Tuning
Rear Suspension Front Suspension The Frame Transmissions Engine Tuning Miscellaneous
Tuning is one of those subjects that is in the eye of the beholder and can be considered to be an extremely simple subject, or an extremely complex one. It depends upon the experience of the tuner and the depth to which he wishes to pursue the subject.
Being old school and having spent considerable time at the track playing with various types and brands of cars for far too many years, I prefer to take a broad based approach seeking synergy from the parts. I am going to try to stick to the basics rather than delving too deep into the theory. There are so many ways to approach the various systems that I shall hopefully leave you with an understanding and you can fill in the blanks in the way most suitable to you.
Try to learn the difference between theory, empirical results, opinions, and magazine articles. What follows is my opinion based upon my own experience and that of others. I will try to be somewhat general in nature as I understand there is usually more than one way to approach a problem. There is no substitute for experience as long as one is willing to do some testing to ascertain what works best for ones specific combination. Don't fall for magic numbers or magic parts.
Don't try to compare your car against another car with a different combination running on a different day on a different track with different weather conditions at a different altitude, etc. It will drive you crazy and mean virtually nothing. Takes a lot of analysis to normalize cars under such conditions. If you are that good, you should be betting on horses down at the horse track.
Don't assume that your car will run tens just because you bought ten second parts...whatever that may be.
First, our cars are 25 years old. All the original stock parts have many cycles on them. There is no sense blowing a head gasket to prove original fuel injectors can hit the 11's You will have to go through your car from top to bottom. Keep this in mind when you look at each category below.
People often send me PowerLogger files asking for help in tuning their cars. Far too often, I see problems with the car that are basic in nature. It is impossible to tune a car to run quickly when it has problems that need to be fixed before the car goes to the track.
Before I get to engine tuning, I am going to mention some of the other basic facets of building a quick car.
What does the rear suspension have to do with tuning? It's quite simple. If you cannot transfer power to the pavement, you cannot go quick(ly). With good running cars, the one that spins the most, loses most often.
On an average 11 - 12 sec car, a reduction in the 0-60 ft times of one tenth generally equates to one and a half tenths at the lights. A quicker car may pick up closer to two tenths at the lights. See why obtaining the best "hook" is so important?
Part of getting the best short times is obviously in driving skill. The other half of the equation is setting the car up so that it is easy to drive.
I am not going into detail on suspension theory. An excellent book that covers the subject in great detail, yet, in simple English, is Dave Morgan's "Door Slammers-The Chassis Book". Dave used to write the column on suspension in National Dragster and is now employed by the IHRA. He tours and puts on suspension clinics periodically. Do a search and see if you can find one at a reasonable price as the cost has soared recently. Excellent software that allows one to calculate all needed parameters is "4 Link Calculator" by Performance Trends.
Now, the factory suspension was not designed with drag racing in mind. It was designed for good ride and intended to keep the rear axle more or less located under the car. On cars that sit at factory ride height, the instant center obtained by projecting lines thru the upper and lower control arms and determining the intersection part is often either behind the car, which is terrible for planting the rear tires optimally, or way to the front of the car-again, very bad for weight transfer.
In spite of the bad location, these cars will still hook surprisingly well using the factory control arm locations if the bushings, etc. are in good condition. Short times (0-60ft) of 1.6-1.7 seconds are not at all uncommon for 11-12 second cars. Cars that go even faster routinely have the power to go 1.4-1.5 seconds in the 0-60 ft light.
What does it take? It takes good bushings in the control arms-all four bars, both ends. Although I prefer rubber bushings, I think the polygraphite bushings probably do a better job when it comes to drag racing launches-at least in theory. They are cheaper as well.
Lower Control Arms-Boxing the lower control arms prevents distortion when they are under compression from launch. This is more important when very sticky tires, or, slicks are used. The upper arms are under tension during acceleration and are not likely to suffer dynamic distortion. Box the lowers. They will perform better when you get quicker and will not distort with heavier sway bars installed. If you don't wish to box your own...there are plenty of options out there. Basically, they are all the same no matter the hype.
Do you need adjustable upper arms? That really depends upon how fast your car is. If it runs in the tens, adjustable upper arms allow you to add some negative pinion angle which may help transfer power a bit better on a hard launch and aid in avoiding some driveline bind. One can obtain the same effect by buying a set of lower control arms from Paul Ferry of HRpartsNStuff that are 0.5" longer and which will normally provide a couple of degrees of negative pinion angle which is fine for a street car. Cars that run in the tens, or better, may benefit from 4-6 degs of negative pinion angle, but, this amount will wear the rear U-joint out quickly in a daily driver. I prefer Paul Ferry's adjustable uppers and leave lower stock length. Set angle to 3 deg.
If you have access to four wheel scales, then you can use the adjustable upper arms to dial some preload into the passenger side rear tire by shortening the arm slightly. Read Dave Morgan's book before you start...
Remember, if you install upper control arms with solid bushings in the front, the frame will need to be reinforced, or, you will soon find yourself with elongated mounting holes as the stock frame simply cannot stand the abuse.
Do you need a long pinion snubber? Just say no. Long snubbers were in vogue on leaf spring cars back in the '60s on 7 liter Super Stock cars that tended to wrap the rear axle up in the spring on launch. On a coil spring rear suspension with four link control arms, the rear housing does not rotate much if the bushings are good. Further, they do little for load transfer as they press down on the pinion nose in the center rather than over the passenger side end which tends to lift upon acceleration. Worst case, they load the rear axle and then unload it up in the top end of first gear causing wheel spin and/or a change of direction of the car. Yes, I know, lot's of us old guys tried them initially, but, we were wrong. Save your money.
Do you need air bags? That is a definite Maybe Not. (or a Probably Not)
The primary function of an air bag is to increase loading on the passenger side rear tire to counteract the natural unloading, and resultant tire spinning, that is incurred when torque lifts the rear right side of the axle and removes wait from that tire. Wait, you say, that is why we have posi-traction rear units-they apply power to both tires. Not exactly, they transfer power to the tire that has the most traction...in this case, the driver's side tire.
A secondary function of air bags may be to prevent the body from sitting down and cutting the rear tires if large tires that don't tuck completely into the fender wells are employed.
Either way, the air bags function by increasing the spring rate of the rear coil springs. The more air that is added to the bags, the stiffer the springs become. This is not necessarily desirable as the rear axle becomes increasingly less compliant as the spring rate is stiffened (increased) and may reach a point where excessive tire spin at launch results or the load transfer from launch does not last long enough and the tires break loose shortly after launch.
Now, if we examine the primary function of an air bag installation which is to increase the load on the passenger rear tire, we note that as air bag pressure is increased on this side of the car, the body is jacked up higher into the air which in turn increases the load on this tire at launch (and removes it from the other tire). This makes it harder for the axle to lift up and reduce traction on this tire.
If we are only trying to equalize launch traction, there is no real reason to use two air bags as one on the passenger side will suffice. On a posi equipped vehicle, 10# of pressure in the bag may be sufficient to do the job. On a peg leg car (non-posi) it may take 20-30# to do the job. Hopefully, it should be obvious that the more powerful the engine, the more the torque roll will be and the more the bag will need to be inflated.
How do we determine a starting pressure for the air bag? There are two simple methods.
Do a burn out....the two strips of rubber left on the pavement should be the same length. Add air to the passenger side bag until the two strips are equal.
The second method entails loading the car to the normal launch boost against the brakes and adjusting the air in the bag(s) until the rear bumper is parallel to the ground at launch boost. Note that this technique does not work on tranny braked cars and is hard on the tranny due to rapid heat build up so the boost should not be held more than a few seconds. The first may not seem to be as precise, but, I suspect it is the only viable means as it accounts for the dynamics of launch as well as static conditions.
Let's retrace our steps a bit and consider a few things.
The more power the car makes, the more it will tend to unload the rear passenger side tire. Hence more air will be required.
Increasing the effective spring rate will improve the traction at launch by making both tires do equal work, but, it may affect handling at high speed as the body is torqued due to bag pressure and imperfections in the strip can be magnified.
Increased spring rate may not be desirable for maintaining traction throughout the run as the increased rate resists load transfer and the tires may unload prematurely causing wheel spin up in the top of first gear or into second. Typically, softer spring rates help cushion the blow delivered at launch by stick shift cars or by tranny braked automatics that leave violently. Stiffer spring rates may benefit automatics that leave on the foot brakes, but, note that the stock springs may be considered stiff as they are.
Considering the above, it would be desirable to minimize the amount of air used in air bags, or, to eliminate them altogether.
Airbags are ok for the street to keep the body from hitting the tires on turns or potholes. I always suggest emptying them on a car that has good springs, shocks and sway bar.
My guess is that most people with cars that have suspensions that are in good condition will find very little benefit in air bags.
Aren't sway bars only good for going around corners? Absolutely NOT! Sway bars are more properly called anti-roll bars as they assist the body in maintaining a level attitude in relation to the road. The effort to do so also resists the effort of the rear axle to lift the passenger side rear tire off the ground and into the wheel well which allows tire spin. The factory supplied rear sway bar is undersized even for good handling as it allows too much understeer, and, it is definitely undersized for drag racing purposes. When using the factory rear bar, air bags definitely provide some traction benefits at the track. That is why I stated that air bag need is a definite maybe in the prior section.
If the factory bar is replaced with a substantially larger bar such as the ATR bar which is a massive 1.375" in diameter as compared to the factory unit which is a little less than 1.0" in diameter, there is a large increase in the resistance provided to the rear axle as it tries to twist under launch torque. In this case, an air bag may not be required, or, it may need far less air to equalize "bite" from both tires.
For informational purposes, it is worth noting that there is an alternative to the factory style mounted rear bar style. The Wolfe Racing bar works very well for very serious cars and should reduce the handling problems that are often inherent with very quick cars. It is both expensive and a pain to install as it requires welding and may interfere with the exhaust system. It may also cause bind during cornering on street cars. The HRPartsNStuff bar is similar in design concept but is a bolt in solution made precisely for our cars, and, it should not bind. One of these days, I intend to install one on my GN in place of the ATR bar. Look at the links for the difference in concept and additional theory. I suspect that cars running in the nines, or faster, will show more benefit from a performance versus cost stance than most of us will see with our cars.
Note! Recently, I have seen some cars running the Hellwig rear bar which is tubular and adjustable. It resembles the HRParts bar but is under $200. this might be the most cost effective means of having something that works on the street for good handling, and, on the strip for great launches.
Bottom line-the rear sway bar is a major contributor in obtaining maximum traction and the stiffer it is, the less air bags, and their possibly negative effects, are needed.
Note. Wolfe bars are not really streetable in my opinion!
Rear Shocks-How important are they? Well, you need at least two of them. That is not as facetious as it might sound. Shocks, at least on cars that are slower than 11.0 are not particularly critical. I would say that a pair of worn out stock shocks would do very well while a set of good, stiff shocks such as Bilsteins would not be very good from a technical view. If you want to have something that will work well and be a good conversation piece, put a pair of QA1adjustables on the back and set them to soft for the track and up in the mid range for normal driving. Don't know if you will see any difference, but, it looks cool to crawl under there and turn the knob! If you have a hard leaving car running down in the tens, a set of specialty drag shocks would be good for the strip, but, not very suitable for a daily driver. Whatever shocks you have on the rear now should work well unless they are rusted solid and don't let the rear end sit down under acceleration.
Rear Springs-Do you need special drag racing springs to get a good launch? Again, I think this is one of those non-critical items. The factory springs should work well at least into the nines. Considering that most of us are using our cars on the street to some extent, I think the springs that are sold by Moroso and others as specialty drag springs are really not worth the effort. All out racers launching at very high boost off a tranny brake might see a slight benefit of such combined with a set of rear drag shocks, but, I don't think it would be a major improvement, or even a significant one for most of us.
Note, stock Moog replacement springs have gone 1.3s so there is little, if any, bang for the buck with this type of spring replacement (special drag springs such as the Morosos) and they may make the car unsafe in normal driving.
Tires-What to use? In recent years, drag radials have been the trick to use for daily drivers that see week end action. The BFG DRs were the first on the scene, but, they are a little more soft and have less tread than than the Nittos so they may not last more than 3000 miles and they can be exceedingly dangerous in the slightest rain. The Nittos came out next and they are a bit harder and offer considerably better performance in the wet due to the tread design. They seem to last closer to 10,000 miles for the average driver. The latest, hottest tire is the Mickey Thompson drag radial which has a softer, stickier rubber and seems to be giving better short times than the competitors. Being softer, they may not last that long for those that want to do burn outs after each stop, but, they may be the trick for those that are serious about it, or, are making more power where the other drag radials just want to spin.
M/T does not suggest them for anything other than dry pavement. They appear perfect for a week end warrior on those nice, dry days.
The factory tire diameter was 26" which is only slightly taller than the average 275/50-15 tire. A number of cars that are running 115 mph, or faster, seem to often prefer a taller tire in the 27'-28" class. A 275/60-15 is normally 28" in diameter. There are some cars which don't appear to like the extra height and I suspect it is all combination driven.
Most Drag Radials seem to like about 18 lbs of air. It's a good starting place to find out what works best for you. Remember that track surface, prep, temperature, and the boost you leave at will all affect pressure. Don't use less than needed, if for no other reason than safety.
When doing burnouts...do the minimum required to make the tires sticky...usually staying in the water until the smoke changes from white to a slight bluish tint, and no longer, is about right, I think. This brings the sticky to the surface without frying the tire.
Let's not forget that chassis setup, engine power, track condition, road condition and environment has as must to do with traction as the tire brand.
Rear Suspension Summary- If you are running 11.0's, or slower, I suspect that you will get about 85% of the possible improvement from a pair of boxed lower arms, good bushings in both uppers and lowers, a large sway bar, stock springs, stock, or similar, shocks and a sticky set of tires. This can be done relatively cheaply and should provide adequate consistency for bracket racing.
If you want to address the other 15%, then adjustable uppers, relocated control arm mounting positions, a Wolfe/HRPartsNStuff style rear bar, and drag shocks can all help if you take the time to get everything dialed in correctly. This means repeated testing with slight adjustments between runs. There ain't no right way beyond what your car tells you it likes...no short cuts!
An air bag on the passenger side may help the final tweak as well. Just remember that an air bag increases effective spring rates and that is probably not desirable so keep the pressure as low as possible to get an even burnout from both tires. Two bags may be used if it helps eliminate tire rub, but, wheels with the right backspacing would be preferable.
Driveshaft loop-Yes you need one unless you have a death wish or just want to destroy your car. Buy one, Install one!
Also, most tracks require it.
Front end-What's it got to do with going quick? The answer is "plenty"! In order to get the best short times and the highest top speeds, the car has to transfer weight from the front end where about 58% of the weight resides to the rear tires at launch to provide maximum "hook" and then it has to allow the car to run straight all the way down the track with minimum rolling resistance.
Front Sway bar-should I remove it? At the track, definitely. But, remember that this can make the car unstable if the steering wheel is suddenly moved, PARTICULARLY if you don't have the suggested large rear sway bar on the car. If you do have the larger rear bar and larger rear tires, then, the car should handle fairly well and can be driven to and from the track with the bar removed. I don't suggest auto-crossing on freeway ramps, though. Remember that many things we do to improve drag racing performance may actually harm normal driving performance. Be smart and be safe!
Removing the front bar will allow the front end to rise and add down force to the rear tires which is what we want. If you are serious about improving short times, this is a "must" change.
Removing the front bar will also be a weight saving gain in a area that helps with lift and load transfer.
Front Shocks-Do I need special shocks? That depends upon how serious you want to be. Stiff shocks like Bilsteins resist the front end lift and limit the weight shifted to the rear tires. Specialty drag shocks like the 90/10s, or the 80/20s allow the front end to rise without much resistance so that mass is easily transferred to the rear tires, but considerable resistance is encountered when the front begins to settle. This maintains the weight transfer as long as possible and may prevent the tires from beginning to spin after leaving the line. These shocks are excellent for a race car but can make for a dangerous handling car on the street.
Some shocks, such as those made by Competition Engineering can be adjusted from 90/10 to 80/20 to 60/40. The latter is more streetable, but, these shocks typically have to be removed and the rod turned to change the damping.
Other shocks, such as the QA1s have a knob on them to change from stiff to soft, but, I understand that this does not change the ratio of the shock. This means the front will come up easily, and also go down easily. Better than a set of Bilsteins, but, not as good as a true drag shock.
Plenty have run in the upper tens with good shocks like Bilsteins....they may not be made for drag racing, but, I like them because I like my car to handle well on the street.
Do some searching on the Net. There are quite a few articles on shocks and how to use them. Better information than I can parrot, I am sure.
Front Springs-Do I need special drag springs? I would not unless building a true race car. After all, these cars should be fun to drive around corners as well as down the track. The factory springs are not too stiff and work well with the aforementioned shocks. If you have Eibachs, or similar, as I do, then you really need a good set of shocks that do not add resistance to the front end lift. Stock springs are not a major deterrent until one is far into the nines, I suspect.
Alignment-Is there anything to consider here? I would put plenty of positive castor in the front to encourage the car to run straight. Always get a thrust alignment which references the front wheels to the rear wheels for minimum rolling resistance. For a drag racing alignment, have the shop check the toe with the front end up in the air simulating a launch and adjust to reduce "scrub" in order to minimize rolling resistance. Check the toe with the front down close to the static position, and, find a happy medium that does not interfere with normal driving. Toe on each side will probably be close to 1/32". Camber should be close to "zero".
Front Tires-Should I get a set of skinny front runners? Yes, if it is a pure drag car. If you are going to drive them on the street, then consider the load ratings of the tires. The average Regal has at least 1100 lbs on each front tire in a static position, and, this goes up considerably when the brakes are stomped. Those skinny front tires may look cool to the teenaged vampires hanging around Sonic, but, they might kill you in the wrong usage. Think about what it takes to be safe as well as what looks good to you, or whomever you are trying to impress.
When at the track, air them up to minimize rolling resistance.
Typical drag racer tricks-how serious should I get? That is really up to you. If you want to take the tension off the control arm bushings, or use Del-alums. etc., then go for it. Just don't forget this is for the track. Tighten them back up before you go home. If you want to use lightweight grease, loosen the wheel bearings, etc., again remember this is no good on the street.
The Frame??? What the heck are you talking about?! Yep, the frame! Everything is bolted to the frame, and, it is extremely flimsy/flexible when abuse is applied. Crawl under the car and examine it. You will see that the frame is not completely boxed, but, is a C section in several areas and is also made of quite thin material. If you remove the rear body bushings, you will see the frame rails sag downward. Not very impressive in my eyes.
When the car is launched, the frame twists and becomes part of the steering system. This does not lead to consistency. The stronger the car leaves, the worse the problem.
Okay, what can we do to improve this situation?
1) Replace the body bushings at all positions, top and bottom, plus add the GNX bushings. Doing so will incorporate the body as a strengthening member to the frame. If you want maximum effect, there are poly bushings available. Be warned that they may add some road noise into the car according to some.
2) Add the triangle bracing to the front frame and install the cross bracing in the trunk. The former stiffen the front half of the frame while the latter removes a lot of twist from the body which in turn, hold the frame in position.
3) If the car is 11.50 or quicker, install a roll bar. In addition to protecting you if you hit the rail, or roll it, at 120 mph, it ties the frame together which will make the car launch much straighter which may not only keep you from crossing the center line and killing the guy in the next lane, but, when the car goes straight, it gets to the other end quicker.
4) You can also box the rails in the open areas to add some strength. Worried about the additional weight? hey, didn't you take the front sway bar off?
All in all, the frame is the foundation off which you work. It determines the success of everything that you do to improve the drag "racibility" of your car.
Rebuilt transmissions-Do I need to spend $2000.00 or more for a killer transmission? If you are quicker than 11.5, or run slicks and like to do banzai, high boost, launches, yeah, you probably do. If you don't fit this category, then something around half of that figure will probably meet your needs.
If you are paying to have it rebuilt make sure the shop is familiar with the HI-Per rebuilds that our Buicks require. Stay away from shops that cannot supply a number of references.
When you decide it is time to rebuild your tranny, it's a good idea to replace the converter or have it opened and cleaned out as it is probably full of trash and may be tired. No since having it pumping trash back through your new tranny or failing and filling it with bits of metal. If you have a newer unit, have it cut open and cleaned out. This is particularly critical if your old tranny has given up the ghost.
Replace the stock transmission cooler. It will also be full of debris.
A well built tranny with a good converter and a good tranny cooler should perform the same each run of the day whether it is cold or hot. It should not flare on shifts and it should not slip more on the top end from one run to the next.
How hard the tranny shifts is not necessarily an indicator as to the quality of how well the tranny is built. It may impress your friends, but, all it may be doing is increasing the rate of wear on the drive train parts. One wants minimum slippage (flare) on the shifts, but brutal shifts may be do more harm than good.
When analyzing run differences, it is important to compare your data logs and see if the mph is consistent with rpm from run to run. It's a waste of time trying to tune for problems that don't exist in the engine when the problem lies in the tranny. Be sure you compare the rpm at the shifts as well as the rpm during the non shift periods of the run.
Converters-What should I buy? Torque converters are kinda like religion; there is an option for everyone.
The stock converter was stamped D5 and was a 12" converter that stalled around 2200-2400 rpm at 6#, or so, boost (factory turbo). Factory replacement converters are generally lower stall and don't allow the car to build boost.
The factory converter is a lock up unit meaning that there is friction material inside that effectively locks up in third or fourth gears upon command from the ECM and removes the slip inherent in a converter. This serves to improve fuel mileage and reduce rpm at cruise.
The 12" converters can be restalled to 2600-2800 rpm by bending the blades to a lesser angle inside the converter bent over to parallel the rotation-is this lesser or greater?). This allows the converter to spin to a higher rpm before the car begins to move. 2800 rpm seems to be considered to be the maximum that a 12" converter should be restalled to before the fin angle becomes such that there is excessive slip all the way thru the rpm band which tends to create too much heat and too much slip at high speed. Some do sell 12" converters rated to 3000 rpm and depend upon the lock up clutch to handle the slip on the top end. I don't like these converters as one is asking them to defy the laws of physics and the clutch life is shortened further by locking them up on the strip.
From the factory, the converters do not lock up at wide open throttle. This is done in the interest of long converter life. We often mod them by installing a lock up switch, or commanding lock up in the chip, so that we have lock up at wide open throttle. As we increase the power of the engine, we quickly begin to eat up the clutch in the converter. I particularly don't like the ECM commanded lock up in daily drivers. No need to add further abuse on a regular basis to the converter. I prefer a lock up manual switch. Then I can decide when to get serious about the abuse.
Back to converter diameter. When one needs greater stall than 2800 rpm, then one really needs a smaller diameter converter-9", 9.5", or 10" are the common diameters. The smaller diameter converters obtain higher stalls and better torque multiplication without having to bend the blades as much and this works better on the top end. The downside to the smaller diameter is greater heat generation and too little clutch area to allow for reliable lock up on a strong engine.
The aftermarket has addressed this problem in various ways, but, the most common method is to reduce the converter diameter and go to higher quality components inside.
For a street driven car, the lock up converters as described above can be very practical. Better gas mileage and less heat generation which can shorten the tranny life.
The alternative for more strip oriented cars is the non-lockup converter which is similar to what older cars traditionally used. They are much lighter in weight which reduces rotating mass and they often offer better torque multiplication, not too mention that they are much simpler and reliable. The downside is slippage throughout the run which may hurt the mph on the top end and they can generate a lot of heat with the continual slippage in normal driving. All cars should have an external cooler for added tranny longevity, but, the non-lockup units should be equipped with the largest possible.
Non-lockup converters require a minor pump mod when being installed.
There always has been an ongoing dispute over which is best, lockup, or non-lockup. I think I prefer non-lockup on cars faster than the lower 11s or strip only cars. This is opinion based upon a number of years of observation rather than any hard proof.
Stall-how much should I use? Sometimes I think stall is in the eye of the beholder just like tuning. First, it is hard to define stall in a turbo car as the turbo itself is such a power modifier that a converter that stalls to X on one car, may far exceed that number on another car. The turbo characteristics also have a lot to do with it. Matching turbo to converter is one of the more important items on the list when putting a combo together.
The idea when selecting stall is to be able to quickly obtain enough rpm so that the turbo can then make enough boost at launch to immediately spool to full boost on within a few feet of the starting line. For street driven cars, one should not have to stand on the brake and gas for several seconds to get to this point...takes the fun out of street fun.
Typically, the factory D5 works well with stock thru TA49/TE44's. More stall should not be needed if the fueling is correct on the car so that the turbo spools correctly. So often, people are unhappy because they don't think they can burn the tires off on launch and they go to a higher stall. Then they find out that while they are spinning their tires, the other guy is driving away from them.
It should be noted that what blows the tires away on the street may not do much at all on a well prepped strip with a set of slicks on the rear.
Therefore, we always have to consider some compromise and learn to drive the car in all conditions...this may mean less that wide open throttle at launch on the street if the car is equipped with a converter aimed at high boost launches on slicks at the strip.
When foot braking a converter, the quality of the rear brakes, the tires, and the pavement condition has a lot to do with it. Typically, I find that a converter that will quickly allow 5# of boost on street tires will allow twice that on slicks on a sticky strip.
Recommending stall is a tricky business as ultimate stall depends both on the manufacture of the unit and the hp in the stall range being generated by the car. When a car fails to achieve the stall rating of the converter, one has to figure out if the car is at fault, or is the problem with the converter.
So Why did I take so long to get to the important stuff? It's very simple, if your car will not perform consistently from run to run, it makes it much harder to analyze what the engine is doing. Eliminate the variables in order to understand the constants. Anyway, drag racing is about getting to the lights first, and the easiest tenths are off the starting line as I initially pointed out.
The Cardinal Rule- Do your best to never change more than one thing before you go out and try to determine how effective that change was. If you change a number of things, it becomes extremely difficult to determine what caused the change whether it be positive, or negative.
Required equipment
1. Intellectual equipment-A basic understanding of how things work. You have to understand what the parameters reported by your scan tool mean and what is normal, and what is not. For instance, you have to understand when the maf readings are normal, and when they are not. Otherwise, you will not be able to understand if the O2 readings are lean or rich due to engine demands, or because the maf is not working properly.
It takes awhile to learn how all the ecm control functions work together and affect one another. Read the Basics section and the Scan tool section and try to learn the vocabulary so you will understand what people are talking about...and maybe have a better clue if they know what they are talking about.
Also, it's not just simple technical things as pointed out above, but how changes in weather, etc. affect hp output. For example, a change of 20 degs in air temp can effect a change in hp output in the magnitude of 15-20 hp. This means that such things have to be considered when evaluating tuning changes, and, if at the track, should affect the tuning changes you make to counteract the weather change.
2. Required test equipment-a recording (logging) scan tool (the only one that really fits the bill is PowerLogger (available from Full Throttle Speed or Turbotweak) as others don't provide enough samples to be meaningful on a quick car), a fuel pressure gauge on a long hose that can be monitored while making a run, an audible knock (detonation) alarm, and an analog boost gauge (or an accurate digital model). An A/F monitor that uses a wideband Oxygen sensor for input can be useful-only if the user does not believe in magic numbers and will do the testing required to determine at what A/F his particular car runs the best.
Note that experienced guys have been getting along with
a simple Scanmaster for years rather than using something like PowerLogger.
PowerLogger makes it really easy to get help and other opinions as well as
provide you with a blow by blow playback of the run. If you use it, it
should speed up the learning process as being able to see all the parameters at
the same time and observe the interaction between them should speed up the
learning process considerably. I strongly suggest you invest in both a Scanmaster and a PowerLogger as they compliment each other.
Now let's consider these items in a bit more detail.
A. Recording Scan Tool-We need to derive two basic uses from the scan tool. First, we want to be able to monitor various parameters in order to look for potential anomalies and/or problems so that we know the engine is running properly from an engine management view.
Secondly, and just as important, if not more important, is the need for the data logging that PowerLogger provides. Unlike a conventional ALDL scan tool that records data approximately each 1.4 seconds, PL records up to 25 data sets per second. It allows us to examine all the various parameters in order to see what looked right, what looked wrong, and what might be tweaked to be better at our leisure and not simply during the actual run.
It is also useful if one is to evaluate one run against the next whether one is comparing rpm change during shifts, or searching for voltage aberrations, duty cycle, etc.
B. A fuel pressure gauge that can be mounted under a wiper blade on the windshield where it can be read during a run is required to insure that the pump is supplying sufficient fuel during a run. It is not needed for each and every run, but only periodically to verify that things are okay in the pump department when problems arise. I prefer to use a large diameter, high accuracy unit from Grainger or McMaster-Carr. PowerLogger also allows one to attach a pressure sensor to the fuel rail and record fuel pressure data along with the other recorded data. The better senders are pretty consistent and accurate. Then we can see on every run how well the fuel delivery was maintained rather than having to physically observe the analog gauge. The fact that you just installed a new fuel pump does not necessarily mean you have the correct pressure at the fuel rail at all times.
C. An audible knock alarm with a loud alert as well as visual warnings is a necessity to save you from potential disaster. No matter what your tuning theories may be, detonation will kill an engine in a matter of moments under high boost conditions. If the alarm goes off, Lift! Sometimes this is hard to do in the heat of battle but discretion is the cheapest course of action.
D. An accurate analog boost gauge, or a high quality digital gauge, is required. The digital gauges that have a logging function can be very helpful in tracking boost and ensuring that it comes up rapidly and stays where it should be. Depending upon your particular combination, a pound of boost increment may be worth a tenth of a second in the quarter. Being able to monitor it accurately is a big help in fine tuning. Again, you can record boost data on the PowerLogger. It should be obvious that you need to verify that boost is being properly controlled throughout the run.
E. Wide band Oxygen sensors that display Air/Fuel ratios can help dial in a combination as long as one does not believe in magic numbers. If someone tells you that he set his A/F to something like 10.6-1 in order to be safe, ask him what he did to determine what was dangerous? Because of the tendency of people to try to come up with so called magic numbers rather than do actual testing in order to determine what it takes to maximize performance, I hesitate to recommend such things for new comers.
Note that I have removed references to EGT. It can be confusing as EGT's increase either side of stochiometric air fuel ratios. I think avoiding detonation is good enough. If it is not detonating, it is not too hot.
Tuning-What can I change to make my car run up to its potential?
There are really only three things that you can do to alter the tune of the engine assuming you have addressed all the basics.
1. Change the fueling. (Match it to the boost-or vice versa)
2. Change the timing.
3. Change the boost.
If you want the simplest possible answer, run as much boost as you can with as much timing as possible with the leanest air fuel ratio possible without incurring detonation. Note that damaging detonation can occur without you ever hearing it and that is why we must monitor timing retard as the computer has better ears than most of us do.
Before you start changing things, get a spiral notebook, or a logbook made for such things and write down the particulars of each run-temperature, barometric pressure, humidity, wind direction, wind speed, track condition, etc. as well as the performance details. It's nice to be at a track that gives you info on several waypoints down the track so you can break the run up into segments for analysis. If tuning for the street, write down the particulars and what you have done...also, put some comments in PowerLogger so that the people trying to help you can understand the differences.
If at the track, make a few runs to dial in your launch technique in order to determine how much boost you can leave at without spinning the tires and how much air pressure is optimum. At the beginning, this may take a few tries until you get it figured out. Then it should be a lot easier and quicker.
Finally make two or three runs to obtain some baseline numbers to see if you are running consistently as it is impossible to make decisions on fueling and/or timing parameters if the car does not repeat itself under similar conditions. Remember that changes in air temperature, barometric pressure, humidity, etc. will affect your performance so try to do your tuning when there is not a lot of change going on.
There should not be any timing retard ...but, if there is, LIFT! Reduce the boost and try again.
Miles per hour is a better indicator of horsepower than is time as time is affected by launch and track conditions more than miles per hour at the line. At the beginning, concentrate on improving the mph in the lights and then go back and analyze the waypoint information and see if you can tweak the fueling/timing to improve the waypoint numbers-if at the track, of course.
My Own Basic Assumptions
1. I can run less fuel in first and second than I can in third and fourth.
2. I can run more timing in first and second than I can in third and fourth.
3. I can run more timing with small turbos than I can with a large turbo.
4. Race gas is for real race cars. Alky injection is for anything driven regularly on the street.
5. Boost makes more power than small changes of timing-particularly on the street
6. Due to the lack of change in ambient conditions, I can run closer to the edge consistently at the track than I can on the street so I leave more margin for error on the street.
7. Any amount of timing retard resulting from real detonation will do some damage to your engine and will eventually cost you.
Okay, I wrote the following to someone that was asking if I would explain how I would approach tuning his car. He has a TurboTweak 5.7 chip. I am not trying to imply that you need a TT chip as opposed to a Bob Bailey chip as I think they both will give exactly the same performance in the hands of someone that can read and understand the instructions and who also understands the goals of tuning.
Now, on your TT chip, you have four
parameters that you can adjust.
Parameter 1 controls wide open fueling in all four gears.
Parameter 2 controls wide open fueling in FIRST gear and it is a trim factor
based off Parameter 1. In other words you first set Parameter 1, then you look
at your low gear fueling. If you want to lean it down some to improve turbo
spool and get a quicker launch from a standing start, you can. If you have too
much wheel spin from too much turbo spool, you could make it richer and cool
down the charge a bit to slow down the spool a bit. It really depends on how
good the traction is and how much boost you are trying to leave on.
Parameter 3 is the timing in first and second. Normally you can run more timing
in first and second at the strip if you can hook the tires because there is less
load on the engine and combustion chamber temps are not as high. This can
be a bit more dangerous on the street when the engine is hot because excess
timing might cause detonation in that case where it may not on the strip because
the engine is cooler.
Parameter 4 is timing for 3rd gear and 4 gear. Again on the strip you can
usually get by with additional timing unless you are hot lapping the car and the
engine is not cooled down between runs.
As a rule, I am much more conservative on the street because engine conditions
are usually not optimum-particularly if you have been driving in traffic or
pounding on the car at boost multiple times.
Okay, so that is what you can do with your chip. If you had the SD chip you
could adjust over 20 different things but there are only a few that I ever touch
and seldom at that once I have things where I want them.
So what about fuel pressure? It's something that can be adjusted. When
you adjust fuel pressure you adjust every facet of fueling from idle to wide
open throttle. A change in fuel pressure affects flow by taking the square root
of the (new fuel pressure divided by the old fuel pressure). Therefore a change
in fuel pressure is a relative small change in the actual delivery but it is
more obvious at idle and low rpm than it is at higher rpms because the
percentage of change compared to the fueling is larger due to the small amount
of fuel used at idle and low rpm.
This is what I do, I set the fueling to 43 (TT chips) and I drive the car until
it is fully warmed up and I have done some stop and go driving, then I stop and
look at the O2s in gear idling. If they are 780-800 and the car is idling well,
I call it good and forget it. Note that the O2s will change when you stop and
the O2 sensor starts cooling down so your 780 might increase to 810 in a short
period of time. Don't be confused because this is a function of the stock o2
sensor not a change in fueling.
If, when I first stop, the o2s read something like 820, then I reduce the fuel
pressure 1-2 psi and try it again, until my first readings upon stopping are in
that 780-800 range. Remember that the TT chips are open loop at idle so that
first blm cell is not adjusting the fueling like the factory chip. It does have
some learning capability, however, so that is what I like to drive the car for a
bit before beginning to play with the adjustments.
If everything is right, the O2s should be pretty stable wherever you set them
and they should not be jumping around at idle due to the open loop feature.
That is why the idle is normally smoother and better.
When you come off idle, then the chip goes to closed loop and the o2s will jump
around a lot more as the ecm takes charge.
In essence, you can use the fuel pressure to set up your idle and low speed blms
but I only look at the idle O2s first when I stop and the sensor is good and
hot.
Now, remember that the fuel pressure affects the entire fueling range so the wot
fueling will be a little leaner than what Eric put into his default if you
reduced fuel pressure at idle with the HOSE OFF so you need to look at the wot
fueling to see if it needs adjusting. Normally, it will probably not be
noticeable because the chip was probably a bit rich to begin with for safety's
sake. Be sure to put the hose back on the regulator
before you drive it again!
Now, having done this, I go to the wide open throttle setting and start dialing it in. This needs to be done at the top of third gear so it will approximate what you will see at the finish line. At this point, I am leaving the timing alone (using the default in the chip) and have the boost set for whatever Eric said the chip was burned for.
If the chip was burned for 25 psi, I would not be surprised to find that the chip was giving plenty of fuel for that boost level and no timing retard was being shown on Powerlogger. If I am leaving the boost at 25 which is generally a good level for the street when using alky, I start removing a bit of fuel-say no more than two numbers at a time and making a run after each adjustment until I see the slightest hint of timing retard. I then add about 3% of fuel back to the wot throttle setting and call it good. I prefer to hae some margin of error-particularly on a street car where ambient conditions can vary widely. This is done with Position 1 in the chip.
Spraying Methanol at 100%, I would expect my oem O2s to be around 780 on the street. When at the track, I might lower my fueling a bit and look for something around 750-760 mv but in all cases, I am not going to accept any timing retard on PowerLogger.
Once I am happy with third gear fueling at the top end, I would look at the O2s in first and second from a launch. Again I want to remove fuel until I am on the verge of timing retard and then add 2-3% back for some margin of safety. I would guess the O2s will be close to 750 mv but the main thing is NO TIMING RETARD.
If you push first and second too much, you will create a lot of heat in the combustion chamber and this may push third gear over the hill so be careful and don't cause detonation in third by going too far in first and second. Tuning is a tedious business and there are no short cuts nor magic numbers.. It is all about what works on your car with its combination and the ambient conditions around it on a given day. That is the reason I like to leave room for a margin of safety. I like living to fight another day instead of fixing what broke because I was too aggressive.
Okay, I have not mentioned timing. I think most of Eric's chips have defaults of 23 degs in first and second and 21 in third and fourth. That seems to work well on the street in most conditions. At the strip you may get by with adding a couple of degrees more, but, you have to be careful and not make big changes at any one time. Adding timing in first and second can greatly affect the spool up and the launch. If you can stick the tires, it can get you out of the hole quicker...or it can make you break traction. In third gear, I have not seen as much difference and I have seen some awfully quick cars that never used anything but the defaults.
I am not going to mention programming the alky controller other than strongly suggest you start with it set as the manufacturer suggests and read all his notes on tuning the alky flow. Talk to him about changes.
One thing I have seen a few times in recent years was guys that kept adding alky to stay out of detonation. When I questioned if the fuel pressure was good, they assured me that there was nothing wrong with the fuel pump because their O2s and A/F's were dead on so it would be a waste of time and money to buy a fuel pressure gauge. Bad things happen to those that think like this. In each case, they were increasingly running on alky as the fuel pump was dying. You cannot assume anything is good without being able to prove it.
Finally, accept the fact that the quicker you
go, the faster something will break. The corollary to this is, the faster
you go, the more expensive it will be to fix it when it does break. Stuff
happens and none of us are exempt. It's just that it happens a lot faster
to idiots who ignore the warning signals.
Mechanical Condition-Yes, I know I am being redundant as I stick this in every section, BUT, if your car is not in proper working condition, you are wasting your time.
If the turbo is blowing oil, the valves are burnt, the tranny is slipping, or flaring between second and third, a cylinder lacks compression, a head gasket is blown, the car detonates under boost, the cam has a flat lobe, and/or the timing chain is wasted, ad nauseam, stay away from the track...fix the damn car! Otherwise, you have nothing that can be made to perform properly and you are just inviting more expensive repair bills if you try.
Engine Cooling
An old adage states that one-third of the combustion heat goes into making power, one-third goes out the tail pipe, and one-third goes into the cooling system. Turbo cars try to make use of the heat going out the exhaust to spin the turbo when required.
The one-third that goes into the cooling system heats the oil and the coolant in the block. We need some heat in both to make the oil work properly and to minimize wear as well as enhance engine efficiency.
Most engineers seem to think that oil should be at least 180 degs in order to burn off condensation and allow the additives to properly clean. On the other hand, oil temperatures that rise much above 200 degs begin to contribute to thermal breakdown which shortens the life of the oil and its effectiveness as a lubricant. How high is safe? I would guess that the curve steepens greatly at 215-220 degs when it comes to oil life. Okay, we can change the oil more frequently, right? Yes, but.....
The but is that hot oil splashing on the bottoms of the pistons, etc. contributes to detonation. We do not want 250 deg oil heating up the piston surface and pushing our engine closer to the detonation limit that what it was when we tuned for maximum safe performance on a colder engine.
The factory oil cooler is often discarded after an engine rebuild and not replaced with an alternate cooler. Many seem to think that the only purpose of the cooler is to prevent coking in the turbo bearings after the engine is turned off by reducing oil temps. While this has some merit, the factory was also concerned about detonation and realized the need to make the engines as consistent as possible.
If you are not running an oil cooler, go buy the largest one you can find. I like the B&M style for durability. The new ones with the fan are expensive but can be more easily mounted without so much regard for external air flow. Keeping the oil in the 180-200 deg range will not only help preserve the engine life, but, will make the car easier to tune and improve consistency of performance.
The other half of the cooling system involves the circulation of normally water/antifreeze based coolant thru the water passages and radiator. This circulation is designed to cool the cylinder walls and heads primarily. From the factory, most came with 180 deg thermostats which was the factory compromise between engine life, efficiency, and detonation control. Most of us have installed 160 deg units which gives us more insurance against detonation, but, probably gives us a bit worse emissions, and may be slightly shorten engine life. The few comments that I have seen attributed to factory engineers would seem to suggest that life is not seriously shortened, but, few would suggest going any colder. Anyone that has run a set of loosely fit forged pistons and heard the "slap" on a cold start up understands the importance of running a thermostat and getting the engine up to 160 degs in a hurry....Slap does not do the ring life any good nor the ring grooves on the piston. The rocking of the piston wears the rings and hurts seal.
Those running original radiators are probably not obtaining nearly as much radiator efficiency as originally provided. Between the tubes being clogged from coolant precipitates and mineral deposits plus the deterioration of the fin bond to the tubes, the core simply does not perform like it once did.
Now the car may not run too hot down the road in normal driving, but, add some wide open throttle runs through the quarter mile, and, the temperature probably rises more than it should.
In most cases a new, heavy duty, three row core will improve even upon the original core and certainly a big improvement over the original core 18 years later. Stay away from four row or five row units as the small tubes and additional thickness work against cooling. By the time air gets to the rear rows, it is already hot and little cooling is performed by them. Also, these cores also block air flow and that further hurts the cooling, particularly when sitting still.
For consistency in tuning and performance, I would use a modern core, a heavy duty water pump such as the Flow Kooler, and an overdrive pulley to increase water flow further along with the standard 160 deg thermostat with a 3/32" hole drilled thru it to aid in getting all the air out of the system. Dual fans will help if you are running a front mount intercooler.
Running distilled water and RMI-25 will provide the best summer time cooling efficiency and will minimize any bearing damage if you blow a head gasket. Just remember that minimizing bearing damage does not make it okay to drive a car with water in the oil. It takes a very small amount of water to destroy the lubrication properties of oil. In the winter, continue to use antifreeze, but, keep adding the RMI-25 as it prevents the antifreeze from leaving silicate precipitates behind in the engine and radiator. Don't use cheap coolant-use Prestone and stay far away from the Dex-Cool orange stuff no matter what your neighbor tells you. For every person that likes it, there are five people that have bad experiences with it. And, anyway, you are going to dump it come spring and go with distilled water for superior cooling, right? (Note! If you live in an area up north where it can freeze at anytime in the summer, don't take the risk! Run Antifreeze year round. You should not need the extra cooling performance anyway) Remember that RMI-25 must be used for the lubricant package as well as its enhanced cooling/cleaning performance. The Water Wetter that many use does not prevent rust very long in a daily driver. RMI-25 can be bought cheaply in quart containers which is good for four applications.
An engine which has a bad radiator also probably has a coating of crud built up on the internal water passages of the block and heads and this greatly affects the ability to transfer heat to the coolant. If this is a hard coating, there is little that can be done to remove it other than a visit to the hot tank when the engine is rebuilt. Cleaners will remove the slime which helps as does RMI-25.
It is important to try to cool the engine back down between runs so that this becomes another constant in the tuning process. It is easy to add a manual switch to the high speed relay so one can cool down the coolant in the radiator as well as idle the engine and circulate the cooler coolant thru the engine and get the temperature back down.
If you install dual fans, retain the factory wiring and relays. Don't run the risk of either having a manual switch only, or leaving them on all the time. If you want heavier wiring, then use the factory relays to switch relays coming directly from the battery. In my car with dual fans, I use one on the low speed circuit and the other on the high speed circuit.