So you're ready to get serious. Welcome to the club. Recipe B is the best performance : cost ratio I am aware of. As has already been stated, this recipe requires you to take over for the car's computer in certain areas and call your own shots. Because of this fact, here's the important legal speak about this page. Read it.
this recipe involves assuming manual control of some functions formerly controlled by your car's computer. Precise instructions are included below, however if things go wrong the results could be damaging to your engine. I provide the information below to illustrate what methods others have developed in their quest for increased performance. You should realize that any modifications you make to your own car are your own responsibility; by modifying your car you choose to accept any risks inherent in so doing.
I don't mean to scare you. To brighten the gloom-and-doom image, let me remind you that as long as you understand what the car's computer is doing and then work with it to reach your desired performance goals, all will be well. Be sure to thoroughly read the entire recipe and understand what is going on before you attempt anything; ignorance is a sure road to doom.
Before you make a single modification, consider this step mandatory. Install two gauges in your car: a quality boost gauge and a Cyberdyne (or Intellitronix) air/fuel gauge (this is available at Summit Racing Equipment for around $30). While you have some flexibility in the first gauge--you can shop for one that appeals to you--there is no fooling around with the second one. A Cyberdyne/Intellitronix gauge is known and proven to read accurately and consistently, and that's why we need it. Install them wherever you prefer; just be sure to do it!
Why are we installing these gauges? The first one should be very simple to figure out - we will be tuning the car to different boost levels and we must always know where we are at. The second gauge may seem less obvious, so let me explain. The Chrysler engine controls do not feature a mass airflow sensor. In normal driving this does not present a problem; the computer monitors the O2 sensor to decide how much fuel to inject. At WOT (wide-open throttle) things change; the computer no longer acknowledges the O2 sensor's signal. Instead it monitors various other sensors (throttle position, rpm, intake manifold pressure, etc) and then consults a preprogrammed look-up chart to decide how long to pulse the injectors. This is how our air/fuel ratio is determined at WOT.
So let's say you make some hardware changes. You add a ported head, for example, or maybe install a hotter cam, a larger throttle body, or something else. Now there is more air flowing into the engine. The computer does not know this but can still compensate in normal driving from the O2 sensor's data. At WOT, however, it reverts to only injecting enough fuel for the stock hardware you used to have; your new hardware isn't programmed into the look-up tables. What happens to the engine in this situation? Your air/fuel mixture gets leaner, which causes combustion temperatures to climb. Once they get high enough, things start to melt. Literally. Pistons are typically the first thing to go. Understand this point right now; engrave it into your brain: going lean is a sure ticket to an engine rebuild.
Avoiding that situation is easy. Just install these two gauges and pay attention to them. The Cyberdyne gauge is a 10-segment LED of various colors; lights 9 and 10 are bright red. Only having the 8th light lit is too lean; if you go to WOT and that's all you see then back out of it immediately - save the engine for another day. Illuminating the 9th light is safe (and actually optimal for best-possible drag strip times) but some people feel a little scared living 'on the edge' like this. If you feel that way, fine; lighting the 10th light is richer (which causes combustion temperatures to drop) and thus safer. When #10 lights up you'll use a little more fuel than with only #9 lit; you'll also slow down a little bit but you definitely will not melt anything. How many lights should you aim for? Use this info and make your own call. Whatever you decide, be consistent and comfortable with it. For that reason, install these gauges while your car is still stock. Get used to how they work; see what the computer does when it knows exactly what is going on; impress your friends when they bum rides off you. Once you are completely comfortable and ready to go faster, proceed to Stage 1.
Depending on the exact year and model of your turbo engine, it generates between 7-12 psi of boost stock. The exact level you start at doesn't matter, though, because we are going to go higher. First, though, are a few simple changes that all together add up. Switch to a colder thermostat. 195^ is stock; switching to 180^ is an improvement but go with a 160^ if you can find one. Then drop in spark plugs that are two heat ranges colder, ie go from a Champion RN12YC to an RN9YC. (If you decide to run another name brand of plug, go ahead... but DO NOT use Bosch Platinums!!! Their tips are prone to breaking down at higher boost pressures. Literally.) Next, visit an alignment shop and have them set a little toe-out up front (about 2/32") so that the wheels will pull straight ahead under acceleration. If the shop doesn't want to go out of their 'spec' range then have them set it right on the line, as close to that figure as they are willing to go.
Another important thing to do at this point is to install an upgraded exhaust system (as mentioned in Recipe A). Decide how wild you want to go and then do it now. Why do this before upping the boost? Because on the average, just opening the exhaust system will allow for more boost to be made. You don't want to dial in your boost control, then open the exhaust, and then have to redial everything in (and this scenario will happen if you wait until later to open the exhaust) so just go ahead and take care of it now. Besides, it sounds cool.
And now for the fun part: upping the boost. Stage 1 calls for a target boost level maximum of 12psi. To achieve this boost level we are going to set up a two-stage boost control. Read the instructions carefully in order to install the valve properly; be sure to consult the diagram as well to eliminate any confusion. Once you understand what is going on it is actually quite easy to do; don't get discouraged.
1. Remove the hose coming out of the wastegate actuator can and plug the hose. Find a source of manifold pressure/vacuum (at the turbo's output barb if your turbo has one, or else from the intake manifold itself) and run a new short rubber vacuum line directly from this source of manifold pressure to your wastegate actuator can's hose barb.
2. Test drive the car. If you've only got 5 to 7 psi of boost, things are good. Now you have to find the restrictor. It's in the wastegate solenoid vacuum lines that you just rendered useless when you unplugged the hose from your turbo, OR it might be in a tube that comes straight out of your turbo.
3. Cut your new rubber line in half, then reconnect it back together using the restrictor. Now you have a direct tube from intake manifold (or turbo output barb) to the wastegate actuator can hose barb, with the restrictor in the line, right? Good.
4. Mount a solenoid underhood as close to your vacuum source and wastegate as possible.
5. Cut your new rubber line in half again between the restrictor and the wastegate actuator can. Get a vacuum tee and push the two tubing halves you just cut onto the tee. That leaves one barb of the tee open. Mount a check valve to the open barb so that it lets air blow out but won't let air get sucked in. (Make sure you point it the right way!) With short rubber tubing, connect the other end of the check valve (the unconnected end) to the center barb of the solenoid.
6. Now get one of your bleed valves and crack it open SLIGHTLY, so you can BARELY blow through it. With another short piece of tubing, connect this bleed valve to the solenoid's off barb. (You may elect to just leave this bleed valve closed entirely; if so, you can simply plug this barb.) This is the low-level valve. Then crack the other valve open, so that you can blow a LITTLE more air through it than the first one. Connect this valve to the solenoid's on barb. This is the high-level valve.
7. Install a single-throw single-pole toggle switch (a simple on-off toggle) in a convenient place on your dash. Ground either one of the toggle's two wires on or near your dash. Solder a long extension onto the other toggle wire, shrink-wrap it, and run the wire through the firewall. Under the hood, connect this wire to either one of the solenoid's wires. Take the only remaining solenoid wire and run it to a positive source that is only live when the car's on. (Placing a small 1 amp inline fuse in this wire is a good idea.) That's it, you're done!
Now you dial it in. Take a ride and nail it in a higher gear (so that you can stay in full boost for a little while) with the toggle switch off. Note what boost level is produced. Then, while still under boost, flip the toggle on. Your boost level will immediately jump to a higher level; note this level of boost as well. If you SLIGHTLY opened the second bleed valve, as instructed, you won't hit overboost cutout; if you do happen to hit cutout then just make a mental note of it. Now let out of the throttle.
You'll have 2 boost level settings, say 7-8 psi & 11-12 psi. All you need to do is adjust each valve until each boost level is where you want it; the more one of the valves is open, the higher that particular level of boost. For simplicity, leave the toggle switch off and work on only the low level until it is where you'd like it (7 psi works very well), then leave the switch on and keep adjusting only the high setting until you get it dialed in to 12 psi. Be sure to read your Cyberdyne air/fuel gauge during this adjustment process (and read your spark plugs after you are done) to make sure you've got enough fuel. Remember: going lean is a sure ticket to an engine rebuild.
How do you read your spark plugs? Here are some guidelines. Install a new set and then go for one WOT pass down a back road. Now pull each one out (be careful not to burn yourself!) and look very closely. You want to see sharp corners on the electrodes and no "salt & pepper" on the center porcelain insulator (salt = tiny melted aluminum globs, pepper = carbon deposits that have "splashed" onto it). If the electrodes have sharp corners before a run and rounded corners afterwards, you're probably lean; add fuel. Salt and/or pepper is probably from detonation; retard timing, or lower compression. Cracked porcelain is definitely from detonation; retard timing, or lower compression significantly (such as with a headsaver gasket by Fel Pro). Real dark porcelain = too rich; take some fuel away. Grey porcelain = good; yellow porcelain = gasoline additives; rust-colored porcelain = 104 octane booster.
Anyway, back to our setup. The beauty of it is this: you can come out of the hole like gangbusters without burning your tires up (at 7 psi or so), then flip the toggle on to 12 psi after you've already launched. With this launch technique, the boost will not spike to cut-out! Flooring the car on "low", then flipping on the toggle after you already hit your "low" boost setting, will raise you to your 12 psi setting while nearly eliminating spiking. This simple high-low switch knocked .2 seconds off the Acclaim's launch and stopped the boost spiking. Launch hard on 7 psi, flip it to 12 psi about 20 feet out, and you will burn less rubber while also running faster. Once you get the hang of using the switch, you should really improve those low-traction stoplight street launches that tend to fry your tires right now.
Sneaking up on 12 psi very gradually while keeping an eye on things (ie - checking your plugs for signs of detonation) is the key to success. The disaster stories you hear about bleed-offs are usually caused by people with dirty fuel filters or weak fuel pumps, or those who jump the boost up all at once, or those that never check their gauges or plugs. 12 psi of boost is well within the parameters of your computer and is harmless IF your fuel system is healthy.
To see if your fuel system is OK, connect a fuel pressure gauge to the schraeda valve on your fuel rail, run the gauge tubing to your windshield, and tape the gauge to your windshield wiper facing the driver. Run high octane unleaded (92-94). At wide open throttle @ 12 psi of boost, in 3rd gear, at 4,500 to 5,000 rpm, you should see 67 psi of fuel pressure (55 psi over 12). If so, you've proven to have pump capacity and a clean fuel filter. When reading your spark plugs, make sure you don't have one cylinder way leaner than the others. If you can't read your plugs because they're all white, add just an ounce or two of 104+ octane booster. Go for a ride, and when you come home you'll be able to see a rusty color on one side of each plug. If one plug has a lot less color on it, forget about running high boost until you have even fuel delivery.
The cost of Stage 1 mods (including Stage 0) is at most $125 and even then it is only that high if you get raped by the alignment shop; the bleed hardware ought to set you back less than $10. What sort of performance inprovement results? In the case of Gus, his bone stock automatic 1989 Acclaim dropped a full second off its ET, going from 16.99 @ 78.74mph to 15.99 @ 82.82mph, and that was with no exhaust modifications. So there you have it - chop an easy second off your timeslip just by taking matters into your own hands.
Okay, so you've been running 12psi for a few weeks now. You've gotten used to the power - now you want more. Here is the next step.
The next thing to do is remove the balance shafts from the engine, assuming you have them. These shafts are used to counteract the vibration and buzziness which is inherent in a four cylinder engine. They are rumored to cost a stock 2.5L TurboI 14 horsepower. Well, we can't have parasites like that now, can we? Once the shafts are out the engine will still run fine; it will just transmit a little more vibration to the rest of the car. This is harmless.
An added benefit to yanking the balance shafts is less obvious: it lightens the car. Weight is the natural enemy of speed and lighter is always better (at the dragstip, anyway). For front-wheel drive cars, though, keeping the majority of the weight up front is critical for traction when launching. We have just lightened the nose of the car, so how do we restore (or enhance) the front-rear ratio? Removing at least an equal amount of mass from the rear of the car is the answer. What to remove? Start in the trunk/hatchback and gut it. Sound deadener, carpet, spare tire, anything that isn't part of the car itself. Just for curiosity, weigh all this stuff once it is out of the car - it may surprise you.
Lastly, we will again increase the boost pressure a bit. However, we will now be hitting the computer-enforced limit of 14psi (and beyond). We need to stop the computer from fighting our efforts. A pop-off/bleed setup attacks this problem pneumatically; Gus wrote a great web page on various ways to raise your overboost cutout point.
Now that the computer will not shut down on us, we are ready to increase boost pressure again. Our target level for Stage 2 is 15psi of boost. To get it, we will adjust only the high-level bleed valve just as we did in Stage 1. Remember to JUST BARELY open the valve further than it was, always in small increments, until the desired level is reached. As always, keep reading your air/fuel gauge to ensure that there is enough fuel in the mixture. Even though we are going over 14psi, the computer is programmed richly enough that we should be okay (unless your particular fuel system is weak--see Stage 1 for troubleshooting tips). Once you are dialed in at 15psi, you should again park the car and read the spark plugs like we did before. If the plugs say that all is well, you're done with Stage 2.
How much more performance can we expect now? With Gus and his Acclaim, he dropped from 15.99 @ 82.82mph (his Stage 1 best) to 14.93 @ 91.35mph. Again, another full second choped off the ET, just by knowing how the process operates and how to work with it. (It should be noted that at this point, Gus did open his exhaust system somewhat - but we already did it in Stage 1. Also, you will not see quite as big a gain if your car didn't have balance shafts.) Keep an eye on that Cyberdyne gauge and read your spark plugs, and you'll have safe, reliable performance.
Now we're really getting serious. In order for any further modifications to be as effective as possible, it is time to add an air-to-air intercooler. If you already have an intercooler but it is the smallish stock one, you may consider upgrading to a larger, more efficient one. When it comes to making power, intercooler size does matter: go as big as you can fit in the car.
There are two general methods for intercooling: have one custom made to your specifications or else scrounge one up and find a way to make it fit. If you want to have one made, there's only one place you should call: Spearco. This method may cost you--some Shelby enthusiasts have laid out around $500--but the result will be unparalleled from a performace standpoint. Would you rather try your luck at the local junkyards? Go for it; just remember to get the largest intercooler you can lay your hands on. Hey--some guys have even stuffed a Cummins diesel intercooler in their cars! Once you do figure out which intercooler to use and where to mount it, you'll have to plumb it into your intake system. Creating your own intake system is actually pretty simple, though, if you know the right tricks.
Whichever intercooler you install, be sure to expose it to cool outside air. In other words, mount it in the nose of the car ahead of the radiator. (Mounting an intercooler in the hot engine bay is a bad idea, performance-wise.) Be sure a healthy amount of air can flow through the intercooler's fins; design some sort of shroud or airdam if necessary.
Important tip: when adding an intercooler to a blow-though turbo system (where the intake air exits the turbo before passing through the throttle body) it is important to add a blow-off valve just before the throttle body. A blow-off valve is designed to open during vacuum, preventing compressor surge. You can use a stock one like I did; just insert a short piece of exhaust pipe with a flange welded to it. Be sure to cover the vent tube with some sort of filtration material since air will be drawn in through this opening at certain times. You can make it look nice by adding a small K&N filter; I just tie-wrapped a scrap piece of cloth for the time being.
Now that we have an intercooler you'll need to pay close attention to your Cyberdyne gauge. Most Shelby enthusiasts have learned that the stock computer calibration will still deliver an adequate fuel supply for an intercooler at 14psi but each case might be different. If you need to add more fuel there are many ways to do so; check out Gus Mahon's fuel page which lists many of your options.
What can we expect now? Hard to say. Your performance will certainly increase but the exact difference depends on the intercooler you choose, how you mount it, and so on. Follow the tips outlined in Stage 3 and you'll be sure to achieve the maximum possible gain.
Modified on 4/2/99.