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[ojcool]

I am posting this up to outline how a car SHOULD be tuned on a dyno with the proper equipment. This is how the process works where we are.

1) And unfortunatly this is the most frustrating from a tuners perspective step of all. Spend enough time talking with the client finding out what he has done to the car and make sure that they have taken the steps necessary to be sure that there is not something very basic that needs to be done before he comes in. Such as, does he have enough fuel system to support the power numbers he is expecting, and are these numbers even attainable with the setup he is running. Are their mechanical and basic maintainence issues that need to be addressed. I can't tell you how many times we go through all the work of strapping the car on the dyno making pulls just to find out that hes got a clogged fuel filter on the car with 40,000 miles on it. We don't keep this stuff in stock so a trip to the autoparts store has to be made. Do we have a clean air filter? What spark plug does he have in the car and is it appropriate. Are ALL the components there to do the job and do we have EXTRA plugs ect, should a change need to be made? Do all the components on the car function properly? Don't bring us a car that just need basic maintainence!! And if you have a wideband and you can get the car CLOSE on a/f ratio your going to save yourself ALOT of money right off the bat. Make sure their is enough fuel in the car to do the job and it is of the quality you plan to run!!

Step 2) Put the car on the dyno and hook up all the sensor inputs you intend to datalog. On an SRT-4 this would include:
-wideband
-fuel pressure
-Map voltage
-boost pressure
-EGT if appropriate (depending on setup and how wicked a tune the customer is going to want) This is an additional cost due to the installation of the EGT probe

Step 3) Put the car on the dyno bring to operating temp and run the car at cruise to see what a/f ratio your getting. Obviously if your blowing 11:1's at cruise something isn't right as far as fuel. (close is okay because the we generally spend time here at the end of the tune when were targeting drivability) If your getting appropriate a/f then you start to make a series of short low rpm blasts to see if the a/f ratio is safe and the car has a safe amount of timing in it to make a full dyno run.

Step 3) Do a dyno pull and datalog all your sensor input

Step 4) Make your changes based on your a/f ratio targeting 11:1 to 12:1's. This is where we start working with boost pressure. If the intake air temp is safe, the car is not detonating we start to put a combination of fuel and boost and timing into the tune untill we get to the end of the efficiency of the turbo or the targeted boost/power level the customer wants. Here is where you have a discussion with the customer about what fuel hes running, what the turbo/supercharger/is capable of safely ect.

Step 5) Timing, here is where you would start to make timing changes and log their affect on a/f ratio and power. Timing makes major changes on a/f ratio as well as power. This comes at a tradeoff of safety, is is logical to run 3 more degrees of timing to make 2-5 more HP? Is is realistic to run more boost if your only getting a couple HP out of it. Are the EGT's safe? This is where you have an open discussion with the client to explain the risks involved with putting the car closer to "the edge". In the end it is the customer who will make the call judging the amount of additonal risk he is willing to expose his engine to to get the most power out of his setup. Here we always err to the side of caution. We want you to enjoy the car, not worry yourself to death every day when your racing a Geo metro.

At any point during this process any issue can come up such as:
Fuel- is your fuel system keeping up with the demand? Is the pressure dropping off forcing us to max out the injector duty cycle? Are we detecting detornation?
Sensors or other issues-Are your other sensors capable of running these boost levels? In short, is their something the car needs to complete the tune at the boost/power level desired? Is is reasonable to run 2-3 psi more boost to attain a limited power improvement vs the risk of detonation? Do we need to stop here and make a change in mechanical parts (bigger fuel pump) If that is the case we would detune the car to a safe usable drivable setup and schedule them to return when the change is made.

Step 6) Drivablility- now it's time to run at cruise and various load levels with the scantool watching the fuel trims to see what the PCM is doing and how the car is running overall. If it's short term trims are more than 10% we need to make changes to bring them into an acceptable line or the PCM is going to start putting data into the long term and in essence detuning itself. We want the PCM happy with whats going on so it will continue to be happy for the long haul.

Step 7) Street drivabiliy, does everything on the dyno result in a car that runs good on the street and is FUN TO DRIVE. This IMO is where alot of shops let cars go out the door too quickly. We like to ride around with the customer letting him judge if he is happy with what has been done. Is it to his satifaction? It's not acceptable to just say things like, well your just going to have to live with that it's a performace car.... Unless there is a very good reason to say that such as we advised the customer he needed something that he choose not to do.



This is just an overview and any one of these steps could be modified