Dyno tuning a computer tune

[aldive]

What is actually involved in the custom tuning of your computer based on Dyno runs?

What does one gain doing this verses having a tune programmed based on your vehicle and its modifications?

 

[Nate1]

AFAIK dyno run optimized tuning programs are optimized for your specific vehicle by using wideband oxygen senor data to keep your fuel curve as optimal as possible... not too rich nor lean... I think stoich is the correct term.

It would, I assume, also be possible to find your optimum shift points based on your specific vehicle's torque and hp peaks...

 

[Doug904]

Dyno tuning has alot of important values to look at. A/F readings are just one of a few different items to review while doing so. A 14.6 a/f ratio isn't really what your looking for at WOT but depending on the engine and it's modifications anywhere from 11.0-13.5 is what you want.

Also, there is an asigned value in the PCM for the a/f ratio under different loads and situations. Ensuring that the actual a/f ratio is what the computer is commanding will help bring everything in order. For example, if the computer is commanding a 12.5 a/f ratio but seeing a 13.5 then the spark tables will be too much and this could possibly affect timing by use of the knock sensor. If it is too rich then it would affect milage and could also cause a CEL because the o2 sensors are seeing one thing and the computer is commanding another.

Finally driveability, when dyno tuning you have to use a Datalogger and this will tell you the short and long term fuel trims which can mean the difference between a bad idle or good idle and there again affect load which goes back to spark and fuel tables. The Mass air meter in this equation means everything, the mass air meter gives readings that controll up to 80% of the engine's management system and so it means the world. Companies like Pro-M can really screw the readings from the MAF up so a dynotune can help bring it all back into play. This is why with SCT's software you don't have to change MAF's to upgrade injector sizing, we have the ability to change all the values in the PCM.

That's is just a small run down of things to watch and adjust while dyno tuning, there are other values such as dashpot adjustment for deceleration speeds, IAC transfer functions to control idle adjustment(something you adjust to make a 422 cam idle good on a 4.0 OHV), and alot of other items.

If you have any other questions then feel free to ask, I can't even think of all of the values to adjust or monitor right off hand but I have a program in my datalogger that saves a list of values and I can post it if you'd like.

Thanks, Doug.

 

[aldive]

Doug, thanks for taking the time to answer questions.

 

[aldive]

Doug and others...

What would one expect in terms of increases in (1) HP (2) torque and (3) fuel economy ( I had to ask ) after dyno tuning and rewriting the tune?

 

[spindlecone]

Doug and others...

What would one expect in terms of increases in (1) HP (2) torque and (3) fuel economy ( I had to ask ) after dyno tuning and rewriting the tune?

Al, you need first to have a baseline Dyno done, than work from there.
The MAX you will ever achieve over OEM in a N/A mode may be 30,H.P and 25 TQ, even you cannot do any better, but of coarse, that remains to be seen, go for it, all it takes is money and a well thought out plan.