At the point where tuning the EVO invovles leaning out the fuel mixture, what is the point of having larger injectors and a better fuel pump while still using the stock turbo, if it is ALREADY getting too much fuel stock?

 

People are just planning ahead is all.

 

What sort of duty cycle are the stock injectors running on a car with a lot of bolt-ons (bigger FMIC, turbo back exhaust, 20+ psi, etc.)? A lot of people with the stock turbo are pulling over 100 whp more than stock. Doesn't seem out of the question that the stock injectors could become marginal at that level. I believe that larger injectors can also avoid fuel cut on a car running stock programming and a fuel computer.

 

Larger injectors and better fuel pump allows you to use an S-AFC to drop the duty cycle of the fuel injector to get the same amount of fuel. As RichJ's comment, it does effectively raise the fuel cut.. The disadvantage is without any sort of reflash or engine management, the car would run OBNOXIOUSLY rich when it goes into open loop... However as you raise the bar by increasing the horsepower, you begin to cross the line where you just cannot supply enough fuel to the engine. Therefore the bigger injectors can provide more fuel to the engine if needed.

In closed loop, the computer adapts.. In Open loop, the maps themselves have to be altered.. Just an FYI..

 

I agree. That's why I specifically mentioned a car running larger injectors, stock programming and a fuel computer .

 

If you are tuning with an afc (also any other piggy back that alters the maf signal) you lean out the mix by reducing the amount of air "seen" by the ecu. This will raise fuel cut and also give you more timing. The computer is programmed to deliver less timing at higher airflows for safety reasons.

Also, the ecu can only compensate so much in closed loop. That is what people are refering to when logging their fuel trims.

 

Fuel Cut is really what we want to avoid when running higher boost with the stock turbo (aside from boost cut). Ultimate Racing was able to run 11s with the stock turbo with 750cc injectors with Walbro upgrade, e-manage, and S-AFCII.

 

Also, the bigger the injectors, the more you have to lean out.....more timing

 

Any one see the modified mag article of the evo and the safc2?? They called it the ams trick it was to use bigger injectors to keep the ecu from pulling timeing and loss of torque. They gained 20lbs using this.

 

The larger injectors we installed were so we could get rid of the fuel cut. Like the other guys said. By adding more fuel through the injector you can lean the car out more and let the computer allow you to run more boost. With the injectors/pump we were able to re-tune the AFC for another 20 hp and 49 ft lbs of torque. These settings are included in our Stage 4 package.

Alot of guys think the added timing you get from leaning the mixture out is a bad thing. We have to disagree, the EVO timing curve is so conservative that it is basically sickly. Getting this extra timing just starts to get the car where it needs to be.

David Buschur
www.buschurracing.com

 

Here is a good reason to run a bigger pump on a lightly modified Evo...

https://www.evolutionm.net/forums/sh...ight=fuel+pump