I was wondering, is the LT1 a speed density setup?

If a car has a speed density setup then it wont know the difference if I put bigger injectors in . . . . . . This is because the density system will send the same injector impulse width to the bigger injectors instead of compensating for the bigger injectors . . . . . . . corret?

 

Only the 93's are Speed Density, anything newer had a Mass Air Flow Sensor.

I don't understand. Are you asking if you would have to get the car tuned because of the bigger injectors?

 

Thanks for responding and letting me know that.

 

I am asking if the statement I made above is true and it not if someone could set me straight on the Speed Density System Operation boundaries and guidelines to modification.

 

92-93 are speed density only. 94-97 are primarily MAF, but also have speed density. Exactly when the 94-97 use speed density is a matter of some debate.


No. Closed loop correction using Oxygen sensors is how it can correct for small changes in injector size. MAP/MAF has nothing to do with it.

Regardless, you don't let the O2s correct for injector size changes if you want your car to run as well as possible - you reprogram the injector constant.

 

Thats why the 93s are faster than the 94/97s.. JUST KIDDING

 

"speed-density" has NOTHING to do with the injectors. Its a method of measuring/calculating the mass air flow into the engine. Once it makes that calculation, the operation of a 93 speed-density ECM is basically no different than the operation of a 94/95 mass air (MAF) PCM, with regard to A/F ratio, injector constant requirements and closed loop feedback/correction.

Neither system can correct for significant changes in injector size, and it is foolish to rely on the PCM's limited correction capability (+25%, -15%) for that purpose.

 

Thats not what that show on Spike, "Truck's" said

 

Well if its on TV.....

02 corrections will adjust to a point (+25% -15% as said above) but that is not the correct way to do things. That adjustment is not enough to make up for larger injectors and is not accurate enough to make your car run at its best.

Yeah you can get away with going from 24# to 26# and just letting the car adjust for it. But put that car on a dyno before and after a tune to adjust the Inj size and i bet their is a large difrence accross the boaard.

ANother reason not to do it is what if your car starts to lean out on the 02 adjusted fuel? The car not adjust anymore and you end up with a burnt up engine.

 

And even thought it "corrects" in closed loop, when you go WOT it really gets screwed up with larger injectors than its programmed for. Oversized injectors cause negative fuel corrections, and when the PCM goes into power enrichment mode, if the PCM was cutting fuel in closed loop, it defaults to 0% correction (BLM = 128) and it runs rich by the amount the injectors are oversized....... the oil companies like it when you use that much fuel