yo, i was just reading gm tpi swapper's guide (which by the way, has no info on swapping, but tons on the system itself). It says that the stock ecm can handle an injector change as long as the injectors don't flow more than 10-20 percent more than the stock injectors. Is this true?

I have an 88 gta with the l98 which has 22 pound injectors, using the injector formula these injectors can handle 300 hp. Since my engine will have around 350 hp, i want to upgrade to 26 pound injectors.

upgrading to 26 lb injectors is only an 8% increase in inj flow, so in that books theory it should work, right?
thx

 

Actually that's an 18% increase, still within that 10-20%.
I have never heard that actual figure but that sounds about right. I'm doing the same swap but will end up getting amother PROM burnt because I am doing other mods at the same time.

 

It is likely that 26 lbs injectors w/ No change in Fuel pressure Will Run you VERY Rich. So rich In fact I would be worried about washing out the rings and getting fuel in the oil.

But it depends. I have done some cars that Run pretty close with 24 lbs injectors on their stock L98 Bin Because of the increased fuel demands of their Combo's. The increased WOT fuel demands were approximately compensated for by the oversized injectors.

But thats a pretty shonky way to do it. Especially with 26lbs injectors and a motor with anything less than a radical build, Your still going to be rich.

Even the cars I mentioned above, while pretty close to stoich at WOT, were Rich at other parts of the fuel curve, Idle especially.

So I personally would not just stick 26 lbs injectors On a motor w/ a stock Bin, Because You are Likely to run way rich, Like I said above.

The "right" Way to do it, would be to buy injectors wich overshoot your estimated hp by a pretty healthy margin, and then tune your chip to work well with them. That way your injector's don't see high duty cycle and You wont have any problems. (As long as you don't over do it and see Minimum PW at idle, ect )

But If your not the DIY-PROM kinda guy, you should at least have a chip with the injector constant changed Burnt for your purpose, so the ECM can have more than a snowballs Chance in hell of delivering fuel appropriately.

 

i never knew about that, that's good to know though..

so the computer has some leeway to work it..

 

Guys,

Let me be a little less under-stated.

There is no Way that the computer can compensate for 26 lbs injectors.

You WILL Run Rich.

you MIGHT be able to fudge it with drastically lowerd fuel pressure, But that is going to cause spray pattern problems.

That book is Wrong. A 20% change in injector flow Rate is HUGE.

That means that when the computer Calculates PW and then Delivers that fuel, It is delivering 20% MORE fuel than it Meant to. The Computer Calculates PW based on the injector Size it thinks it has. If it has a 20% Larger injector installed, It will deliver 20% More Fuel, unknowingly. The Computers Ability to compensate for a Low O2 is Not enough to Make up for that much of a discrepency, and thats assuming your dead on with the stock injectors, Wich your not anyway.

Its all the computer can do to keep your Block Learns anywhere near 128 on a stock setup using stock Sized injectors.

That is a Huge Amount to be Off.

You cannot get away with 26lbs injectors on a stock BIN if you have any hope of running anywhere near stoich.

But try it and see... That Black smoke your seeing Means something, and its not that your fast.

 

i have a maf car, is it possible to tune it for the larger injectors, i know that its possible with sd, but what about maf?

 

I agree with bort. i'm running 24 pound injectors and I'm running rich. In order to correct it I'm wandering around in prom burning.

 

Yes It is Possible to Correct the injector Constant in the MAF Cars.

If you don't have the facility to do it yourself, Have a look at the link in my Sig.

 

thanks when im done rebuilding my engine, and i start with the mods ill prolly mail you.