I was wondering how much would be involved in tuning for bigger injectors. I sold my buddy my old TPI L98 and a couple of injectors have bit the dust. Considering they want almost $100 to rebuild those(if possible), I found the SLP 25lb hr injectors for $100. I know the stock L98's had 21lb, and I know 25 is a pretty big difference and was wondering if it would need a new chip for those. The engine is basically stock. How hard would it be to reprogram for just the injectors ??? Or is it possible?? Thanks in advance guys......

 

kyL-98, im having the same problem. my motor will be done tomorrow and ive gotta know if im gonna need a chip burned or not. its a 355, vortec heads, zz-9 cam, r/rs, 24# injectors,sdpc vortec intake, as&m runners, everything has been gasket matched and ported. will i need a chip just for stepping up to the 24# injectors?...will it idle? this is a brand new motor and i want everything to be right, will someone please help us........thanks

 

If you want it to be right, you need to change the injector constant in the chip. That's a pretty simple change.

Will it run if you don't? I can't answer that.

Stuart,

You will need more changes than just the injector constant to make it "right"

 

thanks novakm, my chip wont be here for a couple of weeks, and this motor sittin in my car and not being able to fire it will drive me nuts. but if im gonna mess something up ill guess ill wait. i was just wondering if it would hurt to break it in with the factory chip......thanks

 

I'm in the same boat. New 355ci with ported Dart iron heads, 212/222 112 LSA cam, ported/siamesed stock SD TPI setup, and 24 lb/hr LT1 injectors.
I was wondering the same thing, if I should try firing it up with GM stock 350 EPROM.

 

If you run larger injectors than programmed in the eprom, you will run richer. On a "bone stock" L98 with a simple injector change, this will not be too big of a problem (assuming 24#), but bear in mind the stock eprom is bit on the rich side to start with.

Will it run? Sure. Will it run optimally? Not really. Can you compensate through mechanical means? Yes, you can get an adjustable fuel pressure reguluator to lower the fuel pressure but some AFPRs can only lower the fuel pressure so low and altering fuel pressure does not work in a linear fashion like swapping to a different injector size (ie. raising/lowering fuel pressure has it's greatest effect at high load like WOT and least effect ot low load (like idle and cruising).

On a modified engine, you should get a modified eprom to account for the other changes - ESPECIALLY with SD.

But, for all the money you are going to spend, get the eprom burning equipment and do it yourself. An injector sizing is a great place to start for your "first eprom". And, as you spend more time at it and learn the craft, you will only get better and better results.

If you want to see what can happen with a "store bought" eprom, read a story on the TPI Board by me called "ZZ4 & Stealth Ram Dyno Results". It's a horror story about a guy who had problems with a company that basically refused to help anymore in making his ZZ4 run right with a Stealth Ram and told him he had something wrong with his setup/engine and NOT their eprom.

 

Oops, forgot to post the link

https://www.thirdgen.org/techbb2/sho...hreadid=208510