Hello all. After just purchasing my 89 corvette z51 i decided to do a little learning to clear up some rumors the previous owner has been feeding me. I have been searching and reading a LOT, and already love the community.

So now for my noob questions.

1 Being an 89 with a standard MAF setup i have been told i can run 5-6 psi with NO ecu/tuning mods at all. I was told that the ecu can compensate for this increased air. Of coarse were assuming a standard properly sized turbo, 91 octane, colder plugs, etc. How true is this? What are the stock injectors (in stock car) duty %? Would a step up to 24# injectors better facilitate this while still avoiding a tune?

2 I have been reading on self tuning, and this is not something i am against as i have experience tuning many other cars, im just trying to sort options. So my question here is are there any Colorado tuners comfortable with tuning the 89 maf system to a max of around 8 psi turbo and possibly on e85.

3 Does anyone use piggie back fuel solutions such as the apexi safc to alter the maf output to then change fuel compensation? with this i believe it possible to run larger injectors on e85 while requiring no new tune(the modification of the fuel trim in the safc for larger injectors generally increases the timing which when switching to e85 is okay) or do these things never really get used on vettes?


Car details
89 z51
l98
6speed
dana 44
j55 brakes
very crappy ac :p
borla exhaust

not yet installed
1.6 rrs
short shifter
full rear hymlink bushingless

EDIT

Quick tuning question
When using some tuning software to change the eprom bin is the ignition map accessible? ie can you tune specific ignition degrees per rpm and engine load(boost)? thanks

 

Hi Karrr !!! Welcome...
Stock MAF pegs at 250 gms/sec so at 5 lbs of boost you'll need a lot more fuel than it can deliver, not to mention the stock injectors are way too small. In the past I added fuel with FMU's, supplemental water/alcohol etc.

Today you stick in a set of Siemen's matched 63's, my new HPX MAF (600 to 800 gm/sec), an Ostrich (e-prom emulator), TunerPro RT or TunerCat RT, appropriate fuel pump upgrades, and you are ready for real time programming that will support 600 RWHP no problem. Oh almost forgot U need my base start-up program that runs from $149 to $249 depending on your need for help.

Best regards,
greg

 

Sounds like bad info. I measured my '85 L98 duty cycle in stock form with increased fuel pressure to 47 PSI and it topped out at 70%. Ideally you want to stay below 80% injector pulse width so you are capped at about 260 HP. Even at 100% pulse width you are probably only at about 330 HP. Not likely where you want to be.

BTW: AFAIK the stock injectors are 24 lb/hr @ 47 PSI

Yes, you can change the ignition map. IIRC it is a 3D table of timing vs. LV8 vs RPM or something like that. If you want to see for yourself go download TunerPro (it's free), grab the XDF for your engine and have a look at what you can do. You can do all this stuff yourself if you are determined. Pick yourself up a WBO2 sensor, an Ostrich and TunerPro RT and you will be on your way.

If that sounds daunting by all means go to an expert like Greg above.

 

1985 cars used 24 lb/hr injectors, after that they went to 22lb/hr

 

Thanks for all the info. So new question. With appropriate tuning and 40s or so injectors, how are people running the stock maf? or in these cases do they convert over to speed/density?