Got the 91 RS dyno tuned a few weeks ago. Results were pretty disappointing. Car made 293whp 301tq. Got lots of mods, the engine would hit a wall at 5100rpms. The tuner was telling me those computers can't control fuel past 3600 and spark past 5k. So I needa do a computer swap. I know about EBL but dont have that kinda cash. I've read the sticky about doing the 427 swap which is I'm guessing 16197427 computer right. What are the benefits of doing this and will it help at high rpms? I'm not a tuning computer guy so I need lots of help going about this. Will it be pretty difficult to get it running? If anyone can point me in the right direction.

 

Any thoughts?

 

You may have hit the rev limiter?

you might find info on 427 in above stickies...

I would think ECU would use the SA last seen after falling off the chart.

There is an adder table that I recall goes higher than 3600 rpms for fuel. Maybe 4800 rpms. But same story as it will use same cell seen last and then use any BLM adder as well.

I have a LO3 table on my laptop. Shows the VE #s dropping over 4800 rpms so you should be OK there. I believe there is a PE enrichener as well but that is TPS% sensitive(70%?).

SA stays same over 3600. SA adder is PE may be 3 ded?

Quote: not a tuning computer guy so I need lots of help going about this.

This screams EBL. A 427 conversion might be a bit to much for you starting out.

 

Help finally
Ok I'm really new Ronny.
No rev limiter. I read somewhere that these ecu's can't control ignition past 5k or something like that. I don't know what SA means but yes it was using the last whatever at 3600 to fuel the rest of the way. My tuner was running it rich at 3600 about 11:1A/F trying to feed enough for redline. Past 3600 A/F ratio kept climbing at redline it was about 13.5:1.

What's an adder table?
PE?
VE?
I don't do my own tunes. What do you suggest?

 

No rev limiter? I thought GM has one in ECU? My def file is not that of L03 so I cant be sure.

I think GM distributor will do fine. If you are able to attain 5000+ rpms I beleive it will just continue same value that is final entry in table for SA(spark advance) and VE fueling.
I run stock GM distributor to 6000 rpms.

Q: ecu's can't control ignition past 5k

I think 6000-6200 is limit for fueling due to pulse width and timing of same PW. A good sticky in TBI forum called 'free tune". Explains TBI fuel and other.


PE is power enrichment of A/F for heavy prolonged loads. adds 2 points to A/F. Provides cooling with enrichment.

3600 running rich. Probable as the car needs a tune. Enleans at higher RPM may be due to inability to provide larger PW again due to lack of fuel(pressure/injector).

VE is fuel map cells rpm vs VAC(MAP).

You need to learn to tune. Read the stickys above in DIYProm and check out "intro to tune" part 1+2 at dynamic efi.com. I doubt you will find a professional that will want to tune TBI. Mail order tune(tbichips.com) will be frustrating as you need to provide datalogs and US Postal chips back and forth. You need to do it yourself. For sure.

EBL is your answer...

7427 thread : https://www.thirdgen.org/forums/diy-...-its-time.html