Reduced power mode on Zs with eliminated secondaries

[1991 Corvette ZR-1]

This popped into my head a while back about reduced power mode triggered by a trouble code. I don?t know the exact amount of codes that default our cars to ?normal? mode only. Even when the chip has been set to always have full power on all the time, this is overridden by a trouble code mandating reduced power.

What I am getting at is with a fully ported top end and eliminated butterflies, a reduced power scenario sees a lot air in the chamber and not enough fuel to burn with it in normal mode, creating a lean condition. I spoke with Marc about this a bit and he mentioned running an LT5 leaned out in this manner at WOT for less than ten seconds would not cause an issue. That was a bit of a relief.

But then it had me wondering if any registry members with eliminated secondaries experienced this before.. If the engine reverts to 8 injectors because of a trouble code, if you keep the revs low, the engine should be fine as you limp it home.

[GOLDCYLON]

You need to modify your chip to account for these performance modifications and that's the bottom line. MOST of the performance chips that are available out there are only tuned for a few variables. key on, Cooling fans on early, a mod for headers and for WOT. You have now changed the air equation and fuel equation with the porting and the removal of the butterflies.

I suggest you talk to Dom Xfirez51 as he was able to port tune my car via the mail. You will need to buy a Ostrich II emulator that will allow you to up load different tunes with a piggyback chip until you achieve the desired result. You will also need an old school laptop. Dom has my 380 tune on file as a standard as I have ported heads, runners and stage 1 cams and no secondaries. Dom has every profile for every after market chip that was ever made for the last 25 years. That same laptop can record data on the car while it drives to give,
Dom clues on the tune. Dom is the only gent I know that matches tunes at different throttle positions beyond WOT.

If that does not work for you as a solution your only other option is to find a tuner with a DYNO that still knows how to do this work. Most of those folks have moved on to LSX community about 10 years ago. I can highly recommend Dom.

Good luck. GC

[1991 Corvette ZR-1]

The existing modifications I have performed have been backed up by Marc?s tunes, including updates for the removed secondaries. I am all set there. I was alluding to the actual override of the chip tuning updates if a CEL condition designed to turn off the secondary system occurred. I believe if I have interpreted it correctly, a CEL designed to limit power by cutting fuel delivery by eight injectors on a Z with eliminated secondaries, even with full power mode always enabled in the tuning for 91-95 cars will still experience a lean condition.

I was curious if any have encountered this issue before with eliminated secondary butterflies. I figured aside from the actual CEL and seat of the pants difference in the car if this were to occur, can it be limped home if rpms kept at as low as possible. Or is it automatic flatbed trip?

[GOLDCYLON]

That has not been my experience and I am San secondaries. However my car is specially tuned at different throttle positions beyond WOT. It is a delicate balance warts and all because you can completely eliminate one problem and cause another at the same time. This is way scanning and recording your car during a drive is important.

The goal is to fine the best performing middle or baseline. Before all this effort my car would just shut off. GC