Fly on the wall

A friend of mine just swapped out his 32lb injectors for 36lb. He says he doesn't need a new tune. I'm trying to convince him he does. Is there anybody that tunes their own car or has specific knowledge on why he needs a reflash and the repercussions if he doesn't. I'll pass this along to him. He owns a '93 Camaro.

BALLSS

your friend will soon discover his car is running rich...and all that goes with that.

SS RRR

iTrader: (2)

Wondering why the larger injectors are needed. If the same logic applies as the "no tune necessary for larger injectors" then the are probably are not needed.

97lt1camaro

iTrader: (3)

Just a question that might not be overly accurate. Can the PCM compensate for a certain increase in injector size at all without technically needing a retune ? Or is the difference in injector size too great for the PCM to be able to control ?

It would be no different then an exhaust leak correct? It's a variable the PCM doesn't see, it tries to compensate for it.

In short, I'm asking what CAN the pcm compensate up to ?

Puck

iTrader: (17)

PCM can only compensate a very small amount, just a couple percent.

Going from 32 to 36 though will definitely need to be tuned. The computer cannot compensate for that much more fuel, and even if he can't get a full tune he needs to change the injector constant at the bare minimum.

This is not considering the fact that I doubt the 36s are needed in the first place. Too large injectors hurt tuning ability and driveability for no benefit in power whatsoever.

Fly on the wall

My friend has a LE2 on a stock bottom end. His Accel 32lb injectors were not working correctly so he picked up a set of 36lb Racetronix.

Mystery Bird

iTrader: (7)

Get tuned before too much gas winds up in the crankcase and starts to take out the bearings. Injectors are the one thing you should never drive without tuning.

SS RRR

iTrader: (2)

He could pick up a set of used stock 24's for 20 dollars and it would be plenty.

96capricemgr

iTrader: (1)

It is even worse on a 93 than later years because the O2s take longer to warm up to begin trying to compensate and I believe the fuel trim learn is reset at each shutdown.

Puck

iTrader: (17)

Yep, and with no MAF to accurately measure incoming air, it cannot adjust as well as the later year computers.

nitrous2fast

iTrader: (2)

I love all the half truths in here...

96capricemgr

iTrader: (1)

like what

Puck

iTrader: (17)

If you mean the OP and the guy mentioned then I agree.

If you also think going from 32s to 36s doesnt need a tune, then I feel bad for your car!

nitrous2fast

iTrader: (2)

I was talking about the fueling and pcm compensation. The pcm can add up to 50% more fuel before throwing a code. The same goes for decreasing fuel. Does that mean that you shouldn't get a tune? No. I like make tuning adjustments for any modification that effects the air ingestion. Also a maf doesn't make the pcm be able to compensate for fueling changes any better than the o2s. Infact the o2s actually have the final say when it comes to telling the engine about fueling changes in closed loop. Yes I agree the heated o2s are far quicker at noticing afr changes after cold start. But better... No. Also a maf deosnt tell the pcm about afr changes, so that isn't even a variable anyway. Overall changing anything that effects injectors constant without tune changes is pretty noobish and shows overall ignorance.