Z28Camaro30Ann

iTrader: (15)

Increasing the Injector size actually LEANS OUT the fueling. When I had 32# Injectors, I was running SUPER rich. So much that it was unable to idle on its own and my O2's were reading over 1000 at idle what little time it WAS running. I raised the injectors constant to 42# and low and behold, it would idle and the injectors began reading a little closer to normal from that and nothing else changed. Then I began tuning the timing tables, AFR tables, etc...

chief455

iTrader: (21)

So do you think you may be in the same tuning spot now (rich) actually having installed larger injectors?
I'll stop here, but it seems like a simply 'tweak and see what happens' idea - especially since it has worked for you before.

Good luck - I'll be watching your results.

gregrob

iTrader: (8)

First of all you guys need to learn the difference between closed loop, and speed density. They are not the same....

Second, even using the MAF the computer DOES use the VE tables to determine fueling requirements. It use the MAF calibration first, then corrects it with the values in the VE tables AND feedback from the 02s, hence "closed loop".

You can run closed loop speed density which uses the VE tables (MAP values...) and 02 feedback to determine fueling requirements.

Or open loop speed density which relies solely on the data in the VE tables ( save a few modifier tables such as IAT) to determine fueling and WILL NOT try to correct itself to the targeted stoich value in the PCM.

chief455

iTrader: (21)

gregrob - do OBD1 and OBD2 LT-1 ECUs utilize this same logic?
I believe 93 only is a speed density program, so 94-95 same as 96-97?

Info from VEMaster creator website:
"EE: 94-95 Corvette, Camaro/Firebird, Impala, and other LT1-based B-bodies. Note that the VE tables are used only in the backup Speed Density mode on these cars (i.e. as long as the maf is plugged in and working, VEMaster will have no apparent effect.) You can also explicitly enable SD mode via Tunercat or LT1Edit."

You are saying this is incorrect?

gregrob

iTrader: (8)

Yes I am. If you dont believe me, try pulling 30% from the VE tables at idle and watch what happens to the fuel trims

chief455

iTrader: (21)

I will test what you said about VE tables in closed loop MAF.
Every other LT-1 tuning 'how to' on the net I've read says the opposite.
Darn internet

just can't believe anything without verification.

gregrob

iTrader: (8)

Regardless, tune the VE tables in SD then tune the MAF tables.

Jon A

Interesting stuff. While I certainly wouldn’t argue it isn’t ideal to have the VE tables all tuned nicely, especially if one wants to experiment with and without the MAF, if you plan to stick with the MAF in my opinion it’s a whole lot of effort for something that makes little or no difference.

I don’t claim to understand absolutely everything about how the PCM does what it does and it wouldn’t surprise me terribly if the VE tables are used in the calculations as an initial baseline to help get the “first guess” fueling correct, but I’m pretty darn sure after driving the car a couple days the Long Term Trims take care of that completely—that’s what they’re for. With different VE table values would the LT’s end up at different values? Even if they do, it still seems like a moot point to me as long as the LT’s aren’t close to maxing out. If the MAF is calibrated correctly, your injector constant/fuel pressure are correct and there’s nothing mechanically wrong, the LT’s do a fine job of keeping the AFR right where it should be in all part throttle conditions in my experience. That’s when the car is actually moving, idle is a different story.

So again, I won’t go so far as to say it’s a complete waste of time, but in my experience I always have other things much higher on the list of priorities to spend the time on.

WS Sick

When youre long terms are hovering around 160 or 108 you'll see the need to have the VEs pretty close to start with. After all you want those corrections to be as close to 128 as possible.