Chase71Z28

But i thought that yall said i could not adjust my ve with my maf hook up. I am confused.
Thanks for your help
Chase

Another_User

So if I do get it right, I should be in good shape. What is the disadvantage of running without a MAF? I mean, it is the primary sensor that the PCM uses in closed loop.

HumpinSS

iTrader: (1)

I dont see any advantages to using the maf the only reason i am not running without it is because i would lose resolution on the ve table for fine tuning. I know that when i unpluged mine the car was more respinsive to throtle movements. I would like to know why we see such a difference with the maf hooked up and without it????? That has been a question on my mind for some time now

Another_User

I think it's the aftermarket lids. It has to be throwing the MAF table way off. I am curious to see what happens when I plug my MAF back in.

I got to thinking about it, and I think that the way the PCM handles the trims is part of the problem too. Your trims get applied to your fueling whether you are running off MAP or MAF. If you VE is off, it will affect low RPMs, slowly creeping up, but not much into the higher RPMs. Unfortunately your MAF is what is getting read a lot of the time, so once you do something that adds fuel (like a lid) it also gets applied to your fueling when the car is running off of MAP (which is less of the time). So now you have way too much fuel at lower speeds, but the MAF is saying to keep adding more. Does that sound about right?

HumpinSS

iTrader: (1)

That sounds about right and would explain how when the MAF plugged it read lean and as soon as it unplugged it read rich

Another_User

That's why I want to figure out how to calibrate the MAF table. If I can get that calibrated to match the lid, then it wouldn't matter. I think.

Another_User

Hey, how does this sound. After I finish my VE tuning (which I am nearly done...definitely no vacuum leaks), I can plug my MAF back in. Then I can log MAF frequency and fuel trims, and then multiply the airflow reading by whatever percent it would take to make the trims zero. That should allow me to calibrate my MAF table right?

P Mack

iTrader: (6)

Sounds good to me. Should be pretty simple in excel. The only thing i would add is use smoothing after changing the maf table.

HumpinSS

iTrader: (1)

That sounds good to me also

P Mack

iTrader: (6)

It's still a catch-22 for chase though. He needs to get his ve right to calibrate his maf tables and he needs his maf tables right to calibrate ve tables.

Edit: I must be lysdexic

Chase71Z28

yea i know i am in a bind here. Is there any way i can keep the line pressure down with hp tuner. I have a factory maf would it be that far off. by the way i am tuning a 93 rx7 with a 2002 ls1. I wonder if i put a maf that has been ported so that the maf table will be far off if i would rely more on the ve table. Then i would be able to tune my ve better are would that make a difference. Or does anybokedy know how to compelty tun out the maf. Thank for your help and input
Chase

Another_User

I should be able to get the VE down. I think I will try to get a rough "curve" from the trims, and leave the top end alone. The problem should only be at the low-end of the MAF table.

As for people with automatics...I don't know...is there any way they can tune down their line pressure to do fix their VE? Probably not?

nbmls1ta

PMack, thankyou for the excellent response. I really appreciate it. Your answers are very helpful. I was just curious if anyone knew for sure if the knock sensor is disabled with the MAF unplugged? I use the knock sensor religously as a guide when I am tuning. If I have knock I adjust for it, without it I could be knocking and would never know, I have duals dumped at the axle. If anyone knows for sure if the knock sensor is disabled when the MAF is unplugged I would really appreciate it if you could let me know.
Thanks
Matt

Another_User

The knock sensor is not disabled. It recorded knock and adjusted timing, just like always on mine.

nbmls1ta

Thanks for the help I appreciate it. I think I am going to try it and then do what you are planning on doing. Plug the MAF back in and then adjust the MAF table for ~0 ltims. You are tuning on your secondary VE table right? I have a 98 M6 also, do you know when our Main VE is used?? Could deleting the codes for the MAF allow our cars with the Sec. VE to use the higher resolution Main VE? Just curious why there is even a Sec. VE and when the Main VE is used, because if it defaults to the Sec. only when there is a code, deleting the codes should allow the use of the Main VE.?????
PMack said "If you instantly go w.o.t. without letting the fuel trims learn, and if your ve is way too low, you could go lean and detonate." How do I know what numbers to put in the VE to start with? If I am tuning all my Ltrims to 0 or slightly negative the Ltrim will lock at 0 in WOT. Do I use my O2's as a guide still? Say I am lean 800mv O2's or something. Should I add to the VE table in the lean area or should I use the PE table to adjust it back richer? Is there a certain point when I should add to the VE table or use the PE table? This is where I am getiing confused. If the trims lock at 0 I can't use them to adjust the VE table but I could still be very lean/rich even though the trims say 0. It just doesn't seem feasible to tune the VE accurately at WOT, without disabling (setting to 1.) all the F/A multipliers associted with WOT. I am really sorry for all the questions. I keep coming up with new ones. Just trying to wrap my brain around it.
Thanks again
Matt

Another_User

Plug the MAF back in and then adjust the MAF table for ~0 ltims.
I may not go completely to zero...I haven't decided yet. I don't expect to get all zeros on my VE histogram...but at least +/- 2. I will probably adjust my MAF table based on my results, but I expect to see some sort of curve like I see in my fuel trims. I may use a little "fudge factor" in the final results. Just something to think about.

You are tuning on your secondary VE table right?
I tune the primary and paste (the appropriate rows only) over to the secondary.

I have a 98 M6 also, do you know when our Main VE is used?
From the way it sounds the primary is used when you aren't missing your MAF, except later year cars only have a primary. With the MAF unplugged it is supposed to be using the secondary, but I feel pretty comfartable plugging the histogram numbers into the primary first.

Could deleting the codes for the MAF allow our cars with the Sec. VE to use the higher resolution Main VE?
I doubt it. I asked how we could force it and it doesn't seem to work that way. Unfortunately.

PMack said "If you instantly go w.o.t. without letting the fuel trims learn, and if your ve is way too low, you could go lean and detonate."
Yes, that will happen IF your trims aren't already negative, and your PE isn't already tuned. If your trims are positive, but have not been learned yet you could go lean because the trims get applied to your WOT when your trims are positive.

How do I know what numbers to put in the VE to start with?
You can use your stock table, or I chose to use a 2002 Z06 table to start with. If I did it over again I would probably start with my stock table though, so you should probably just use that.

If I am tuning all my Ltrims to 0 or slightly negative the Ltrim will lock at 0 in WOT. Do I use my O2's as a guide still?
Yeah. If your trims are negative you have to add PE to get your WOT fuel right again (if it is off). 890-910range. I still don't know about that, because they are not dependable. If you shoot for that you should be fine though. Some people have to run richer, some leaner. You really need a wideband O2 to be sure.

Say I am lean 800mv O2's or something. Should I add to the VE table in the lean area or should I use the PE table to adjust it back richer?
I am changing my VE based on the trims. If the trims fall into place, then use the PE to richen it back up.

Is there a certain point when I should add to the VE table or use the PE table?
You should (ideally) add PE after everything else has been changed. For VE you should be tuning part throttle, and not a bunch of WOT. Try to stay out of PE because it could affect your trims.

This is where I am getiing confused. If the trims lock at 0 I can't use them to adjust the VE table but I could still be very lean/rich even though the trims say 0.
If the trims lock at zero at WOT that means you are running richer, so it won't add fuel at WOT. That's why you need to fluctuate your throttle use and try to stay out of PE. I was actually able to get trims for some cells that I would have though unreachable at moderate throttle. The ones you can reach you will end up tuning through PE. Just make sure you start with a good, realistic, VE table.

I think that answers everything I can answer for now. Please chime in with any corrections all!

nbmls1ta

Wow, Thank-you very much for the help, I would be completely lost without you guys. I am going to give this a try. Thanks again for all you help, I hope I can tune the car this way, that would really make me fell more comfortable about inaccuracies in the MAF. I hope you all have great success in your tuning adventures, best of luck!!
Thanks
Matt

P Mack

iTrader: (6)

Here's what I did as a starting point for my ve table. I found a dyno graph of a car with similar mods to mind and compared the torque curve to a stock car. If the modded car had 5% more torque at a certain rpm, I added 5% to the ve for that rpm in the 105 kpa cell. I did that for all the cells at 105 kpa, then kind of smoothed the ve table so there was like 0% change at 20 kpa on up to 5% at 105 kpa. I don't know if that makes sense, but that is what I did. Another User's idea is good too, i'd never thought of it till he mentioned it.

nbmls1ta

Few more questions...SORRY!!
I just went out and logged a little with the MAF unplugged. Before my ltrims were -2 - 0 now they are -6 - -12. Anyway I had some knock in a few areas and pulled up the Retard histogram. The Spark tables are in g/cyl and with the MAF unplugged it is obviously not going to measure that unit anymore and all my timing advance/retard is contained in the .08 row. How do you fine tune your timing with the MAF unplugged? I can't tell where the knock happend only the rpm. Is there a way you guys are working around this? Are you adding to the VE to richen it up where there is knock or what? Unfortunately, all my ltrims are pretty negative so adding to the VE would only make it worse. I have some areas that are -1 or 0 but no way of knowing where to adjust the spark. The car seemed to run much crisper though. I have a G5X2, Pacesetter LT's, Duals dumped at the axle, Ported/Polished TB, stock LS1 intake etc. I am idling at around 55 to 60 kpa at 850 rpm is that normal?
Thanks AGAIN!!
Matt

Another_User

Heh...you said "Retard histogram". Anyways, you are right, you can't get the timing to read out with you MAF unplugged. It needs the MAF reading to determine where to put you on the table. I am going to plug my MAF back in and then finish off my timing tables. I don't know how the guys tune their timing without a MAF...I am sure there is a way though. You should just try to smooth out your VE table so you are near 0 straight across. You will never get it perfect, but you can get it real close. Then plug your MAF back in (and hopefully it doesn't throw your trims off, but it probably will). The order you should probably go in is tuning VE, then PE, and finally spark. 55ish kpa is about where I idle too, so that sounds normal.