2MuchRiceMakesMeSick

What does the VE table control exactly? Is it a measure of air or fuel or something else?

horist

it's how efficient the motor is... it relates RPM to the amount of useable air entering the car... There's a theoretical maximum amount of air (under non boost conditions) that you can squeeze into a cylinder that is useable... however that'd be 100% efficiency... motors don't opporate at 100% efficiency...

so the VE table tells the PCM if x amount of air is entering, and it's at y RPM then z percent of the air is useable... so it knows how much fuel to add... if the values are wrong then the PCM will pull or add fuel via the short term fuel trims , these short term are used to build an average for the long term fuel trims

HumpinSS

iTrader: (1)

Not neccesarily mine was only + by about 5-7 no more than that

2MuchRiceMakesMeSick

Wow, now I understand VE tables. You know alot about tuning. Thanks alot.

Would someone be willing to look at my log files from hptuners and tell me what I need to change? I really am not sure what to look for but I am willing to learn.

marc_w

So - WOULD it be a good idea to calculate out a VE table via the "VE table cracked" thread... hit up the IFR table to get fueling in the ballpark... and then go back to the VE to fine tune out any more fueling changes?

It seems as though with the fuel trims working they way they do, it's really not necessary to go through all of that trouble. The stock VE would be adequate because it's within the adjustment range of the fuel trims...

P Mack

iTrader: (6)

Not necessarily. Any inaccuracy in your MAF will show up directly in your VE calculations. The general concensus is to tune VE with a wideband or ltrims rather than calculations, which will get you good results even if your other tables are off.

P Mack

iTrader: (6)

Not really. For example, fuel trim cell 15 covers 2400 rpm to redline at high MAP. If you change your cam and your VE goes up by 5% at 3000 rpm and 15% at redline, you still only have one fuel trim cell covering that whole area. You're ltrim might be 10% so while it would kind of work, it's too blunt of a tool to work well.

marc_w

Okay, so it still really comes down to wideband tuning...

Dang.

Another_User

Sh**. I had a feeling you were going to say something like that. Well...I guess I am going hunting for vacuum leaks while I am installing my 160 stat tonight...if it ever gets here. How can something show up in town before 6 am, leave the UPS place in town before 10 am, and still not be here at almost 7pm?

Anyways...where are all the places this sucker could be leaking? I am thinking about just sticking a cap on my pcv port for starters, and checking the seal on my throttle body and rubber piece between the MAF and throttle body. Where else do I need to worry about?

HumpinSS

iTrader: (1)

Since both of my banks showed the same increase. I started after the MAF since it and the o2 sensor seemed to be fighting each other. I did the PCV mod that used two fuel filter to help with oil consumption and the heat adn the oil loosened up my hoses and allowed air to enter right past the barbs. As soon as i grabbed it it came right off in my hand. So i am redoiing the whole thing and hoping :fingerscrossed: this cures it but i wont really find out till my y-pipe gets here and installed. Hopefully tonight or tomorrow.

I also put the end of the hose in my mouth and capped the other end i was able to pull air through there just as easy as me brething. That cant be good :angry:

Another_User

Hmmm. I have been beating myself up with this all day, trying to figure out what is going on. With my stock VE table, IFR, MAF, etc my trims were consistently +10ish, have been for almost a year. Using my old MAFT I could get them all negative... Thinking about how it works, if you add +10% airflow your trims will settle around 10 less. Adding 10% fuel through the IFR table won't necessarily work that way. The MAF affects all fueling at all times. The IFR only affects everything based on injector flow by vacuum, which explains why it would be impossible for me to tune low vacuum (and it would always want to add fuel). At low vacuum you need to add more fuel than your car would normally allow...after I am done searching for (hopefully non-existent) vacuum leaks, I am going old-school on this ****. I really want to see if changing the MAF table moves me lower on the spark timing table... Ugh...tuning woes.

horist

Making progress I'm targeting +/- 5 for all cells

http://www.horist.com/images/hptuners/STFTLog5.jpg

Watch22

I found a leak yesterday right behind my MAF. Before plugging the leak my LTFT were 15+, and now there 11-11.5+. I ordered adapters to move my rear O2's to the front locations to help with the fluctuating numbers (The rears have a better heating element.)

Another_User
I scaled my MAF by 10% and it did move me down on the spark table. As a test I copied my spark table and moved it down two lines. I don't think this is the correct way. I would like to get everything done through the VE table.

Another_User

Well thats what I want to do too...but if plugging up any vacuum leaks (if there are any) doesn't work, I don't know...
I still have never seen a successful tune done completely via the VE table. I'm beginning to doubt it can be done...
Well using the MAF table to riched it up made all my trims 0 or negative, and I have more timing advance throughout the curve. I didn't really wander off from where my spark was in relation to airflow before either. My changes were, install 160 degree stat, plug EGR (which was disabled before anyways), add Z06 VE table, stock (98) timing, 10% increase (times 1.1) on my MAF table. Very interesting results. My trims go from 0 on both the edges to about -5 towards the middle where the VE table slopes up.

2MuchRiceMakesMeSick

This is a headache, one day its almost perfect, the the weather changes and the ltrims are way off. Any reason why?

P Mack

iTrader: (6)

My best guess would be humidity. The map sensor can't tell how much partial pressure is due to humidity. The maf can't tell how much of the flow is water vapor instead of air.

Another_User

My guess is air temperature. I noticed that as the intake air temperature heats up, more fuel gets added. I think there is a table for that too...so many tables..I forget. But the trims definitely go up as the intake air gets hotter.

2MuchRiceMakesMeSick

Do I have to use wideband to edit my VE tables. I have stock o2s w/ sims. I plan on getting wideband soon, but what happens for now? Will it get me in the ball park, or is it totally off?

Another_User

It could be dead-on...or it could be way off. I have been saving my money for a wideband O2 system...and knock sensors...and an LS6 intake...and...oh hell, I should just have a direct withdrawal from my account every month to the sponsors.

Pro Mouse

iTrader: (15)

Very True,How much are Wide Band o2's anyway?