V6 VE Tuning Test

[Bill@HPTuners]

In regards to this post http://www.hptuners.com/forum/showpo...00&postcount=8 in the 3800 table request thread I finally got around to test what Chris stated was true and to no suprise all was true.

Basically I read the current file off of the pcm and 0'd out the entire ve table to see what affect it would have on
a. drivability
b. fuel trims

My findings are this:
a. the car started & idled like it always has without so much as a blip
b. the fuel trims didn't budge more than 1 or 2% in the 10 or so minutes I had the tune in for.

Threw the tune I read off of the pcm and
a. the car started & idled like it always has without so much as a blip
b. the fuel trims didn't budge more than 1 or 2% in the 10 or so minutes I had the tune in for before coming inside.

Take it fwiw guys but between our engineer saying VE is coded out unless the maf fails & me testing this theory by completely 0ing out the table doesn't boad well for other interpretation of how the code works lol.

Bottom line is if it makes you all warm & fuzzy inside to perform a full OLVE tune feel free but it strongly appears as if its not necessary nor will it help at all to do so.

But think of it this way, if the VE was important in normal operation why would they setup a VE table like the one in the stock file I've uploaded?

Have fun guys!

-Bill

[devildog9999]

Don't know why yours is that way Bill.. Perhaps it is the bare minimum to keep the car running in the event of Maf failure?

Mine are wayyyyy different.. I will have to go back to my old logs and scans, but the differences in "MY" car are night and day when tuning via VE and then re-enabling the maf. LTFT's, general responsivness, shift fuel, all much better. Not to mention, "IF" I do lose a maf at 110 on the back half, I know the car is still safe.

[JerryH]

First off, the effort was appreciated, but it takes a lot longer than 10 minutes for the trims to be relearned even under the most optimistic circumstances. On average it is not unreasonable to do 1-2 driving cycles of 15-30 min with at least 1 (preferably 2) engine restarts in between to make sure that the trims are learned.

A VE tune is not the end all of everything, but it is the base from which the rest of the tune is built on. After doing as complete a tune with and without VE adjustments, on my car (and all the cars I have followed the same process with) the difference is clearly different in terms of final results.

Doing a VE by itself will not do very much... using it as part of a complete process gives superior results to not using it. This is not just me, but hundreds of other tuners that came back and confirmed the very same thing.

A very important factor is number of mods. A stock or near stock car will show very little end result improvements. A well modified car will show clearly superior differences in terms of final results. Most obvious results occur on cars with sub 3.4 pulleys and aggressive aftermarket cams like the XPZ, S1(2 or 3) and XP. The VS cam is so close to stock that it does make a difference, however it is not as clearly visible as on other cams.

Now... unless the PT is modifying some other table or doing things in some other way (highly unlikely), the benefits should be the same if done (properly) with the HPT.

I am not saying that a VE tune is going to give you 50HP more in the end... I am saying that on my car mileage rose as high as 4 MPG, the car was smoother feeling and sounding... I am saying that the trims locked in over a far greater temperature and humidity range than a tune without it. I did not have to retune the MAF when temperature dropped 20 degrees and trims no longer locked in at 0 becuase they consistantly locked in over a broader range of conditions. The stability of the tune seems so much less volatile with it than without it.

[damojo2003]

Ah...i see that you went to the dark side. The car runs like crap in the beginning and then smooths out as the fuel trims get closer to 0. 10 minute scans are far from enough to get good resolution. You want to hit as many cells as possible. Everytime I do mine, I stay in 2nd gear and I see 6k rpms. Bring the car into the upper rpm range and let off the gas a bit. That will reduce the map and keep the rpms high.

[JerryH]

I don't normally suggest that people do VE tunes and run around in 2nd gear and go up to 6000 RPMs, becuase PE is disabled... and thats dangerous as heck for the engine.

One can tune the VE's upper cells, but to do it safely, thats where a WB helps. Now since I have never had a WB in the past, the benefits that I see are mostly in the idle to 100 MAP(kPa) range. Though I try to hit as many of the cells as I can touch without KR, and I basically interpolate the results and apply an average to the few cells that I cannot get to. No, this is not optimal, but if you don't have a WB, its a safe way to do it.

[Chris@HPTuners]

it's a case of "it depends"

the PCM has two options that control the main airflow logic.

Option 1 is the Airflow mode that is used if MAF fails, it can be:
- None
- Speed Density (VE)
- Alpha-N (TPS vs RPM)

Most cars are set for None or SD. This option is only looked at if the MAF fails.

Option 2 is the Airflow transient mode, it can be:
- None
- SD
- Alpha-N

On most cars this is set to none. The transient behavior logic is very simple if it is enabled. if a transient detected (by TPS delta being over a threshold) use the transient airflow source for a specified number of refs. then ramp out again to the MAF.

as an example. 2000 GTP 3800 cal (9389753 for those who are intersted) i am looking at has Option 1 set to SD and Option 2 set to None.

What this means that in most cases the VE table is never looked at and in rare cases only during throttle transients, hence tuning it to change your fuel trims is a big waste of time. As evidenced by Bill beging able to completely zero his VE table without any effect at all.

Before you ask, yes i will add these switch options to the editor as well

Hope that helps,

Chris...

[damojo2003]

Jerry
It is not that bad if you are constantly watching the computer and don't hang there for long. IMO...WB is the right way to tune this table. I have done it with the narrow band and it would take me over a week to get the decent resolution that I can do in an afternoon with my wideband. I find hanging in 2nd you can hit more cells faster and lower MPH (KPH...northern people ) than using all the gears. That is the way I do it. If you plan on keeping the car in 2nd and 5k+ rpms....then plan on having issues. Give it a try with pe enabled...you will see that if you hold it in 2nd and let off the gas a bit, you will reduce the map and then you can vary the tps to get good resolution in the upper rpm ranges.

[damojo2003]

chris
I don't know how many mods Bill has, but I have a few. My table has changed alot and there is a minor change in the maf to compensate for the change in weather. Tuning VE actually made my car more responsive with a smoother idle. The benefits in tuning this table will be the guys that a significant amount of mods including cam and rockers. We discussed on the other site how this is a reference point for changes and I will let Jerry explain that. I understand, but he explains things alot better than I do.

[Keith@HPTuners]

damojo2003, its a very simple test.. zero out your VE table and give it a try.

You might be surprised with what you find.

[Perforator]

That is interesting stuff Chris and maybe it explains why some people don't see any change and some people do.
I'm looking forward to all these additions you plan on making for us 3800 guys.

[damojo2003]

Sure, I think I can find time this afternoon after work to test. I am sure I will find ares where there is little to no change and I am sure I will see a significant change where I accelerate quickly. So we are on the same page, zero out the entire table will be the only change to the tune and of course the maf will still be connected.

[85DropTopTA]

If i set my VE to .9 accross the board my 01 bonneville SSEi surges when idleing

[johnh]

Alright...cold or not I am gonna have to test this.....hopefully, I can report back later today.

[devildog9999]

Just zero'd out mine, and all it does is stall, while trying to get an idle. I was able to keep it running, but it was a bitch to make it even around the block. I will play more after work and send up a scan.

[JFDugal]

Bill (or anyone else), try running the zero'd VE table for an extended amount of time (might want to keep the laptop handy though).

I tried something similar to what Bill did a while back after reading another VE discussion thread. My test was to set the VE table to 25% of the original (stock 2002 GTP) value keeping everything else the same. I let the car idle for about 10 to 15 minutes and came to the same conclusion that Bill posted above - that with a functioning MAF sensor the VE table did not affect vehicle operation/performance. However when I took the car for a ride, I had the engine die out while on the highway. It would crank fine, plenty of fuel and no DTCs (that I recall). Oddly enough when I flashed the PCM back to what it was before I put in the reduced VE table, it started right up and the problem never occurred again.

Since then I have re-done my VE tune (added a GenV & N* throttle body to my S1x setup) and have found that my fuel trims seem to be more consistent afterward. It seems like it's been much easier to get my LTFT's dialed in pretty close to zero with a tuned VE table.

[johnh]

Well I just had to test the 0 VE table.

Here's my process:
1. Started Car with current Calibration.
2. Started fine, drove around the block, got ECT over 100F.
3. Reflashed with 0 VE table.
4. Car was hard to start, but did, idled roughly.
5. Backed out, put in in drive, drove roughly 50ft, stalled out, couldn't keep it running, didn't want to start.
6. Reflashed back to normal Cal, started right up no problem, drove fine.

I have attached a scan with the Zero'd VE table.

Bottom line: It sure does do something...car wasn't drivable without a VE table.

[damojo2003]

Well, I guess I don't have to try this later. The VE is used during normal operation. Engine Management Advanced Tuning. On page 72 he talks about Speed Density (reference for others, not an insult in any way shape or form), in our case this table is used as a reference point.

[Keith@HPTuners]

Please read Chris' comments.

The V6 operating systems do not function the same as the V8's do. In the V6's case, use of the VE is hit or miss based on a few key parameters.

In bills case, the VE isn't used. In JohnH's case, it is.

If you zero out your VE table and you only notice a slight difference or change, then its likely not used. Zero'ing out the VE table is such a drastic change (removes all fuel) that you would notice a substantial difference like in JohnH's example.

[devildog9999]

So I think we have determined that the VE table is more usefull in some circumstances other than for the event of a MAF Failure, thus the reason I have been doing it for my tunes for years!

[Chris@HPTuners]

Well I just had to test the 0 VE table.

Here's my process:
1. Started Car with current Calibration.
2. Started fine, drove around the block, got ECT over 100F.
3. Reflashed with 0 VE table.
4. Car was hard to start, but did, idled roughly.
5. Backed out, put in in drive, drove roughly 50ft, stalled out, couldn't keep it running, didn't want to start.
6. Reflashed back to normal Cal, started right up no problem, drove fine.

I have attached a scan with the Zero'd VE table.

Bottom line: It sure does do something...car wasn't drivable without a VE table.

Please email me your .hpt file and i'll tell you how your cal is setup.

Chris...