PCM Diagnostics & Tuning - VE table? PCM learning

How far from the VE-table are the PCM capable of adjusting?

Lets say that one cell is 50 can the PCM adjust it (learn) so much as +30?
What are the limitations?

I´m just curious :eyes: :confused:

How far from the VE-table are the PCM capable of adjusting?

Lets say that one cell is 50 can the PCM adjust it (learn) so much as +30?
What are the limitations?

I´m just curious :eyes: :confused:

What ever you set the MAX/MIN fuel trims to. I believe they're 25% stock.

I didn´t know that, Thanks... Can i find it in hptuners?

I didn´t know that, Thanks... Can i find it in hptuners?

sure just go into the VE table and muck with the numbers. I just got mine, so im no expert, but I was able to hand enter 120 values in some cells.
i dont know what the max is though.

sure just go into the VE table and muck with the numbers. I just got mine, so im no expert, but I was able to hand enter 120 values in some cells.
i dont know what the max is though.

Yes, I know that :) I´m talking about "selflearning" how much can the PCM add to the VE before the SES comes on?

Ttt :)

fuel trims only learn when in closed loop. The PCM can learn up to 25% each way, generally that is the point the SES will come on.

It's a good idea to get you VE table as consistent as possible across the driving range to prevent weird surging or flatspots. Remeber their is not a fuel trim for every cell in the VE table, the fuel trim cells span multiple VE cells.

You shouldn't see any major changes in LTFT's as you traverse the VE table.

Chris...

OK. Thanks Chris.

Here is my VE... Running on 50% E85.

Ah, E85, that explains alot. (why you needed so much more fuel!)
How does it run? What did your investiagations reveal with regards to the ethanol being corrosive to certain components in the fuel system?

I dont have my copy of HPTuners with me, and im new with it, but I thought I remember seeing an Alcohol table somewhere...I assume that for Flex Fuel vehicles?

I have read alot about ethanol and gas, And what i can understand so is gas more corrosive to the fuelsystem then ethanol.

A tune from a FFV would be great... Anyone?

5.3 vortec is a FFV right? What injectors do they have? And i really want to se the timing tables.

I dont think you can really reference a FFV table. Flex fuel vehicles use sensors to determine how much percentage of the fuel is gas vs. ethanol. It then skews teh tables accordingly. You could tune for e-85 but dont expect it to like to run on straight gas too well.

Also, AFAIK, the ECU does not actually adjust it's VE table. Once loaded, it stays as is. The adjustments are made to the trims (LTFTs). However these eight of sixteen cells cover large areas of the VE table. Your LTFT could average 0 while in reality half the VE cells are lean and half are rich. The VE will not adjust itself to fix this.

Gas might be more corrosive, but the materials designed to resist gas may or may not be designed to resist large quantities of alcohol. All modern cars can handle small amounts of ethanol ~10% or so, but may not be be able to handle the 85% in e85. i think the critical point was fuel injectors, IIRC.

Also, as far as timing, I know you can put more into a motor running E85 (octane of 100-105)

Please keep us informed, ive been looking into E85 conversions for my GTO and my Saturn!

I dont think you can really reference a FFV table. Flex fuel vehicles use sensors to determine how much percentage of the fuel is gas vs. ethanol. It then skews teh tables accordingly. You could tune for e-85 but dont expect it to like to run on straight gas too well.

I dont want to run gas any more... Only 100% E85. A look at the timing table of an FFV when set to 100% E85 would make tuning the timing easier. Seeing the same vehicle when the table is set to 100% gas would be nuce to compare with.

your difference in timing between pump gas and e85(100-105 octane) wont be much different then pump gas and race gas (100 octane)

use the standard max timing tuning methodoloy.

use the standard max timing tuning methodoloy.

Whats that? can you explain or a link maybe :)

Thanks.

FYI - there some links in the sticky at the top of this forum.

What i just did this weekend with my GTO (my first tune ever!)
I added +5 degrees across the board, and then logged for KR. Where I had some KR, I pulled the timing out for, those specific cells. I had to pull about 2 back at the upper end of the RPM range, and a little at the low range <=800 rpms

But essentially, add SANE amounts of timing +5 in one big whack. Log it. If theres ZERO KR, add +5 more. As soon as you start seeing moderate KR, back off -2 whole table. Run again. Remove the occasional -1 or -2 KR.
I suggest doing this SEPERATELY from VE table tuning, running too rich can mask too much timing.

Sorry KR = Knock retard, from using HPTuners logging

On the big end, most find you wont gain anything going past 28º or so, even if you dont get any KR.

My above info may be wrong as it relates to ethanol.

On the big end, most find you wont gain anything going past 28º or so, even if you dont get any KR.


On gas?... or E85?

On gas?... or E85?

You know what, I was going to say that it dosnt matter because the same results were found on both pump and race gas.

Now that I think about it, Ill bet it does matter quite a bit. Ethanol may burn much slower than gasoline, hence its higher octane rating.

Forget I said anything because this may not apply here.

E-85 is what 104 octane?
That should allow/require much more timing.

As for fuel, since E-85 has a lower AFR the VE table *might* not need altering so long as you command a richer AFR. Maybe just some tweaking..?

Ethanol does burn slower than gas, and most people who run it also can bump up their compression by at least a full point.

E-85 varies from 100-105 depending on controls. Expect 100, but no more for safety and consistency.