Well, I had mentioned in another thread that I would throw together kind of a "STFT Tuning How-To" since a few people seemed to be asking questions about it. Well, it kind of grew into a "Guide to VE Table Tuning Using Fuel Trims". In Part I, I take some time to describe how LTFT's and STFT's work, and some other stuff. Part II outlines the method I used to dial in my VE table. Alot of the info is not new, but hopefully it'll be of some help to at least some of the newbies.

This is kind of a beta version. I'd like to add some pictures into the Word document, and I'm also going to add another section about PE tuning in SD. I may also incorporate all this into a bigger "LS1 Tuning Guide" if I can keep motivated. The info is out there, but I'd like to consolidate it into one easy to understand .doc.

So take a look. Let me know if it makes sense. Those more experienced out there, let me know if I screwed anything up or left anything out. Let me know if anyone has any suggestions; stuff they would like me to add, stuff I should change, anything that doesnt make sense, improvement, etc.

Thanks!

 

Added this to the main sticky up top... thanks for the work. You may want to specify in there though that 98-00 cars (at least F-Bodies) use a secondary VE table when in SD mode, so you want to adjust the Main VE

But then also the secondary VE, perhaps those that have done SD tuning on the earlier PCMs can offer some advice

 

Excellent, very clear and concise. Thank you!!

 

I'll definitely add that in the next revision.

I would appreciate advice from someone on the best method to transfer the VE data over from the secondary table to the primary, since I have never had to mess with that.

 

i made a simple VE caculator excel sheet in which you paste your current primary and secondary VE table and your STFT histogram(averaged) and it calculates your new primary and secondary VE. It also takes percentages of your STFT's so you dont have to do one pass with 100% and another pass with 50 %. its set up like this.

STFT <-10 multiply by 0.75
STFT <-6 multiply by 0.4
STFT <-3 multiply by 0.2
-3< STFT <=0 mulitply by 1
0< STFT <4 multiply by 0.5
4 < STFT < 8 multiply by 0.75
STFT > 8 multiply by 1

Kinda like that, then it takes these values and adds/subtracts them from the old VE and calculates a new VE. I used a lesser multiplier for the negative values since I like to have the STFT slightly negative.

If you want I can email it to you and you can look at it. It is a very simple excel sheet and took only ten minutes.

 

Sure, send it my way. I'll apply it to some of my old logs and VE tables and see how close the results come to what I got doing it the hard way.

I expect that I'll include it in my guide. With your permission of course, and due credit will be given!

 

I'll send it right away from (tigerbalm2424@yahoo.com). You can use it if you want but as I stated it is a very simple spreadsheet!

 

Would you mind sending it my way also? Raider52@aol.com Thanks.

 

If you wouldn't mind I would like to see that as well! Mr_g_tek@hotmail.com Thanks!

 

I am curious as to why you do a Paste - Add first and then a Paste - Multiply % half?

 

My main and secondary VE tables have the exact same values, the only difference being the secondary table starts at 20Kpa and increases in intervals of 10 where the main starts at 15 Kpa and increases by 5.
Does this really make a difference?
Isn't it running basically the same program so I can still use the histogram and adjust the primary table and still have good results?

 

How would you go about doing this with ls1 edit and EFI Live. Does everyone use HP Tuners here. I know there is another way to go about this. Thanks, any suggestions are greatly appreciated accept for go buy HP Tuners. I have ls1 edit unlimited and have invested too much to go buying more tuning programs.

 

Hmm, i don't know if i like the idea of copying the high octane table to the low octane. Especially when you turn off PE. Personally, i'm going to leave the timing alone and do the high load tuning in open loop with all the desired a/f ratios set to 13:1.

Dapsuprslo, if you're good with excel you could write a macro that would perform the same function as the hptuners histogram. Have it average ltft's and stft's and sort them by map and rpm.

 

I use FlashScan.

Bill

 

the reason for copying hte low to the high is that when you disconnect or disable your MAF, you get dropped into the low octane table until reconnected
... so that's the reason for copying the low to high while doing SD tuning

 

This is pretty much the standard method for tuning the VE table in SD mode. Timing has a significant effect on fuel trims, so if you aren't tuning for the spark table you plan on running, you're shooting yourself in the foot. This is especially important if you plan on staying SD, since you'll be running off this table permanently.

As far as disabling PE, this is necessary as it will dump in extra fuel while you are trying to hit the higher MAP cells and throw off your trims. Yes, if you try to do a WOT run like you would for tuning your PE, you're going to get detonation. However, using my method the engine only hits these cells for a fraction of a second. I can fill almost all my STFT histogram cells up to 6000 RPM, including all max MAP (the most MAP I can pull here in the "Land of Enchamntment" is 85 kpa ) cells, with absolutely no KR at all, and I run a spark advance table that is much more aggressive than stock. This being said, I do need to add a warning about the importance of monitoring KR during every step of VE tuning to the guide.

The method you mention above is a great way to tune VE... if you have a wideband. This guide (currently) only outlines the procedure I used using my narrowband O2's. I may add other methods in at a later time. Using the method I detailed in the guide to tune my high RPM, max MAP VE cells, I am able to command a solid 12.5 AFR for every PE cell, and my O2 readings are all within 10 milivolts of eachother. Of course, without a wideband I can't verify whether or not the actual AFR equals the commanded AFR, but the similarity of the O2 readings tells me that my WOT VE cells are spot on. Which was my goal. Accurately tuning PE would of course require a wideband.

 

I paste the full value of the STFT histogram at first because the values are (usually) a good ways away from 0 (greater than +/- 5). The second time I use half the value because the STFT's are (again, usually) pretty close to zero, so I want to make a smaller adjustment so I don't overshoot. Using this method, I got very close (STFT's mostly in the +/- 2 range) after the second pass. I actually did more logging and more half value adjustments, but I never really got any closer for my effort.

 

When I tune VE in Speed Density my advance and retard histograms dont log other than on the upper most row. They only log on the first row of values. Why is this? I have my LTFT learning turned off.

 

what all do you have configured for logging? You're missing a parameter so it can't plot properly...

 

Proportional idle turned off
LTFT learning turned off
copied high octane to low octane
oh wait........

RPM
Speed
TPS
Ignition Timing Advance
KR
Mass Air flow
MAP
ECT
IAT
O2 b1s1
O2 b2s1
TPS (volts)
Idle park position airflow
STFT 1
STFT 2
LTFT 1
LTFT 2
IAC position
FTC

I can send you the log, its not my newest one but it logs these parameters. STFT's and LTFT's log although retard and advance log only on upper row.

I looked over a couple of older logs (before I disabled MAF/proportional idle/ltft learning) and the advance and retard worked fine.