HumpinSS

iTrader: (1)

I just began taking logs for ve tuning. Previously i have modified my IFR and PE vs RPM tables to get L-trims in order and to lean out the mixture. Should I go back to stock on both these tables before fooling around with the main ve table? I have derived my ve values using ChrisB's Log Analyzer and want to proceed to start tweaking the ve table. Any suggestions would be appreciated. How come the values calculated seem to be grossly off from the stock tune?

TIA

Bink

IFR and PE don't effect your VE values - so don't change them. Make sure the 100% value in the Log Analyzer is changed from 2500 to 3000. Also, Uncheck the VE Percentage so it reports in edit values.
If your current setup is grossly different than your stock setup then I would expect the VE values to be grossly different.

I responded to your PM.

HumpinSS

iTrader: (1)

My setup consists of a lid/filter,4.10 and LM, my edit mods consist of EGR delete. That is it. I took some arbitrary values from what was logged and multiplied them by 30 and then compared them to the stock tune in which there were great differences.

Bink

You need many, many data sets.For any given cell at least 50 sets. Hundreds would be better. Don't use deceleration sets. With your mods they should be very similar.
joel

HumpinSS

iTrader: (1)

I logged two 50 minutes drives including some blasts to a 130 and most of the table was filled in but i got 0's for other values. What did you do to "fudge" the cells where you got no data for?

Bink

I looked at the cells with zero data and tried to figure out ways to hit them.
For instance, a long downhill slope you can hold the brake on a little and barely open the throttle - > low load and varying RPM. This actually helped me hit quite a few "zero data" cells .

For the cells you can't hit go by the graph table and hand form for a smooth curve. Follow the existing lineform you already have. You can focus on a single MAP/kPa by by selecting the "select rows" tab in the Main VE table. In most cases, it seems to me, the MAP line smoothes out as the RPMs increase- i.e. transition points aren't as abrupt as airflow increases.

If you think about it - how accurate do the "fudged" cells have to be? ....we don't use them in normal , spirited or race driving.
Hope this helps some.
joel

deezel

No need to change the IFR and PE values right away. Play with the VE table a little bit and do some logging before changing other values. Some of my calculated values were more than 10% higher than stock... I'd suggest smaller changes to start out though.
I tuned my VE table this way:
1) Lots and lots and lots of logging
2) filter out unwanted data (FTC#, data count per cell, or whatever method you prefer)
3) Make a calculated VE table from the logs (I filled up an Excel sheet with almost 64000 frames of data)
4) Create a "blended" VE table. I used 50/50 stock/calc... average the calc and stock VE tables in all of the cells you have data. Then smooth and fill in between the cells where data is lacking.
This made noticable difference in part throttle response.

Bink

Why did you average from your old cell values??

VT2 EXEC LS1

Personally I don't believe the VE values calculated from the LFA accurately reflects the required VE values in the Main VE table. I've just finished tuning a car mafless and the VE values entered are nothing like the VE values that LFA reported.

I have the car running as smooth as it was with a maf but with much more throttle response and 101 - 100 kpa MAP @ WOT. Previous was 98 - 95 kpa MAP @ WOT.

Surprisingly tuning the car to run without a MAF is very easy with the right scan tools.

deezel

At first, I wanted to play it safe and make small changes... the mantra of learning Edit tuning. I did not use the LFA found on the web, no disrespect to those that do. I made my own pivot tables and calculated VE from RPM, MAF, MAP, and IAT. The "smoothed 50% blend" has been the best "feeling" tune I have tried with the VE table. I only have EFILive data to support any performance claims - I'd say about 10hp/tq improvement over my best tune before playing with VE tables. I've seen many post about improved throttle transitions and street manners - I have to agree. Thanks to NoGo, ChrisB, VT2, and all who have posted their suggestions and experiences with VE tuning.

VT2, I've seen you post about VE tuning before. Sounds like you have your methods down. I'm not interested in running MAFless, but I would like to optimize my VE table. Can you suggest ways to develop a more accurate VE table? I can think of a few corrections that could be applied to the 4 variable VE calculation I used - temperature variation from sensor to manifold (my iat sensor is in the maf); smooth function on MAF data before calculating VE; various types of data filtering... Just wondering how you come up with your VE table that is quite different from the methods lots of people are using. TIA

VT2 EXEC LS1

deezel

I base my VE values from the LTFT values. E.g. say at 2000rpm, MAP 55 EFILive shows a LTFT value of 9.5%. I would scale the VE value at that particular load site by 109.5% (knowing a +ve LTFT value means the PCM is adding fuel, -ve LTFT value would be the opposite) and recheck the LTFT's. I would do as much data logging as possible, over varied RPM and load sites, then extract the RPM, MAP and LTFT values and create a speadsheet with those values.

I've noticed that the factory VE values are inconsistant with the engines fueling requirements. At some load sites the values are near good enough, other load sites cause the LTFT's to be out by up to +18%. Running the car MAFless shows these descrepencies rather quickly, as the PCM cannot read the MAF values and calculate the engines fueling requirements.

Should you be running a MAF I would also revert the MAF table and IFR back to the stock settings provided the MAF and injectors are standard.

As my engine will be built shortly, and will be running the GM GrandAm cam, it is more out of necessity, and also curiousity, that I have started testing my theories on other cars. My car wont idle well with a MAF at low RPM due to the reversion in the inlet upsetting the MAF signal. My target idle speed will be between 900 - 1000rpm.

Other cars that have been tuned MAFless with LS1 Edit here in Australia are all able to run relatively low idle speeds (850 - 950 rpm) with cams as big as 242/242 @ 0.050 and 106LSA. I figure the GrandAm cam fits this category and I should achieve the same results.

NoGo

iTrader: (2)

The VE table is a direct contributor to the LTerm calculation. Tuning the VE table using LTerms is like circular reasoning.
The VE values factor in to the magnitude of the LTerms to be applied.

You can actually drive the a/f ratio of the car 'off-target' doing this.

Additionally, Lterms aren't very accurate especially with big cams. O2 sensors are very dependant on temperature and flow. Changes to the exhhaust system, cam, etc... will all effect LTerm readings significantly.

Bottom line: You can tune the VE table using LTerms, but it is kind of a messy way of doing it where you can get yourself in trouble.

The absolute best method is to use a wideband.

HumpinSS

iTrader: (1)

Well I logged and calculated the Ve's for the motor and filter all the decel data and got numbers to use for the ve table. I flashed them last night and started up the car. Instantly it felt a little smother idling and throttle response "seemed" a little crisper (I attribute that to knowing it tuned it but i am not too sure). The car feeled to pull a little better and rev a tad bit quicker but now my LTFT are off. I scaled the IFR table by 96% to get them back in line and that has seemed to correct the lean condition for now. I will continue to log and watch what is going on over the next few days as I am sure there will be more changes to be made.

NoGo

I have a question about this statement
Even though we can figure out realtime ve you still feel a wideband is the way to go? Why is this? With all the sensor inputs we have on the car why couldnt these be used to accurately pin down the correct ve's for the car?

NoGo

iTrader: (2)

Personally, I use the calculation method. It works well enough to get a good VE table.
You can also use the LTerm method as mentioned above.

Just like everything else, there is an absolute best / most reliable method. For a Ve table that is using a wideband. For most though, careful calculation will work just fine.

Brains

iTrader: (7)

My biggest problem with part-throttle VE tuning right now is my wideband doesn't give a solid reading at low exhaust flow The sensor is pretty shallow in the pipe because the bung is pretty darned thick -- I'm going to skim it down and see if the readings improve. Thus far, my low RPM VE tuning has been solely seat-of-the-pants.. While its been quite effective, it certainly has taken several flashes to get even somewhat close.

deezel

Thanks for the responses everyone.
I would have to agree with HumpinSS about the fuel trims changing. When I tried using 90% calculated VE values my trims went off and I had some PT stumbling. I suspect that I needed to return the IFR closer to stock. I really didn't want to start over from scratch on fuel tuning, so I'm currently running the 50% blend VE table mentioned before.
I think if you wanted to do VE-only tuning, you probably should leave the IFR and MAF tables stock like VT2 said. I like to think of it this way: if the stock engine is not at peak performance, its because one of the sensors or calibration tables is inaccurate. Most people use one or more of MAF, IFR, VE, and PE to tune fueling. MAP also plays a role here. So, which is most likely to be inaccurate...? The VE table. Why? The IFR (table), MAP and MAF (sensors) should be pretty accurate as long as they are not modified or damaged. Mass production/quality control should give us good enough sensors and injectors... so its the VE table thats most likely inaccurate.

I assume you would use the wideband data in place of fuel trim data to tune various ranges of the VE table, correct?

Thanks again to all for the helpful discussion.

HumpinSS

iTrader: (1)

I reverted my IFR table back to stock and when i started the ve tuning and flashed with the new values the LTrims were off by about 4% I scaled the IFR table back at that point to 96% and everything looks fine now.

NoGo

iTrader: (2)

If you are going to be determining your VE values by calculation, you need to be absolutely sure that your sensors are reporting properly and that your current tables in edit properly match your setup (they don't necessarily have to be stock).

With proper VE tuning you should be able to get even the most difficult setups to behave mildly on the street.

VT2 EXEC LS1

Agreed. Neither is a MAF and accurate sensing device when used with large cams. Too much reversion at low RPM causes the MAF frequency to become unstable. Having an idle speed of 1200 - 1400 RPM is not a fix for that problem either.

Agreed. I believe any tuning (part throttle or full throttle should ALWAYS) be checked with a wideband O2 sensor.

Bink

NoGo - You are the MAN (sorry, ...had to say it)

HumpinSS- Thanks for the help! I've said it before...I'll say it again...it never ceases to amaze me how kind people are around here. That said - obviously, I am the analog man! Question - you added 4% more fuel after the new VE values were flashed- how much of an increase (%) were your new VE values over yuor stock VE values????

Could someone tell me what "LFA" is???

Brains- The tip of the O2 sensor should be lower than the body and it should extend fully into the exhaust stream (I'm sure you know this...but it never hurts to restate). When we initially installed mine the bung was too thick and partially shielded my O2 sensor ( it bottomed out on the bung before the tip was fully exposed). We ground it down to allow for full extension and it's been less erratic since.

My two cents from my experience with my car and my setup:

Underneath it all - we have the MAF and VE Tables. Air mass (g/sec) and Throttle (kPa and rpm). Max air density is Baro....it's physics from there ( I wish it was that simple). VE table is global. I think everything else is built on these two tables - am I missing something??

10% LTFT cannot be corrected, proportionately, with the VE table as long as the MAF is functioning. VT2 - I realize you're MAFLESS and VE is your primary fuel table. (I never thought about the O2 sensors working with basically a speed density setup Hmmm....I need to think about this ....where is the correction table?.....oh, it's the FTCs!!! Duh - long day!!)

The stock VE values are not meant to be a functioning VE table in the classical sense - if it was why do they rely on the MAF? It's to provide: 1.)pulsewidth/Tip In info. 2.) function as a backup - some call it Limp Mode. 3.)Provide for cross reference checks on the MAF ( predicted values) - NoGo calls this a "Gut Check".

With a bigger cam the wideband O2 is the way to go. Prices have fallen and it's not only insurance but also a definitive method of refining the table.
Areas of your new VE table,where you're too rich or lean, can be refined by the MAP, RPM and AFR of the wideband setup (I need to pound this into my head ) .

I don't think 1200 rpm is a bad idle. I bet I can pull mine down more ...in the spring (warmer weather). We'll see.

My .02 - I'll shut up. Anything in error please correct me.
joel