What are your smoothing techniques

[SinisterSS]

My BENs are around 1.00X in most cells with the worst one probably around 1.01. If I get a chance tonight, I'll post a screenshot of the VE. It is not perfectly smooth (never, ever smoothed it) and the car performs flawlessly and the LTFTs values are all exactly the same -1.51% by design in closed loop.

It takes literally hundreds of miles of driving, logging data with multiple VE iterations under controlled conditions and then using the filter to glean the data. My approach is to fill the entire BEN table with lots of counts in each cell and make a global update to the VE. Rinse and repeat until the BENs start coming up with values like 0.996, etc.

And no, I don't tune my MAF with LTFTs. :wink:

[Delco]

Keith says that it needs to be smooth because of the interpolation of the cells, where I have stated since day one like Ross did, its what the car wants and what is what the wideband tells me it needs. So is there really a correct way or is it just a personal preference? I have tried to smooth and make it look perty, but it just doesn't seem to work as my actual differes greatly from my commanded.

Keith has a point in that you would not get away with BIG differences between cells, smoothing is helpful there, but as Rick said (hope it was you Rick) your first log of the BEN factor might produce some spikey areas, smoothing on the first pass would be a good idea to get things in the ballpark, then logs done after that will be pretty much what the engine wants, it does depend on how crazy you want to get with this stuff, but because the PCM can interpolate (256 from memory) values between the cells so you are never going to hit the same points at say 2000 - 2400 and 55 - 60kPa, so between those cells the PCM may calculate a VE number of 1.203 or 1.209 or 1.198 etc (I did a thread on that somewhere), the more logging you do, the more correction you apply will pretty much reduce those error factors.
You are always fighting the PCM interpolating between the cells, the idea is to narrow the range of that interpolation by either 'measuring it' or 'smoothing' it which is a calculated correction.

I don't spend 8hrs a day tuning cars so I just can't say 100% that you should not use smoothing all the time, mathematically it doesn't make sense to me to do it that way. But practically I'd love to hear from others, I found on my own car making the graph look like a babies blanket screwed my WBO2 values.

Delco, if you wouldn't mind passing on your eperiences with your car that would be good, I know that thing has a BEN factor of what 1.0001 everywhere!!.

Cheers
Ross

SinisterSS is right on the money , lots of data , careful gleaning out of bad daa is what is required , one or two passes will only get you intot he ballpark.

One interesting thing I noted yesterday on my combo ( this is a development version I am using in full AlphaN in anticipation of big cams etc and 2 bar ) is that IAT can have a big effect , I did 2 1 hr plus drives yesterday to a job datalogging as always and the average IAT was in the low to mid 20 deg C , all my benfactors where within 0.9998 to 1.0002 but as soon as I got into the city and had a few stop starts the IAT climbed to 50 deg C and the tune went lean ( this is a full open loop tune at present) by about 1 AFR.

Transients also mess up the BenPLX factor big time , really need to filter the data a litttle more heavily to get more accurate results , also while at steady state on the dyno with a fixed base pulse width the observed AFR will jump around by about 0.4 AFR due to the combustion process so this is not all a exact science.

use the BenPLX with careful data interpritaion , a little mild smoothing and lots and lots of data at constant temps. It is not there to take the tune out of tuning but to help get to the base tune in a quicker time frame.

the other thing is you wont have a smooth VE table in the real world , it will have little ripples in it due to the inlet harmonics - for this reason I tend to use localised smoothing at a low factor rather than a blanket smooth.

[SinisterSS]

Here's the VE for my LS6 with 1.75" Tri-Y headers, 3" dual exhaust with x-pipe, and a honking big K&N filter. Needless to say, the VE wasn't even close in stock form.

This VE was created by six to eight iterations (didn't keep track) and has less than 1% error in the BEN, beautiful LTFTs and drivability.

Why smooth it?

[Black02SS]

Ok guys, I thought I was going nuts trying to get this stuff smooth. I did a log today and decided not to smooth, what do you know, my BEN was pretty close after one pass. I also noticed what Delco was refering to, my IAT's jumped up to 180*F (no C*) here, and my AFR went to the high 15's low 16's and I didn't know what had went wrong as the tune was the same, I just restarted my car. Could the timing reduction for IAT cause this or is it just the fact that the intake temps were so hot? I had my car dialed in when I was using HPT with a spikey table and was told that it was incorrect and needed to be blanket smooth which is why I tried re-doing it.

Could you guys specify more in depth on what you use to filter out the data? How many cell counts does one consider "engough" before you can move to the next cell? Obviously the more the better, but is there a magic number that works well for ya'll? I personally like to see ~50 counts in each cell for part throttle when doing the tune.

Thanks for all the replies and help.

[SinisterSS]

50 to 5000 counts.

Filter at different percentages, if you have 5000, start with a super fine one and see how many it counts it gets rid of. If you have 50, a more course filter.

[mistermike]

Smoothing? Not a problem.
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[GMPX]

Nice burnout pad :lol: