Has anyone found a charge temp solution?

[erics_02_z06]

If you want to do that, you can save yourself a lot of heartache by disabling the complex modeling for temp and just let the ECM use IAT for its TEMP value.

Then my VE would be tuned for just one small range of IAT, and I would still get large fuel swings.

So for now, I think the EASIEST SOLUTION IS TUNE YOUR VE AT A MODERATE TEMP. This way, your error is slightly above, and slightly below, and not from zero to one extreme (talking fuel trims)

P.S (I wasn't yelling that at you, that is just for future members reading this post, maybe they'll see that advice)

[erics_02_z06]

It is solvable like this. Take a large enough data set, hopefully from many logs from many different conditions. For every data point we know after applying the afr error, that to make the command afr match the observed afr the end result of the all the math needs to be X g/cly (CAM)

For every frame of every log we know the IAT, ECT, RPM, MAP, and what the CAM should have been for that frame to make the command afr match the observed afr. Then its a matter of what GMVE and MAT (read Bias table) make for the best fit over the whole data set.

That sounds just like what LSQCURVEFIT in Matlab will do...if you want to get together with me to discuss the math, I'll throw together an Mfile

[S2H]

If you want to do that, you can save yourself a lot of heartache by disabling the complex modeling for temp and just let the ECM use IAT for its TEMP value.

disabling the charge temp makes it 100% IAT... which unfortunately will make it swing even greater amounts thanks to a hard coded formula in the PCM that just doesnt work as 100% IAT

[S2H]

this is the problem of dumping ALL responsibility in ONE table. it is functionally not any different from IFR hacks, or PE hacks. I'd like to avoid these sort of approaches like the plague.

technically... if you dont set your bias to an appropriate value first...then you are doing a VE hack...

if you set it to values that make for stable fueling instead of fueling swings because of temperature difference... then you have tuned the bias table and you can work out a VE table that is correct...

the problem becomes with what value to call the "zero" point...
do you call 0*C actual 0 or do you call it a 21*C day as the zero point...

if we knew what the temperature was that GM considered the "Zero" value.. then we could tune it based on that

and either way...as long ass your fueling doesnt swing because of temperatures.. then it should be correct...
if its VE value of 75% on a cold day, it should be VE% value of 75 on a hot day as well..


also haviing your IAT in an area that gets a lot of heatsoak, and not a lot of "real" air movement...and further away from your engine..is a bad thing for the math of it...

the closer you can have it to your actual point of combustion..the better...
min is in the front opening of my intake.. when I open the throttle, I see an immediate response from the IAT ... I have very little heatsoak to begin with in that location, and it moves immediately towards real incoming air temperature...
within a few seconds of opening my throttle, it settles into "real" incoming air temperature

[LinearX]

disabling the charge temp makes it 100% IAT... which unfortunately will make it swing even greater amounts thanks to a hard coded formula in the PCM that just doesnt work as 100% IAT

But to Eric's point where he asked about moving all of the error attribution to just one table, it's far easier to shift that to VE by disabling the MAT calculation.

[S2H]

But to Eric's point where he asked about moving all of the error attribution to just one table, it's far easier to shift that to VE by disabling the MAT calculation.

theres no way to fix a hard coded formula... by disabling the complex cylinder charge temp it rely's on 100% IAT... which will lead to drastic fuel swings as have been proven on just about every vehicle that has tried it

unfortunately...it becomes having to tune around GM's error...

[LSxpwrdZ]

The only way to help create a value for the GMVE unknown is to use the MAF and some reverse engineering to create the GMVE value. Knowing the airflow readings will help give a more accurate measure of creating a EQ table. The reason I say this is because I've not noticed much if any error in fueling when running 100% MAF because it physically read's the air going into the engine. Yes there are error's in that as well but not to the extent of the GMVE coupled with the complex air charge calculation's. I may be completely off with my assumption but it's just a little food for thought to help accurately nail this EQ bs.

[knyght4]

OK. I used soundengineer's config to run a log yesterday. The 3d table was pretty helpful in seeing how IAT effects the dynamic airflow. Then, I went ahead and created a similar config without IAT in the axis. This gave me a 1 row table similar to the Editor's bias table. (I'm not on the PC I used, but hopefully I can figure out how to upload attachments later). I'm not sure if anyone else had to make changes to their tables, but my AFR error was within -3% to +1% in the table. Outside temps were between 85-90*. From that, I don't think I have to make any changes to my original table.

[jimmyblue]

I propose you get the IAT out of the engine bay. If you do then
any error based on low-flow heating puts you rich and you trim
negative at the low end (better than a high-flow error making
you variably lean and untrimmed at the big end).

[knyght4]

I think I'm leave the IAT where it is. My problem now is that at idle or slow moving speeds, there's enough engine bay heat to get taken in by the intake. I can run my intake further down, but I want to fine a heat shield (which I've been trying to find) for my C5, and see if that makes a difference.

[S2H]

I propose you get the IAT out of the engine bay. If you do then
any error based on low-flow heating puts you rich and you trim
negative at the low end (better than a high-flow error making
you variably lean and untrimmed at the big end).

it depends on the car and the values on the table...
the 2001/2002 Fbody has a table that when IAT rises at lower airflows, the fueling goes lean...

as an experiment, I just tried moving my iat up to the front bumper...I have the plastic grill piece removed and have holes cut in the foam revealing holes in the bumper... my IAT is just above that metal hole. (if I was at home right now I would take a picture and post it...but I'm out on the road right now with Reba McEntire)

I get a slight heatsoak from engine bay heat when I sit still long enough...and it goes lean.. when I bring up my "0" cell in the bias table to double the current value (1.3~1.4 ish) it seems to do just fine in a heatsoak situation...and I dont have to touch the rest of the table.

I just happen to luck out with a car that the table works when I put the IAT in the bumper....other cars may not be as lucky and might have to make more changes to the bias table.

[WS6Fury]

heres the histogram I use..

be sure you log Dynamic Airflow in lbs/hr, and IAT in Fahrenheit

Can you save this off in an older format? I can't open it since I'm not running the beta, I'm still on the old version.

[WS6Fury]

so I tried to get the histogram right...dynamic air flow (PID) on x, IAT on the y, with the cells being populated by AFR....but I ended up with only 4 boxes....

I got the same thing. I'm lost, and don't have 2.23 beta.

[S2H]

heres some screen shots of how I have it set up on mine

[WS6Fury]

heres some screen shots of how I have it set up on mine

WOW 2.23 is completely different looking!!!!

I'll see if I can piece this together when I get home from work. Looks like you manually entered in the #'s for the x and y axis, is this correct?

[S2H]

yes...
there is no prebuilt table for this that you can load... so I manually entered the bias table values from my vehicle.

[WS6Fury]

ah ok that's the part I was missing then, thank you again so much!!

In regards to what you mentioned on the first page, adjusting the bias table, redo the VE table, then go logging again and do same thing over.

say you are running at IAT 90-100* and balance the VE table, at night you do a nother run and are at 60-70* and the AFR comes up rich by 10%. Would you not keep the VE table where it is, and just adjust the bias table accordingly to lean out the mixture?

haven't played with the bias table much so I'm just trying to better understand the method.

[Frost]

I am still adamantly in support of relocation of the IAT. It makes bias problems go away.

[Higgs Boson]

say you are running at IAT 90-100* and balance the VE table, at night you do a nother run and are at 60-70* and the AFR comes up rich by 10%. Would you not keep the VE table where it is, and just adjust the bias table accordingly to lean out the mixture?

because when the temps change again you will have to move that table again.

i have found a much more effective solution. leave your bias table stock, adjust your ve in avg temp weather, and then adjust your bias filter to slow the rate of change (at .3 g/s and below usually). this can slow or speed the rate at which fuel adjustment takes place. even if iat's get hot you can just make it take longer than a stoplight to lean out or richen up.

i also think iat's should be measured in the intake tract (not the bumper) but should be relocated to near the filter, which should be in the bumper area. i think iat/maf combo at the tb is not a good idea (maf by tb - good, iat by tb - not good).

measure iat's as far from the engine as you can, leave bias alone, adjust bias filter.

[S2H]

I am still adamantly in support of relocation of the IAT. It makes bias problems go away.

I've actually been playing with myself in my own car...
I just moved my IAT sensor up to the Bumper support, made a hole, mounted it with the grommet...
I actually have no front black plastic bumper cover, so it reveals the holes behind it...and I have cut holes in the foam there as well... allows in some cooler air, and also allows the cool air to get to my IAT now.

theres still some corrections that need to be done for when you come to a stop... but its only in the lower couple of cells in the bias table...

because when the temps change again you will have to move that table again.

i have found a much more effective solution. leave your bias table stock, adjust your ve in avg temp weather, and then adjust your bias filter to slow the rate of change (at .3 g/s and below usually). this can slow or speed the rate at which fuel adjustment takes place. even if iat's get hot you can just make it take longer than a stoplight to lean out or richen up.

i also think iat's should be measured in the intake tract (not the bumper) but should be relocated to near the filter, which should be in the bumper area. i think iat/maf combo at the tb is not a good idea (maf by tb - good, iat by tb - not good).

measure iat's as far from the engine as you can, leave bias alone, adjust bias filter.

moving the bias filter to a slower rate also means that its going to return to a slower point as well...not really a viable option
keeping the IAT in the intake tract is not always an option...some vehicles get horrible heat soak of the sensor no matter where you put it in the tract...even though the actual air flow moving thru is a much lower temperature....example of this being any GTO.