Air per cylinder Estimate random change?

[BigBoiMR2]

Hello,

I am tuning a 3sgte with a link G4+ Extreme PNP.

I am having a weird issue that happens occasionally, at the moment it only seems to happen on the first pull after warming up the engine, when the intake temps are still cold.

during the pull i could feel it sharply lose power a couple times in quick succession. Checking the logs showed the Injector duty cycle dropping sharply a couple times. the first drop seems to be from the accel enrichment turning off, but the second drop I can't figure out what is causing it.

I noticed that when the Duty cycle drops the second time I've noticed the "Air per cylinder Estimate" drops by half; the same as the injector dc. as far as I know that is calculated from the IAT and MAP, during this period those 2 values are consistent. Is there another value that could be affecting it?

Maybe there is something else obvious that I am overlooking.

I have attached the log file as well as my tune file.

Thanks,

Cameron

weird fuel issue cold pull.llg WIP Roadtune 3SGTE.pclr

[Adamw]

Yep, thats pretty weird for sure.  As far as I know the main inputs for the air mass calculation are MAP, charge temp, engine capacity, number of cylinders, VE & fuel charge cooling - and as you say all those appear to be (or should be) constant.

I have asked engineering to take a look in case there is some other factor I have missed but my initial feeling is it looks like possibly a firmware issue.  I will report back tomorrow.

[Adamw]

Hi Cameron,

Thanks to your good log engineering found the problem.  Here is an explanation from them what was happening:

"There is a problem in the charge temperature correction calculation in modelled fuel. When the charge temperature is close to zero the correction for the cooling effect of fuel could take it negative but it was stored as an unsigned number so became very large"

So its a combination of the zeros in that area of your charge temp estimate table and your very low IAT that showed up a problem that no one has noticed before.  I have a new firmware with this fixed for you to test.  I will PM that to you.

[BigBoiMR2]

Hi Adam

I appreciate your quick solution and clear explanation.

I will update the firmware and let you know if I have any more issues.

Thanks!

[BigBoiMR2]

On 3/7/2019 at 6:21 PM, Adamw said:

Hi Cameron,

Thanks to your good log engineering found the problem.  Here is an explanation from them what was happening:

"There is a problem in the charge temperature correction calculation in modelled fuel. When the charge temperature is close to zero the correction for the cooling effect of fuel could take it negative but it was stored as an unsigned number so became very large"

So its a combination of the zeros in that area of your charge temp estimate table and your very low IAT that showed up a problem that no one has noticed before.  I have a new firmware with this fixed for you to test.  I will PM that to you.

Hi Adam,

I've downloaded the updated PClink software, and the firmware that you have sent me. When I select the firmware after clicking browse I get this error. Firmware block size did not match file. 

I redownload the file from your link and got the same error again.

Thanks,

Cameron

[Adamw]

Hmm, are you using the latest PC Link, V5.6.6?

Edit:  I just tried myself and I get the same error.  It will have to wait till Monday now sorry.  

 

[BigBoiMR2]

Hi Adam,

Yes I installed the 5.6.6 pclink today.

No worries, it seems to be a minor issue as it only happens under those rare conditions.

If I put 1% in my charge correction table in place of 0 will that be a temporary solution also?

 

Thanks,

Cameron

[Adamw]

It was apparently my one drive that corrupted that file.  Im going to email you a new copy directly.