Low Idle Airflow numbers

[2003SilvSS]

I'm using the Idle airflow Config. Could someone tell my why my Base Running Airflow> Idle Airflow numbers are so low. I look at other tunes and their numbers are so much higher. Sometimes double.
Am I doing something wrong? I want to make sure I have an accurate starting point for my idle tuning.
Attached is the tune set up for idle airflow tuning and my log.
Thank you and Happy 4th!!

My SD 80lb inj. BRA.hpt <<<<Tune
7-4 idle airflow in gear.hpl <<<<Log

[mecanicman]

You have a vacuum leak somewhere.

[2003SilvSS]

Thanks for the reply.
Is there anything else that may cause this before I go tearing things apart looking for a vacuum leak? All of my hoses and connections seem to be fine.

[owens1]

Low desired airflow can be caused by large hole in throttle blade, or iac vs effective area table may need to be adjusted, especially if it has a larger TB.

[mowton]

Assume it the truck in your signature. Do you have a vacumn referenced fuel system (1:1)? The tune says you possibly do as the IFR is flatlined yet the offset table is not? What is your idle fuel pressure? If all that is ok then it must be a sneak path of air somewhere's and a hole in the TB or check around intake manifold with a propane torch are easy tests. I don't think its a hole in TB plate as that would be metered air and taken into consideration..... the TP% would be low though.

Ed M

[2003SilvSS]

It is the truck in my sig. I'll try the propane trick. It's a DBW TB. I do have a hole drilled in the blade.
My IAC steps vs Effective area is set with stock values. What should that be set at for the 102mm TB? Should the whole table be raised by a percent?
I do have a vacuum reference fuel pressure regulator. Should the offset table be flat also? My idle fuel pressure is 53 psi.
I have the MAF fail set to 0 in this tune. Is that a problem?
Thanks for the help.

[mowton]

It is the truck in my sig. I'll try the propane trick. It's a DBW TB. I do have a hole drilled in the blade.
My IAC steps vs Effective area is set with stock values. What should that be set at for the 102mm TB? Should the whole table be raised by a percent?
I do have a vacuum reference fuel pressure regulator. Should the offset table be flat also? My idle fuel pressure is 53 psi.
I have the MAF fail set to 0 in this tune. Is that a problem?
Thanks for the help.

If its a DBW then there shouldn't be a hole in the throttle plate, electronic throttle control (ETC) will handle the opening and closing and closed throttle shouldnt be a problem like with DBC. Also set up has an ETC, and not an IAC idle control, so the ETC Scalar s/b changed from the stock .0255 to .0149. All the idle tuning will need to be redone, especially the RAF. The PCM will use this value to convert the mm2 idle desired air into the TPS%.

In a DBC systems, they use the mm2 value and the effective area table you discussed to find the step count. As the stock TB was a 78mm, it provided approximately 12 mm2 of area in the closed throttle position. That is why 0-12 all are 0 steps. By adding the 102, I would shift the table from the 12 mm2 starting position to 20-22, again if you were running DBC.

Where is you TPS% at idle? I personally would close the hole in the throttle plate unless there is a good reason to put it there...the cam isnt that big.

Yes, the offset table should be flatlined as well. Thats not going to bother you that much but just needs to be corrected.

When you say MAF failed at 0 does that mean you are tuning the VE or intend to run in Speed Density? Along with the MAF failed at 0, do you have DTC's P0101-103 set to fail on first error?

Ed M

[2003SilvSS]

I'll make these changes probably tomorrow evening. This is a SD tune. My codes were set to MIL on second error. I'll close the whole in the TB. Any suggestions how to close it? My tune does have an IAC step vs. Effective area table. I guess it's not being used in this tune? To flatten the Offset table, do I use the value in the 0 vacuum column and copy it across each volts row?
TPS% is around 8% +/- at idle.
Thank you for the help.

[mowton]

I'll make these changes probably tomorrow evening. This is a SD tune. My codes were set to MIL on second error. I'll close the whole in the TB. Any suggestions how to close it? My tune does have an IAC step vs. Effective area table. I guess it's not being used in this tune? To flatten the Offset table, do I use the value in the 0 vacuum column and copy it across each volts row?
TPS% is around 8% +/- at idle.
Thank you for the help.

You can close it with JB Weld. I have used pop rivets in the past, but actually had one come loose (think it was undersized) and was ingested by the motor during a dyno pull.....now I exclusively use JB Weld :-) Thankfully no damage...

Yes copy the 0 kPa columns all the way across.

As far as the DTC, I also set the High RPM disable to 8000 (enable to 7900 if you have it) just to be sure also.

All tunes have both IAC table and ETC scalar table. The Operating System is coded to handle which of the two it uses. If you look in the Systems Tab, you wil see an ETC column for defining what each specific setup has. Even some of the PCMs have both drivers in them (would have to go back nd find my notes) so you can use them in swaps...

Your welcome,

Ed M

[2003SilvSS]

I couldn't find any vacuum leaks. I closed the hole in the TB blade, Set p0101-p0103 to MIL on first error(because this is a SD tune), set ETC scalar to .0149(for 102mm TB), and flattened the injector offset table(for vacuum reference FPR). Also, I set the Idle Airflow numbers to stock. The stock numbers were around double what I was coming up with. After running the Idle airflow config with these changes, the numbers were even lower. With this config I'm logging actual airflow numbers not error correct?? I'll attach the latest log and the tune with the changes.
Thanks,
Mike
My SD 80lb inj. BRA 2.hpt <<<<<<<TUNE
idle air log 7-12.hpl <<<<<<<LOG

[mowton]

I couldn't find any vacuum leaks. I closed the hole in the TB blade, Set p0101-p0103 to MIL on first error(because this is a SD tune), set ETC scalar to .0149(for 102mm TB), and flattened the injector offset table(for vacuum reference FPR). Also, I set the Idle Airflow numbers to stock. The stock numbers were around double what I was coming up with. After running the Idle airflow config with these changes, the numbers were even lower. With this config I'm logging actual airflow numbers not error correct?? I'll attach the latest log and the tune with the changes.
Thanks,
Mike


My SD 80lb inj. BRA 2.hpt <<<<<<<TUNE
idle air log 7-12.hpl <<<<<<<LOG

Yes those are the values that get pasted into the BRAF....

If there are no vacumn leaks or sneak paths then the Idle desired and TPS% are ok in my book...

Ed M

[2003SilvSS]

Correction to my last post.
I was reading the last log in Lb/min... oops. My numbers are actually greatly improved with the adjustments you gave me, Ed.
Thank you again