Xfi 2.0 question on lt1

Jeff Niceswanger · 06-30-2021, 07:36 AM

Like previously stated, if the car has an IAC ( Idle Air Control) on it you can adjust the throttle follower and try to help it. But an active IAC on a Superstock car is rare. I doubt you have one. Most of them are unplugged, blocked off, gutted or deactivated in the program. Its probably just a ill tuned map with the tune needing much more air than it should to idle, so the throttle body blades are opened way up, which in turn causes a sloppy return....
Make sure you don't have any type of vacuum leaks, especially at the map sensor or hose. Vacuum leaks play havoc with FI tunes...
You didn't mention whether is does this right after its been started, of after its warmed up and siting there running. If its right after a restart it is the After Start Enrichment and Decay rate,. Probably more so the Decay rate.

Kdw1403 · 07-01-2021, 09:02 PM

Anybody got a screenshot of a properly adjusted throttle follower? What is the proper way to adjust the throttle follower? Which way does what? Sorry to be so stupid.

Kdw1403 · 07-01-2021, 09:05 PM

It does it most all the time. Cold or warm. It’s a B-C/SA.

Kdw1403 · 07-01-2021, 09:07 PM

What is decay rate and what’s the proper way to adjust it.

KRatcliff · 07-01-2021, 10:10 PM

It sounds like you are using the IAC. Disconnect that sumbish. You don't need it and should solve your problem to allow the throttle body to simply close to your set idle point.

Pierce Jones · 07-02-2021, 12:44 PM

I was having similar issue last year with Holley HP and IAC controlling. I tried tuning decay etc. I couldn't get it to work well.

Thanks to posts on this site I finally unplugged the IAC this year. Much better returning to idle along with better idle quality.

L.Fite · 07-02-2021, 12:56 PM

So... I'm a carb guy, know zip about FI...
What exactly is the IAC supposed to be doing?
Is that similar to the Idle control that was to up the idle when the A/C was on, back in the carburetor days?
Or something else.

Always curious about how things work.

KRatcliff · 07-02-2021, 01:04 PM

Quote:

Originally Posted by L.Fite

So... I'm a carb guy, know zip about FI...
What exactly is the IAC supposed to be doing?
Is that similar to the Idle control that was to up the idle when the A/C was on, back in the carburetor days?
Or something else.

Always curious about how things work.

That is it pretty much and why we can disconnect them.

Kdw1403 · 07-02-2021, 05:56 PM

Will disconnecting the IAC hurt the performance performance of ET or MPH?

pmrphil · 07-02-2021, 01:12 PM

Quote:

Originally Posted by L.Fite

So... I'm a carb guy, know zip about FI...
What exactly is the IAC supposed to be doing?
Is that similar to the Idle control that was to up the idle when the A/C was on, back in the carburetor days?
Or something else.

Always curious about how things work.

Idle Air Control - it's a computer controlled (sometimes poorly) air leak into the intake that a race car doesn't normally need.

06-30-2021, 07:36 AM	#1
Jeff Niceswanger Senior Member Join Date: Jul 2003 Posts: 894 Likes: 687 Liked 1,034 Times in 368 Posts	Re: Xfi 2.0 question on lt1 Like previously stated, if the car has an IAC ( Idle Air Control) on it you can adjust the throttle follower and try to help it. But an active IAC on a Superstock car is rare. I doubt you have one. Most of them are unplugged, blocked off, gutted or deactivated in the program. Its probably just a ill tuned map with the tune needing much more air than it should to idle, so the throttle body blades are opened way up, which in turn causes a sloppy return.... Make sure you don't have any type of vacuum leaks, especially at the map sensor or hose. Vacuum leaks play havoc with FI tunes... You didn't mention whether is does this right after its been started, of after its warmed up and siting there running. If its right after a restart it is the After Start Enrichment and Decay rate,. Probably more so the Decay rate. __________________ Jeff Niceswanger 3740 SS Last edited by Jeff Niceswanger; 06-30-2021 at 04:30 PM.

07-01-2021, 09:02 PM	#2
Kdw1403 Member Join Date: Nov 2016 Posts: 209 Likes: 49 Liked 68 Times in 22 Posts	Re: Xfi 2.0 question on lt1 Anybody got a screenshot of a properly adjusted throttle follower? What is the proper way to adjust the throttle follower? Which way does what? Sorry to be so stupid.

07-01-2021, 09:05 PM	#3
Kdw1403 Member Join Date: Nov 2016 Posts: 209 Likes: 49 Liked 68 Times in 22 Posts	Re: Xfi 2.0 question on lt1 It does it most all the time. Cold or warm. It’s a B-C/SA.

07-01-2021, 09:07 PM	#4
Kdw1403 Member Join Date: Nov 2016 Posts: 209 Likes: 49 Liked 68 Times in 22 Posts	Re: Xfi 2.0 question on lt1 What is decay rate and what’s the proper way to adjust it.

07-01-2021, 10:10 PM	#5
KRatcliff Senior Member Join Date: Sep 2011 Posts: 769 Likes: 75 Liked 534 Times in 143 Posts	Re: Xfi 2.0 question on lt1 It sounds like you are using the IAC. Disconnect that sumbish. You don't need it and should solve your problem to allow the throttle body to simply close to your set idle point.

07-02-2021, 12:44 PM	#6
Pierce Jones Junior Member Join Date: Aug 2013 Location: Chatham, ON. Canada Posts: 19 Likes: 15 Liked 15 Times in 9 Posts	Re: Xfi 2.0 question on lt1 I was having similar issue last year with Holley HP and IAC controlling. I tried tuning decay etc. I couldn't get it to work well. Thanks to posts on this site I finally unplugged the IAC this year. Much better returning to idle along with better idle quality. __________________ Pierce Jones 1995 Camaro D/S #3102

07-02-2021, 12:56 PM	#7
L.Fite Senior Member Join Date: May 2020 Posts: 517 Likes: 559 Liked 497 Times in 243 Posts	Re: Xfi 2.0 question on lt1 So... I'm a carb guy, know zip about FI... What exactly is the IAC supposed to be doing? Is that similar to the Idle control that was to up the idle when the A/C was on, back in the carburetor days? Or something else. Always curious about how things work.

07-02-2021, 05:56 PM	#9
Kdw1403 Member Join Date: Nov 2016 Posts: 209 Likes: 49 Liked 68 Times in 22 Posts	Re: Xfi 2.0 question on lt1 Will disconnecting the IAC hurt the performance performance of ET or MPH?