- Sun Jan 09, 2022 9:23 am
#127203
I have only known the S3 set up which uses an adjustable throttle bypass port (ie screw) in which stock idle is set and AFR manipulated with MAF adjustment.
I don’t think later 928’s do it this way and I don’t think earlier models do either?
My current project involves VEMS conversion with a S4 IAC for “simplicity” ;).
What I’m getting into is the throttle bypass port has the ability to override the IAC until higher duty cycles( percentage of open IAC valve). Meaning finer adjustment of IAC don’t move the rpms around at idle. For background, the software lets you “lock” IAC at any given opening or duty cycle. This in turn should adjust idle speed.
Because of the SC I have to assume the forced induction is a factor here as well, even with a BOV I’m sure bypass port gets more air then designed.
So what am I really achieving?
The idle screw is an IAC right? Just manually set.
The actual IAC, I assume is to deliver or not deliver additional air for fine tuning at different engine demands correct?
I guess the point is how hard do I have to try to perfectly manage this bastardized IAC if current idle rpm is fine and car doesn’t stumble after throttle blips?
I can close the port and rely on IAC exclusively, and is that essentially how the S4 would do it?
Opinions please.
I don’t think later 928’s do it this way and I don’t think earlier models do either?
My current project involves VEMS conversion with a S4 IAC for “simplicity” ;).
What I’m getting into is the throttle bypass port has the ability to override the IAC until higher duty cycles( percentage of open IAC valve). Meaning finer adjustment of IAC don’t move the rpms around at idle. For background, the software lets you “lock” IAC at any given opening or duty cycle. This in turn should adjust idle speed.
Because of the SC I have to assume the forced induction is a factor here as well, even with a BOV I’m sure bypass port gets more air then designed.
So what am I really achieving?
The idle screw is an IAC right? Just manually set.
The actual IAC, I assume is to deliver or not deliver additional air for fine tuning at different engine demands correct?
I guess the point is how hard do I have to try to perfectly manage this bastardized IAC if current idle rpm is fine and car doesn’t stumble after throttle blips?
I can close the port and rely on IAC exclusively, and is that essentially how the S4 would do it?
Opinions please.
Devolved 86.5 Track car
Manual w/LS
DIY Supercharger
Manual w/LS
DIY Supercharger