6.0-928S

Does ALL of the air the motor uses at idle go through the ISC motor or does some go through the throttle plate? (on an S4)

Thanks, Hammer

Jack Riffle

According to my Bosch Fuel Injection and Engine Management Book, it appears that most but not all the air the engine takes in at IDLE is controlled by the ISC which actually allows air to bypass the closed throttle as the engine requires. It does appear that a very small amount is going across the throttle plate at an idle.

AO

The idle plate is not 100% air tight (like Jack said), but it is closed fully. So for all intents and purposes, yes, all the air for idle passes through the idle stabalizer valve.

6.0-928S

The reason I ask. I'm using the factory ECU's with my ITB setup & am trying to determine if I need to make the feed lines from the ISC motor to the ports larger. They're only 1/8 inch lines. If I can get the majority of my idle air by adjusting the throttle plates & have the ISC for fine tuning I'll be ok. If not I'll have to provide larger feeds.

Hammer

6.0-928S

That explains my question.
I researched it & I saw no reason that it couldn't be done.

Hammer