RCinXS

I'm adding a AIC to my Supercharged 1984 16V. Has 85 TB, Air Guide, etc., attached to the original Spider Plenum.

I'm not using the stock 3 wire 85 Idle Control Valve. Using a 4 wire GM stepper and aftermarket valve.

Air Output from the Aftermarket valve to the original loaction in the Air Guide.

I know that on NA cars the valve would be attached to the Plenum to use filtered incomming air.

When adding a Air Idle Control valve to a supercharged 928, should the air input side of the valve be routed from the Plenum or before the Supercharger in the Flitered air stream?

Concerned about adverse effects of boost to the IAC valve.

Any advice or opinions would be appreciated.

John Speake

I would take it to atmo via a suitable small filter.

123quattro

I would put it post supercharger. On my Audi I had the problem of blowing the IAC open at high boost and it becoming a leak when vented to atmosphere. This could cause more of a problem since you are MAF based.

RCinXS

Thanks for the responses. I should have stated that I am MAP based.

123quattro, Your description indicates the condition that I am concerned with. But perhaps you meant to say Pre supercharger? There would be no boost before (Pre) the supercharger.

John S., I think I like the idea of pulling from atmosphere. Would probably have more consistant flow.

I believe the main reason they are usually hooked up to the Intake Plenum is that the air is already filtered, and to bury the slight noise they make sucking air.

Unless matching air temperature is also a concern.

Car does have an intercooler. So Plenum air will always be quite a bit colder than atmosphere.

Air Temperature Sensor will always read colder than atmosphere too.

I'm probably just overthinking this and should just hook it up and see what happens.

Lizard928

It needs to have one side routed between the valves and throttle body, the other side needs to be between throttle body, and SC.

The reason is that if it is before the SC (sees no boost), then it will bleed boost off while under boost.

where as if both sides are pressurized you will not have any loss.

Imo000

So one side would be pressurised at the valve cover by the crancase blowby and the other, by the SC throught the boost pipe?

928mac

I am not super charged but I have already converted to a MAP (Mass Air Pressure) and a MAT Sensor (Mass Air Temp)
Well its not complete yet

Lizard928

Imre,

This valve is simply for controlling the Idle Air Control. In other words, an idle control valve. This has absolutely nothing to do with crankcase pressure.

Brad,
You are going to be running Tec GT. Most members need to be aware that the stock engine management is not able to be converted at this time.

Imo000

Yup, I understand. I was just trying to picture what you were explaining with the re routing of the idle air control motor. I have been chasing a weird off throttle idle problem for a while but I'm not sure if it's a faulty valve (have replaced it with a spare with no change) or if it need to be re routed because of the supercharger.

RCinXS

All that I was worried about was adverse effects of the boost on the valve and stepper motor.

However, during discussions, it has been realized that in effect there is no real force to be concerned with on the valve other than the minimal residual boost within the plenum while under boost.

There will only be a slight pressure differential, if any, between the Plenum and the Air Guide under boost.

My thanks to Lizard931 and all others who responded to my quandry.

So far as hunting for an idle, the stock Bosch Idle Control valve's motor is notorious for causing problems.

I think PorKen had a write up on it some time ago.

RCinXS

Found the link. https://rennlist.com/forums/928-foru...alve-wear.html