I'm having a very productive morning at work..... So I'm sitting here pondering if the idle speed control valve (when controlled by the stock ecu) returns to a closed position during normal driving?

I know that on my Autronic ECU with TPS Follower turned on it sits fully open so that when you lift off and the revs begin to drop it moves to maintain a stable speed that gradually bleeds off at a predetermined rate to provide smoother driving approaching lights, crawling in traffic etc, at the same time it keeps the injectors running to negate engine braking, it does cause a bit of popping and banging from the exhaust but overall does a very good job of smoothing things out. Now I'm thinking with how much the stock ecu pops and bangs on over-run.

So I guess what I'm trying to determine is whether or not the stock ecu does actually do the same thing, because basically the downside of this feature is that the valve stays open during normal driving even when on boost, therefore providing a direct leak path for the pressurised air within the throttle-body/plenum to escape to atmosphere through the valve. This must effect the boost threshold/spool rate of the turbo.

For my ECU I'm setting up a 'general purpose control' to close the valve above a certain rpm/boost point, however things aren't so simple with the stock ecu, perhaps a one way valve in the air supply going to the ISCV?

Ah good, it's nearly lunchtime.

i don't know for sure but an educated guess.....
I believe it's closed until it sees the throttle fully closed

When I did the rebuild I took the TB apart and despite using alignment marks it wasn't reporting the throttle closed. The idle was terrible hunting all over but mostly at lower than stock rpm. A tweak of the TPS solved it and the car idles perfect. This makes me believe it's inactive when the throttle closed signal isn't working

Looks like someone's got to go for a drive with a multimeter in the car

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If at first you don't suck seed, try drier grain.

Good lad, off ya go!

Got to weld my seat up first. Back broke again. I'd hate to have an accident in it when it can't take normal driving. At least the 185 was well made.

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If at first you don't suck seed, try drier grain.

Well you need to stop driving around with it reclined at 60 degrees in a 'pimp-dawg' stylee with your windows down and system pumpin.

shock undercover photos of Chris, hot of the Hello magazine press

St185 ecu closes it if the idl contact on the tps is not saying you've got throttle open. I'd bet the st205 is the same.

This is until rev drop into the 620 to 1200 rpm range, then it will open it.

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Darryl

Cheers Darryl!