16 valve throttle body wiring

[dude]

I am fitting a 1800cc 16valve kr engine into a MK2 golf gti that previously had an 8Valve digifant.

I have noticed that on the bottom of the throttle body of the 16v engine there is a switch. This is apparently thethrottle valve switch.

Does anyone know what exactly this does?
As I dont seem to have the wiring for it in the 16valve ECU loom that I have fitted.
Do I need to have it connected, and what exactly does it do...even if not needed?

[Conker]

It tells the idle system to go into idle mode e.g. the ISV starts to control the revs. This switch going wrong is probably one of the most common causes of a "hunting idle", and so I think you will definitely need it, presuming you are putting in the K-Jet management.

[dude]

Thanks for helping.

The engine is going to be in a rally car.
Therefore Id like to do away with as many wires as possible that are not essential.

Does this switch have any affect on advancing the ignition timing?
Or is it just for cold start running?
When the engine is upto working temperature does it become redundant?

[Conker]

Someone else will know for sure, but in the meantime...

IIRC... Advance is very simply controlled by the ECU detecting engine revs through the dizzy, which it then advances as revs increase. Its a very basic [but functional] system. The idle switch is needed all the time, even when hot, to maintain a steady idle - Cold running is a separate system primarily affected by the WUR, thermotime switch and 5th injector.

[rubjonny]

please see your other post for what the switch does and how it works:
http://www.golfgtiforum.co.uk/index.php?topic=100089.0

In addition the ECU will continue to advance the timing as normal as it only gets a signal from the switch when its closed.  However you might struggle to get it to idle, especially without the ISV system.  But several MK1 boys have got away without the ISV setup by increasing the idle a wee bit, apparenly it doesnt like to idle from cold but it clears up when hot.  However I dont know if the ide switch was present in this case or not.  If it was me I'd run it, its only 1 wire to the ign controller and another to an ign live source.  You'll get rid of a fair chunk of wires & hoses by binning off the ISV system alone.