Working Cold Start and Idle Control for 20vt swaps! How to Guide!

Hi,

I have successfully fitted my mk2 20vt conversion with the Idle Control valve and control box from the old 16v KR engine. It has solved all my cold start issues and holds the idle at 1k rpm at all times.

It will now start from cold from on the key, or now the remote start which is why i did it!
When it is very cold, it will idle at 1500rpm for the first 20sec or so at start but then will hold it at 1000rpm no matter how many accessories you switch on.

It also stops it stalling when the throttle snaps shut quickly by opening as the revs drop past 1500 back and softens the landing down to 1000rpm.

Here's a very comprehensive how to!

Put the idle control box back behind the centre console and run all the wiring back how it was fitted on the KR back to the fusebox area and then out to the engine bay.

The idle control box has the following connections:

Black - connects to thin black wire behind fuse box wihch is ignition live

Brown/White - connects to thin brown/white wire behind fusebox which is sensors ground

White - ISV Motor goes out to engine bay
White/Black - ISV Motor goes out to engine bay

Green - Unused on UK models (I want to know if this is for increasing idle speed when you switch aircon etc on. anyone know?)

Black/Yellow - There are two of these that come out the ISV Control box. Connect either one to one side of the throttle microswitch (on when throttle closed). Cut the other one off.

Throttle microswitch, connect one side to ignition live and the other side to one of the Black/Yellow wires from the control box. If you run a MK3 throttle body then you can use the old cold start valve plug or WUR plugs as these are the same.

Black/Red RPM Wire
If you are driving the original MK2 cluster with a "3 diodes circuit" from your coilpacks then connect it to this. If you are using the output of your new ecu to drive the clocks then you will need to build a "3 diodes circuit" (google it) to combine your coilpack signals so that the control box senses the right RPM.

Green/Red - Temp.
Originally connected to single pin temp sender in side of 16v head. I couldn't find anywhere to put that sender in the 20vt so instead i used an additional 8v temperature sender (the black one) which is identical to the one used to drive the cluster and put it in an inline hose joiner which i think is fitted to some diesel golfs. Connect the other side of the sensor to the Brown/White sensor ground wire.

Brown/Black - Originally connected to overrun valve. unused, cut it off!

ISV Air connections
Get some silicone pipe bits from http://www.sfsperformance.co.uk/
Plumb the input to the ISV which is on the END of the valve, to the spare air port on the main rubber turbo intake pipe. It is just after where the diverter valve dumps it's air back in and is probably blanked off as it was originally used for the carbon canister/egt system.

Plumb the output of the ISV which is on the SIDE of the valve to a spare air port somewhere after the throttle butterfly. My MK3 8v throttle body has a spare 10mm port in the body so I used this.

I am unsure as to whether the ISV will stay fully closed on boost or whether it will leak air back into the inlet. If this happens I will fit a one way valve into the pipe between the ISV and the throttle body to stop boost getting back to the ISV. I got the one way valve with 10mm inputs from the brake servo pipe in a late model vw in the breakers. I didn't want to fit it if i didn't need it as it would restrict the air available to the idle system.

There you go, Good luck!

Oli.

 

interesting thread matey, what management system are you using? on my 20vt using i am using megasquirt programed to run a digi 8v isv using a pwm circuit incorperated into the ecu that also works quite well

Yours does sound like an easy route for cold start on any standalone ecu without the need for as much trial and error, good work

 

Mine runs DTA which is supposed to be able to drive the ISV directly but doesn't.

Nobody on the DTA forum has got it working properly.

This was a nice easy swap because the little VDO controller box is already programmed to operate the 16v ISV and after all the engines are almost the same bar the turbo!

Better than the MK1 Aux Air Valve which won't stabilises idle when you turn the main beams and heater on as well when the throttle snaps shut from high revs.

Oli.

 

The ISCV ground, should go to approx 0% duty if the idle switch goes to open and the RPM goes over a certain threshold. So you should be alright when on boost. Of course you can always test and see.
It is good you have written about this as I was going to experiemnt into doing this.

 

cold start whats that lol

ive also found if you send a 12v feed to the stepper motor on the 20vt agu tb it acts as a cold start and i got this info from the nutter in the thread below this guy is the man i helped him over a year ago with different things and he sent me a link to his website enjoy

http://rush.smolly.nl/changes/change4_2.htm

 

wow!,very nice.now i know what the pins are,just got to figure out where to conect the wires,im not using ms,im using dta

 

That's great, but since the AGU TB is a stepper motor and the DTA ISV control circuit is PWM for a solenoid valve you'd only get full open or full closed.

This would be ok for starting, but you'd have to use a switch on the dash or find another way of turning it off when the engine got warm, otherwise the revs would shoot up to 3k everytime the DTA sensed the revs dropping past 1k and it opened the valve.

To make it work properly you would need to build a stepper motor drive circuit to drive the Tb from the PWM signal the DTA outputs. This would be a very neat option, but I don't know how to build one, and i had all the old ISV stuff kicking around which is a proven solution for the 16v engine and needs no fiddling with Duty cycle and Control Loop function s to make it work!

Now I just need to find a slightly bigger port on the intake and inlet manifolds to plumb it to so that it gets slightly more air through for very cold starts.

Oli.

 

Oli

Which DTA are you using?

 

i'm running E48EXP which has no idle control duty cycle map.

the later DTA ecus have a separate map for idle control and i believe they can run the ISV properly. I don't think they have stepper motor control though.

Oli.

 

Ok mate

Going to do this on my S80 DTA 16vt once i get the rallye back