PWM Idle Speed Control Valve

[TheDarkRaver]

Hey All,

So I went down to Pick'n'Payless today to find a Ford Falcon XF ISCV to use on my 7MGTE with a Wolf3d V4 (as this will only operate a PWM (Pulse Width Modulated) ISCv (Idle Speed Contol Valve) and I have heard the XF ISCV is the way to go.. Now I couldnt find any XF's with them still attatched BUT then I remembered reading a while back that some Hyunda's had the large bosch ISCV's which were PWM.. So off I went and found that indeed the Excels along with their plastic planum do use a bosch ISCV like this one..



So I decided to grab it as it has two barb type fittings which will be easy to attatch some hose to and fit up..

Now this brings me to my question, the ISCV has three wires on it which I am assuming are 12v-Ground-PWM is this likely to be correct? and if so how can I safely find out which one is which? Once I figure out which is which I am assuming I can just connect 12v+ --- Ground --- and the PWM wire to my wolf? is this correct?

Thanks to any help anyone can give me.. And if this works I think this is a very good CHEAP solution to the ISCV problem alot of people have with aftermarket ECU's..

Marc,

[CrUZida]

Just thinking out loud here, but aren't the XF ISCV's only 2 wire ?

FWIW I'm using a 20V 4AGE ISCV (3-wire) and thats PWM-12v-PWM, ie no ground connection.

[TheDarkRaver]

Yes the XF ISCV's are 2 wire and are different to the bosch unit i picked up..

That would make more sense as the PWM act's as ground anyway doesnt it?

I have tried searching the bosch part number and tracking down excel wiring diagrams but no luck yet..

Just hoping it does not turn out to just be some sort of 3 pole stepper motor as I know some of the bosch units are..

[MWP]

How much was it from the wrecker?
If it was cheap enough, maybe buy a second one and break it open?

[thechuckster]

This might help ...

edit: these are PWM devices.

From the MSextra manual:

3 Wired Bosch Valves (0280 140 505)
The bosch valves can also be made to work via the FIdle output, these need the transistor mod as above and they need to be wired as the diagram below. The centre pin goes to +12V, one of the other 2 pins will hold the valve shut when its connected to ground (0V). This pin needs to go to earth via the resistor, the other pin goes to the FIdle output on the DB37 connector.

On a 3 wired valve there are effectively 2 windings that fight against each other, one opens the other closes it. So we put a resistor in line to ground with one winding, this shuts (or opens it depending on what winding you use) the valve, so its like having a spring holding it one way. The MS ECU then forces it either shut or open, it can do this as the resistor in the other winding limits how much it can force it one way.]

[TheDarkRaver]

Excellent thanks heaps for that chuck, is exaclly what I was looking for some type of diagram!

Looks like it will do the job for what I need, will follow up and let everyone know how I go..

Marc,

[TheDarkRaver]

Ok, so after going to jaycar today to pick up a resistor and a diode it occured to me that a 50W resistor seems rather large, plus the highest wattage I could find on the shelfs was 10W..

So I put the question to anyone with a bit of electrical knowledge what they would suggest to use, or does 50W sound correct for this application? (or should it infact be a 5W resistor and they have just miss typed it?)

Marc,

[-Totenkopf-]

That seems like a rather half arse way to control the valve, generally two PWN outputs would be used to control the position. Using the method of one PWN and then a steady voltage to the other coil would probably make it a little slower to respond and what not then normal.

Doing some quick calculations on the ohm value of the resistor they gave you tends to make me think its a 5W resistor.

V=IR -> I=V/R P=VI -> P=V^2/R

Say V = 12 and R = 35 gives us a power consumption of around 4.1W

[TERRA Operative]

Although a 10w won't hurt at all. Bit of extra headroom.

[thechuckster]

I've never used the above diagram - it just comes from the msextra online manual.

-Totenkopf-: they suggest wiring it up that way as the ECU (like many aftermarket ECUs) only has one PWM output for idle control.

[TheDarkRaver]

Well I had a little play yesterday and just sat the valve in the engine bay and hooked it up with the 5w resistor to see if it worked.. And I can report back that it works perfectly, I change the PWM idle position all the way from 0% to 100% on the ECU and it opend and closed fine. It also seems alot quieter than the XF (2 wire - spring type valves) aswell..

I then hooked it up temp on the engine with some pipe, to make sure with a vaccum load that it still operated fine and it did what it was supposed to fine.. The only thing is the resistor gets very hott (wouldnt be able to touch for longer than a second), but this is fairly normal for this type of large resistor isnt it?

[TERRA Operative]

Yea, it'll get hot.

You can get ones with an inbuilt metal heatsink (the resistor is inside a finned aluminium tube) and or go to a higher wattage too.