IAC Stepper Motor issues
Turbo Mini Forums

Just going through the final testing of the MS2 board before I get it finished, and have come to realise that while testing the IAC functionality, it's not working as intended.

The motor is a 4 pin bi-polar unit from a Peugot 106 1.1 I believe.

I have the stepper motor wired in through the JimStim, and all i can hear is the motor making a small prolonged buzzing sound each time i switch on the stim. I'm currently using a 9V battery which is bascailly new to power the stim.

I'm wondering if 9 volts is not enough to power the motor, or could something else be to blame?

Edited by Carl S on 11th May, 2010.

the stepper will consume quite a bit of current, I'm sure you'll need a proper battery on there.

those IAC steppers have 50 ohm windings, current = volts/ resistance so it will eat something like 1/4 of an amp at 12v and .2 of an amp at 9v, although they are PWM'd so it will be less than that,

still a fair bit though.

I should add that the pintle isnt moving at all.

I will try and get it on a car battery and try it again.

You definitely need more than a 9V battery. With the MS and the stepper motor, the total current draw will be well over 1A which the battery will not be able to provide. And it will probably last only a few seconds so will need replacing by now.

Jean

http://www.jbperf.com/

Best thing I've found to use on the JimStim to power everything is a PC PSU.

Just use the black/yellow feed, 12V stable and plenty of amps available - just put it through a fuse as the current available is very high so needs protection.

The PC PSU will drive anything you want to test.

Re the IACV itself, I found it was down to the settings in the msq to get it to work as expected. (I've used a Rover one).

Schrödinger's cat - so which one am I ???

Excellent idea Rod, I think I have an old PSU somewhere so will dig it out.

Thanks for the comments guys, I was hoping it was simply a power or settings issue and it sounds as if this is the case. (quite a contrast from what the MS site says, mentioning that the pintle will fly accross the room!)

With any supply that can provide more than 1A, be careful because that could melt traces if something is shorted.

So if you do use a PC power supply or a car battery, you should think about placing a 1A or 2A fuse inline with the supply. This is especially important when using a car battery because you could actually start a fire since it will provide over 100A if allowed.

Jean

http://www.jbperf.com/

As Jean says (I just said put it through a fuse....) mine is through a 2A one.

PC PSUs can provide very high current without you realising it but are a really good stable power supply if treated with respect.

BTW, my Rover IACV did send the pintle across the room a couple of times while I was testing it to find how it decided zero when out of the throttle body...

Schrödinger's cat - so which one am I ???

I've got an inline fuse holder handy so will wire something up with that.

Unfortunately my spare PSU is nowhere to be seen so i'll have to rig something up to my current PSU's supply.

Just use a spare molex on your current PC supply using the black/yellow but through a suitable fuse...

Schrödinger's cat - so which one am I ???

Yes that's the plan :)

Well i finally got the pintle moving after many hours of head scratching. When i first picked up the IACV, a lot of water came out of it, so I did wonder if this would affect it. I managed to get a supply from my PC's PSU in the end, wired in with a fuse.

The buzzing finally stopped and the motor gained enough strength to start moving the pintle. Looked inside and there was lot of gungey build up, so I don't know whether I should keep the unit or not.

Now the current issue is, I cannot stop the pintle from flying out the end of the unit. It seems there is no way of setting a base value for the starting position properly. I have tried setting the start position in the settings to numerous values, but whenever i switch on the stim, the pintle starts by moving outwards, and so if the coolant temperature was previously set to a very hot temperature (i.e at near to 0 steps), the pintle just falls out the end when you switch off the stim then turn it back on.

Is it a case of me having the motor wired in opposite to how it should be? I'm thinking this is not the case because I would have thought the pintle would be all the way out (fully extended) when the coolant is hottest, i.e letting the least amount of air flow in to the engine?

So far as I can tell - having been through this with a brand new one - when you power the MS up, it drives the pintle out until it hits a hard stop, then the CPU seems to sense the current change so recognises it's at "zero" and everything is re-calculated from that.

If there is no hard stop, the CPU doesn't know where "closed" is when powered up so just keeps driving it until it's shot out.

I proved this on the bench by taping the IACV down and hammering in a nail to limit it's outward movement and then everything worked fine on the JimStim.

Somewhere in one of my numerous posts, there is a piccy of it working that way.

Schrödinger's cat - so which one am I ???

Beginning of this thread, it was a screw I used on the bench though, not a nail...

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=295719

and in the piccy I was testing it connected to the engine inputs, not the JimStim...

Edited by Rod S on 12th May, 2010.

Schrödinger's cat - so which one am I ???

OK, thanks for that Rod. Hopefuly then, the IACV housing for the mini manifold will stop the pintle in time before it shoots out!

I will carry on testing this tomorrow.

In other news, I now have the carb and inlet manifold off the engine so that I can mark up the exhaust for the lambda bosses. Things are finally falling in to place.

Edited by Carl S on 12th May, 2010.