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Is this the ISV?

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barks944

New member
Ive been puzzling lately over what the electrical device with a two pin plug under the manifold of my two early 944 engines is. There are some pictures if you follow the link below. I can only think that it is an ISV but I didnt think the early engines had them. They certainly dont have the pins needed for an ISV listed on http://www.the944.com/connector.htm for the late model cars with the ISV. The connector just has blank holes.

http://picasaweb.google.co.uk/tomspics1234/944ISV#
 
It is the ISV a simple version and I would prefer it to the 3 wire valve on the later cars as I believe would easily work with my setup.
 
Don't take my word for this but from what is visible it resembles an Auxillary Air Valve. It is supplied with power when the engine is cold and the two pins are the ends of a coil which heats a bimetallic strip and gradually shuts the valve. The pipe going into the back of it is in just the right place and there should be another one coming out the front. Don't take my word for this however because the whole thing would need to be visible to be sure.
 
That would make sense as it is not connected to the DME but I'm sure it allows air to bypss the throttle body. Anyone know how it is wired up? Is it just a temperature switched 12v feed?
 
I've got a couple of manuals with electrical schematics in them, i'll endevour to have a look when i get home. You're probably right about it not being connected to the ECU because the same valve is fitted to K-Jet engines which don't have management. If you suspect it's not working there's some tests you can do on the thing itself and the supply to it.
 
ORIGINAL: mr brightside

Don't take my word for this but from what is visible it resembles an Auxillary Air Valve. It is supplied with power when the engine is cold and the two pins are the ends of a coil which heats a bimetallic strip and gradually shuts the valve. The pipe going into the back of it is in just the right place and there should be another one coming out the front. Don't take my word for this however because the whole thing would need to be visible to be sure.
Click to expand...


Thats what I would have said if I hadn't had a beer or two.



Some people have been using an auxiliary air regulator for fast idle control. SAAB, VW, and many other European vehicles used this system on their early EFI systems (D-jetronic) and on their mechanical injection system (CIS). The great thing about this system is that it does not need to connect to MegaSquirt® at all. You just hook up 12 volt, ignition switched, and you are ready to run. Use 12 volts from the fuel pump relay. If the engine is not actually running you do not want it powered up, as it will move to the 'warm' position even though the engine isn't running.





Mount the regulator to the engine such that engine heat can keep the valve closed when you do not need any additional air for warmup. During cold starts, the auxiliary air valve opens to allow additional air into the inlet duct. As engine heats up, a bi-metallic element expands and closes valve. At approximately 140°F (80°C) the auxiliary air orifice is completely closed by the valve.


Shamelssly copied from a manual.
 
Checked the supply voltage just now and it raises to 13v after the engines been on for a bit. Nothing changes though so I think its likely that it is permanetly open.
 
JamesO said it all really, it's fed from the fuel pump relay via 16a fuse 2 on the additional fuse board. The raise in voltage you noted suggests the heating coil is intact, a drop in voltage would be observed initially due to the coil heating up and once it's warm the current would probably decrease resulting in a small voltage rise. To see if it's stuck open you'd really need to look down one of the holes at cold and then warm engine temperatures, may i suggest a dentists' mirror for that cos it's in a really inconvenient spot.
 
Should the supply voltage be about 12v from the start, mine sat at 0v for about a minute then jumped to 13v and then was a little skittish and dropped to about 4v now and again. This was just measuring across the plug with a voltmeter, the plug was disconnected.

From what you are saying there should be voltage across the coil as soon as the engine starts and the coil then runs hot while the engine is on.
 
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