Does anyone know the size and spring rates for the springs inside the OM603 vacuum control valve?

As far as I can tell, the valve adjusts vacuum from ~10in HG to zero as throttle position increases. I'd like to increase that to ~20in HG to zero. I'm hoping I can get there by installing a stiffer spring.

Thanks.

EDIT: I'm not using the VCV for its normal purpose. I'm using it to help control a variable vane turbo.

I don't think you can do it that way. I think the max pressure is dependent on the size of the inlet orifice.

Is there any particular reason for doing this "mod"? If your vacuum lines are routed properly and the blue UFO is doing its job, there's no reason to need "more" vacuum, it won't do anything to the transmission since the modulator is designed for a maximum vacuum tuned to the system supplying it.

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I'm not using the VCV to control the transmission. I'm using it to control a variable vane turbo. ~20in HG would be much more useful than 10.

A couple of things you might try:

- The VCV from a 190D Turbo uses a larger orifice. It can be identified because it has a blue top. I discovered this when my VCV began leaking and I tried replacing it with one from a 603.

- You can try using a BUFO to amplify the vacuum signal. I've not measured this, but I'm pretty sure the BUFO's output is higher than the VCV signal.

- You may have a leak somewhere. Here's a 603 VCV connected directly to my vacuum pump. As you can see, the at-rest vacuum is around 15:

https://www.youtube.com/watch?v=WZzY6t2InrY

- Check the input line to the vcv for a vacuum orifice. It would be a plastic bit with hose barbs on both ends. These are used as restrictions at various points in the system. Remove it and run the hose directly to the VCV inlet.

I have ~25in HG vacuum available from the vacuum pump. I have that vacuum hooked directly to the VCV, no restrictions.

The ~10in HG coming out of the VCV I beleive is within the spec its supposed to be.

Maybe so, but the VCV in my video is directly connected. So there must be either a leak or a restriction somewhere in between.

I picked up a new valve. I'll swap it in and then take apart my old one to see if I can make it hold 20in. Hg.