Wur -153 - pressure adjustments

[albinski]

Hi Pelicans,
We're working on a 930/68 engine.
It does smoke a lot (black) on boost. AFR goes to 9'ish.
Control presures cold and warm are within spec.
According to porsche tech docs, wur should be dropping conrol.pressure by 0.5bar under boost; the wur in the car (brand new) drops the pressure by 0.9 bar. This is what we are suspecting to be the problem, especially in mid-range rpm - 3-4k.

Comments welcome.

The main question now is how do we bring the control pressure under boost to the correct spec.
Cold pressure adjusted by tapping the pin.
Warm pressure gets adjusted by tapping the cylinder
What about the boost pressure?
There's a hex bolt at the bottom of the wur, adjusting small spring tension but it does not seem to impact boost pressure.

Any advices here pls?
Thanks
Krzysztof

[Chris_chch]

Under the WUR, there will be a brass plug, which I'm assuming from your description, has a hole drilled in it, with the hex head inside.

The brass plug is the travel limiter for the boost enrichment. That plug needs to be tapped in a bit and it will then limit how far the piston can move down.

I'm not the best at describing it, but if you do have a hole in the brass plug, you can see the hex head adjuster move down while you apply pressure to the boost reference nipple. That will give you a better idea of what I'm attempting to describe...

This is all on the UNDERSIDE of the WUR

Good luck! and tap lightly....or you have to pull it apart to tap it back out if you go too far

Chris

[RarlyL8]

... or you could modify the WUR to be adjustable.

[albinski]

Many thanks Chris!
No, plug is not drilled, but i know guts of these devices
it is not the first wur in hands that been taken apart, and some got the pin drilled and tapped for cold pressure adjustment

Will work on this one as advised and report back the result.

Thanks again
Krzysztof

[albinski]

Just a quick follow up here to say that boost pressure has been adjusted using instructions above. It took few attempts to get the brass plug to desired position but we eventually got it where it was supposed to be
Thanks for all the support guys.
Regards
Krzysztof

[Chris_chch]

Result!