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Alan L Alan L is offline
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Join Date: Apr 2006
Location: New Zealand
Posts: 3,261
I think mine is type 145 (if that makes sense) . Bit hard to get at now.
The springs ; in the early days when I was struggling with a bunch of problems, including the ubiquitous excessive fuel dump, I had a series of springs made for the WUR. These were to replace the base boost dump spring. They were made in a series of harder pressures to compress the spring. The working length of the spring is about 11mm. In other words the approx 2" long spring compresses to around 1/2" in the WUR. It takes a certain amount of force to compress to this point (about 3kg stock spring). I had a bunch made progressing to 5+kg. A slightly heavier wire grade will do it. There are a bunch of calcs you can do depending on the wire - the length of wire is one factor. Anyway - I think you are right. It did not seem to control the boost dump very well. I then deviated off to the Digi WUR /UT path for a few years until they got junked. Then I got to physically restricting the travel of the boost diaphragm - fitted a screw in the base of the WUR and that is where I am back to now. I can apply the 0.8bar boost pressure on the WUR and with CIS gauge set up can adjust the screw to allow a max CP drop.
My current settings (as of y/day) are WP 3.4 bar, boost CP 2.7bar. The factory specs are 3.6/2.9. I have installed the stock spring again. Not sure why I was getting such a massive boost drop. All I can do is try it out and adjust from there. Trying to work out if I can sneak out on the hway rather than waste a day getting to the track for 10 mins of data. With the race livery and zork it is somewhat conspicuous.
As for the max flow, Brian raises an interesting Q when asking how determined. Would be interesting to see what he does. But AFAIK the airplate does not fully open at WOT. So I am not sure fully depressing the airplate gets you the actual max flow . I have sketched out what I think happens in this respect. So the trick is to know if the slits are fully uncovered by the metering edge of the piston. I recall some early threads on this topic where pioneers were trying to uncover more of the slit. Which is what I think the airplate cone was about. And the drop in CP at boost is trying to do the same.
83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)

Last edited by Alan L; 11-09-2017 at 10:42 AM..
Old 11-09-2017, 10:01 AM
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