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Alan L Alan L is offline
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Join Date: Apr 2006
Location: New Zealand
Posts: 3,248
Goran, with my current fuel settings, when the WUR boost diaphragm kicks in, my AFr's drop into the 9s. The car bogs. It did not do this intially with my previous fiddling. But when I got the car, the system pressure was pegged, at a guess somewhere around 120-130 psi, and my WUR cold pressure was 50 psi. I lowered these to book values, and about that time had my AFR in. Last track date, with my suspect dizzy, my AFRs on boost would drop to 11.5 and rise to 12.2 at redline (6000) - which from all I have heard on this board is about normal - running out of fuel at top end. But my pre boost AFRs were quite lean - low throttle in the 14-15s and the car just bogged down completely. Would not tolerate it. So I have assumed all along that the fuel management has been the problem. Certainly getting the pre boost AFRs down has improved it. But then the top end was too rich.
I then found my WUR pressures were still suspect because my battery may not have been good enough. Put new battery in and found they were still high by book values, and dropped them to book spec. I have dropped my WUR cold and system pressures by about 30 psi from when I got the car. But now my boost enrich is far too heavy. Strangely, in desperation for the track day, I tried blocking the boost dump off, and found it behaved like you would programme a digi WUR - it got richer with revs at top end. I expected it to lean off.
I can't log this data simultaneously at the moment, but I do have an analogue output on my AFR. At the moment I watch it, which can get a bit busy in traffic. Every now and then you find a clear bit of track, and monitor it. It is sitting just above top of my steering wheel - the one piece of data I can see all the time. Basically at moment low throttle pre boost it is around 14, as it hits boost it progressively drops (rather than dumps) and richens thru the 12s into mid 11's at max revs. I can change this end point (and fiddled with it at the track) - but it has the same effect at the other end of the range. If I try and put more fuel in for the pre boost lean spot, I get a richer AFR at top end.
This behaviour is very strange from all I've heard. I can feel a slight flat spot at the boost transition (which may be knocking some of the edge off the boost onset) , and suspect it would like a quick dump of fuel to get up and go at this point. I was considering getting some heavier WUR boost springs made up. But think I'm probably better to go with the digi WUR. I wonder with the previous unusual fuel set up if the WUR spring has been changed to match the fuel managment that was set up - which was definitely all out - dump as much as you can.
One Porsche tech at the track y/day suggested it may have come with a RUF fuel set up - given it has RUF wheels and front/rear ends, plus some engine mods.
After months of flat spots pre- boost it just feels so different to have progressive throttle response. Different car. And great fun to drive now. Just have to get it going faster - still behind my previous NA lap times.
Old 08-03-2008, 03:50 PM
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