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JBL930 JBL930 is offline
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Join Date: May 2006
Location: UK
Posts: 1,172
I'm simply asking this question so i can better understand how you plan to achieve what you are saying, i know you know your stuff so i'm all ears.
A stock WUR starts to enrich the fuel at about 3psi, which is 0.2bar, anyone can see that with a modern turbo fitted this amount of boost comes in really early, even below 2000rpm in some cases! Brian Leask states that the WUR boost threshold can be raised to as much as 8psi, this is 0.55bar. This boost pressure will be reached by around 2500rpm which is still way too early. In all of the applications that i am aware of I am told that boost enrichment needs to be delayed until above 4000rpm, sometimes as late as 4500rpm. By this point full boost has been reached for way over 1000rpm of the rev range, how can adjusting the mechanical boost enrichment threshold inside the WUR delay enrichment in this way? It can't, you can only delay it until a certain boost level and not a certain RPM point, full boost is reached long before it needs enrichment so the only way i can see of getting a flat AFR is with the RPM solenoid, Brian Leask clearly agrees with this.
If i am missing something here please enlighten me, cheers

Originally Posted by RarlyL8 View Post
No, what I am saying is the RPM switch is a good bandaid but does not actually fix the problem, it masks the symptoms.

The problem is that as the WUR ages it goes off spec. In order to recalibrate you need to go inside the WUR and do some adjusting. Once back in spec you re-gain the full spectrum of the threshold adjustment.
The RPM switch simply delays the onset of boost by hiding the signal until a preset RPM, effectively overriding the threshold system by shifting the threshold to a point requiring less adjustment. The resulting A/F graph looks better but the WUR is still off spec.
Old 06-03-2008, 11:51 PM
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