View Single Post
spuggy spuggy is offline
Registered User
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,414
Originally Posted by PrimeMvr View Post
Since there is only one TB hose, I don't understand how it can control both vacuum and boost enrichment.
I'm not so sure that it does provide enrichment on vacuum on 930's, although 965's did have this, IIRC. But on earlier cars, I think vacuum enrichment is purely for N/A cars.

But anything in the intake under the throttle plate will see both vacuum and boost, depending.

My understanding is the hose on top of the WUR going to the airbox is nothing but a vent??
Correct. It's vented so the WUR can react quickly internally, and the hose is to direct the stream of high-pressure gasoline away from the hot motor/exhaust if the diaphragm splits, in the hope that you'll notice the car running really badly and figure it out before it catches fire...

Idle AFR is mid 14s. The lightest touch of the throttle in neutral will lower it fairly linear with increasing RPM to high 12s. Light throttle cruise at just about any speed is low 12s and I average around 10 mpg.
Idle sounds right. Little rich in cruise maybe.. Not sure revving with no load gives any useful information.

WOT drops almost immediately into the 10s and 9s when boost comes on, slowly rising over 5500 RPM and maxing out in low 11s at redline. Can you say "washing the cylinders?"
Yeh, sounds rich in the mid-range. Personally, I'd be delighted to see 12 at WOT...

Which leads me to the question that I cannot seem to find the answer to: How do you adjust warm CP with a stock WUR?
Well, that's the kicker. You can't - except by knocking the plug into the body or pulling it back out. I believe that this actually changes the CCP, but that it has a knock-on effect on WCP as well.

You can knock the plug in with a punch (which makes it richer/lowers the control pressure), but to pull it back out (like when it moves more than you expected) implies either dismantling the WUR to reset it - or just modifying the WUR so you can pull it out more conveniently than taking it off the car and dismantling it. That'd get old pretty fast.

Yes, I know the BL WUR is a great product and pretty cheap, but I enjoy DIY
Then get reading :

Modified my WUR
Turbo WUR?? need CIS Gurus help
Who sells rebuilt WUR's

Should get you started.

Bear in mind that, even if you modify the WUR as shown, that's a long way from what you get with a Brian Leaske adjustable.

BL provides a stud in the CCP adjustment point (the plug). The WCP adjustment on a BL adjustable is done separately through the hole in the center of the boost enrichment adjustment points (also adjustable, although to a lesser degree).

I think that moving the plug alone may force you to make compromises with CCP to get the WCP pressure you want/should have. Neither changing the CCP nor the WCP does anything to address the shape of the fuel curve itself - especially with boost enrichment - which is basically not what we think we want. (too rich in the midrange and leaning up top).

Some have had good results with the RPM solenoid, but I think you're basically limited to tuning the WOT/full RPM mixture, messing with the enrichment start point - and just putting up with what's left, unless you control the pressure according to boost/RPM, like several here are already doing.

Anyway, BL first rebuilds the WUR, making ALL of the following individually adjustable:

Cold Control Pressure
Warm Control Pressure
Boost Enrichment (amount)
Boost Enrichment (onset)

He also installs a better (stronger) diaphragm, I believe (he certainly can if you will be running more than stock boost). Based on what you told him about the tune of your motor, he makes an educated guess as to where the various pressures should be set, sets the WUR to those pressures so that the whole thing is a bolt-on - and then writes them down in the documentation he provides with the unit. I thought mine was a little richer than optimal, but I expect he knows pretty much exactly where the ballpark optimal is, and was just being conservative

The value is tough to beat for $300. You could save that in dyno fees...

BTW, lambda is open loop.
Many have said their car runs better with lambda enabled, as long as it is working correctly. It makes no difference to power, because it's disabled beyond a certain throttle opening, and should help with light cruise gas mileage/running considerably.
'77 S with '78 930 power and a few other things.

Last edited by spuggy; 07-01-2011 at 11:43 PM.. Reason: Fix the quote I didn't terminate
Old 07-01-2011, 11:42 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #3 (permalink)