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Join Date: Dec 2010
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A couple of WUR questions

I've been reading endlessly on proper CIS setup, both here and the Bosch book. I get how all of the pieces work together, except for how the WUR reduces warm CP on light throttle vs. boost.

Since there is only one TB hose, I don't understand how it can control both vacuum and boost enrichment. My understanding is the hose on top of the WUR going to the airbox is nothing but a vent??

My car is running quite well, but I'm sure I'm leaving both power and fuel economy on the table.

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.

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?"

I can block the boost signal to the WUR with an RPM solenoid, but since it enriches long before boost and even on light throttle, I'm guessing my warm CP is too low to begin with, allowing the sensor plate to overshoot. 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?

I have a gauge, but want to know how to adjust the pressures before I hook it up. Yes, I know the BL WUR is a great product and pretty cheap, but I enjoy DIY and I'm not finding the answers I need. Maybe I just need to open it up and stare at it for awhile. That worked wonders on my AAR and dizzy. BTW, lambda is open loop.

Thanks gents...learning more every day thanks to Pelicans and trial/error.

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87 930 - Black - 3.4L/964 cams/K29/Powerhaus IC/6AL-2/B&B dual exhaust/MTX-L/235-315 Toyo R888/18" Kinesis wheels/Big Red brakes/LSD
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Old 07-01-2011, 10:55 AM
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Bl wur

I am running almost identical numbers as you through the entire RPM range. I would like to remove my air pump before any adjustments are done. I really don't know if my LC-1 is giving a true reading, as air is still being injected into the exhaust manifold, pre wide band sensor. I have talked to a couple of wrenches who say this enrichment is running on the safe side, and don't think I should try to lean it out for safety's sake. Philip
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Old 07-01-2011, 07:12 PM
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Quote:
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.

Quote:
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...

Quote:
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.

Quote:
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...

Quote:
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.

Quote:
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...

Quote:
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.
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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
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I don't think your WUR is reducing warm CP under light throttle. Steady warm CP is probably low enough now to let intake airflow push the airflow metering plate down while raising the control plunger upwards against it displacing it a little faster than fuel is replenished through the small orifice leading to the control pressure chamber above the control plunger. That seems like a good thing that would improve throttle response at low speeds.

If you want to try making your WUR's warm steady cruise CP adjustable you'll have to experiment a little and start by removing the approximately dime sized gold cad plated steel cover pressed into the bottom.

I sent mine to Brian Leask to be made adjustable so he did all that. I've never removed the steel bottom cover so I don't know if what you'll find under there is the same adjustments you see on one Brian has worked on and made adjustable.

You could post that question on the engine rebuild forum and maybe one of the experts over there knows and will reply, or maybe they don't want to say what they do or is done by others.

Either way that steel cover has to come out.
Maybe they drill a hole in it and use a slide hammer or thread a self tapping screw into the hole they drilled and pry it out from the bottom while the WUR is clamped in a bench vise or maybe all the insides are removed and they press it out from the inside.

I'd like to know and I wonder if thats all it takes to expose the boost and steady cruise adjustments - if they are already there and factory set to CP specs for the year and model car it's going on and then covered up with the pressed in steel cover to make them tamper proof.
I'm just guessing at that and I don't know.
Not that I want to get into modifying them.. I'm just curious.

For the boost threshold adjustments he drills and taps 3 holes and installs 3 stainless allen head grub screws in a triangle around the boost CP adjustment with a touch of low yield loctite to keep them snug. When they are turned inwards they push the largest diameter internal spring upwards pushing against the CP fuel return line metering disc under the return line orifice.
Old 07-02-2011, 08:20 AM
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Thanks for the great info guys. Next rainy day I'll hook up the pressure gauge, see where I'm at, and decide where to go from here. I think JF has it right that my base WCP is too low to start with. In the absence of a definitive "just do this..." I will probably leave it as is until winter and then send it off to Brian.

I have a WB02 that has a NB output. I'm going to try hooking that up to the lambda brain and see what happens. The last time I did that it caused severe popping when the engine warmed up, but I have a feeling it needs to be calibrated to the right voltage range to match the NB sensor.

I have good throttle response off-idle, I'm just looking to get a little better cruise mpg and stop the pig rich WOT, but that might just have to wait, as I don't want to put the car out of commision at the peak of Iowa driving season.

I'll let you know what I find.

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87 930 - Black - 3.4L/964 cams/K29/Powerhaus IC/6AL-2/B&B dual exhaust/MTX-L/235-315 Toyo R888/18" Kinesis wheels/Big Red brakes/LSD
10 997.2 Cab - Speed Yellow
83 SC Cab - Guards Red [SOLD]
17 NSX - Nouvelle Blue
Old 07-02-2011, 09:10 AM
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