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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Hi Zane, yes of course I have.
You're pushing the 17mm diameter control plunger/piston upwards against fuel control pressure in the top of it's cylinder when you are pushing down on the 930 sensor plate, thats the hydraulic fuel pressure and resistance that you're feeling.

Control pressure is created by system fuel pressure in the lower chamber flowing upwards through a very tiny orifice in the steel gasket that seperates the top and bottom sections and chambers of the fuel head.

From that orifice fuel flows into a seperate chamber in the top of the control plunger's cylinder.
From there that fuel pressure flows out of the middle of the top of the fuel head to the WUR where the WUR returns a certain amount of it to the fuel tank through a small banjo fitting on the side of the fuel head that links to the main metal fuel return line banjo fitting off the side of the fuel head.

The only thing that changes control pressure is the warmup regulator/control pressure regulator because it returns fuel to the gas tank faster than system fuel pressure can flow through that tiny orifice in the metal gasket, and on into the chamber on top of the control plunger.
The restricted flow rate of fuel through that tiny orifice is why the WUR can change control pressure by varyinfg the amount it returns to the tank.

Now, with all that said.. when you floor a 930, turbo boost pressure goes into the bottom of the WUR through a little hose off the throttle body and by moving a sealed diaphram it moves the multiple spring loaded linkage to the internal valve at the top of the WUR so more fuel will bleed off the top of the control plunger and return to the tank thus lowering control pressure and allowing the control plunger to move higher in the fuel head with a given amount of upwards mechanical force from the air flow sensor plate linkage and uncovering more of the 6 seperate fuel metering slits in the control plunger cylinder wall.

I could go on with what happens to fuel from there before it goes to the injectors but thats not what this discussion is about.

You can think of the boost enrichment function of the WUR as a crude mechanical MAP sensor from the early 70's.

With the control pressure being lowered considerably under boost the air sensor plate is alot easier to push down.

Hook up the pressure side of a mighty vac to your WUR boost enrichmnent hose fitting and pressurize it with 14-15 psi, or .9 - 1.1bar like most of us are running and then push down on your air sensor plate and get back to me with an update on your previous statemant...

So... adding light weight mass of some type onto the the airflow sensor plate kind of like a spoiler/wing on the back of a car is likely going to push it down farther as air flows over it and into the big rubber 90 degree hose when under boost and give the injectors more fuel.

Someone has to actually try this because absolutely no one can say it will or won't work till it's been tried.
Old 11-23-2009, 03:05 PM
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