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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Cheap Fueler concept.

One of the ways we get more fuel is to lower control pressure on boost so the metering plate advances further and thus moves the metering pin further so more fuel passes thought the head.

Thus, advancing the pin gets us more fuel.

We can also advance the pin with the CO adjustment screw. This can get us more pin extension but at some point the AirFuelRatio at lower air flows is going to get way to rich.

To accommodate this we could plumb an air passage around the Metering Plate assembly with a valve in line to adjust how much air we allow to pass.

This should allow us to tune the AFR's back to the normal ranges at lower rpm.

At higher RPM the metering plate is still going to advance to its typical stall point given the on boost control pressure it sees. Having adjusted the CO screw the metering pin will have moved further allowing for more fuel just as if we had lowered control pressure.

Just a thought.
Old 11-22-2009, 08:57 AM
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Location: S. Florida
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I've been trying to picture this in my head and I just don't see how it would work at all...
If you got the motor running in a configuration like this I think it would be practically undrivable at low speeds and have a hard to control high idle speed.

If you had a working 930 CIS unit in front of you and you looked at the top of the metering cone, the VERY small air clearance between the edge of the sensor plate and the cone while at rest and at idle speed, and the sensor plate linkage arm and counterweight and how it links up to bottom of the control plunger in the fuel head I think you might change your mind about this theory.

That said I really like all your imaginitive ideas for modifying CIS and distributor ignition for more performance.
Old 11-22-2009, 12:20 PM
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Think of the tubing and valve like a bigger version of an air bypass screw but it just bypasses air around the metering plate, not the throttle plate.

It would be plumbed into the section just after the air filter and back into the section just after the metering assembly (could use a C2 Turbo elbow). The tube would need a valve in it to control how much air passes and to reset the AFR back to this ideal after the CO screw is advanced substantially.

Again, we are not bypassing any air around the throttle plate and AFR at idle will reset to our ideal using the new valve.

Another way to approach this might be to just clip or bend up the edge of the metering plate so it dose not respond so quickly to changes in air flow and then readjust the AFR back to normal levels by advancing the CO adjustment screw.

Might be better to just bend the metering plate at the end that drops the lowest into the metering cone when it advances. This should then also help increase the range of travel of the metering arm on top of the increased travel gained from the readjustment using the CO adjustment screw. Might be a more and simpler approach.

One post here some where noted his 930 had a metering plate that was in such condition and not one seemed to understand why this might have been. This makes some sense of it.

What I we do not know is what the AFR curve will look like. I suspect modifying the metering plate would keep it more stable. On the other hand the air bypass method might make is flatter at lower rpm and fatten at higher rpm as the percentage of air through the bypass becomes a lower percentage of the total air flowed.

Just a thought that would need to be tried.

Would be cool if just bending the metering plate and readjusting the CO could get us another 10% or so more fuel as if we had lowered control pressure using a modified WUR w attachments.
Old 11-22-2009, 02:53 PM
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That gives me an idea...
I wouldn't bend the edge of the metering plate up but you could remove the single bolt holding it on and sandwich another thin lighweight piece of aluminum sheet metal on top of the metering plate and bend the side closest to the big rubber hose upwards as far as you want to experiment with so the airflow over it would probably push the metering plate downward a little farther under full throttle.

Thats easy to try and remove if it doesn't do anything.
Old 11-23-2009, 11:55 AM
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Even try to push a metering plate down with the pumps on? At first, it is easy but gets harder and harder. Midway a lot of force is needed to push it further down but by then the fuel is pouring. Air is not going to be enough to advance it nor is any other mod to the plate. I say take advantage of the CIS fat fuel curve and create an artificial torque curve, just like Micke did with his 627hp mostly stock CIS car.
Old 11-23-2009, 02:18 PM
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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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Micke probably than it seems.

The "mostly stock" probably refers to his using mostly original parts like the rods heat exchangers, P&C's, and retaining CIS. Almost all parts including the fueling system were probably breathed on quite heavily and a very special turbo and cam were added to the mix.

Looking at his TQ curve it looks like a combo of a cam timing and pulling the boost back very quickly once the fueling limitation and the motor VE starts falling off. This is a guess.

I very much agree with the idea of working withing the fueling of the existing system including a high torque cam and active boost management that pulls boost back when the limit of the fuel system has been reached as solid approach.


I do believe adding a wedge to the meteringg plate should advance the meteringg plate further for more fuel and be much simpler.

Stage two would be reducing the advance rate of the meteringg plat through a larger meteringg cone or less windage at the metering plate combined with a HF fuel head.

If the advance rate of the meteringg plate is reduced 20% and the fuel head delivers 20% more fuel, they will balance out and the stock WUR settings could more closely be retained. However, we still need to figure out how to get the MP to advance further and not stall which is what the wedge dose as well as relocating the hinge point of the metering arm.
Old 11-23-2009, 03:19 PM
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