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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
I spoke to a 930 tuner years ago that modified WUR's to be boost sensing and to operate at a lower on boost control pressure for more fuel (Rice Fueler). He made me aware that even with lower on boost CP settings the metering arm still dose not reach fuel range of travel. He found that on a dyno at full tilt he could push the metering plate down further with a screw driver and flood the car. Thus, I am suspicious that modifying the metering pin is of significant value.

Another way to test this the additional fuel delivery of the stock head and that we are not accessing it is to set the idle CO very fat. Then run the car up and you should see that the top end gets more fuel even though you thought you were at a limit. What this is doing is changing the position of the metering pin relative to air flow and allowing it to advance further. Until doing this no longer adds any fuel up top, we still have fuel delivery capacity left. Thus, if we can get the metering plate to not stall, we can get more fuel.

Steve Werner is the only tuner I have heard of that addresses this by relocating the hinge point of the metering arm. This allows the metering pin to travel further with any change in the metering plate position. If I recall correctly SW used to build a sweet 930 with gears, 3.5 twin plug w MSDs, 8/1 CR, ports, and .7 bar boost that was good for 425hp. Start to go much past that and the issue becomes premature ware and limited thermal reserve.

It might be helpful if we knew if we are talking flywheel HP or rear wheel HP.

I do not know if gross air flow is the problem at the HP levels we are talking about here. I think it is more how the metering plate responds to the air flow we have.
Old 04-18-2009, 08:26 PM
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