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The only metering of fuel is via the airplate flap - which is mechanically connected to the metering piston in the FD. There is a cut out waist in the piston and it rises in the FD head as the airplate opens - it gets pushed up against the WUR pressure settings. As it moves up it travels past metering slits in the FD body and the exposed slits allow more fuel thru. Each slit is connected to an injector port.
The only other 'enrichment' dump is when you hit the boost mark. The WUR has an extra port which allows the manifold pressure to connect to the WUR. The pressure depresses the diaphragm in the WUR and softens the WUR pressure. This allows the piston to open more of the metering slits - so you get a boost dump enrichment.
It stays in this richer WUR setting until you return to vac MAP.
It doesn't take full boost for the fuel dump to occur - typically the WUR pressure starts to drop around 0.3 bar MAP.
Regards
Alan
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83 SC, 82 930 (track) - Stock except for RarlyL8 race headers, RarlyL8 Zork, K27-7006, 22/28 T bars, 007 Fuel head, short 3&4 gears, NGK AFR, Greddy EBC (on the slippery slope), Wevo engine mounts, ERP rear camber adjust and mono balls, Tarret front monoball camber adjust, Elgin cams, 38mm ported heads, 964 IC. 380rwhp @ 0.8bar Apart from above, bone stock:-)
Last edited by Alan L; 12-18-2023 at 04:47 PM..
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