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Dutch924-racer · Joined: 23 Jul 2007 Posts: 1081 Location: The Netherlands

I still have two larger airflow meters that came with the Willibald 931 engine.

Will this be of any benefit (HP improvement) ?

The 931 (left) one is 76mm valve, the Willibald ones are 86mm.

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937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

Fifty50Plus · Posted: Fri Oct 25, 2013 2:10 am Post subject:

For the turbo, I suspect that the larger air flow meter is a benefit. For an NA, the area of the throttle body is probably the restriction rather than the air flow meter.
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1979 924 NA race car H-Prod SCCA
1982 924 NA race car - Sold
1981 924 Turbo sold
1982 924 Turbo sold
1972 911 E race car - traded for Cayenne Diesel
1975 914 1.8 Building for H-Prod SCCA

Carrera RSR · Joined: 08 Jan 2010 Posts: 2312 Location: Somerset, UK

Would be keen to see the results of this, and bag one of those myself as I reckon mine could do with more airflow. What car is the 86mm version from?
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
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Dutch924-racer · Joined: 23 Jul 2007 Posts: 1081 Location: The Netherlands

It looks like a Mercedes unit, there are no numbers on it.

It also had a different WUR, I will post the number of that this weekend.
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937 trackday car
Series 2 engine
951S turbo and intercooler
Fast road camshaft
Forge recirculation valve + boost controller

morghen · Joined: 21 Jan 2005 Posts: 9095 Location: Romania

merc or 928
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Supercharger and EFI kits
https://www.the924.com

dpw928 · Joined: 02 Nov 2002 Posts: 1860 Location: owasso, ok 74055

Please keep in mind that a larger venturi will result in slower air movement past the air sensor plate and may cause the engine to run lean.

Dennis
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81 931 5 sp
78 928 5 sp Silver
78 928 AT Euro Black

gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

The length of the lever from the centre of the plate to the pivot is the same? The vacuum of the engine will pull the larger area harder and rise the plate higher for every given rpm if you don´t compensate with higher systempressure.

Measure the length of the lever from centre of the plate to the pivot and multiply with the area and divide with the length from the pivot to the plunger of the fuel distributor. It is the same for 924 and 931, and probably for all 4-cyl CIS cars using the same fuel systempressure.

It is a delicate trade-off. High pressure will cause restriction, but so does a small area.
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

emoore924 · Joined: 13 Apr 2004 Posts: 2822

Ok, I'm going to take the low road here and say if it works it will be dumb luck. The whole CIS setup is a *system* where all the parts are designed to work together; AFM, WUR, TB, turbo, manifolds, injectors, displacement, all of it. You change out one part without considering the rest of the design and you can put the whole system out of kilter.

Yes, it *might* work, but the they don't call it German engineering for nothing...

Rasta Monsta · Joined: 12 Jul 2006 Posts: 11733 Location: PacNW