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Re: Homologation of Alpina A4/A4s systems (a little info)

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Guest Anonymous

URL: http://www.moreschi.info/pezzi/bmwa2002_2.jpg

I have the FIA homologation papers for 1973 (Gruppe 2). Quite a bit to them, vented rotors of course and rear discs etc., Regarding motors, the BMW M12/7 (16v with slide throttle) and the Schnitzer 20-4 (16v slide throttle) were the motors approved. While the Alpina A4/s motors were nice for street/hp cars they just couldn't match up with 16v power so there was no sense in trying. That said, I am sure that they were used in rallying, hillclimbing etc., In most of the racing applications where Alpina was racing (it is a fact that in 1974 Alpina was using Schnitzer 16 v motors in their cars because their motors couldn't cut it) they were using their own slide throttle motors (8v only). Pretty sure they used this motor up until 73 when the 16v's were homologated. Attached is a photo of an 8v Alpina slide throttle (dry sump).

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Guest Anonymous

Instead of a butterfly that rotates to allow air into the intake runner, a slide throttle has a bar with a hole in it that moves across the carb throat to let the air in. When fully open, the butterfly is more restrictive than the slide throttle because the butterfly flap is still in the middle of the airstream.

I don't know how much difference it really makes in the long run, but they sure look nifty.

Mike

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Guest Anonymous

I know that there are a few out there that are more "techno" engineers than I. Alpina's A4/s system uses multi-butterfly's (throttle plates) in each throttle housing which also have idle adjustment via spring loaded idle adjustment screws. With regard to air flow you have the throttle shaft and butterfly plate to impede air flow--works great on a street car because you can get idle. Alpina also has the fuel injectors mounted at the throttle housing similar to the stock tii manifold (close but not the same) The slide throttle on the other hand is essentially a manfiold that houses a sliding plate that has holes machined in it. As the throttle is acutated the holes in the sliding plate begin to align with the intakes on the manifold. Wide open there is no restriction (straight through) of throttle shafts or butterfly's. Fuel injectors are usually mounted in the ends of the velocity stacks. This wouldn't be good for a street car because at when the sliding plate is not wide open, the injector sprays against it causing fuel to pool (and sometimes leak onto the engine). Bottom line is that slide throttles get maxiumum flow/performance but under racing conditions (wide open). Would not be adviseable to try and run one on a street car (BMW used this on the 8v racing motors in the late 60's early 70's, also on the Formula 2 cars/Gruppe 5 320's in the 70's / 80's also on the M88 procar engines. Same system was used by Porsche on the 70's 911 RSR's and Ford Cosworth motors.

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Guest Anonymous

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16 valve motors. I posted last year that i saw a real deal Heidegger dual overhead cam M10 F2 motor at my fried's shop and that i was going to try to buy it and build a car around the engine... but the owner of the engine was rude enough to actually come and take his motor home! all my fantasies gone! I have seen the schnitzer slide throttle system and it is gorgeous. Forgot that Alpina dabbled in it. Very arcane stuff: highest grade engine work , very few examples remaining, very few mechs. from the day to talk to about them. Now this is exciting stuff to me. But it yanks me into the stratoshpere of cost- But I can save up!

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