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#41 Re: A12, A14, A15
ddgonzal Posted on: 2002/11/20 6:48
Quote:
has anyone heard about variable compression like moving the whole crankshaft up or down
No, but the in the new BMW 7 series the camshafts move up and down to control valve lift, and thus airflow. The engine doesn't even have a throttle!


#42 Re: A12, A14, A15
dimlight65 Posted on: 2002/11/20 18:57
Not that I'm adding to the conversatin but I too have read of both of those innovations, BMW's throttleless system and Saab's variable compression.
The BMW thing basically varies the lift and timing on the valves to such a degree that it keeps the engine at the best volumetric efficiency for the given load and speed. They barely crack open at low speeds but really get wide when needed.
Saab's thing has the cylinders and crank seperatated, and a pivoting device that makes the pistons ride higher or lower in the cylinders to vary the compression. They, Saab, also were playing with a variable spark gap engine where the piston has a little "titty" in the center that acts like the ground electrode on the spark plug. I'm not sure what the reasoning behind that one was though.


#43 Re: A12, A14, A15
dimlight65 Posted on: 2002/11/21 21:13
I would also like to say:
"Bunnies!"


#44 Re: A12, A14, A15
ddgonzal Posted on: 2002/11/22 5:35
Looks like Pitroad has the adjustable cam gears - kinda expensive though:
http://www.pitroad-ts.com/englishpage/a-02.htm

Oh, and they work with the 76mm bore engines.



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