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SU performance tuning... 1800

posted by  Bennie on  Tue Mar 1 06:07 CST 2005
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last visit: Wed Nov 28 03:03 CST 2007
[RELATED]

No! It's NOT linear by any means.

Yep, thats what I said. But I do not understand what your trying to say.

Lets say an engine does 3000 rpm at part throttle. Relative low compression in the cilinder, relative slow burn rate, need for early ignition. Then you open up the throttle: higher compression in cilinder, faster burn rate, need for later ingnition. The vacuum advance unit takes care of this till some extend.

At 6000 rpm and full trottle the vacuum in the manifold will be low, so ignition will be the same as when doing 3000 at full throttle. However, the engine revs twice as fast. Next to that, the compression in the cilinder will be lower due to flow restrictions, causing a slower burn rate, increasing the need for extra extra ignition advance.

You say: Beyond a certain speed you don't need to light off the charge earlier to keep up with rpm. But why then? It must be since basically all ignitions (of all kinds of engines) advance till about 3000 rpm) but I just dont get it.

Thanks, ben

--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)






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