Quote:
Originally Posted by Stan Weiss
Can you please explain how that works?
Thanks,
Stan
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In many of the Stock, Super Stock and Comp Eliminator engines I have been involved, one of the typical issues that were common with some of the profiles issue with exhaust reversion. Clues of exhaust reversion were sooty intake manifold plenums and exhaust ports.
It has been a known fact and proven that any valve opening event or lift that takes place prior to TDC will effect the performance of an normally aspirated engine.
The intake event during overlap at BTDC, can expose and contaminate the intake charge with exhaust gas all the way to the TDC event when the piston reverses direction and starts down on the intake stroke. The reduction of reversion improves port velocity and improves cylinder filling.
Many years ago, friend asked for help with his new Comp engine that supposedly made enough power in the dyno to make him top of the class. It did not happened and when the engine was put in a different dyno, it did not make the power claimed by the builder. The problem was reversion. Based on his cylinder head and intake flow data and other details, I had a new camshaft ground with different timing events. The result of both the camshaft change and intake plenum volume change was 89 HP. Moreover, the engine required less timing, and although the cam had more duration, the engine had more PTV clearance with the new cam. After the camshaft change, the intake plenum volume was also reduced and the engine picked up 89 HP with both changes.