As he said, tuner's problem.

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Added on October 24, 2008, 2:01 pmyou better check back what Guan posted regarding to the knocking issue.

This post has been edited by drexchan: Oct 24 2008, 02:01 PM

Interesting... but need some clarification:

1. degrees as in cam or crank degrees?
2. advance as in advancing the cam (clockwise) or the crank (counter clockwise)?
3. what's A/F comp efficiency?
4. where you get the data from.

TQVM. =]

My brain went wee wang wang reading your explanation but lets assume that you got it right, have you factored in the effect of advances exhaust valve?

Exactly. It's all about getting a balanced point between the compression efficiency and power efficiency. While calculations may give you a picture of what's happening, the end result is still pretty much depending on OTR and on-dyno tests.

This is the reason why most DOHC tuners advance the intake and retard the exhaust. While the idea of advancing the intake and retarding the exhaust improve both compression and power efficiency, the high overlapping duration also means poor idling quality and narrow powerband at the high range. That's how high duration camshaft works.

The ultimate questions are - at which rev range the tuner intend to squeeze more juice out of the engine, how much advance, how much retard. The answers come with experience of trial and error, with or without dyno (which just makes things simpler).

Oh yes, just want to point out to you that you have neglected the flow efficiency in the intake and exhaust ports.

This post has been edited by drexchan: Mar 24 2011, 09:38 PM