02GF74
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| posted on 21/3/07 at 01:35 PM |
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timing cam/ignition
Does any have or know where I can see data from tests conducted on engines shoing the effect of cam and ignition timing?
Basically what I am looking for is how the engine's power is affected if the cam is not timed as per manufacturer's recommendation, say by
1 degree increment before and after TDC and same for ignition.
If you been to rolling road and conducted such tests that are repeatable then thay may be enough.
In case you a pondering, I'm just curious as to whether vernier gears are hype or do make a difference, and if so, then how much.
Also data on how much from the manufacturer's setting a mass produced cam e.g. crossflow can be out by.
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coozer
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| posted on 21/3/07 at 01:55 PM |
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I think for cam timing if its out the vavle knocks off the piston.
Actually, if the ign timing is out that knocks as well
Cheers,
Steve
1972 V8 Jago
1980 Z750
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TangoMan
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| posted on 21/3/07 at 06:52 PM |
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There are two issues. Firstly cams, especially aftermarket ones, are notoriously bad for being ground off centre so the timing is out before you
start.
Secondly, altering the cam timing, within sensible limits moves the power up and down the range. From memory, although I could well be wrong,
retarding it gives better loe down power at the expense of outright max power.
On twin cams there is also the option to play with overlaps
I think Vizard wrote a lot about the effects of playing with cam timing.
Summer's here!!!!
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bricheun
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| posted on 23/3/07 at 07:36 AM |
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Cam timing
Retard cam timing - push power up higher rpm - at the cost of lower rpm torque.
Advance cam timing - push power lower down in the rpm.
Advance timing - feels very torquey, won;t be a screamer as power goes down high up.
retard timing - engine sounds and feels happier at higher rpm. The difference I am talking is about _/-1000rpm.
Remember to adjust your ignition - retard cam timing -> need to advance ignition timing
Advance cam timing --> need to retard ignition timing
There is only a limit you can do s don;t go +/- 10 degrees on the cam timing. The difference is huge and we are talking 2 different engine feeling +/-
2 degrees.
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