thepest
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| posted on 30/12/09 at 02:37 PM |
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Ignition advance curves
I've looked at a few 2d racing curves, why do they flatten at say 3500RPM? wouldnt it be better to have a constant increase in ignition advance
as RPM increase.
Thats the setup I have right now on my xflow running megajolt, is that wrong?
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02GF74
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| posted on 30/12/09 at 02:50 PM |
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in an ideal world, yes.
my guess is that at higher revs, the engine is no longer as efficient as regards to filling the cylinders with the correct mixture hence the igntion
is not advanced.
otherwsie you would see power curve keep on rising with rpm yet we see that it starts to drop off.
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britishtrident
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| posted on 30/12/09 at 02:56 PM |
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No you run into a mechanical issues, use too much advance and the initial combustion will try to drive the engine backwards.
The most total ignition advance I have ever seen used was 43 crankshaft degrees on Hartwell Imp engines, the other Imp engine builders stuck with 38
btdc and didn't suffer any loss of power.
How much advance that can be usefully used varies, generally the more controlled turbulence in the combustion chamber the less advance is required
because turbulence speeds up the spread of the flame front through the combustion chamber.
One of the reasons multi-valve engines are superior to two valve engines is the modern pent roof style four valve combustion chamber has a natural
"tumble swirl" which improves mixing in the combustion chamber and speeds up combustion.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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