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Originally Posted by SaabTuner
As for water injection slowing the flame rate, I don't believe that's true. I recal reading one of the papers on this forum, I believe it's still posted, which showed that, rather than retarding the burn rate, it retarded the flame development angle.
Slowing down the flame development angle has little effect on detonation because you can adjust the ignition timing to compensate with little or no effect on total cyllinder pressure, or rate of rise in cyllinder pressure.
It's just like a delay between when the flame kernel is ignited, and when it propogates through the combustion chamber generating heat.
The rapid burn angle is what will control detonation. A slow rapid burn angle, as produced with a bad A/F ratio, contributes to detonation.
Adrian~
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ppp (peak pressure position) as you referred is a cylinder pressure plot against crank angle arriving at a peak value.
Are you implying that injecting Water will shift this PPP to the right hand side of the chart (delay). If this is the case, retarding the ignition timing would have the same effect as injecting water, I can agree to that to some extent. Torque change further confirmed this assumption.
I am interested on your view on what will happen to the ppp when water is injected after the igniton is advanced to re-align the ppp to the edge of detonation threshold. If this condition can be repeated many times until the there are so much water is being injected and the ingition is so far advanced but in the end the engine has no gain nor torque change? Does this sound correct?