How much timing are you pump gas+alky guys seeing
10-31-2007, 01:07 PM
#4
I've been trying to find out the same info. People keep telling me it all depends on your setup, too many variables, etc. I found a setup that was very similar to mine on EPP's website here. I asked Bob what timing they ran with that setup and he told me 22°. Hope this helps you some...
10-31-2007, 11:55 PM
#7
The whole purpose of changing timing is to allow the motor to ignite the fuel/air at the point which yields best efficiency without any adverse effects (such as detonation). The old school rule of thumb is that peak cylinder pressure should be at 15* after TDC. Leaner fuel mixtures burn slower, as do extremely rich (over about 11/1) mixtures. More compressed mixtures burn faster than less compressed ones. At any given mixture/compression combination, the burn rate is static with regard to engine rpm (in generality). This means that the fuel takes just as long to burn at 1000rpm as it does at 8000rpm. Since the fuel takes the same amount of time to burn, but has MUCH less time to do so at higher rpm, the timing must be advanced to achieve peak cylinder pressure at the same point in the piston travel. There are a ton of other issues that must also be taken into account, but that should answer your question in a grossly over-simplified way.
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11-01-2007, 07:55 PM
#8
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With a maggie at 10psi, 9.6:1 compression (LQ9 heads), GT2-3 cam and 92 octane, I am only able to run about 14° before getting KR.
I am hoping to be able to run more with the AFR 205's I am going to put on with a higher compression. Reason being, I think they have a better combustion chamber squish.
I am hoping to be able to run more with the AFR 205's I am going to put on with a higher compression. Reason being, I think they have a better combustion chamber squish.
