MLPANKEY said: (quoted from post at 15:03:56 10/17/12)
Dodgeit said: (quoted from post at 07:42:14 10/17/12)
Dodgeit said: (quoted from post at 14:32:03 10/15/12) I'll throw this in just for Shitzengiggles. Two indentical make and model engines. Both at 11-1 compression. The only difference between the two is dome height on the piston. One is flat topped and the other has a 20cc dome. Running 91 octane pump gas.
All build componets to include, setting, temprature, humidity, and anything else you can think of is the same for both engines.
Which engine will be able to run more advance without detonation, in a high load situation?
B&D, MLpankey, please refrain from ruining the fun for others. I know you know the answer. I want to see how many others do.
Hint the answer is the same for any fuel type.
Since no one ventured a reply. I have to wonder, if the question was too hard?
B&D, MLpankey you two are free to post the answer, as is anybody else.
Lets here your thoughts Dodgeit. I would at first thought say the flat top cause its cylinder head would have to have a smaller combustion chamber but thats not always a winner for instance big block chevy . When the engineering staff went away from the closed combustion cylinder head to the open chamber cylinder head the engine made close to 100 hp more even with a 1 static point less compression ratio . Mainly because of valve shrouding .
All things being equal for discussions sake the flat top piston in general would allow you to run more advance, because you would not need the time to overcome the piston dome blocking the flame front.
I was basicaly just trying to make another simple point that many overlook when building a performance engine. All the go fast goodies don't always, play nice together. Now if you took the engine examples I mentioned and changed just the cam shaft, you could make them perform in two arenas.
The flat top build would do nicely for tractor pulling or road / flat track racing. Because you could build a torque engine that would respond well to throttle inputs for road racing or a high map , low speed load seen in tractor pulling.
The pop top piston build would work the best when used in a high rpm WOT situation, such as drag racing or Talladegia type, super speedways. In tractor pulling the pop top build would give up too much "streetability, for lack of a better word" when used in MPH or gear limited classes.
Again I'm just generalizing. Each build could be made to work in both scenarios, with alot of forthought put into matching the rest of the components. But again the flat top would be a better WOT engine than the pop top build would be if used in one of the mentioned flat top builds in overall usefulness just because of the piston dome.
This post was edited by Dodgeit at 12:24:47 10/18/12.
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