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Re: highest compression for propane

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Posted by Dodgeit on October 18, 2012 at 12:41:10 from (

In Reply to: highest compression for propane posted by ITS GREEN on October 05, 2012 at 17:50:16:

buickanddeere said: (quoted from post at 13:41:04 10/18/12)
Dodgeit said: (quoted from post at 13:58:14 10/18/12)
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 .

The flat top piston would allow you to run more advance, because you would not need to overcome the piston dome blocking the flame front, there by need more time to properly propagate the burn.

Flat top piston requires less advance .

The idea is not to run an engine with as much timing advance as possible. The least amount of advance that is required to make peak power is a better way to make the most and reliable power.

An engine that makes lots max power with 30degrees advance is more efficient than the engine making max power using 35 degrees advance.

What I was trying to say was that a pistom dome, all things being equal requires that timing be retarded because of the dome masking the flame front. You could run 30 degees no problem with a flat top piston wheres as you may only be able to get 22-23 degrees with the dome build to make max. power. Based on the primis that the map loads each build is seeing is the same. I wasn't try ing to get into what is needed to accomidate each piston type to make it a viable canidate for "A" job.

Most don't match build components to the job they want the engine to perform. Generally a home build is the "mostest of the mostest. Big Domes, long duration high lift cam, carb four sizes to big, huge valves and ports that would swallow Texas. And believe they have a horsepower monster, and they do @ 8000+rpms with a 200 rpm power band. Not at all suited for pulling in a MPH or gear limited event.

This post was edited by Dodgeit at 12:42:18 10/18/12.


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