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Octane and higher compression

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bhill

Member
Any thoughts on 87 octane with a high compression chamber? Anyone ever run into issues with performance ?
 
bhill said:
Any thoughts on 87 octane with a high compression chamber? Anyone ever run into issues with performance ?
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I'm wondering what you consider high compression? What is the compression ratio? Have you ever checked the compression pressure with a gauge?

The problem is detonation! You get detonation from excessive heat and/or pressure. Need to know your compression ratio to determine an octane with any degree of success. Higher compression ratios, (of course higher is a relative term) are the reasons there are multiple octane ratios available.
 
Mr.Al when you remove material from a stock cylinder head or engine block, the compression of that particular cylinder will increase. I am asking the question that if anyone has any experience with performance advantages or disadvantages with raising the compression of a stock predator engine. ( while running on 87 octane )
Perhaps someone has been down this road and could give me some advice on what there expereince was with this process. I'm running stock piston , .10 in hole, head shaved to fin ( flush )
 
I think Al's question still stands bhill. Slim chance that someone with your mods has milled their head to your exact measurements and tried it on 87 octane.
As al stated need to know the static compression ratio to get an idea if your close to needing a higher octane to avoid detonation.
 
Outcrydrummer said:
I think Al's question still stands bhill. Slim chance that someone with your mods has milled their head to your exact measurements and tried it on 87 octane.
As al stated need to know the static compression ratio to get an idea if your close to needing a higher octane to avoid detonation.
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That's odd , one would think that someone would try to get alas much compression as possible , I think it creates H.P. ( horsepower )
 
Maybe I'll try running the engine ,pull the plug wire when engine gets 400 degree, and if engine still runs I'll know I need to go with higher octane. Or perhaps less timing, or littler cam, can anyone help me?
 
Just my thoughts... But why not just run 91 octaine? I'm guessing class rules? But I'd be willing to say 9.5/10 to 1 would run on pump gas? The cam will play a big part but I would shoot for 10 to 1 and keep a few extra gaskets around
 
We have used regular fuel in engines up to 10:1 alot depends on various attributes not simply CR. Try it listen and look for signs, I don't think you will get it hot enough to diesel when you pull the plug wire so that is unreliable.
 
bhill said:
That's odd , one would think that someone would try to get alas much compression as possible , I think it creates H.P. ( horsepower )
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What does that have to do with what I said at all? Your asking for help and were trying to get more info from you so we can help you. Nothing in my reply was geared towards why you would or would not want to increase compression. Obviously you already have if you have milled the head. A smart @$$ attitude isn't going to get you much help from anyone here.

Good luck
 
Outcrydrummer said:
What does that have to do with what I said at all? Your asking for help and were trying to get more info from you so we can help you. Nothing in my reply was geared towards why you would or would not want to increase compression. Obviously you already have if you have milled the head. A smart @$$ attitude isn't going to get you much help from anyone here.

Good luck
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Thanks
 
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