Checking compression ratio
08-31-2005, 11:40 PM
#2
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Join Date: Aug 2005
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Re: i no u can check a dirt bikes comp. w/ a tool, can u check a cars?
let me clear that up, i mean by taking the spark plug out and (or atleast this is how i think you do it on a dirtbike) and then put the tool in through the spark plug hole and cranking it up or turning it over.
09-01-2005, 06:36 AM
#5
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Re: i no u can check a dirt bikes comp. w/ a tool, can u check a cars?
so you can get something at advanced and check compression ? how's it work, just put it in a spark plug whole? and would it tell me like 9:1 or does it read in PSI, and if it does how do i know what PSI = what :1 ?
Last edited by glennxx1; 09-01-2005 at 07:03 AM.
09-01-2005, 10:17 AM
#6
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Re: i no u can check a dirt bikes comp. w/ a tool, can u check a cars?
It will read in PSI.
You really cant convert the PSI to compression because you are reading a dynamic compression of the engine, not static. Also it depends on your battery health, cranking speed, and the brand of gauge you have.
As a tool its useful to find the general health and compressing ability of the engine. You can compare cyl to cyl and see whats low, if anything. All your cyl should be within 10% of each other, and your first puff of compression should be at least half of the 4th or 5th.
You really cant convert the PSI to compression because you are reading a dynamic compression of the engine, not static. Also it depends on your battery health, cranking speed, and the brand of gauge you have.
As a tool its useful to find the general health and compressing ability of the engine. You can compare cyl to cyl and see whats low, if anything. All your cyl should be within 10% of each other, and your first puff of compression should be at least half of the 4th or 5th.
09-01-2005, 11:02 PM
#8
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Location: Bay Area, CA
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Re: i no u can check a dirt bikes comp. w/ a tool, can u check a cars?
No - there actually is a volumetric gas analyzer that can determine your compressoin ratio.
We built a motor for a super stock racer who wanted to use the pistons he had already bought, they made the static compression 9.8:1 spec for his class is 8.5:1, he was winning every race, which to his own bad luck had nothing to do with how powerfull the motor was, he is that good of a driver, but anyways, he got tested and the machine spit out 9.8:1, exactly what his build sheet says.....
We built a motor for a super stock racer who wanted to use the pistons he had already bought, they made the static compression 9.8:1 spec for his class is 8.5:1, he was winning every race, which to his own bad luck had nothing to do with how powerfull the motor was, he is that good of a driver, but anyways, he got tested and the machine spit out 9.8:1, exactly what his build sheet says.....
thanks for all the input by the way
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