7.5 to 1 comp. is = to ? p.s.i. comp.

badger999

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A legal class 9 engine can have no more than 7.5 to 1 comp., convert that to p.s.i. ,what is the max comp. In p.s.i. That will pass post tech. ?
 

JAM 1600

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A legal class 9 engine can have no more than 7.5 to 1 comp., convert that to p.s.i. ,what is the max comp. In p.s.i. That will pass post tech. ?
Compression ratio and maximum compression are two completely different items ! Camshafts, Valve timing also come into play when seeking cranking compression !:rolleyes:
 

badger999

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ok then, when they run a compression test in post tech, what is the max. allowable p.s.i. comp?
 

D-rek

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The compression ratio of an internal-combustion engine or external combustion engine is a value that represents the ratio of the volume of its combustion chamber; from its largest capacity to its smallest capacity. It is a fundamental specification for many common combustion engines." from wikipedia
The psi compression check that you are referencing has nothing to do with compression ratio. This test is to determine the condition of an engine not the compression ratio
 

vw2nut

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so if you do a compression test on 4 class nine motors and they all come up 120 to 125 pounds and then you do 1 and it comes up 145 to 150 you are sayin that it could be legal.
i dont think so:cool:
 
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If the first 4 have burnt valves or worn rings and the other does not, then I think so.

Make it even simpler: on the same engine, three cylinders have 120 to 125 compression and the fourth has 150. Is there any reason to think the compression ratio is different in the fourth cylinder. "i dont think so:cool:

There is no direct correlation between Compession and Compression Ratio. What they are doing at Post Tech is "P&G" tests, checking displacement only.
 

Mean Dean

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Tech uses a product called a "ringer" developed by NASCAR to verify their 9.0:1 compression rules. It screws into the spark plug hole with the piston at TDC and electronically measures the volume of the combustion chamber.
 
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