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Compression Test

morto86

By morto86,
in General Maintenance

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Missileman Veteran

Missileman

Posted
Posted (edited)

On a warmed engine with all sparkplugs removed, with accelerator fully depressed and a charge on the battery capable of cranking the motor at 300rpm.

RB20DE/T/26DETT

New = 170psi

Low Limit = 128psi

Max cylinder difference 14psi

...from engine workshop manual.

Edited by Missileman
Ben C34 Grand Master

Ben C34

Posted
Posted

I just got the reply 210. Cold. Does this mean the head has been shaved previously

No as the comp ratio doesnt effect the compression test. it just ensures the rings and valves are sealing as they should.
Ben C34 Grand Master

Ben C34

Posted
Posted

Def 200 all round with snap on gauge and warmed engine. With researsh this proves the comp ratio therefor is 10:1. As for the knob who said the comp is not relayed to the ratio. Actually write out the equation.

Settle down. explain to me how an engine when built has a certain compression test result, then when worn had a lesser compression test result? Did it's comp ratio drop? can you run more boost cos it has less comp ratio? NO. explain how comp ratio effects the comp test results please :)
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted

Settle down. explain to me how an engine when built has a certain compression test result, then when worn had a lesser compression test result? Did it's comp ratio drop? can you run more boost cos it has less comp ratio? NO. explain how comp ratio effects the comp test results please :)

Well personally I would have though it was obvious that the higher the compression ratio the higher the expected compression test result . The value of the compression test for measuring wear depends on knowing the original compression so as above if the stock factory figure was 170 psi then yes 130 psi indicates a lot of wear which can be confirmed with a leakdown test. My engine had 130 psi compression when built because of the choice of pistons (CR about 8:1) and leakdown test is within limits at 5%

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