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Compression?

KLA#ZLA

By KLA#ZLA,
in Engines & Forced Induction

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KLA#ZLA Contributor

KLA#ZLA

Posted
Posted

i've been looking for an r32 gtr for a while now n ive seen a few differences in the compression ratings for some cars, i dont really know much about compression rating but im guessing its got to do with the amount of pressue the engine can with stand maybe? but anyway im guessing higher is better, ive seen cars ratings from 140-150 so just wondering what is a good rating and what is bad?

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deant1 Collaborator

deant1

Posted
Posted (edited)
i've been looking for an r32 gtr for a while now n ive seen a few differences in the compression ratings for some cars, i dont really know much about compression rating but im guessing its got to do with the amount of pressue the engine can with stand maybe? but anyway im guessing higher is better, ive seen cars ratings from 140-150 so just wondering what is a good rating and what is bad?

a consistant one. anything that reads simiular pressures through all 6 is good. obviously excessively low would be you'd never come across a very low reading that is consistant throughout anyway.

Edited by deant1
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Beer Baron Grand Master

Beer Baron

Posted
Posted

up to 15psi variance from the highest to the lowest is acceptable. 5-10 psi variance is 'desirable' though.

figures above 135psi for the lowest is important. expect a healthy engine to be around 14-150 and variance of not more than 10 from lowest to highest. don't worry too much about the outright numbers as peoples test procedures are not always the same (hot engine V cold engine, strong battery? strong starter? how much throttle?, type of gauge?, how many cranks? etc) and all those things will affect the figures.

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GeeTR Grand Master

GeeTR

Posted
Posted (edited)

Could anyone hazard a guess, as to how much of a difference testing a cold motor would have on results?

I tested an RB26 that hadn't been started in 4 months... needless to say, the results were disgraceful, with lowest 125PSI, highest 140PSI.

Should I stop worrying and wait till i can test again when hot and oiled?

Edit: Grew another testicle... tough now, for news either way

M

Edited by GeeTR
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luke gtr Grand Master

luke gtr

Posted
Posted

u can go to a mechanic, or buy the gauge from auto one/repco/any tool sellers. i think u can buy a kit from the brand ABW for around the 50-100 mark. lets face it, it'll probably be used in the future. im a mechanic, and had to use mine when my timing belt tens. pulley gave way.

if the engines got slightly low compression, squirt a little oil in the cylinder, if the pressure comes up, the rings will need replacing. if not, it'll cost more...

to test, remove all spark plugs, screw in gauge, and let crank for aprox. 4 times. dont 4get to disconnect the coil packs.

hope this helped.

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