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Rb20 Compression Test.

odessy

By odessy,
in Engines & Forced Induction

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odessy Enthusiast

odessy

Posted
Posted (edited)

Compression tested my engine today with an el cheapo sca gauge and here are the results.

1: 140(D) 150(W)

2: 135(D) 140(W)

3: 145(D) 150(W)

4: 135(D) 145(W)

5: 135(D) 140(W)

6: 145(D) 145(W)

I did warm the engine up but by the time I got the top pipe off and the coilpacks out it had cooled down a bit. Engine seems fine when driving but is doing weird things when idling (Randomly dies after 5-10 mins of stationery idle.)

Thoughts?

Edited by odessy
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https://www.sau.com.au/forums/topic/407291-rb20-compression-test/
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The Dan Grand Master

The Dan

Posted
Posted

Yeah, they're low, but not very low, and the lowness could also be the function of engine cooled down a bit or the cheap gauge. So, not to worry.

I'd be very surprised if you could find another RB20 that's over 140psi.

Those results are perfect.

RB25's are usually around 155-165 but RB20's have a lower comp ratio and that gets them around 130-140.

The Dan Grand Master

The Dan

Posted
Posted

When my old RB20 was much newer it came in at 150ish. 10 years ago! No idea what it is like these days, but the motor was still just as strong, so I wouldn't expect too much wear.

I have comp tested dozens and none ever exceed about 140. That's not to say they can't though. Even brand new engines I've tested come in at that result. Increasing the static comp ratio will also effect that result. Was your old RB20 modified possibly?

GTSBoy Grand Master

GTSBoy

Posted
Posted

Not modified, to best of anyone's knowledge that is. Was always a strong car though. When JMS imported it in 1999 they said it was the fastest standard one they'd had come in. But everything else about it was 100% standard, so I'd not suspect that anything was different inside.

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