Compression question after build and break-in?

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Mar 2, 2010 | 12:42 AM

#26

FDSeoul

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Corea FD

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From: San Diego

Compression Numbers level off and reaches their maximum compression as co-efficient of thermal expansion of metals are a factor.

Heat forces all materials to expand, especially in our case making the metal seals seal tighter.

Mar 2, 2010 | 09:55 AM

#27

Rx7aholic

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From: Morris Plains, NJ USA

Quote:

Originally Posted by GoodfellaFD3S

Khris, those readings come out to F 103/103/99 R 99/95/102 at 250 rpm. That's on a stone cold engine too, so the readings would be lower if thoroughly warmed up as it should be.

Those are new rotor housings? Who built it? For new housings and apex seals that's not horrible for a completely fresh build, but not great either.

Hey Rich, what I meant to say is that the egine had total of two hour and half running since it was installed, and it was warmup for aleast 30 minutes before i did the compression test, again I have not driven the car yet, btw Jim (aka JPR imports) build the motor for me.
Khris

Mar 2, 2010 | 11:22 AM

#28

R3AL.CH1CK3N

Jesse

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interesting, nice thread Mike.

Mar 2, 2010 | 06:49 PM

#29

FDSeoul

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Corea FD

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From: San Diego

Quote:

Originally Posted by R3AL.CH1CK3N

interesting, nice thread Mike.

Beside, educating myself along with the rest of the community, I really was hoping to provide some crucial rebuild info for those dropping K of $$$ on the engines on what to watch out for.

Mar 2, 2010 | 11:59 PM

#30

arghx

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From: cold

just keep driving the car

Mar 3, 2010 | 02:53 AM

#31

WaachBack

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From: Hawaii

I wouldnt really worry much about compression numbers unless your car is having major problems starting due to low compression. Like stated above, just keep driving the car and dont worry about it.

Mar 3, 2010 | 08:24 AM

#32

alexdimen

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From: Richmond, Va.

Quote:

Originally Posted by Rx7aholic

Ok gent's got my compression result, it's a rebuilt with new housing and everything else is oem (new) accept for R.A Super Seals and Pineapple Racing HD water seals and most important o miles on the engine just about 1:00 minutes total running since it was put in.
The compression was done with Mazda digital compression tester.
Front Housing Result:
Rpm= 276
1=7.9 kpsi
2=8.0 kpsi
3=7.6 kpsi
Rear Housing Result:
Rpm= 263
1= 7.2 kpsi
2= 6.9 kpsi
3= 7.4 kpsi
I was too lazy to look up to psi I thinkt he book call it kpsi? maybe some can chime in.
Khris

lol, you would need a compression ratio of 550:1 to make 8 kpsi! Those readings are in kilogram force per square centimeter.

Mar 3, 2010 | 11:44 AM

#33

Rx7aholic

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From: Morris Plains, NJ USA

I am not worring about my motor, I was just repling to FDsoul thread about a compression are after a rebuild and I was sort of curoius myself. Also I knew what parts went into my motor. I can wait to start driving it on the road.
Khris