jaedra

I have just had a compression test done on my 2007 RX8. The results in PSI for the 3 faces of the front and rear rotors are respectively 89, 87, 91, 92, 90, 90. What exactly does this mean?

jaedra

PS Oops! 2006 that should be.

Loki

iTrader: (1)

We need the rpm at which rhe test was done to make decisions with those numbers. 90psi @250rpm is failing. 90psi at 200rpm is borderline but OK.

Who did the test? Was this with a rotary tester or a regular one?

jaedra

I will ask the mechanic tomorrow, and provide more details then. Thank you.

jaedra

I talked to the mechanic today who zaid it was a rotary test and also that the result meant the car is okay right now but will need a rebuild before too long. He said to watch for hot start issues which will be the signal.

alterego

Parts that are re-usable now have the potential to be made un-usable if you run it until it becomes hard to start. With proper care you can still drive happily with low compression, but you will have to accept the reality of the car breaking down at some point.

If you daily drive the car and redline it often during every drive, it may not last more than a year. If it's only driven on the weekends, you could easily get a few years out of it.

Loki

iTrader: (1)

I mean. It's below Mazda's minimum spec. If you're not having hot start problems yet, that's great and the car may continue like that for some time. So while he's wrong about the engine being OK, I agree that you don't need a rebuild until symptoms start. In either case you don't want to rebuild your engine, you want to buy a complete rebuilt one done by a professional, or Mazda.

This is also a good time to figure out what killed your engine. Have the ignition coils and catalytic converter tested/examined so your new engine isn't inheriting current engine's silent killer.

jaedra

Thank you fot all your help. I feel much clearer now.

XDragon8

Not trying to thread jack, rather keeping things tidy. Hope those with engine build experience find this.

Just a few steps ahead of you on a rebuilt engine to OEM specs (no porting) after catastrophic engine failure at 100km/hr. Aparently very good good 2nd hand housings used as my very tired ones were toast. Most other parts installed were new for same reason (gets exxy). Compression tested at similar numbers to OP from new @300km and again at 1500km with slight improvement in compression normalized for 250 rpm and elevation.

Just wondering if not enough km on car to build the compression yet or otherwise. Thoughts? Will test again in another 1 to 1.5 k. It really is a super smooth engine with no issues and all rotor face readings are within about 3 psi within and between rotors. Could my tester just be reading low? Maybe. Back to back to back tests show only small changes in PSI.
Looking for approximate numbers expected on rebuilt engine and what they are likely to get to thereafter.

blue17

Being in Victoria i was wondering where you got the work done and how you found the experience.

XDragon8

Hi Blue. The engine rebuild is going great. I never got a response to the above questions here in OZ subforum or the repost elsewhere that gets heaps more traffic. Hmmmm... I will be keeping a very close eye on compression during the warranty period. All i have found out is that compression should increase after xyz km.
I am not into free advertising or public slagging either way. Feel free to shoot me a DM with a quick into and where u located and i will definitely get back to you. Cheers.