socalightning

I wanted to have a real compression check done before the extended warranty ran out, so at 57k miles I paid $73 and had it done. Here are the results from my paperwork:

Rotor #1 at 315rpm: side 1 = 8.9, side 2 = 8.6, side 3 = 8.0 (kg/cm2)
Rotor #2 at 304rpm: side 1 = 9.4, side 2 = 9.4, side 3 = 9.2 (kg/cm2)

<states> "COMPRESSION NORMAL AND ENGINE OK"

I did not get a chance to see my service advisor about the results and not sure of his credibility yet with RX8 service and issues. ...So my question is directed at any rotary experts here. Based on this data, is my engine healthy? ...I'm concerned especially about rotor #1 with one side being 8.9 and the other being 8.0 (kg/cm2), and the min/max spread 8.0 on rotor 1 to 9.4 on rotor 2.

Issues I'm having with the car are vibration at idle, especially with AC on. They also pulled some misfire codes and say 2 of my coils are bad - I ordered new ones and will replace them this week. They looked at the engine mounts and say they are okay, at least visibly. And I had a loss of power above 5k rpm (response went completely flat) when I drove out to the desert last week - 150 miles or more each way with the temps out there at 95 degrees. Power returned when I got back to cooler temps.

All updates have been performed including the recall but I don't believe they checked the engine (vacuum test) since I never complained about lack of power.

Thank you for your time and help.

Go48

Here's the page from the 2004 factory service manual. I have plotted your numbers on the engine cranking speed correction graph. For the most part, they are above the "minimum" which I assume is good for Mazda. And the difference between the rotor face readings and rotor-to-rotor differences are within spec as well. I guess the Mazda "standard" is for a new, broken-in engine that was assembled perfectly by a little Japanese man in tennis shoes.

I must say that those are pretty high engine cranking speed numbers. You must have the upgraded starter and a fully-charged upgraded battery?

socalightning

Thanks Go48! I guess I should get a copy of the service manual. Yes, I have the upgraded starter and battery. I appreciate you for graphing my results. Looks like my lowest reading rotor side (#1- 3) could be below minimum for that cranking speed (315rpm). So, do you (or anyone else) think the numbers are good for a 60k mile rotory engine??? I'm worried about getting stuck with a damaged motor having to do with Mazda's poor oil injection programming - I hope to go another 60k before rebuilding my motor.

Go48

Apparently Mazda considers your engine essentially above the minimum. I suspect that if you maintain the engine properly it should easily go another 60K. My guess is that--assuming a constant level of maintenance--the highest percentage of engine wear occurs during the early break-in and shortly thereafter period, say the first 20K miles. After that, things are looser and don't rub so hard. (I'm thinking of an analogy but won't elaborate.) If you plan on keeping the car that long you might want to add a few ounces of 2-stroke oil with each tankful of fuel.

BTW, see my PM.

socalightning

Nice analogy. Thanks again for the advice.

j9fd3s

we had a car come in recently that did something really really really weird.

it was flooded, we got it started, but it was running on 1 rotor. so we compression tested it, and one rotor was ok (in the 9's) other rotor was in the 5's, dead engine right?

mazda told us to put coils into it. we did.

engine is now fine. compression came up to specs, car runs fine.

ive been playing with rotaries since 93, but NEVER seen a bad coil change compression numbers.

i would consider your compression test numbers meaningless until you get the coils fixed.

also the motor mounts dont fail visually yet

swoope

iTrader: (5)

easy,

flooded motor wiped out all the oil in the chamber... compession test was done before the motor was run.. with new coils. now the plugs fire and that rotor is not in a constant state of flood..

start motor apex seals get oil, compression comes back...

beers

TeamRX8

iTrader: (25)

it's all in the training ...

8is>enuff

My dealer did the same thing. Good thing they didn't charge me for it. They still claim to not have the tools necessary for pressure@RPM.

My previous dealer once did a compression check when the engine was cold. Man were those numbers shocking.