So, I've been trying to determine the condition of my engine for some time.
The compression tests I've had done by Mazda appear to me to fail, but they say the results are fine. My last compression test came out:
6.8, 7.3, 6.6 rotor 1
7.2, 6.9, 7.2 rotor 2
test RPM 302

I've been arguing with my dealer as to whether those are good numbers or not. To me, and the manual I have access to, they seem to fail, to the dealer, they say it's in excellent condition, and a 'average-good motor would test 4-5kg/cm' which they can't substantiate.

I just had it dyno tested, and it came out with what looks like some descent numbers to me.



That was on a Mustang Dyno. Engine is stock with a K&N filter insert.
Test conditions: 23 deg C [74F], 50%RH, 238m [781ft]elevation

The max HP was 199.4, which they have as 202.7 with correction factors. It pulled a little better when the engine temps were cooler (pulled a 209) but the graphs also had some noise which makes it hard to read.

Is that the correct WHP of a healthy engine? If so, why would my compression numbers be so low? Also, is there anything I should look into which is causing the drops in power you can see on the graph (at 6300 and 7300 rpm)?

 

So, I've read through (most) of the Dyno compilation, and it looks like the power drops are normal.

https://www.rx8club.com/showpost.php...&postcount=598

The scale on my graph is off, but similar results to the linked one (ports?).

Does anyone have any ideas on the discrepancy between the compression test (which looks bad) and the dyno results (which look good)?
I'm trying to find a way to periodically monitor the engine to make sure it's still in good shape. The dyno should be a good way to judge overall powertrain health, but the low compression numbers still concern me.