Hello,
Had a nice weekend with "RoXanne", my 2009 RX-8 GT (82,900 miles). Only had her about 2 months so this was the first DIY service I've done to the car.

• Replaced motor mounts (OEM)...the old ones were sitting on the brackets....measured them on the bench compared to the new ones and they had about 4-6mm of "sag". Driveline feels smoother.
• Changed manual trans and diff fluid with Royal Purple 75w-90. Trans oil looked good (only had about 1,000 miles since clutch replacement) but the diff oil looked ugly with some fine metallic particles on the drain plug...might've been original oil? Probably change it again on next oil change just to make sure it's clean.
• Changed engine oil with Royal Purple 10w-30. I've put about 1,500 miles on the car since I purchased it in March...last oil change is unknown so I figure I should do all these fluids at once and know for certain when they were changed.
• Replaced battery. Car was randomly setting off the alarm since yesterday and one of the symptoms was a bad battery (had just changed the batteries in the key fobs). Alarm hasn't gone off since.

OK, compression test with the "rotarycompressiontester.com" tool that I just bought last month...here are the numbers:
Front rotor raw numbers in PSI: 126, 125, 98 @ 376 rpm.
Front rotor corrected PSI: 94, 94, 73
Rear rotor raw numbers in PSI: 135, 135, 125 @ 361 rpm.
Rear rotor corrected PSI: 105, 105, 97

Lead spark plugs were a nice light tan. Didn't check the trailing plugs.

Are these good values for an engine with 83,000 miles?
I'm curious why the numbers are low on the 3rd rotor "face" in both chambers?

Thanks,

 

376 rpm sounds like WAY faster than normal starter speed. A little weird. The S2 2kW starter turns the engine at about 290-300.
If the rpm is off, the corrected results are also off. May want to validate the rpm with an OBD reader.

That said the corrected results if true are about par for the course for 83k. There is no schedule on which engines start to fail, but like any random-but-eventual process, they have a half-life. 83k is "mature" for a renny. Some don't even make it that far, few survive to 200k.

 

376rpm is really really fast for the S2 starter as Loki mentioned. My 2KW starter turns at around 290-310rpm.
You want to make sure that your trans fluid is not GL5. You want GL4 in your trans.
The low compression face might be caused by a worn or stuck side seal/ side seal spring.

 

I would love nothing more than to have those kind of numbers.

I get over 360 rpm from my $90 14t ebay starter and optima red top battery.


While my compression is very very sad, my last resort before an oil change was to add a little zoom zoom cleaner/ or seafoam while the car is running via the "jet air nozzle system" pictured here on the intake accordian tube at 12'o clock. It should be painted white, do at your own risk, I went with seafoam in my gas and oil as well because my engine is on its last life and I change the oil often.


https://www.rx8club.com/series-i-tec...eaning-217177/


Next I went on the twisty backroads and probably got about 20 redlines in before coming back to do another compression test and had some results. 5 psi but felt much smoother afterwards especially noticable when engine braking.


Since you just changed your oil my other suggestion is to beat the living daylights out of her...

https://black-halo-racing.myshopify....eos-75w-90-uoa

 

Maybe you're battery was fresh off the charger at 14V?

 

Any way to address said worn / stuck side seal without a rebuild? I had one low rotor face reading (out of 6) as well at 80k miles. Everything is still within spec right now, but that one low reading is borderline by Mazda standards after normalizing so I'm curious as to if more hard driving will help "unstick" it haha.

 

Hard driving does help, but you could try spraying some Marvel Mystery Oil in the spark plug holes then crank it a little bit, spray more ect. Get good coverage in the rotors and let it sit for at least 2 to 3 hours (overnight is better). If your issue is stuck seals, this will help, no guarantees though.

 

the 25 psi difference between faces is pretty large. the starter rpm is insanely high also; the charts with results don't even go that high.