De carbon opinions please....with explanation
 

05 with 27k miles. Runs very well,engine sounds and feels good, however I noticed it does 0-60 in 8 seconds as opposed to 6 seconds in others I have driven. Kris,whom I met on this site did a compression test for me. One rotor passed, the other failed. The results in psi
rotor 2 front
Face 1: 67psi normalized: 106psi
Face 2: 70psi ....................111psi
Face 3: 68psi,.....................108psi 198 rpm normalized to 250
Rotor 1 rear
Face 1: 72psi,.....................90psi
Face2: 74psi......................93psi
Face3: 75psi......................94psi 292 rpm normalized to 250 and altitude to 7000 ft +

We discussed the possibility of ATF/seafoam/zoom cleaning. Kris said it may help, it may not.
I researched the forum on this and the one thing emphatically stated by someone was this should be a LAST RESORT. I kind of like the ATF cleaning because you could leave it in for a couple of days. However one person said that ATF has no detergent properties at all although others disagreed. My 2 cents....brought my Tundra in for a tranny flush at 177k miles. Took it to supposedly the biggest and best place in Colorado. He recommended doing a filter change and replenish half the fluid as the detergent in the ATF might clean out too much and create problems not currently showing up.

What are your thoughts on de carbon at this point. I'm not at a last resort point yet. Should I wait until the compression gets worse and keep driving it for now?

FYI....We put in New plugs after the test. The car is running and accelerating a little smoother. A little faster too. 0-60 in 7 seconds instead of 8.

Also, the car has no other symptoms of low compression based on my research here.

failing compression is failed compression period. you may get a tiny bit back but only a propper rebuild will restore compression. if you want to try it just use distilled water. RIWWP (a mod here) did a comparison on different "cleaning" methods. go out and drive the shit out of your car redlining often, it may "help"

Distilled water using the same method as ATF? In the spark plug hole? I wondered if red line more often might help. Also previous owner had it for 11k miles and pre mixed less than 1/2 oz/gal every other tank whereas I do 1/2 oz every time.

distilled water in the lim vac ports while the engine is running

You are assuming carbon is your problem here.

There are a lot of things that can cause low compression.

Like 200 said, you are really just delaying the inevitable. Once you have low compression, all the wear will accelerate from the blow-by gas.

What other things that cause low compression beside the apex seals.

side seals, corner seals, water seals, bad cracked housings/irons

Is that a typo or is the rpm in the rear rotor results 100 higher than the front results? I assume typo, but never know...

I wouldn't wait to do treatments. It's definitely not going to get better on its own. They may not help, but they definitely won't if you don't do them.

Failing compression at 27k miles? Ouch.

Just to double check: what kind of altitude do you live at? That can have an effect as well.

Yes....ouch! I asked Kris about the rpms. He said the readings were accurate. He is not sure why the difference. I'm wondering if it had to do with the starter. It's the original wimpy one. We tested at 7000 ft. Kris normalized for the altitude and rpms.

Was able to track down the original owner. He had the car 8 years and put 14k miles on it. Always garaged, constantly checked oil level and changed the oil every 6 months regardless of miles driven. He didn't know about Pre mix or red lining. Basically he babied the car.

Second owner did pre mix every other tank. Not sure how often he red lined. He was very meticulous and kept it garaged. I will call him to find out how often he red lined.

Based on the cars history, it doesn't sound like the seals are worn but more likely it is carbon build up as it was babied, not driven the way you are supposed to drive it. Neglected maintenance plus high use would most likely cause seal wear. This is not the case with this car.

Tonite I red lined the crap out of it. Will do this for a bit and then probably do another compression test. If little or no change, then I will probably do the de carbonization thing. Hopefully I can restore a little bit of health to it.

a lot of 04/05 8s had very early engine problems. i bought mine at ~40k, previous owner had engine replaced in 2006 with about 25k

If you redline, you should pull some in 2nd and if safe, 3rd. 1st gear redline doesn't help much since the duration is too short.

Earlier 8s also didn't inject enough oil into the chamber. You might wanna check with a dealer to see which ECU flash you have.

And even if carbon buildup is the issue here, there's not much you can do about it, really. Once it's there, it's very hard to get rid of it short of a rebuild. And you don't want too much of it coming off at a time, as bigger pieces of carbon can do quite a bit of damage.

You can try the water in the vacuum line or the Zoom Zoom kit thing, but even that's a very slow process,

The car runs very well. Engine is smooth and pretty quiet. As long as it drives well with no starting issues, is there any reason I shouldn't drive it until it craps out?

drive it. the only reason i wouldnt is if you are gonna get a rebuild and are trying to reuse all irons/ housings but a mazda reman is still probably cheaper anyway. i say drive the shit out of it

Can you hold in 2nd gear at 8000rpm for a short period ?

Correct me if I am wrong, but engine load is a pretty important part of the equation here.

When you floor it in gear, your engine will have a very high load as it's trying to accelerate the car as hard as it can. High load + high rev = good for the engine. As long as you are not lugging the engine, it's fine.

However, when you hold the RPM constant, the load drops to very low as all the engine has to do is just fight against frictional losses, air resistance or whatnot. It doesn't need to accelerate the car, though. Low load + high rev = bad for the engine.

Same idea as revving the car in neutral. There is almost no load on the engine, so other than showing your car off to your friends or rev-matching(which lasts fairly short anyway), don't rev it in neutral. Not to mention, this is pretty taxing on your cooling system as well if your car is still.

These also apply to any engine, not just rotaries.

I went thru the service records !looking for the updated ECU flash regarding the oil injection. The only thing I found was reprogrammed PCM in Sept 06. Could that be the updated ECU flash?

Ok, contacted local mazda dealer and they verified the ECU flash was updated in 09.