Paul_in_DC

The same is true of my local club and folks I've met at the track. The only place I've heard of engine problems is in these forums.

MrWigggles

They are simply sharing shower water. Just two girls who are environmentally conscious.

Maniac probably got the image from Greenpeace or the Sierra Club's website.

-Mr. Wigggles

MazdaManiac

iTrader: (3)

That is because you don't live in the desert, which is where the failures are happening.
Now you could say "move", but that wouldn't help all the other potential Mazda customers in the 5th largest city in the United States, amongst others.

More than half of the '8 owners I know in Phoenix and Vegas have replaced their motors at least once.

RX Guy

Just did a compression check this past Friday. Though I'd contribute.

Rotor #1 @ 258 rpm
132.675 to 137.895 psi

Rotor #2 @ 256 rpm
134.27 to 140.795 psi

DynoJet done a couple months 170's hp/130's tq
Car is 2004 Aug manufactured. 20,000 mi. (yes, weekend only street car) Pretty much stock powertrain except for MS CAI and RB ignition wires.

MazdaManiac

iTrader: (3)

Wow! That is extremely high! Then again, you list a range rather than a set of numbers, so your testing method is suspect.

rotarygod

I've never seen numbers anywhere near that high.

MazdaManiac

iTrader: (3)

Mine were around that (9.1 or so - 130 PSI) right after I did an ATF de-carbon, but that was before I ran the motor, so it was still soaked in oil.
It immediately dropped to ~8.3 (120 PSI).

RX Guy

Here is the print out from the dealership where the work was done. I wanted the compression test since the warranty is ending this month.

Yeah, I have mixed feeling about this test. Happy for one. But that 140 psi (for one) is suscipiously high.

MazdaManiac

iTrader: (3)

That's fantastic. That motor should be putting down a TON of power.

RX Guy

And yet. the car only dyno'ed at 180 hp.

r0tor

iTrader: (1)

...because a compression test and power are not always related (as long as you don't have something really wrong anyway...)

MazdaManiac

iTrader: (3)

All other things equal, compression = power. (Up to a point, which is the point indicated by that readout!)

r0tor

iTrader: (1)

but compression at 7,000 rpms does not equal compression at 300 rpms... which is why compression at 300 rpms does not equal power

MazdaManiac

iTrader: (3)

Why do you talk out of your neck sometimes? Stop inventing stuff just to confuse people.
Compression is compression. Pressure changes at RPM. There is a direct correlation between compression pressure and RPM. There is no magical "breakdown" of pressure at some certain RPM.
Its not like he is going to have mammoth pressure at 250 RPM and suddenly have nothing at 7000 RPM.
If that were to happen, he would then have nothing at 250 RPM also.

dznutzuk

How's this for some great numbers--- rotor 1 :619,635,663@ 224rpm's --- rotor 2: 659, 673,701 @228rpm's! And yet Mazda Greece-Europe says it's fine and won't change the engine!Bastards! BTW the car is totally stock 2004 Cosmo, always has been and is a street car with 39000km and runs like ****!

r0tor

iTrader: (1)

fine... you can ignore the fact that at 7,000 rpms you have an increase of centripetal force, oil injection, and heat over the conditions at 250 rpms - all 3 of which can increase compression in a rotary engine (unless you have a significant problem)

...you can also ignore the fact that every RX8 long term tester (like car and driver's for instance) finished the stay being significantly quicker then when the car was brand new... i guess their engines must have gained compression over time -yawn-

MazdaManiac

iTrader: (3)

Or that you might have a net decrease in oil injection (depending on load), charge inertia reducing effective sealing, decreased charge time allowance yielding less gas to compress, lower VE, etc.
None of it matters.
We are talking about static compression ratio.


Not a single one had a dyno to back that up and that idea runs contrary to the fact that many of these motors are loosing compression over time. and are dynoing significantly lower than anything near the rated power of this car should.
All of which is irrelevant to the discussion, so enough with the red herrings. No one is buying your nonsense.

joff

My compression check from last Friday. (17000 mi 2005 6MT sport). We did three runs per rotor separated by about 20 seconds.

Rotor #1
run 1: 9.0 7.7 7.8 -- 277 RPM
run 2: 8.7 7.6 7.6 -- 285 RPM
run 3: 8.6 7.6 7.6 -- 286 RPM

Rotor #2
run 1: 8.8 8.6 8.8 -- 290 RPM
run 2: 8.8 9.0 8.9 -- 290 RPM
run 3: 9.0 9.0 8.8 -- 291 RPM

Mechanic (Karl, RotaryMan25) said numbers looked okay compared to other RX8s he's looked at on his tool, but might be a bit of carbon on rotor #1. I've been driving the car really easy in the heat this summer in Phoenix.

Interesting to see the variability between runs without changing any variables involved in the test. Makes me wonder how accurate these testers are? Perhaps part of the "margin" included in the max/min ratings from Mazda are partially used up in imperfections in test equipment/test environment and not just motor tolerances?

two rotors

True,but of course you know that all other things are very rarely equal!

MazdaManiac

iTrader: (3)

Absolutely true! But the point was that if you simply had higher compression in the same motor (magically) you would have more power.
Unfortunately, pr0bed has a love for over-complication. I suspect his inner monologue is a bit of a Rube Goldberg contraption..

No. Its the RPM difference and the gradual loss of heat from the motor.

Your #1 has a stuck or damaged apex seal.

LionZoo

Slightly off topic, but are your dealers doing the compression test for you guys for free?

joff

No. But you can probably expect to pay between $50-150 for the test as its about 1 hour of labor with the right tools.

tdiddy

I am going FI this winter so I thought I would run a compression test. I also had my coils checked and they were fine. Here are the results...

Rotor #1 - 9.6, 9.9, 9.7 at 274 RPMS
Rotor #2 - 10.0, 9.8, 9.7 at 270 RPMS

I am pleased. My car has 22618 miles. I use Castrol GTX 5w30. I run 90 octane with 6oz of premix per tank. Currently, running Penzoil Marine because I ran out of Idemitsu and couldn't get anymore. Now for a couple of baseline Dyno runs....

nycgps

iTrader: (1)

Stop using Premix for at least couple of tanks before you do your compression test ...