So a friend let me borrow the Mazda rotary compression tester and I was able to get a few readings today.

4.9,5.0,5.1 @ ~220 rpm on the front rotor
5.1,5.3,5.6 @ ~225 rpm on the rear rotor

Depressing eh? I know the spec RENESIS threshold is something in the high 6's? So according to my numbers, I have a terrible motor. But the thing is, it really does NOT feel like it. I know people will argue that compression loss is not noticeable, and unless you have catastrophic failure, you wouldn't be able to feel it but it just doesn't seem like my motor is in this drastic state. So I'm left with either taking the results for what they are, accurate, or I screwed up the test. I have slight reason to believe that the compression tester itself may be faulty because at times it would give me readings of 0.0,0.0,5.1.. etc.. random readings on either rotor and I would have to power cycle it to get it to work again. Maybe the pressure transducer? Not sure.. but at this point I'm hoping the test I did was just fubar.

With that said, there are certain occasions were the car will dip rpm on idle to ~700 but then it pulls itself back up. Slight stutters. If there is a real problem I am thinking the winter and cold weather is masking the problem.

So at this point my plan is to wait a little while longer and see how my car behaves and if I notice anything. I don't have a CAT on, so that's what's stopping me from going to Mazda right away.. but ultimately that is what I will be doing.

Anyway, what do you guys think? You folks that have experience with compression numbers and their implications, how would the motor "feel" if the compression numbers were really that bad? Input?

 

Take it to the track , give it a thrashing then retest ......

 

Try testing again those number are not good. From my knowledge anything under 7 is doomed.

Let some of the Rotary doctors give their input here. But I do think you should check it again with a different tester

 

That's low...but even..which is better than low and all over the place

Might want to try a Seafoam and a good hard thrashing see what happens....

 

It was seafoamed 6,000 miles ago. 32,000 miles on it.

 

Take it in....new engine time then

Might as well go for it..the new remans seem to be holding up well

 

You need a hand man ?

also your starter seems a bit slow. weak battery or old starter ?

"normally", the compression should be in the mid 7 @ 250 rpm. 2 rotors should be within 1.0 apart.

Seriously, when Kevin told me my engine failed I was shocked too, but hey, it is what it is.

 

nycgps, that would be great if we could do a compression test on your car this way I can rule out the compression tester itself being faulty. i guess that would also be a good time to see why my starter is so slow!

 

alz0rz, at what mileage did you start premix and heavier oil? What kinda driving do you do on a regular basis? I started at 34,000 (just got the car) and drive 75% freeway Purposely run up the revs every drive. Thanks..

 

I started pre-mixing 6oz of Idemitsu and changed oil to RP 5w30 as soon as I got the car at 25,000 miles.
Until recently I had been doing 75% highway, 25% city driving on every tank of gas.

 

We can try this some time next week. if u're free

 

give me a day and i should be free.. since I lost my job and all ;[

 

**** ... well ... get some rest ... things will be better tomorrow

 

Will my compression go up? :p

 

Dude about 10k miles ago my car was feeling kinda luggy. So I ran the gas down to e toped off with shell and premix jumped on the free way around 2am on a cold *** night with no one out and gave her a hard thrashing as they say.
Even with my race pipe I could see the black smoke coming out from behind my car as I hit red line from 1st - 3rd gear. It got to a point where I could not see it anymore and was doing about 90 to 120 mph with a z06. I went from one side of town about 45 min then back home another 45 min. She has been running strong sence. So every weekend I give her a nice hot flame on run on the express way and she likes it.
GL

 

hey alzorz nycgps - let us know how this goes? I'd appreciate your qualitative description of the car if in fact compression is low. I'm thinking of bringing my car in for a comp test, my MPGs are slowly getting worse (plugs+coils are fine), starting is difficult especially when warm. Power feels fine but thats why i'm curious if you can really notice poor compression.

I'm almost at 8 years old, so I need to check this out soon....

 

Does the rx8 need it's own compression tester or can we use one that is used on piston engines?

 

Omg I can't believe you just asked that. Does the rx8 have pistons? No! So what do you think?

 

....I didn't ask if it has pistons. I asked if we need a specific compression tester for rotary engines or can we use one that is used for piston engines.

 

Dude I'll let you borrow my cat if that's all that's keeping you from a new engine bro.

 

The rotary specific tester is recommended to get accurate readings.

 

Do a vacuum test. Nothing can screw those readings up.

 

do you know where I could buy a good one if needed? Im checking my cat today