Hey Guys,

Just got my first 8 (and first rotary) 2 months ago. 2007 w/ 13,900 miles. I have 1 month left on the powertrain warranty so I decided to have a compression test performed. The results are:

R1: L 95-psi T 95 psi
R2: L 95+psi T 95+psi

These tests are not from a dealer (nearest one is 2 hours away) but rather a local import repair shop.

The tech tells me the staandard compression should be around 120 psi with a minimum of 98.6 psi. He said the test was run between 250-270 rpm.

My current highway gas mileage is at 19.5mpg at speeds between 80 - 85 mph. (seems a bit low)

I have done some searching on here and havent found anyone with similar results so forgive me if this has been covered (but I just havent found it).

Obviously, i'm going to have to make the 2 hour trip to the nearest dealer but i'd like to get your guy's expert opinions on what my best way is to approach this. I'm assuming failing a compression test with this low mileage is not good at all and I should try to get the dealer to put in a new engine.

Everything on the car is stock. I know that replacing the coils, plugs and possibly a decarb will help but is that just putting a band aid on an inevitable engine failure some day?

Any advice would be much appreciated. Thanks.

 

Low compression at 13,000 miles is very low, and a bit of a cause for concern, although it's possible that the test was done incorrectly, which is more possible because the results aren't in the format really needed. You need 7 total numbers, possibly 8. You need a compression score for each face of each rotor (3 for each rotor), plus a crank RPM. Rarely does the crank RPM shift from one rotor to the next, so usually 1 RPM number is sufficient, though sometimes the RPM for each rotor is given.

Ignition health won't affect the compression scores however.

Your best bet is to just go to the dealer, ask for a compression test, and then go from there. Even if your engine is just fine, it's a peace of mind thing that is very much worth the cost of time and travel to get there and the cost of the test. It's not something you want to pass up on and find out you REALLY should have.

 

+ 1 sounds like they used a regular compression tester, not a rotary one. I'd say these results are not really reliable or meaningful.

 

Forgive my ignorance (like I said, first rotary ). What does +1 mean?

 

+1 in forum speak is "I agree with the post above". Derived from "adding a vote of agreement".

 

Haha. Yep, feel dumb now. Thanks.

 

Just made an appointment with the dealer on Monday to have the test ran. I will post the results here. Thanks so much for the imput so far.

 

Your results should look like:
Rotor 1: 7.2, 7.1, 7.1
Rotor 2: 7.3, 7.4, 7.1
@250rpm

Actual numbers may vary obviously.
The 250 rpm is important, the Mazda compression tester should be able to convert the result it sees at whatever rpm they test at to what it should be @250 rpm

 

Compression numbers in BAR or PSI are valid as well, but yes, that is the format they should be in.

 

Cool. Thanks. My appointment next week is with a rotary tech. Hopefully he knows more than the first guy. Results coming.......

 

Well, here are the results.

Rotor 1: 6.7, 6.7, 6.7 @ 293 rpm
Rotor 2: 6.8, 6.7, 6.5 @ 306 rpm

The Mazda dealership claims that these numbers pass. From the graphs I have seen I believe they do not pass. Any help?

 

Correct me if i'm wrong.
Any number below 7 (even if it's just one), means you need a new motor.
Get all your oil change records ready, you'll need those in order to get you a new motor.

 

With those numbers in hand, call Mazda North America. They ultimately decide, the dealer is just a middle man. The numbers do look low, corrected for 250rpm that puts you in the low 6s-high 5s.

 

That has failed. what your Mazda dealership been smoking?

Just look at this



if 98.6psi/680 KPa @ 250 rpm is BARE minimum. How the F can you pass when you are getting those numbers @ almost 300 rpm? with numbers like yours, it will put you to the low 6/high 5s @ 250 rpm.

 

unless this is a thread on Troubleshooting dealer incompetence it probably belongs in another forum area

 

+1

 

By any long shot of a chance.......Does anyone have a good contact person they have dealt with at Mazda North America?

 

That's mine when I got it replaced last year. Rotor 1 is at low, while rotor 2 is way below the minimum, you can see on the right-most column where it says 'standard' and minimum' since yours is below minimum; tell your dealership/ mechanic/ service adviser --> you don't a lawyer or English teacher to tell you what it means when it's below average. They should get it Warrantied FOC.