I kinda have an urgent question and call on the forgiveness and grace of the admins and other members.
I have an 04 with 130,000 miles (original motor) and got a compression test and failed. actually pretty badly, face three of rotor 1 is at 56 psi, with about 66-68 on the other two faces.
rotor two is at 70-72 psi. So my average compression being around 66 psi many would condemn the motor and rebuild it or replace it. But i am experiencing no problems starting hot, idling, or major power loss symptoms and have actually been getting great gas mileage and no abnormal oil consumption.
bottom line is, I don't have money for replacement or anything right now so i need thi to live until i have money for some options and i need honest opinions from you awesome people!
Any help would be greatly appreciated.

also...i'm curious what you all think about the test results given i have absolutely no issues with the motor although it should be just limping around right now right?

 

I kinda have an urgent question and call on the forgiveness and grace of the admins and other members for any flaws in this thread...

I have an 04 GT M/T with 130,000 miles (original motor) and got a compression test and failed. Actually pretty badly, face three of rotor 1 is at 56 psi, with about 66-68 on the other two faces. Rotor two is at 70-73 psi. So my average compression being around 66 psi many would condemn the motor and rebuild it or replace it.
But here is where my problem is, i am experiencing NO problems starting hot (have upgraded starter from 06 models), have NO idling issues or stalling, or major power loss through the gears and have actually been getting great gas mileage (about 18 in town with regular redlines), and no abnormal oil consumption.
Bottom line is, I don't have money for replacement or anything right now so i need this to live until i have money for some options and i need honest opinions from you awesome people!
Any help would be greatly appreciated.

also...i'm curious what you all think about the test results given i have absolutely no issues with the motor but the numbers (as well as mazda techs) suggest it should be just limping around right now on it's last mile.

Thanks again!
Vincent
shokwave23 is online now Report Post

 

If your not having any problems I would keep driving it. Why not right? Youll need a rebuild at some point anyway. Im not familiar with the numbers you have provided. Normally they are single digit numbers 5,6,7,8. Something like 7.6, 7.8, 7.8. You should have 3 numbers per rotor. Did you get numbers in this format at all? You also need the cranking RPM for the motor. Was this done at a Mazda dealer?

 

Those numbers are low enough that you should have significant trouble at any low RPM and starting hot and cold. Since you don't have any trouble, I would suspect that the test was performed incorrectly, and your numbers don't mean anything useful.

You also didn't include any RPM information and if it was corrected for RPM and altitude, so the numbers may be right, and they just haven't been corrected properly.

Note though, "average compression" isn't used at all. If you have only 1 face below the minimum line, the whole engine is considered failing.



Chrishoky:
PSI is a valid compression unit of measure. The dealers use KPA or kg/cm2 typically, but PSI and BAR are two other units of measure that may be used as well. My compression chart (https://www.rx8club.com/attachments/...sion_chart.png) has all 4 on the left, though the main grid area of the chart uses kg/cm2.

 

It was done at the dealer. Those numbers are in psi however they were originally in KPA. i'm going to copy all of my results shortly, including rpm and such.

 

That is where I am confused, other people said their engines started working badly at 550 kpa and stopped starting entirely at 482..
My starter spun up to 272 rpm. The test compensated for that, but i will include both numbers. I wasn't told about any altitude compensation. I live in West Texas, being flat dry desert I'm guessing they didn't think it mattered...
They got me an estimate on a new engine, oil & filter, coils, front alignment, and other bullcrap stuff that came out to $8,300 . For that much I'll buy a 3 rotor and pay to have my other shop convert it.Probably with some money to spend on my own oil and filter

Here are my test results:
Rotor 1 272 rpm
Port 1 481 Compen. (250 rpm) 437.91
Port 2 485 Compen. (250 rpm) 441.91
Port 3 434 Compen. (250 rpm) 390..91
Diff. Port 51

Rotor 2
Port 1 543 Compen. (250 rpm) 499.91
Port 2 527 Compen. (250 rpm) 483.91
Port 3 542 Compen. (250 rpm) 498.91
Diff. Port 16.

Diff. no1/no2 93

Again, no difficulty starting cold or hot, no issues sitting at long red lights, no issues getting up to 9,000 rpm on a nearly daily basis, no idle shakes, if anything when i am sitting at a light with the music turned up i can't even tell the engine is running at times. And that's with my rather noisy muffler delete..

 

Then I'm inclined to say that the test was performed incorrectly and your compression is actually higher than that.

 

I'd like to think so too, I was just hoping it's not wishful thinking.
Is there anything I can do for it myself here at the house, or on the road, that could put that theory to the test?

 

I'd probably go get another test at a different dealer (or get one at a rotary shop, if there is one in the area, unsure but i seem to remember one down there in TX)

When I had my first compression test done, it was absurdly low like that. I drop 90 minutes away to another dealer 3 days later for another one, and I passed. 6 weeks later I got another one, and the scores were even higher.

 

Okay, yeah I'm sure there is in a state this size, including a good 7 or 8 hour drive and a day off work to get there.
I could find another dealer within a couple hours, and i might check into that when i get some more cash for the test and for gas.
I imagine a properly done test would produce some higher numbers, but in your opinion, what would you expect from an 04 engine with 130,000 miles with the behavior that I've mentioned? I don't think the engine is perfect, but its definitely not as low as they said...

 

If you are gettin 18mpgs, and able to start hot and have no issues redlining what so ever then my best guess is your engine is in good order and the compression test wasn't done properly.

I am not that experienced and still in my learning mode, but our compression shouldn't be in psi it should be in kpa, though you convert from psi to kpa.

Where did you get the compresson test done?

 

I'm thinking the same thing, I just wish that for the money it would have produced some accurate results.
I converted it to psi earlier for the sake of my own convenience and when i typed up my first post those were the numbers i still had, It wasn't until later when i had access to the papers Mazda gave me at the dealership when I typed up the kpa.