Hey guys, I had a compression test done at a local dealership, then I came on the forums to see how the results stack up against the others. They told me my engine is ok, and I have nothing to worry about. But then I found out my results are presented differently than the others. Did my dealership did the test correctly?

Rotor 1: 87 psi/600 KPA @ 1500RPM
Rotor 2: 70 psi/480 KPA @ 1500RPM

My car is 2006, with 76,000 miles (122,500 km)

 

What.

The starter can't spin the engine at 1500RPM, so whatever they measured, they measured wrong. there is a Mazda procedure for this, there are no excuses for not following it.
The Mazda machine provides 3 numbers @ 250RPM. If they didn't provide you 3 numbers, they didn't provide the service you paid for.

I had a local dealer offer me something like that (although not at 1500rpm, wtf), because their machine was broken. I complained and didn't have to pay for service not provided. Suggest you do the same.

 

I'd double check those numbers. Typically the engine RPM is roughly in the 250-300 RPM range, depending on how strong your starter and battery are. I very serious doubt any RX-8 started can spin the engine up to 1500 RPM. You should also have 3 pressure readings for each, 1 for each rotor face.

 

The thing about the rotary engine is that the compression can vary greatly depending on the RPM, unlike a piston engine which will have relatively the same compression regardless of the RPM.

So with a rotary, even if you have really bad compression, if you rev your car up high enough, it might feel just fine to you.

That's why you need 2 cranking RPM(one for each rotor) to go with the normal 6 numbers you get.

Demand a proper test with the proper tool. And you probably want to find another dealer or a rotary shop next time. They sound like they don't know what the **** they are doing.

 

Was this done at an official Mazda dealership? It not, they likely performed the test wrong.

 

I appreciate the insight. Sadly, it was a proper dealership, Mazda of Toronto, in fact. Too bad I didn't know enough to point it out at the time. I'll definiately go back and ask for what I paid for.

 

Here is what the Mazda OEM tester looks like:


Mazda should provide the results in kg/cm^2, with a valid RPM reading (between 200 and 300RPM).

Here is a table cross-referencing compression results against RPM to determine engine health (Bold line is Mazda's threshold for a rebuild based upon compression results)

 

I recently bought a 2010 RX8 R3, I paid to have it tested before I bought it ( Amarillo TX) I live in Oklahoma City. At the dealership in Amarillo my #s were 620ish to a high of a 680s. Mazda USA arranged for me to bring to OKC dealership because it was under the 8 year 100k warranty.
At OKC Mazda Dealership it tested 710ish to 780ish alk tests were minimum 254 RPM. Now my motor tested "pass" and "fail" is 599 Kpa and down
I was not content with this outcome and called Mazda USa to allow a third test at another dealership, my #s were 630ish to 680ish, but was told Mazda says 690kpa and down is fail. Either way I now have a new engine coming under warranty.......
but I feel your pain

 

YUP!!! 690 it is!!! TY!!!

 

Could be that the second dealer did it when the engine is cold. If it's cold, the compression numbers will be higher.

 

Yeah for sure, it's just scary I could have missed a warrantied engine!!!! And they were unaware of the KPa threshold as well, so even if it yielded in the 600s they would not have pursued a replacement. I am having clutch and all 6 oil injectors done as well. Only have 71k but might as well.