Compression test results without multiple pressure figures
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.
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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 fook they are doing. |
Was this done at an official Mazda dealership? It not, they likely performed the test wrong.
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Thanks guys...
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.
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Here is what the Mazda OEM tester looks like:
https://www.rx7club.com/attachments/...er-r1front.jpg 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) https://www.rx8club.com/attachments/...sion-chart.jpg |
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 |
Originally Posted by furansu
(Post 4864411)
Here is what the Mazda OEM tester looks like:
https://www.rx7club.com/attachments/...er-r1front.jpg 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) https://www.rx8club.com/attachments/...sion-chart.jpg 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.
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Originally Posted by UnknownJinX
(Post 4864414)
Could be that the second dealer did it when the engine is cold. If it's cold, the compression numbers will be higher.
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