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Hello all, just acquired a 2006 rx8 a couple days ago and I took it into a dealership to get it compression tested. I know I should have done it before buying it but I couldn't and had high hopes because it started great hot and cold and drove strong. The previous owner had done a rebuild at 92k miles and the car is currently at 109k. How much life do I have with the motor/ is it still bad to keep driving the car? What options do I have and what are the prices I'm going to be looking at? Any advice would be much appreciated
Here is a link to the video the dealership sent me:
The technician said he put a jumper on it to increase the rpm for the rotor with the weak compression rotor to see how the compression is doing. I do not know when the spark plugs were replaced, however there are apparently upgraded coils though I am unsure of when those were installed.
Again any advice about this situation is greatly appreciated thank you.
Do you live in a high-elevation area? If so, there are extra corrections you would need to do.
With those numbers, I think your car would struggle to hot start at sea level.
I live in California near the Sacramento area. So I'm pretty much at sea level, the Mazda dealership is the one that did the compression test however I am wondering if they did it correctly because I had to search far and wide just to find one that can do it and they apparently only have one tech that works on rotaries because he had been working for mazda for 30 some odd years. The reason I suspect the test to be a little off as well is because I thought the tests are supposed to be corrected for 250 rpm which the photos and the video they sent me showed they have it left at 230 rpm. So I'm not sure if they did it right and if they did it wrong how far off are they, like are they at least pretty close or just way off the mark. And the car starts cold and hot with no problems at all so that was the whole reason why I took the leap of faith and bought it in the first place. But with the prospect of needing a new engine right away it is definitely making me quite nervous and debating whether to try and sell and move on or see if there is more going on with the car.
Last edited by JasonJenkins; 01-19-2024 at 09:35 PM.
I live in California near the Sacramento area. So I'm pretty much at sea level, the Mazda dealership is the one that did the compression test however I am wondering if they did it correctly because I had to search far and wide just to find one that can do it and they apparently only have one tech that works on rotaries because he had been working for mazda for 30 some odd years. The reason I suspect the test to be a little off as well is because I thought the tests are supposed to be corrected for 250 rpm which the photos and the video they sent me showed they have it left at 230 rpm. So I'm not sure if they did it right and if they did it wrong how far off are they, like are they at least pretty close or just way off the mark. And the car starts cold and hot with no problems at all so that was the whole reason why I took the leap of faith and bought it in the first place. But with the prospect of needing a new engine right away it is definitely making me quite nervous and debating whether to try and sell and move on or see if there is more going on with the car.
Get a standard compression tester ($30) and see if your peaks match theirs, before looking for another rotary test.
You can also pull the valve and video the peaks to see if you have a bad face, as the Mazda test is showing. It will show up that way. Is your hot idle lumpy?
Make sure you log RPM through the OBD port when you test. Compare with the compression graph that is all over this site.
Get a standard compression tester ($30) and see if your peaks match theirs, before looking for another rotary test.
You can also pull the valve and video the peaks to see if you have a bad face, as the Mazda test is showing. It will show up that way. Is your hot idle lumpy?
Make sure you log RPM through the OBD port when you test. Compare with the compression graph that is all over this site.
I decided to just pull the trigger on a rotary compression tester as I have a strong feeling this is not going to be the end of my rotary journey despite this set back. It just might take me a while to get another rotary vehicle if I do decide to sell this one as I am a college student. Anyways my idle is not lumpy at all and the hot/cold starts are just fine. I'd say hot start takes like 2 or 3 seconds if I'm actually counting it. what does logging my RPM through the OBD do as I am compression testing it?
If the hot starts are taking noticeably longer, then you're on borrowed time.
I drove my first one for about a year and a half once it started doing it.
It gradually got worse before it died.
The 2nd one failed much quicker and was dying in traffic after just a few weeks.
Just make sure you're doing the compression test with the engine at normal operating temperature and the throttle completely depressed. Buying a rotary compression tester was the smartest move you could have made in this scenario. To compare, I've had an engine in my 04 RX-8 that has had lower compression numbers for years. It gets driven on nice days only and sits all winter. The gas mileage is down and power is slightly down. I know I'm on borrowed time as well, but I still really enjoy the car. You shoudl as well. Just know the inevitable is coming.
what does logging my RPM through the OBD do as I am compression testing it?
In a rotary compression depends on rpm, so when you get a compression reading it's important to know at what engine speed that compression was read. Can make the difference between a passing and a failing result.
01-16-2024, 10:22 PM
