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RX-8 Compression

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Old May 28, 2019 | 07:04 PM
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GautamC's Avatar
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RX-8 Compression

I've been looking at RX-8s and I noticed one from 2004 that has 87k miles, but has the following compression stats : 98 95 99. Image is attached. Is the higher mileage worth for the compression, or would the apex seals be blown too soon for it to matter?



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Old Jun 3, 2019 | 01:02 PM
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Those are only stats for one rotor, you need the other 3 values.

However, 98 psi at 259rom is borderline. I wouldn't spend a lot of money on this car. If it's cheap you buy it and drop in a replacement engine and start with a clean slate. These days that's a better strategy than finding a healthy original engine.
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Old Jun 7, 2019 | 10:19 AM
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Originally Posted by GautamC
I've been looking at RX-8s and I noticed one from 2004 that has 87k miles, but has the following compression stats : 98 95 99. Image is attached. Is the higher mileage worth for the compression, or would the apex seals be blown too soon for it to matter?



98 psi should start ok
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Old Jun 11, 2019 | 02:13 PM
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As long as the numbers are about the same in the other rotor it should run just fine. Keep in mind, your numbers are a bit low assuming you arent high in altitude when you did the test. This engine appears to be close to needing a rebuild soon so if you can get it cheap go for it. 100 psi is minimum spec.
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Old Jun 13, 2019 | 08:16 PM
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Somebody else just posted in another thread part of the factory service manual that says minimum spec is 98.6 psi at 250rpm.
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Old Jun 14, 2019 | 11:58 AM
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Per the below chart...

For example...@ 250 rpm:
- Standard compression (A): ~120 psi
- Minimum compression (B): ~98.5 psi


The swath cut threw the chart bounded by A & B demarc the STANDARD (A) and MINIMUM (B) compression range at the listed RPM along the X-axis.
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Old Jun 14, 2019 | 02:58 PM
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Anything below 100 a good idea to start saving pennies for a rebuild. The car will run and drive fine but as the engine continues to wear over time, a rebuild is less and less likely going to be a good option due to damage being caused to rotors and housings. You may be forced to get a reman engine and swap it in.
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