I've just done a compression test on an engine rebuilt 3 years & 8,000m ago for a Greddy kit. The engine was described as rebuilt suitable for a turbo application by a respected builder; the receipt and warranty give no details on porting, seals etc and the builder isn't contactable for a week or 2.

The compression results were at a low rpm (215 ish) as the battery struggled, and normalised to 250 have around 5.3 on the front rotor and 6.2 in the rear rotor, all 3 chambers reasonably consistent across each rotor. I'll put the detailed figures when I have them to hand.

The rear rotor is what I'd expected for a ported engine but the front 5.3 concerns me.

Anyone got any thoughts?

Update:
Actual figures:
Front @ 213 rpm
67.0/4.71 68.2/4.79 67.2/4.72 Average 68.8/4.84 (psi/kgfcm-2)
Rear @ 215 rpm
80.4/5.65 79.1/5.56 78.2/5.50 Average 79.2/5.57
Normalized figures (ie adjusted for RPM, atmospheric pressure, dead space):
Front @ 250 rpm
75.3/5.30 76.7/5.39 75.6/5.31 Average 75.9/5.33
Rear @ 250 rpm
89.9/6.32 88.6/6.23 87.5/6.15 Average 88.7/6.23

 

That engine is done, the fact that the engine is turbocharged doesn't mean anything and with a street port, the results won't be that different than a non ported engine. Mine is street ported and has 40,000 turbocharged miles and as of my last test was still solidy in the 8's.

Also there is not much you can do to build a Renesis specifically for boosted duty. I mean people have ideas but generally the engine built for boost don't last any longer than a normal rebuild. It's more about who is doing the rebuild and what parts are reused.

 

What are you testing this with? Is it a Mazda tester or some other device? I've had mine tested with a TR-01 and it showed a consistent 80psi, where a subsequent Mazda test showed 120psi.

 

I tested our Rotary Diagnostics tester against the stock Mazda tester and the Twisted one and the results were pretty inline with each other. If you had a borderline engine it would be passing on one and possibly not another but overall they were pretty accurate.

 

Thanks.

I think the tester is fine. It's a TR01 that I've used 50+ times on standard engines and gives very consistent high figures for my R3 engine. It matched the results of a Mazda tester the first time that I used it, as expected, and subsequent results show no evidence of sensor failure.

Also, I go further than most users by doing a full adjustment for atmospheric pressure. The Mazda tester does this automatically. The difference is more academic than essential where I am near sea level; for a test at height in, say Colarado, could be up 20% out, changing an underlying 7.0 pass into a 5.6 dismal failure.

80 instead of 120 suggests the sensor has failed or the settings are wrong (for some reason mine reset after shutting down and I can't get them to save; that's me or a software glitch, and it's just easier for me to live with it).

 

Anyone else got any thoughts?

 

A local member and buddy (dealer tech) of mine is who brings the Mazda tester, and it will only normalize the results if you connect the usb cord and use the Mazda software, which we did on his laptop.

 

Thanks. Interesting, as my memory of the Mazda tester used in comparison when I got my tester was that the box did all the corrections and didn't need a laptop. The explanation my simply be that different Mazda testers (I know of 3 different part numbers) have different operating methods, with the first RX8 version not having built-in normalization.