This is why being paranoid is a bad thing when it comes to rotarys. I've had engines with 85 psi last 50+ thousand miles and NEVER fail to not start hot or cold. It's better to trust the original S2 engine that's built in Japan than the remans. I don't know who Mazda is using for remans these days but, Williams tech rebuilt the engines back when I was a Mazda parts manager back in 2007-2008. Those rebuilds were basically junk. All these compression numbers you guys keep paying for and throwing around is a waste of your time. Why???? Because y'all want a free engine?? Buy a compression check gauge, remove the shradder valve and do your own. Sometime it's just better to leave well enough alone because you can't control all the other issues that can and will come up as soon as the dealer starts pulling your engine. Today's Mazda mechanics don't have a clue how these engines run and most have never even rebuilt one. My advise, at 75k miles and higher, if it cranks up and runs all day everyday and is reliable, leave it the hell alone. The apex seals in these things are very short and light for high rpm reving. As they get shorter they loose there spring tension so the compression will lower over time. Plus these side seals wear down faster because of the side exhaust. These engines aren't like the 3mm sealed engines of the 1st gen Rx7. Those engines would easily last 200+ thousand miles because they were lower reving and the seals were damn near bullet proof. This coming from a 20b guy who did his own engine swap.

My 25k mile S2 failed compression test and had engine replaced under warranty.
Unfortunately no compression numbers or troubleshooting on the failed engine.
Crossing my fingers on the reman. There's a lot of sealant ooozing externally...
They did a good job though, mechanically. Everything is tight, no drips, tech was very thorough.

Car is under warranty till Oct 2017. Sept 2017 it goes for compression test. If good, fine. If fails, the (next) reman engine will be yanked right out and sent to a reputable builder.

2009 R3 - 61,000 miles

The car cranks up quick every time, no hot start issues or issues of any kind really except that there is a slight stumble at idle occasionally, barely big enough for the tach needle to register, but I can hear/feel it.

I purchased the car for a discount from a non-mazda dealership on the basis that compression was below spec (according to their local mechanic's comp test):

R1: 102.7 - 100.4 - 99.8 --Normalized for 250 rpm @0ft-- R1: 97.5 - 95.3 - 94.6
R2: 108.9 - 108.6 - 105.5 --Normalized for 250 rpm @0ft-- R2: 103.4 - 103.1- 100.2
@303 rpm and 900ft elevation

Of course I already called Mazda North America to confirm the extended engine warranty was still in place prior to purchase ;-). I figured I'd drive hard for a couple days with no premix, then take it in for a Mazda comp test.

(results are converted from Kpa)
R1: - 121.8 - 117.5 -117.5 --Normalized for 250 rpm -- R1: 104.8- 101.1- 101.1
R2: 121.8- 120.3- 120.3 --Normalized for 250 rpm -- R2: 104.8- 103.5- 103.5
@332 rpm and 0 ft elevation

The tech wrote a narrative on the service report about how the high cranking rpm of the starter was producing inflated compression results and that when normalized for 250 rpm were borderline. However he privately confided that mazda will not accept normalized results for warranty purposes and suggested that I either replace the battery with a weak one,or install and S1 starter so the results will be more accurate.

My concern is that with that hit & miss quality of remans and the fact that my "Italian tune up" seemed to actually raise compression instead of lowering it, am I better off trying to save this engine, via a decarbon procedure or continuing down the reman path? Keep in mind the warranty is up at the end of the month.

Thanks

It is your call here. But yes you need to get a compression test result that Mazda will accept. Try to contact MNAO to be sure what you were told is accurate. Often dealerships get it wrong. MNAO will ultimately make the final decision on approving any warranty engine replacement, not your local dealer.

Don't let that warranty period expire without proper test results. I got a reman approved by Mazda in 2016 with my (borderline failing numbers) test results, with just one week left on my warranty period (8years was up). My reman has been very strong and I have taken additional steps to help keep it running for a long time.

Another fellow RX8club member and friend of mine in Arizona, with his 8year warranty time almost up, had a dealer give him the runaround about his compression test numbers until the warranty ran out, and then he was out of luck for any Mazda reman. The dealer just really didn't want to bother doing the work, even though Mazda pays for it. Don't let a local dealer rob you of thousands of dollars of work that you are entitled too.

Just my advice. Don't delay, it could personally cost you thousands of dollars if you have to pay for an engine replacement yourself. If you intend to keep this car, don't miss out here.


By Phone Mazda North America Operations

M-F, 5:00am - 6:00pm PST
Sat., 7:00am - 3:00pm PST

(800) 222‑5500

Got a 2011 R3 last August, love the car but I've been worried about the compression.

Test last Aug, @18500 miles. Hot, somewhat humid day

Rotor 1:
800
770
780
@250
Rotor 2:
790
790
790
@250

Today @24500, cold rainy weather
Rotor 1:
730
740
700
@250

Rotor 2:
730
740
740
@250

First thing I did after I got it was swap in new plugs. Just swapped in new coils a few weeks ago. I've had the occasional hot/hard start, maybe twice in the last few months. Any cause for concern? Can weather result in such a massive change in numbers?

Recently got a 2011 GT

Had it tested yesterday:
R1 8.6, 7.2, 8.6
R2 8.6, 8.5, 8.6

With the one facing so off it's 'borderline'. Talking like ~1PSI here to be considered failing by difference in faces.

42k original engine. Worth risking the reman lottery or just deal with some side seal weakness?

Drives great, no problems so far

it could be some carbon deposit stickiness of the side seal. maybe a decarb procedure will loosen it and restore that little bit of compression loss

Would Mazda replace under warranty?
I thought it needed 690 and down on a face.

Like he mentioned, there is a limit on how much compression can differ between faces and rotors, so if all the other faces are mid 8s while one face has a flat 7, that's still a fail.

This is from the Service Manual:

https://cimg8.ibsrv.net/gimg/www.rx8...f5c0be597e.png

Compression Test Results in Strange Format
 

Hi all, long time follower, first-ever post. :-)

My 2011 RX-8 GT automatic (63,000 miles) just died. I had a compression test done by a Mazda dealer just before the warranty ran out last July because I noticed a significant loss in power starting in May. They said the compression was low, but still within spec. (I should have pushed more at this point, but they changed the spark plugs and sent me on my way.) The car never felt right, some days better than others. But, I figured Mazda must know their cars. Anyway, the engine gave up the ghost a couple of weeks ago and I asked the dealer for a copy of the compression test results that were done in June (2019). (I had not been provided with this information at the time of the test. I know... I'm an idiot for not getting this then.)

Long story short... the results don't look like what I was expecting to see. There are four numbers instead of six, in a format I don't recognize for rotaries. It says: L 110 T 110, L 115 T 115.

Can anyone shed any light on this? Was the test even done properly? I'm convinced the engine was shot back in June. I only drove it 3,000 miles since the test and it never felt right. I feel like the Mazda dealer screwed up, but they won't admit it and aren't interested in trying to make it right. Their tech admitted they may have "caught the car on a good day" back in June due to the expansion/compression of the seals. But, my appeals with the dealer and Mazda corporate have come up empty. (I know I'm an idiot, and Mazda owes me nothing. Still... something seems fishy with those test results.)

Thanks for any insight,
Jeremy

Test results:
https://dwellingproductions.com/down...st-results.pdf
https://dwellingproductions.com/down...st-results.jpg

https://cimg6.ibsrv.net/gimg/www.rx8...73a4b9b0ff.jpg
Compression Test Results (strange format) - 2011 RX-8 GT Automatic - 63,000 miles

Hi. What ever happened with this? I have a 2011 at very similar mileage that won't start, and my local mechanic is blaming compression. It may be a similar situation.

Do you have trouble with cold starting or hot starting? Hot starting trouble could be compression, while cold starting trouble could be ignition, fuel injection, etc.

The numbers in the post you quoted aren't useful. Rotary compression varies quite a bit by RPM.

As the others say, you need 3 compression pressure numbers and 1 starter RPM number for each rotor. Go to a knowledgable Mazda dealer or a rotary shop to find out.

This is what the local dealer gave me when I purchased mine. It could be a different device, but should still be in the same format.
https://cimg7.ibsrv.net/gimg/www.rx8...b6a2ac0c09.jpg