djgiron

So my car got its compression test today. I have the compression chart, but my question is are there corrections to it based on altitude (which is what the dealer is saying).

Here are the readings:
7.0 7.0 7.2 - 307
7.4 7.1 7.1 - 304

Keep in mind I am at 5000+ feet if that matters. They are calling Mazda Corp tomorrow to see if they want to replace the engine with those numbers. This is the last month of my extended warranty which is why I got the comp test.

UnknownJinX

Yes, and by a huge amount if you are at 5000+ feet. The normalizing calculator has an altitude input for this very reason.

The numbers after being normalized:

Rotor 1: 7.88 7.88 8.10

Rotor 2: 8.38 8.38 8.04

I am jealous now.

djgiron

Thanks man, was nervous, also no need to be jealous, my car is an '09 with 28k miles

UnknownJinX

Mine has 44k miles now. Compression is not bad, but just not as good as yours.

I do hope our S2 engines hold up well.

djgiron

Yeah me too, it is a fun car to drive for sure.

djgiron

Funny thing just happened, Mazda called me back and told me they will replace my engine under warranty . . .

9krpmrx8

iTrader: (46)

Nice, that is cutting it close.

djgiron

Honestly the only reason I got the compression test is because the cost was $59 (diagnostic fee) and I figured why not, i guess it worked out.

9krpmrx8

iTrader: (46)

Yeah a ton of people drive around with low compression. It's such a gradual loss in power most peoples butt dynos don't detect a problem and many (like my first reman) seem fine and then just die from one day to the next without any previous symptoms.

My factory engine didn't seem that low on power but I did a highway pull against buddies then new RX-8 and he pulled me like by two car lengths and then I knew something was wrong and about two months later it started to stall on me and that was that, it had 22,000 miles on it.

Loki

iTrader: (1)

Wait what? But those numbers aren't failing? Can you refuse the new engine? Who knows what quality the rebuild will have.

Jastreb

iTrader: (1)

Please don't! Please don't replace a perfectly good factory engine that has only 28k miles, with a Mazda re-manufactured engine of unknown quality. Those re-mans are mix of old and new parts, and you have no idea the condition of the engine internals you're actually getting. Combine that with dealer techs that hardly ever work on these cars any more and you also have potential for installation errors. I got a Mazda re-man because I was stupid, and that engine never ran right and made it 35k miles before blowing a coolant seal.

As an aside, it seems Mazda doesn't know how to interpret their own compression tests any more?

wannawankel

If you need another opinion - stick with your engine.

UnknownJinX

What was the culprit?

UnknownJinX

But 9k said his factory engine went out after 22k miles. I wonder what happened.

9krpmrx8

iTrader: (46)

No one knows, dealers can't break down the engines. The engine was dealer serviced and bone stock, it just died. My second engine (first reman) lasted 74k or so and then one day I was rowing thru the gears and it felt like I hit a brick wall. I replaced the coils and the power was back but then a month later it started stalling (I blame a clogged cat) and reman #2 was installed. Reman #2 lasted 27k or so until coolant was found in the oil during a routine oil test with Blackstone.

You never know what you are going to get in a Mazda reman since some part are new and some are re used so it all depends on who is doing the rebuild. But they do use a lot of new major parts so it can be beneficial to get a reman and then have that rebuilt by a reputable builder. That is what Mazmart does IIRC.

djgiron

Well in the last month is has had a very rough idle and seem to fall off at high RPM's. I know it is not the plugs or coils as I upgraded to BHR Coils and new plugs ~10k miles ago. I don't think it is the MAF as I change my own oil (other than this time as I wanted the comp test). So there is something wrong with it. I haven't had the time to check the CAT (finishing my yard so far this summer) so I will talk them into checking on that when they pull the engine. As for techs, 3 of them have 8's so I am not so worried about that.

TheWyvern

Seriously can't stress enough that those are very strong numbers and don't warrant a replacement whatsoever. If you think they did the test wrong, have them do it again just for safety, but replacing an engine with those number is a huge roll of the dice.

Jastreb

iTrader: (1)

With normalized compression in the low 8s/ high 7s the engine core is unlikely to be the cause of your issues. I am surprised Mazda approved it. Rough idle could be due to several things - vacuum leak or leaky injectors for instance, and replacing the engine core may not fix it. For instance, injector cleaning and flow testing is not part of the standard Mazda procedure for an engine replacement. As everyone else has stated, you are really rolling the dice here. Another cautionary tale - a Canadian member on here had two successive Mazda re-man fails within a few hundred miles of them being installed at the dealer. I think the 3rd time was the charm for him, but only after considerable aggravation. I strongly advise you to spend a bit more time diagnosing your issue before you have the engine pulled. If you can post OBD-II data logs that have your MAF airflow and fuel trims and RPM, the knowledgeable forum members here can point you in the right direction. Otherwise, best of luck to you.

djgiron

I don't have a way to post the data logs.

9krpmrx8

iTrader: (46)

datazap.me | Fast, Free, Interactive Datalogs

Rudolph

I have a 2008 RX-8 HP with 36.500 mls since new.......
The engine still runs very fine and starts cold or warm within 0,5-1,0 second..

I was interested in my compression values and a month ago I did a first compression test wit my own "RCT-V5.2 Rotary Compression Tester".......each rotor was tested 2 times..........

The results:
Front rotor:
kg/cm2 at adjusted/normalised 250 rpm.........1st -- 8,60 / 8.02 / 7.43
.................................................. ............2nd --8,53 / 8,31 / 8,02
Rear rotor:
kg/cm2 at adjusted/normalised 250 rpm.........1st -- 8,83 / 8,48 / 8,46
.................................................. ............2nd --8,83 / 8,39 / 8,09

The results for both rotors seem to be ok in respect with the individual heights, but the differecenses between the chambers for each rotor are considerable........however within the max. allowed tolerance of Mazda
MAZDA tolerance norm: deviation for chambers on one rotor max 1,5 kg/cm2.........deviation between 2 rotors max 1,0 kg/cm2

Could there be any reason, for instance the presence of premix oil?

For your info: I started premixing from new at 1 oz/gallon plus active OMP (increased the flow rate of the OMP at 10.000 km with 50%)........on which the engine runs very smooth; especially at idle you can clearly hear the difference
I run 5 or 10W40 engine oil in the moderate Dutch sea-climate.........oil change every 5.000 mls.........spark plugs + leads every 20.000 mls........OEM Mazda coils every 30-35.000 mls ..........recently I changed the motor mounts......again OEM Mazda; the old ones still had "free space" on both sides.