Raivynn

2007 RX-8 AT, Sport (although VIN pops a GT)
48Kmi (estimated, in the high 47k)



After 2 months of ownership, I finally got the chance to take my 8 to Mazda for a compression test. I wanted to share my results and see if an engine replacement is going to be in my near future. The dealership says the engine is "good," and that I "shouldn't be worried until the compression is in the 400's." The "spark plugs are original and need replaced." I was also verbally informed that the coils "show wear, but still pass all tests and are within specifications." The car does have issues with the check coolant light at highway speeds. The tech wrote down the compression in the wrong measurement, so I am replacing what he wrote with the correct one.

"F Rotor @ 250 RPM
1. 690 KPa
2. 710 KPa
3. 710 KPA

R Rotor @ 251 RPM
1. 710 KPa
2. 720 KPa
3. 705 KPa"

They recommended a decarb at 60K, however, I think I am going to try and get it in sooner and see if that raises the compression at all. I have seen members get better compression from just the decarb. I live in a snooty neighborhood, and can't get away with Seafoaming at home. Plus ... Mazda would be responsible if "anything goes wrong" vs. me doing it at home and being responsible if something goes wrong. Mazda also recommended waiting to 60K to change the plugs/coils/wires. Kinda don't think the same thing ... I almost had them go ahead and change the plugs, but the service manager was pretty much insisting I bring it back at a later time for service. Found that to be strange since the tech wrote on the service ticket that plugs need replacement ................


Where do I go from here? I am planning on speaking with another reputable dealer's service shop (Mazda, of course) to see what they take from the compression test results. With Face 1 of the front rotor at dead minimum compression, is this engine at risk? (Probably. )

I will say that I do see a small hesitation at start up, though I am thinking this is normal for a rotary (takes around 2 seconds between ignition and fire up), but the car runs smoothly and effortlessly. It has the AT "bog down" at times. So I am not seeing a hard start at cold or running temp, which were the first questions the service department at Mazda asked me. They were not sure why I was asking for the compression test on a "well running vehicle."

If you guys need any more info, let me know. I will give ya all I got.

RIWWP

iTrader: (2)

I believe those numbers would be divide by 100 to get to the normal scale, in which case you are just barely passing on 5 of the 6 rotor faces. The 6.9 is either .1 from failing or just at the failing line, depending on how you define the failure point (less than, or equal to)

The rpm is exactly at the normalization point of 250rpm, so there isn't any fudge there.

A 4.0 wouldn't run at all.



Considering the dealer's reaction to the numbers though, I'd expect a tough time with them.

Raivynn

The service tech originally wrote those values in psi, so I believe that warrants a trip to a different technician anyways. I doubt they will recheck the compression for free, but I want to keep my engine from failing.

RIWWP

iTrader: (2)

Yeah, a 2nd opinion is always worth something.

I had mine checked 3 times in 2010, the first one was done by a dealer I didn't trust (but was nearby) and the scores came back in the low 5s and I was told "it passes". I should have realized they weren't going to want to deal with it when they said "we have never had to replace an engine!"

I took it to another dealer I trust 4 days later and got 7.0-7.1s across the board. 6 weeks later got high 7s at the 2nd dealer. Same tech, same equipment.

Raivynn

I will definitely be asking if they can match the price of the first dealer (they quoted 1 hour labor charge, and I forced them to honor it), but if not, I'm in for another $200 bill. Bleh. And the reason I went to the first dealer - it's about 45 minutes closer to me, and it's 40 minutes away...But, lots of highway driving gives me a good excuse to drive it like I stole it. :D


AND a good excuse for an oil change, 500 miles early.

RIWWP

iTrader: (2)

The only dealer "in the area" I trust is an hour and a half away

So basically I only go there for warranty work, and with only my engine left under warranty, just compression checks.

reddozen

iTrader: (1)

Compression test should be like a flat $80. Don't make them quote a stupid hourly fee. Get a flat quote on a compression test.

I had no problems getting Nelson Mazda in Hickory Hollow to replace my engine, but they also know that I'm a rotary guy and don't usually try and take advantage of me.

Good Luck.

Raivynn

Took my 8 to Nelson. To get things straight, the service manager set it up to where Mazda is covering my decarb, and I believe they will retest the compression as well. They are pricing the full tune up for me, at a ridiculous low price (around $500 - I've been quoted between $700 and $800 prior). They are replacing my cabin air filter.

I am definitely coming to Nelson again. Maybe not for oil changes that I get for nearly free, but I do have weak motor mounts...ugh.

Raivynn

Oh, and Nelson Mazda also replaced the spark plugs for me as well. This had a better outcome than I first thought.

FastFreddy61

May I ask , how do you know, or what do you mean "weak" motor mounts ?

Raivynn

The technician simply stated the mounts were weak. I'm assuming this means they are showing signs of wear. I notice slight vibration in drive at idle.

Nadrealista

for $200 you can get new plugs, coils, coolant, all filters and bunch of seafom..find local rotary enthusiast to help you and don't waste your money at the dealer. you are ways away from the end of your engine warranty so no need to test compression if your car is running well. clean your OMP and decarb twice a year and you will be fine.

lilring

iTrader: (11)

Raivynn. If you need any help with your 8. please let me know. Im a tech at a Andrews Cadillac in brentwood and Ive owned a few rotaries. I will be more than glad to help a fellow 8 owner.

Raivynn

Much appreciated. :D As you can easily tell, the 8 is my first rotary experience. The Cool Springs Mazda dealer, while a great team, didn't inspire my trust like Nelson Mazda did. They weren't rude or anything, but I just feel like Nelson had more experience with the 8 - they had an '05 in the shop for an engine replacement the day I took mine in.

Part of the reason I can't decarb "at home" is because I live in a very nosy neighborhood, and moving to an apartment complex within the next few weeks. So ... let's not go there.

And now that all the mechanical checks out ... time to drive the t total **** outta my 8.

9krpmrx8

iTrader: (46)

My handy dandy android rotary compression calculator app says:

Front rotor chamber difference is 20.0 and the rear chamber difference is 15.0

Rotors difference is 11.02


Your alright, tune up time.

drag0s

Hope this thread isnt completely dead...

Does anyone happen to know the minimum acceptable kPa / rpm for the compression?

They`re listed as 680 and 250 respectively on my compression test and my 8 scored below these levels, but the dealer is trying to tell me not to worry because the "acceptable levels" shown on the test are not the "true acceptable levels that mazda uses".

I`m getting between 613-675 on all of them @ 224 RPM which seems terrible imo...

drag0s

Hope this thread isnt completely dead...

Does anyone happen to know the minimum acceptable kPa / rpm for the compression?

They`re listed as 680 and 250 respectively on my compression test and my 8 scored below these levels, but the dealer is trying to tell me not to worry because the "acceptable levels" shown on the test are not the "true acceptable levels that mazda uses".

I`m getting between 613-675 on all of them @ 224 RPM which seems terrible imo...

2004 here with 65k miles

drag0s

Can anyone shed some light regarding the minimum acceptable kPa / rpm for the compression?

They`re listed as 680 and 250 respectively on my compression test and my 8 scored below these levels, but the dealer is trying to tell me not to worry because the "acceptable levels" shown on the test are not the "true acceptable levels that mazda uses".

I`m getting between 613-675 on all of them @ 224 RPM which seems terrible imo...

drag0s

Can anyone shed some light regarding the minimum acceptable kPa / rpm for the compression please?

Eldragon0

Pick one day out of the next week, take off work early, and call every mazda dealer within 50 miles. Ask for their rotary techs and ask them directly.
That's how I settles on the dealership to bring mine to.

RIWWP

iTrader: (2)

See the new owner thread, it details what good numbers are, provides a chart, etc...

Your numbers are fine, when normalized to 250rpm. Low to mid 7s. Your starter could use a replacement though.

se3p_s

My compression result is
"F" rotor @999rmp
1. 0.52 mpa
2. 0.52 mpa
3. 0 mpa

"R" rotor @999rpm
1. 0.53 mpa
2.0.53 mpa
3. 0 mpa
Recently i rebuild it and it runs fine.

Unionville_2004_RX8

Recently have developed problems with hot starts (most of time but not always). Checked battery (got it replaced). Have replaced all ignition coils/wires/spark plugs in November 2014. So decided to get a compression test done.

Rotor #1 222RPM------>250RPM
7.3 Kgf------------------>7.9 Kgf
7.1 Kgf------------------>7.7 Kgf
7.5 Kgf------------------>8.1 Kgf

Rotor #2 223RPM------->250RPM
7.3 Kgf------------------->7.9 Kgf
7.1 Kgf------------------->7.7 Kgf
8.3 Kgf------------------->8.5 Kgf This one seems high for some reason (oil in chamber?)

I have used the online calculator that the guy from Android used. Which gives lower values the Foxed. The normalization to sea level I have not done. Though I live at 533feet above sea level. So I don't think the numbers should change that much! Mazda didn't mention anything about the status of the starter (150RPM under load is a fail I believe)

I said I might bring it back in to let a technician look at what possibly could be the problem. But sounds like they want to start with checking the status of the Ignition coils.

I think the starter needs to be replaced, but I dont want to spend over $400 on a possible fix. Any suggestions?

9krpmrx8

iTrader: (46)

The Android calculator is inaccurate and I notified the creator a while ago, not sure if it was fixed or not. I tested it against an OEM Mazda tester/system and it was way off. The twisted rotors tester and our rotary diagnostics tester when used with the Foxed calculator showed both testers were pretty accurate.

Those numbers are marginal. Who did the test, the dealer? If so, did they use the WDS system to print the results? And a starter upgrade is well worth it and not $400.00, unless you get the 09-11 starter from the dealer. I recommend the 09-11 RX-8 manual starter :

Unionville_2004_RX8

Well interesting to know about that android one. I did use the Foxed calc as well. They did give me higher results (8.2, 7.9, 8.4) and (8.2, 7.9, 9.3). I did take it to the local dealer to do the compression test. And like before, it is scribbled down on a piece of paper with smudges all over it then. And I am handed a photo copy of the sheet. I did have the service manager sign the sheet which have the results.

Will look into that starter though.