So, I had the engine compression check on my 2005 with 69K today
 

Stats: 2005 model MT with 69,000 one owner miles bought with 15 miles on it
Never been flooded and never had starting issues
All the recalls have been done with reflashes, new starter and battery
Plugs, Coils and Wires have less than 2,000 miles on them

She has recently cut off on me a few times while driving on the interstate and this morning after driving her 7 miles to work, shut off and sat for 15 minutes, she did not want to start. I took her to Wills Mazda in Sumter, SC for the engine failure tests this afternoon.

Initial Tests:
All coils firing
Barometric test good – below 1.90
Cat switch ratio .218 – no codes

Compression Test on trailing side:
Front rotor @ 283 rpm - 124.99 PSI, 125.86 PSI and third twist 123.685 PSI
Rear rotor @ 274 rpm – 121.365 PSI, 121.365 PSI and third twist 118.175 PSI
Standard on a new engine @ 250 RPM is 120 PSI
Minimum for engine replacement @ 250 RPM is 98.4 PSI

Battery is 75 month with a 2006 date
Battery positive post is leaking and corroded
Battery failed cold crank test @ 382 CCA from a 590 CCA battery
Cleaned positive post and charged battery for 30 minutes, battery tested need replace at 469 CCA from 590 CCA
I opted not to have the dealer put a new battery in and will see what this one does over the next week

The Female Mazda tech, Keff a capable young lady, cleaned the battery post and contacted Mazda to discuss. The cause is not completely determined, however the not wanting to start is most likely the battery corroded and low charge. The engine cutting off could be related to the battery (electrical) due to the engine passing the compression test. They requested that I continue driving and monitor if the issues continue.

I am satisfied that it is the battery corrosion and the battery not being able to completely charge due to the massive amount of corrosion on the positive post. The plastic battery cover is nice to look at, but shame on me for not looking at the battery!

Does anyone know how to calculate what my compression readings would be at 250 RPM’s?

in Excel if B21 is your Compression value and B22 is your RPM it's something like...

=(B21*6.894757/1000+(-0.514*LN(B22)+2.838030912))*1000/6.894757

For you values subtract about 9 from the front rotor values and about 7 from the rear rotor values, still well within spec.

Use this graph from the service manual

https://www.rx8club.com/attachment.p...6&d=1117928048

Very nice 69k and the battery is the only problem and you get a female rotary tech. Sorry I saw nothing but positives in this thread.

Thanks for getting me straight on the values at 250 RPM. I guess 5W20 every 3,000 miles, 93 Octane and not turning the ignition off until she is hot is working!

Yes, there is all postives in this thread! The other positive was the time I spent behind the wheel of the new Blue 2009 R3 that the dealer had while Keff was working on mine. They offered me good money for mine and it was tempting, but I decided to drive mine home :slap:. The seats bear hug you and the suspension is noticeably different in the R3. I drive mine long distances and I believe the R3 would beat me up on a long trip :blue: Awesome car though and what a look

I would check the fuel pump as well, just to be sure.

Your compression number look realy quite healthy. Your numbers were used they just get converted for/by the program.
Result from Ioannis conversion utility

people might hate me for this but ... (ppl hate me anyway)

There are times that even dealership "fails" to perform the compression check correctly.

one of the biggest mistake is "test when engine is still COLD", it always give you higher number, some shady dealership might do this so they can keep "trying" other things, until they claim enough warranty money/customer's cash, then they finally say "oh yeah, the engine is bad now. replace it"

Just saying ~~~~

That is awesome if the battery fixes it. But we will see, there is a thread somewhere about the compression test being done cold at a dealer and when they did it hot it was enough of a difference to fail.

Thanks and I value everyones opinions!

I drove the car 50 miles to the dealership, arrived at 1:30 and they put the car in the bay @ 1:50 by my watch to begin testing. She did the coil test first, then the compression test. The engine was not cold, but it had been about an hour since I brought it in when she had completed the tests. Cleaning the battery, charging the battery for 30 minutes and changing the oil and filter, I left at 4:45 pm. Things did go slower in the garage because I was back there with them most of the time.

If someone believes the engine was too cold, please speak up. I am fairly close with the Tech and Service Advisor to the point that they let me in the garage bay area with my car while they are working.

+1 This happened to me and and dad's 8 in the 60k mile range.

Checking the fuel pump is a good idea and of course its "sock filter" while in there. Unfortunately you have to remove the rear seat and have a special tool (preferred). No doubt a cost savings to go with the integral pump/filter in the tank, but a discrete filter would have been a better/easier design imho.

the engine just needs to be warm and it probably still was after that short period

is that available for downloading?

BTW, while it was on the lift we checked the motor mounts and they are not broken. I am getting a vibration at idle and thought they were going to be broken. The tech told me that it may help replacing them, but they would not completely cure the vibration because they are not broken. She took a pry bar and moved the engine ever so slightly when she applied pressure. What do you think, replace them?

Coming up on 18 months have passed and I have 84K on the car now.
My current compression readings are below.
Front - 707,708, 710 @ 278 RPM
Rear - 683, 719, 700 @ 278 RPM

In December of 2009 my compression readings were:
Front - 862, 868, 852 @ 283 RPM
Rear - 837, 837, 815 @ 274 RPM

My car is currently waiting an engine replacement at a dealer.
I am disappointed, but was informed by Mazda that I had nothing to do with the failure. It is interesting that in 15K I went from a strong compression for the miles (69K) to an engine that would not pull up a hill and began stalling.

Did you pre-mix? Will you now?

I did not premix, but I will investigate it for the future. From what I understand, making it as far as I did is remarkable. Any others go over 80K?

Yes many over 100K....

https://www.rx8club.com/rx-8-discussion-3/100-000-mile-club-158709/

Great that you are getting a new engine..I would go with good syn oil and premix this time around.

Out of curiosity did you ever run engine decarb\seafoam cleaning?

I probably need to search some, but you guys in the know. What is causing the low compression. Side seals wearing, or apex seals. Due mainly to excess carbon or poor lubrication?
I had a GSL-SE with 210k miles that was still running when I sold her. She did smoke after sitting a few days, compression was ok, just bad oil control rings.

Educate me on synthetic engine oil, it is not designed to burn and I understand it to cause issues? I will most likely permix fuel though on this engine.

I did not decarb or seafoam, my 69K compression test suggested I should not do either. The issue came on quick, within the last 2,000 miles. Cleaned the MAF and ESS and the issue went away, at least I thought it did. I had not driven the car on a long trip in high heat conditions until last week and the compression was gone.

seafoam once a year, syn oil and premix..that is what I would do if I were you.

no engine oil is designed to burn, but since it does burn in rotary I would prefer to use ester based oil which leaves least deposits..hence decarb once a year...sometimes excessive carbon deposits can give you higher compression readings until seals wear out.

take a look at this pictures that shows deposits left by oil type:
Attachment 244027

one more:
http://www.oilsandlube.com/images/varnish.jpg

Finally got it back yesterday after 29 days! Words cannot express how Pissed I am!