was it just me or did that not seem TOO carboned up like the "mechanic" said what caused it!

 

would break in affect the springs?
Sounds to me as if it is overheating at the exhaust port which affected the side seal springs? the seals themselves were good. Some racing teams have had this same issue--car ran ok --just lost 15-20 hp up top. Dont know for sure but this sounds simalar
OD

 

Mazda doesn't know how to do a compression check?

And it takes you 3 hours of cranking to do a compression test. Then you take apart motor and can not find the cause.


Are you sure you did the compression check correctly?

What were the numbers and RPM?

 

looks like a ridiculous amount of side iron wear from the side seal. Something was definitely wrong there. Could just be a bad assemble from mazda?

But most likely not warming it up would be a reason for it to get stuck, imagine the motor just cranking, then instantly revving to redling with hardly any oil pressure to lube the side seals. That **** is gonna get really hot and expand. Causing a stuck seal . pretty simple

 

Well The Local Dealer that the owner went is located at an island and it seemed that the mechanics were never trained how to do a compression check. After they got help from the central offices in Mazda they did a compression check.

The compression checked signalled a replacement in Engine that never happened because Mazda refused to do due to aftermarket parts installed on the car. Since this car is not my car I do not know the compression numbers but I will ask the owner.

After refusal of Mazda to replace the engine the owner went to a local rotary shop. Compression was taken again properly and verified the numbers of the first compression check. The engine was opened in front of me and some other RX-8 owners and it was our first opportunity to watch a renesis opening.

Local rotary shop mechanic said that some seals were stuck due to carbon lock. We do not have the experience to understand what is the real problem. I was suspicious because the mechanic pulled two broken side seals springs and apart those springs everything else seemed to my untrained eye to be in perfect condition. So I came to the conclusion that the low compression problem was due to the broken side seals springs.

So compression was taken two times in two different garages signifying the same results.

RX-8 problem before taking the first compression check was that after 10 minutes of operation was stalling and after the engine was dead could not start again.

Anyway this is not my car and I have opened this thread in order to inform about an RX-8 problem. To my untrained eyes this renesis due to racing conditions and overheating caused side seals springs to break.

You have to take into consideration that Mazda dealers in Greece and special at Greek islands lack of training and this is the reason that compression at the first place was hard to do.

However, the local rotary shop is working with wankel engines over 20 years and the mechanic have rebuilt successfully many 13B engines. The local rotary shop did not take time to examine the engine and the used parts. This is a task that had to do later. He just expressed a first opinion on the problem of the renesis but this opinion may change as he examines better the engine.

 

As it concerns warming properly the engine the owner claims that he always warmed to operating temp and even more the engine. Over 20 minutes of warming and then hard acceleration.

As I said the side seal springs were broken and may be that caused the wear in the side iron.

 

closer look of intake and exhaust ports

 

The pre-mix is not the problem and the carbon;unfortunately, is rather normal unless it's strictly raced (Normal for Renesis). It's always important to know what rpm a rotary compression test is performed at in relation to the resulting numbers. That 400 kpa isn't bad if you have a weak starter or bad battery.

Paul.

 

Owner told me that the compression was an average of 340KPA at 250rpm. This number applied to the rest of the chambers (i.e 348, 339 etc)


So Paul you say that probably carbon lock WAS NOT the problem this renesis had so low compression numbers???

You think that the compression problem can be related to the broken side seal springs ?

 

thanks for the updated info and pics---exhaust ports do not look overheated to me--so I was wrong.
could have been a bad rebuild?
Warmed good before running. developed the classic low compression idling probs at 5K.
SOMETHING isnt right.
Would need to speck it all out to see where the prob was?
OD

 

Maybe I'm missing something, but where are the broken side seal springs?
The 6 you show in the pics look fine to me.

 

do you know what aftermarket parts did he have installed?

 

Is he going to do some cooling mods to the cor and maybe some porting though?
@Jeff: i hope that the broken springs were alrea trashed... do you imagine tearing apart a potentially perfect engine with low miles that would have done just fine with a decarb?

 

^yeah that would b a shitty day

 

I do not know what the owner decided about and mods or porting.

You are very right about the broken springs ! The rebuilder I soon as he examined the broken springs he just trashed them not giving us opportunity to take a photo.

I do not know how safe is to have a decarbed renesis engine having broken side seals springs.

 

The classic NA as Revi, final muffler, coilover etc.

 

The car was brand new. This means that the renesis came from the factory and it was not a rebuild.

We have asked the rebuilder to examine the engine and give us a better explanation about the engine failure. We could not believe that a renesis with 5200 miles using premix would have so much carbon lock as to stack some springs (i.e apex seals springs).

We have a lot of cars that are using premix more than 30.000 kms with no problem in carbon deposits and with very good compression. Why a car with 5200 miles and premix will have carbon issues?

I believe that this engine lost compression from the side seals. At least this is a point of failure that found opening this engine.

 

Right, but he didn't even premix. 180ml are close to nothing. i usually premix with something around 120 grams!.
Anyway, with a dial gauge and a caliber you should see what parts could be reused. A rebuild with a so young engine shouldn't bee to expensive.
From the pics it doesn't even seem to be too much carbon build up. This must be, as said, a case of poor break-in and bad luck.
Tell the owner to do at least 1500km of break-in this time, possibly using the method that i stated some posts ago.
Did the shop owner take some measures concerning the side seals tolerances? It would be cool to know how they were.

 

180ml = 180 milliliter = 0.18 liter = 6.08 ounce [US, liquid] PER TANK (61Liters. )

So 6 oz per tank IS NOT PREMIXING ?

Idemitsu suggests 238ml per tank and you think 180ml per tank is not premixing ?

The owner DID break in the engine for at least 1500km. The engine had compression problems at 8500km. The owner went at track after 2000km.

You think that a renesis with 2000km of breaking IS NOT suitable for track day ?

The shop owner have not finished his evaluation yet.

 

it's 3\4 of what idemitsu says so it is a light premix. Anyway i misread your numbers, that's why i said that. I thought you were putting 18ml which is close to 0, lol.

You said earlier that the break-in was of about 1000km, now it is at least 1500km. The owner must be confused!
2000km of break-in is absolutely not suitable for track days if poorly done.
Race teams do break in the engines differently but they also rebuild them more often than the average joe.
I wouldn't hit the track with an engine with just 2000km. Add transmission break-in, differential etc.
Did he at least swap his fluids after the break in or after the first track days? New parts do leave a lot of metal dust.

 

ml = milliliters. Maybe you're thinking milligrams. 180ml of oil is around 130 grams.

 

This sucks. My first engine went kapoop at 22k. Subscribed.

 

Well no, to be honest i just kept the final 0 out in my mind. Pretty harsh period here, in italy we've got exams 'till the end of july.
A druggie is mentally healthier than me!

 

Get some new seals and put it back together---

 

I premix AT LEAST 8oz per tank....if I know i'm going to be runningit pretty hard i'll go more on the heavy side!....

damn i better go get some more premix while i'm thining of it