Hi all,

I am member of a large RX-8 community in Greece. I am reading very carefully every day your magnificent forum. However, there are still some things that I have not fully understand concerning the life of renesis !

I have read all your topics about renesis with more than 100.000 miles , I have read all about premix, all about redlining , all about fuel quality, maintenance about coils, plugs, fuel pumps, all about broken cats

I have read Literally almost every major topic in this forum. BUT I cannot still fully understand the following :

In my country it seems that the renesis life has the following life span

37.282.- 49.709 Miles !!!!!!!!

I know many cars and persons that on the above milage theirs compression is at the low end or just a little bit above specs.

I know also that those cars I know may be a wrong sample to provide sound statistics , hence my conclusion are all wrong.

So the question is:

What are the major reasons you think a renesis with 37.282.- 49.709 Miles will have a bad or low end compression ??

My answer to this is the following

1- bad warm up hence a lot of cold start wear (no sign of proper oil warming with OEM gauges)
2- wrong maintenance
-----------a. plugs change after 37.282 miles
-----------b. No coils replacement at proper millage
-----------c. Clogged fuel pumps and no replacement at proper millage to prevent this.
-----------d. Not so often as required the oil changes
3- Inappropriate fuel quality (They choose cheap fuel that gas stations tend to juggle)
4- Red lining at high ambient temps (along with poor fuel causing knocking)
5- Too much Red lining causing engine/seals wearing


What do you think ?

 

#1 reason is carbon build up on the rotors side/apex seal, springs wont compress and you lose compression. We will see how the 09's life will be, personally I think the placement of the oil filter may help some. One small thing that I still say matter is the placement of the exhaust/intake ports compared to previous rotary engines, I believe in my own opinion that the engine cant push out the carbon as easily as the past versions who had the ports located on the rotor housings themselves. Then again I am just a assembly line worker who is just trying to use common sense to figure those things out, I dont speak japanese so I dont grill the engineers at work it usually turns into them telling me something that doesn't apply to my question that I already know lol. Good news is so far the only 09 motors that have been sent back were due to road damage(hit a rock on the road) and another had gasket failure immediately but either no one has hit 30k+ yet or there hasn't been any issues yet.


Also life span depends on whether its a AT or a MT, MT has a little longer life span but then again it does come down to maintainance, personally I would change the oil every 3k miles, I am a believer in the idea that the oil weights/length of oil change times is longer now due to enviromental reasons more the the idea that engines are made to handle a longer oil life, just my opinion again though.

 

Sleepy-z I do not think that the carbon build up is the main reason. I know may replaced motors that I personally knew the owners and were driving all the time to the red line. No way those motors had carbon build up. Most probably the apex seals were worn so much due to red line that compression was at the low end.

 

Maintenance issues are important, eg, oil changes, premix, but if you've had detonation problems (knock), there's your answer I think.

 

Unfortunately, redlining isn't the be all, end all fix to carbon buildup. Due to the location of the ports, the carbon is having a much harder time "Blowing out". There has been a few topics here of people rebuilding their engines, and there is quite a bit of carbon buildup, even if they redlined it daily. The redline may help it remove some carbon, but it won't keep the engine completely clean of it, either.

 

Need to do periodic zoom-power cleaning, or seafoam. That'll get in there good and deep and eat up carbon.

 

You know, the whole carbon build up thing still has me perplexed.
In an ICE engine, when rings fail, oil comes up into the combustion chamber and is burnt. You know this occurs because carbon will be missing above the rings on the piston. The oil actually cleans the carbon buildup off. Why doesn't that occur in our rotarys?

 

It does at least in some areas. If you look at the rotors of a tear down, you can see where the oil is injected on the sides to cool the apex seals. In those areas, there is much less or no carbon build-up. Rebuilders of rotaries that have gotten rid of their OMPs and relied exclusively on 2-stroke premix will tell you that these engines are cleaner:

 

maintenance is the biggest problem