Ok so let me be a bit less vague.

So after reading a bunch of articles on failing engines, and watching a ton of rebuild videos online, and even looking at the junked rotors I got from a user here, I was a bit curious about something. Now I know that the whole redline-a-day method is probably the most common method of engine maintenance amongst rotor heads. That, coupled with premixing has been the golden ticket for some to create a reliable engine with stable compression.

Although it is believed that the 'redline a day' theory would create enough heat to loosen carbon deposits in the rotor housings, which will essentially allow the apex seals to "brush them" away, does this theory work for the carbon that has built up in the combustion pocket on the faces of the rotor?

As I am typing this I am wondering if I have a misconception on exactly "where" the carbon is forming and if the redline-a-day theory is there with a purpose to actually loosen the deposits from the faces.

From the few junked rotors that I have played with, it was obvious where the carbon had baked onto the rotors, and the most prominent location was those combustion pockets. Baked on to a point where I had trouble removing them with a drill using a steel brush bit.

I have just been curious, because there are a LOT of members here who take care of their engines, redline, premix, and still see a failure and replacement engine in their lifetime.

 

The reason for redlining is more to push carbon build up out of the exhaust ports (not to clean the walls of the housings).

Edit: it is also to prevent build up of carbon on the housings BEFORE it has a chance to build up. At least, that's how I understand it...

 

Right I knew that much, I guess I was trying to understand exactly where the carbon buildup is typically occurring .... i assumed that it was forming a thin film over the walls

 

Most of the torn down rotaries I've seen tend to have fairly clean side walls. Mind you, I haven't seen many. Its usually the rotor itself where the carbon tends to build up.

Though I'm by no means suggesting that the walls don't get build up!

I digress, as its too early, I've only had one coffee and I have only the slightest clue what I'm talking about

 

Well what I don't get is why only one of my rotors (tested at 80,000 miles) was bad...

R1 6.6, 6.7, 6.5
R2 8.1, 7.9, 8.0
at 268 rpm

So why only one rotor? Wouldn't some sort of "buildup" be consistent across both?

 

I wouldn't think so ... the two rotors are separated by a center plate. If the spark in one of the rotor housings is bad, then it would affect the combustion in that housing

 

Rotary engines actually have very little consistency, as they are built by hand...

 

So was that rotor doomed from the beginning? It was built 11/03, and so suffered through the earlier flashes for a few years before getting to the "M" or whatever it is.

I just don't want my "new" engine failing the same way, so I too am wondering if being more aggressive with the redlining will preserve it longer. I'll admit that as the car and I aged, I drove it more conservatively and probably only touched the redline a couple times a week after those initial few years.

 

Carbon in the seal grooves is the real problem.
It sticks and occasionally breaks the seals.

Carbon on the rotor face is inconsequential.

 

^^ Exactly what I needed to know, thanks!

So by redlining (which essentially is boiling down to increasing the temperatures of the combustion cycle) we are hoping that the carbon that has built up around the seals to break free.

Just curious though, you mention that teh carbon on the rotor face is inconsequential,... but do you mean that because it would not really be possible for a significant amount of carbon to accumulate inside of the pockets as its generally where the highest flash of heat occurs? I guess I haven't had the tear down experience enough to know if that much actually does build up there ... i only question because I just wonder how it would actually affect the combustion cycle by reducing the size of that pocket due to layers of carbon buildup.

Sorry ... lots of free time at work today lol

 

Once there is carbon in those seal grooves, it wont break free (and you probably don't want it to since it'll break other things).
The idea is to keep it from ending up in there in the first place.

Combustion heat is part of it, but inertia and friction are the main cleaning components.

The layer of carbon on the rotor faces can only get so thick, so once it gets a layer on there, it just gets harder, not thicker. It marginally increases effective compression.

 

Thanks for taking the time to answer sir, def helped clear some stuff up for me

 

I don't but the whole redline a day BS as any type of saving technique. My second motor lasted 74,000 miles and was well maintained and redlined everyday. There are so many variables as to why these motors fail, everyone has an opinion, but there is little actual testing done (well that is shared with us anyway).

My third motor has died (not really still runs fine once warm for the most part except for some misfires) due to a coolant seal failure after 30k. I caught the problem early and parked it so I am very curious to see the internals since it has been premixed, increased oil pressure, SOHN adapter, no cat, BHR kit, etc. since break in.

 

idk about you guys but my 8 is not my dd. between it, f150, subaru legacy (bought for the gf), and my cbr i usually only drive my 8 2-3 times a week. when i do drive it i always redline it more than once a day. i read all of these threads about problems but mine has been great for 3.5 yrs (knocks on wood).

 

Ironically you were the one I was referring to when I mentioned that "users that premixed and redlined" had their engines failed ...

 

So I take it then, all we "know" is...

1) Series 2 engines aren't likely to lose compression, as long as the owner does the routine maintenance (oil changes) expected for any car

2) Series 1 engines, whether originals which suffered through the first flashes, or "new" replacements which have only seen the "M," are a roll of the dice no matter what one does. Some lose compression, some don't, and there's no way to predict or prevent it

Is that about it?

 

Not sure that we really know anything about #1 ... there just isn't that many of us here that have S2's, let alone had them for a time period that would be significant for analysis. For all we know they could just be as prone to failure as the S1 motors. I think "Texas RX8 R3" (sorry if i got the username wrong) had one of the first documented S2 engine failures here, not due to compression loss but e-shaft problems

 

Premixing also helps preventing buildup to some extent.
Something that's often overlooked about redlining is that you actually prevent the intake valves from sticking, that definitely is a good thing.

 

Forgive my naivete and being off topic, but could this be one of the reasons why rotary engines have a reputation for running stronger as it ages?

 

^^ And why using additives like FP+ that claim they remove carbon buildup a bad thing? I bought a bottle just because of the hype over on BITOG ... but maybe its not such a good idea? No data is available saying yay or nay unfortunately.

 

Yeah without any scientific testing it's a crap shoot as to what works. Someone here who had his engine rebuilt by a reputable builder here, had his rebuilt engine fail again despite routine maintenance, using Royal Purple, redlining, premixing, etc. He was pretty bummed considering his rebuilt engine was expensive and was supposed to be better than the original but yet only lasted 30-40k. Not to mention he hardly did any track days on this motor and the original motor lasted much longer and was tracked heavily.

 

This may be a stupid question, but lets say my engine fails tomorrow and I get a replacement .... is there any way to request pictures of the internals when they disassemble? Or is it basically like a "throw the old engine in a ""bucket"" for it to be inspected and rebuilt at a later time"

 

hrm.... so much for a loaded redline forcing the OMP to squirt more juice into the mix...

 

he used synthetic? while i don't claim to be an expert... i've read more than enough saying "synth is bad", compared to the nominal number of articles and threads where people said "yay synth!!! It rocks!!! I'd give it to my 18month old daughter i trust it that much!"

Synth + Rotary = Bad

that's the math i was taught at least.

 

If your talking Mazda, no. Anyone else it would have to be a part of the deal.