Challengine conventional wisdom
 

I came across an interesting response to the question "how much oil is burned in the engine" in the FAQ area on Atkins Rotary's website. Of course the question was concerned with the oil injection system and the resultant oil consumption.

The response was "very little oil is burned, most of it is scraped off and returned to the oil pan".

Keeping that in mind, an noting that oil consumption increases significantly with more agressive driving, it's seemingly clear that the answer provided applies to engines being driven non-agressively. We all know that oil consumption does in fact increase signficantly when our cars are driven agressively.

Combining this with the fact that I've noted significant increased soot in the tailpipe after having driven agressively for a tank or so, it appears that higher rates of fuel consumption, and apparently richer A/F mixtures, perhaps combined with more engine oil being burned in the injection process produces more carbon soot in the exhaust system.

Having said all that, one might conclude that the means, often cited here to keep ones engine from becoming the victim of heavy carbon deposits and lock is exactly opposite of what should be done to prevent such...and that is, redlining the thing daily.


Additionally, since the response from Atkins that very little oil is consumed, it would then be true that driving in non-agressive fashion using a Sohn oil adapter to inject 2 cycle oil into your engine will result in 2 cycle being delivered to your oil pan (noting of course that the oil is more volatile than motor oil and may in fact burn).

What say you on these challenges to conventional wisdom?

i would say that you are going to cause some discussion.
olddragger

I don't know of a path the would return injected oil to the oil pan. It would have to leak past the side seals to get there.

Well, then I'll have done my job then. I'd like to see opinions/experience chime in on this one.

Cheers olddragger.

I had the same question. The assumption on the part about oil consumption is that Atkins knows the design well enough to answer such a question correctly.

If the oil can leak there.....imagine all the exhaust gases that will follow the same path.......


Great compression ;)

Seems like conventional wisdom wins out IMO. Oil is being injected in both a high throttle/high rpm situation and a low throttle/low rpm situation. But if the carbon produced during the high throttle/high rpm is exponentially (or should I say, disproportionately) more than the low throttle/low rpm, then that means that the carbon produced is not being carried out of the exhaust as in the high throttle/high rpm situation. This also brings to mind the selection process for spark plug heat ranges. A spark plug has to have enough heat on the tip to burn off carbon deposits. In the rotary, they've already tried to address the carbon buildup issue by selecting hotter leading spark plugs to keep more heat in (to combat fouling). The fouling issue didn't come from WOT driving, it came from turning your car on and off too soon, cold starts, etc. Meaning that the carbon wasn't being burned off at a sufficient rate by enough RX8's on the road that Mazda felt it necessary to select hotter spark plugs...

Moral of the story, Rev your engine or get a Driving Miss Daisy bumper sticker :)

My question is how the heck does the oil get back to the oil pan?

I don't believe it does. I think they added an extra scraper ring to the 13B-MSP which would have reduced losses going out of the rotors. And they worked to "improve" the metering oil pump. But as far as I'm aware of, whatever gets injected goes bye bye (how would you deal with the fuel contamination issue otherwise?).

Oh and if you're wondering about the other oil, here's a pretty illustration. Learning is good

^yeah, that is what I thought, I was kinda being sarcastic. Once it is sprayed into the chamber it is gone. :)

Thanks for the link though, that is a good vid.

During "spirited" driving my exhaust turns a very light brown.
As far as oil getting back to the oil pan after OMP injection,,, balderdash. It has no way to do it. If there was too much oil being injected (which at this point in time I find highly unlikely) it would just be pushed out the exhaust (port) system. And thus burned by the catalytic converter.

"68. Does the oil in the combustion chamber burn?
Hardly any of the oil in the combustion chamber burns, it is scraped off of the cast irons by the oil rings and returned to the oil pan. "


Above is quoted from FAQ #68 on the Atkins rotary website.

Someone needs to tell Mr. Atkins they're wrong about the oil burning...argue that one with him.

"During "spirited" driving my exhaust turns a very light brown."

I've yet to see this. Nearly all tailpipes I've seen on these cars are blackened with soot to varying degrees. Interesting. Why is it that your car is different than others?

Using one of the theories proposed in this thread, you're building up carbon in your engine since it's not being seen in the exhaust pipe...as this statement might indicate

"But if the carbon produced during the high throttle/high rpm is exponentially (or should I say, disproportionately) more than the low throttle/low rpm, then that means that the carbon produced is not being carried out of the exhaust as in the high throttle/high rpm situation."

Unless of course, your exhaust pipes turn black when you're driving Miss Daisy.

Well, all tailpipes blacken... but if its doing it more than normal, perhaps you should try pre-mixing :lol2:

Anyways, the oil rings on the sides of the rotors are to keep the oil in. They keep the pressurized oil in the rotors from coming out into the combustion chamber. They also have to be tight enough to keep the oil from leaking out when the car is stopped. Like I said before, the oil would become contaminated with fuel if it was returned into the oiling system. Watch this vid, it illustrates what the oil rings are doing. Same thing is stated in a little book called "Rotary Engine" by Kenichi Yamamoto. Atkins is wrong, sorry dude.

I do premix. 4oz of Amsoil Saber Pro+1.5 oz FP+

I don't know where the oil is actually sprayed, although your video indicates its in the induction system. I'm assuming that is correct.
I'd think it would be difficult to escape being burned if true.However, that neglects when it's injected relative to the detonation of the fuel charge.

It'd be difficult for any oil to actually lubricate after being burned, so I'm guessing timing is involved, in relation to the actual fuel burning. That being the oil is injected priot to combustion, not during.


I've downloaded the book you mention (thanks), but haven't had a chance to read it yet.

No need to be sorry. If Atkins is wrong, tell him that.

thanks for the link monkey.. i'm smarter now..

if the injected oil can't possibly get back to our oil pan, neither should gas... but we all know our oil gets fuel contamination

I believe that's from blowby...:uhh:

Edit: I thought about it a little more and it's either blowby or... The film from the injected oil that forms on the side housing wall could be thin enough to allow the oil rings (which are already riding on a film of oil) to pass over the oil and pull it into the pressurized oil path, contaminating the oil. Oil is already being shot at the corners anyways by the injection system... More guesswork... Where's rotarygod when you need his sage advice (pictures rotarygod with walking stick and long white beard divulging the meaning of life in relation to rotary engines)

Actually, that's a good point.

I can see blowby being the cause in a piston engine, not so sure about these rotaries.

Regardless of all that, Atkins is undoubtedly an expert with these engines, doesn't mean he can't be wrong, but it does mean I'd be less likely to doubt an answer to such a simple question.

Blow-By will contaminate the oil with carbon and unburned fuel. The carbon will wear bearing surfaces and the unburned fuel will dillute the oil, effectively lowering the SAE rating.

I'm assuming blow by applied to this engine are fluids getting past the apex seals, that should not, after combustion.

This indicates a path does exist from the combustion chamber to the oil pan.

:icon_no2: These are complex issues and you're not thinking like an engineer...

A path definitely exists - I use a rich pre-mix all the time, and change oil at 4k intervals, and over that period the level will drop about 1 quart/litre.

My assumtion (since we're playing that game) is that some of the pre-mix oil that gets on the side irons is scraped down into the sump oil, a not-unreasonable conclusion, given that 4 or 5 litres of pre-mix oil have passed thru the system in that time.

S

It's not a perfect seal, but that's a limitation of the materials, not a design feature. The original statement he said from Atkins rotary FAQ was that "very little oil is burned, most of it is scraped off and returned to the oil pan" meaning it was intentionally being returned, and that's not the case.

What "conventional wisdom"?

I can tell you - almost down to the gram - exactly how much oil goes into the motor and under what conditions.

None goes "back to the pan". Not by scraping or any other method. The OMP is a dead end.

LMFAO!!!

I won't even go there.