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.

Look fellas, it was Mr Atkins who stated that the oil is mostly returned to the pan. Clealy under heavy loads, that's just not true as our oil consumption increases dramatically.

On the other hand, during light loads, the oil consumption is minimal, and is comparable to many piston engines in good condition.


So then, under lighter driving conditions where 1/2 quart of engine oil is burned in 3000 miles (some I've heard have done less).

Assuming the oil is burned as an intended process of normal combustion, then that's a fuel to oil ratio of 1200:1. Not much oil in there eh?

How long does oil stay in a low load/low rpm situation with an omp that likes to inject? I'm guessing it burns out in 1-2 revs?

Feel free to go there if you wish :)


Man... that Oil Metering Pump, fancy stuff right there. :rolleyes:

Tell me then, exactly how does an engineer think and while you're at it, why not answer the poster's question as to how to install his temp control knob.

An engineer thinks in Blue, you think in Magenta. And an engineer doesn't do installs, he does designs :cool:

My god man. Give it up. Having been an engineer for 20+ years, I'm yet to think in blue. Back on topic, where you unwittedly admitted that the challenge was a good one....and it's yet to be disproven by anything but your limited sample space.

Man, at least you have an engineer's sense of humor... :eyetwitch

I'm unsubscribing from this thread, 20+ year engineers who think they're going to re-invent the wheel feel free to take my place :dunno:

Now that was a huge transition...from 'hey this is a very complex topic, you're not thinking like an engineer' ...and now, suddenly redundant.

Did you ever think that the AF's are such that all the fuel is getting burned? Hence no carbon choking my engine or exhaust. That would make Al Gore happy now wouldn't it. A engine properly tuned should not leave carbon behind internally.
I have lots of people including the dealer and technicians that have seen this in my exhaust.
Seems to me there is a thread that I recall about someones track time and how White the exhaust pipe was.

Well, let's see. Complete combustion of a hyrdrocarbon results in carbon dioxide and water, and of course is an exothermic, in the case of gasoline, a very rapid exothermic reaction.

Additonally, under ideal conditions the A/F ratio for combustion of gasoline is 14.7:1 at standard temp and pressure Since precise temperature in the combustion chamber is not measured, and the O2 sensors have non-uniform response and are the only method of feedback into the A/F control measures, the probability of complete combustion is minimal. In addition to unburned hydrocarbons, cars produce carbon monoxide, oxides or nitrogen and other compounds in their combustion chambers. If complete combustion occurred, we wouldn't have catalytic converters, since their job in life is to produce that ideal CO2 and water exhaust. Of course you could google this stuff if your had an interest...a quick search yielded these simple chemical equations.

C(x)H(y) +O2 —›H2O + CO2
CH4 + 2O2 ---› 2 H20 + C02

So to answer your question, yes, I have thought about it.

Where the brown stuff comes from, I'm not sure. I'm sure Al Gore is full of it though.

This thread should be retitled "Challenging Conventional Spelling"

Ahh, spelling. The internet and intellectual equivalent of the Curly defense. Ya! Ya! Ya!


Oh well....on to the next discussion about changing air filters, oil and spark plugs.

I was referencing the thread title, not your response.

This thread was anti-informative from the outset.

+1
(though I tried to put out some quality information).

Over time, engine oil turns black, even in the rotary. Therefore, there definitely IS a path from the combustion chamber to the oilpan.

Still leaves open the question of how much injected oil might be able to take that path. It could be answered if someone is using an external oil tank; choose a 2-stroke oil with an additive that your sump oil doesn't contain. Then do a used oil analysis at some point and see how much of that additive finds its way into the sump oil.

Hello Charles,

While it may be true that the question/answer in #68 is about oil burned outside the OMP, I'm less in inclined to believe that than think it's referring specifically about the OMP since that's the source of oil being burned an why the rotary engine has the "reputation" for being an oil burner. Also, he said most of it is "scraped off" and I'm assuming he meant its scraped off instead of being burned in the combustion chamber.

The question's answer, for my stock RX8 is correct when the car is driven normally, OMP or not. Since the car consumes about 1/2 quart in 3000 miles of normal driving. MY LS1 used nearly that much.

This subject is brought up a lot, along with the carbon produced by these engines.

The conventional wisdom being challenged is:

(1) the cars engine is "cleaned" of carbon by driving it hard. I don't see Atkins stating that as a method for keeping our engines from having the carbon lock problem and in fact I observe far more carbon in the exhaust having driven it agressively vs. normally....carbon being the product of incomplete combustion of either gasoline, oil or both.

(2) The usage of the sohn oil adapter. if the questions answer was taken from the correct context, woul have to result in the

So one question I have is how much oil does the OMP deliver as a function of RPM, throttle position, and whatever other variables are used by the PCM to control the flow rate. I am assuming the OMP has direct or indirect electronic flow control only by the fact the PCM reflashes affect it.

If it could be derived to be 1200:1 at normal driving speeds for example, then at 1/2 quart and 3000 miles the oil it's delivering is in fact being burned.

But 1200:1 doesn't sound like an amount that will effectively lubricate anything.

Dig,
You are right about lack of lubrication---but,you may want to read a long thread on the OMP that was discussed in detail, along with possible modifications.
I think Ray is correct concerning the Adkins statement. Seems very lodgical to me.
In response to your questions
1- have you tracked your car? If you have not then you havent driven it hard -- i think that is the definition most of us except. Redlining it a couple of times a day is not driving it hard. By tracking the car(not drag racing) the engines temperature is hotter than normal, the oil temps are hotter than normal and the amount of air being pumped through the engine is maybe 100 fold. Any one that has tracked their car will tell you that the engine runs better for a while after they do. Tailpipes do run lighter on the track. The pcm is not doing any short or long time trims at the track rpms/load and the mix may become a little leaner --i really dont have evidence for that--just a thought.
But, to summerize--high temps, high air flow, high fuel flow through an engine does have a slight cleansing affect.
The rotary has a rep as an oil burner simply because it is injected into the combustion chamber --not unlike a 2 cycle engine.
Remember one thing also---all engines have some blowby----alll.
olddragger

Charles,
Here's the question from the FAQ on their website and the answer, cut and paste style:

"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. "

Since they say "In the combustion chamber" I assumed this meant injected oil.

I see only 2 possibilities with Atkins statement. 1 is that he got confused when typing the answer. The second possibility is that the question is worded in a way that is confusing and is intended to ask something other than it implies.

If the question is "How much metered oil is burned in the combustion chamber?", then his answer is all wrong. Some of it gets burned. Some of it goes out the tailpipe and yet some more of it forms carbon deposits. The easier you drive, the less of it gets injected and less of it goes out the engine and more of it builds up inside. The harder you drive, the more that gets injected and the more that gets burned, expelled, etc. Less tends to build up inside as carbon deposits this way. All forms of driving will result in soot buildup on the tailpipes and harder driving may result in more soot on the tailpipes as more went out the exhaust.

If the original question was "How much non injected oil gets past the side seals and burned in the engine?" then his answer would be correct. Oil is sent through the rotors to cool them and this oil drains out the sides of the rotors. Since it hits the side housings in the process, the oil control rings scrape it off and send it back down to the pan. The oil hitting the side housings does not do so to lubricate anything. It's just the way it flows out of the rotors. The oil control rings are just that, control rings. They control the return flow of oil to the pan.

This all assumes that everything in the engine is doing it's job properly.

This oil lubricates the oil control rings' travel on the housings. :)

Ah Jeez!
OD

and yea Ray--I do remember that! Always a search for the best premix and the right plug and keep 2 extra plugs in your pocket---especially before truely digital ignitions and ported 2 cycles with larger venturis!!
I can remember the popping.
olddragger

Hello Old Dragger,

Although I'm sure it's fun, and expensive, I don't track my car. Perhaps I should as traffic around here lives little room for actually driving it.

As for many threads on this subject, my reason for posting it here had 100% to do with what the Atkins site said which is, assuming he was referring to injected oil, is inconsistent with the advice given in many threads on this site. that advice being that the car must be redlined once a day to prevent carbon buildup and that the carbon buildup is due to incomplete combustion of the oil in the combustion chamber.

I added the fact that I know more carbon is in my exhaust pipes when I drive it hard, and more oil is burned. and combining those two might lead one to believe that driving hard does exactly the opposite of what is the advice, or conventional wisdom would have us do.

Not an unreasonable line of thinking.

Also, I am considering the Sohn for my car, but perhaps not if my motor oil will be mixed with injected 2 cycle.

Charles/Old Dragger/RotaryGod...

I'm simply trying to learn from those more experienced with this car than I.

There are many variables at work in these engines of course, and in combination they're pretty complex. The only way to learn about them either be involved in the engineering of such systems or having practical experience using them and I've been exposed to neither.

When I see experts, whether they be of the variety who've acquired knowledge through practical application and hands on experience, or gained in the engineering design of these engines, seemingly contradict one another, I ask questions and challenge the answers.

Long term testing under tightly contolled conditions with large sample sizes will yield outcomes that are useful to predict the behavior of these engines. I'm trying to use your communicated collective experiences in place of that.

Don't ever be scared to ask a question. Of course this also means that you shouldn't ever be surprised if you are told to search!!! ;) We all learned from someone somewhere.

Hey NP man---you should have seen the questions i was posting in early 2004--this being my 1st rotory engine!
Answering questions/ challanges is a hell of a lot better than playing sudoko for my old brain:) I am more than willing to share my rotory experiences.
This carbon issue is real and since we have a 270 degree flame front and need to run rich at times to help keep tempertures down etc--we are going to have carbon issues. We are going to have lubrication issues also. And it is not just on the rotor housing. You should see some of the eccentric front bearing wear at 50K.
There are things that can be done to help with the carbon, just as there are thing that can help with the lubrication.
With the current omp and the fuel system we now have --we are challanged.
Keep the questions coming.
olddragger