Rotax Oil Injection: Friend or Foe?

[GyroRon]

I still believe the oil injection is there mainly to make it easier to use the engine, not for anything else.

Look at the 503's oil injection and tell me this wasn't engineered as a afterthought.

Why didn't the 447 ever come with injection?

And the 582 and 618, being sled based engines, did come with injection... why not though since the sleds had it. Why did the sleds have it... to make it easier to use the sleds, oil in one tank, gas in the other.

Jet skis for example... Most are now four stroke powered, but before switching to 4stk power, they were 2 stroke. All the big 3 seater skis offered oil injection, even some of the 2 seaters. But not every model had it. My jet ski, a Kawasaki SXR800 doesn't have it, and they made this model up till last year, never had oil injection. Same thing with the yamaha super jet which is still in production, no oil injection. Why? Because the people who ride superjets and SXR's are not the same kind of people who ride big 3 seat cruisers, we don't mind pre mixing our gas. We also only have 5 gallon fuel tanks and therefore limited range, so having oil injection where we could fill the oil tank and burn through 3 or 4 tanks of gas is impractical.

If oil injection was so much better for your engine, why would Yamaha and Kawasaki offer jet skis, with warrantys, to the general public, without oil injection?

In nearly every case, if you stop to really think about why any recreational two stroke engine has oil injection, it is clearly there to make the engine easier to use.

Are there benefits from using oil injection, besides making it easier to fuel up the gas tank? Sure. But there is also drawbacks as well.

I don't have a problem pre mixing my fuel. I do 10-15 gallons a week as it is for work and play and have done so for years. It isn't hard.

Talk about it, debate it all you want, but the bottom line truth of the matter is..... As long as you pre mixed your fuel, the engine will not have oil related issues! There is nothing to fail. With the injection, there are many points of failure. This can't be argued.

[DennisFetters]

Originally Posted by GyroRon

I still believe the oil injection is there mainly to make it easier to use the engine, not for anything else.

Look at the 503's oil injection and tell me this wasn't engineered as a afterthought.
Why didn't the 447 ever come with injection?
[/U][/B]

Well, I don't know about the other brands or applications you mentioned, I only went to the Rotax Aircraft engine overhaul and maintenance schools in Canada, so I will only give advice on what I know for sure.

Yes, oil injection came out later on the 503's and it was an afterthought, so they had a reason. The 447 was discontinued so there was no need to make the upgrade.

But, you are right; people are going to do what they want no matter the logic presented.

[Not Yet]

The new SDI & DI Rotax sled engines must be oil injected because no gasoline is ever in the crankcase.
The 2009 Ski-Doo 600 E-TEC is one such engine.

[DennisFetters]

I found this published by Published by Aero Population Technologies and thought it was a good addition to this thread;

Why Choose Oil Injection on Rotax Aircraft Engines?

All Rotax 2-stroke Aircraft Engines (except the 447 UL) are now provided with an oil injection pump. But because of a lack of an adapted mounting system (as is the case for the Quad City Challenger / Challenger II Ultralight), or because of dubious superstitions, some planes are still not equipped with oil injection.

The principle of oil injection rests in the separate intake of oil and fuel/air mix rather than the premixing of both. An engine driven pump regulates the flow of oil and injects it into the engine via the intake manifolds. Such systems have been used on 2-stroke engines since the early 60s, but it is only since 1989 that Rotax has been using them on their aircraft engines, starting with the first 582 UL. Faithful to their tradition of reliability, Rotax waited for the system to be thoroughly proven before using it on their 2-stroke aircraft engine range.

Advantages:

•More convenient
No need to premix your fuel. Simply fill up with pure fuel and ensure that your oil tank is always topped up.

•Less carbon accumulation
The major part of carbon accumulation in 2-stroke Aircraft Engines takes place at idle, a speed at which they do not actually require as much as a 50:1 ratio of oil. The oil injection pump regulates only 70:1 at idle, therefore limiting carbon accumulation. At higher RPMs, the ratio is brought back up to 50:1.

•Less engine wear
The lower amount of oil at idle also helps prevent the wear caused by excess carbon deposits.
With oil injection, the oil circulates through the engine better and ensures better lubrication. Furthermore, the alcohol contained in the majority of fuels reduces the oil's lubricating efficiency when pre-mixed. Oil injection prevents this reaction from happening and ensures that the oil maintains its peak efficiency.

•Cleaner inside
When oil injection is used, only pure fuel flows through the fuel system and carburetors, keeping everything clean. Otherwise, when premixed fuel evaporates, it leaves the oil's varnish deposits behind, quickly contaminating the fuel system and carburetors.

•Cleaner outside
An oil injected engine's emissions are reduced thanks to the lower oil ratio at idle. In addition to the environmental advantages, the difference becomes quickly obvious in terms of exhaust deposits on your aircraft and propeller.

•Eliminates the risk of pre-mixing mistakes
How many times did you ask yourself if you did put the right amount of oil in your fuel? Or if you even forgot to add it? Those risks are completely eliminated. Simply keep the 2 liter (about 5 hour's flying capacity) tank topped up. A level sender can even trigger a warning light on your instrument panel to indicate low oil.

•Preserves octane rating
Most 2-stroke engine oils cause the fuel to lose up to two octane points when pre-mixed.

Installation criteria

•The tank should be placed so that its outlet is always higher than the pump under any flying attitude, so that the pump is always gravity-fed.

•The oil line and oil filter have to match Rotax standards.

•A few precautions have to be taken during the first run: It is important to bleed the system to free any air bubbles; the oil injection lever cable has to be adjusted so that the marks on the lever and pump align at idle; the first tank should contain 100:1 premix to ensure that the engine will receive adequate lubrication while any last air bubbles go through.

Don't wait!

•On a new engine:
Your new engine will be provided with an oil injection pump. You will just have to add an oil injection tank and a 3-way throttle control cable to actuate the pump lever in addition to the two carburetors.
Note: Certain manufacturers (notably Quad City, manufacturer of the Challenger) provide an engine without oil injection with their kit. It is more advantageous for you to buy your engine through us since for the same price you will have oil injection included.

•On an existing engine:
Most existing engines of types 503 UL, 582 UL and 618 UL can have oil injection retrofitted. You need to add an oil injection pump and change the intake manifolds. You will also need the oil injection tank and a 3-way throttle control cable to actuate the pump lever in addition to the two carburetors.

[Penguin]

I'm experimenting with pre-mix while making a cake. Following the argument that if I pre-mix, every bite would always have frosting, I pre-mixed the frosting with the cake mix, guaranteeing that every bite always had frosting.
The result was neither a good cake nor a good frosting.


As Dennis' article indicates, adding oil to the gas lowers the octane of the gas. And adding gas to the oil reduces the efficacy of the oil.

[Earthboundmisft]

Interesting...
Every carbureted 2 stroke Mercury outboard uses the Mikuni oil injection pump.
The oil exits the pump, and is entered into the FUEL LINE,
then goes to the CARBS.

[Penguin]

Originally Posted by Earthboundmisft

Interesting...
Every carbureted 2 stroke Mercury outboard uses the Mikuni oil injection pump.
The oil exits the pump, and is entered into the FUEL LINE,
then goes to the CARBS.

Actually, the oil injection pump feeds the fuel line before the fuel pump which then feeds the carbs. Merc may be using the fuel/oil mix to lube the fuel pump as well.
There is a big difference between oil in a fuel solution for weeks/days/hours as opposed to injecting it at the last practical point before introducing it to the crankcase.

[opsled]

Originally Posted by Penguin

Actually, the oil injection pump feeds the fuel line before the fuel pump which then feeds the carbs. Merc may be using the fuel/oil mix to lube the fuel pump as well.
There is a big difference between oil in a fuel solution for weeks/days/hours as opposed to injecting it at the last practical point before introducing it to the crankcase.

Yamaha started injecting into the fuel lines prior to pump in 1983 on sled engines. Later setups had ports right on the pumps for injection lines. It's a great setup. As far as I know they were the first to come up with an injection system for oil on a two stroke. That happened back in the 60's on street bikes. As others said it was mostly a convenience issue to make a production machine more user friendly. It would also help eliminate user error in premixing that could damage an engine.

Old fuel is junk premixed or not. In my opinion premix is just as good as oil injection if done properly. Oil injection is easier to deal with. Personally I like oil in my carbs for many reasons but I don't like to premix so I like the injection into line/pump system.

If a person knows what they are doing there is nothing wrong with premix.

opsled

[themonarch]

Back in the 80's I was into having my sno-mo engines modded. I wanted something faster than stock, no matter what stock. At that time Yamaha was injecting the oil into the fuel lines, upstream the carbs. Performance shops such as PSI Peformance, Wild Rose Wisc., were concerned that this method lacked proper timing when considering rapidly changing engine rpm's. Subsequently PSI encouraged oil injection into the intake manifolds to better "time" the best ratio of oil to gas to the particular engine rpm. I made these changes to my systems because it made sense to me. If there was a burndown it was not due to lack of oil, but lapse of proper timing of overall fuel delivery. Eventually I eliminated this variable by reverting back to pre-mix. Proper carbureator calibration is everything folks, remember, for this is key. Especially with 2 strokes. MJD.

[bryancobb]

JUST THE FACTS SIR!

* No debate about injection being convenient
* No debate about less ring-groove clogging and plug-fouling
* All other aspects can be argued and debated.

My friend just this past week sent his grayhead Rotax 582 to a highly respected and well known rebuilder for a complete 300hr rebuild. The rebuilder, has been an A&P/I.A. for deacdes, and has worked on hundreds of general aviation engines. For the last ten years, he has almost exclusively worked on Rotaxes.

My friend's engine was rebuilt at 300 hours TTE, before he bought the Kitfox III it has always been in. Now it has just over 600. I can't remember if it got a new crank at 300 or not. It does have very complete logs, so he knows every part ever replaced and how it has been operated.

After disassembly, the guy calls my friend to report what's needed. He reports "Everything looks great. However you have been operating it has served you well. The ring grooves are very clean and the rings were free. The crank looks great and doesn't need replaced. It's perfect. All you need is pistons and rings and the cylinders need to be put back to non-worn geometry. (In 600 hrs you would EXPECT some wear)" He also said "There was some carbon buildup on the crown of the pistons."

Then he tells him all the changes he suggests like REMOVING THE OIL PUMP, CHANGING THE JETTING, AND CHANGING OIL TYPE AND MOVING THE JET-NEEDLE CLIP POSITION, AND CHANGING THE IDLE JETS, ETC ETC!!!!"

I don't get it! If the crank is perfect and the rings free, And my friend has flown 300 hours with ZERO issues and no engine failures, I don't understand why this EXPERT wants him to make ANY changes! If it ain't broke, don't fix it.

Now I understand that a fresh engine MAY require jet changes because, in theory, it will be a tighter, more efficient air pump now, but if I was the expert, I'd say..."DO NOT CHANGE A THING! JUST GET THE NEXT 1 OR 2 LEANER MAIN JETS AND NEEDLE JETS JUST IN CASE IT'S TOO RICH ON THE ONES YOU HAVE BEEN USING.

[Penguin]

@bryancobb - But you are overlooking the tremendous horsepower increase from removing the oil pump. Not to mention the weight reduction.
Vroom vroom!

[bryancobb]

Originally Posted by Penguin

@bryancobb - But you are overlooking the tremendous horsepower increase from removing the oil pump. Not to mention the weight reduction.
Vroom vroom!

Horsepower is in the form of "pent-up" energy in the gasoline. I can't get my mind wrapped around how having MORE oil in the gas, and the tiny energy loss in spinning an oil pump shaft robs a TREMENDOUS" amount of horsepower. You have GOT to

When oil-pump removal/pre-mix advocates show me certified dyno-plots and I'll remove every oil pump myself!

[Penguin]

Parasitic drag - probably good for 15 or 20 hp, right?
Nahh. I'm messing with ya.

[bryancobb]

Originally Posted by Penguin

Parasitic drag - probably good for 15 or 20 hp, right?
Nahh. I'm messing with ya.

LOL! I posted it without finishing my last sentence that said "You have got to BE joking."

[themonarch]

No matter what, diesel, (especially diesel), 4 stroke gas or 2 stroke gas, being oil injected or not, they All run rich cold. We expect that. You see a lot of extra smoke from a cold diesel then less from a two stroke premix. Even less from a two stroke oil injection and finally least of all, less smoke from a cold 4 stroke. I don't know about kerosene turbines maybe someone can chime in here about that.

Because on cold start my pre mix 582 shakes too much and spews a lot of smoke (not that smoke is so important as long as nothing is on fire! ). I asked the tech's at L.E.A.F. "how long do I have to wait before I can raise rpms to 2600 to get away from these disturbing annoyances?". The response was "go direct to 2600, this will not hurt the engine". By the way, as I am told, at 2600 you go past the sprag clutch if you have one, so what good the sprag clutch in this cold engine situation? Probably a clutch has benefit in other situations. I am not taking issue here, only musing.

I am not sure that going quick to higher rpm's at cold start really is okay. I think that it depends on how cold is it at the time, so you have to know your feel for things.

My experience is that pre-mix is not really loading up your engine as compared to oil injection. It's just a cold two stroke, that's all. The engine is cold for only few minutes, then it's all whisked away by more gas, higher engine temps and rpm's so no matter. I feel that it's more important the choice of oil. By my experience I prefer synthetics. Pre mix or Autolube? To each their own. MJD.