Rotax Oil Injection: Friend or Foe?

[opsled]

Originally Posted by 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.

I like my oil injection but have no issues with premix and use it too depending on what the engine is being used for.

Dynotech, PSI, Bender and others all scoffed the Yamaha system of injecting into the fuel stating the reasons you describe.

Problem is they were/are wrong. There argument is based on the belief that oil injection varies the ratio of oil/fuel mixture for various rpms/loads. If that were true they would be correct.

Fact is that oil injection is designed to keep the oil/fuel ratio constant and consistant with the fuel use rate. The oil/fuel ratio in the carb bowls on the Yamaha system is always the same. The aftermarket direct injection systems sold by these companies didn't hurt anything but they were sold under a false premis and were not needed. A lot of wasted money by consumers.

Personally I havn't seen a bad injection system yet. Some use better quality components than others. Some are more prone to failure but I havn't seen anything that would cause me to call them all junk. I also don't think there is any real world proof that premix is bad or not as good as injection.

Test results are often scued to reflect the objective of the test.

opsled

[Penguin]

Originally Posted by opsled

Fact is that oil injection is designed to keep the oil/fuel ratio constant and consistant with the fuel use rate.
opsled

I'm pretty sure that is incorrect.
All modern systems vary the oil injection with throttle position. The Rotax range is 100:1 at idle and 50:1 at full throttle.

[opsled]

Originally Posted by Penguin

I'm pretty sure that is incorrect.
All modern systems vary the oil injection with throttle position. The Rotax range is 100:1 at idle and 50:1 at full throttle.

You are correct in that all two stroke oil injection systems vary their rate "ratio" with throttle position and that they are variable rate "ratio" pumps. They have to be in order to keep a consistant oil/fuel ratio under all rpm/load conditions.

The oil pump has two methods of increasing the amount of oil it pumps. One is with rpm from it's drive. Increase rpm and oil flow increases. The other is by increasing the stroke on the pump which is done by moving the arm on the pump. This is seperate from the drive and tied to throttle to compensate for increase fuel use rate because of load.

An engine under no load can achieve 6000 rpm with very little throttle and very little fuel consumption. An engine under full load will need much more throttle to achieve 6000 rpm and with the increase in throttle it will use more fuel. The variation of oil flow because of rpm is not enough to be consistant with these two senarios. In order to keep a consistant ratio at all rpm and loads the pump must have the ability to increase oil flow rate to match fuel use rate. That's why the rate is increased with the ratio change via a connection to throttle position.

A variable rate or "ratio" pump is a MUST have in order to keep consistancy in all rpm/load conditions.

opsled

[akoschier]

I for one ruined a very expensive Hirth 3701 with Carbon Pistons due to an injection pump failure. The Carbon pistons made the failure benign - gradual power loss- but the engine stopped after a few minutes and seized. Taking the exhaust manifold, off blued needle rollers from the connecting rod bearing fell out. Sent the engine back to Hirth who initially did not want to believe the pump had failed. Have not heard from them back yet.
This was the end of me using 2 cycle power.
avk

[Stan V]

It's been said here before, friends don't let friends fly with a Hirth. I sold my BD5 last week, when they first came out, the Hirth was its bigest failure, the Turbo Honda made it a much better and safer plane. PRA 41973

[Redbaron]

Originally Posted by Stan V

It's been said here before, friends don't let friends fly with a Hirth. I sold my BD5 last week, when they first came out, the Hirth was its bigest failure, the Turbo Honda made it a much better and safer plane. PRA 41973

They only hirth one time. :-)

[opsled]

The snowmobile industry quit using Hirth in and around the mid 70's.

They only had to walk home when one went down..

So,,,,

opsled

[themonarch]

Opsled, say no.. You can't mean the 650 Hirth Red Baron? Tug tug tug on a humgous two cyl. two stroke. (It won a few in it's day). Opsled, you are approaching being sacraligius, mind you sir! Best be carefull if the ole time sledders find out what you say.. I'll stay mum. MJD.

[opsled]

Originally Posted by themonarch

Opsled, say no.. You can't mean the 650 Hirth Red Baron? Tug tug tug on a humgous two cyl. two stroke. (It won a few in it's day). Opsled, you are approaching being sacraligius, mind you sir! Best be carefull if the ole time sledders find out what you say.. I'll stay mum. MJD.

LOL, The Hirth engines are still alive and runnin in the vintage world. They were used in many machines back in the day and there is no shortage of love for them. I've owned two in my life and wish I still had them. One was an 800 free air tripple in a Rupp Magnum and the other was the famous 650 Red Barron in a early 70's Air Cycle hovercraft. (google it, they were cool).

No oil injection though, a bit early for that. There were many such engines back then from many other manufacturers. Most are gone now.

Cool stuff though,

opsled

[CLS447]

OK.....what's up with this ? I got 2 stroke oil dripping out the bottom of my dual air filter. (503DCDCDI)

It would seem that oil is draining out of my tank, through the pump,through those small hoses, into the intake , through the carb throat , & out the air filter,& onto the floor !

My oil tank is mounted up the mast, about a foot higher than the pump. I refuse to install a shutoff valve on the tank for obvious reasons.

Is this typical or are my check valves not working ?

This is a great reason for my intakes & carbs to tilt away from the engine.

What do ya think ??

[Penguin]

Chris - I don't think it is happening as you describe.

Try this for verification - pull the tops on your Bings and lift the slides out. I suspect that you'll find them well coated in 2-stroke oil. That's what I observe on my 582. IMO, no amount of leakage could result in oil backing up onto the slides. It would simply run out the carb and onto the air filters.

I believe that a mix of gas and oil is being blown back from the intake as a result of reversion. This is equally true with oil injection or premix. You may also observe a puddle of 2-stroke oil under the air filters has formed over night. Again, not leakage, but the result of the air filters getting 'wet' from the fuel/oil mixture, the excess dripping out, and the fuel evaporating.

You are right - don't put a shutoff on your oil supply in any case. But you might try marking the oil reservoir with a bit of tape and pencil just to reassure yourself that oil is leaking by the oil injector overnight.

I hope this makes you feel better that everything is up to snuff.

[DennisFetters]

Originally Posted by CLS447

OK.....what's up with this ? I got 2 stroke oil dripping out the bottom of my dual air filter. (503DCDCDI)

It would seem that oil is draining out of my tank, through the pump,through those small hoses, into the intake , through the carb throat , & out the air filter,& onto the floor !

My oil tank is mounted up the mast, about a foot higher than the pump. I refuse to install a shutoff valve on the tank for obvious reasons.

Is this typical or are my check valves not working ?

This is a great reason for my intakes & carbs to tilt away from the engine.

What do ya think ??

I think ya got a banjo valve leaking.

[GyroRon]

Originally Posted by Penguin

Chris - I don't think it is happening as you describe.

Try this for verification - pull the tops on your Bings and lift the slides out. I suspect that you'll find them well coated in 2-stroke oil. That's what I observe on my 582. IMO, no amount of leakage could result in oil backing up onto the slides. It would simply run out the carb and onto the air filters.

I believe that a mix of gas and oil is being blown back from the intake as a result of reversion. This is equally true with oil injection or premix. You may also observe a puddle of 2-stroke oil under the air filters has formed over night. Again, not leakage, but the result of the air filters getting 'wet' from the fuel/oil mixture, the excess dripping out, and the fuel evaporating.

You are right - don't put a shutoff on your oil supply in any case. But you might try marking the oil reservoir with a bit of tape and pencil just to reassure yourself that oil is leaking by the oil injector overnight.

I hope this makes you feel better that everything is up to snuff.

I agree with what larold just said above

[CLS447]

Great ! That'll keep that K&N well oiled !

[Penguin]

Originally Posted by CLS447

Great ! That'll keep that K&N well oiled !

Not really, but I think you know that.
The oil just drools out the bottom of the filter.
Assuming you have a K&N, it needs to be pulled, cleaned and oiled regularly.