Wow, just checked and sure enough they did discontinue it...I sold my last 2 stroke a few years ago so it's been a while since I checked...Well, that's a bummer as it was a good 2 stroke oil.
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2-stroke oil?
- Thread starter Zedhed
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Originally Posted By: OilNerd
Hasn't MX2T been discontinued for a few years?
Yes its been discontinued for some time. I have a case still. Its a TC oil (not TCW3).
On premix ratios significantly impacting air/fuel ratio and the need for jetting changes, I've always found this to be an overblown concern. Personally I've never noticed premix ration impacting jetting at all. The Jennings data does not include any jetting changes, was told. Below is the situation described mathematically. As you can see, going from 32:10 to 100:1 premix ratio only changes the air/fuel ratio by 2.2%. Very insignificant given the radical change in premix ratios. Changes in temps, elevation, fuel composition, air restrictions, etc. will have a stronger impact on a/f ratio.
Oil OZ Fuel OZ
4.0 124.0 32 1 NA
3.2 124.8 40 1 0.6%
2.6 125.4 50 1 1.2%
1.3 126.7 100 1 2.2%
Hasn't MX2T been discontinued for a few years?
Yes its been discontinued for some time. I have a case still. Its a TC oil (not TCW3).
On premix ratios significantly impacting air/fuel ratio and the need for jetting changes, I've always found this to be an overblown concern. Personally I've never noticed premix ration impacting jetting at all. The Jennings data does not include any jetting changes, was told. Below is the situation described mathematically. As you can see, going from 32:10 to 100:1 premix ratio only changes the air/fuel ratio by 2.2%. Very insignificant given the radical change in premix ratios. Changes in temps, elevation, fuel composition, air restrictions, etc. will have a stronger impact on a/f ratio.
Oil OZ Fuel OZ
4.0 124.0 32 1 NA
3.2 124.8 40 1 0.6%
2.6 125.4 50 1 1.2%
1.3 126.7 100 1 2.2%
"On premix ratios significantly impacting air/fuel ratio and the need for jetting changes, I've always found this to be an overblown concern."
I'd agree that in most applications, that's correct. Racing engines, on the other hand need every possible advantage to maintain a balance between power and reliability.
A good example to support your claim is the use of oil injection pumps. The amount of oil varies with engine RPM. As the engine spins faster, more oil is injected into the fuel. Oil ratios can vary from as low as 100:1 to 16:1.
Despite that, I believe in keeping the oil on the rich side in premix applications.
I'd agree that in most applications, that's correct. Racing engines, on the other hand need every possible advantage to maintain a balance between power and reliability.
A good example to support your claim is the use of oil injection pumps. The amount of oil varies with engine RPM. As the engine spins faster, more oil is injected into the fuel. Oil ratios can vary from as low as 100:1 to 16:1.
Despite that, I believe in keeping the oil on the rich side in premix applications.
Originally Posted By: boraticus
"On premix ratios significantly impacting air/fuel ratio and the need for jetting changes, I've always found this to be an overblown concern."
I'd agree that in most applications, that's correct. Racing engines, on the other hand need every possible advantage to maintain a balance between power and reliability.
A good example to support your claim is the use of oil injection pumps. The amount of oil varies with engine RPM. As the engine spins faster, more oil is injected into the fuel. Oil ratios can vary from as low as 100:1 to 16:1.
Despite that, I believe in keeping the oil on the rich side in premix applications.
What I was saying is that premix ratio should not impact a/f ratio enough to re-jet. Different matter than what the proper oil mix is for a given application. I agree, a little richer than 32:1 is generally better for most hi-po applications. Problem is that although the a/f is not impacted by premix ratio, as you start dumping more premix in the a/f mix detonation can go up (remember when two stroke oils also had octane booster mixed in).
Variable rate oil volume output of some injection pumps can be disaster on long steep unfavorable grades. If the oil pump volume is governed by throttle position, you can do lots of damage going down hills. Think about it - if you premix at 30:1 compared to the pump running ~100:1 at closed throttle with injection pump - what situation would you rather have going down a long steep hill? Old school survival techniques are to blip the throttle, flick on & off the kill switch or tap the choke when going down long hills. A billion years ago we thermocoupled heads and monitored temps in such conditions and things got hot real quick.
"On premix ratios significantly impacting air/fuel ratio and the need for jetting changes, I've always found this to be an overblown concern."
I'd agree that in most applications, that's correct. Racing engines, on the other hand need every possible advantage to maintain a balance between power and reliability.
A good example to support your claim is the use of oil injection pumps. The amount of oil varies with engine RPM. As the engine spins faster, more oil is injected into the fuel. Oil ratios can vary from as low as 100:1 to 16:1.
Despite that, I believe in keeping the oil on the rich side in premix applications.
What I was saying is that premix ratio should not impact a/f ratio enough to re-jet. Different matter than what the proper oil mix is for a given application. I agree, a little richer than 32:1 is generally better for most hi-po applications. Problem is that although the a/f is not impacted by premix ratio, as you start dumping more premix in the a/f mix detonation can go up (remember when two stroke oils also had octane booster mixed in).
Variable rate oil volume output of some injection pumps can be disaster on long steep unfavorable grades. If the oil pump volume is governed by throttle position, you can do lots of damage going down hills. Think about it - if you premix at 30:1 compared to the pump running ~100:1 at closed throttle with injection pump - what situation would you rather have going down a long steep hill? Old school survival techniques are to blip the throttle, flick on & off the kill switch or tap the choke when going down long hills. A billion years ago we thermocoupled heads and monitored temps in such conditions and things got hot real quick.
Originally Posted By: boraticus
Wouldn't pulling the clutch in and coasting down the hill solve that problem?
yeah but compression braking is usually desired down steep grades ....
Wouldn't pulling the clutch in and coasting down the hill solve that problem?
yeah but compression braking is usually desired down steep grades ....
Originally Posted By: BBDartCA
Originally Posted By: boraticus
Wouldn't pulling the clutch in and coasting down the hill solve that problem?
yeah but compression braking is usually desired down steep grades ....
Not a whole lot of compression braking with two strokes but the clutch could be released as required and a down shift or two to get some engine braking. How long of a hill are you talking anyway? Sounds like some of the hills out in the Rockies that have a 12% grade for twenty miles or so. You won't be seeing me on one of my old RDs out there. That's for sure.
Originally Posted By: boraticus
Wouldn't pulling the clutch in and coasting down the hill solve that problem?
yeah but compression braking is usually desired down steep grades ....
Not a whole lot of compression braking with two strokes but the clutch could be released as required and a down shift or two to get some engine braking. How long of a hill are you talking anyway? Sounds like some of the hills out in the Rockies that have a 12% grade for twenty miles or so. You won't be seeing me on one of my old RDs out there. That's for sure.
Originally Posted By: 47HO
Quote:
Not a whole lot of compression braking with two strokes...
I hear this a lot. Why is compression braking less with 2 strokes?
Very interesting question.
I don't know for sure but as far as I know, engine braking is the process of the reciprocating mass of the engine working under vacuum. The piston has to pull air through the intake/exaust valve without the assistance of the engine's power stroke. Thus the drive train of the machine is running a vacuum pump more or less when decelerating with no throttle application.
I'm only guessing here, but on a two stroke engine, there isn't the same ability to restrict air flow as on a four cycle engine. For instance, on a four stroke engine, the compression/power stroke will have all valves closed creating a lot of vacuum as the piston moves downward without the assistance of combustion of a chamber full of burning fuel. On a two stroke, with numerous intake ports as well as a relatively highly placed exhaust port, air can be pulled into the cylinder with much less resistance.
As I said, I'm not saying this is fact. It's just how I imagine how the physical properties of each engine would relate to a vacuum situation.
Hopefully, more knowledgeable people will chime in to give us a better understanding if my theory is flawed.
Quote:
Not a whole lot of compression braking with two strokes...
I hear this a lot. Why is compression braking less with 2 strokes?
Very interesting question.
I don't know for sure but as far as I know, engine braking is the process of the reciprocating mass of the engine working under vacuum. The piston has to pull air through the intake/exaust valve without the assistance of the engine's power stroke. Thus the drive train of the machine is running a vacuum pump more or less when decelerating with no throttle application.
I'm only guessing here, but on a two stroke engine, there isn't the same ability to restrict air flow as on a four cycle engine. For instance, on a four stroke engine, the compression/power stroke will have all valves closed creating a lot of vacuum as the piston moves downward without the assistance of combustion of a chamber full of burning fuel. On a two stroke, with numerous intake ports as well as a relatively highly placed exhaust port, air can be pulled into the cylinder with much less resistance.
As I said, I'm not saying this is fact. It's just how I imagine how the physical properties of each engine would relate to a vacuum situation.
Hopefully, more knowledgeable people will chime in to give us a better understanding if my theory is flawed.
Originally Posted By: 47HOI
hear this a lot. Why is compression braking less with 2 strokes?
The nature of a 2 stroke engine is that instead of valves, there are transfer ports to direct the incoming air/fuel/oil mixture from the crankcase up into the combustion chamber. These transfer ports do not seal the combustion chamber throughout the full stroke of the piston. Therefore there is less compression braking.
hear this a lot. Why is compression braking less with 2 strokes?
The nature of a 2 stroke engine is that instead of valves, there are transfer ports to direct the incoming air/fuel/oil mixture from the crankcase up into the combustion chamber. These transfer ports do not seal the combustion chamber throughout the full stroke of the piston. Therefore there is less compression braking.
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A bit off topic, but maybe one day we will see a 4 stroke lubed by fuel engine in a bike; like the new Stihl engines. Excellent weight to power and evidently pretty "green".
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