Fuel Difference?

[bearwood.beckham]

Just wondering if theres any fuel difference between 2 & 4 strokes?

E.g. A 4T CBR125 & 2T NSR125...

Thanks

[Mister James]

They both use the same petrol, the difference is that a 2-stroke mixes oil with it to burn, while in a 4-stroke engine, the oil is sealed in the engine - which only burns the petrol.
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[Velocifero]

Why don't you try them for yourself and see what happens

[Jack_Cheese]

[SoND]

2 strokes are a lot less efficient than a 4 stroke.

I think.
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[NSR Mick]

[Jack_Cheese]

2-strokes are less efficient in terms of horsepower per unit of fuel.

a 4t can easily be tuned to be faster by adding nitrous and a turbo or supercharger.

2-strokes can be supercharged, but often require a very high octane race fuel and will go bang very frequently. 4-strokes also have a more linear power delivery, as they have higher torque and lower revs rather than the low torque and high revs of the 2-stroke

Jack
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[KyleH]

theres a reason why pro sports bikes like MOTOGP arent 2 stroke

there mostly V twin and inline 4s

[NSR Mick]

[Jack_Cheese]

Cast your mind back a couple of years, do 500cc 2-stroke Moto GP bikes not ring a bell?

Racing snowmobiles are 2-stroke supercharged monsters, too. There is no engineering reason why they shouldn't be smokers

Jack

:edit: I'm fairly certain motogp doesn't have emissions regulations
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[Jebus]

2 strokes are more powerful for a given cc, without cheating (turbos etc) but that is because they go bang twice as often. they also have a narrow powerband and need help to make useful power at lower revs, thats why they came up with expansion chambers and power valves and all that stuff.

4 strokes are better and fuel and untill they start to get very highly tuned they make pretty decent power all over the rev range, they can still come with 1 hell of a kick but not as mental as a 2 stroke. they also sound a bit less nutty.

but 2 strokes sound great when you give em some revs you can really get them scream and make it sound like the engine is going to fire its piston(s) into your bollox. i think that 4 strokes sound better when they aint getting reved to the limit, and really love a v twin and v 8 rumble.

sorry that was pretty much nothing to do with the topic but got carried away
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2nd time around CBT: 8/9/11
125 Varadero

[Jack_Cheese]

The expansion chamber is just as much cheating as a turbo is, as it artificially compresses the air/fuel mix. It just uses back pressure instead of an impeller or fan.

The powervalve just works like an exup, varying the exhaust port flow rate to allow maximum performance. This is used on yamaha 4 strokes as well as most 125 2-strokes. They are essentially the same system. It is this valve which allows the power curve to be flattened slightly by allowing the flow rate of the exhaust gases to be altered with revs, so without the valve and an open port, the fuel flow is optimised for maximum revs, but by changing the port diameter, it allows the flow rate to be optimised constantly.

jack
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[Jebus]

well ride a 4 stroke without a exup type thing and you are not really going to miss it, ride a 2 stroke with no power vavle or expansion chamber you really will.

but turbos and nos really not that commom on bikes unless a real nutter owns it or a drag bike, apart from the turbo bikes in the 80's
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2nd time around CBT: 8/9/11
125 Varadero

[edd]

[Kickstart]

[NSR Mick]

Keith , always posting excactly what I would say if I could be arsed typing it.
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