2-stroke emissions

[scotia]

I was recently out walking when passed by a number of old scooters - it seems they were holding some sort of rally. They were emitting obnoxious blue fumes from their 2-stroke engines. Do 2-stroke engines pass current engine emission standards?

[Urbandreamer]

Do 2-stroke engines pass current engine emission standards?

The type of engine that you saw CAN NOT pass the emission standards set for 4 stroke engines.

To understand why and why they were emmiting blue smoke you have to understand how both engines work.
In a four stroke engine intake-compression-ignition-exhust take place on one side of the piston. The other is connected to the crank and lubricated.
In the two stroke that you saw intake and compression happen in the crank case. The moving parts still need lubrication and this is done by adding lubricating oil to the petrol. The result is lubricating oil being blown out of the exhust as blue smoke, but a FAR better power to weight ratio than a 4 stroke.

A better explenation may be found here.
https://en.wikipedia.org/wiki/Two-stroke_engine

[bungeejumper]

It's very doubtful whether 30 year old scooters or bikes would pass modern environmental standards, but that might not add up to a reason for banning them from today's roads. For the most part, vehicles are assessed according to the standards that prevailed when they were first built. Which seems fair enough really.

Mind you, I suppose the situation might change, now that various cities have started restricting or banning diesel cars that can't meet the Euro 4 standards. How long might it be before the smoky old two stroke things I used to drive are excluded as well?

They tell me that KTM and Honda are both getting back into two strokes, using a new technology that meets the emission standards. Certainly seemed to be a lot of brap-brap-brappers around in France this year, but they were all motocross types.

BJ

[jackdaww]

having had several 2 stroke motorbikes aeons ago , i have often wondered if it might be possible to retain the advantages without the pollution.

i wouldnt ban old scooters , nor would i ban preserved steam locomotives , which bring pleasure and delight to millions.

just thought - i think diesels are two stokes !!

[Imbiber]

just thought - i think diesels are two stokes !!

Only large marine or railway engines, the need a turbo or supercharger to operate. ( waiting to here of exceptions and proved wrong )

[scotia]

Ok - I knew how 2-strokes worked with the oil mix and the lower efficiency fuel burn, so I probably should have made it clearer that what I was really enquiring about - can (modern) two strokes pass modern emission standards?
BJ responded:-

They tell me that KTM and Honda are both getting back into two strokes, using a new technology that meets the emission standards

I would be interested in knowing how they can do it.
The Scooter rally took place on the Isle of Cumbrae yesterday (in glorious weather). My wife and myself were walking round the Island (about 10 miles in circumference), in accompaniment with the hundreds of cyclists who hire the bikes in Millport. As the scooters passed (driven by mods of 50 years ago) the current generation on their cycles were waving their arms furiously to disperse the fumes.

[bungeejumper]

They tell me that KTM and Honda are both getting back into two strokes, using a new technology that meets the emission standards

I would be interested in knowing how they can do it.

https://newatlas.com/ktm-2018-direct-in ... uro/49541/ seems to be saying that it's partly a matter of fuel injecting straight into the transfer chamber (whereas traditional two strokes inject/squirt straight into the crankcase), and partly down to a better engine management system. In addition, it says, the new KTMs use only an 80 to one petrol/oil mix, compared with the more usual 40 to one.

Hmmm, I could think of a few cars that use a litre of oil for every tank of fuel...….

My first two stroke was a 1953 Francis Barnett which was already 13 years old when I was given it by my uncle. Kinda classy in a retro sort of way! Rather like this one, but with a rigid frame instead (no rear suspension ). https://www.youtube.com/watch?v=DA-EMiQQWxU .However, as the clip makes clear, it wasn't just the smoke that put people off, it was the decibels. Life got a bit more peaceful when I started riding (four stroke) Triumphs....

Snorvey's right, nothing beats a two stroke for power/weight performance or response. Guess they'll have to do something about the noise, though?

BJ

[scotia]

BJ - thanks for the info.
Its interesting that car manufacturers are getting their increased petrol engine power/weight ratio and improved consumption by using turbo technology on 4 strokes. I have a Ford with a 1 litre 3-cylinder turbo petrol delivering 125ps and a Skoda with a similar configuration delivering 95ps. Both delightful to drive with excellent fuel economy.
And if the 2-stroke renaissance doesn't occur, we can always put scooter enthusiasts on 250W Electric Bikes (with supporting pedals).

[MonsterMork]

Never yet met a scooter that smell nice A well-sorted elsie on the other hand ....

Back in the day a common trick was to add just a couple of drops of Castrol R into the tank for that lovely old brit bike experience, but if you were on the pull then half a bottle of Brut 33 was the potion of choice That and the one tenth of a horsepower gain due to the alcohol content

[gryffron]

Be careful what you wish for. A 30yo 2 stroke moped still produces way less pollution overall than a modern euro6 2 ton Land Rover. Which I presume is why 2-stroke mopeds are still allowed and still being built.

Gryff

[Clitheroekid]

Snorvey's right, nothing beats a two stroke for power/weight performance or response. Guess they'll have to do something about the noise, though?

I hate the damn things, and would ban every two stroke engine in the world simply because of the hideous noise they make. Some of the local kids have vile little motor bikes that they zoom around on, and there are few things that get my trigger finger itching so irresistibly

They also seem prevalent in many Southern European towns, and as well as being as noisily irritating as an angry wasp they leave a cloud of stinking fumes.

Ban them all!

Mind you, the same could be said for a lot of 4-stroke motorbikes. Their moronic owners seem to think that their own appreciation of the hideous racket the stupid things make will be shared by the rest of the population - it emphatically is not! It always amazes me that when cars are subject to such strict noise constraints motorbike manufacturers seem to be able to make machines that you can hear a mile away.

(And breathe ...)

[Urbandreamer]

It always amazes me that when cars are subject to such strict noise constraints motorbike manufacturers seem to be able to make machines that you can hear a mile away.

(And breathe ...)

Including the one that said cars must be noisy enough! Seriously, there is a design constraint for EV's that they can't be too quite as that would be regarded as unsafe.
https://www.theguardian.com/environment ... ctric-cars

I confess that I find the subject of engine noise slightly baffelling. I visited the Porsch museam and there it is explained that they put significant effort into getting the 'right' sound. The even have an exibit where you can electronically select aspects of the sound an engine could make. For the race track they make hybrids, but I bet that their cars will always have a certain noise built in by design.

For what it's worth the noise of the 2 strokes that you are thinking about is also by design. There is however a 'honest' engineering reason for it. By tuning the exhust the sound energy can be used to aid the exhust in its job there by further improving the power of the engine.
http://www.prestwich.ndirect.co.uk/tunedpipetheory.htm