the clean two-stroke thread

[Flettner]

No good, it's a diesel. Diesel is dead, too much particulates to deal with.
My new truck has lost approx 150 kl off its range over the old one. Particular filter is the fault.

[WilDun]

No good, it's a diesel. Diesel is dead, too much particulates to deal with.
My new truck has lost approx 150 kl off its range over the old one. Particular filter is the fault.

Yep, but I'm referring more to the engine layout than the type of fuel - think there must be a way round the cooling of that piston if using petrol!

New isn't always better! - I always used to wonder when in the past they didn't seem to worry about diesel emissions - in Auckland the cretins turned down Robbie's Rapid Rail idea and replaced the electric trolley buses with diesel buses - morons!

As for that (OP) system using petrol with HCCI (which apparently runs well staying at higher revs, but has to keep changing back to the "normal" system when revs get lower (depending on demand) - the idea of a "semi Hybrid - ie hybrid style transmission with the bare minimum of battery capacity - most of the time the engine will be operating at its most efficient revs (relieved of the chore of having to accelerate and decelerate constantly) no need to go up and down the rev range, surely that must have some merit?
But no doubt I will have overlooked something, somewhere!

[Flettner]

Why compromise?
Why not HCCI at all revs?
It can be done, rendering spark plugs and ignitions to the rubbish bin.
Seemingly silly experiments can lead to intetesting results 😆.

https://youtu.be/TOHKls3Cxjs

[husaberg]

i will have to dig out the one with the project leader.

[Flettner]

Honda still needed a sparkplug.

[husaberg]

Honda still needed a sparkplug.

Yes the did and according to them it gave less emissions than a equivalent 4 stroke at the time.
the ARC was to autoignite at low to mid revs.
ie 5%-60% load ie the time when it would be prone to 4 stroking.

Opening up the throttle on the Baja-winning EXP-2, I aimed the bike down a desert trail at the dust storm following test rider and former Baja winner Bruce Ogilvie. As the EXP-2 blasted off down the trail, its engine note changed from a two-stroke burble to the clattering of pre-ignition.
Ignoring the warning of impending doom I opened the throttle wider and hung on.
Every other two stroke in the world would have seized solid, right then. But the EXP-2 pulled away without protest.
What's different about the EXP-2 is the weird, muted note to the exhaust -- like a watercraft -- and the clattering noise of pre-ignition (commonly referred to as knocking or pinging) at low- to medium-throttle openings and engine RPM.
Honda has tamed pre-ignition; on the EXP-2 this auto-ignition is computer controlled to enhance performance and most importantly virtually eliminate pollution.
Usually thought of as a bastion of four-stroke technology, Honda's new two-stroke design promises less pollution, better fuel economy and most important, no loss in power.

Pre-ignition will destroy a normal two stroke. It is caused when the temperature and pressure in a cylinder builds to a critical point and the air/fuel mixture ignites prematurely in a violent explosion rather than in a controlled burn.
The premature explosions are ignited either by red-hot engine parts or highly ionized reactive molecules left from the last exhaust cycle.
Using premature combustion to more thoroughly burn the mixture is not a new idea -- diesels don't have spark plugs either.
But it's the first time that auto-ignition has been successfully applied to a gasoline two-stroke.

Above idle, and below 40 percent throttle, the spark plug is not used. The exhaust power valve automatically regulates combustion pressure, guaranteeing that pre-ignition will start and end at the correct time.
Once the critical pressure is reached, the reactive molecules act like millions of tiny spark plugs, firing the mixture much more evenly than any single plug could.
Honda claims that when the ARC is engaged, carbon monoxide and carbon dioxide emissions are 15 percent lower, hydrocarbons are down 80 percent, and Nitrous Oxide emissions are down 90 percent...'
Before the emergence of microprocessors, engine management systems were not precise enough to control combustion pressure at all engine speeds.
However, with a computer controlled exhaust valve (shown below), pressure in the combustion chamber can be precisely controlled, so pre-ignition can be timed as precisely as an ignition spark.
The engine control unit relies on throttle position and engine speed sensors, and uses a knock sensor to detect low-octane fuel.

The EXP-2 uses two electronic fuel injectors (shown at right) but engineers at Honda say carburetors would work just as well. Honda claims that when the ARC (Activated Radical Combustion) is engaged (from idle to about half-throttle) carbon monoxide and carbon dioxide emissions are 15 percent lower, hydrocarbons are down 80 percent and Nitrous Oxide emissions are down 90 percent compared to conventional engines. At idle and at high throttle openings, ignition is by spark plug and emissions are similar to other two strokes. Why did Honda bother? In case you haven't heard, there are restrictive exhaust emissions laws coming down on motorcycles in many countries. Due to their greater emissions two-stroke have been especially hard-hit. Two-strokes are no longer legal for road use in the US and some countries in Europe may ban them.

In California two-strokes will soon be illegal for off-road use except on 'closed courses'. A sad story-until Honda came along offering new hope with a radical new design.
Not content to merely run the new EXP-2 (for experimental two-stroke) engines on the dyno, Honda built a couple of trick off-road rally bikes and entered them in three grueling rallies to race against the best riders in the world, most riding bigger, faster machines. After fourteen days of African desert racing in the Paris-Granada rally (previously the Paris Dakar)
J. Brucy's EXP-2 finished 5th overall and first in the under-500cc class. In the punishing week-long Nevada rally, Bruce Ogilvie finished 8th overall, and in the Baja 1000 Honda's riding team of Chuck Miller, Paul Ostbo and Greg Bringle finished 7th overall and first in class. "
We packed up our riding gear and met Honda at a secret location in the Mojave desert to test the EXP-2." After the EXP-2 proved it could stand up to this kind of destructive treatment, Honda let Motorcycle Online ride it.
. Some differences are obvious, like the the main frame, hand-built from aluminum tube and sheet. Other parts are more familiar.
The rear sub-frame is sourced from a CR500, as are the seat and fender. The swing-arm is the same size as a CR500 item and is suspended by a Showa shock.
The forks are conventional (right-side up) Showa items. A small fairing bolts to a bracket attached to the frame headstock, and can be replaced with a set of headlights for night riding.
Flip the ignition switch hidden in the radiator shroud and the powervalve motor whines as it cycles the valve to the starting position and the fuel pump charges the fuel injection system.
The bike kicks over easily for a 400cc single and fires right up. The motor has a mildly-tuned low-end, and top-end similar to an open-class MX bike. In between there's no sudden hit to the powerband, just more power when the rider twists the throttle. The desert gearing is tall, but the friendly powerband makes the bike controllable and fun to ride. That makes life easier for rally riders doing 8 or 10-hour stints in the saddle. We followed Bruce Ogilvie around the desert for a while. Bruce, a former Baja 1000 winner and really fast guy was polite enough to wait at each intersection for us to catch up. 'For an experimental bike, it's very well behaved.

The EXP engine has an effective counterbalancer, so the rider doesn't feel any more vibration than a 125 would produce.' The EXP's suspension has a fairly stiff initial travel, necessary for a desert bike to keep the bike riding high on its suspension so there's room to absorb hard hits. At the speed we were riding we couldn't bottom the suspension. The bike is pretty stable but turns well for a 280-pound desert bike.
The broad powerband helps by making it easy to get the rear end to slide just the right amount to carve the turn. For an experimental bike, it's very well behaved. The EXP engine has an effective counterbalancer, so the rider doesn't feel any more vibration than a 125 would produce. This is important for rally riding- reducing the rider's fatigue lets him ride faster for longer. The 6-gallon fuel tank is narrow at the back compared to the Paris-Granada version's huge tank so the rider can move forward to weight the front end. We tried to get the bike to detonate unintentionally by lugging it in a sand wash, but it didn't misbehave in any way. Other than the odd engine noise it's easy to forget that the bike is fuel injected and makes less pollution than a weed-wacker. After a morning of riding there wasn't any more residue in the tailpipe than a four-stroke would produce.

Even the inside of the silencer stayed clean, an impressive vindication of the low emission design. Honda plan to campaign the EXP-2 again next year.
The company says it has no plans to make a production engine right away, but from the success so far, we'd predict that the world's cleanest two stroke motorcycle will be in production before the year 2000. In addition to direct fuel injection, there are other technologies that can help. Two decades ago, Honda introduced a 250cc, two-stroke motorcycle engine for a Japanese-market-only dual-purpose bike that utilized “Activated Radical Combustion.”
This is a technology that has since been well-studied by the automotive industry and is more commonly known as HCCI (Homogenous Charge Compression Ignition), a combustion process that requires no spark but uses gasoline rather than diesel fuel. In Honda’s 250, HCCI combustion was maintained from about eight to 50 percent load, with conventional spark ignition used at both the high and low end of the engine load range.

The benefit was far more stable combustion (no six- or eight-cycling) when HCCI was operating, lower emissions and—according to those who rode it—a two-stroke that felt as if it had the smooth power of a four-stroke.
Honda’s patents have since expired. For those who dont know, the CRM250AR was the production version of the EXP-2 Enduro prototype that used Active Radical Combustions to decrease emissions. The bike at low revs and low throttle openings closes and exhaust flap (hondas fancy word por PV) and introduces hot exhaust gases back into the cylinder to become thousands of tiny spark plugs (known as Active Radicals). Therefore, the Spark ignition is no longer required, the engine 'diesels' as it undergoes controlled detonation combustion. When Undergoing AR combustion the engine purrs steadily without the expecting 'ring-ding-ding' unsteady combustion cycles common in two strokes. its almost akin to a four stroke. Crank the throttle open and the engine comes to live with potency close to a CR250 Honda.

[Flettner]

Yes, but, wouldn't you want better control than that?
Honda clearly didn't pursue this, why?

[husaberg]

Yes, but, wouldn't you want better control than that?
Honda clearly didn't pursue this, why?

i posted the text out of the attachment. have a read through
there is a better write up over about 6 pages in a US mag of the time that has a lot of details from the peple that did it when i dig it out i will post it.
they basically said it didnt need fuel injection either it was just easier to set up.
the dude said they could control it with the exhaust vale more accurately than the Plug, but they only needed to do this under 60%
plus as the exhaust valve controlled the port it needed to be open up top revs........


They did pursue the tecnology and they did patent it, they made a road bike version the CRM250ARC, just like with the 8 valve NR750.
but they are in the business to sell what people want and that was the CRF's plus it suited the corporate image to only sell 4 strokes.

[WilDun]

All very interesting! - but I was going to say why did Honda let the patent lapse? but that was answered by someone - Husa? - it didn't suit their sales strategy at the time, also it was at a time when they were trying to promote change to the four stroke instead!

Still seems strange that they let it lapse - It would indicate that they were not worried about it being used by others as the four stroke had gained enough ground to keep it ahead and no one was willing to take a chance on it and lose their reputation, when they were already doing OK!!

Last century was when breakthroughs were in full swing, this century - refinements and electronic enhancement instead!

But as Frits would say - K.I.S.S!

[Frits Overmars]

Last century was when breakthroughs were in full swing, this century - refinements and electronic enhancement instead!
But as Frits would say - K.I.S.S!

That's a safe bet Will; I will always say KISS. But that was not my first reaction when reading your post. It was this:

I wonder how that man got his job. Must have been something political.
Not only is the 21st century bringing us more breakthroughs - they are coming at an ever-increasing pace.
Makes me wonder what the world is coming to. It also makes me wish to keep on living for another full century, so I can see for myself .

[Norman]

All very interesting! - but I was going to say why did Honda let the patent lapse? but that was answered by someone - Husa? - it didn't suit their sales strategy at the time, also it was at a time when they were trying to promote change to the four stroke instead!

Still seems strange that they let it lapse - It would indicate that they were not worried about it being used by others as the four stroke had gained enough ground to keep it ahead and no one was willing to take a chance on it and lose their reputation, when they were already doing OK!!

Last century was when breakthroughs were in full swing, this century - refinements and electronic enhancement instead!

But as Frits would say - K.I.S.S!

When you have some time over this long article, even though it goes ten years back, is quite interesting and it also gives some insight info and thoughts about Honda and two strokes and the CRM250.
https://www.dirtbikeplanet.com/future-of-two-strokes/

[WilDun]

Frits,
I need to stress that I am not a 'bible banger' but ..... we need to check out all ancient wisdom wherever it come from!
Here is a quote (this time from the bible and unfortunately for you, in 16th century English!) - this one has always intrigued me! :-

9 The thing that hath been, it is that which shall be; and that which is done is that which shall be done: and there is no new thing under the sun.

10 Is there any thing whereof it may be said, See, this is new? it hath been already of old time, which was before us.

11 There is no remembrance of former things; neither shall there be any remembrance of things that are to come with those that shall come after.

So, a 'breakthrough' it would seem is Dis - Covering , as opposed to inventing!

Definitely words of wisdom from someone way way in the past - way before the sixteenth century, - even way before the days of the bible! - but it also applies to us on our little 'put put' machines as well! ...... the Suzuki lubrication system comes to mind here of course, - but there is a huge pool of great ideas buried under glitzy dumbass (but popular) ideas! - So these can be rummaged through, picked out one by one, modified, reassembled in various ways and called 'inventions'

When you have some time over this long article, even though it goes ten years back, is quite interesting and it also gives some insight info and thoughts about Honda and two strokes and the CRM250.
https://www.dirtbikeplanet.com/future-of-two-strokes/

Thanks Norman, will do that - I had hoped for renewed interest in the two stroke and hopefully we are all beginning to wake up and go back over what has already been tried but just shelved till there is an opportunity to use it!
I don't necessarily know or understand much really, but I do know that some things have to be brought up and reviewed - and all possibilities discussed - as Flettner said, seemingly silly experiments can bring up surprising results!

[ceci]

When you have some time over this long article, even though it goes ten years back, is quite interesting and it also gives some insight info and thoughts about Honda and two strokes and the CRM250.
https://www.dirtbikeplanet.com/future-of-two-strokes/

Sorry but I'm going to spoil it.
This long article is the work of a Master of 2S who believed that there can be a 2S solution without the need for electronics
After analyzing all the existing solutions, which solution the author article himself: dispense with electronics

[WilDun]

Sorry but I'm going to spoil it.
This long article is the work of a Master of 2S who believed that there can be a 2S solution without the need for electronics
After analyzing all the existing solutions, which solution the author article himself: dispense with electronics

I'm sure that is possible - but here is an analogy :-
If you have a wife, go and tell her that she doesn't need a cellphone, a vacuum cleaner, a washing machine or drier and she can't have a car to go and indulge in a shopping spree! - Sure, it will work and she will still be able to survive without these things, but if she is pretty and talented, then she may want to do some more shopping elswhere!

Moral of the story don't cut off the frills entirely - although sensible, you'll lose your 'not so clever' buying public!

[Flettner]

Electronics are not the enemy, although mechanicly we can do better than the loop scavenge twostroke, in my opinion.
Combined, we may have something worthwhile.