2 stroke thread (with occasional F1 relevance!)

[Pinger]

The reason BMW etc publish high permitted oil consumption figures is to prevent warranty claims in instances where bore glazing has occurred. Such high consumption is a consequence of engine damage that they do not want to compensate the owner for.
That said, some very high performance 4T engines do consume oil (MB with its McLaren SLR advise that the oil level be checked at every refuel and I've known bikers carry oil for topping up with on every run).
It is something of a travesty though that the 2T is lambasted for its oil consumption and disposal of 4T oil is completely overlooked. (Incidentally, when my smart was consuming oil at 2T levels, no trace of blue smoke was ever emitted. The cat presumably cleaned it up). What proportion of used 4T oil is recycled?
When we get into the absolute environmental impacts of powerplants we must consider the considerable additional energy devoted to the manufacturing of the massively more complex 4T engines. And their heavier transmissions and the resultant increased weight of the final vehicle into which they are installed. All of which impacts on fuel economy irrespective of the fuel efficiency of the actual installed engine.

[Tommy Cookers]

stepped piston (hoping this hasn't been posted before)
http://www.ukintpress-conferences.com/u ... hooper.pdf

[aral]

A number of posts have been removed from this thread. These have been overly abusive and antagonistic.
It is possible to have dialogue without all this childish attitude that "I am right and you know nothing...".

[J.A.W.]

I did look it up and so far 2 strokes consume more oil than equivalent 4 strokes.
I found nothing to say that they are even remotely similar.

This is the truth and it has been known for decades, regardless of your convoluted arguments.

M-f, the sophisticated computer controlled DI systems that current 2T marine engines such Evinrude utilize..
..have not "been around for decades" - I suggest your 'findings' are flawed, since they fail to take into account
the realities of oil 'consumption'..

It is not my "arguments" that are "convoluted", it is again - failure on your part - to grasp "the truth" of what is "known".
Apparently you have not read the cited data linked in the recent posts - that clearly show this..

[J.A.W.]

& in a typically well developed topical dissertation Kevin Cameron shows the mechanical attractions of the basic 2T,
..what they were capable of with simple* tuning, & why they ought to be available (ok, updated) as road vehicles today..

See here: www.cycleworld.com/bsa-bantam-harley-da ... remembered

* Simple in hindsight, but realized by clever thinking/skilled application of real engineering by pioneers, rather than by
"simulation programs" - which were not only not available then, but are based on their successful working principles..

[Pinger]

stepped piston (hoping this hasn't been posted before)
http://www.ukintpress-conferences.com/u ... hooper.pdf

Bernard Hooper has been hawking his motors since the early 1990s.
Strange though, given it and other 2Ts are out there, that BMW for the range extender in its i3 detuned a 60-65hp scooter 4T to 30hp - a massively over-complex and expensive engine for its intended duty. Other than its suitability to under-floor installation, (and perhaps a reluctance to commission a new clean-sheet simpler design) there is to my mind no logic in this.
RE should be 2Ts first route into auto applications but the prejudices are simply enormous. (Eg, witness the statements of 2T 'narrow powerband' in reports of Renault's 2T diesel. As if all 2Ts had utilised expansion chambers).

To counter the arguments against 2T I ask what kind of 4T engines we would have if development had focused only on the cheapest to produce (eg, hand held tools) and full race. Nothing suited to road use I wager.

[J.A.W.]

I have previously linked Hooper's site ( 1st post on page 7) here, but T-C's link is still worthwhile..
The Hooper 'top-hat' 2T designs actually saw metal iteration way back, 40+ years ago - in the dying days of NVT..

Back then Norton could not see its customers being amenable to 2T ( but tried to sell a wankel-style ex-BSA rotary!).

To be fair P, Suzuki did build a big luxo-barge 2T motorcycle back then - the GT 750.. but again, it was a bit 'wurlitzer',
even it did set Honda off on the 'Gold Wing' bandwagon..

Suzuki had racing success with its GT 750-based (liquid cooled 3 cylinder) F 750 variant, but never sold a 'race-rep'
road version, & the same applied to the other 3 cylinder bikes in their range, unlike Kawasaki, who built performance
oriented 2Ts ( until they started selling their big inline 4T four, & detuned the triples - which cruelled their chances)..

[Pinger]

I think I tripped over a stepped piston design by Quincy (I was chasing down the Quincy Looper exhausting on both sides) built onto a Japanese 4T bottom end. The aim was as per NVT.

Suzuki (bless 'em) did persevere with 2T for tourers (with the Wankel departure as a side-show) but 4T from the other three forced its hand I guess.

Riders preferred 4T it is said. How much of that was due to having a bigger, shinier lump of metal to gawp at I wonder.

edit PS.
I think Suzuki even sold (in some markets) a 2T version of its Jimini jeepy thing until relatively recently.

[J.A.W.]

Kawasaki wanted to out-Honda Honda, & did it with the Z1, a 'respectable' ( & profitable ) big 4T.. & they didn't care
about their 2T legacy & still don't ( the triples are sort of like a disreputable hooligan uncle - in their family tree)..

Suzuki alone of the Nippon makers marketed a wankel-type rotary, but it was fairly hopeless, so they did a Z1, too..
Yamaha did have a w/rotary ready to go, but - wisely - got cold feet, & also bottled out of a big capacity 2T road bike..
.. to their shame.. while wasting most of the `70s on big dud 4Ts, ironically enough..

Yamaha still sell off-road 2T motorcycles, but I think their recent attempt to 'recapture the spirit' of the RD/RZ 2Ts..
..by application of a look-alike styling exercise on a 900 triple 4T - is pretty lame..

Ironically again - Yamaha, alone of the big 4 Nippon bike makers ( yes, even Honda did a couple) never marketed a 2T triple..

[Muniix]

& in a typically well developed topical dissertation Kevin Cameron shows the mechanical attractions of the basic 2T,
..what they were capable of with simple* tuning, & why they ought to be available (ok, updated) as road vehicles today..

See here: www.cycleworld.com/bsa-bantam-harley-da ... remembered

* Simple in hindsight, but realized by clever thinking/skilled application of real engineering by pioneers, rather than by
"simulation programs" - which were not only not available then, but are based on their successful working principles..

Simulation doesn't give you the clever design, it only allows you to optimise efficiency or mechanical losses. Small changes, automated it can search for the ideal parameters. That is it.

Everyone uses it in design to verify and reduce time to optimal Implementation.

Or just showing your opinion is contra to the facts

[Muniix]

Manolis: the advantages of the increased dwell at TDC of your engine are an obviously important claim. The most significant challenge for diesel engine manufacturers today appears to be control of NOx and particulates. Do you know of any research that would suggest that the longer mix and burn you anticipate would help, or hinder, or make no difference to the pursuit of lowering these emissions?

On related point, given this slow approach to TDC is there a possibility that the specific point of combustion initiation might vary more than a more conventional design? I assume that the combustion actually starts over a range of pressure/temperature values and in your design these seem likely to occur over a wider range of crank angle. Might this have noise and vibration repercussions?

It might suit RCCI combustion, who really knows without simulation using accurate combustion models what that piston motion about tdc can be advantageous for, given the high inertial mass slower engine speeds are likely it's more efficient operation, slowing the piston velocity further seems counter intuitive. There maybe some CI combustion mode that suits this. RCCI is dual fuel mixing the characteristics of two fuels. Used to achieve better emmisions and power.

Normally one defines these issues first then designs an engine with the features to best meet goals, has all the performance metrics identified at the start so they can be used to verify design. Without you are not verify anything. Is it better? No measure of success.

There are dozens of metrics that need to be defined,
Crankcase pressure, blow-by gasses, temperature. Imep, Bmep, Bmep/Imep ratio, heat loss, thermal monitoring of hot spots and expansion, fatigue.

The list is huge, I have a huge information model schema that holds the Central point of truth for all engine revisions. It's big data on its own.

A measurement protocol is needed to verify each one or your just playing, no one can take it seriously without metrics to assess it by.

Engine control strategies to meet regulations or is it just another dieselgate. One really needs to control liner temperature for emmisions and effective combustion they are the same really
Otherwise it's an exercise in turning a large piece of metal into smaller pieces.

RCCI looks interesting although the practicalities of duel fuel might be a challenge for the average motorist. I'm not sure why you think it would be better suited to a long dwell at TDC, perhaps you could elaborate.

You again assert that the high reciprocating inertia would mean Manolis' design would need to operate at low speed. The first time round he responded with some data and calculated values that refute that assertion. You might do him the courtesy of explaining which of his numbers is wrong or misinterpreted.

You have also asserted, in an earlier post, that the longer dwell would inevitably lead to slow combustion based on an expectation of low turbulence. Have you looked at the combustion chamber design in this engine? It has a very compact combustion space formed in the pistons with very large squish areas driving turbulence.

The Loughborough paper Manolis refers to gives some indication of the theoretical benefits from increasing dwell angle in relation to the Otto cycle. Although at very low speed their initial results support the theory. They certainly don't disprove it.

I carefully explained that one first identifies the goals for an engine, then designs and verifies that it meet the goals. Using simulation and experimental data.
Manolis has done none of this, he has just cherry picking information that he believes may be applicable to characteristics of his engines without any data to back any of it up

These are traits of vendors you want nothing to do with if you are interested in a successful project

[Muniix]

Kawasaki wanted to out-Honda Honda, & did it with the Z1, a 'respectable' ( & profitable ) big 4T.. & they didn't care
about their 2T legacy & still don't ( the triples are sort of like a disreputable hooligan uncle - in their family tree)..

Suzuki alone of the Nippon makers marketed a wankel-type rotary, but it was fairly hopeless, so they did a Z1, too..
Yamaha did have a w/rotary ready to go, but - wisely - got cold feet, & also bottled out of a big capacity 2T road bike..
.. to their shame.. while wasting most of the `70s on big dud 4Ts, ironically enough..

Yamaha still sell off-road 2T motorcycles, but I think their recent attempt to 'recapture the spirit' of the RD/RZ 2Ts..
..by application of a look-alike styling exercise on a 900 triple 4T - is pretty lame..

Ironically again - Yamaha, alone of the big 4 Nippon bike makers ( yes, even Honda did a couple) never marketed a 2T triple..

2T engine advantages are typically in small light weight engines that aren't regulated, with electric tools offering 6+ kW slow start for low impact to operator that market is gone for good. Energy storage worn on the operators waist or backpack with quick change.

[henry]

It might suit RCCI combustion, who really knows without simulation using accurate combustion models what that piston motion about tdc can be advantageous for, given the high inertial mass slower engine speeds are likely it's more efficient operation, slowing the piston velocity further seems counter intuitive. There maybe some CI combustion mode that suits this. RCCI is dual fuel mixing the characteristics of two fuels. Used to achieve better emmisions and power.

Normally one defines these issues first then designs an engine with the features to best meet goals, has all the performance metrics identified at the start so they can be used to verify design. Without you are not verify anything. Is it better? No measure of success.

There are dozens of metrics that need to be defined,
Crankcase pressure, blow-by gasses, temperature. Imep, Bmep, Bmep/Imep ratio, heat loss, thermal monitoring of hot spots and expansion, fatigue.

The list is huge, I have a huge information model schema that holds the Central point of truth for all engine revisions. It's big data on its own.

A measurement protocol is needed to verify each one or your just playing, no one can take it seriously without metrics to assess it by.

Engine control strategies to meet regulations or is it just another dieselgate. One really needs to control liner temperature for emmisions and effective combustion they are the same really
Otherwise it's an exercise in turning a large piece of metal into smaller pieces.

RCCI looks interesting although the practicalities of duel fuel might be a challenge for the average motorist. I'm not sure why you think it would be better suited to a long dwell at TDC, perhaps you could elaborate.

You again assert that the high reciprocating inertia would mean Manolis' design would need to operate at low speed. The first time round he responded with some data and calculated values that refute that assertion. You might do him the courtesy of explaining which of his numbers is wrong or misinterpreted.

You have also asserted, in an earlier post, that the longer dwell would inevitably lead to slow combustion based on an expectation of low turbulence. Have you looked at the combustion chamber design in this engine? It has a very compact combustion space formed in the pistons with very large squish areas driving turbulence.

The Loughborough paper Manolis refers to gives some indication of the theoretical benefits from increasing dwell angle in relation to the Otto cycle. Although at very low speed their initial results support the theory. They certainly don't disprove it.

I carefully explained that one first identifies the goals for an engine, then designs and verifies that it meet the goals. Using simulation and experimental data.
Manolis has done none of this, he has just cherry picking information that he believes may be applicable to characteristics of his engines without any data to back any of it up

These are traits of vendors you want nothing to do with if you are interested in a successful project

I don't want to put words in Manolis' mouth so I won't try to guess the goals for his Patop design. As a concept some of the objectives are both obvious and verifiable by inspection or basic physics. No need for simulation or test data. Balance or piston motion are two of these. Some of his other claims, such as the likelihood that his engine might run faster or more efficiently than a conventional diesel he has provided a reasonable explanation and citation to partially support. He does not claim proof, or at least not in response to me.

In contrast you have again ignored a request to prove your objection to the claim of faster running. I might accuse you of cherry picking but really, without calculations, numbers or citations, I might equally assume you are just making stuff up. So what's the objection? Bearing loads, or cyclic torque variation or some other downside?

[J.A.W.]

& in a typically well developed topical dissertation Kevin Cameron shows the mechanical attractions of the basic 2T,
..what they were capable of with simple* tuning, & why they ought to be available (ok, updated) as road vehicles today..

See here: www.cycleworld.com/bsa-bantam-harley-da ... remembered

* Simple in hindsight, but realized by clever thinking/skilled application of real engineering by pioneers, rather than by
"simulation programs" - which were not only not available then, but are based on their successful working principles..

Simulation doesn't give you the clever design, it only allows you to optimise efficiency or mechanical losses. Small changes, automated it can search for the ideal parameters. That is it.

Everyone uses it in design to verify and reduce time to optimal Implementation.

Or just showing your opinion is contra to the facts

Marc, you do realize - you have contradicted yourself, 1stly you agree with my take on the value of ideas & testing
to establish functional parameters which can then be usefully subsumed into computer generated 'simulation modelling', - then you inexplicably turn 180` & claim you are "just showing" - this view -"is contra (sic) to the facts"..

Well Marc, you are, for sure - showing something, but appreciation of "facts" - clearly aint it..

[J.A.W.]

2T engine advantages are typically in small light weight engines that aren't regulated, with electric tools offering 6+ kW slow start for low impact to operator that market is gone for good. Energy storage worn on the operators waist or backpack with quick change.

Seems you still can't grasp the fundamental basics Marc..

Fact is - the 2T advantage of every piston downstroke being a powerstroke is why they are utilized in the
largest recip' settings, by powering huge cargo vessels efficiently - enabling direct drive - & thus allowing
the propeller & crankshaft to both turn at the most efficacious rates for traversing long oceanic routes..

Nor it seems did you read the cited Kevin Cameron article wherein he duly notes the power density/mass packaging
advantages of the 2T so apparent in current snowmobiles, viz: 4Ts are still too bloody heavy, esp' to drag out when stuck.

& yeah, do post an advert for a professional, hard-use anywhere - chainsaw, which isn't a 2T, as proof of your claims..