Red Bull KTM Ajo
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Joined Sep 2016
894 Posts | 557+
Queensland Australia
I think whether or not the 2T's have potential for improvement or efficiency benefits or not won't really factor into it Electric driven vehicles are the future, love it or hate it. Its already happening in consumer vehicles and in F1 with recovery systems and will at some point in the future be introduced into motorcycle racing.
I myself love the sound of a snarling, popping fire breathing combustion engine and will really miss it.
I myself love the sound of a snarling, popping fire breathing combustion engine and will really miss it.
Joined Jun 2007
10K Posts | 1K+
Norah Head
You know if you really miss that 2 stroke smell you can always add a few cc of castor oil to a tank in your 4T.
As much as I was one of the last people to convert over to 4T bikes ..... especially off road, in this fuel efficient era they cannot compete.
2Ts need to be overfed with mixture to produce high power .... so a high power 2T will allways waste fuel and polute with unburnt gases.
Overfeeding means you are still getting combustion as the exhaust port is already open. In a DI 2T you put only enough fuel in to be completely burnt pretty much before the exhaust port opens. So you get say 1/3rd of the down stroke of the piston doing the forcing down of the piston, thats like max. 1/6 of a whole rev.
Its that area that lays between exhaust port open and bottom of stroke you have too play with for real power unfortunately its the environment that suffers.
And realistcally I was being optimistic cos I havent even taken into account the transfer ports.
Face it ..... 2Ts where the playthings of us in the opulent era ...... thats gone now ...... as have 2Ts.
As much as I was one of the last people to convert over to 4T bikes ..... especially off road, in this fuel efficient era they cannot compete.
2Ts need to be overfed with mixture to produce high power .... so a high power 2T will allways waste fuel and polute with unburnt gases.
Overfeeding means you are still getting combustion as the exhaust port is already open. In a DI 2T you put only enough fuel in to be completely burnt pretty much before the exhaust port opens. So you get say 1/3rd of the down stroke of the piston doing the forcing down of the piston, thats like max. 1/6 of a whole rev.
Its that area that lays between exhaust port open and bottom of stroke you have too play with for real power unfortunately its the environment that suffers.
And realistcally I was being optimistic cos I havent even taken into account the transfer ports.
Face it ..... 2Ts where the playthings of us in the opulent era ...... thats gone now ...... as have 2Ts.
Joined Oct 2012
3K Posts | 725+
Crab Key
That injection system was run on the SR50 DiTech. Very strange little scooter to ride, no 4-stroking/misfiring at idle.
The air pump was mechanically driven to pressurise the little air chamber above the head, which would cost some power. Plus as you wrote the point of the system was fuel consumption and emission reductions. The system doesn't have any power advantages that I can see.
Lastly, injecting compressed air into the head...I reckon you might be able to protest that as Forced Induction
Joined Oct 2012
3K Posts | 725+
Crab Key
Cylinder pressure is already down to a fraction of peak by the time the crank hits 90deg...on any engine. Ok, maybe not Nitro burners...
Losing intake charge out the exhaust duct isn't a problem, the limited rpm range that the pipe can shove it back into the cylinder is the problem. Nothing VSGs can't fix.
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Joined Jun 2007
10K Posts | 1K+
Norah Head
Joined Jun 2007
10K Posts | 1K+
Norah Head
Someone, in the days of yore, played with tuneable header lengths ( on the expansion cone) like a trombone arrangement and it all came to naught.
Face it, even on pipe a 2T piston port engine is inefficient.
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Joined Apr 2008
7K Posts | 3K+
Out of Nowhere
'No',
I didn't say that your 'actual analysis' was wrong and I certainly wouldn't suggest that it was 'pathetic' or 'gobbledegook'. Rather, that it was somewhat limited in its scope - particularly since you have proven knowledge in this area that I would be very pleased to draw upon in and invite discussion. Perhaps you could reciprocate by pointing out which parts in particular of my post were 'gobbledegook'. Also, what are your thoughts about this?...
No Skype then? - Zut alors! - that's a damn shame. I'm sure you could put aside a meagre half an hour of your time to discuss some of the ideas that you are so dismissive of. I do apologise, I wrote that post at work and it's difficult to compose and articulate your thoughts in an open plan office when the purpose of your employment is hardly to spend your time composing a rambling discourse off the top of your head on possibilities for 500cc two stroke engine development. If it was disjointed and seemingly illogical in nature, then that is why. It is also why I propose talking to you in real time, not only because it would enable me to redress this - I think that post may have given you the wrong impression. I have a healthy - or perhaps more accurately, unhealthy interest in two stroke exhaust and intake tuning. I'd like to know specifically what you deemed to be 'gobbledegook'. But also, because I'd be genuinely interested in your feedback.
I also would love to elicit the views of two members that are demonstrably knowledgeable about two stroke motors and tuning - Yamfan and Yakamoto San. I am employed at a West Midlands university which has considerable pedigree in engineering drawing upon the surrounding automotive industry. In fact another very knowledgeable member on here who sadly posts irregularly (Yamaka) I'm sure I'm right in saying was working at nearby Jaguar Land Rover, (love to hear from him too). I often saunter in and listen to the lectures or get the thoughts of a colleague who teaches Motorsport Engineering. I have frequently discussed similar points to those I raised in my post and have learnt much from his informative observations.
Northamptonshire, where I used to work, as you'll know as a county alongside Oxfordshire, spawned a cottage industry for motorsport which is one of the reasons Kenny Snr based his workshops there amid an F1 test bed (as I understand it very much oriented around the expertise in chassis development and aerodynamics). I recall visiting a friend at Riders For Health several years ago in the days when Ilmor were also based in Brixworth and he took me over the road into their workshop. I had a long and very interesting conversation with an engineer there about his views on the recently defunct racing two-stroke development and strangely he centred it around the sort of pathetic gobbledegook I was discussing earlier. It's a shame that you weren't there to put him right. However, I concede such appeals to authority, as Mike would be the first to remind us, is a logical fallacy and the province of the anecdotal - where instead you seek the analytical and I very much concur. Let's Skype.
But on to the subject of pipes again. I don't know about you, but I'm guessing from your time in the UK you'll be aware that any self respecting race rep owner in the early 1980s was nobody without the proud appendage of an Allspeed or a Micron 'spannie' adorning his stroker. I'm sure you recall, the aforementioned British pipes were the aftermarket expansion chambers of choice to any credible KH, RD or RG - but in addition to being popular were hugely polarising. You either subscribed to the twofold pressed steel Micron, fabricated in YakamotoSan's neck of the woods, or the Allspeed multipiece cone construction manufactured 'dahn sarf'. I preferred the former, but to this day there are still Allspeed enthusiasts that swear by the brand and the legacy remains through ex racer Pete Gibson who sold on the brand but marketed a similar product under his own name. I remember a mate of mine taking his 350LC to be tuned by Terry Beckett (again up YakamotoSan's way), and they insisted in the shop that it was all moot unless done in tandem with exhaust tuning. When asked why, they schooled me in great detail on the following and I remember it as though it was yesterday. They basically explained that the exhaust tuning of a 2-stroke is designed to preserve the positive pulse going down the pipe and reflect that positive pulse back up the pipe. The fabled Allspeed pipe for example uses an expansion chamber at the end of the pipe which is basically two cones that reverse themselves prior to the end stinger where the spent exhaust is allowed to exit the chamber. That sort of expansion chamber creates a very strong positive wave reflection back up the exhaust pipe, and this positive pulse will reduce the amount of fresh charge escaping out the exhaust port, and when correctly timed, force back into the cylinder any charge that may have escaped before the positive pulse arrives. Ah! - so it wasn't simply flung on for show or because it sounded good? I have since learnt however through an anonymous internet forum that I was gullibly duped all those decades ago and that this is all in fact 'gobbledegook'. I am also now revising my lifelong convictions in respect of Santa Claus. Strange all this, since Warren Willing was very vocal about the need for transient dyno's at Suzuki - solely for exhaust testing since he also reminded us that the exhausts constitute 50% of the power of a two stroke. More 'gobbledegook' perhaps. As I recall he had to rely on his bud...Bud Aksland at Team Roberts. You're doubtless of the same view that Suzuki won the championship in 2000 despite Suzuki..not because of them. Pointedly, most of the advances were due to Willing's expertise in exhaust modification.
I also previously naively believed that on 2-stroke racing engines, we will see an appreciable alteration in power delivered when the exhaust system is tuned for a particular RPM range or purpose and the engine revs into that range. Isn't it called "coming on the pipe"? or was that simply a Freudian slip concerning the orgasmic nature of my old RD? Anyhow, the burst of sound and power that occurs when that happens is tangible.These were the sort of fine adjustments that I remember Burgess bemoaning the loss of with the onset of the four stroke era.
You might find this interesting, you might not. I recall when GP used to visit Welkom that one of the strategies used by teams to mitigate against power reduction from the lower energy yield from each combustion cycle due to the altitude concerned restrictive silencers to create more pressure due to the plugging pulse of the pipe.I mentioned 2 stroke snow mobiles amongst the earlier gobbledegook, which can operate at substantially higher altitudes than Phakisa Freeway - up to 5,000 feet more and similar strategies are employed.
I absolutely concur when you allude to the bad throttle up behaviour of two strokes - at least I think that's what you meant. Most certainly the limited torque control technologies of the late nineties did little to eliminate this problem - merely moderated it. At the end of their reign I also agree that the V4 two stroke 500s had reached such a pitch in refinement that further developments were measured in single figures of horsepower - or more crucially a few extra rpm breadth in torque curve. 'Huge gains' is I concede utter conjecture on my part and you are absolutely right to call me on that - nonetheless the luminaries that I mentioned were all firmly of the opinion that the 2 strokes had continuing potential. Perhaps I should have said 'relative gains', but returning to Willing, I was always fascinated by that his massive applied knowledge in exhaust tuning - as an art and at the time was an area completely overlooked by an entire Factory .
As you opined earlier though, it would be fascinating to have seen the appliance of technology towards the continued evolution of these wonderful machines over the last decade and a half - particularly given the current open source material which is now available to designers. Such potential I would be fascinated to discuss in a civil manner in real time - assuming that is, you have the time. Like I say, you have Skype?
Joined Oct 2012
3K Posts | 725+
Crab Key
I've never played with a piston port bike beyond lifting heads and checking pistons on an old TZ.
The trombone concept has been realised and examples built, but at the convergent end of the pipe.
Joined Oct 2012
3K Posts | 725+
Crab Key
...., Arrabb. That's a lot to absorb. I read this site on my phone. It's difficult to jump back pages to re-read.
Due to your conciliatory tone, I'll refrain from listing the goobledegook beyond: "non- isentropic stimulations", suggesting OP engines for GP (Forced Induction, my man..plus GM doing an OP engine? news to me. Source?) and something about Beetle engines...
I don't need to be taught how to suck eggs on CFD, I just signed a PO for an upgrade of the package we use at work. That said, we don't use it for engine stuff, bit.more esoteric than that
. Further on the subject of CFD and pipes....I did a crappy analysis of an Honda kit pipe (Jolly Moto) on what passed for PC-based CFD in 94. Tail pipe diameter effects. Told me nothing. Garbage in. Garbage out, I guess. But I did design and build a pipe for an NF4. Did most of the fabrication (header down only, ...... NF4 header joints) but left the welding to people who know what they are doing.
So there's that on pipes.
I have never skyped and am not about to start now. And the PRC isn't particularly skype friendly.
As for Cliche's comment. I interpret that as a comment on the fundamental necessity for a spanny on a stroker? My RS barely notched a dyno reading when we ...... about and took the pipe off.
Back to the development potential of GP 2Ts. Duct angles, exhaust cone angles...all specced to 2 decimal places of angle. It's that critical. While I love the old RD LC tuners and the ability to extract power with such a passive system...they are/were merely improving on a compromised design. All the systems on a 2T are interdependent to a ridiculous degree.
Anyhoo. It's beer o'clock and the Golden Week hols.
PM me if you want to work out a way to discuss strokers/engines/VSGs.
Due to your conciliatory tone, I'll refrain from listing the goobledegook beyond: "non- isentropic stimulations", suggesting OP engines for GP (Forced Induction, my man..plus GM doing an OP engine? news to me. Source?) and something about Beetle engines...
I don't need to be taught how to suck eggs on CFD, I just signed a PO for an upgrade of the package we use at work. That said, we don't use it for engine stuff, bit.more esoteric than that
. Further on the subject of CFD and pipes....I did a crappy analysis of an Honda kit pipe (Jolly Moto) on what passed for PC-based CFD in 94. Tail pipe diameter effects. Told me nothing. Garbage in. Garbage out, I guess. But I did design and build a pipe for an NF4. Did most of the fabrication (header down only, ...... NF4 header joints) but left the welding to people who know what they are doing.
So there's that on pipes.
I have never skyped and am not about to start now. And the PRC isn't particularly skype friendly.
As for Cliche's comment. I interpret that as a comment on the fundamental necessity for a spanny on a stroker? My RS barely notched a dyno reading when we ...... about and took the pipe off.
Back to the development potential of GP 2Ts. Duct angles, exhaust cone angles...all specced to 2 decimal places of angle. It's that critical. While I love the old RD LC tuners and the ability to extract power with such a passive system...they are/were merely improving on a compromised design. All the systems on a 2T are interdependent to a ridiculous degree.
Anyhoo. It's beer o'clock and the Golden Week hols.
PM me if you want to work out a way to discuss strokers/engines/VSGs.
Joined Oct 2012
3K Posts | 725+
Crab Key
The future? They are my reality.
I was given a leccy scooter by a friend. What a pile of junk (mainly chassis bits, but hub drive is kinda interesting).That said, very useful for getting about busy downtown.
Joined Sep 2016
894 Posts | 557+
Queensland Australia
I'm sure you've have seen that Pikes Peak video of the Lighting 218, pretty impressive. The car alarm siren they zip tied to it while he did his run was kind of funny.
The only thing I can see really holding them back is battery technology, capacity is getting better but charge time is still on the high side. If/when they develop batteries that had a 5 minute charge time I think a lot more people would be willing to adopt. Many of the cars are probably fine for people who live within 100km from their work place, so long as you don't want to drive interstate.
Do you know of any motorcycle manufacturers who are dabbling with hybrid petrol/electric assisted power plants?
Joined Jun 2007
10K Posts | 1K+
Norah Head
Its the header length that tunes to a certain revs
high revs .... pipes are short ...... the returning wave has to get back to the port fast ....
low revs ....... pipes are long .....
look at an old CR500 pipe vs a 125.
It was done on a test bed with a straight pipe ..... but when it came to attempting to wrap it through a frame it would have been stupid.
So somebody came out with 2T exhaust port valves/gates ..... and that became the norm.
Joined Jun 2007
10K Posts | 1K+
Norah Head
I like the electric bike idea ..... and the idea of having software selectable engine sounds. I tried a simillar android app. That reads the engine revs via an OBDii connector bluetoothed to the phone then into the car audio ....... had my little diesel sounding like an F1 car
Joined Apr 2008
7K Posts | 3K+
Out of Nowhere
Precisely why I suggested Skype – and being on your phone, possibly the reason that I've now noticed you misquoted me as saying “huge gains”. However, the slightest suggestion that exponential increases in power could have been extracted from the 500s is I concede fanciful and well within the realms of my own conjecture. Sustained? – yes, and that was the opinion of Harald Bartol as I originally mentioned.
"Conciliatory tone'..?? - you assume that my original response was pejorative or hostile...acerbic perhaps, but unlike your reply, not intended to belittle or trivialise your knowledge - rather elicit it.
“Non-Isentropic stimulations?” As I say, these guys were more than au-fait with fluid dynamics as a discipline. I know that Honda R&D was modelling the unsteady flow in the engine ducting for the simulation of both two- and four-stroke cycle engines. Such a model applies mass flow continuity at all sections of an engine and its ducting, but was fully non-isentropic in its handling of friction, heat transfer and area changes along any duct.
“Suggesting OP engines for GP” Ha!! Really? Doc, I appreciate that reading long blocks of text on a phone is onerous but if you are going to skim a Jumkie-esque proportioned post then don’t wrongly attribute assertions that I never made in the first place. Read it again - even if it is difficult to jump back on your phone. Perhaps that does not aid comprehension either, which is why you branded my post as 'pathetic'. My point was that large global organisations such as General Motors are working on such two stroke technologies with the view to obtaining increased efficiency and cleaner operation. If these solutions become commercially viable and we do see a widespread return of two stroke power plants across a range of applications then the motorcycle manufacturers may well revive the two stroke as a product which may then witness a resurgence of interest in 2T racing spanning a range of codes. Again, purely my own supposition I grant you that.
"and something about Beetle engines..."
??? The opposed-cylinder layout - paired horizontal cylinders with a crankshaft down the middle - was the key to the VW Beetle engine’s small size and smoothness. Again, not related to a two stroke 500cc racing motorcycle (you are correct to limit the discussion to a V4 configuration), but simply the observation that R&D is often recursive. The shuttle main engines were basically upgraded F1s from the Saturn V and the same brilliant design has informed the propulsion of the new SLS blocks. Actually, on reflection, it may not be GM - but a spin off who are involved in the design and development of an opposed piston opposed cylinder two stroke layout. Yes I'll search for a link.
I'm sure you've forgotten more than I will ever presume to know about CFD but given that your art is so arcane I was mildly surprised that you didn't devote slightly more of your actual analysis to more of a discussion as to the potential of this in two stroke stimulation as opposed to brief lip service.
In spite of this I regularly use it to converse with students across provincial China and was able to speak on a weekly basis with my daughter when five years ago she travelled from Beijing to Hong Kong - and to Brunei and beyond.
Which is much of what I am saying about expansion chambers. However, the suggestion that a reduction of noise and emissions on say a chainsaw will ultimately crucify it's power is fallacious. Agree?
Absolutely agree...which is precisely why it is so engrossing.
And I will, less so VSGs having had quite my fill of that from the sprawling Ducati threads of five years ago.
Joined Jun 2007
10K Posts | 1K+
Norah Head
Joined Apr 2008
7K Posts | 3K+
Out of Nowhere
Joined Sep 2016
894 Posts | 557+
Queensland Australia
Really interesting thread, to say you are passionate about 2 strokes is a gross understatement.
I read a recent article about Roberts where he quoted that exact statement. Something about Suzuki not using the correct type of Dyno (transient dyno or something) to develop a bigger spread of power rather than just focusing on peak HP. His battles with Suzuki to listen to the team guys who had experience with Yamaha rather than to continue to interpret their requests in their own way, sounded like very frustrating times.
Joined Apr 2008
7K Posts | 3K+
Out of Nowhere
Yeah, I grew up on them and around folk that were really passionate - almost obsessive about how to tune them. A circuit near me, Mallory Park, was always conducive to 250 two strokes - deceptively simple, but crucially no point and squirt long straights. The place was always full of grimey petrol heads and the nimbeys in the village of Kirkby Mallory who recently almost succeeded in shutting the place down must have been permanently addled by the smell of Castrol R.
I have a very large bookshelf. However, the Doc knows much more than I do in a hands on sense and is perhaps even more of an aficionado - which is why I was surprised at his somewhat curt pessimistic response to the Harold Bartol viewpoint. Although in fairness, that has much to do with pragmatic realism where my idealism is admittedly slightly more misty eyed and quixotic.
Dr.No also raised a very good point recently that while everyone was blowing (blue) smoke up Burgess's arse as a Two Stroke guru, the late great Warren Willing was shamefully overlooked. It's true, in 2000, Suzuki only had static dyno testing. As I mentioned, Team Roberts along with HRC and Yamaha had been using transient dynos for almost a decade. The main problem with the RGV was the exhaust problem and ignition timing. Top end wasn't bad, but as I discussed earlier, many overlook the fact that the objective of tuning is as much to make usable power as it is to increase it. Using some of the principles I referred to in my previous posts, Willing through the cooperation of Acksland at KR was able to get the bike on a transient dyno to measure resonance and work on the exhaust tuning resulting in a new set of exhausts from Japan meeting his recommended specifications. Not only did this result in a 10mph increase in top speed, but it substantially reduced the mid range deficit. This is why I keep banging on like a stuck record about the science of exhaust tuning. Nonetheless, this still dogged the bike in relation to yamaha in particular. If Junior tried to pick up the bike early and gas it, the thing bogged down. The reversion to 16.5 tyre which royally ...... over Gary McCoy, also inhibited the Suzuki becuae it meant that you could pick up the bike earlier. That's why, when everyone started using the dumbed down version later in the season, Kenny never won another race after Motegi. Kenny Jnr, again hugely underrated was consistent, which made him a very good test rider. He understood the limits of the bike and how to exploit it to it's max.Suzuki had a very small race division, which continued to hamper the four stroke campaign. Roberts Jnr, and Warren Willing won that title together - like I said not because of Suzuki, but in spite of them.
My apologies Doc, took some digging but the company is called EcoMotors and it was the brainchild of an ex GM VW exec. designer. Exciting stuff...well I think so. I'm really interested in the continuing application of two stroke technologies. Perhaps I simply can't let go, accept and move on. When GP went four stroke, evidently the Kubler Ross model stalled at stage 4.
EcoMotors OPOC Two Stroke Engines ? Opposed Piston Opposed Cylinder
