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September 29th, 2016, 02:57 PM   #41
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Arrabb,
Explain where my "actual analysis" is wrong?
What steps would either raise torque or revs in a 500 to provide these "huge gains", because so far you've failed to provide any support to the contention.
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September 29th, 2016, 03:05 PM   #42
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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.
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September 29th, 2016, 05:03 PM   #43
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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.
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September 29th, 2016, 06:52 PM   #44
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Quote:
Originally Posted by michaelm View Post
I won't enter into the technical discussion since I am a technical ignoramus. On general principles I wouldn't have thought 990cc 4-stroke engines proving superior to 500 cc 2-stroke motors necessarily proved the superiority of the actual technology.

I had also understood that the fuel injection technology Ralph Sarich developed with his orbital engine, which proved to be a rather better thing than the actual engine and was adopted widely for marine 2 strokes, improved emissions and efficiency markedly, and a quick BJC confirmed this. Whether this would also have applied to race engines I have no idea.
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
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September 29th, 2016, 07:12 PM   #45
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Originally Posted by BarryMachine View Post
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.
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.

Last edited by Dr No; September 29th, 2016 at 07:15 PM.
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September 29th, 2016, 09:53 PM   #46
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Quote:
Originally Posted by Dr No View Post
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.
VSGs are good for nothing but bugs and spaceships.
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September 29th, 2016, 09:57 PM   #47
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Quote:
Originally Posted by Dr No View Post
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.
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.

Last edited by BarryMachine; September 29th, 2016 at 09:59 PM.
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September 29th, 2016, 11:18 PM   #48
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Quote:
Originally Posted by Dr No View Post
Arrabb,
Explain where my "actual analysis" is wrong?
What steps would either raise torque or revs in a 500 to provide these "huge gains", because so far you've failed to provide any support to the contention.
'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?...

Quote:
Originally Posted by propagandhi View Post
Try to make a kart or saw engine quieter and less smokey and see whether you can actually cut a chunk of butter.
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?
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September 30th, 2016, 01:16 AM   #49
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Quote:
Originally Posted by BarryMachine View Post
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.
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.
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September 30th, 2016, 01:49 AM   #50
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Shit, 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, shitty 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 fucked 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.
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