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September 28th, 2016, 05:26 AM   #31
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September 29th, 2016, 04:00 AM   #32
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Shit doc, that's way too factual/deep.
Actually Clichť it's not - it's way too myopic as the good Dr. know's full well - he can do much better than that.

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When the #1 State of the Art engine - with 54 hp from a 125cc cylinder - had to go through the effort and complexity of sticking the rotary valve on the back on the engine to gain a couple of hp (due to improved intake run into a crank spinning in the same direction as the intake charge) I question how much further they could've gone.
This solution wouldn't fit on a V4....
Power is increased by improving torque or increasing revs.
On the torque side: aforementioned engine made circa 16.5bar BMEP (30odd N.m at 12k)....that's gonna be hard to get a big increase on. A bit more CFD analysis might yield some gains,...wasn't used in that engine's developement
On the revs side: the whole circumference of the cylinder is chock full of ports. There's very little scope to increase time.area. No miracle revs
So where are the increases going to come from?
The main headscratchers before the 2Ts died was part-throttle issues. Deto.
'Power is increased by improving torque or increasing revs'

Why fixate on the limitations of a particular block? That would be akin to thinking in terms of the restrictive function of a cylinder head as opposed to the range of possibilities of optimal scavenging. I don’t understand why you are using such a rigid example of hardware? - a configuration/solution that has nothing whatsoever to do with the future evolution of the V4 500 two stroke. As Stan Stephen’s used to say, ‘think out of the crate for Christ’s sake’. Now instead, BJ.C some genuine insight from the real two stroke gurus that expressed this belief in the continuing potential of the 500s. These true authorities on alternative scavenging methods, in particular their ideas on friction reduction, non-isentropic stimulation, transfer port timings in relation to pulse waves offer fascinating insight. Your man the late Warren Willing was one of them. These guys weren’t simply dab hands with a needle and a jet, Moriwaki was an authority on gas dynamics, fluid mechanics,thermodynamics and combustion and how to harness related developmental strategies so as to provide the required performance characteristics of power or torque or fuel consumption.

As you know ‘No’, the target is not simply raising torque and BHP but with a two stroke how you make and introduce the power across the range – perhaps eliminating those fabled wafer thin power bands. Part throttle issues, indeed – to me heat was another main adversary of two-stroke engines. Stretching the compression ratio to give say a 10% power increase would possibly only yield a 3% return at the most - the rest will be squandered energy and pumping losses. This is why, at lower engine speeds when the cylinder is not be completely filled with fuel/air mixture the power may increase by 5-6% because there is not so much of this heat loss. As I understood it, this is actually the rationale for raising the compression ratio, not to increase maximum power but to pick up mid-range power and therefore possibly widen the power band. Example being, a variable exhaust port that changes height to suit the rpm the motor is operating at, offers increased drive out of corners – think Roberts' TZ500 and the YPVS system that subsequently appeared on the road. Point being, and the point that Bartol was making, historically seemingly insurmountable barriers to development have been surmounted by innovation – and in a prototype series there was huge continuing potential for a racing two stroke 500cc formula. That will to develop disappeared along with the market for two strokes. Interestingly though there is significant impetus throughout global R&D to develop cleaner two stroke technology.

In spite of its shortcomings, the two-stroke never died remember. Instead, improved designs, electronic fuel injection and automatic oil-metering systems kept it practical for chainsaws, outboard motors and snowmobiles. Skidoo pride themselves on their 2-stroke snow mobile specifications and marketing bumf features direct injection, low oil consumption lightweight internals – (I guess having no valves is what they are referring to in the main), 200 Horsepower Per litre, economy, simplicity of less moving parts etc etc. A snow mobile is not a 500cc prototype racing motorcycle – granted, but consumption in particular is significant and I detect, with the technology of conventional four-stroke engines quite mature, there is renewed interest in taming the two-stroke to compete with diesels, hybrids and electrics as part of the solution to meeting future mileage standards. If that then gathers momentum in the marketplace through cleaner more efficient power plants, then the desire to populate a grid full of strokers will return – albeit minus the blue smoke.

I know that GM are working on a opposed-piston, opposed-cylinder project and an electrically assisted turbocharger. Such a concept is admittedly synonymous military, aircraft, marine and industrial engines – all bulky and heavy, but a similar design was employed for the Beetle which was renowned for its compact size and such an engine would have twice the power density. I realise that this is a departure from racing 500cc motorcycles, but I’m attempting to at least encourage you to think laterally and realise that there are so many possibilities in the commercial continuation of two stroke technologies and where these exist race departments of large corporations such as Honda will flex their muscles and start throwing their weight around in the MSMA to institute change.

Interestingly, you mention Computational Fluid Dynamics which in theory resolves the three-dimensional flow behavior inside engine cylinders. Interestingly if we use that unsteady gas-dynamic calculation to control the flow at the entry and exit boundaries of the system then is no logical reason why this same theoretical approach should not be employed for the design of the most complex of tuned 2 stroke exhaust systems – in particular relation to the pressures at the exhaust port in part governing the charging efficiencies over one cycle. Continual development of race exhaust designs can recover a significant percentage of charging inefficiency in addition to raising post transmission bmep levels. In addition to this, and still on the subject of exhaust - I’m sure that you are aware of resonance. The is an exhaust pulse prior to the appearance of the actual blowdown pulse at the release point is the second return of the plugging pulse from the previous cycle which bounces off the rapidly closing exhaust port acting as an increasingly closed end. This precursor to blowdown is a large pulse but it too is echoes off the closed ended exhaust pipe at the port in a superposition manner so it effectively strengthens and broadens the ensuing exhaust pulse through its latency. I remember Hamish Jameison talking about the nascent research into this (albeit in the late 90s) and explaining the effective harnessing of this second-order phenomenon is essential and is yet another vital factor in the design of high specific output engines and the associated power gains to be made. Further, I think you’ll agree, long exhaust port periods – trapping and charging – optimal breathing through exhaust tuning is particularly beneficial to high speed racing two stroke engines.

Discharge coefficiants aside, why dismiss the value of CFD? as a cognate discipline also offers substantial insight into squish velocity and squished kinetic energy values, burning rates and constant volume combustion and how to tailor these effects to the best possible advantage for any particular two-stroke engine. It also greatly assists the designer in comprehending the effect on performance characteristics which are due to alterations of the physical geometry of the engine and its ducting or its scavenging.
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September 29th, 2016, 06:05 AM   #33
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Yes ketchup, it is compared to the trivia and guessing above. Especially when i consider that complacency to belittle other posters at every turn isn't substantial to him making his points.

You'd need variable anything periphery to not sacrifice a substantial amount of topend if you want another 10hp @9000rpm. Variable ports can't be that much lighter than a flywheel/cam.
The 10 to 3% guess is totally beyond me.
The whole rant about how 2 strokes are very much exhaust dependant is quite a revelation. If only there were decades of optimization behind it... no smoke and noise = no power. Simples. Try to make a kart or saw engine quieter and less smokey and see whether you can actually cut a chunk of butter.
Raising compression would just result in more NOx which is already quite a worrisome thought in relation to todays ultra lean/high comp engines.
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September 29th, 2016, 06:12 AM   #34
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Especially when i consider that complacency to belittle other posters at every turn isn't substantial to him making his points.
You are a sensitive soul. Is it other posters in general, or just you in particular?
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September 29th, 2016, 06:34 AM   #35
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Hey mike
Generally speaking.maybe I'm doing the same simply to illustrate the point. Guess ...I'm just saying
Hey mikey, i do appreciate you finding my pheromones oh so irresistible that u keep going after me but im afraid I'm not that into you you should chase gilf , not bilf bro
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September 29th, 2016, 06:38 AM   #36
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Jesus, Arrabb.
That was pathetic. How long did you spend putting that together? I'm flattered. I think.

If you are comparing your gobbledegook to an actual analysis...well, I can't help you.
If you are interested in discussing 2T development, I'm all for it. Otherwise, I can just dismiss your opinions/thoughts on the matter. Up to you.
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September 29th, 2016, 06:58 AM   #37
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Originally Posted by propagandhi View Post
Yes ketchup, it is compared to the trivia and guessing above. Especially when i consider that complacency to belittle other posters at every turn isn't substantial to him making his points.

You'd need variable anything periphery to not sacrifice a substantial amount of topend if you want another 10hp @9000rpm. Variable ports can't be that much lighter than a flywheel/cam.
The 10 to 3% guess is totally beyond me.
The whole rant about how 2 strokes are very much exhaust dependant is quite a revelation. If only there were decades of optimization behind it... no smoke and noise = no power. Simples. Try to make a kart or saw engine quieter and less smokey and see whether you can actually cut a chunk of butter.
Raising compression would just result in more NOx which is already quite a worrisome thought in relation to todays ultra lean/high comp engines.
I didn't suggest that raising compression was a panacea, I raised it because it is often wrongly attributed to power increase as opposed to usability for want of a better word and as a historical example of a measure to increase race performance.

In respect of NOx emissions, this debate is very much informing the initiative behind cleaner and more efficient two stroke power plants and is pivotal to the research I referred to. Though by no means an authority on this as far as I know NOx formation requires three things: Nitrogen, Oxygen, and sufficiently high temperatures. NOx emissions will therefore increase with higher combustion temperatures and lean mixture operation, which is when enough unreacted oxygen is present in the exhaust. Of course in racing Ė a near stoichiometric combustion point would require a rich burn engine.

Iím sorry if you construe a discussion about exhaust systems a Ďrantí Ė that wasnít may intent. Itís an area that greatly interests me in the context of a tuned two stroke motorcycle engine and as Iím sure the Doc will concur there is historically quite a pedigree in the UK in particular around this area both on the track and on the road.

'Try to make a kart or saw engine quieter and less smokey and see whether you can actually cut a chunk of butter.'

But this is precisely what is currently being achieved by people far cleverer than you or I. It's a shame that they don't tend to populate racing forums.
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September 29th, 2016, 07:09 AM   #38
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Hey mike
Generally speaking.maybe I'm doing the same simply to illustrate the point. Guess ...I'm just saying
Hey mikey, i do appreciate you finding my pheromones oh so irresistible that u keep going after me but im afraid I'm not that into you you should chase gilf , not bilf bro
You are doubtless a more advanced human than I am, but unreconstructed at my current age I am not capable of detecting pheromones via the internet. Being somewhat familiar with excessive self regard myself, I can usually detect that even by means of the internet however.

I guess mercy is the explanation for your forbearance from posting on a forum where the mostly grizzled bikers involved in the forum apparently live in fear of your wit and intellect.
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September 29th, 2016, 07:55 AM   #39
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Jesus, Arrabb.
That was pathetic. How long did you spend putting that together? I'm flattered. I think.

If you are comparing your gobbledegook to an actual analysis...well, I can't help you.
If you are interested in discussing 2T development, I'm all for it. Otherwise, I can just dismiss your opinions/thoughts on the matter. Up to you.
Thanks for your prompt reply Doc.

Definitely, 2T development is fascinating and Iím always eager to learn more Ė particularly from those that are more knowledgeable about the subject Ė or profess to be authoritative on the subject.

Iím genuinely sorry if you dismiss my post as pathetic and gobbledegook Ė Iíd be fascinated to know which aspects of it you actually dispute or are eager to dismiss as inaccurate or waffle. Iím not sure that I can ever recall any of your posts being Ďpatheticí Ė so Iím sure that there is some edification to be gained here through some constructive feedback.

An actual analysis of what? Is that what you contend that you offered in your own rather limited post? I suppose I could B.JC some figures but that would be disingenuous and irrelevant. I thought you raised a very interesting point earlier regarding that we donít really know what might have been possible had the factories continued to invest time and money into racing 2T motorcycles, which was my original point. Development of Two Stroke technologies has endured which is something Iím very interested in keeping abreast of. Moreover, you are perfectly welcome to lampoon my opinions and thoughts, I really donít object to that, but I have also tried to echoe or convey as far as I can recall, the insight of those whose knowledge and expertise I respect Ė albeit crudely, but the all those avenues of development and solutions have been well documented and discussed.

Yeah Iíd love to discuss this further with you because as I say, Iím sure I could learn something and you can then methodically point out the errors in my post instead of sanctimoniously dismissing my interest in this. Further, to avoid clogging up this board, do you have a Skype address you can PM me? - because Iíd be able to clarify my points far easier and logically in real time and Iíd be very interested to hear your views to the contrary and perhaps learn from your Ďactual analysisí.
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September 29th, 2016, 02:35 PM   #40
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Thanks for your prompt reply Doc.

Definitely, 2T development is fascinating and Iím always eager to learn more Ė particularly from those that are more knowledgeable about the subject Ė or profess to be authoritative on the subject.

Iím genuinely sorry if you dismiss my post as pathetic and gobbledegook Ė Iíd be fascinated to know which aspects of it you actually dispute or are eager to dismiss as inaccurate or waffle. Iím not sure that I can ever recall any of your posts being Ďpatheticí Ė so Iím sure that there is some edification to be gained here through some constructive feedback.

An actual analysis of what? Is that what you contend that you offered in your own rather limited post? I suppose I could B.JC some figures but that would be disingenuous and irrelevant. I thought you raised a very interesting point earlier regarding that we donít really know what might have been possible had the factories continued to invest time and money into racing 2T motorcycles, which was my original point. Development of Two Stroke technologies has endured which is something Iím very interested in keeping abreast of. Moreover, you are perfectly welcome to lampoon my opinions and thoughts, I really donít object to that, but I have also tried to echoe or convey as far as I can recall, the insight of those whose knowledge and expertise I respect Ė albeit crudely, but the all those avenues of development and solutions have been well documented and discussed.

Yeah Iíd love to discuss this further with you because as I say, Iím sure I could learn something and you can then methodically point out the errors in my post instead of sanctimoniously dismissing my interest in this. Further, to avoid clogging up this board, do you have a Skype address you can PM me? - because Iíd be able to clarify my points far easier and logically in real time and Iíd be very interested to hear your views to the contrary and perhaps learn from your Ďactual analysisí.
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.
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