2 stroke thread (with occasional F1 relevance!)

[Pinger]

P, the basic convention is to show the TQ/HP cross at the maths constant of 5252 ( where possible, most diesels wont).
But it does not alter the findings, since he is running a machine on a dyno, not a model simulation on a computer,
& his charts show the hp figures comparing curves before & after modification, rather than TQ/HP..

Mainly he shows hp comparisons but there are a couple of plots with torque and hp (the second and fourth ones). Doesn't make sense for the lines to cross at 7k.

Yes, I have tried various pipes, inc 3-into-1, a set-up which works best when the header section is as short as practicable..
..see the Hirth triple for an exemplary unit.. & they sound very 'Ferrari V12' like, but lose out on top-end power..
..compared to well-designed 3-into-3 pipes..

Three into one is more effective than people may realise, but expansions are king - if the space can be found and the narrower operating range is acceptable. Getting short headers on a triple is challenging (and OBs sacrifice any lost charge on an end cylinder in any bank for compactness) but fours permit longer headers - and shorter ex' port timing. Blair reckoned some triples had to run longer ex' duration than required for blowdown just to suit the manifolding.

I may try a balance pipe system on the inlet side..
.. so the marked reverse pulse from the piston shutting the inlet duct, is fed to the next opening inlet cylinder..
..rather than blowing back through the carb & upsetting the mixture/wasting fuel..

The comments re larger carb and standard inlet timing make sense. The kart (Villiers 9E) I had suffered horrendous fuel stand-off off pipe. Letting milder timing create a big vacuum that a bigger carb can then feed makes sense I think. Extreme timing at low rpm just blows it all out. On readmission, it has picked up three times the required fuel!
Faffing about with the Zenoah (admittedly low delivery ratio and conservative timings), it was quite a shock to see just how late before the inlet is opened. No fuel stand off there though.
With your Kawa motor though, isn't it just pumping it back out at lower rpm as opposed to any pulsation effects. (There's no real harsh pressure differential there around TDC to create a pulse. Vacuum pulse on port opening - very different though!)

[Pinger]

P, a couple of things..

1stly, battery tech will have to get way, way, more advanced, in terms of size, power potential, cost &,
recharge time before they can offer a real/practicable alternative to hydrocarbon fuels.

2ndly, emissions legislation/controls are as much a 'political' issue as a health promotion/technical capability matter..

The inherently fundamental 2T advantages of power density/mass/cost have yet to be specifically applied to cars,
at least in a coordinated package, in the current era, but it does not follow that 2T values thusly - do not still apply..

Agree on all points. Much talk of 'better' batteries but they're not here yet.
Much of the talk I suspect is to prop up share price - while they figure out what they will really replace diesel with.
If RE is required, or even as sole generator, with batteries defining the car's packaging and architecture, exploiting 2T compactness will be a boon. Not convinced CITS fit the bill. Tall before the voice coil injector is fitted and destined to have to 'stand up' due to its wet lubrication. Can't see OEMs liking power valves either - even though they are incredibly effective - twice over.

& there are reasons why ( just as for DI) that the "TJI/lean burn concept" actually applies better to 2T, than to 4T..

As an alternative to voice coil injector - absolutely. 2T is fine throttled so lean burn advantages less obvious. Worth the additional pumping losses for lower combustion temps and lower heat loss? The compromises and trade-offs!....

[J.A.W.]

Three into one is more effective than people may realise, but expansions are king - if the space can be found and the narrower operating range is acceptable...

With your Kawa motor though, isn't it just pumping it back out at lower rpm as opposed to any pulsation effects. (There's no real harsh pressure differential there around TDC to create a pulse. Vacuum pulse on port opening - very different though!)

In my experience P, well-designed 3-3 pipes lose nothing to 3-1, ( 'cept that 'Fazza' exhaust note) but still gain up top..

& piston port engines such as the Kawasaki triples are quite sensitive to that reversion pulse..
..proper inlet pipe length, & even flat/solid-backed individual pod air-filters, have a marked impact, from the get go..

[Muniix]

New 2 Stroke engine release;
The CITS

Actually Marc, not quite so "new", I cited this machine here some 30 months ago, its back on P. 23..

Notwithstanding that S.O.P. - hyperbolic-type investment pitch - is it in fact - supported by proof?
If so, do kindly post the video of a running example, say, on a dyno, & preferably - in an actual moving vehicle..
& with an independent appraisal from the tester.

We agree on some things. He has 'innovated' a Flappy valve and reduced crankcase volume. The remarkable thing is he has got it to work in a kind of fashion, hacked Rotax DI heads onto a v-twin bottom end and because it kinda runs thinks he's solved the worlds efficiency problem with claims based on the Rotax numbers zero measurements, just claims.

I tried to explain the MotoInno TS3 to him and the known issues with telescopic forks, like about 5 times he just couldn't understand. Then in discussing his engine using established terminology he had no idea what was being asked. He is using loop scavenging and wants to use the Orbital DI system that is what he wants the $4M investment for. Passing on relevant literature to him he either doesn't understand it or doesn't want to find out actual fact based knowledge.

Why is it increasingly prevelant that people don't want to learn actual knowledge or choose to filter it through their opinions ignoring what doesn't suit.

Every discussion was so painful a complete lack of relevant engine knowledge.
Then repeating back as if they don't understand after explaining something 5 different ways.
Bearing friction, no idea
Piston friction, no idea
Combustion and heat
assuming he understood combustion is hot could almost be a mistake he definitely had no idea about heat loss.

He would then quote something he did in the 60s as reason to backup his belief. Then you would try to explain why it wasn't relevant, is in cylinder turbulence pre dfv Cosworth tumble knowledge and he just wouldn't understand that no matter how you worded it

Not sure if I should report it on Scam watch or ASIC here in Oz, if some one invests because they didn't do due diligence they will be unfortunate.

He is constantly talking of offering a 5% kick back in investment referrals.

[Muniix]

What are typical modern 2T Bmep numbers and last of pre DI?
WITH bsfc and any emissions info DI also.

Would it be above 8? Above 10?


Thanks

[J.A.W.]

What are typical modern 2T Bmep numbers and last of pre DI?
WITH bsfc and any emissions info DI also.

Would it be above 8? Above 10?


Thanks

Ok Marc, here, as a performance 'yardstick'..

According to Frits Overmars, the Aprilia RSA 125cc G.P. machine produced a BMEP of ~17 bar..
( note that the FIM ban on TEL fuel meant reducing comp ratio from ~19.5 to ~15-to-1).

For current 2T snowmobiles, the BMEP figures range from ~10 to ~14 bar..
.. depending on state of tune, from warranty valid - factory standard, to harder hi-po performance tune.

In the link below, noted 2T tuner Olav Aaen discusses developments & notes the advantage of the 3 cylinder lay-out..
..which is yet to be re-introduced in current hi-tech form..
www.amsnow.com/how-to-tech/2009/03/tech ... efficiency

I have previously cited a number of academic research papers in this thread, with comprehensive analyses of emissions..
..such as published by the University of Idaho, & you can read them Marc, if they are of interest.

[Muniix]

I've edited my previous post. May delete it. Relevant info only now hopefully.

Just maybe someone doing hybrid powertrain control strategies, may have put some thought into the best use of;
Ultra lean combustion up to 16 bar Bmep
Multiphase combustion up to 22 bar Bmep
EM Power control +/- 60 nm
To achieve maximum acceleration from available grip force

Really the Torque figures of IC engines are fraud, they only produce this at a very narrow rpm range, unlike electric which is effectively always available.

So, Marc, you are unable to provide evidence of your claims, such as a link to certified dyno charts or even weights.
(& its Bantam, as in diminutive chook, not Batam , or Batman, or other fanciful things).

& still you don't read the data cited here..

Such as your ill-founded assertion: "...IC engines are a fraud..."

If you refer to the basic 30 year old road going 2T Yamaha twin dyno* chart posted a couple of pages back,
-not only was it capable of a peak output of ~165 hp/ltr at a low 9,000 rpm..
.. but it made over 30ft/lb torque for more than 4,000 rpm to that point.

2T engines have advanced significantly since then too, obviously.

*rear wheel power.

You just contradicted your self with the torque range from the impressive 2T Yamaha twin engine dyno chart being;
18-46 proves my statement
That Power and Torque claims of IC engines are only available in a very small operating situation. Supporting my assertion that EM engines claims are more realistic.

I don't see some peoples posts because I see too many erroneous claims which bug me. Due to previous vendors repeated false claims of their products​ performance and behaviour when it failed miserably that ultimately led to a co-worker passing​ from a heart attach. Even though I stepped in the day before and worked around the clock giving the situation for him giving him Xmas holidays with his family. When I rang at 6pm to inform that the $80m project issue was fixed, I had to be told 3 times he was dead. Rip Pat 26-Dec-91
I have an issue with clearly false claims of vendors. Maybe not everyone has coded a bearing friction model. But if you haven't don't go making claims that contradict physics.

In the graph you mention​ I can't see of the twin 2T engine because I choose not to have my intelligence insulted in silly childish comments that contradict the known facts. For example they included;

Making claims of EcoMotors without reading their postmortem is for idiots.

Claiming Revetech are gone when they have just contracted an engineer to do design changes of their engine for a client.

So I feel obligated to correct the misleading information. Force of habit.

I choose to block his posts to save everyone. It is just not worth my time, people with his exact behaviour lead to the death of a work colleague.

That dyno data is now not even relevant and anyway has not been released. But anyone familiar with engines, combustion with any inclination to understanding intake flows can by looking at the Bishop valve geometry and the clearly unique unobstructed flow that may present some advantages to VE gains at the high end due to the behaviour of air being compressible, useful in over rev situations not previously available in induction systems.
Understanding the amount of air it can trap and injected fuel mass at x or y rpm will easily achieve 76 to 80 hp at safe piston velocity if one increased rod length, which they can do due to the Bishop valve heads low profile.

Bishops first attempt with an F1 setup on the CRF450 being very similar bore size 96 vs 93mm had poor performance, they had to reduce valve size heavily and implement a clever throttle valve that closing from the outside in to increase intake velocity and introduce swirl, this setup gave impressive results from low down to over-rev without phasing.

Given the increased heat release of high tumble ratio even at compromised BSR of the CRF450 and the associated reduction of heat losses due to optimal combustion chamber geometry, no heat quenching features typically of poppet valve engines. Really is not that hard for anyone familiar with combustion to believe 80 hp is viable. No magic involved. Just well understood physics.

To continue development of IC engines we need to evaluate every Innovation and its features, finding complementary features in other Innovations through detailed simulation that shows a clear advantage over the traditional design. Due diligence and risk assessment, testing to meet endurance.

Australia had to tear down its Automotive industry, so it could build a new industry based on modern proven methodology. Out with the old biases, opinions etc. Replaced with science and Technology the BS & subsidies they demand to meet regulations due to 'too big to fail' eliminated.

[J.A.W.]

That Power and Torque claims of IC engines are only available in a very small operating situation. Supporting my assertion that EM engines claims are more realistic...


That dyno data is now not even relevant and anyway has not been released. But anyone familiar with engines, combustion with any inclination to understanding intake flows can by looking at the Bishop valve geometry and the clearly unique unobstructed flow that may present some advantages to VE gains at the high end due to the behaviour of air being compressible, useful in over rev situations not previously available in induction systems.
Understanding the amount of air it can trap and injected fuel mass at x or y rpm will easily achieve 76 to 80 hp at safe piston velocity if one increased rod length, which they can do due to the Bishop valve heads low profile.

Bishops first attempt with an F1 setup on the CRF450 being very similar bore size 96 vs 93mm had poor performance, they had to reduce valve size heavily and implement a clever throttle valve that closing from the outside in to increase intake velocity and introduce swirl, this setup gave impressive results from low down to over-rev without phasing.

Given the increased heat release of high tumble ratio even at compromised BSR of the CRF450 and the associated reduction of heat losses due to optimal combustion chamber geometry, no heat quenching features typically of poppet valve engines. Really is not that hard for anyone familiar with combustion to believe 80 hp is viable. No magic involved. Just well understood physics.

To continue development of IC engines we need to evaluate every Innovation and its features, finding complementary features in other Innovations through detailed simulation that shows a clear advantage over the traditional design. Due diligence and risk assessment, testing to meet endurance...

Australia had to tear down its Automotive industry, so it could build a new industry based on modern proven methodology. Out with the old biases, opinions etc. Replaced with science and Technology the BS & subsidies they demand to meet regulations due to 'too big to fail' eliminated...

Oh no.. not even more incoherent blather.. on top of 'bumping' a previous, & just as awful, post too Marc..

You are wrong about IC Engine torque, & notwithstanding that, you do know that gearing schemes have been around..
..for millenia, right?
The improvement in TQ spread in 125cc G.P. race 2Ts over years of development, meant that 6 ratios sufficed,
even with more power, than when, in the early days, a dozen or more gearbox speeds were needed to stay in the 'powerband'..

& your 'belief' in extraordinary 4T power-to-weight figures, especially when they are unsupported by actual data, & are
unable to be approached 'by an order of magnitude' via the original machine.. amounts to 'magical thinking' - for sure..

Australia did not "...have to tear down its automotive industry..." the fact is, Australia tore down its import controls,
& since all the major players ( Ford; G.M.; Toyota) were all wholly foreign owned, & were able to exploit 'globalism',
they chose to can local manufacture operations - when the Australian Gov't ideologically abandoned its stake in 'strategic industries'.. & so, to hell with those jobs, & the paychecks earned by the workers..

[Pinger]

Every discussion was so painful a complete lack of relevant engine knowledge.

I found a CITS launch document from 2013 on my lap-top. In it, there are some dubious claims. He claimed to eliminate piston rock at TDC which he claimed afflicted short skirted pistons - how did he miss that a 2T with exhaust port to the floor requires a piston taller than stroke length? Back then, he was for using E-TEC voice coil injectors.
I couldn't quite see where his claims of being less reliant on exhaust tuning were coming from. Undamped flappy valve smashing home on its seat - reliable? And, despite his claims, not all reeds are placed in V-blocks. Worth noting also that given the requirement for pedestrian impact safety, tall engines are disadvantaged.

[J.A.W.]

Aye, Pinger, if you listen to the - seemingly only available - video soundtrack of the CITS 'running'..
( & if under its own 'steam', at all) .. it sounds very sickly, & quite unlike the lively home-built I posted recently..

Yet to have any hard data/proper dyno charts on the record either, even if Muniix dismisses such proof as "not... relevant."

[Pinger]

Duplicate post deleted.

[J.A.W.]

Three into one is more effective than people may realise, but expansions are king - if the space can be found and the narrower operating range is acceptable. Getting short headers on a triple is challenging...

P, if you scroll down this aftermarket pipe offering list for Polaris to the 'triple' section, the hp gain is salient, 3-3, wise..
www.aaenperformance.com/Polaris.asp

& here: www.totallyamaha.com if you click on 'technical pages' > snowmobile > engines> 'fitting a boost bottle',
therein is shown a 700cc 2T triple boost-bottle set-up, which claims "8-10 hp" gain "at steady throttle" & "3-4 at peak".

This site: www.hartmaninc.com/engine.html offers both the short header 3-1, & 3-3 2T pipes, also showing both..

[manolis]

Hello all.


Regarding the intersection point of the power curve with the torque curve in a dyno:


Suppose the same “scale” is used for both, the Power and the Torque.

For simplicity, take the case the power is in W (watts) and the torque is in Nm (Newton meter).


The Power is calculated from the Torque as :

Power = Torque * 2 * pi * rpm / 60



(why?

A torque of 1Nm can be regarded as a force of 1N acting at 1m eccentricity from the rotation axis of a shaft.

Per rotation of the shaft on which the eccentric force acts, the above eccentric force of the 1N travels, along its direction, at a distance of 1m * 2 * pi (which is the length of the periphery of a circle having 1m radius; pi=3.14159. . .), providing a quantity of energy equal to:

E = 1N * 1m * 2 * pi = 6.28 mN = 6.28 J (Joules)

Per second, the number of rotations of the shaft equals to rpm/60 (rpm: the number of rotations of the shaft per minute).

So, the relation between the Power and the Torque is:

Power = Torque * 2 * pi * rpm / 60 )



Example:

With 100Nm torque at 6,000rpm, the power is 62,832W


With the power in W (watts) and the torque in Nm (Newton meter), the rpm at which the Power and Torque curves intersect is wherein the Power “equals” to the torque, so:

Power “=” Torque = Torque * 2 * pi * rpm / 60

i.e. rpm = 60 / (2 * pi) = 9.55,

i.e. the two curves intersect at 9.55rpm.



In case the Power is in kW, and the Torque is still in Nm, the intersection rpm point shifts1,000 times higher, i.e. at 9,550rpm.


If the Power is in PS (1PS=0.736kW) and the Torque is still in Nm, the intersection point is at: 9,550 * 0.736 = 7,000 rpm (why? the power curve “shifts” upwards by 1.36 (1.36 = 1 / 0.736) and so it intersects the torque curve at 1.36 times lower rpm).


Similarly:


If the Torque is in lb*ft ( 1lb*ft = 1.36Nm ), and the power is still in kW, the intersection point goes at 7,000 rpm (the torque curve “shifts” downwards and intersects the power curve at linearly proportional lower rpm).


If the Torque is in lb*ft ( 1lb*ft = 1.36Nm) and the power is in PS (1PS=0.736kW), the intersection of the two curves is at : 7,000 *0.736 = 5,150rpm (the power curve “shifts” upwards by 1.36 and intersects the toque curve at proportionally lower rpm)


If the Torque is in Nm and the power is in HP (1HP=.746kW), the intersection point goes at 7,120 rpm.


If the power is in HP (1HP=.746kW) and the Torque is in lb*ft the intersection of the two curves is at : 7,000 * 0.746 = 5,200rpm, like:




By the way, in the dyno of the Yamaha RD350:



the intersection point should be at 5,200rpm in both models.
However in the ’85 model the two curves seem intersecting at 5,000rpm (which is not correct).


If the power is in HP (1HP=.746kW) and the torque is in Kgm (1Kgm = 9.81Nm), the intersection of the two curves is at 726rpm. Don’t get confused by the following dyno:



because it uses “different scales” for the power and the torque.



If you search in the Internet, you can find all the combinations of power and torque units in the dyno shown. . .

Babel?

Some day may be agreed the use of the same units worldwide.
Till then . . .


Thanks
Manolis Pattakos

[Pinger]

If the Power is in PS (1PS=0.736kW) and the Torque is still in Nm, the intersection point is at: 9,550 * 0.736 = 7,000 rpm .

Spot on Manolis.
Note to self: read the Y-axis more carefully for units used in future.

[Pinger]

P, if you scroll down this aftermarket pipe offering list for Polaris to the 'triple' section, the hp gain is salient, 3-3, wise..
www.aaenperformance.com/Polaris.asp



This site: www.hartmaninc.com/engine.html offers both the short header 3-1, & 3-3 2T pipes, also showing both..

Short headers in relation to the ex' port timings - quite short in outboards. The next thing I have to look into is the effect of exhaust configuration downstream of the manifold.

& here: www.totallyamaha.com if you click on 'technical pages' > snowmobile > engines> 'fitting a boost bottle',
therein is shown a 700cc 2T triple boost-bottle set-up, which claims "8-10 hp" gain "at steady throttle" & "3-4 at peak".

That is a lot like the balance pipe fitted to 2T twins - eg, RDLC, RG250. For which a boost bottle was sold as an aftermarket option. Reed valve motors though. Can't see why your proposed set-up isn't worth a try.