2 stroke thread (with occasional F1 relevance!)

[J.A.W.]

Hello J.A.W.

Here is the KTM250 TPI of 2018 from your link:

http://motocrossactionmag.com/wp-conten ... studio.jpg


According the DIRTBIKE TEST / Jimmy Lewis ( http://dirtbiketest.com/fresh-dirt/ktm- ... dG5bwpu.97 ) :

KTM says there will be, “considerable benefits over carbureted models including drastically reduced fuel consumption while also no-longer having the need to pre-mix fuel or alter the machines’ jetting.”
Called TPI (Transfer Port Injection) the biggest difference from current off-road four-stroke fuel injection systems is the placement of the injectors in the transfer ports and not in the throttle body or in the air boot (from what we can see).

http://dirtbiketest.com/wp-content/uplo ... -750-W.jpg


Question for all:

With the exhaust port remaining open for several (20? 25?) crankshaft degrees after the end of the transfer (i.e. with all the fuel into the cylinder), what stops a part of the fuel from escaping unburned to the exhaust?

We talk for an engine operating in a wide range of revs and loads.



In comparison, here is a PatATeco 2-stroke design which, either carbureted (the carburetor connects to the left / lower port):

http://www.pattakon.com/PatATeco/PatATe ... uretor.gif

http://www.pattakon.com/PatATeco/PatATeco_s1.gif

or injected:

http://www.pattakon.com/PatATeco/PatATeco_s5.gif

keeps the fuel in the cylinder:

the transfer starts with air from the crankcase, it continues with rich air-fuel mixture from the space underside the piston crown and ends with air coming from the crankcase and passing though the piston and the asymmetric transfer ports.

The rich air-fuel mixture can enter into the cylinder even after the closing of the exhaust.

In the same design the intake is highly asymmetrical without reed valves and without disk or drum valves.

More at http://www.pattakon.com/pattakonPatATeco.htm

Thanks
Manolis Pattakos

Hi Manolis,

You could build it, & if it functions in metal as per design, KTM might have to pay you for it..

I note that a member here 'Uniflow' has been using a very similar ( home built) set-up to the KTM,
although the published Yamaha patents on it ( linked earlier in this thread) may well have elapsed...

The whole 2T/4T 'working volume/swept volume/geometric compression ratio' - palaver is of course, a 'rules fiction',
akin to the 'calculated equivalence' ratios accorded by various competition federations for wankel/turbo mills..

[manolis]

Hello J.A.W.

You write:
“To be fair Manolis, I note that minuscule motor was sans exhaust pipe.. & that's a integral part of real-world 2T function..
This would surely tend to 'colour' the results of the test outcome.. somewhat significantly.. ”


You are right.

However I found no other crankcase P-V plot in the Internet.
If you have some, please post it.

Thanks
Manolis Pattakos

[manolis]

Hello all.


It is not the physics degree of Kevin Cameron that makes the difference; millions of people have physics (and others) degrees and still cannot understand the basics.

Kevin Cameron, standing firmly on the basic physical laws, can think out of the box, can calculate, can predict, can reject and, the most difficult, can dream.


Quote from Kelvin Cameron / CycleWorld magazine, about the unbelievable evolution of the 2-strokes through the years:



“What were their methods? CFD? Time-area analysis? Laser interferometry mapping? No, they did what we all did in those days; they tried stuff.”

Thanks
Manolis Pattakos

[Pinger]

http://www.jhis.co.uk/ICE/Help/images/D21DSPVDiag.png



The pressure in the crankcase of the 2-stroke with the 1.6:1 primary compression drops near 0.5bar, while the pressure in the cylinder of the 4-stroke with the 10:1 compression ratio cannot drop below, say, 0.3bar.

When I look I see the pressure dropping from 15psi to around 11psi (at lowest). 4psi is 0.27 bar.
The other pressure drop (on the downward stroke) is the compressed charge reducing to cylinder pressure when the transfer ports are open.

Close off (throttle) a cylinder that has as clearance volume 1/10th of the swept volume, draw the piston down, and the pressure drop will be much larger.

[/quote]

[Pinger]

However I found no other crankcase P-V plot in the Internet.
If you have some, please post it.

Thanks
Manolis Pattakos

Have a look at Blair's Design and Simulation book - there's plots for all the pressures for various engines - chainsaw, blower scavenged triples and fours, and race tuned twins.

There's also some papers; The Effect of Crankcase Volume and the Inlet System on the Delivery Ratio of Two-Stroke Cycle Engine and A Study of the Delivery Ratio Characteristics of Crankcase-Scavenged Two-Stroke Cycle Engines that may be off interest. (Shout if you can't find them and I'll provide more info).

Question: On the design of yours you showed with the last of the transfer occurring after exhaust port closure. How so with no remaining crankcase pressure and a rising piston? I'm thinking, the flow will reverse back into the crankcase - as happens with conventional porting even.

[Pinger]

Anyone who has access to a 2T motorcycle ( not with CVT ) can test the low 2T 'pumping losses'..
..per the overt characteristic of very little apparent 'engine braking' - as the give-away, but if you kill the ignition..
..then open the the throttle, you will suddenly develop 'engine braking'..

Exactly the same can be experienced on pull starting a small 2T. Open the throttle and it gets a lot harder to pull. Pointing to the work going into pushing through the transfers.

The lack of friction from not driving cams/valve gear/large capacity-high pressure oil pumps-scraper rings & the like too.

Everyone is in such a rush to go to plain bearings and a parasitic pump. Roller bearings as standard are a bonus!

Here, yet another approach to exploiting the 2T fundamentals: https://www.pureburnengines.co.uk/two-s ... pplication

Not sold on that as a concept. Unthrottled we've just discussed. For more cost it gains very little (lower heat loss (maybe) vs higher air work) over downcarbing a conventional 2T to a delivery ratio where the charge loss is minimised.
Petrol vapour heavier than air. Why centrifuge fuel to the combustion chamber wall? Throttling losses shuttling charge between cylinder and combustion chamber and back again. Can anyone see real benefit in the design?

[Muniix]

Maybe a pressure wave supercharger to provide the intake pressure on a two stroke engine, after the first couple of cycles on start would be running well. Make a good research project. Integration into the packaging some novel way. High charge pressure with EGR if needed with TJI and conventional HP direct injection. Two stroke engines are pressure wave engines. There must be a clever meeting of these two systems that is an improvement and simple. A through flow PWS not the Hyprex style with inlet and exhaust at opposite ends.

Also on calling Polaris Swiss Auto about the Hyprex PWS seems Polaris hasn't just shut down Victory, Mission motors they have sold off the IP assets and components. So no more PWS availability from Swiss Auto. That is a shame.
No reply from the German company that has bought it.

Oh no.. by the beard of the Vader..
..well, Marc, it looks like we're actually getting you over to the 'dark side' - too.. "May the 2T power be with you.."

It's an interesting intellectual challenge! What can come out of it can only be good, knowledge, discoveries...

I was always the one that was shangied to solve others problems. It's a curse I was born with, dad got shangied to the Womera to work on the Blue Streak missile project. Interesting things he hasn't divulged due to official secrets act!

[Muniix]

talking of cars I see that a suggested cause of the Ford Orbital 2 stroke failure was inadequate ring life

That sounds familiar - in that I seem to recall it being said at the time.
Re-reading Orbital's paper on the 5million km trial it says no ring problems providing the ports were properly chamfered.
Even if ring wear is deemed excessive - are detachable cylinders not acceptable with a view to treating rings as service items? It would require reasonable access to the engine but sled motors seem to survive well enough without casting the block and upper crankcase in one piece.
It may be that ring wear is too high a price to pay for loop scavenging.

I would have thought that current ring technology would not be an issue anymore.

AP advanced profile, low tension, DLC edge coated ... All the acronymed ring tech of currently available rings would solve any such issue now.

The specification used in F1, MotoGP and Superbikes rings are the same I've noted. Looking at a Total Seal catalogue reveals the common specification for known bore sizes in these classes.
Talking to them also helps I've found. Combining this with the best piston and ring friction and blow by models to come up with a accurate simulation when compared with experimental data. Not much point to simulating if the numbers are BS, wouldn't even know if you were heading in the right direction.

Motorcycles, combustion, electrons and algorithms. Equal best thing in life.

[Muniix]

Hybrid intergration with the ZeroShift on a 7 ratio gearbox is made so much simpler. One can improve its shift performance even further, the emmisions improvement​ is also better.
Aprilia use it in their​ MotoGP bike.

well I tend to say that F1s shift performance is not any better with the K on the scene than it would be otherwise
though a more road engine's shift would be improved
and what are Aprilia using ?

I'd say that F1 gear change performance, time between shifts hit it's minimum years ago - pre F1 hybridisation. (Ferrari and some Israel transmission researchers from memory in Schumachers time)
Though with a more conventional manual one can do things with type 1 hybrid (crank driven) to assist the three stages involved in changing and synchronisation.
There is a resent paper on this I partially read from the engineering 360 emails.

Aprilia have exclusive rights to the ZeroShift in MotoGP one has to agree to never racing their bike in that class, that's ok the FIM has banned my valve gear anyway.

According to ZeroShift Jardines recently Aprilia is using it in their GP bike, obviously with them mentioning they want to use it in production, it's the testing ground for eventual use in production bikes. It has emissions and energy advantages.

[Pinger]

I would have thought that current ring technology would not be an issue anymore.

AP advanced profile, low tension, DLC edge coated ... All the acronymed ring tech of currently available rings would solve any such issue now.

''Outside of the Genesis program, a martensitic cast-iron ring material has also been validated in place of the chrome-ceramic rings as a lower cost option. The castiron rings have demonstrated significantly less bore wear yet still offer very good scuff resistance.''

and:

''Ports in the side of the cylinder performed well after initial concerns were expressed at the effect of the port edges on piston ring wear. After appropriate choice of piston ring shape and ensuring that controls were placed on the finishing of the port chamfers, these concerns did not arise as problems during the fleet trial.''

The above is quoted directly from the 5m km trial paper.
They seem not to have had any problems. Possibly it was a perception of potential wear that scuppered it. Old prejudices prevailing as they do....

[manolis]

Hello Pinger.

You write:

“When I look I see the pressure dropping from 15psi to around 11psi (at lowest). 4psi is 0.27 bar.
The other pressure drop (on the downward stroke) is the compressed charge reducing to cylinder pressure when the transfer ports are open.”


Because the plot is for full load (wide open throttle).

With closed throttle and 1.6:1 primary compression ratio, the pressure drops near 0.5 bar (7.5psi).




You also write:

“Close off (throttle) a cylinder that has as clearance volume 1/10th of the swept volume, draw the piston down, and the pressure drop will be much larger. “


How much larger can be the drop of the pressure?

Zero is the absolute vacuum.

To the residual gas of the 4-stroke with the 10:1 compression ratio (theoretically 1/10 of the cylinder capacity, more than double in practice due to the overlap) it is added a quantity of fresh mixture.

This quantity, in atmospheric pressure, is about 1/5 of the capacity of the cylinder.

Not difficult calculations based on the data provided at http://www.pattakon.com/pattakonIdleValve.htm :

.

for the Honda - VVA-roller prototype engine of pattakon:





Adding the residual gas (circa, 2/10 of the capacity of the cylinder) and the charge required for the engine to idle (circa, another 2/10 of the capacity of the cylinder), the cylinder is not so empty.

With 40% of the capacity of the cylinder occupied, the actual compression (or expansion) ratio is not the geometrical one (10:1) but 2.5:1, or so.




You also write:

“Question: On the design of yours you showed with the last of the transfer occurring after exhaust port closure. How so with no remaining crankcase pressure and a rising piston? I'm thinking, the flow will reverse back into the crankcase - as happens with conventional porting even.”


For low rpm the timing shown in the animation is aggressive.

But for high revving, wherein the inertia of the air gets in play, the timing should be even wilder.


On the other hand, with the asymmetric timing, the duration of the exhaust can be substantially shorter, shifting all the ports lower on the cylinder.


Thanks
Manolis Pattakos

[Pinger]

Because the plot is for full load (wide open throttle).

With closed throttle and 1.6:1 primary compression ratio, the pressure drops near 0.5 bar (7.5psi).

Transmission systems complicate the picture. If as with propeller the rpm drops then the vacuum will also. If as on a road vehicle the rpm remains constant and the torque output is reduced by throttling the vacuum will increase.

How much larger can be the drop of the pressure?

Zero is the absolute vacuum.

A bit like absolute zero temperature to actually achieve? Enormous effort required?

“Question: On the design of yours you showed with the last of the transfer occurring after exhaust port closure. How so with no remaining crankcase pressure and a rising piston? I'm thinking, the flow will reverse back into the crankcase - as happens with conventional porting even.”


For low rpm the timing shown in the animation is aggressive.

But for high revving, wherein the inertia of the air gets in play, the timing should be even wilder.


On the other hand, with the asymmetric timing, the duration of the exhaust can be substantially shorter, shifting all the ports lower on the cylinder.

I suspect your inertia will be in the lower port.
The prospect of lower ex' duration with asymmetric transfer timing is - or could be - welcome. How far back though before high rpm breathing is stifled? (My current conundrum with my asymmetric transfer timing endeavours).

[Muniix]

Hello all.


It is not the physics degree of Kevin Cameron that makes the difference; millions of people have physics (and others) degrees and still cannot understand the basics.

Kevin Cameron, standing firmly on the basic physical laws, can think out of the box, can calculate, can predict, can reject and, the most difficult, can dream.


Quote from Kelvin Cameron / CycleWorld magazine, about the unbelievable evolution of the 2-strokes through the years:

http://www.cycleworld.com/sites/cyclewo ... H&fc=50,50

“What were their methods? CFD? Time-area analysis? Laser interferometry mapping? No, they did what we all did in those days; they tried stuff.”

Thanks
Manolis Pattakos

I come up with great is -- then use compute to verify and optimise. Many of my ideas have been commercialised successfully​. Many not by me including the fastest growing company in the world, only to be destroyed by Microsoft, that could have been me, look what I missed out on. Had near exactly the same as a browser in 1992 subset of SGML and jit language runtime. Uber idea but financial backer didn't go for the Gray legal side of it when Nokia introduced their N9000/9100.

While I've been identifying the optimal average crankcase pressure to minimise piston and cranktrain Aero frictional losses, likely ring blowby increase. You work to maximise the moles contributing to Aero friction in crankcase. And parasitic losses in your balance systems pumped up to 11 compressing air moving masses around.

I'm coding a virtual attribute to contain the energy used in a mesh cell when the energy conservation solution is reached in the higher order functions of CFD.

That way I can optimise cranktrain geometry in the crankcase and energy used by vacuum pump. Achieving the opposite, minimal parasitic losses.
I don't write any code until I've figured out a test for it first.

[Muniix]

Hello Pinger.

You write:

“When I look I see the pressure dropping from 15psi to around 11psi (at lowest). 4psi is 0.27 bar.
The other pressure drop (on the downward stroke) is the compressed charge reducing to cylinder pressure when the transfer ports are op hien.”

Because the plot is for full load (wide open throttle).

With closed throttle and 1.6:1 primary compression ratio, the pressure drops near 0.5 bar (7.5psi).

You also write:

“Close off (throttle) a cylinder that has as clearance volume 1/10th of the swept volume, draw the piston down, and the pressure drop will be much larger. “

How much larger can be the drop of the pressure?

Zero is the absolute vacuum.

To the residual gas of the 4-stroke with the 10:1 compression ratio (theoretically 1/10 of the cylinder capacity, more than double in practice due to the overlap) it is added a quantity of fresh mixture.

This quantity, in atmospheric pressure, is about 1/5 of the capacity of the cylinder.

Not difficult calculations based on the data provided at http://www.pattakon.com/pattakonIdleValve.htm :

http://www.pattakon.com/VVA_Idle/img004.png .

You know I can't let BS stand so here goes.

Everyone here knows that engines achieve far less residual gas in cylinder than you claim. Insert Explitieve here.

Typically​ well designed engines have around 4% EGR at full load, maybe up to 40 at part loads.

My design due to phasing gets down to 0.5% and if identified as optimal for efficiency at current load demand up to 40% all under software control with very fast response to load changes < 10 ms. Mines bigger, better.

for the Honda - VVA-roller prototype engine of pattakon:

http://www.pattakon.com/VVA_Idle/VVA_Idle_Valves.jpg

http://www.pattakon.com/VVA_Idle/img005.png

Adding the residual gas (circa, 2/10 of the capacity of the cylinder) and the charge required for the engine to idle (circa, another 2/10 of the capacity of the cylinder), the cylinder is not so empty.

With 40% of the capacity of the cylinder occupied, the actual compression (or expansion) ratio is not the geometrical one (10:1) but 2.5:1, or so.

You also write:

“Question: On the design of yours you showed with the last of the transfer occurring after exhaust port closure. How so with no remaining crankcase pressure and a rising piston? I'm thinking, the flow will reverse back into the crankcase - as happens with conventional porting even.”

For low rpm the timing shown in the animation is aggressive.

But for high revving, wherein the inertia of the air gets in play, the timing should be even wilder.

On the other hand, with the asymmetric timing, the duration of the exhaust can be substantially shorter, shifting all the ports lower on the cylinder.


Thanks
Manolis Pattakos

Everything you assume from that point on is erroneous. Why waste everyone's time.

Information provided because this is all well documented in the available literature just incase someone else didn't know.

You have even quoted from the document the real facts come from.

If that doesn't meet the definition of cherry picking I don't know what does.

Trying to make an assertion on flawed logic, hoping someone is having a brain freeze.

You make dealing with government bureaucracy seem intelligent, I did that nearly all day.

Marc

[Muniix]

Hello all.


It is not the physics degree of Kevin Cameron that makes the difference; millions of people have physics (and others) degrees and still cannot understand the basics.

Kevin Cameron, standing firmly on the basic physical laws, can think out of the box, can calculate, can predict, can reject and, the most difficult, can dream.


Quote from Kelvin Cameron / CycleWorld magazine, about the unbelievable evolution of the 2-strokes through the years:

http://www.cycleworld.com/sites/cyclewo ... H&fc=50,50

“What were their methods? CFD? Time-area analysis? Laser interferometry mapping? No, they did what we all did in those days; they tried stuff.”

Thanks
Manolis Pattakos

And how did they measure success? How did they understand why?

Researchers spent a lot of effort to produce accurate models, standing on the shoulders of giants in the field, improving the models further.

To not use them is showing them disrespect.

I communicate with them, showing them respect.

I come up with great ideas -- then use compute to verify and optimise. Many of my ideas have been commercialised successfully​. Many not by me including the fastest growing company in the world, only to be destroyed by Microsoft, that could have been me, look what I missed out on. Had near exactly the same as a browser in 1992 subset of SGML and jit language runtime. Uber idea but financial backer didn't go for the Gray legal side of it when Nokia introduced their N9000/9100.

While I've been identifying the optimal average crankcase pressure to minimise piston and cranktrain Aero frictional losses, likely ring blowby increase. You work to maximise the moles contributing to Aero friction in crankcase. And parasitic losses in your balance systems pumped up to 11 compressing air moving masses around.

I'm coding a virtual attribute to contain the energy used in a mesh cell when the energy conservation solution is reached in the higher order functions of CFD.

That way I can optimise cranktrain geometry in the crankcase and energy used by vacuum pump. Achieving the opposite, minimal parasitic losses.
I don't write any code until I've figured out a test for it first.