2 stroke thread (with occasional F1 relevance!)

[manolis]

Hello all.

Port injection.

At http://www.pattakon.com/tempman/Rotax_P ... Patent.pdf is the US6,691,649 patent of Rotax.

Below they are shown three slides (pages) from the above patent:







In the first slide you can see the cited, by the examiner, documents. The list continues to the second page of the patent and comprises 100 patents relating with the same subject matter (port injection in 2-strokes).

In the third “slide” you can see, at the beginning, the priority claimed by Rotax / Bombardier: it is July19, 2000.
This means that the “Port Injection” of Rotax / Bombardier is near to expire (it has three years before expiration, provided they continue to pay the relative maintenance fees).


In the USPTO there is no a KTM patent (or patent application) relative to Port Injection in the 2-strokes.

KTM claims their TPi (transfer port injection) is patented. They should give at least a patent number.


There are hundreds of patents granted for the TPi.
The question is: does anyone of them really solve the problem?

Which problem?

To eliminate the quantity of fuel that passes unburnt to the exhaust, and to achieve the required quality and motion of the mixture during the combustion.

Thanks
Manolis Pattakos

[Tommy Cookers]

the Napier Nomad had of course identical efficiency to the Wright Turbocompound (the fuels make the sfcs different)
nobody wanted to buy the Napier despite its fuel price being 62% of the price of Avgas

UK aircraft operators had little faith in the UK piston engine makers and were waiting for gas turbines (as was the USA)
Sabre, Hercules/Centaurus/ Griffon ? - in 50 years I extracted from people involved a modest approval only of the Merlin
some (ex-Mustang) in the US are pro-British because of the Merlin (and some because of the Harrier)

in the 30s a 2 stroke fighter engine was intended in the UK (anticipating the events of 1940)
instead high-aromatic fuel was introduced (becoming the standard 100/130 Avgas) to give high power via rich mixtures enabling high boost

high boost obtained efficiently gives high maximum power from a relatively small engine
the smaller cylinder size helps allow a decent CR despite the boost
said engine is efficient at cruise powers because it will need less throttling or none (than a bigger engine at this power)
the aircraft engine is power-controlled primarily by load-controlling via propellor pitch not by throttling - it's the aerodynamic equivalent of CVT
that's how a 1700 hp Merlin runs down to 17 gallons/hr and a bigger 1700 hp engine eg Hercules or Pratt & Whitney doesn't

these arguments were also applied to an equivalent 2 stroke of course
yes that also could be noisier and less durable than the conservative ('big fat engine') route
the Crecyites resorted to false accounting ie remember all engines exhaust gives thrust

TPI ? - apparently 50s-70s (timed) injection in road cars claimed better economy by keeping all the fuel in the combustion chamber
but of course these are disparaged as mechanical and so inferior to 'electronic' injection
I assume current car injection is quasi-continuous ie untimed
but does a bit of fuel going to scavenge make any difference ?
as all systems fuel to prevent the oxygen sensor finding any oxygen the outcome will be the same regardless ?

[J.A.W.]

the Napier Nomad had of course identical efficiency to the Wright Turbocompound (the fuels make the sfcs different)
nobody wanted to buy the Napier despite its fuel price being 62% of the price of Avgas


high boost obtained efficiently gives high maximum power from a relatively small engine
the smaller cylinder size helps allow a decent CR despite the boost
said engine is efficient at cruise powers because it will need less throttling or none...
...than a bigger engine at this power..



yes that also could be noisier and less durable than the conservative ('big fat engine') route
the Crecyites resorted to false accounting ie remember all engines exhaust gives thrust

I assume current car injection is quasi-continuous ie untimed...

In fact T-C, as noted in this 'Flight' article - the Napier Nomad showed significant efficiency advantages over the Wright..

See here : https://www.flightglobal.com/pdfarchive ... 01222.html

& so, as was sadly typical, the sorry fate of the Nomad..
.. along with too many other pioneering British advanced engineering projects..
..was due to cruelly deliberate political policy.. ..rather than any outstanding actual/technical difficulties..

T-C your point about the smaller cylinders - is clearly demonstrated by the power & efficiency superiority of
the 24 cyl Sabre VS the 12 cyl Griffon, both being of ~36 litre capacity.. ..yet this is more relevant to SI, however..

The issue of Crecy exhaust thrust was due to the fixed porting, (which reduced efficiency at lower rpm),
but the reportedly awesome sound level produced - certainly indicates the violence of the efflux..
& a 'power valve' or some such variable porting arrangement - would've tempered this attribute effectively..


Current car electronic DI systems must surely be timed, given they were derived from 2T developments..

[J.A.W.]

Hello all.

Port injection...

The question is: does anyone of them really solve the problem?

Which problem?

To eliminate the quantity of fuel that passes unburnt to the exhaust, and to achieve the required quality and motion of the mixture during the combustion.

Thanks
Manolis Pattakos

Hi Manolis,
The final part of the patent claim excerpt ' summary' - below the last passage you have underlined - makes that claim..
..& if KTM have indeed gained approval under Euro 4 emissions reg's.. ergo - it must..

The use of an expensive 'Isoflex grease' as lubricant in the 2T mainbearings of snowmobiles - has been around for years..

For such machines, performance attributes are accorded more importance than economy.. emissions reg's allowing..

[Tommy Cookers]

[quote="Tommy Cookers"]
the Napier Nomad had of course identical efficiency to the Wright Turbocompound (the fuels make the sfcs different)
EDIT
last time J.A.W agreed that the efficiency was the same - and pointed out that the diesel fuel saves weight
the diesel fuel has much higher calorific value than 115/145 Avgas
so .345 lb diesel c. = .37 lb Avgas = identical efficiency
allowing for Nomad (compounds helped by altitude) vs WTC sea level and
airlines (mostly) 7.2 CR WTC's got better sfc than .38 lb that comes from WTC presented c. 1950 CR 6.something

TPI ? - apparently 50s-70s (timed) injection in road cars claimed better economy by keeping all the fuel in the combustion chamber
but of course these are disparaged as mechanical and so inferior to 'electronic' injection
EDIT
this was port injection but timed
yes I know DI is timed but 99.9% of these (4 stroke cars) weren't DI but they were timed

QUESTION
I assume current car injection is quasi-continuous ie untimed
but does a bit of fuel going to scavenge make any difference ?
as all systems fuel to prevent the oxygen sensor finding any oxygen won't the outcome be the same with either type of injection behaviour ??
[/quote]

[Pinger]

QUESTION
I assume current car injection is quasi-continuous ie untimed

I'm not 100% certain but I think they fire injectors in banks (multiples) and split the cycle event between two injection events. Eg, a four cylinder would have cyls # 1 and 4 fired together, and cyls #2 and 3 fired together as a separate bank and at a different time. Cyls # 1 and 4 with split injection events would each see fuel arrive identically in their cycle.
I think that's how it's done. Pretty sure all injectors firing together does not happen and that fully sequential was abandoned as not being worth the complication.

Might be worth investigating MicroSquirt's website. I think they detail how they do it and there may be reference to OEM.

[MrPotatoHead]

QUESTION
I assume current car injection is quasi-continuous ie untimed

I'm not 100% certain but I think they fire injectors in banks (multiples) and split the cycle event between two injection events. Eg, a four cylinder would have cyls # 1 and 4 fired together, and cyls #2 and 3 fired together as a separate bank and at a different time. Cyls # 1 and 4 with split injection events would each see fuel arrive identically in their cycle.
I think that's how it's done. Pretty sure all injectors firing together does not happen and that fully sequential was abandoned as not being worth the complication.

Might be worth investigating MicroSquirt's website. I think they detail how they do it and there may be reference to OEM.

This is incorrect.
Old ecus might have fired in "Batch Mode" but any modern good ECU will run sequential injection.
Some power can be found by timing the injection event to the valve opening event. Especially if the injectors are large enough to run a lower duty cycle - thus being even more accurate on timing.

As far as Microsquirt / Megasquirt goes. The old versions were limited to Batch Fire but since the Megasquirt II they have been capable of full sequential also.

[J.A.W.]

Indeed, as 'Moore's law' - has allowed much more ECU capability - & the current Rotax/BRP E-TEC 850 blurb claims..
..that its - new for 2017 ECU - operates at "32 million cycles per second"!

Here's a dyno report on that machine: http://www.dynotechresearch.com/file_up ... tec850.pdf
Revving the 82mm X 80.4mm twin to 8,050 rpm produced 170 hp from 111 ft/lb tq..
..that 85 hp per cyl compares ah, fairly favourably - to what the current CRF 450 Honda 4T MX is making - (53 @ 8,600)..

& for T-C, as for the Wright turbo-compound 'efficiency' - the Wright was a 'plumbers nightmare/lash-up'
compared to the integrated Napier Nomad unit, thus curiously, being the reverse of usual US/Brit mechanical practise..

[Pinger]

Re sleeve valves (as I saw no mention of). No mention of him ‘knife-edging’ the sleeves’ upper edges (the sealing breakthough IIRC). The ‘knife-edging’ reputedly made the sleeves very vulnerable to damage up to and during assembly.

Bit of a correction to the above - and as sleeves have been getting another airing....
Re-read Ricardo development of exhausting over the sleeve and while they did begin with 'knife-edging' they soon found that it wasn't necessary so abandoned it.

[Tommy Cookers]

it seems that the fun thing to do a few years ago was to convert your boring old 2 stroke diesel to ...... steam !
http://www.internationalsteam.co.uk/tra ... dern11.htm
http://www.rossen.ch/solar/wcengine.html
http://www.google.com/patents/EP2538019A2?cl=en

and several decades ago some tried a combined diesel/steam engine eg in the Schneider-Still loco
https://www.flickr.com/browser/upgrade/ ... 4308709%2F
this had a 2 stroke diesel that pulled away on steam and switched over to diesel at speed (and used waste exhaust heat to raise steam)
(there was in the UK the similar Kitson-Still loco where Mr Still used a 4 stroke diesel combined with steam)
the big point was avoiding the weight and cost of other ways of torque engagment and multiplication eg diesel-electric

[J.A.W.]

Oh no T-C, from 'Moore's law' to 'steam punk' on the same page..

What would Sir Hiram Maxim do? Pull out his 9mm Luger?

[J.A.W.]

Another 'ride report' - on the new TPI KTM: https://www.transmoto.com.au/tested-ktm ... o-strokes/

I note that the KTM tech guy acknowledges, but waffles past - the DI systems - they have in hand..
I guess that if the simple TPI system still makes Euro 4 compliance, & allows them them to sting buyers an extra grand..
( & I do not recall KTM 4T's getting such a price hike, when they picked up FI set-ups, earlier on - but that's 'marketing')..

[Pinger]

I note that the KTM tech guy acknowledges, but waffles past - the DI systems - they have in hand..

At a guess, a delicate 'voice coil' injector based on hi-fi speakers (would you strap your speakers to an off-road motorcycle?) which are bulky and rely on a heat creating, electrical energy consumptive ECU aren't the best solution for a tightly packaged marginally cooled off-road motorcycle expected to operate in searing desert temperatures.

Outboards, PWC, and sleds experience neither the shock loadings or the lack of cooling facilities and are a little more spacious in accommodating hardware. Making a 2T the height of a 4T isn't really playing to 2T strengths. But KTM are never going to say all that out loud!

Their TPI does look good though, And Uniflow's comments on his set-up suggests it works really well.

Thanks for the article BTW.

[J.A.W.]

P, you'd surely be jesting about 'voice coil' DI injectors.. being virtual 'hi-fi' speaker units, they're alike - only in EM concept..

As for being bulky/complex - sure, somewhat, but nowhere near the extent of a massive OHC 4V cylinder head..
..& the purpose is to enhance the inherent 2T advantage, while negating 'simple' operating flaws of basic fuelling..

& if you think that the 'shockloading' scenarios routinely encountered by powerboats & snowmobiles are 'soft'..
..then clearly you haven't experienced/observed a hard run sporting event involving these machines..

As for the technical concerns, BRP/Evinrude would not be supplying Mil-spec units - if they'd failed severe use tests..

I'd bet KTM is starting out with a simple, but proven ( inc' by Uniflow here) 2T TPI for 'marketing' reasons..
..which likely range from 'buyer resistance' due to price/fear of novelty - through to paying BRP tech royalties..

[uniflow]

So with direct injection how are we going to accommodate the smaller twostroke's 125 etc? Not
enough time to inject at plus 9000 rpm, or so ETech have stated. DI is only good for slower turning big capacity engines.