naturally aspirated 3.0l V12 by todays standards

[Tommy Cookers]

..... "...the advantages are far more pronounced when it is applied to a 2T design, preferably with 3 cyl or multiples thereof...
The typical port timing of a 3 cyl, 2T unit is that the exhaust blows down 90`after TDC... ( &) ...120` disposed from that
blowdown process the engine is closing up the exhaust port in an adjacent cyl. This means that the blown gas from
one cyl helps to charge the adjacent cyl... a high pressure pulse arrives at the port, just in time, & forces the mixture back in...
'The beautiful part of the process is that the effect occurs right across the speed range,& this makes the 3 cyl set-up an optimum configuration.' ".

the above is a road engine scenario, that DKW seemed to discover after they bought a 3 cylinder Scott 1000cc motorcycle prototype in 1939
(and endorsed in Saab's SAE paper in the late 1950s on their replacement of the twin with the three)
it won't give 300 hp/litre - that demands charging aided by the strong low pressure pulse of a race-type 'expansion chamber' system
the 2 stroke seems (including such chambers) rather bulky and/or wide for the situation apparently envisaged in this thread
and we know in established engine types the stroke will need to be almost double the recent N/A 4 stroke's for adequate port size

[J.A.W.]

T-C you have it back-to-front.. the N/A 4T must run massively over-square B X S to allow for the valve area/rpm needed..
..since for a given capacity 4Ts are lazy workers except at super-high rpm - unless blown..

& running so many rpm to compensate for 1/2 time BMEP = expensive material components - to hack the stresses..

Performance oriented 3 cyl motorcycles/snow & water craft have all utilized the 3-1 pipe scheme, even though maximum hp at high rpm is usually obtained by treating all cylinders as discrete units with an individual intake & pipe for each.

AFAIK, no recent work has been done on simulations of the thread topic, with examination of the potential synergies
from running 12 high performance 2T cylinders in a resonant unit , but linking 12 discreetly operated 2T cylinders in
'bout any practicable arrangement, & 300hp/Ltr - would even so - certainly not be a problem..

See here below, for an inline six 2T powered snow-mobile with a 1/2 doz nicely arranged individual expansion chambers..

https://www.youtube.com/watch?v=vsZTKAWdA2A

[J.A.W.]

This article: http://www.jagweb.com/aj6eng/ret/index.php
.. shows the developmental changes by in N/A F1 - by comparing the `60s-on legend Cosworth &,`09 Toyota F1 mills..

(mainly via lots more- expensively supported - rpm)..

[gruntguru]

Great article Jaw! I'd have given you 2 votes if it was possible.

[Tommy Cookers]

we should all have on our hard discs or in our memories ......
the article c 2008 on the then-current Cosworth F1 engine
the Instrumentation/Measurement Journal paper on combustion measurements in Ferrari F1 engines c 2007
links to these were posted on this site

the Ferrari work shows combustion at c17000 rpm as fast (but not ideally so), and rich mixture usefully reducing combustion variability in affected cyls
and interestingly, ignition advance is far more than Mr Bywater mentions

RCE tells us Cosworth chose ordinary Al alloy pistons (ie no beryllium magic) for their 20000 rpm capable engine
as the rules later compelled in all makes of 18000 rpm-frozen engines, along with other 'cheap' materials

JAW's 2 stroke Honda 500 cc twin (conventional b:s ratio = 1 ie stroke c 68 mm) is at its c11500 rpm equivalent in piston acceleration .....
to our notional V12 4 stroke (conventional b:s ratio = 2.4 ie stroke c 38 mm) at c15500 rpm
the 4S piston has a large crown/pin boss and little else, the 2S piston is much deeper, so their weight is roughly similar

later the F1 engines were limited to 17000 rpm (and were often run slower and less rich), but still made their 300 hp/litre


re 2 strokes .....
sincere question - is the mean exhaust pressure in the expansion chamber significantly higher (or not) than atmospheric pressure ?
btw - the BB NSR 500 must have had imo a 'N-S-N-S' crank to give its paired firing at 0 deg and at 68 deg - how else ?
and we think the Honda varietous 'try everything once' design philosophy is new !! ??

[Edis]

we should all have on our hard discs or in our memories ......
the article c 2008 on the then-current Cosworth F1 engine
the Instrumentation/Measurement Journal paper on combustion measurements in Ferrari F1 engines c 2007
links to these were posted on this site

the Ferrari work shows combustion at c17000 rpm as fast (but not ideally so), and rich mixture usefully reducing combustion variability in affected cyls
and interestingly, ignition advance is far more than Mr Bywater mentions

There is a delay between the spark being fired and heat being released in the cylinder and as engine speed increase this delay will increase in duration requiring more spark advance. So with the later and higher speed F1 engines running a lot more spark advance, only a small amount of heat is actually released before top dead center.

A "fast combustion" isn't determined based on ignition advance, but typically the crank angle between 10% and 90% fuel mass burnt.

[J.A.W.]

...re 2 strokes .....
sincere question - is the mean exhaust pressure in the expansion chamber significantly higher (or not) than atmospheric pressure ?
btw - the BB NSR 500 must have had imo a 'N-S-N-S' crank to give its paired firing at 0 deg and at 68 deg - how else ?
and we think the Honda varietous 'try everything once' design philosophy is new !! ??

Engineer Kaaden at MZ realized that a 2T race engine - is an effective mechanical method of transmitting pulse jet energy..
He recalled the research done during the Nazi missile programs & utilized the Kadenacy sonic-wave effects in a practicable way.

The geometry of the expansion chamber allows for the highly energised sharp shot of exhaust blown down by a rapidly opened port to be properly used in a sonic energy wave/resonant flow system - ( viz: see the head vs tailpipe relative diameter ).

As the article above briefly noted, Toyota also must have utilized Kadenacy effects in their N/A 4T F1 engine..

Water injection into exhaust gas streams - to alter gas velocities by temperature/density control- had been used in 2T racing outboard marine engines by OMC, prior to Honda, & yes, Honda tried various crankpin/crankcase V-angle configurations, in its single crankshaft NSR 500/4 mill.

[J.A.W.]

Here, an ex-outboard boat motor is modified for use by rude-boys in a hot-rod.. ( & V8 expansion chambers neatly arranged)..

https://www.youtube.com/watch?v=RoiWpJLokEc

[Tommy Cookers]

btw ......
Kaaden was Mr Disc Valve not Mr Expansion Chamber (though the DV had been used before by Sun Vitesse and by Dooling etc)
DKW having invented the expansion chamber c 1954 and conspicuously almost won the 350cc WC with it in 55/6
(though the 350 Garelli seemed to have some idea c 1928)
Kadenacy didn't invent anything related to 4 strokes
he invented exhaust geometry to charge a 2 stroke diesel (unusually large exhaust ports somewhat equivalent to ports opening earlier)
he used in the late 30s such tuned exhaust (and inlet) for Armstrong-Whitworth on constant-low-speed/constant-load 2s generation diesels
N/A with a 65' ? exhaust pipe replacing blower-charging or crankcase compression charging
any IPR claim via his (1933) patent (against US 2 stroke makers ?) was untenable due to lack of evidence ?
resonant pipe lengths were known years before, there's a 1932 article in a US boating magazine showing such a reader's project
for Kadenacy ?, try these http://www.google.es/patents/US2581668
http://www.google.is/patents/US2102559
http://www.google.is/patents/US2123569
http://www.google.ca/patents/US2431266
http://www.google.ca/patents/US2281585
against him ? , try these https://www.google.com/patents/US4924956 (this may explain why some have denied awareness of Kadenacy)
http://pme.sagepub.com/content/161/1/98.abstract
others related ?
http://www.google.com.gt/patents/US3064417
http://www.google.co.uk/patents/US2595932

the EC only works with port opening earlier than conventionally ideal (normal 2 strokes are inherently worse in this respect than 4 strokes)
so how would the sfc/race fuel weight of the 2 stroke, even with DI (did eg the NSR500 ever have DI?) compare with those of the 4 stroke ?
wouldn't the fuel issue (now limited to 22 litres in Moto GP) anyway kill the 2 stroke (at 300 hp/litre) as in our N/A F1 concept ?

[J.A.W.]

W. Kaaden at MZ was able to build a winning 2T G.P. machine on a shoestring budget, T-C.

On page 39 of the 1957 edition of 'Automobile Year' is an article featuring these 2T developments..
.. unequivocally stating that it is "...the work of many minds, & not of a single man."

& lets not conflate the current 'fuel economy' formula - with actual proven cost effective racing..

The sealed 'engine in a box' which is inviolable to the on-track engineer/tuner ( not allowed, even gear ratio selections!),
is sterile, compared to the days when different tracks would require a tuned set combination of top-end/pipes & carbs,
let alone a specific gear ratio selection.

Of course a clean sheet design N/A 3 ltr 2T 12cyl F1 mill would best a 4T rival, in so many parameters, not least cost..

& some are still doing 2T R & D.. http://www.iffitech.com/project/gp-piston/

[J.A.W.]

See this link for an interesting view of a 2T Kawasaki racing 750/3 cylinder - inline block - showing the porting arrangements..

http://www.kawasakitriples.myfastforum. ... 10413.html