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Why aren't big bikes ever 2t?

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5v3d3b0
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PostPosted: 22:47 - 14 Jun 2007    Post subject: Why aren't big bikes ever 2t? Reply with quote

Imagine a 600cc 2 stroke. How much bhp could that produce honestly. I at least am under the impression that 2t beats 4t in power output...
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Kickstart
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PostPosted: 22:52 - 14 Jun 2007    Post subject: Reply with quote

Hi

140hp should be fairly easy, but packaging the bulky exhausts and keeping it legally quiet would be an issue. Never mind getting it anywhere close to the emissions rules.

All the best

Keith
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JakeyR
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PostPosted: 22:54 - 14 Jun 2007    Post subject: Reply with quote

Not economical, from what my college tutor told me, i asked him the same question a few weeks back.

EDIT: Keith beat me too it, and with a far better explanation. Razz
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bish777
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PostPosted: 22:56 - 14 Jun 2007    Post subject: Reply with quote

A supercharged fuel injected two stroke would not require any expansion chamber. The FI means that fuelling can be precisely controlled so none is blown up the exhaust (making a expansion chamber redundant).

The supercharging also means the crankcase isnt used as part of the induction so can be sealed the same as a 4 smoke. It neednt be a high pressure supercharger, it only has to provide enough pressure to fill the cylinder at atmospheric pressure.

Should mean a cleaner greener stroker.
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mr.z
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PostPosted: 23:10 - 14 Jun 2007    Post subject: Reply with quote

Quote:
Suzuki's GT750 motorcycle was launched in 1971. The GT750 was Suzuki's competitor in a market populated by the likes of Honda's CB750 and the Kawasaki Z1. The GT 750 was also nicknamed the "Kettle" and the "Water Buffalo", for its liquid cooling system (and also in the latter case its substantial weight).

Never intended as a sportsbike, the GT was targeted more at the tourer market, hence the 'GT' nomenclature. Power output of the early models was a claimed 67 BHP, not especially impressive for the time. Handling and braking would, by modern standards, be considered alarming. Top speed in contemporary road tests was around 110 MPH.

In modern times the GT has acquired something of a cult status, mainly due to its two-stroke engine and the historical rarity of liquid cooling in this class.

As an aside, the GT 750 motor was the basis for the 180 MPH racing bike on which Barry Sheene had his infamous high-speed Daytona accident in March 1975. He went on to win the world 500 CC championship in 1976 and 1977.


http://www.suzukicycles.org/photos/GT/GT750/1977_GT750_blue_540.jpg

The biggest i can think of at least..

Bit of an odd one.. all ways fancied one for the sheer ridiculousness of them

Add this to that allegedly a modern 50cc two stroke makes emissions close to that of a BUS, an old crap bus at that..

Interesting the FI point, aprilia were considering it for their 125s e.t.c. not sure why they didn't go ahead as they must have been pretty sure its doable.

Consider this though.. the amount of energy/emissions from manufacturing a 4stroke are far higher, vastly more complex engine with more parts, if dodgy Chinese 4strokes are only managing 5000 miles before terminal engine failures then has there been much of a gain environment wise? Question
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St0rmer66
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PostPosted: 23:24 - 14 Jun 2007    Post subject: Reply with quote

mr.z wrote:
Interesting the FI point, aprilia were considering it for their 125s e.t.c. not sure why they didn't go ahead as they must have been pretty sure its doable.

Consider this though.. the amount of energy/emissions from manufacturing a 4stroke are far higher, vastly more complex engine with more parts, if dodgy Chinese 4strokes are only managing 5000 miles before terminal engine failures then has there been much of a gain environment wise? Question

Aren't Aprilia a pretty small company? So they don't have the financial means to research and develop the fuel injection for the 2strokes. Honda being the biggest bike manufacturer decided that 4strokes were the way to go (since they were so good at them) and so that's the way the whole industry had to follow. I've heard many people speculate that had they developed 2 stroke engines more, they could be even better than the 4 strokes we have now... but it's unlikely we will ever know.
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bish777
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PostPosted: 23:26 - 14 Jun 2007    Post subject: Reply with quote

You could have a 1000cc 2stroke with the same power as a same capacity four stroke. Just run the thing at much lower RPM. Should make the motor last longer
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Kickstart
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PostPosted: 23:32 - 14 Jun 2007    Post subject: Reply with quote

St0rmer66 wrote:
Aren't Aprilia a pretty small company? So they don't have the financial means to research and develop the fuel injection for the 2strokes.


They are a fair size, and are now owned by Piaggio so part of the 4th largest motorcycle manufacturer.

St0rmer66 wrote:
Honda being the biggest bike manufacturer decided that 4strokes were the way to go (since they were so good at them)


Honda have always hated 2 strokes. They spent massive sums of money developing the oval piston NR500 GP bike is a failed attempt to keep up with the 2 strokes and in the end gave up and built a 2 stroke themselves.

St0rmer66 wrote:
I've heard many people speculate that had they developed 2 stroke engines more, they could be even better than the 4 strokes we have now... but it's unlikely we will ever know.


Ford had a fleet of 2 stroke Fiestas a decade or so ago (Orbital designed 2 stroke engine, people who licenced the design to Aprilia for the DiTech system I think). Problem was they were getting ~50000 mile engine life which was not considered long enough.

All the best

Keith
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mr.z
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PostPosted: 23:38 - 14 Jun 2007    Post subject: Reply with quote

Weren't some saabs 2stroke? Neutral (i'm sure a myriad of dodgy eastern block cars have been also)
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Kickstart
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PostPosted: 23:39 - 14 Jun 2007    Post subject: Reply with quote

mr.z wrote:
Weren't some saabs 2stroke? Neutral (i'm sure a myriad of dodgy eastern block cars have been also)


Yep. Been a few 2 stroke cars years ago.

All the best

Keith
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hmmmnz
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PostPosted: 01:11 - 15 Jun 2007    Post subject: Reply with quote

suzuki also had some of their eary 4x4 as 2strokes
http://suzuki.off-road.com/suzuki/data/articlestandard/suzuki/532005/277664/lj50.gif
a 600 cc 3 cylinder
and the sabb sonett with its 841cc engine
http://www.motorbase.com/pictures/nec_1998/std_saab-sonnet.jpg

and the new daihatsu sirion 2cd
http://www.daihatsu.com/motorshow/frankfurt99/s2cd/photo/bigimg/img/01.jpg
A 3-cylinder, 987 cc, two-stroke cycle diesel engine
http://www.daihatsu.com/motorshow/frankfurt99/s2cd/photo/bigimg/img/06.jpg
its uses less that 3 litres of deisel per 100 km and has both a supercharger and varible turbo
read more http://www.daihatsu.com/motorshow/frankfurt99/s2cd/index.html
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Diggs
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PostPosted: 08:18 - 15 Jun 2007    Post subject: Reply with quote

The biggest two stroke bike I can think of is the Ossa 1000 - basically two 500 twins stuck together... They raced one years back and it gained a reputation as a dangerous bike to ride... wonder why?

http://img.photobucket.com/albums/v237/DiggsUK/Ossa1000.jpg
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5v3d3b0
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PostPosted: 12:31 - 15 Jun 2007    Post subject: Reply with quote

But imagine a bike like the R1 but in 2t. If it's already basically sneeze and you risk a wheelie...Wouldn't a high performance 2t be insanely fast and torqueish?
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feef
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PostPosted: 13:58 - 15 Jun 2007    Post subject: Reply with quote

you want a BIG and POWERFUL 2 stroke?

try this turbo charged diesel 2-stroke with 108,920 hp at 102 rpm and 5,608,312 lb/ft at 102rpm :

http://people.bath.ac.uk/ccsshb/12cyl/

Laughing

a
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hmmmnz
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PostPosted: 13:59 - 15 Jun 2007    Post subject: Reply with quote

the thing with smokeys the larger you go the smaller the gap in performance between 2t and 4t if you were to get to 1000 cc you would get far more from a 4t power wise and reliability still wouldn't be compromised. after about 500cc you are basically wasting your time.
although there is an ozzie that is currently working on a 6 stroke,
basically a 4 stroke bottom end with a 2 stroke top end (no valves just ports)
http://www.sixstroke.com/
http://www.sixstroke.com/images/sixstroke.gif
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BFG
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PostPosted: 14:32 - 15 Jun 2007    Post subject: Reply with quote

Diesels are two stroke by nature and always have been (there are exceptions). I'd think it's fair to say that diesels are out of topic in the bike debate.

2 Stroke petrol engines have problems with upper engine lubrication. Smaller engines have less surface area to worry about, but as the CC increases, the surface area of the contact between metals also increases. However, you can't just keep adding more oil, and so it becomes self-defeating.

Materials technology might help. Smile
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5v3d3b0
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PostPosted: 14:34 - 15 Jun 2007    Post subject: Reply with quote

I'm guessing a 20x50cc cylinder 2t engine wouldn't really be practical... 20 exhausts...What would that look like?
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feef
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PostPosted: 14:40 - 15 Jun 2007    Post subject: Reply with quote

BFG wrote:
Diesels are two stroke by nature and always have been (there are exceptions). I'd think it's fair to say that diesels are out of topic in the bike debate.


Eh!??

In Ship engines, such as the one I posted, you'll find 2-stroke diesels.. but every other diesel engine you'll come across in day-to-day use is a 4-stroke.

a
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Cigaro
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PostPosted: 14:40 - 15 Jun 2007    Post subject: Reply with quote

BFG wrote:
I'd think it's fair to say that diesels are out of topic in the bike debate.


There are a few diesel-powered ratbikes about.

I'd love to see a powerful two-stroke diesel bike. Gargantulum quantities of smoke everytime you touch the throttle - I like Very Happy

Also, feef - locomotive genset engines are two-stroke.
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BFG
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PostPosted: 15:03 - 15 Jun 2007    Post subject: Reply with quote

feef wrote:
BFG wrote:
Diesels are two stroke by nature and always have been (there are exceptions). I'd think it's fair to say that diesels are out of topic in the bike debate.


Eh!??

In Ship engines, such as the one I posted, you'll find 2-stroke diesels.. but every other diesel engine you'll come across in day-to-day use is a 4-stroke.

a


Oops. Sorry was cutting / pasting stuff and I fucked up. Ignore first sentence. Mr. Green
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Ravo
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PostPosted: 16:44 - 15 Jun 2007    Post subject: Reply with quote

I don't know about large 2 strokes, but I've always wanted to see a larger (>=750cc) diesel that was actually practical to ride.
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pwntifex
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PostPosted: 16:49 - 15 Jun 2007    Post subject: Reply with quote

http://people.bath.ac.uk/ccsshb/12cyl/rta96c_crank.jpg

Feef's engine. Wink
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Last edited by pwntifex on 18:41 - 15 Jun 2007; edited 1 time in total
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Jack_Cheese
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PostPosted: 17:43 - 15 Jun 2007    Post subject: Reply with quote

I think the cathederals can be ignored as far as 2-stroke debate goes!

Previous attempts at big 2-strokes have lead to problems with overheating problems. The old kawasaki 750 triple was notorious for destroying the middle cylinder IIRC.

bish777 wrote:
A supercharged fuel injected two stroke would not require any expansion chamber. The FI means that fuelling can be precisely controlled so none is blown up the exhaust (making a expansion chamber redundant).

The supercharging also means the crankcase isnt used as part of the induction so can be sealed the same as a 4 smoke. It neednt be a high pressure supercharger, it only has to provide enough pressure to fill the cylinder at atmospheric pressure.

Should mean a cleaner greener stroker


Seams that your dream is becoming reality;

hmmmnz wrote:
there is an ozzie that is currently working on a 6 stroke,
basically a 4 stroke bottom end with a 2 stroke top end (no valves just ports


To be honest, i can only see one major downfall. Sure, the engine would burn less oil, be quieter and potentially be more reliable. But it would still need an expansion chamber to reduce emissions. The design of the 2-stroke engine means that the exhaust port is open while the piston is at the bottom of it's stroke, and inevitably some fuel will be lost through this gaping hole in the side of the bore.

another way round it would be to pressurise the mixture beyond atmospheric pressure using said supercharger, and inject it after the piston has gone past the exhaust port. There would be no increase in performance from this, but it would keep the engine clean and help the 2-stroke keep on living.

The thing is, new engines like this just aren't 2-strokes. A proper 2-stroke has an expansion chamber, burns gallons of oil, a powervalve blade in the exhaust and a full top-end rebuild can be done in under an hour. A new complex engine wouldn;t be the same, all the magic appeal of the 2-stroke would be lost.

Jack
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Ariel Badger
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PostPosted: 17:53 - 15 Jun 2007    Post subject: Reply with quote

feef wrote:
you want a BIG and POWERFUL 2 stroke?

try this turbo charged diesel 2-stroke with 108,920 hp at 102 rpm and 5,608,312 lb/ft at 102rpm :

http://people.bath.ac.uk/ccsshb/12cyl/

Laughing

a


Beat me to it Very Happy
I used to make the intercoolers for those buggers.
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