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Author Topic: Twin piston vs Triple piston..  (Read 1840 times)

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Offline 2StrokeDan

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Re: Twin piston vs Triple piston..
« Reply #60 on: August 19, 2018, 07:56:48 pm »
Jealousy doesn't suit you Dan

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Thanks! ;)

I actually like the Triumphs, they are well-built machines. John Bloor based the production lay-out on Japanese models.
 

Offline Offroadrider

Re: Twin piston vs Triple piston..
« Reply #61 on: August 19, 2018, 10:05:13 pm »
Jealousy doesn't suit you Dan

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Thanks! ;)

I actually like the Triumphs, they are well-built machines. John Bloor based the production lay-out on Japanese models.
Has the same stacked gearbox as the TDM/R1 Yamaha but I must add a shit load smoother
 

Offline Oilspill

Re: Twin piston vs Triple piston..
« Reply #62 on: August 19, 2018, 10:11:35 pm »
Jealousy doesn't suit you Dan

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Thanks! ;)

I actually like the Triumphs, they are well-built machines. John Bloor based the production lay-out on Japanese models.
Really, that makes sense/ is interesting. Everyone said Triumph copied BMW, not sure why, totally different layout.

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Offline Offroadrider

Re: Twin piston vs Triple piston..
« Reply #63 on: August 21, 2018, 12:27:27 am »
Jealousy doesn't suit you Dan

Sent from my ANE-LX1 using Tapatalk

Thanks! ;)

I actually like the Triumphs, they are well-built machines. John Bloor based the production lay-out on Japanese models.
Really, that makes sense/ is interesting. Everyone said Triumph copied BMW, not sure why, totally different layout.

Sent from my ANE-LX1 using Tapatalk
Why reinvent the wheel? same as the Yami S10 check the dimensions of the 1200GS pretty similar the only crowd that do totally their own thing on adventure bike is KTM
 

Offline noble steed

Re: Twin piston vs Triple piston..
« Reply #64 on: August 21, 2018, 10:10:56 am »
Back on topic...

As I understand, torque is related to surface area of the piston, ie engine bore. So for the same displacement engine, eg 500cc single, a large bore, short stroke engine will produce more torque at low speed than a small bore, long stroke engine. Although will also have less top end power, lower max rpm, due to inc weight of the piston.

So a single will have more torque at low speed than equivalent displacement twin, which will have more torque at low speed than equivalent displacement triple. Once engine speed gets higher, the difference will become less noticeable. Due to power pulses in the crank cycle, more cylinders will be smoother. Also rev faster and higher, produce more top end power.

The triumph triple may have oodles of torque at 2500rpm, but a single would have the same at 1500rpm.

That said, I would love to have an 800XC in my garage...
 

Offline 2StrokeDan

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Re: Twin piston vs Triple piston..
« Reply #65 on: August 21, 2018, 10:29:02 am »
Torque at peak revs is basically hp times revs.

But torque at low revs is determined by crank leverage, and the longer the stroke, the bigger the crank circle around which the big-end of the connecting rod exerts pressure.

At low revs, a short stroke engine has less torque than a long-stroke of equivalent displacement. [not piston size, but swept volume.], simply becaus ethe long-stroke engine has bigger leverage around a bigger diameter crank web.

A comparison could be seen in the torque of an XT500 at 1500rpm, as opposed to the torque of a 2019 KTM500 at 1500rpm.

Yes, of course, the KTM500 can hardly run at 1500rpm. :peepwall:
« Last Edit: August 21, 2018, 10:32:22 am by 2StrokeDan »
 

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Re: Twin piston vs Triple piston..
« Reply #66 on: August 21, 2018, 10:42:53 am »
Some people still cling to the myth that a longer stroke will produce greater torque due to the greater 'leverage' on the crank. Nonsense of course because this ignores the fact that the smaller bore/longer stroke cylinder will not fill as efficiently, or burn the gas as effectively, and will therefore produce a weaker 'bang' to put it crudely.

High torque depends upon efficient cylinder filling at a given RPM, and at lower revs an engine with smaller inlet ports and a slower rate of valve lift will fill more effectively due to the higher gas velocity and inertia that can be induced at those speeds. At high RPM of course, such an engine will run out of breathing ability, and this explains, in crude terms, why some engines are designed for flat out power while others are 're-tuned' for a strong spread of torque across the range.
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Offline 2StrokeDan

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Re: Twin piston vs Triple piston..
« Reply #67 on: August 21, 2018, 06:15:42 pm »
Some people still cling to the myth that a longer stroke will produce greater torque due to the greater 'leverage' on the crank. Nonsense of course because this ignores the fact that the smaller bore/longer stroke cylinder will not fill as efficiently, or burn the gas as effectively, and will therefore produce a weaker 'bang' to put it crudely.

High torque depends upon efficient cylinder filling at a given RPM, and at lower revs an engine with smaller inlet ports and a slower rate of valve lift will fill more effectively due to the higher gas velocity and inertia that can be induced at those speeds. At high RPM of course, such an engine will run out of breathing ability, and this explains, in crude terms, why some engines are designed for flat out power while others are 're-tuned' for a strong spread of torque across the range.

I think it is basic mechanical groundrules that a bigger offset crankpin will unfailingly result in bigger connecting rod leverage, and more torque at low revs.

Keep in mind that this low-rev scenario allows ample time for cylinder filling in an engine not designed to operate at high revs.

You actually go ahead and explain to yourself why a short-stroke engine will never, unless you employ VVT, have the low-down torque of a long-stroke engine.

Just like a long-stroke engine will never make peak power comparable to a short-stroke.

PS; I would completely agree with you when it comes to race engines. But to get a thumper to work well at really low revs, forget about a short-stroke.
« Last Edit: August 21, 2018, 06:21:12 pm by 2StrokeDan »