Squeak 17
Big power from a small number of cylinders for Cruiser bikes, why not for cars?
By
sundevil777, in The Bonfire
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sundevil777 93
QuoteThe more pistons rotating a crank, the more steady application of power and less space between ignition. a 4 cylendar engine is limited for ignition every 180 degrees of crank rotation. an eight cylendar engine rotates every 90 between ignition. This allows for more torque at a lower rpm due to a steadier application of power.
Not at all true. You don't get more low rpm torque due to a multi-cylinder engine's steadier application of power. In fact, for engines of similar displacement and similar bore/stroke ratio, both tuned as racing engines for power, an engine with more cylinders will have a power and torque curve that peaks at a higher rpm.
Contrary to what most think, horsepower isn't directly measured on a dynamometer. Torque is measured, and is converted to horsepower by the formula HP=(Torque(in ft-lbs)xrpm)/5252. The relationship between torque and power really is that simple.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am
1969912 0
Comparing bike and car engines is an apples/oranges comparison.
Horsepower is just (Torque x RPM). To get, say, 150 HP, you can have tons of torque resulting in 150 HP at 3000 RPM, or you can have lower torque and get the HP at 11,000 RPM.
Torque is what's really important since it's what produces the force needed to overcome vehicle weight and produce acceleration.
Because a bike and rider might weigh only ~700 lb., engine torque requirements are less than what is required for a 3000 lb. car. To get the same acceleration, the car requires more than 4x the engine torque that the bike needs. Put a bike engine in a car and it will not have the torque needed to effectively get the car moving from a stop. his could be overcome somewhat through gearing, but that has it's own problems. Engine performance requirements for bikes and cars are totally different.
"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."
-NickDG
Horsepower is just (Torque x RPM). To get, say, 150 HP, you can have tons of torque resulting in 150 HP at 3000 RPM, or you can have lower torque and get the HP at 11,000 RPM.
Torque is what's really important since it's what produces the force needed to overcome vehicle weight and produce acceleration.
Because a bike and rider might weigh only ~700 lb., engine torque requirements are less than what is required for a 3000 lb. car. To get the same acceleration, the car requires more than 4x the engine torque that the bike needs. Put a bike engine in a car and it will not have the torque needed to effectively get the car moving from a stop. his could be overcome somewhat through gearing, but that has it's own problems. Engine performance requirements for bikes and cars are totally different.
"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."
-NickDG
billvon 2,400
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> So why is it that there are no cars that have large displacement engines
>with very few cylinders?
Because in general more cylinders = smoother power output and less vibration transmitted to the frame. Both are valuable selling points in cars.
>with very few cylinders?
Because in general more cylinders = smoother power output and less vibration transmitted to the frame. Both are valuable selling points in cars.
sundevil777 93
Quote> So why is it that there are no cars that have large displacement engines
>with very few cylinders?
Because in general more cylinders = smoother power output and less vibration transmitted to the frame. Both are valuable selling points in cars.
I do realize that most car owners prefer smoothness. I'm just taking a jab at the cruiser bike owners that for some reason prefer the opposite. I can't understand it, or at least I can't understand why at least there isn't some segment of the auto industry where similar characteristics are appreciated. Why don't at least some car owners enjoy the throttle blip bark from the nearly simultaneous ignition of a big V-twin that gives them such joy on their bikes?
The owners of such bikes that wake me with that bark are lucky I believe in an afterlife, or else I would be more likely to seek a violent revenge.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am
1969912 0
Quote> So why is it that there are no cars that have large displacement engines
>with very few cylinders?
Because in general more cylinders = smoother power output and less vibration transmitted to the frame. Both are valuable selling points in cars.
Not to mention problems with mixing, flame propagation, quenching, heat transfer, etc., with larger diam. cylinders.
"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."
-NickDG
sundevil777 93
QuotePut a bike engine in a car and it will not have the torque needed to effectively get the car moving from a stop.
The big displacement cruiser bike engines are tuned for lots of low speed power and torque. That is exactly what is expected for a normal (not high performance) car. The biggest of the bike V-twins already have similar displacement as some small cars, so they should actually be better suited to providing good low rpm acceleration response.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am
1969912 0
QuoteQuotePut a bike engine in a car and it will not have the torque needed to effectively get the car moving from a stop.
The big displacement cruiser bike engines are tuned for lots of low speed power and torque. That is exactly what is expected for a normal (not high performance) car. The biggest of the bike V-twins already have similar displacement as some small cars, so they should actually be better suited to providing good low rpm acceleration response.
It's actually being done with Harley v-twins, but the car had better be very lightweight to make use of an engine with ~ 60lb-ft max torque. It could also be done with a rocket bike motor, but major gearbox raito changes would be needed or a separate gearbox used.
http://thekneeslider.com/archives/2006/09/15/twintech-v-twin-motorcycle-powered-car/
Here's a Hyabusa V8. Now that's more like it - but is's 2.6 liters.
http://thekneeslider.com/archives/2005/02/09/hayabusa-v8-engine/
"Once we got to the point where twenty/something's needed a place on the corner that changed the oil in their cars we were doomed . . ."
-NickDG
sv3n 0
or you could just go this route, while it's a four cylinder is would be sooooo much fun
..........
http://www.ktm-x-bow.com/index.602.0.html
...and you're in violation of your face!
Here's a larger displacement 4 cylinder.
I've got a couple.
----------------------------------------------
You're not as good as you think you are. Seriously.
You're not as good as you think you are. Seriously.
nanook 1
QuoteIn fact, for engines of similar displacement and similar bore/stroke ratio, both tuned as racing engines for power, an engine with more cylinders will have a power and torque curve that peaks at a higher rpm.
will the same hold true if the bolded section was rephrased to show an engine tuned for work applications? Not meant to get off subject, but does the number of cylendars really have a huge effect on RPM peaks or does the cam profile claim a larger responsibility here? And to put myself into learning mode here: With the same considerations but with a demand to keep an engine spinning roughly at 600 rpms, would you rather have an 8 cylendar or a 4 cylendar to take up the task?
_____________________________
"The trouble with quotes on the internet is that you can never know if they are genuine" - Abraham Lincoln
"The trouble with quotes on the internet is that you can never know if they are genuine" - Abraham Lincoln
sundevil777 93
QuoteQuoteIn fact, for engines of similar displacement and similar bore/stroke ratio, both tuned as racing engines for power, an engine with more cylinders will have a power and torque curve that peaks at a higher rpm.
will the same hold true if the bolded section was rephrased to show an engine tuned for work applications? Not meant to get off subject, but does the number of cylendars really have a huge effect on RPM peaks or does the cam profile claim a larger responsibility here? And to put myself into learning mode here: With the same considerations but with a demand to keep an engine spinning roughly at 600 rpms, would you rather have an 8 cylendar or a 4 cylendar to take up the task?
I'll take a shot at answering your questions.
An engine with large cylinders will not be able to spin as fast (rpm) because of inherent stresses due to heavier reciprocating parts and limitations on the piston linear velocity. Managing the stresses in both the piston/crank and the valve train are limitations on high rpm engines.
If you would want an engine to constantly operate at a much lower rpm than maximum, then a large number of cylinders isn't much advantage, and then you would want a cam profile tuned with little overlap of exhaust closing/intake opening, and an earlier intake closing than normal. Of course if an engine is never going to be operating anywhere near its max rpm, then it is a much larger engine than needed, but you get the advantage that it will be under little stress.
People are sick and tired of being told that ordinary and decent people are fed up in this country with being sick and tired. I’m certainly not, and I’m sick and tired of being told that I am
QuoteVibration and the rolling thunder sound is apparently very desirable for motorcycles. So why is it that there are no cars that have large displacement engines with very few cylinders?
"very few cylinders" may not apply here but...
http://www.bosshoss.net/view_bike.asp?x=BHC3502
My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239
kallend 1,623
QuoteQuote> So why is it that there are no cars that have large displacement engines
>with very few cylinders?
Because in general more cylinders = smoother power output and less vibration transmitted to the frame. Both are valuable selling points in cars.
Not to mention problems with mixing, flame propagation, quenching, heat transfer, etc., with larger diam. cylinders.
Bingo!
Large cylinders produce all kinds of engineering problems from heat transfer (cooling) to timing, rate of filling, detonation, thermal degradation of the valves, and stress cracking in the cylinders, pistons and heads. The very large radial aero engines used before jets became commonplace are testimony to this.
...
The only sure way to survive a canopy collision is not to have one.
The only sure way to survive a canopy collision is not to have one.
Quote...The very large radial aero engines used before jets became commonplace are testimony to this.
Good thing they came with "jugs", eh?
My reality and yours are quite different.
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239
I think we're all Bozos on this bus.
Falcon5232, SCS8170, SCSA353, POPS9398, DS239
A 125cc two stroke GP bike weighs 75kg and puts out 130 odd horses.
MotoGP bikes are at about 1:1 for pwer to weight NO cars have that.
My Life ROCKS!
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