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Krunok

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Torque is used to calculate power, without speed it tells nothing, an engine producing infinite torque at zero rpm is producing no power and going nowhere.
That is indeed so, unless your engine is electic motor - as they have torque at 0 RPM they will actually start going even from 0 RPM. That's why we used them as starters for poor old internal combustion engines which really can't go anywhere at 0 RPM. :)
 

Frank Dernie

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That is indeed so, unless your engine is electic motor - as they have torque at 0 RPM they will actually start going even from 0 RPM. That's why we used them as starters for poor old internal combustion engines which really can't go anywhere at 0 RPM. :)
I have a plug-in hybrid which is very sprightly from low speed but it also isn’t going anywhere at 0 rpm, and once the car is moving it is still the power curve which counts.
 

Krunok

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I have a plug-in hybrid which is very sprightly from low speed but it also isn’t going anywhere at 0 rpm, and once the car is moving it is still the power curve which counts.
How do you get it going then? With gasoline engine?

Anyway, electric motor will move from standstill the same way the electric starter in your car gets going from standstill to start your gasoline engine. It only has to hae enough force (torqu) to move a little. As DC motors have pretty much flat torque curve all the way to max RPMs the power will raise in a linear fashion as the motor gains RPMs.
 
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It was in the link I posted. Torque may be present with a non-rotating motor, but power is 0, because the rotation in equation is 0. When it starts moving/rotating, power "happens"

This discussion started from driveability and aggressiveness of certain engine types. Torg/power curves are done at full throttle on dyno and they tell the maximum capacity of the engine. However, outside racing we hardly ever push gas pedal down and hold it there for even tens of seconds. How a car or a bike feels at normal everyday cruising, comes very much from max torq/power at low rpm and throttle response. Throttle response is determined by valve timing, injection and ignition control, intake/exhaust port control etc. modern "black box"programming (and gearbox programming if automatic) Consumer market cars hardly ever use full potential of the mechanics powerwise, because they must fulfill also emission controls! Chip tuning is popular now, even among truckers and farmers!
 
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noobie1

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I own two cars 2015 Audi A6 and 2015 Lexus GS Sport. Love driving the A6 but hate the Bose audio system. Driving the Lexus is less fun but the Mark Levinson audio system sounds really good.
 

JJB70

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The relative importance of power and torque is largely determined by the application. There are applications where torque is a significant limiting factor, particularly those needing very high starting and low speed effort. A lot of marine engines are more limited by torque than by power.
 

Krunok

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There are applications where torque is a significant limiting factor, particularly those needing very high starting and low speed effort.
As there is a linear relationship between the two which depends on RPM and that power is actually doing the work I really think torque is being mentioned much too often without any reason at all. With internal combustion engines it's anyhow all about cylinder pressure and the generated power. Torque is quite insignificant thing in between mostly being mentioned by folks who don't understand it (and here I don't mean you).
 

Blumlein 88

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Another unusual compared to modern power curve is like those of large American sedans from the 1930s. Think Buick, Packard, that sort of car. A large displacement straight 8 with a very long stroke. Peak torque was at low rpm vs modern engines. Low power output for the displacement.

With such an engine in the time before automatic transmissions, you can get the car up to speed, and once in high gear just leave it there. It would pull down to 3 or 4 mph and smoothly, slowly accelerate back up to speed without getting out of high gear. Much reduced the amount of shifting.

I've not looked at any motorcycle mags in years. I know at one time they would include a test of top gear acceleration time for 50-70 mph or maybe it was 50-80 mph. Basically trying to make V-twins look good in a passing scenario. The large slow turning engines did fairly well in such a test vs sport bikes. Of course any sport bike owner wanting to pass someone would drop 3 gears and be long gone in the real world because they have so much more power. The torque of the V-twin doesn't get it done without power.

Someone mentioned peaky 2 stroke racing bikes. Yeah those are horrible in my opinion for use on public roads, but quite the ride if you have a chance to air one out on a track.
 

Krunok

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One more thing: let's not forget that there is a gearbox between the engine and the wheels. Gearbox acts as a power transfer box where torque gets traded for speed - for that reason some call it a "torque converter", which basically it is. That means that pretty much all the engine power (minus various losses) is transferred to the wheels to do some work while torque is progressively reduced to enable advance in speed. So engine torque is really not something that needs to be discussed, especially not in the countries where power is specified not at the crank but at the wheels, as crank torque and wheel power really have very little in common. ;)
 

RayDunzl

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My new car is under-square:

Bore 87 mm
Stroke 103 mm
 
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Someone mentioned peaky 2 stroke racing bikes. Yeah those are horrible in my opinion for use on public roads, but quite the ride if you have a chance to air one out on a track.
They aren't that much different than cars with a big turbo for top end power and low compression. Super boring down low, but when the power builds, hang on! My old laggy turbo car wasn't a good daily driver, it wasn't the fastest thing out there either, but when the boost started building it FELT fast, and was a super fun weekend car.
 

JJB70

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Torque comes into its own with direct drive arrangements (i.e., no gear box) and with high starting loads (such as marine engines). As well as starting, torque is a serious limiting factor for acceleration in such arrangements.
 

W2S

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The 335D X Drive does everything I need in a car plus with new penalties for Speeding in the UK

largest fine I think is £96k as now based on your earnings

All the spec's you need

Below we present more detailed data of the factory claimed performance and the ProfessCars™ estimation, including all detailed acceleration times, with comprehensive graphic illustration, top speed, accelerations on gears, speed vs rpm and overtaking times.

https://www.automobile-catalog.com/performance/2016/2162405/bmw_335d_xdrive.html

Or Just book a test drive at your Local BMW dealer and judge for yourself
 
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Frank Dernie

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The 335D X Drive does everything I need in a car plus with new penalties for Speeding in the UK

largest fine I think is £96k as now based on your earnings

All the spec's you need

Below we present more detailed data of the factory claimed performance and the ProfessCars™ estimation, including all detailed acceleration times, with comprehensive graphic illustration, top speed, accelerations on gears, speed vs rpm and overtaking times.

https://www.automobile-catalog.com/performance/2016/2162405/bmw_335d_xdrive.html

Or Just book a test drive at your Local BMW dealer and judge for yourself
Too heavy for that small a car (IMHO of course)
 

Frank Dernie

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