Exactly! at last someone who can see the correct relationship
For the same gearing it's impossible to derive two seperate speeds for the same revolutions, they are inexorably linked, one RPM is one RPM irrespective of torque.
Wotan
Mondeo 2 Litre Zetec
- Thread starter wotan
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Exactly! at last someone who can see the correct relationship
For the same gearing it's impossible to derive two seperate speeds for the same revolutions, they are inexorably linked, one RPM is one RPM irrespective of torque.
Wotan
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thank you.
and being that i build racing car engines for a living i would like to think that its not as simple as slapping a huge stroke engine in to get the top speed.
you need a fine balance between stroke and bore.
turbos are another topic again.......
p.s. i have spent considerably longer than 4 years learning this stuff.
and being that i build racing car engines for a living i would like to think that its not as simple as slapping a huge stroke engine in to get the top speed.
you need a fine balance between stroke and bore.
turbos are another topic again.......
p.s. i have spent considerably longer than 4 years learning this stuff.
davieboy";p="850362 said:
I'm afraid you are totally missing the point, if 3000 RPM equates to 70 MPH then it matters not a jot what the stroke of the engine is.
All that is different is the efficiency of the said engine, one may be struggling to maintain the speed due to lack of torque, but a more efficient engine will cope easily and 3000 RPM will still give 70 MPH.
Wotan
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you seem to be confusing crankshaft revolutions per minute (the important factor in this equation) with relative piston velocity.
turning slower.?? no the crank still turns at the same speed. just the pistons move at different speeds depending on crank stroke and conrod length.
as i said, longer stroke generates more torque,
shorter stroke better for high rpm.
end of the day crankshaft rpm is the same.
therefore wheel speed the same.
difference is how quick it gets to given speed.
turning slower.?? no the crank still turns at the same speed. just the pistons move at different speeds depending on crank stroke and conrod length.
as i said, longer stroke generates more torque,
shorter stroke better for high rpm.
end of the day crankshaft rpm is the same.
therefore wheel speed the same.
difference is how quick it gets to given speed.
Yes we appear to be getting there
I think the confusion is trying to address engine design in terms of efficiency against the tangible effect of whatever power unit is producing the rotational force.
Crankshaft throw ie, swept volume, condod length vs stroke are immaterial, it could be a Hampster in a tread mill producing the power.
For given gearing and wheel circumference if it could mantain 3000 RPM then the speed would be 70 MPH
And all of this was because my daughter did not realise she was not in top gear!
Wotan
it seems i'm wrong!
somewhere along the line i've got mixed up with the power to maintain the speed, you live and learn!
somewhere along the line i've got mixed up with the power to maintain the speed, you live and learn!
Hi
Apology accepted.
My mistake was assuming my daughter was correct saying her car took 4,000 RPM to maintain 70 MPH in top gear, when she was only actually in fourth gear.
I test drove and found 3,000 RPM equates to 70 MPH, having said that your four years of training appear to have been wasted.
Apology accepted.
My mistake was assuming my daughter was correct saying her car took 4,000 RPM to maintain 70 MPH in top gear, when she was only actually in fourth gear.
I test drove and found 3,000 RPM equates to 70 MPH, having said that your four years of training appear to have been wasted.
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