"Dave Plowman (News)" wrote in message
...
In article ,
michael adams wrote:

"Dave Plowman (News)" wrote in message
...

Same as BHP is all important to bar room mechanics.


"Dave Plowman (News)" wrote in message
...

Please don't use 'power' as it seems to confuse so many on here. The
term is BHP - brake horse power.



And? Just what you find in that worth pasting without comment?


Your instructing me, that I should tailor my useage i.e. use BHP,
so as to pander to those very same "bar room mechanics" who you
choose to sneer at.



michael adams

....

In article ,
Fredxxx wrote:
On 09/04/2016 00:05, Dave Plowman (News) wrote:
In article ,
Fredxxx wrote:
I might agree that maximum acceleration in any gear would occur at
the maximum engine torque in that gear, the fact in itself is most
unhelpful in determining 0 to 60mph times.

And in the original discussion, 0-60 times weren't mentioned. Just the
point in an engine's output where the best acceleration occurred.
Which of course is at maximum torque, not maximum BHP.

Actual 0-60 times depends on so much more.

If you can understand the OP's question, you will accept that there are
scant details to provide an answer.

I was commenting on the assertion that torque is an irrelevance to the
acceleration of a car where 0-62mph times were mentioned. The OP's
question was something like 40 posts ago in this specific thread.

Torque still matters even for a 0-60 time, unless you were using some form
of CVT specifically designed for a very narrow band output.

Early BMW 4 valve per cylinder car engines were extremely peaky. Later
units used variable valve timing to improve the torque curve - but had no
more peak BHP. The acceleration times with the later engines were better.
And the car felt far more lively in general driving.

--
*A plateau is a high form of flattery*

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Fredxxx wrote:
On 09/04/2016 12:14, michael adams wrote:
"Dave Plowman (News)" wrote in message
...

Same as BHP is all important to bar room mechanics.


"Dave Plowman (News)" wrote in message
...

Please don't use 'power' as it seems to confuse so many on here. The
term is BHP - brake horse power.

If you want the least confusing measurement of power then use Watts, or
even KW. They are also an SI unit.

It's not commonly used in the UK for engine outputs. That is still BHP -
in the same way as we still used MPH. Although PS is creeping in. But they
can all be converted directly.

If people here don't know how to calculate power from torque and revs,
then they ought to excuse themselves from this discussion and learn.

I've been saying that for weeks. ;-)

--
*Hard work has a future payoff. Laziness pays off NOW.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
michael adams wrote:

"Dave Plowman (News)" wrote in message
...
In article ,
michael adams wrote:

"Dave Plowman (News)" wrote in message
...

Same as BHP is all important to bar room mechanics.


"Dave Plowman (News)" wrote in message
...

Please don't use 'power' as it seems to confuse so many on here. The
term is BHP - brake horse power.



And? Just what you find in that worth pasting without comment?


Your instructing me, that I should tailor my useage i.e. use BHP,
so as to pander to those very same "bar room mechanics" who you
choose to sneer at.

Sneering at those who only 'know' BHP and don't understand torque. And
therefore argue black is white.

The trouble with 'power' is it means different things to different people.

BHP is the common term in the UK for car engines. But it does need to be
used correctly.

--
*Just give me chocolate and nobody gets hurt

Dave Plowman London SW
To e-mail, change noise into sound.

On 09/04/2016 14:29, Dave Plowman (News) wrote:
In article ,
Fredxxx wrote:
On 09/04/2016 12:14, michael adams wrote:
"Dave Plowman (News)" wrote in message
...

Same as BHP is all important to bar room mechanics.


"Dave Plowman (News)" wrote in message
...

Please don't use 'power' as it seems to confuse so many on here. The
term is BHP - brake horse power.

If you want the least confusing measurement of power then use Watts, or
even KW. They are also an SI unit.

It's not commonly used in the UK for engine outputs. That is still BHP -
in the same way as we still used MPH. Although PS is creeping in. But they
can all be converted directly.

PS has been creeping out for years. It is no longer the EU "legal"
definition of power, and despite representing a German Horse Power,
German horses are less powerful than British ones so causing all the
more confusion. Perhaps the feeling they are "creeping in" is more a
reflection of the cars you buy, or for cars where power is seen as so
crucial, or even marketing where you get more PSs for your money?

kW is an international unit with no local variation, so perhaps best to
stick to that?

If people here don't know how to calculate power from torque and revs,
then they ought to excuse themselves from this discussion and learn.

I've been saying that for weeks. ;-)

Torque is irrelevant to performance. I know it's hard for you to
understand, and it doesn't agree with your prejudices, but it's true.

Try towing!

In article ,
TomSawer wrote:

Torque is irrelevant to performance. I know it's hard for you to
understand, and it doesn't agree with your prejudices, but it's true.

Try towing!

He could also try studying basic mechanics. ;-)

--
*A clear conscience is the sign of a fuzzy memory.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Fredxxx wrote:
PS has been creeping out for years. It is no longer the EU "legal"
definition of power, and despite representing a German Horse Power,
German horses are less powerful than British ones so causing all the
more confusion. Perhaps the feeling they are "creeping in" is more a
reflection of the cars you buy, or for cars where power is seen as so
crucial, or even marketing where you get more PSs for your money?

kW is an international unit with no local variation, so perhaps best to
stick to that?

It's like many things. One tends to stick to units you are familiar with -
unless for professional reasons. Same way as many still give a person's
height in feet. Know the price of a pint of milk. And so on.

--
*I must always remember that I'm unique, just like everyone else. *

Dave Plowman London SW
To e-mail, change noise into sound.

On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to oranges.


The fact remains that a car's power to weight ratio (*not* engine torque
to weight ratio) is a pretty good indicator of accelerative performance.

It's an oft quoted figure for the masses. Same as BHP is all important to
bar room mechanics. But it doesn't tell the full story. Only that car
makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

But I'll ask you a question. Take a high revving bike engine with a very
high specific BHP per litre and put it up against a lightly stressed but
torquey V8 etc in vehicles with the same power to weight ratio. Which one
will accelerate better?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Sat, 09 Apr 2016 17:38:45 +0100, Roger Mills wrote:

On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to
oranges.


The fact remains that a car's power to weight ratio (*not* engine
torque to weight ratio) is a pretty good indicator of accelerative
performance.

It's an oft quoted figure for the masses. Same as BHP is all important
to bar room mechanics. But it doesn't tell the full story. Only that
car makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

But I'll ask you a question. Take a high revving bike engine with a
very high specific BHP per litre and put it up against a lightly
stressed but torquey V8 etc in vehicles with the same power to weight
ratio. Which one will accelerate better?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.

It depends on the amounts of inertia in the engines relative to the
whole vehicle's inertia. The typical diesel equivalent to its petrol
counterpart will have more inertia, reducing the overall acceleration
performance despite providing the same top speed performance. This
assumes the overall mass of the vehicles remain identical. In practice,
the diesel variant tends to weigh a few pounds more than its petrol
engined counterpart.

Of course, the ratios available in the gearbox along with clutch
technique used when maximising acceleration performance will modify this,
with full throttle change up and abuse of of the clutch even reversing
this trend. An automatic box with continuously variable ratio configured
to allow the engine to run at its peak BHP revs will eliminate such a
difference.

--
Johnny B Good

On Friday, 8 April 2016 23:24:06 UTC+1, Roger Mills wrote:
For
maximum accelerative performance you need the maximum available
acceleration all the way up the speed range - so you need to run the
engine as close to max power as possible.

You still can't grasp that "Full Throttle" does NOT equate to "Full Power"; it only equates to "Full Power" at Full Power" engine RPMs. Which means that you cannot accelerate AT "Full Power"; you can only accelerate UP TO "Full Power"

In article ,
Roger Mills wrote:
It's an oft quoted figure for the masses. Same as BHP is all important to
bar room mechanics. But it doesn't tell the full story. Only that car
makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

Well yes. Since most makers aim for the same sort of engine output curve.

But I'll ask you a question. Take a high revving bike engine with a
very high specific BHP per litre and put it up against a lightly
stressed but torquey V8 etc in vehicles with the same power to weight
ratio. Which one will accelerate better?


Why compare a bike engine with V8 car engine?

Because you've singled out power to weight as some sort of benchmark. And
it would be easy enough to find a small capacity high revving bike engine
with the same sort of peak BHP as a lazy V8. Put them in vehicles so the
power to weight ratio is the same, and see which one accelerates faster.
It will be the one with the flatter torque curve.

--
*How do they get the deer to cross at that yellow road sign?

Dave Plowman London SW
To e-mail, change noise into sound.

On 09/04/2016 17:38, Roger Mills wrote:
On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to oranges.


The fact remains that a car's power to weight ratio (*not* engine torque
to weight ratio) is a pretty good indicator of accelerative performance.

It's an oft quoted figure for the masses. Same as BHP is all important to
bar room mechanics. But it doesn't tell the full story. Only that car
makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

But I'll ask you a question. Take a high revving bike engine with a very
high specific BHP per litre and put it up against a lightly stressed but
torquey V8 etc in vehicles with the same power to weight ratio. Which one
will accelerate better?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.

I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

On 09/04/2016 16:51, TomSawer wrote:

Torque is irrelevant to performance. I know it's hard for you to
understand, and it doesn't agree with your prejudices, but it's true.

Try towing!

Are you suggesting that it isn't power that accelerates a car and towed
trailer to a desired speed?

If you regard torque as the single indicator of performance, you have a
strange sense of performance.

On 09/04/16 19:15, Fredxxx wrote:
Most modern diesel engines seem to produce near constant power over a
very large range of revs.

No they dont. Perhaps more constant torque, but not power

e.g.


https://www.bmw.co.uk/dam/brandBM/co...3896735380.jpg

Torque flat to 3000, then tails away to peak power at 4500.


--
New Socialism consists essentially in being seen to have your heart in
the right place whilst your head is in the clouds and your hand is in
someone else's pocket.

On 09/04/2016 18:02, Johnny B Good wrote:
On Sat, 09 Apr 2016 17:38:45 +0100, Roger Mills wrote:

On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to
oranges.


The fact remains that a car's power to weight ratio (*not* engine
torque to weight ratio) is a pretty good indicator of accelerative
performance.

It's an oft quoted figure for the masses. Same as BHP is all important
to bar room mechanics. But it doesn't tell the full story. Only that
car makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

But I'll ask you a question. Take a high revving bike engine with a
very high specific BHP per litre and put it up against a lightly
stressed but torquey V8 etc in vehicles with the same power to weight
ratio. Which one will accelerate better?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.

It depends on the amounts of inertia in the engines relative to the
whole vehicle's inertia. The typical diesel equivalent to its petrol
counterpart will have more inertia, reducing the overall acceleration
performance despite providing the same top speed performance. This
assumes the overall mass of the vehicles remain identical. In practice,
the diesel variant tends to weigh a few pounds more than its petrol
engined counterpart.


I mentioned in an earlier post that you needed to consider the effective
mass of the engine in each gear and add it to the vehicle mass when
calculating acceleration. The diesel engine will have a higher moment of
inertia in absolute terms, but the diesel car will be higher geared - so
the 'effective' mass of the engine probably won't be any greater than
that of the petrol. [And no, I don't have any specific figures in order
to verify that, but that is my hunch.]
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 09/04/2016 18:40, Dave Plowman (News) wrote:
In ,
Roger wrote:

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

Well yes. Since most makers aim for the same sort of engine output curve.

Well, it seemed to apply to everything from a Fiat 500 to a V12 Jaguar.

But I'll ask you a question. Take a high revving bike engine with a
very high specific BHP per litre and put it up against a lightly
stressed but torquey V8 etc in vehicles with the same power to weight
ratio. Which one will accelerate better?


Why compare a bike engine with V8 car engine?

Because you've singled out power to weight as some sort of benchmark. And
it would be easy enough to find a small capacity high revving bike engine
with the same sort of peak BHP as a lazy V8. Put them in vehicles so the
power to weight ratio is the same, and see which one accelerates faster.
It will be the one with the flatter torque curve.

It's not a practical thing to do - and you'd *have* to do it to prove
whether or not your statement is true.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 09/04/2016 19:15, Fredxxx wrote:
On 09/04/2016 17:38, Roger Mills wrote:
On 09/04/2016 11:42, Dave Plowman (News) wrote:
In ,
Roger wrote:
What any car's 0-60 time may be is totally irrelevant to where the
maximum acceleration occurs anyway. Unless comparing apples to
oranges.


The fact remains that a car's power to weight ratio (*not* engine
torque
to weight ratio) is a pretty good indicator of accelerative
performance.

It's an oft quoted figure for the masses. Same as BHP is all
important to
bar room mechanics. But it doesn't tell the full story. Only that car
makers tend to produce roughly similar engines.

A colleague of mine at Rover studied this is some detail, and plotted a
graph of 0 - 30 times (admittedly not 0 - 60) against power to weight
ratio for a wide range of vehicles. He found a very strong correlation.

But I'll ask you a question. Take a high revving bike engine with a very
high specific BHP per litre and put it up against a lightly stressed but
torquey V8 etc in vehicles with the same power to weight ratio. Which
one
will accelerate better?


Why compare a bike engine with V8 car engine?

If you take the same car and equip it with a high revving petrol engine,
and then swap the engine for diesel which produces the same power but at
a lower speed (with a suitable matching gearbox in each case) there will
be very little difference in the accelerative performance - even though
the level of drama may be different.

I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

I'm not comparing it with a bike engine - that was Dave's idea!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 09/04/2016 18:24, wrote:
On Friday, 8 April 2016 23:24:06 UTC+1, Roger Mills wrote:
For
maximum accelerative performance you need the maximum available
acceleration all the way up the speed range - so you need to run the
engine as close to max power as possible.

You still can't grasp that "Full Throttle" does NOT equate to "Full Power"; it only equates to "Full Power" at Full Power" engine RPMs. Which means that you cannot accelerate AT "Full Power"; you can only accelerate UP TO "Full Power"

But you haven't read what I wrote! I have never once asserted that full
throttle equates to full power under all conditions - it clearly doesn't
- just look at an engine power curve, showing that max power only occurs
at one specific engine speed.

What I actually said was that you needed to run the engine as close to
max power as possible. Naturally *how* close to max power you can keep
it as the car accelerates depends on how many gears you've got, and how
they're spaced.

As I have said before, if you had a continuously variable transmission
rather than a stepped gearbox, you *could* actually hold the engine at
max power and continuously change the ratios to match the road speed.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

wrote in message
...

Which means that you cannot accelerate AT "Full Power"; you can
only accelerate UP TO "Full Power"

So you stick the pedal to the metal at 40mph - full power
and the car doesn't accelerate any further.

On Saturday, 9 April 2016 20:56:48 UTC+1, Roger Mills wrote:
On 09/04/2016 18:24, wrote:
On Friday, 8 April 2016 23:24:06 UTC+1, Roger Mills wrote:
For
maximum accelerative performance you need the maximum available
acceleration all the way up the speed range - so you need to run the
engine as close to max power as possible.

You still can't grasp that "Full Throttle" does NOT equate to "Full Power"; it only equates to "Full Power" at Full Power" engine RPMs. Which means that you cannot accelerate AT "Full Power"; you can only accelerate UP TO "Full Power"

But you haven't read what I wrote! I have never once asserted that full
throttle equates to full power under all conditions - it clearly doesn't
- just look at an engine power curve, showing that max power only occurs
at one specific engine speed.

What I actually said was that you needed to run the engine as close to
max power as possible. Naturally *how* close to max power you can keep
it as the car accelerates depends on how many gears you've got, and how
they're spaced.

As I have said before, if you had a continuously variable transmission
rather than a stepped gearbox, you *could* actually hold the engine at
max power and continuously change the ratios to match the road speed.
--
Cheers,
Roger

I've read everything that you written on this thread. All through it you've been using the words "Max Power" when you should have used the words "Full Throttle".
The confusion is your fault.
Now go and stick your head up a dead bear's bum.

On 09/04/2016 21:59, wrote:
On Saturday, 9 April 2016 20:56:48 UTC+1, Roger Mills wrote:
On 09/04/2016 18:24, wrote:
On Friday, 8 April 2016 23:24:06 UTC+1, Roger Mills wrote:
For
maximum accelerative performance you need the maximum available
acceleration all the way up the speed range - so you need to run the
engine as close to max power as possible.

You still can't grasp that "Full Throttle" does NOT equate to "Full Power"; it only equates to "Full Power" at Full Power" engine RPMs. Which means that you cannot accelerate AT "Full Power"; you can only accelerate UP TO "Full Power"

But you haven't read what I wrote! I have never once asserted that full
throttle equates to full power under all conditions - it clearly doesn't
- just look at an engine power curve, showing that max power only occurs
at one specific engine speed.

What I actually said was that you needed to run the engine as close to
max power as possible. Naturally *how* close to max power you can keep
it as the car accelerates depends on how many gears you've got, and how
they're spaced.

As I have said before, if you had a continuously variable transmission
rather than a stepped gearbox, you *could* actually hold the engine at
max power and continuously change the ratios to match the road speed.


I've read everything that you written on this thread. All through it you've been using the words "Max Power" when you should have used the words "Full Throttle".
The confusion is your fault.

You are the only one who's confused!

Whenever I've referred to max power I've meant just that - namely
operating the engine at full throttle at the speed at which it produces
its maximum power.

Now go and stick your head up a dead bear's bum.

That's nice and friendly! How about trying to have a civilised discussion?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Fredxxx wrote:
I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

See what I mean about the misuse of 'power'?

--
*My luck is so bad that if I bought a cemetery, people would stop dying.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Roger Mills wrote:
Because you've singled out power to weight as some sort of benchmark.
And it would be easy enough to find a small capacity high revving bike
engine with the same sort of peak BHP as a lazy V8. Put them in
vehicles so the power to weight ratio is the same, and see which one
accelerates faster. It will be the one with the flatter torque curve.

It's not a practical thing to do - and you'd *have* to do it to prove
whether or not your statement is true.

Actually, quite easy to do.

But are you then saying power to weight isn't the be all and end all of
acceleration?

--
*How does Moses make his tea? Hebrews it.*

Dave Plowman London SW
To e-mail, change noise into sound.

On 10/04/2016 00:33, Dave Plowman (News) wrote:
In ,
wrote:
I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

See what I mean about the misuse of 'power'?


That's not a misuse of power - it's just an error of fact!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 10/04/2016 00:35, Dave Plowman (News) wrote:
In ,
Roger wrote:
Because you've singled out power to weight as some sort of benchmark.
And it would be easy enough to find a small capacity high revving bike
engine with the same sort of peak BHP as a lazy V8. Put them in
vehicles so the power to weight ratio is the same, and see which one
accelerates faster. It will be the one with the flatter torque curve.

It's not a practical thing to do - and you'd *have* to do it to prove
whether or not your statement is true.

Actually, quite easy to do.

I think you might have some difficulty trying to install a bile engine
in a car!

But are you then saying power to weight isn't the be all and end all of
acceleration?


I'm saying that it's the most significant factor. I would expect a
diesel car to perform similarly to a petrol car with the same power to
weight ratio - as indicated by the figures which someone quoted to other
day.

But when you start comparing apples with pears by speculating about
putting a bike engine in a car, you are shifting the goalposts more than
somewhat. Your hypothetical bike engine probably wouldn't do so well
because you wouldn't to able to deliver near maximum power - and I
stress the word *power* - to the wheels for as large a proportion of the
time.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Saturday, 9 April 2016 22:08:28 UTC+1, Roger Mills wrote:
On 09/04/2016 21:59, wrote:
On Saturday, 9 April 2016 20:56:48 UTC+1, Roger Mills wrote:
On 09/04/2016 18:24, wrote:
On Friday, 8 April 2016 23:24:06 UTC+1, Roger Mills wrote:
For
maximum accelerative performance you need the maximum available
acceleration all the way up the speed range - so you need to run the
engine as close to max power as possible.

You still can't grasp that "Full Throttle" does NOT equate to "Full Power"; it only equates to "Full Power" at Full Power" engine RPMs. Which means that you cannot accelerate AT "Full Power"; you can only accelerate UP TO "Full Power"

But you haven't read what I wrote! I have never once asserted that full
throttle equates to full power under all conditions - it clearly doesn't
- just look at an engine power curve, showing that max power only occurs
at one specific engine speed.

What I actually said was that you needed to run the engine as close to
max power as possible. Naturally *how* close to max power you can keep
it as the car accelerates depends on how many gears you've got, and how
they're spaced.

As I have said before, if you had a continuously variable transmission
rather than a stepped gearbox, you *could* actually hold the engine at
max power and continuously change the ratios to match the road speed.


I've read everything that you written on this thread. All through it you've been using the words "Max Power" when you should have used the words "Full Throttle".
The confusion is your fault.

You are the only one who's confused!

Whenever I've referred to max power I've meant just that - namely
operating the engine at full throttle at the speed at which it produces
its maximum power.

Now go and stick your head up a dead bear's bum.

That's nice and friendly! How about trying to have a civilised discussion?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

How about examining the facts and admitting that you're wrong. An egine develops full power at one speed only. Now weasel out of that.

In article ,
Roger Mills wrote:
On 10/04/2016 00:33, Dave Plowman (News) wrote:
In ,
wrote:
I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

See what I mean about the misuse of 'power'?


That's not a misuse of power - it's just an error of fact!

Could be either. But it does prove the point I made earlier. Power can be
a general expression used which may be perfectly well understood in a
context. But not when discussing the difference between power and torque.

--
*A bicycle can't stand alone because it's two tyred.*

Dave Plowman London SW
To e-mail, change noise into sound.

On Sunday, 10 April 2016 09:48:31 UTC+1, Roger Mills wrote:

I think you might have some difficulty trying to install a bike engine
in a car!


You're not really "into" cars and motoring. are you?

In article ,
Roger Mills wrote:
On 10/04/2016 00:35, Dave Plowman (News) wrote:
In ,
Roger wrote:
Because you've singled out power to weight as some sort of benchmark.
And it would be easy enough to find a small capacity high revving bike
engine with the same sort of peak BHP as a lazy V8. Put them in
vehicles so the power to weight ratio is the same, and see which one
accelerates faster. It will be the one with the flatter torque curve.

It's not a practical thing to do - and you'd *have* to do it to prove
whether or not your statement is true.

Actually, quite easy to do.

I think you might have some difficulty trying to install a bile engine
in a car!

Really? There are several around. Although more what you'd call sports
cars.

But are you then saying power to weight isn't the be all and end all of
acceleration?


I'm saying that it's the most significant factor. I would expect a
diesel car to perform similarly to a petrol car with the same power to
weight ratio - as indicated by the figures which someone quoted to other
day.

They may have a similar 0-60 time or whatever, but how they perform in a
single gear is likely very different. The very point I was making about
torque versus power.

But when you start comparing apples with pears by speculating about
putting a bike engine in a car, you are shifting the goalposts more than
somewhat. Your hypothetical bike engine probably wouldn't do so well
because you wouldn't to able to deliver near maximum power - and I
stress the word *power* - to the wheels for as large a proportion of the
time.

I was merely commenting on power to weight ratio. That may be a reasonable
guide to performance where the engines are similar. But doesn't take into
account how the vehicle will perform in a single gear if the engine type
varies wildly. For that, you need to know about the torque output of the
engine.

--
*Could it be that "I do " is the longest sentence? *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
wrote:
On Sunday, 10 April 2016 09:48:31 UTC+1, Roger Mills wrote:

I think you might have some difficulty trying to install a bike engine
in a car!


You're not really "into" cars and motoring. are you?

Seems to apply to an awful lot on here. Doesn't stop them thinking they
are, though.

--
*You can't teach an old mouse new clicks *

Dave Plowman London SW
To e-mail, change noise into sound.

On 10/04/2016 11:40, wrote:



How about examining the facts and admitting that you're wrong. An egine develops full power at one speed only. Now weasel out of that.

No need to. I've never said anything which is inconsistent with that. I
can only assume that you've *mis*-read all my posts on the subject!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article , Vir
Campestris writes
It's true that if you can't change gear you'll get the highest
acceleration at peak torque.
Isn't that where we started?
--
bert

On 09/04/2016 19:20, The Natural Philosopher wrote:
On 09/04/16 19:15, Fredxxx wrote:
Most modern diesel engines seem to produce near constant power over a
very large range of revs.

No they dont. Perhaps more constant torque, but not power

e.g.


https://www.bmw.co.uk/dam/brandBM/co...3896735380.jpg


Torque flat to 3000, then tails away to peak power at 4500.


OK - I was thinking of turbo-diesels.

On 10/04/2016 22:45, bert wrote:
In article , Vir
Campestris writes
It's true that if you can't change gear you'll get the highest
acceleration at peak torque.
Isn't that where we started?

Yes, but didn't we start in ignorance of the gear?

On 09/04/2016 19:15, Fredxxx wrote:

I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

A lot of modern diesels have a flat torque curve. Not a flat power curve.

The few I've driven feel as if the power band is horribly narrow
compared to my car - which has peak torque at 4800...

Andy

On 10/04/2016 00:33, Dave Plowman (News) wrote:
In article ,
Fredxxx wrote:
I doubt it. Most modern diesel engines seem to produce near constant
power over a very large range of revs. Bike engines don't.

See what I mean about the misuse of 'power'?

Power corrupts, absolute power corrupts absolutely :P

Andy