In article ,
Clive George wrote:
The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

No. Vir Campestris started it again after say the same as many on here
seem to think. That an engine accelerates at its best at peak BHP. But was
wrong before and is wrong now.

--
*A day without sunshine is like... night.*

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

In article ,
Clive George wrote:
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about
2000 rpm and max power at about 3500 rpm. Going up the gears and
accelerating as fast as I could I never got anywhere near max power in
any gear before I could feel the acceleration dropping off.

But did changing to a higher gear result in faster acceleration?

Only an idiot would think it would. Unless you were way beyond the peak
BHP in the low gear. Which few engines would allow anyway.

Does it come as surprise to you that changing up results in less torque at
the rear wheels? And it's the maximum torque which produces the best
acceleration. ;-)

--
*IF A PARSLEY FARMER IS SUED, CAN THEY GARNISH HIS WAGES?

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

In article ,
newshound wrote:
Power, revs, and torque are inextricably linked but I think that most
mechanical engineers who go back to the basics think of it being the
torque which provides the mechanical force at the wheels (and hence the
acceleration).

I've been trying to get that point across for some weeks now. But it is
obviously beyond many. ;-)

--
*If a pig loses its voice, is it disgruntled? *

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

In article ,
Clive George wrote:
That's all there is. The available torque at various RPM is of course
unknown, depending on the engine itself.

Peak torque is always at lower RPM than peak BHP.

--
*Money isn't everything, but it sure keeps the kids in touch.

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

On 31/03/2016 16:59, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about
2000 rpm and max power at about 3500 rpm. Going up the gears and
accelerating as fast as I could I never got anywhere near max power in
any gear before I could feel the acceleration dropping off.

But did changing to a higher gear result in faster acceleration?

Only an idiot would think it would.

I agree. So to make the car go the fastest, even though you can feel the
acceleration dropping off, it's still worth staying in the lower gear
past peak power. Ie aiming for peak power where possible, same as I've
been saying for quite a long time.

Unless you were way beyond the peak
BHP in the low gear. Which few engines would allow anyway.

Does it come as surprise to you that changing up results in less torque at
the rear wheels? And it's the maximum torque which produces the best
acceleration. ;-)

Funnily enough I've been arguing that for quite a long time...

On 31/03/2016 17:03, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
That's all there is. The available torque at various RPM is of course
unknown, depending on the engine itself.

Peak torque is always at lower RPM than peak BHP.

It has to be :-)

In article ,
Clive George wrote:
Only an idiot would think it would.

I agree. So to make the car go the fastest, even though you can feel the
acceleration dropping off, it's still worth staying in the lower gear
past peak power. Ie aiming for peak power where possible, same as I've
been saying for quite a long time.

It's rather irrelevant, but with a decent set of ratios, you'd change up
around peak BHP and plonk things close to the peak torque in the next
higher gear. Unless you just like making a lot of noise and wasting fuel,
of course.

Unless you were way beyond the peak BHP in the low gear. Which few
engines would allow anyway.

Does it come as surprise to you that changing up results in less
torque at the rear wheels? And it's the maximum torque which produces
the best acceleration. ;-)

Funnily enough I've been arguing that for quite a long time...

Then why do you keep on mentioning BHP?

--
*A 'jiffy' is an actual unit of time for 1/100th of a second.

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

In article ,
Clive George wrote:
On 31/03/2016 17:03, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
That's all there is. The available torque at various RPM is of course
unknown, depending on the engine itself.

Peak torque is always at lower RPM than peak BHP.

It has to be :-)

Just waiting for Turnip to come along and disagree. ;-)

--
*The more people I meet, the more I like my dog.

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

In article , Clive
George writes
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

But did changing to a higher gear result in faster acceleration?


Faster compared to what?
--
bert

On 31/03/2016 18:05, bert wrote:
In article , Clive
George writes
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

But did changing to a higher gear result in faster acceleration?


Faster compared to what?

Compared to being in the lower gear.

(the answer I'd expect would be "no", hence even though you're feeling
the acceleration drop off, it's still worth staying in the lower gear
and using max power if you want to carry on accelerating as fast as
possible)

On 31/03/2016 16:54, Dave Plowman (News) wrote:
In article3qadnR0KFvKhqGDLnZ2dnUU78b2dnZ2d@brightvie w.co.uk,


To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

No. Vir Campestris started it again after say the same as many on here
seem to think. That an engine accelerates at its best at peak BHP. But was
wrong before and is wrong now.

I'm beginning to lose the will to live!

Yesterday, you you agreed with my two propositions. Please re-read the
second one and then explain why you are contradicting yourself by what
you are now saying.

Supposing that you had an infinitely variable transmission (with an
upper and lower limit, of course) and could program it to maintain the
engine speed constant as the car accelerated. If I understand you
correctly, you would argue that in order to maximise acceleration, you
would need to hold the engine at its max torque speed. Most other people
here would say that was nonsense, because you could get more power to
the wheels - and hence acceleration - by running the engine at its
maximum power speed instead. So where do you stand on this?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 31/03/2016 14:31, Dave Plowman (News) wrote:
In ,
Roger wrote:
Indeed. If you want to accelerate the car as fast as possible, you need
to maximise the power available at the wheels. This invariably means
taking the engine up to at least its maximum power speed before changing
up to the next gear. I say "at least" because quite often - unless you
have lots of closely spaced gears - you still get more acceleration in
the gear you're in by keeping going beyond max power speed until you run
our of revs than by changing to the next gear which drops you a long way
back down the power curve.

And idea set of gearbox ratios would allow you to change up round about
peak BHP and the next higher gear would plonk you at near enough maximum
torque...


Yes, it would. But you'd still have less thrust at the wheels because of
the higher gearing.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 31/03/2016 15:39, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed.
No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed and
the engine's maximum power speed.

Yes or no please - no equivocation!
I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

That's what you'd expect. The torque - and hence the acceleration in
that gear drops off. But it will almost certainly drop even more when
you change to the next gear up even though the engine is producing more
torque.

Next time, take an accelerometer with you, and tell us what happens in
the higher gear.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 31/03/2016 16:59, Dave Plowman (News) wrote:
In articlea9ydnS6TQ4n_oWDLnZ2dnUU78XPNnZ2d@brightvie w.co.uk,
Clive wrote:
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about
2000 rpm and max power at about 3500 rpm. Going up the gears and
accelerating as fast as I could I never got anywhere near max power in
any gear before I could feel the acceleration dropping off.

But did changing to a higher gear result in faster acceleration?

Only an idiot would think it would. Unless you were way beyond the peak
BHP in the low gear. Which few engines would allow anyway.

Does it come as surprise to you that changing up results in less torque at
the rear wheels? And it's the maximum torque which produces the best
acceleration. ;-)


IN A GIVEN GEAR. I've come to the conclusion that you're trying to view
a 3-dimensional problem in 2 dimensions!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 30/03/2016 23:01, newshound wrote:

Not convinced. Peak power is certainly the place of max speed, I would
have said that peak torque is the place of max acceleration.

fx looks up

I did the math earlier. Peak power is at higher revs, so you can use a
lower gear. This means that the torque at the output of the gearbox is
higher at peak torque.

Like this:

2000 RPM, 400nM, geared down 2:1 to 1000 RPM gives you 400nM.
5000 RPM, 200nM, geared down 5:1 to 1000 RPM gives you 1000nM.

Dave refuses to admit that this means you get better acceleration at
peak power than at peak torque.

The only exception is when you are in 1st gear and cannot change down.

Andy

On 30/03/2016 23:16, Roger Mills wrote:
OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes or no please - no equivocation!

Yes.

(Well - almost. You want the gear that gives you the highest possible
power output for that road speed. It's not likely to be exactly peak
except for CVTs.)

Andy

On 31/03/16 15:39, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed.
No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed and
the engine's maximum power speed.

Yes or no please - no equivocation!
I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

That is not the ****ing point, The point is whether or not changing up
to the next gear and dropping the revs lost even MORE acceleration.


--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 31/03/16 16:15, newshound wrote:
On 3/31/2016 3:33 PM, Clive George wrote:
On 31/03/2016 14:25, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 01:22, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
On 31/03/2016 00:43, Dave Plowman (News) wrote:



I
won't disagree with that, but don't think it's terribly useful, because
generally people are concerned with the fastest way of getting between
two road speeds (eg 20-60). And for that, the fastest way is to choose
the gear such that the engine is at or closest to maximum power, not
maximum torque. Ie change up late, not early.

The discussion was about where on the *engine's* output maximum
acceleration occurs. Not about achieving the best 0-60 mph or anything
else.

To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

To you it seems to be only about at which point when you're racing from
0 to whatever are you accelerating fastest - which I agree is max torque
in first gear.

Is that an adequate summary of the two positions?

Peak power revs is normally a point where your acceleration is dropping
right off.

No, it isn't. Its probably past peak torque for most rad car engines,
but not that far past ot.

For the best 0-60, standing quarter, or whatever you would
normally change up before you reach peak power

No, you would change up *after* you reached it.

(as long as you have
another gear available). You change up somewhere beyond peak torque so
that in the next gear you are going back through the torque peak again.
Exactly where you change is also partly determined by how much time you
lose in the gearchange; you might decide to start in second if you have
a low first ratio, or to reduce wheelspin. If you are drag racing in a
Landy you probably would not use low ratios!

You are in fact confusing torque with power.


Power, revs, and torque are inextricably linked but I think that most
mechanical engineers who go back to the basics think of it being the
torque which provides the mechanical force at the wheels (and hence the
acceleration).

No, they dont. Not is the confused and simplistic way that you do.


--
"In our post-modern world, climate science is not powerful because it is
true: it is true because it is powerful."

Lucas Bergkamp

On 31/03/16 17:08, Clive George wrote:
On 31/03/2016 17:03, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
That's all there is. The available torque at various RPM is of course
unknown, depending on the engine itself.

Peak torque is always at lower RPM than peak BHP.

It has to be :-)


No, in fact it doesn't.

But it would be a weird sort of engine where it wasn't

Some engines can be made to deliver both at the same point. At the point
where the engine is revving itself to imminent destruction.

I agree peak torque can't be BEYOND peak BHP in rev terms. ;-)

--
Karl Marx said religion is the opium of the people.
But Marxism is the crack cocaine.

On 31/03/16 18:54, Roger Mills wrote:
On 31/03/2016 16:54, Dave Plowman (News) wrote:
In article3qadnR0KFvKhqGDLnZ2dnUU78b2dnZ2d@brightvie w.co.uk,


To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

No. Vir Campestris started it again after say the same as many on here
seem to think. That an engine accelerates at its best at peak BHP. But
was
wrong before and is wrong now.

I'm beginning to lose the will to live!


Notice how he has changed the goalposts "That an *engine* accelerates at
its best at peak BHP".

That is of course incorrect, but we are not talking about the engine, we
are talking about the *CAR*. Which includes a gear box.



--
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 31/03/16 18:56, Roger Mills wrote:
On 31/03/2016 14:31, Dave Plowman (News) wrote:
In ,
Roger wrote:
Indeed. If you want to accelerate the car as fast as possible, you need
to maximise the power available at the wheels. This invariably means
taking the engine up to at least its maximum power speed before changing
up to the next gear. I say "at least" because quite often - unless you
have lots of closely spaced gears - you still get more acceleration in
the gear you're in by keeping going beyond max power speed until you run
our of revs than by changing to the next gear which drops you a long way
back down the power curve.

And idea set of gearbox ratios would allow you to change up round about
peak BHP and the next higher gear would plonk you at near enough maximum
torque...


Yes, it would. But you'd still have less thrust at the wheels because of
the higher gearing.

The optimal point to change up is beyond peak bhp, such that at the road
speed the car is doing, the BHP that results after you have changed up
is less than peak bhp by the same amount as the bhp when you changed up,
was before. That keeps the average BHP as high as possible, and thus the
overall acceleration as high as possible.

If BHP doesn't make cars accelerate why the **** do we bother with it,
since a million to one gearbox on an elastic band will give you more
torque than a formula one car engine.


--
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 31/03/16 19:03, Roger Mills wrote:
On 31/03/2016 16:59, Dave Plowman (News) wrote:
In articlea9ydnS6TQ4n_oWDLnZ2dnUU78XPNnZ2d@brightvie w.co.uk,
Clive wrote:
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about
2000 rpm and max power at about 3500 rpm. Going up the gears and
accelerating as fast as I could I never got anywhere near max power in
any gear before I could feel the acceleration dropping off.

But did changing to a higher gear result in faster acceleration?

Only an idiot would think it would. Unless you were way beyond the peak
BHP in the low gear. Which few engines would allow anyway.

Does it come as surprise to you that changing up results in less
torque at
the rear wheels? And it's the maximum torque which produces the best
acceleration. ;-)


IN A GIVEN GEAR. I've come to the conclusion that you're trying to view
a 3-dimensional problem in 2 dimensions!

Leftybrain thinking is like that. Its the curse of the
almost-intelligent. Thinking you understand what you actually don't.

--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

On 31/03/2016 00:42, Dave Plowman (News) wrote:
In article ,
Roger Mills wrote:
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed. No vehicle with an IC engine gives a linear rate of increase in
speed from 0 to top speed. It will obviously produce the best
acceleration in the lowest gear, slightly less in the next one up, and
so on. But that is a red herring as regards when the engine produces
the best acceleration in any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

Yes.

At a given road speed, the maximum rate of change of road speed will be
achieved at the engine's maximum power point. The necessary gear ratio
to achieve this will be determined by the chosen road speed and the
engine's maximum power speed.

Yes. Assuming you have a gear which allows that road speed at maximum BHP.
That would by nature be a lower gear than one which place the engine at
peak torque at that road speed. And a lower gear multiples the torque.

Yes or no please - no equivocation!

Doesn't need any equivocation. Of course a lower gear multiplies the
engine's torque.

At last he gets it right.

Any more argument must be just trolling.

Andy

On 31/03/2016 16:15, newshound wrote:
You change up somewhere beyond peak torque so that in the next gear you
are going back through the torque peak again.

Substitute torque for power and that is exactly right.

Andy

In article ,
Roger Mills wrote:
On 31/03/2016 16:54, Dave Plowman (News) wrote:
In article3qadnR0KFvKhqGDLnZ2dnUU78b2dnZ2d@brightvie w.co.uk,


To most of the people in this discussion, the discussion is about how
to achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to
maximum power as you can, not maximum engine torque.

No. Vir Campestris started it again after say the same as many on here
seem to think. That an engine accelerates at its best at peak BHP. But
was wrong before and is wrong now.

I'm beginning to lose the will to live!

Yesterday, you you agreed with my two propositions. Please re-read the
second one and then explain why you are contradicting yourself by what
you are now saying.

In your second point you specified a road speed that coincided with
maximum BHP. Therefore it would be impossible to be at the same speed in
the same gear and at maximum torque. But perhaps you meant something else?

--
*Kill one man and you're a murderer, kill a million youand 're a conqueror.

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

In article ,
Vir Campestris wrote:
On 30/03/2016 23:01, newshound wrote:

Not convinced. Peak power is certainly the place of max speed, I would
have said that peak torque is the place of max acceleration.

fx looks up

I did the math earlier. Peak power is at higher revs, so you can use a
lower gear. This means that the torque at the output of the gearbox is
higher at peak torque.

Like this:

2000 RPM, 400nM, geared down 2:1 to 1000 RPM gives you 400nM.
5000 RPM, 200nM, geared down 5:1 to 1000 RPM gives you 1000nM.

Dave refuses to admit that this means you get better acceleration at
peak power than at peak torque.

And you don't seem to realise that using a different gear for each example
simply confuses the issue.

The only exception is when you are in 1st gear and cannot change down.

Which is were we came in. I was talking about accleration *in any one gear*

How often do I have to say it?

--
*How come you never hear about gruntled employees? *

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

In article ,
The Natural Philosopher wrote:
That is not the ****ing point, The point is whether or not changing up
to the next gear and dropping the revs lost even MORE acceleration.

That may be your point, but was never mine. No surprise as you never read
stuff properly anyway.

--
*WOULD A FLY WITHOUT WINGS BE CALLED A WALK?

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

In article ,
The Natural Philosopher wrote:
Peak power revs is normally a point where your acceleration is dropping
right off.

No, it isn't. Its probably past peak torque for most rad car engines,
but not that far past ot.

Right. So according to you you get peak accleration at peak BHP, and the
same acceleration as the BHP drops off above that?

Forget reading what others say. Try reading what you do.

--
*i souport publik edekashun.

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

In article ,
The Natural Philosopher wrote:
On 31/03/16 18:54, Roger Mills wrote:
On 31/03/2016 16:54, Dave Plowman (News) wrote:
In article3qadnR0KFvKhqGDLnZ2dnUU78b2dnZ2d@brightvie w.co.uk,


To most of the people in this discussion, the discussion is about how to
achieve maximum acceleration during normal (or rather 'spirited')
driving, at whatever start and end speed the situation requires - and
the answer to that is to choose the right gear to get as near to maximum
power as you can, not maximum engine torque.

No. Vir Campestris started it again after say the same as many on here
seem to think. That an engine accelerates at its best at peak BHP. But
was
wrong before and is wrong now.

I'm beginning to lose the will to live!


Notice how he has changed the goalposts "That an *engine* accelerates at
its best at peak BHP".

FFS. Please read the posts you've quoted.

That is of course incorrect, but we are not talking about the engine, we
are talking about the *CAR*. Which includes a gear box.

I'm only talking about the engine. Introducing different gearing simply
confuses the issue.

--
*If they arrest the Energizer Bunny, would they charge it with battery? *

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

On 01/04/2016 00:29, Dave Plowman (News) wrote:


Which is were we came in. I was talking about accleration *in any one gear*

How often do I have to say it?


No-one disagrees with you that max acceleration in any one gear occurs
at the engine's max torque point.

But you seem to be fixated on that point and unable to accept that, at
the corresponding road speed, you can get *greater* acceleration by
using a lower gear and running the engine near to its max power point.

BHP at the wheels = thrust (lbs) x speed (mph) / 375

OR Thrust = BHP x 375 / speed

So it stands to reason that the more power you can get to the wheels at
a given speed, the greater the thrust and hence acceleration. QED!

I note that you haven't commented on my post about using a continuously
variable transmission to maintain a constant engine speed!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

In article ,
Roger Mills wrote:
On 01/04/2016 00:29, Dave Plowman (News) wrote:


Which is were we came in. I was talking about accleration *in any one gear*

How often do I have to say it?


No-one disagrees with you that max acceleration in any one gear occurs
at the engine's max torque point.

You jest, I assume? Read the vast number of posts which state this happens
at maximum BHP.

But you seem to be fixated on that point and unable to accept that, at
the corresponding road speed, you can get *greater* acceleration by
using a lower gear and running the engine near to its max power point.

Never ever denied that. But in that lower gear, you will still get better
accelation at the peak torque point, not peak revs.

BHP at the wheels = thrust (lbs) x speed (mph) / 375

OR Thrust = BHP x 375 / speed

So it stands to reason that the more power you can get to the wheels at
a given speed, the greater the thrust and hence acceleration. QED!

I really don't see how you can constantly confuse torque with power in the
same post. It is the torque at the driven wheels which is important - not
the 'power' ie BHP.

I note that you haven't commented on my post about using a continuously
variable transmission to maintain a constant engine speed!

Because the type of transmission is totally irrelevant to my original
point which dealt with the output characteristics of the engine.

--
*If a parsley farmer is sued, can they garnish his wages?

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

On 01/04/2016 10:41, Dave Plowman (News) wrote:


I really don't see how you can constantly confuse torque with power in the
same post. It is the torque at the driven wheels which is important - not
the 'power' ie BHP.


I have never confused torque with power!

If you want to maximise the acceleration of the vehicle, you have
*three* independent[1] parameters to play with - engine speed, engine
torque and gearing. Hence my earlier reference to trying to treat a
three dimensional problem as having only two dimensions. If you fix the
gearing - which you seem to want to do - you restrict your options!

I fail to see why you struggle with the concept that, at a given road
speed, you get *more* torque at the driven wheels by running the engine
at max power and using a lower gear than you would by using a higher
gear at the max torque point - assuming constant transmission
efficiency. Seems blindingly obvious to me!

What part of that don't you understand?

[1] Power is not independent because it is the product of engine speed
and torque.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 01/04/2016 10:41, Dave Plowman (News) wrote:
In article ,
Roger Mills wrote:
On 01/04/2016 00:29, Dave Plowman (News) wrote:


Which is were we came in. I was talking about accleration *in any one gear*

How often do I have to say it?


No-one disagrees with you that max acceleration in any one gear occurs
at the engine's max torque point.

You jest, I assume? Read the vast number of posts which state this happens
at maximum BHP.

That's because when people are saying "max acceleration" they're not
saying "max acceleration in any one gear", they're saying "how to get
from one speed to a higher one the quickest".

Do you agree that when the task is to get from one speed to a higher one
the quickest, max power is what you need to aim for, not max torque?

In article , Clive
George writes
On 31/03/2016 18:05, bert wrote:
In article , Clive
George writes
On 31/03/2016 15:39, bert wrote:

I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

But did changing to a higher gear result in faster acceleration?


Faster compared to what?

Compared to being in the lower gear.

Bearing in mind this is purely seat of the pants stuff, I would say
acceleration initially dropped but then picked up as engine speed moved
back up to and beyond max torque but again tailed off well before max
power.

At 70 in top gear at about 3000 rpm acceleration was quite slow. (max
power is 3500) (This IS a Land Rover we're talking about)
(the answer I'd expect would be "no", hence even though you're feeling
the acceleration drop off, it's still worth staying in the lower gear
and using max power if you want to carry on accelerating as fast as
possible)
No The reason for not staying in the lower gear was because acceleration
was decreasing and well before max power had been reached. I assume this
is because engine speed had moved above max torque and so torque had
decreased.
--
bert

In article , Roger Mills
writes
On 31/03/2016 15:39, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed.
No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed and
the engine's maximum power speed.

Yes or no please - no equivocation!
I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

That's what you'd expect. The torque - and hence the acceleration in
that gear drops off. But it will almost certainly drop even more when
you change to the next gear up even though the engine is producing more
torque.

On changing to the next gear the engine speed was then initially below
max torque.
Next time, take an accelerometer with you, and tell us what happens in
the higher gear.
That would be more scientific but I don't feel sufficient desire to
prove my point to justify the investment.
--
bert

In article , The Natural Philosopher
writes
On 31/03/16 15:39, bert wrote:
In article , Roger Mills
writes
On 30/03/2016 18:39, Dave Plowman (News) wrote:


We're not talking 0-60 times here. Just the best rate of change of
speed.
No vehicle with an IC engine gives a linear rate of increase in speed
from
0 to top speed. It will obviously produce the best acceleration in the
lowest gear, slightly less in the next one up, and so on. But that is a
red herring as regards when the engine produces the best acceleration in
any one gear.


OK, can we agree on this?

In a given gear, the maximum rate of change of road speed will be
achieved at the engine's maximum torque speed. The road speed at which
that occurs will be determined by the engine speed and the gearing.

At a given road speed, the maximum rate of change of road speed will
be achieved at the engine's maximum power point. The necessary gear
ratio to achieve this will be determined by the chosen road speed and
the engine's maximum power speed.

Yes or no please - no equivocation!
I did a little test with my Defender which has max torque at about 2000
rpm and max power at about 3500 rpm.
Going up the gears and accelerating as fast as I could I never got
anywhere near max power in any gear before I could feel the acceleration
dropping off.

That is not the ****ing point, The point is whether or not changing up
to the next gear and dropping the revs lost even MORE acceleration.


****ing in a Land Rover is known officially as "The Land Rover
Experience" as any farmers daughter will tell you.
--
bert

In article , Roger Mills
writes
On 31/03/2016 14:31, Dave Plowman (News) wrote:
In ,
Roger wrote:
Indeed. If you want to accelerate the car as fast as possible, you need
to maximise the power available at the wheels. This invariably means
taking the engine up to at least its maximum power speed before changing
up to the next gear. I say "at least" because quite often - unless you
have lots of closely spaced gears - you still get more acceleration in
the gear you're in by keeping going beyond max power speed until you run
our of revs than by changing to the next gear which drops you a long way
back down the power curve.

And idea set of gearbox ratios would allow you to change up round about
peak BHP and the next higher gear would plonk you at near enough maximum
torque...


Yes, it would. But you'd still have less thrust at the wheels because
of the higher gearing.
Where does one measure thrust at a wheel? Presumably at the hub, or do
you mean torque?
--
bert

In article ,
Roger Mills wrote:
I fail to see why you struggle with the concept that, at a given road
speed, you get *more* torque at the driven wheels by running the engine
at max power and using a lower gear than you would by using a higher
gear at the max torque point - assuming constant transmission
efficiency. Seems blindingly obvious to me!

You are assuming that given speed is such that in your chosen gear the
engine can run at the maximum BHP point.

A very narrow set of conditions.

And again you choose to ignore that this discussion was about an engine's
output - not the effect of different gearing.

--
*Generally speaking, you aren't learning much if your lips are moving.*

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

In article ,
Clive George wrote:
You jest, I assume? Read the vast number of posts which state this
happens at maximum BHP.

That's because when people are saying "max acceleration" they're not
saying "max acceleration in any one gear", they're saying "how to get
from one speed to a higher one the quickest".

Then they need to read the original thread that started this.

Do you agree that when the task is to get from one speed to a higher one
the quickest, max power is what you need to aim for, not max torque?

Aim for?

If you now want to talk about getting the best acceleration through the
gears, and where the best change up point is, it would depend on the
individual car and gear ratios. Some with a wide ratio box and not many
gears might get the best results by revving beyond peak power to get the
engine on a decent part of the torque curve on the higher gear. Some may
be better changing up at near enough max BHP.

But it's all about torque anyway. The amount of torque the engine is
producing at near peak revs to the amount it will be producing when you
change up. BHP is once again irrelevant.

--
*The closest I ever got to a 4.0 in school was my blood alcohol content*

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

On 01/04/2016 13:40, Dave Plowman (News) wrote:
In article ,
Clive George wrote:
You jest, I assume? Read the vast number of posts which state this
happens at maximum BHP.

That's because when people are saying "max acceleration" they're not
saying "max acceleration in any one gear", they're saying "how to get
from one speed to a higher one the quickest".

Then they need to read the original thread that started this.

I did, and what I said is correct. You may think the discussion is still
about one thing, but for most people it's moved on - thread drift is a
perfectly normal thing. You're talking about one thing, everybody else
is talking about something else. Both sides are correct about what
they're talking about, which is why this argument has gone on quite so
long - it's not a physics problem, it's a communication problem.

Do you agree that when the task is to get from one speed to a higher one
the quickest, max power is what you need to aim for, not max torque?

Aim for?

If you now want to talk about getting the best acceleration through the
gears, and where the best change up point is, it would depend on the
individual car and gear ratios. Some with a wide ratio box and not many
gears might get the best results by revving beyond peak power to get the
engine on a decent part of the torque curve on the higher gear. Some may
be better changing up at near enough max BHP.

You could have just said "Yes" - it would have been quicker...