Hi all,
having just swapped an automatic for a manual, I now have gears and
a tachometer as controllable variables in my driving.
So it occured to me that I've never really done that bloke thing of
knowing about rev ranges, when "best" to change gear (other than when it
feels "right"), and such like.
So.... for instance, given there's an obvious upper range to be
avoided (as indicated by red lines), is there actually a practical lower
limit (obviously without stalling)? Is there a "sweet spot" in between?
Is it possible to determine at what amount of revs a particular
engine is theoretically "best" at - and would "best" be defined in terms
of fuel economy or some other operating measure?
I'd imagine that any such measures would vary according to the
vehicle (& engine size).
Is it obvious where I'm coming from, or should I just go get on with
enjoying driving without worrying about such stuff

Cheers,
Marlon

Marlon wrote:

Hi all,
having just swapped an automatic for a manual, I now have gears and
a tachometer as controllable variables in my driving.
So it occured to me that I've never really done that bloke thing of
knowing about rev ranges, when "best" to change gear (other than when it
feels "right"), and such like.
So.... for instance, given there's an obvious upper range to be
avoided (as indicated by red lines), is there actually a practical lower
limit (obviously without stalling)? Is there a "sweet spot" in between?
Is it possible to determine at what amount of revs a particular
engine is theoretically "best" at - and would "best" be defined in terms
of fuel economy or some other operating measure?
I'd imagine that any such measures would vary according to the
vehicle (& engine size).
Is it obvious where I'm coming from, or should I just go get on with
enjoying driving without worrying about such stuff

Cheers,
Marlon


The answer to this depends on quite a lot of things, such as the size
and type of engine (petrol/diesel have quite different characteristics),
the size of the car, the type of road you are driving on etc...

That said the basic way most people would drive is to use the bottom
third to half of the rev range when driving normally, for economy,
comfort and noise, and to use the upper half of the range for more
spirited driving, or if you wish to overtake.

Marlon wrote:

Is it obvious where I'm coming from, or should I just go get on with
enjoying driving without worrying about such stuff

Yep, unless you have a TD.

On 6 Aug, 13:53, Marlon wrote:
Hi all,
* * *having just swapped an automatic for a manual, I now have gears and
a tachometer as controllable variables in my driving.
* * *So it occured to me that I've never really done that bloke thing of
knowing about rev ranges, when "best" to change gear (other than when it
feels "right"), and such like.
* * *So.... for instance, given there's an obvious upper range to be
avoided (as indicated by red lines), is there actually a practical lower
limit (obviously without stalling)? *Is there a "sweet spot" in between?

As I understand it, which could very easily be wrong:

- You should avoid using low revs with high throtle, as this can
damage the engine, in particular cause the head gaskete to blow. I
interpret this as hardly touch the throtle with the revs lower than
1.5k, and do not use full throtle below around 2.2k.

- When accelerating, the engine works most efficently at full throtle
between 3 and 4k. If you want to save fuel, change up at 4k and that
is usually around 3k in the next gear.

- Engine damage occurs over about 0.5k over the red line. Unless
really critical, do not use the revs above this. Most modern cars
have rev limiters that prevent going much over the red line anyway.

This is all based on petrol cars. I know even less about tractors

"Marlon" wrote in message
...

Hi all,
having just swapped an automatic for a manual, I now have gears and
a tachometer as controllable variables in my driving.
So it occured to me that I've never really done that bloke thing of
knowing about rev ranges, when "best" to change gear (other than when it
feels "right"), and such like.
So.... for instance, given there's an obvious upper range to be
avoided (as indicated by red lines), is there actually a practical lower
limit (obviously without stalling)? Is there a "sweet spot" in between?
Is it possible to determine at what amount of revs a particular
engine is theoretically "best" at - and would "best" be defined in terms
of fuel economy or some other operating measure?
I'd imagine that any such measures would vary according to the
vehicle (& engine size).
Is it obvious where I'm coming from, or should I just go get on with
enjoying driving without worrying about such stuff


Change gear when it feels/sounds right, which you'll pick up very quickly.
The rev counter is a pretty toy.

Steve

"shazzbat" wrote in message
...

"Marlon" wrote in message
...

Hi all,
having just swapped an automatic for a manual, I now have
gears and
a tachometer as controllable variables in my driving.
So it occured to me that I've never really done that bloke
thing of
knowing about rev ranges, when "best" to change gear (other
than when it
feels "right"), and such like.
So.... for instance, given there's an obvious upper range
to be
avoided (as indicated by red lines), is there actually a
practical lower
limit (obviously without stalling)? Is there a "sweet spot"
in between?
Is it possible to determine at what amount of revs a
particular
engine is theoretically "best" at - and would "best" be
defined in terms
of fuel economy or some other operating measure?
I'd imagine that any such measures would vary according to
the
vehicle (& engine size).
Is it obvious where I'm coming from, or should I just go
get on with
enjoying driving without worrying about such stuff


Change gear when it feels/sounds right, which you'll pick up
very quickly. The rev counter is a pretty toy.

Yup. It isn't that long ago to a time when tachometers were only
fitted in 'sports' or more expensive cars as std equipment.
They have little practical use.
Mike.

On 7 Aug, 12:25, "Mike G" wrote:
"shazzbat" wrote in message

...
Change gear when it feels/sounds right, which you'll pick up
very quickly. The rev counter is a pretty toy.

Yup. It isn't that long ago to a time when tachometers were only
fitted in 'sports' or more expensive cars as std equipment.
They have little practical use.
Mike.

I really disagree. I can make a much more acurate decision about when
to change gear with a rev counter than with my ear. At the bottom of
the rev range this probably translates to a lower incidence of head
gasket failures, at the top of the rev range it definatly means higher
performance. As I am willing to spend a significant amount of money
on a larger engine, the relativly small cost of a rev counter is well
worth it to me. YMMV.

Dave wrote:
On 7 Aug, 12:25, "Mike G" wrote:
"shazzbat" wrote in message

...
Change gear when it feels/sounds right, which you'll pick up
very quickly. The rev counter is a pretty toy.

Yup. It isn't that long ago to a time when tachometers were only
fitted in 'sports' or more expensive cars as std equipment.
They have little practical use.
Mike.

I really disagree. I can make a much more acurate decision about when
to change gear with a rev counter than with my ear. At the bottom of
the rev range this probably translates to a lower incidence of head
gasket failures

How does it stop your headgasket failing?

Mike P

On 7 Aug, 13:49, "Mike P" wrote:
Dave wrote:
On 7 Aug, 12:25, "Mike G" wrote:
"shazzbat" wrote in message

...
Change gear when it feels/sounds right, which you'll pick up
very quickly. The rev counter is a pretty toy.

Yup. It isn't that long ago to a time when tachometers were only
fitted in 'sports' or more expensive cars as std equipment.
They have little practical use.
Mike.

I really disagree. *I can make a much more acurate decision about when
to change gear with a rev counter than with my ear. *At the bottom of
the rev range this probably translates to a lower incidence of head
gasket failures

How does it stop your headgasket failing?

Mike P

I am not sure, but I was told that using lots of throtle at low revs
caused the head gasket to fail. Once I stopped doing this I stopped
getting head gasket failures (and I had had a few). A rev counter
allows me to make this decision more easily and acuratly. I could be
wrong of course, but it seems to make sence to me. I am certain about
the other end of the rev range.

"Dave" wrote in message
...
On 7 Aug, 12:25, "Mike G" wrote:
"shazzbat" wrote in
message

...
Change gear when it feels/sounds right, which you'll pick up
very quickly. The rev counter is a pretty toy.

Yup. It isn't that long ago to a time when tachometers were
only
fitted in 'sports' or more expensive cars as std equipment.
They have little practical use.
Mike.

I really disagree. I can make a much more acurate decision
about when
to change gear with a rev counter than with my ear. At the
bottom of
the rev range this probably translates to a lower incidence of
head
gasket failures, at the top of the rev range it definatly means
higher
performance.

At the top of the rev 'range' maybe. but peak revs on a tacho is
seldom the right time to change gear for maximum performance.
As far as lower revs are concerned, you shouldn't need a tacho to
tell you when revs are too low.
IME you can hear and feel when to change gear, up or down. I
can't say I've ever needed to refer to a tacho, even when driving
briskly.
Mike.