94 1.8 rev limiter.

Alan Baker > wrote:

>In article >,
> "Chris D'Agnolo" > wrote:
>
>> Was that the same for the 1.6? What Mal describes is exactly the way my 92
>> 1.6 was. My 99 1.8 cuts out almost exactly at an indicated 7000, just as it
>> is beginning to really 'SING'............Now even I am thinking about how to
>> bump the rev limiter up a bit ;-)
>
>Before you do that, you might want to look at a power curve and see if
>there's actually any point...

http://flyinmiata.com/tech/dyno_runs...ell_112700.pdf

Does not look like you want to shift at 7000.

Leon

>>
>> Chris
>> 99BBB
>>
>> "Lanny Chambers" > wrote in message
>> ...
>> > In article >,
>> > "Mal Osborne" > wrote:
>> >
>> >> Read in a few places that the 94 1.8 is limited at 7000RPM. Mine seems to
>> >> spin a bit further than this, looks like 7200 on the tacho. Anyone
>> >> confirm
>> >> what it really is?
>> >
>> > The ECU cuts the injectors at 7200 rpm. It may appear to vary from one
>> > Miata to the next, but that's because the tach isn't especially
>> > accurate. 7000 is a good shift point.
>> >
>> > --
>> > Lanny Chambers
>> > '94C, St. Louis
>> > http://www.hummingbirds.net/alignment.html
--
Leon van Dommelen Bess, the Miata Bozo, the Miata
http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

Alan Baker > wrote:

>In article >,
> Lanny Chambers > wrote:
>
>> In article >,
>> Alan Baker > wrote:
>>
>> > Maximizing acceleration consists almost entirely of maximizing the area
>> > under the horsepower curve.
>>
>> Not quite; I think the torque curve is more relevant. Torque
>> multiplication via gearing is a factor as well, and the optimum shift
>> point may be different in each gear. The goal is to shift at the point
>> the next gear will provide better acceleration. If you plot rpm versus
>> acceleration in each gear, it's where the curve for one gear crosses
>> that of the next. Practically speaking, many cars' gear spacing and
>> redlines will not permit reaching the crossing point, and so shifting at
>> redline is the best one can do.
>
><sigh>
>
>No. Torque curve is *not* more relevant.
>
>Horsepower is torque multiplied by rpm (multiplied by a constant, of
>course) and hence torque at the rear wheels, is horsepower divided by
>RPM at the rear wheels. Are you with me so far? So if you want maximum
>torque at the rear wheels, at any given moment you must be in the gear
>that delivers maximum horsepower, *not* maximum torque.

That is true. However, maximizing area below the horsepower curve does
not have any meaning that I know off. To compare engines that are
to operate on the same car, by approximation the best engine has the
largest area below the torque curve in the used rpm range.

Leon
--
Leon van Dommelen Bess, the Miata Bozo, the Miata
http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

"Alan Baker" > wrote in message
...
> In article >,
> Lanny Chambers > wrote:
>
>> In article >,
>> Alan Baker > wrote:
>>
>> > Maximizing acceleration consists almost entirely of maximizing the area
>> > under the horsepower curve.
>>
>> Not quite; I think the torque curve is more relevant. Torque
>> multiplication via gearing is a factor as well, and the optimum shift
>> point may be different in each gear. The goal is to shift at the point
>> the next gear will provide better acceleration. If you plot rpm versus
>> acceleration in each gear, it's where the curve for one gear crosses
>> that of the next. Practically speaking, many cars' gear spacing and
>> redlines will not permit reaching the crossing point, and so shifting at
>> redline is the best one can do.
>
> <sigh>
>
> No. Torque curve is *not* more relevant.
>
> Horsepower is torque multiplied by rpm (multiplied by a constant, of
> course) and hence torque at the rear wheels, is horsepower divided by
> RPM at the rear wheels. Are you with me so far? So if you want maximum
> torque at the rear wheels, at any given moment you must be in the gear
> that delivers maximum horsepower, *not* maximum torque.

Your conclusion does not follow your statement. Torque can be changed by
gearing, horsepower cannot. As you stated there is an rpm quotient in
horsepower, so horsepower out of a gear box will always equal horsepower in
(less the inefficiencies) no matter what gear is used. For example a 2:1
reduction will increase torque by a factor of 2 but also reduce rpm by that
factor, so horsepower remains the same.

In article >,
(Leon van Dommelen) wrote:

> Alan Baker > wrote:
>
> >In article >,
> > Lanny Chambers > wrote:
> >
> >> In article >,
> >> Alan Baker > wrote:
> >>
> >> > Maximizing acceleration consists almost entirely of maximizing the area
> >> > under the horsepower curve.
> >>
> >> Not quite; I think the torque curve is more relevant. Torque
> >> multiplication via gearing is a factor as well, and the optimum shift
> >> point may be different in each gear. The goal is to shift at the point
> >> the next gear will provide better acceleration. If you plot rpm versus
> >> acceleration in each gear, it's where the curve for one gear crosses
> >> that of the next. Practically speaking, many cars' gear spacing and
> >> redlines will not permit reaching the crossing point, and so shifting at
> >> redline is the best one can do.
> >
> ><sigh>
> >
> >No. Torque curve is *not* more relevant.
> >
> >Horsepower is torque multiplied by rpm (multiplied by a constant, of
> >course) and hence torque at the rear wheels, is horsepower divided by
> >RPM at the rear wheels. Are you with me so far? So if you want maximum
> >torque at the rear wheels, at any given moment you must be in the gear
> >that delivers maximum horsepower, *not* maximum torque.
>
> That is true. However, maximizing area below the horsepower curve does
> not have any meaning that I know off. To compare engines that are
> to operate on the same car, by approximation the best engine has the
> largest area below the torque curve in the used rpm range.
>
> Leon

But that's just saying the engine with more horsepower, isn't it? At any
given RPM, if you have more torque, you have more horsepower.

But horsepower combines the effect of engine torque plus the ability to
multiply it by gearing ratios to achieve the maximum torque at the rear
wheels.

Do a thought experiment. Imagine the engine in your Miata could not only
operate in its normal range, but also in a range of three times normal.
For some strange reason, it doesn't blow up and although it breathes
worse, it still produces half the torque that it does in the
conventional range.

So...

In which range to you want your gearbox set to allow you to use?

In article >,
"Chas Hurst" > wrote:

> "Alan Baker" > wrote in message
> ...
> > In article >,
> > Lanny Chambers > wrote:
> >
> >> In article >,
> >> Alan Baker > wrote:
> >>
> >> > Maximizing acceleration consists almost entirely of maximizing the area
> >> > under the horsepower curve.
> >>
> >> Not quite; I think the torque curve is more relevant. Torque
> >> multiplication via gearing is a factor as well, and the optimum shift
> >> point may be different in each gear. The goal is to shift at the point
> >> the next gear will provide better acceleration. If you plot rpm versus
> >> acceleration in each gear, it's where the curve for one gear crosses
> >> that of the next. Practically speaking, many cars' gear spacing and
> >> redlines will not permit reaching the crossing point, and so shifting at
> >> redline is the best one can do.
> >
> > <sigh>
> >
> > No. Torque curve is *not* more relevant.
> >
> > Horsepower is torque multiplied by rpm (multiplied by a constant, of
> > course) and hence torque at the rear wheels, is horsepower divided by
> > RPM at the rear wheels. Are you with me so far? So if you want maximum
> > torque at the rear wheels, at any given moment you must be in the gear
> > that delivers maximum horsepower, *not* maximum torque.
>
> Your conclusion does not follow your statement. Torque can be changed by
> gearing, horsepower cannot. As you stated there is an rpm quotient in
> horsepower, so horsepower out of a gear box will always equal horsepower in
> (less the inefficiencies) no matter what gear is used. For example a 2:1
> reduction will increase torque by a factor of 2 but also reduce rpm by that
> factor, so horsepower remains the same.

<sigh>

Go away and do some research. You'll see I'm right.

Alan,

In theory you are right.

In a practical application, you want to output the maximum average
horsepower as you shift through the gears. The factory transmission and
rear-end gear ratios may not be designed to give maximum accelaration.
Allowing the engine to run past torque peak before shifting often produces
higher average horsepower from the next gear's operating range. Take two
stock 94 Miatas to the drag strip. Instruct one driver to shift at torque
peak in each gear. Instruct the other driver to shift at 7000 rpm. There is
no doubt which Miata will win.


"Alan Baker" > wrote in message
...
> In article >,
> "Chas Hurst" > wrote:
>
>> "Alan Baker" > wrote in message
>> ...
>> > In article >,
>> > Lanny Chambers > wrote:
>> >
>> >> In article >,
>> >> Alan Baker > wrote:
>> >>
>> >> > Maximizing acceleration consists almost entirely of maximizing the
>> >> > area
>> >> > under the horsepower curve.
>> >>
>> >> Not quite; I think the torque curve is more relevant. Torque
>> >> multiplication via gearing is a factor as well, and the optimum shift
>> >> point may be different in each gear. The goal is to shift at the point
>> >> the next gear will provide better acceleration. If you plot rpm versus
>> >> acceleration in each gear, it's where the curve for one gear crosses
>> >> that of the next. Practically speaking, many cars' gear spacing and
>> >> redlines will not permit reaching the crossing point, and so shifting
>> >> at
>> >> redline is the best one can do.
>> >
>> > <sigh>
>> >
>> > No. Torque curve is *not* more relevant.
>> >
>> > Horsepower is torque multiplied by rpm (multiplied by a constant, of
>> > course) and hence torque at the rear wheels, is horsepower divided by
>> > RPM at the rear wheels. Are you with me so far? So if you want maximum
>> > torque at the rear wheels, at any given moment you must be in the gear
>> > that delivers maximum horsepower, *not* maximum torque.
>>
>> Your conclusion does not follow your statement. Torque can be changed by
>> gearing, horsepower cannot. As you stated there is an rpm quotient in
>> horsepower, so horsepower out of a gear box will always equal horsepower
>> in
>> (less the inefficiencies) no matter what gear is used. For example a 2:1
>> reduction will increase torque by a factor of 2 but also reduce rpm by
>> that
>> factor, so horsepower remains the same.
>
> <sigh>
>
> Go away and do some research. You'll see I'm right.

"lgadbois" > wrote in
k.net:

> Take two stock 94 Miatas to the drag strip. Instruct one driver to
> shift at torque peak in each gear. Instruct the other driver to
> shift at 7000 rpm. There is no doubt which Miata will win.

The white one, of course...

Alan Baker > wrote:

>In article >,
> (Leon van Dommelen) wrote:
>
>> Alan Baker > wrote:
>>
>> >In article >,
>> > Lanny Chambers > wrote:
>> >
>> >> In article >,
>> >> Alan Baker > wrote:
>> >>
>> >> > Maximizing acceleration consists almost entirely of maximizing the area
>> >> > under the horsepower curve.
>> >>
>> >> Not quite; I think the torque curve is more relevant. Torque
>> >> multiplication via gearing is a factor as well, and the optimum shift
>> >> point may be different in each gear. The goal is to shift at the point
>> >> the next gear will provide better acceleration. If you plot rpm versus
>> >> acceleration in each gear, it's where the curve for one gear crosses
>> >> that of the next. Practically speaking, many cars' gear spacing and
>> >> redlines will not permit reaching the crossing point, and so shifting at
>> >> redline is the best one can do.
>> >
>> ><sigh>
>> >
>> >No. Torque curve is *not* more relevant.
>> >
>> >Horsepower is torque multiplied by rpm (multiplied by a constant, of
>> >course) and hence torque at the rear wheels, is horsepower divided by
>> >RPM at the rear wheels. Are you with me so far? So if you want maximum
>> >torque at the rear wheels, at any given moment you must be in the gear
>> >that delivers maximum horsepower, *not* maximum torque.
>>
>> That is true. However, maximizing area below the horsepower curve does
>> not have any meaning that I know off. To compare engines that are
>> to operate on the same car, by approximation the best engine has the
>> largest area below the torque curve in the used rpm range.
>>
>> Leon
>
>But that's just saying the engine with more horsepower, isn't it?

No. There is a difference between peak horsepower, as reported,
and area below the torque curve. Area below the torque curve is
a valid measure for engine design and improvements. Unfortunately,
popular books like Norm Garrett III make blanket statements about
this which apparently fool a lot of people thinking that they
somehow have to maximize area below the torque curve, or just
torque, while *driving* instead of *designing* engines. There
have been many discussions like this here, with countless people
arguing that torque should be maximized instead of hp. Many
painting very graphical pictures of what torque is versus hp,
but showing little knowledge of dynamics and conservation of
energy.

> At any
>given RPM, if you have more torque, you have more horsepower.

True but irrelevant. The point would be relevant if you had
more torque at *every* rpm, but that is not necessarily how
things work.

>But horsepower combines the effect of engine torque plus the ability to
>multiply it by gearing ratios to achieve the maximum torque at the rear
>wheels.

True, but still irrelevant.

>Do a thought experiment. Imagine the engine in your Miata could not only
>operate in its normal range, but also in a range of three times normal.
>For some strange reason, it doesn't blow up and although it breathes
>worse, it still produces half the torque that it does in the
>conventional range.
>
>So...
>
>In which range to you want your gearbox set to allow you to use?

You are missing the point. The area under the torque curve has to do
with you not having full control over where you can operate. Unless
you have CVT, you have to operate over ranges of rpm, even if you
correctly select the gear that operates at the largest possible hp
at each rpm. While in such a range, if you replace your engine with
one that has a lower peak hp but more area under the torque curve,
you will accelerate faster.

Of course, the swap has to be done very quickly.

Leon
--
Leon van Dommelen Bess, the Miata Bozo, the Miata
http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

"lgadbois" > wrote:

>Alan,
>
>In theory you are right.

Correct.

>In a practical application, you want to output the maximum average
>horsepower as you shift through the gears.

Correct, but it is the *time-average* maximum horsepower. Which is
equivalent to saying that you must at each *instant* use the gear
that gives the highest hp at that rpm.

Which is exactly what Alan said.

> The factory transmission and
>rear-end gear ratios may not be designed to give maximum accelaration.

Actually, the only thing is losses. This is a secondary effect that will
slightly favor the higher gear if the higher-gear-rpm hp and the lower-gear-
rpm hp are the same. Let's not worry about those small unpredictable effects.
And the rear-end ratio is irrelevant regardless of losses.

>Allowing the engine to run past torque peak before shifting often produces
>higher average horsepower from the next gear's operating range.

True. But note that what Alan is saying is equivalent to shift after *peak
horsepower*. He is in no way telling you to shift at peak torque,
which would be ludicrous. Peak horsepower is after peak torque.

> Take two
>stock 94 Miatas to the drag strip. Instruct one driver to shift at torque
>peak in each gear. Instruct the other driver to shift at 7000 rpm. There is
>no doubt which Miata will win.

No. Shifting at peak torque is ludicrous. However, shifting, (after peak
hp), at the time that the *hp* at the rpm you are shifting into has become
equal to the *hp* at the rpm you are shifting out of is exactly what you
need to do for best performance, and that is what Alan told you to do.
And I myself over the many years in this group. Let me join Alan in
sighing.

Leon

>
>"Alan Baker" > wrote in message
...
>> In article >,
>> "Chas Hurst" > wrote:
>>
>>> "Alan Baker" > wrote in message
>>> ...
>>> > In article >,
>>> > Lanny Chambers > wrote:
>>> >
>>> >> In article >,
>>> >> Alan Baker > wrote:
>>> >>
>>> >> > Maximizing acceleration consists almost entirely of maximizing the
>>> >> > area
>>> >> > under the horsepower curve.
>>> >>
>>> >> Not quite; I think the torque curve is more relevant. Torque
>>> >> multiplication via gearing is a factor as well, and the optimum shift
>>> >> point may be different in each gear. The goal is to shift at the point
>>> >> the next gear will provide better acceleration. If you plot rpm versus
>>> >> acceleration in each gear, it's where the curve for one gear crosses
>>> >> that of the next. Practically speaking, many cars' gear spacing and
>>> >> redlines will not permit reaching the crossing point, and so shifting
>>> >> at
>>> >> redline is the best one can do.
>>> >
>>> > <sigh>
>>> >
>>> > No. Torque curve is *not* more relevant.
>>> >
>>> > Horsepower is torque multiplied by rpm (multiplied by a constant, of
>>> > course) and hence torque at the rear wheels, is horsepower divided by
>>> > RPM at the rear wheels. Are you with me so far? So if you want maximum
>>> > torque at the rear wheels, at any given moment you must be in the gear
>>> > that delivers maximum horsepower, *not* maximum torque.
>>>
>>> Your conclusion does not follow your statement. Torque can be changed by
>>> gearing, horsepower cannot. As you stated there is an rpm quotient in
>>> horsepower, so horsepower out of a gear box will always equal horsepower
>>> in
>>> (less the inefficiencies) no matter what gear is used. For example a 2:1
>>> reduction will increase torque by a factor of 2 but also reduce rpm by
>>> that
>>> factor, so horsepower remains the same.
>>
>> <sigh>
>>
>> Go away and do some research. You'll see I'm right.
>
--
Leon van Dommelen Bess, the Miata Bozo, the Miata
http://www.dommelen.net/miata
The only thing better than a white Miata is two white Miatas

I'll leave the quoted text intact below, but so many people get this
wrong so often, I want everyone to understand this.

Imagine two engines. Both produce exactly the same peak torque and
exactly the same peak horsepower, but one has an absolutely flat torque
curve and one has an absolutely flat horspower curve; are you with me so
far? To make it easier talk about let's put a few numbers into place.
Power is equal to torque (rotational force) multiplied by rate or
rotation, and in our case, horsepower is equal to torque in foot-pounds
multiplied by RPM divided by 5252.

So if both engines have a redline of 5252, then if engine 1 (with a flat
torque curve) has 200 ft-lb torque, it has horsepower curve that is an
straight line from 0 at 0 RPM to 200 hp at 5252 RPM. Engine 2 (with a
flat horsepower curve) has 200 ft-lb of torque, rising to 400 at 2626
RPM, 800 ft-lb at 1313, and (for the sake of argument) the curve stops
at that speed (a little fast for idle, but close enough for government
work)

Now, if both engines are connected to a continuously variable
transmission that will let them operate at typical road car speeds, what
can we discover.

First, engine 1. If -- as some people insist -- all you need to do is
maximize average torque (another way of expressing maximize the area
under the torque curve), then at what RPM should you operate the engine?
Any RPM delivers the same torque, so according to this argument, any RPM
should produce the same acceleration. But, of course, for any road
speed, the transmission will deliver the greatest torque multiplication
at its numerically highest ratio. IOW, operate the engine at peak
horsepower.

Now let's look at engine 2 with the flat horsepower curve. Now it really
doesn't matter at what RPM you operate the engine. At redline, the
transmission will be at ratio x when the road speed is n, but at half
redline, you'll get twice as much torque, but it will be multiplied by a
ratio of x/2, giving you precisely the same output torque.

Does every get it yet?

Horsepower encompasses both engine torque and how much ratio you can
multiply it by due to RPM. If peak horsepower is twice horsepower at
peak torque then it means that even if you have one *tenth* the engine
torque, you must therefore have 20 times the RPM and thus will deliver
twice the output torque because your gear ratio will be 20 times what it
is at peak torque.

Maximize average *engine* torque and you will always be operating at
less than a maximum *output* torque. Maximize average horsepower
(maximize the area under the horsepower curve) and you will get the best
combination of available engine torque multiplied by gear ratio.

Always.


In article >,
(Leon van Dommelen) wrote:

> Alan Baker > wrote:
>
> >In article >,
> > (Leon van Dommelen) wrote:
> >
> >> Alan Baker > wrote:
> >>
> >> >In article >,
> >> > Lanny Chambers > wrote:
> >> >
> >> >> In article >,
> >> >> Alan Baker > wrote:
> >> >>
> >> >> > Maximizing acceleration consists almost entirely of maximizing the
> >> >> > area
> >> >> > under the horsepower curve.
> >> >>
> >> >> Not quite; I think the torque curve is more relevant. Torque
> >> >> multiplication via gearing is a factor as well, and the optimum shift
> >> >> point may be different in each gear. The goal is to shift at the point
> >> >> the next gear will provide better acceleration. If you plot rpm versus
> >> >> acceleration in each gear, it's where the curve for one gear crosses
> >> >> that of the next. Practically speaking, many cars' gear spacing and
> >> >> redlines will not permit reaching the crossing point, and so shifting
> >> >> at
> >> >> redline is the best one can do.
> >> >
> >> ><sigh>
> >> >
> >> >No. Torque curve is *not* more relevant.
> >> >
> >> >Horsepower is torque multiplied by rpm (multiplied by a constant, of
> >> >course) and hence torque at the rear wheels, is horsepower divided by
> >> >RPM at the rear wheels. Are you with me so far? So if you want maximum
> >> >torque at the rear wheels, at any given moment you must be in the gear
> >> >that delivers maximum horsepower, *not* maximum torque.
> >>
> >> That is true. However, maximizing area below the horsepower curve does
> >> not have any meaning that I know off. To compare engines that are
> >> to operate on the same car, by approximation the best engine has the
> >> largest area below the torque curve in the used rpm range.
> >>
> >> Leon
> >
> >But that's just saying the engine with more horsepower, isn't it?
>
> No. There is a difference between peak horsepower, as reported,
> and area below the torque curve. Area below the torque curve is
> a valid measure for engine design and improvements. Unfortunately,
> popular books like Norm Garrett III make blanket statements about
> this which apparently fool a lot of people thinking that they
> somehow have to maximize area below the torque curve, or just
> torque, while *driving* instead of *designing* engines. There
> have been many discussions like this here, with countless people
> arguing that torque should be maximized instead of hp. Many
> painting very graphical pictures of what torque is versus hp,
> but showing little knowledge of dynamics and conservation of
> energy.
>
> > At any
> >given RPM, if you have more torque, you have more horsepower.
>
> True but irrelevant. The point would be relevant if you had
> more torque at *every* rpm, but that is not necessarily how
> things work.
>
> >But horsepower combines the effect of engine torque plus the ability to
> >multiply it by gearing ratios to achieve the maximum torque at the rear
> >wheels.
>
> True, but still irrelevant.
>
> >Do a thought experiment. Imagine the engine in your Miata could not only
> >operate in its normal range, but also in a range of three times normal.
> >For some strange reason, it doesn't blow up and although it breathes
> >worse, it still produces half the torque that it does in the
> >conventional range.
> >
> >So...
> >
> >In which range to you want your gearbox set to allow you to use?
>
> You are missing the point. The area under the torque curve has to do
> with you not having full control over where you can operate. Unless
> you have CVT, you have to operate over ranges of rpm, even if you
> correctly select the gear that operates at the largest possible hp
> at each rpm. While in such a range, if you replace your engine with
> one that has a lower peak hp but more area under the torque curve,
> you will accelerate faster.
>
> Of course, the swap has to be done very quickly.
>
> Leon