94 1.8 rev limiter.

In article >,
(Leon van Dommelen) wrote:

> "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,

Clearly I was misunderstanding what you were trying to say in the post
to which I just replied. From this post, it's clear that you get it.

Alan

>
> 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.
> >

"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.

That's your reply? You're a charlatan.

In article >,
"Chas Hurst" > wrote:

> "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.
>
> That's your reply? You're a charlatan.

That's my reply to *you*.

The fact that torque can be changed by *gearing* is precisely the point.

Half the torque of RPM n at RPM n times (anything more than 2) and you
can change the gearing to get more delivered torque at the rear wheels.
That's precisely what horsepower tells you. If you have more horsepower
at RPM y rather than RPM x, then you can more than make up any loss in
torque due to more a favourable gear ratio.

Alan Baker > wrote:

>In article >,
> (Leon van Dommelen) wrote:
>
>> "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,
>
>Clearly I was misunderstanding what you were trying to say in the post
>to which I just replied. From this post, it's clear that you get it.

And area below the torque curve is still the proper engine design
or modification criterion to use. It is just important to remember
that it is not the proper engine *driving* criterion.

Leon

>Alan
>
>>
>> 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

That assumes the power curve for all Miatas is the same. A few degrees
differance in CAS timing, a cooler running thermostat, a slightly stretched
timing belt, a remachined head or a myriad of other minor differances could
move the optimal point up or down a few hundred RPM


"Alan Baker" > wrote in message
...
> In article >,
> "Mal Osborne" > wrote:
>
>> I think 7000 is about the optimal point to change on my '94. A 7200
>> limiter
>> would allow a little slack, but 7000 would be a pain.
>
> But it's not one of those things that *requires* thought. Simply find a
> power curve for the Miata and *see* if that is the correct shift point.
>
>>
>> "Alan Baker" > wrote in message
>> ...
>> > 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...
>> >
>> >>
>> >> 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