Best MPG : 5-speed vs. auto?

« Paul » <"« Paul > wrote in article
>...
> SQ wrote:
> >
> > Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
> > Toyota, which would
> > get better MPG -- one with automatic tranny or 5-speed?
> >
> > I understand that 5 speeds vs. 4 gives a better selection of rpms,
> > meaning at the same speed you can cruise with lower rpms, assuming the
> > same rear axle ratio.
> >
> > Also I understand that 5-speeds don't have a torque converter that
> > autos have which robbs some power.
> >
> > But in my experience, in city driving, it's hard to shift well for good
> > MPG. Maybe I am shifting at wrong rpms, I am not sure.
>
> Automatics will always have some loss due to the torque convertor.



The use of lock-up torque converters has eliminated that situation.

When the converter is locked, you have a direct mechanical connection
between the engine crankshaft and the driveshaft - just as with a manual
tranny.

Computer-controlled transmissions can now shift gears at exactly the
correct moment......

If it is fuel mileage I'm looking for, I'll take an automatic over a stick.

SQ wrote:
> Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
> Toyota, which would
> get better MPG -- one with automatic tranny or 5-speed?
>
> I understand that 5 speeds vs. 4 gives a better selection of rpms,
> meaning at the same speed you can cruise with lower rpms, assuming the
> same rear axle ratio.
>
> Also I understand that 5-speeds don't have a torque converter that
> autos have which robbs some power.
>
> But in my experience, in city driving, it's hard to shift well for good
> MPG. Maybe I am shifting at wrong rpms, I am not sure.
>


Not hard at all. Forget what they said in olden days about not lugging
the engine. Shift early- if the car WON'T accelerate, then you shifted
too soon. But if it accelerates smoothly, even though leisurely, that is
fine. Even though my Neon R/T has a fairly agressive camshaft(s), I can
shift below 2K, and it will be smooth with no shudder, though it is a
leisurely acceleration. Also, when you see a light ahead, shift into
neutral and coast. Yeah, it is illegal in many states, but those laws
were written when brakes were primitive and gas was a quarter a gallon.

There was a study in the late seventies by a European mfg. I think it
was VW. They ran two cars on test trac for 100K miles, or some long
distance. They lugged one car, drove other without lugging them. When
they tore them down to look at crank, no discernable difference. I wish
I could remember the mag I read about this test in, but I cannot (it was
about 1980). Anyway, it altered my driving habits.

« Paul » wrote:
> SQ wrote:
>
>>Well, this explains a lot. I have been driving a 5-speed and have been
>>getting awful mpg in city. Now I am realizing I am shifting at very
>>high rpms, around 2500. I will try to lower the rpms during shifting
>>and see if it makes any difference.
>>
>>(I think one problem in my particular situation is that the type of
>>engine I have derives it's power from high rpms, you have to rev it to
>>get going, and I don't like it)
>
>
> Small overhead cam engines are like that. Especially ones with lots of valves per
> cylinder. They develop max hp and torque near max rpm.

But you don't NEED that much hp to drive it. One can take off with fair
throttle, as soon as you are moving, begin shifting. Short shift. You
will not be the leader of the pack, but you can save gas.

* wrote:
>
> Computer-controlled transmissions can now shift gears at exactly the
> correct moment......
>
> If it is fuel mileage I'm looking for, I'll take an automatic over a stick.
>
>
>

No way! We traded in a Voyager stick for a new Chrysler van. The auto
in the new one shifts at WAY higher rpm than we did with the old one,
and we get nowhere the milage. You can short shift a stick- newer ones
with computer control, you can't even FORCE an upshift! And the
computer wants to supply AVERAGE driving program. If I knew how to redo
programming I would.

Anyone know if the dealer shop can alter the shift point?

Don Stauffer wrote:
>
Also, when you see a light ahead, shift into
> neutral and coast. Yeah, it is illegal in many states, but those laws
> were written when brakes were primitive and gas was a quarter a gallon.
>

I just don't get idiots that come onto a world wide web boasting about
doing highly illegal and deadly practices while saying 'forget what they
used to say', it's cool now to go out of control and potentially kill
yourself or others....

Mike

* wrote:
>
> « Paul » <"« Paul > wrote in article
> >...
> > SQ wrote:
> > >
> > > Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
> > > Toyota, which would
> > > get better MPG -- one with automatic tranny or 5-speed?
> > >
> > > I understand that 5 speeds vs. 4 gives a better selection of rpms,
> > > meaning at the same speed you can cruise with lower rpms, assuming the
> > > same rear axle ratio.
> > >
> > > Also I understand that 5-speeds don't have a torque converter that
> > > autos have which robbs some power.
> > >
> > > But in my experience, in city driving, it's hard to shift well for good
> > > MPG. Maybe I am shifting at wrong rpms, I am not sure.
> >
> > Automatics will always have some loss due to the torque convertor.
>
> The use of lock-up torque converters has eliminated that situation.
>
> When the converter is locked, you have a direct mechanical connection
> between the engine crankshaft and the driveshaft - just as with a manual
> tranny.
>
> Computer-controlled transmissions can now shift gears at exactly the
> correct moment......
>
> If it is fuel mileage I'm looking for, I'll take an automatic over a stick.

A TC locks up at a certain speed (~38 mph) in high gear.
Typical city driving rarely lets you get above that speed.
I think the original poster was talking about city driving (read his post#2).

SQ wrote:
> Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
> Toyota, which would
> get better MPG -- one with automatic tranny or 5-speed?
>
> I understand that 5 speeds vs. 4 gives a better selection of rpms,
> meaning at the same speed you can cruise with lower rpms, assuming the
> same rear axle ratio.
>
> Also I understand that 5-speeds don't have a torque converter that
> autos have which robbs some power.
>
> But in my experience, in city driving, it's hard to shift well for good
> MPG. Maybe I am shifting at wrong rpms, I am not sure.

Two big unknowns prevent making a flat statement:

Does the driver know how to drive a stick shift to maximize milage.
Is the test in town or on the road.

"Don Stauffer" > wrote in message
...
> * wrote:
> >
> > Computer-controlled transmissions can now shift gears at exactly the
> > correct moment......
> >
> > If it is fuel mileage I'm looking for, I'll take an automatic over a
stick.
> >
> >
> >
>
> No way! We traded in a Voyager stick for a new Chrysler van. The auto
> in the new one shifts at WAY higher rpm than we did with the old one,
> and we get nowhere the milage. You can short shift a stick- newer ones
> with computer control, you can't even FORCE an upshift! And the
> computer wants to supply AVERAGE driving program. If I knew how to redo
> programming I would.
>
> Anyone know if the dealer shop can alter the shift point?

Most Chrysler minivan sticks were on the short wheelbase 2.5L you have
a 3.8L in a long wheelbase there now that weighs a hell of a lot more.
If you had a stick on there you would get even worse mileage.

Ted

"Mike Romain" > wrote in message
...
> Don Stauffer wrote:
> >
> Also, when you see a light ahead, shift into
> > neutral and coast. Yeah, it is illegal in many states, but those laws
> > were written when brakes were primitive and gas was a quarter a gallon.
> >
>
> I just don't get idiots that come onto a world wide web boasting about
> doing highly illegal and deadly practices while saying 'forget what they
> used to say', it's cool now to go out of control and potentially kill
> yourself or others....
>

I didn't realize that when you shifted into neutral that your brakes
stopped working.

I'll cite another ancedotal study I can't find right now, they did a
study of accidents, out of the 200+ or so they found only 5 where
the driver would have been better off accellerating in an attempt
to avoid a collision. All others it made no difference or the driver
would have been a lot better off braking harder.

The idea that you lose control in neutral is baloney. You still have
steering and brakes, and in most collisions I've seen there was plenty
of room for the drivers to swerve to avoid. They call it taking
evasive action. The problem is that most drivers in the few seconds
before a collision happens, freeze up and do not steer away from
the impending collision, and as a result many collisions happen that
wouldn't have happened at all had the driver swerved.

Particularly in city driving when the car is seldom above 35Mph, the
idea that your going to be able to downshift during a deaccelleration from
35Mph to 0Mph, and be able to suddenly power out of the way of
an impending collision, is poppycock. The engine is not going to be
in the right gear to be able to punch it and power out of a collision.

Ted

Don Stauffer wrote:
> SQ wrote:
>
>> Assuming an identical car, let's say a 4-cyl Honda or a Subaru or
>> Toyota, which would
>> get better MPG -- one with automatic tranny or 5-speed?
>>
>> I understand that 5 speeds vs. 4 gives a better selection of rpms,
>> meaning at the same speed you can cruise with lower rpms, assuming the
>> same rear axle ratio.
>>
>> Also I understand that 5-speeds don't have a torque converter that
>> autos have which robbs some power.
>>
>> But in my experience, in city driving, it's hard to shift well for good
>> MPG. Maybe I am shifting at wrong rpms, I am not sure.
>>
>
>
> Not hard at all. Forget what they said in olden days about not lugging
> the engine. Shift early- if the car WON'T accelerate, then you shifted
> too soon. But if it accelerates smoothly, even though leisurely, that is
> fine. Even though my Neon R/T has a fairly agressive camshaft(s), I can
> shift below 2K, and it will be smooth with no shudder, though it is a
> leisurely acceleration. Also, when you see a light ahead, shift into
> neutral and coast. Yeah, it is illegal in many states, but those laws
> were written when brakes were primitive and gas was a quarter a gallon.
>
> There was a study in the late seventies by a European mfg. I think it
> was VW. They ran two cars on test trac for 100K miles, or some long
> distance. They lugged one car, drove other without lugging them. When
> they tore them down to look at crank, no discernable difference. I wish
> I could remember the mag I read about this test in, but I cannot (it was
> about 1980). Anyway, it altered my driving habits.


I don't like that. 'lugging' the engine is what happens when you shift
too soon. YOu need to shift soon enough to balance the acceleration you
get after the shift with overdriving in the gear you are shifting from.
Don't shift ASAP. That just waste gas.



--
Thank you,



"Then said I, Wisdom [is] better than strength: nevertheless the poor
man's wisdom [is] despised, and his words are not heard." Ecclesiastes 9:16