Assuming I’ve reached my cruising speed, and I don’t need extra power
for passing, is it always better to upshift? RPMs always decrease so I
assume it saves fuel, but would driving at 35 MPH in 5th put any
unnecessary strain on my engine? Any other side effects?
=====================================================================
Chris J. Kirsanoff "Every time I learn something new,
Univ. of Illinois it pushes some old stuff
chr…@uiuc.edu out of my brain." — Homer Simpson
=====================================================================
In a previous article, chr…@uiuc.edu (Chris Kirsanoff) says:
>Assuming I’ve reached my cruising speed, and I don’t need extra power
>for passing, is it always better to upshift? RPMs always decrease so I
>assume it saves fuel, but would driving at 35 MPH in 5th put any
>unnecessary strain on my engine? Any other side effects?
Learn what is the torque range of your engine and maintain RPM levels that
neither allow lugging nor higher revving than necessary. Most engines run
out of useful power well before RPM. 35 MPH in 5th gives me about 2000
RPM in my 86 Honda Prelude, which is fine with me. You will have to test
what your car can handle.
Bye,
—
-Darren Mallette: Ottawa, Ontario, Canada!
Congratulations to Jeff Gordon & Team Dupont for an outstanding drive in the
Inaugural Brickyard 400 at the Indianapolis Motor Speedway. I was THERE!
In article <34geb2$…@vixen.cso.uiuc.edu> chr…@uiuc.edu (Chris Kirsanoff)
writes:
> Assuming I’ve reached my cruising speed, and I don’t need extra power
> for passing, is it always better to upshift?
It depends on the circumstances. For example, if you’re going even
slightly uphill, it might be better to stay in the lower gear. Also,
it probably isn’t a good idea to upshift more than one gear even if
you’re just maintaining a steady speed.
> RPMs always decrease so I assume it saves fuel, but would driving
> at 35 MPH in 5th put any unnecessary strain on my engine?
Yes, it would. Here’s an analogy: You’ve probably ridden a ten-
speed bicycle and noticed how hard it is to pedal if you upshift
too far for your current speed. Well, you’re essentially the
"engine" of your bicycle, right? It makes just as much sense
to limit stress on your car’s drivetrain by selecting a gear that’s
appropriate to conditions as it does to limit stress on your
leg muscles by doing the same on a bike.
All cars are different, of course, but in general, it’s a good
idea to always try to keep your engine speed above 2000-2500
and 3000-3500 RPM while cruising. That way you’re neither
lugging it nor overrevving it.
Geoff
–
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Geoff Miller + + + + + + + + Mountain View
geo…@netcom.com + DoD #0996 + California
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In article <Cvoq21….@freenet.carleton.ca>,
Darren Mallette <ab…@FreeNet.Carleton.CA> wrote:
>Learn what is the torque range of your engine and maintain RPM levels that
>neither allow lugging nor higher revving than necessary. Most engines run
>out of useful power well before RPM. 35 MPH in 5th gives me about 2000
>RPM in my 86 Honda Prelude, which is fine with me. You will have to test
>what your car can handle.
35 mph in 5th at 2000 revs? That’s 4000 revs at 70 mph! My old four speed
would do that in top. My current car will be doing 50mph at 2000 revs in 5th.
Do you find yourself contantly changing gear or do you just use first,third
and fifth?
Steve
In a previous article, S.G.Adder…@ukc.ac.uk (sga1) says:
>35 mph in 5th at 2000 revs? That’s 4000 revs at 70 mph! My old four speed
>would do that in top. My current car will be doing 50mph at 2000 revs in 5th.
>Do you find yourself contantly changing gear or do you just use first,third
>and fifth?
>Steve
Ooops, that should be 42 MPH in 5th at 2000 RPM. I messed up converting
from km/h. I use each gear, shifting between 3000 and 3500 RPM in each,
until I reach cruising speed of about 70-80 MPH in 5th @ 3200-3500 RPM.
Sorry about the confusion,
—
-Darren Mallette: Ottawa, Ontario, Canada!
Congratulations to Jeff Gordon & Team Dupont for an outstanding drive in the
Inaugural Brickyard 400 at the Indianapolis Motor Speedway. I was THERE!
- Hide quoted text — Show quoted text -
In article <geoffmCvoysn….@netcom.com>, <geo…@netcom.com> writes:
> In article <34geb2$…@vixen.cso.uiuc.edu> chr…@uiuc.edu (Chris Kirsanoff)
> writes:
> > Assuming I’ve reached my cruising speed, and I don’t need extra power
> > for passing, is it always better to upshift? ……
> > RPMs always decrease so I assume it saves fuel, but would driving
> > at 35 MPH in 5th put any unnecessary strain on my engine?
> Snip
> All cars are different, of course, but in general, it’s a good
> idea to always try to keep your engine speed above 2000-2500
> and 3000-3500 RPM while cruising. That way you’re neither
> lugging it nor overrevving it.
It really does depend on the car/engine/gearing combination. A V8 in a
mustang/camaro.corvette etc will be much happier at the lower end of you range.
In fact a V8 will most lilely not really need to be revved much above 3,000
unless you are really interested in maximum acceleration. I drive a ford
pick-up (i know it isn’t a car) with a 5.0L and it is very happy if i upshift
at 2000 to 2500 and has strong power at 1500 rpm. I don’t think there is a big
difference in the power chaecteristics compared to a *car* version of the same
engine. My truck is not particularly low geard, 5th is an overdrive and it has
a 3.55 differential so 75mph cruising equates to 2400-2500 rpm, and 60mph drops
it to about 2000 rpm.
Sooo it realy depends on the particular vehicle. My father drives a buick
roadmaster (with a tach???:-)) with a 5.7l and it cruises at 70 mph at about
1600 rpm.
Jim Kastenholz
geo…@netcom.com (Justin Cayce) writes:
>> RPMs always decrease so I assume it saves fuel, but would driving
>> at 35 MPH in 5th put any unnecessary strain on my engine?
>Yes, it would. Here’s an analogy: You’ve probably ridden a ten-
>speed bicycle and noticed how hard it is to pedal if you upshift
>too far for your current speed. Well, you’re essentially the
>"engine" of your bicycle, right? It makes just as much sense
>to limit stress on your car’s drivetrain by selecting a gear that’s
>appropriate to conditions as it does to limit stress on your
>leg muscles by doing the same on a bike.
>All cars are different, of course, but in general, it’s a good
>idea to always try to keep your engine speed above 2000-2500
>and 3000-3500 RPM while cruising. That way you’re neither
>lugging it nor overrevving it.
I couldn’t disagree more. The stress on the drivetrain is governed
by the speed of the car, and the amount of force slowing the car down. The
drivetrain must transmit exactly that amount of force (assuming your not
accelerating) regardless of what gear you are in or what speed your engine is
cranking at. By running in the higher gear, even if RPM’s drop to below 2000
you only benefit. First of all you will be running at a more open throttle,
leading to less pumping losses and higher efficiency. Secondly, by running
at lower RPM’s you generate less heat, less noise, and in actuallity less
stress on your engine. The only reason not to "lug it" is if you want the
extra power for hills, passing, etc, otherwise keep it in the higher gear.
The reason your bike analogy doesn’t hold up is that an engine is
most efficient at lower speeds and wide open throttle (meaning maximum
force/torque for a given speed) whereas your body is most efficient using
smaller forces at higher speeds. This is evidenced by comparing marathon
runners with sprinters. Sprinters burn up all their stored energy in the
initial 100 or so meters because they are exerting their maximum force.
Marathon runners use considerably less force, and are able to run much longer
distances because of the increased efficiency in this mode of operation.
(to qualify this, I want to say, without trying to sound uppity, that this
is based on science and not heresay. I am a graduate student who specializes
in engines and combustion, and who formerly worked as a powertrain engineer
for GM Saturn.)
Ashok Tripathi
"Less government is better government. Let the drivers set the speed limits."
In article l…@gap.cco.caltech.edu, tripa…@cco.caltech.edu (Ashok B. Tripathi) writes:
- Hide quoted text — Show quoted text -
>geo…@netcom.com (Justin Cayce) writes:
>>> RPMs always decrease so I assume it saves fuel, but would driving
>>> at 35 MPH in 5th put any unnecessary strain on my engine?
>>Yes, it would. Here’s an analogy: You’ve probably ridden a ten-
>>speed bicycle and noticed how hard it is to pedal if you upshift
>>too far for your current speed. Well, you’re essentially the
>>"engine" of your bicycle, right? It makes just as much sense
>>to limit stress on your car’s drivetrain by selecting a gear that’s
>>appropriate to conditions as it does to limit stress on your
>>leg muscles by doing the same on a bike.
>>All cars are different, of course, but in general, it’s a good
>>idea to always try to keep your engine speed above 2000-2500
>>and 3000-3500 RPM while cruising. That way you’re neither
>>lugging it nor overrevving it.
> I couldn’t disagree more. The stress on the drivetrain is governed
>by the speed of the car, and the amount of force slowing the car down.
The stress on everything on the input side of the transmission (eg.
pistons, wristpins, connecting rods, crankshaft, main bearings, flywheel,
clutch/torque converter, and input shaft,) is governed by the torque the
engine is producing.
>The
>drivetrain must transmit exactly that amount of force (assuming your not
>accelerating) regardless of what gear you are in or what speed your engine is
>cranking at.
Correct. To maintain speed, it takes a certain amount of power to overcome
the forces of friction trying to slow the car down. Since power is equal
to torque*RPM, you can utilize a high percentage of the engine’s torque
capability and a low RPM, or a low torque capability and a high RPM.
>By running in the higher gear, even if RPM’s drop to below 2000
>you only benefit.
Keep in mind that you *must* use more torque in this situation.
> First of all you will be running at a more open throttle,
>leading to less pumping losses and higher efficiency. Secondly, by running
>at lower RPM’s you generate less heat, less noise, and in actuallity less
>stress on your engine.
Wrong. Stress will increase because the engine is operating at a higher
torque requirement than at at higher RPMS. MORE energy has to be exerted
with each power stroke of the piston to maintain the power necessary to
move the vehicle..
> The only reason not to "lug it" is if you want the
>extra power for hills, passing, etc, otherwise keep it in the higher gear.
Actually, you’ll generally have more horsepower at higher RPMS because of
the way the mathematics works out. HP peaks a few hundred RPMS after torque
does. Why do you think engines downshift to pass?
> The reason your bike analogy doesn’t hold up is that an engine is
>most efficient at lower speeds and wide open throttle (meaning maximum
>force/torque for a given speed) whereas your body is most efficient using
>smaller forces at higher speeds.
But efficiency doesn’t enter into the argument. when your comparing the
stress on an engine running at 2000 RPM to an engine running at 3500 RPM,
efficiency doesn’t matter.
> This is evidenced by comparing marathon
>runners with sprinters. Sprinters burn up all their stored energy in the
>initial 100 or so meters because they are exerting their maximum force.
>Marathon runners use considerably less force, and are able to run much longer
>distances because of the increased efficiency in this mode of operation.
>(to qualify this, I want to say, without trying to sound uppity, that this
>is based on science and not heresay. I am a graduate student who specializes
>in engines and combustion, and who formerly worked as a powertrain engineer
>for GM Saturn.)
Really? I guess I better not buy a Saturn then!
(I must mention that I’m not an automotive engineer, just a drag racer :-> )
—
+———————————————————————–+
| Robert A. King | |
| Systems Software Engineer | |
| Kodak Health Imaging Systems | "I drank WHAT?!?" — Socrates |
| | |
| k…@khan.khis.com | |
+———————————————————————–+
| The opinions expressed here arn’t even mine, much less my employer’s! |
+———————————————————————–+
>Rear A/C seems helpful, foldup rear seats seem handy (no need to
>store ‘em), comfortable drive, lots o’ space.
Previa doesnot have rear AC. Just a fan behind the
driver’s seat.
>Principal bummers – high price
Yes, what a bummer. They are 15% higher than rivals.
>small engine.
It pushes the van to 110mph. But the power is not enough
to fit this van in American road.
> space
Its strongest point.
Chung Lu (chun…@bnr.ca) wrote:
: >Principal bummers – high price
: Yes, what a bummer. They are 15% higher than rivals.
Yes, but think of the anvil-like reputation Toyota has for quality
service and reliability. My parents have a burgundy LE, one of my bosses
has a sky-blue LE, and a friend just got a new AWD — They are certainly
not unhappy with their choices. Sometimes you just gotta pay more to get
the best. (Yes, your subjective on qhat constitutes "best" may vary.)
: >small engine.
: It pushes the van to 110mph. But the power is not enough
: to fit this van in American road.
A concern that is eradicated in the new Supercharged Previa. See a recent
issue of Car and Driver for details… Hmmmmm, I’ve forgotten just which
month.
Nhat-Viet Phi
nhatv…@nucleus.com
Calgary, Alberta
Nhat-Viet Phi (nhatv…@nucleus.com) wrote:
: Chung Lu (chun…@bnr.ca) wrote:
: : >Principal bummers – high price
: : Yes, what a bummer. They are 15% higher than rivals.
: Yes, but think of the anvil-like reputation Toyota has for quality
: service and reliability. My parents have a burgundy LE, one of my bosses
: has a sky-blue LE, and a friend just got a new AWD — They are certainly
: not unhappy with their choices. Sometimes you just gotta pay more to get
: the best. (Yes, your subjective on qhat constitutes "best" may vary.)
: : >small engine.
: : It pushes the van to 110mph. But the power is not enough
: : to fit this van in American road.
: A concern that is eradicated in the new Supercharged Previa. See a recent
: issue of Car and Driver for details… Hmmmmm, I’ve forgotten just which
: month.
: Nhat-Viet Phi
: nhatv…@nucleus.com
: Calgary, Alberta
I’m sorry, but $35,000+ for a Toyota van is just too much (especially for
one that looks like an egg!). You need AWD for decent wet- and
snow-covered roads. And it’s very difficult to walk between the front
seats into the rear compartment due to the below-floor engine placement.
In article <Cw0By5….@nucleus.com>, nhatv…@nucleus.com (Nhat-Viet Phi) writes:
> Chung Lu (chun…@bnr.ca) wrote:
> : >Principal bummers – high price
> : Yes, what a bummer. They are 15% higher than rivals.
> Yes, but think of the anvil-like reputation Toyota has for quality
> service and reliability. My parents have a burgundy LE, one of my bosses
> has a sky-blue LE, and a friend just got a new AWD — They are certainly
> not unhappy with their choices. Sometimes you just gotta pay more to get
> the best. (Yes, your subjective on qhat constitutes "best" may vary.)
Hi, Toyota fan. I agree with you. So are those Mercedes and Luxas owners.
How many Quest/Villager do you see before you see one Previa.
How many Camry/Accord do you see before you see one 300E.
Japanese car maker start by offer better car which costs less.
When they build up their image they start to charge. See what
happen to them:
Toyota: MR 2, Supra, Luxas GS 300
Honda: CRX Del Sel, Acura Vigor, NSX
Mazda: RX-7
Those are all good cars. They just charged too much for them.
What we want are "better valued" cars like:
Honda: Civic, Mazda: miata … let me stop here.
> : >small engine.
> A concern that is eradicated in the new Supercharged Previa. See a recent
> issue of Car and Driver for details… Hmmmmm, I’ve forgotten just which
> month.
Again, money issue. I have hard time spending more than $30K for it while
others cost only half. Previa is nice, but not twice better.
I am looking for a basic car that will get me up and back to work.
I am thinking f purchasing a geo metro- I’d appreicate any thoughts
in this regard (what is a good price for a basic version- no air, manual…?)
Any other models/brands I may wish to consider?
Thanks
Martin
p.s. please e-mail your reply to me