Home » Public Forums » GMCnet » [GMCnet] Max torque/max RPM
| [GMCnet] Max torque/max RPM [message #157277] |
Thu, 19 January 2012 12:06  |
enate98690
Messages: 23
Registered: January 2012
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Hi,I have a '73 GMC with an unmodified Olds 455 in it. Does anyone know at what RPM this engine reaches its maximum torque?
Also, does anyone know what the engine's "redline" (maximum RPM the engine can safely reach) is?
At least on my engine, it kind of seems right now that the engine torque curve drops off fairly significantly so that reaching "redline" is pretty hard. However, I'm not sure.
Any information would be appreciated!
Thanks,
Keith Lee (SF, CA)
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| Re: [GMCnet] Max torque/max RPM [message #157279 is a reply to message #157277] |
Thu, 19 January 2012 12:23  |
Gary Worobec
Messages: 867
Registered: May 2005
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On my '73 between 2800 and 3000 seems best for overall torque and mpg. My
engine rarely sees over 3200 so I can't comment on redline. I changed to a
3.55 diff which puts it right in that range at highway speeds with enough
torque that if I can keep it in the range hills even while towing are no
problem. I do have a 23 which weighs a ton less than a 26.
Thanks
Gary and Joanne Worobec
1973 GMC Glacier
Anza, CA
----- Original Message -----
From: <enate98690@mypacks.net>
To: <gmclist@temp.gmcnet.org>
Sent: Thursday, January 19, 2012 10:06 AM
Subject: [GMCnet] Max torque/max RPM
> Hi,I have a '73 GMC with an unmodified Olds 455 in it. Does anyone know
> at what RPM this engine reaches its maximum torque?
>
> Also, does anyone know what the engine's "redline" (maximum RPM the engine
> can safely reach) is?
>
> At least on my engine, it kind of seems right now that the engine torque
> curve drops off fairly significantly so that reaching "redline" is pretty
> hard. However, I'm not sure.
> Any information would be appreciated!
> Thanks,
> Keith Lee (SF, CA)
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Max torque/max RPM [message #157285 is a reply to message #157277] |
Thu, 19 January 2012 13:08 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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On Jan 19, 2012, at 11:06 AM, enate98690@mypacks.net wrote:
> Hi,I have a '73 GMC with an unmodified Olds 455 in it. Does anyone know at what RPM this engine reaches its maximum torque?
>
> Also, does anyone know what the engine's "redline" (maximum RPM the engine can safely reach) is?
>
> At least on my engine, it kind of seems right now that the engine torque curve drops off fairly significantly so that reaching "redline" is pretty hard. However, I'm not sure.
> Any information would be appreciated!
> Thanks,
> Keith Lee (SF, CA)
I had once gotten some info from Dick Paterson and passed it on to Billy Massey who posted it to his site. http://www.bdub.net/OldsEngineSpecs.pdf
Page 2 has the hp and torque figures.
Torque is a measured value. Horsepower is a computed value using the relationship between rpm and torque. The peak torque occurs at a different RPM than the peak HP. More info on that is available in an article I wrote several years back which is posted on the GMCWS site: http://www.gmcws.org/techcenter/01-03tc32.html
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Max torque/max RPM [message #157333 is a reply to message #157277] |
Thu, 19 January 2012 17:34 |
enate98690
Messages: 23
Registered: January 2012
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Thank you for your prompt response, Emery.
Sincerely,
Keith
-----Original Message-----
>From: Emery Stora <emerystora@mac.com>
>Sent: Jan 19, 2012 11:08 AM
>To: gmclist@temp.gmcnet.org
>Subject: Re: [GMCnet] Max torque/max RPM
>
>
>On Jan 19, 2012, at 11:06 AM, enate98690@mypacks.net wrote:
>
>> Hi,I have a '73 GMC with an unmodified Olds 455 in it. Does anyone know at what RPM this engine reaches its maximum torque?
>>
>> Also, does anyone know what the engine's "redline" (maximum RPM the engine can safely reach) is?
>>
>> At least on my engine, it kind of seems right now that the engine torque curve drops off fairly significantly so that reaching "redline" is pretty hard. However, I'm not sure.
>> Any information would be appreciated!
>> Thanks,
>> Keith Lee (SF, CA)
>
>
>I had once gotten some info from Dick Paterson and passed it on to Billy Massey who posted it to his site. http://www.bdub.net/OldsEngineSpecs.pdf
>Page 2 has the hp and torque figures.
>
>Torque is a measured value. Horsepower is a computed value using the relationship between rpm and torque. The peak torque occurs at a different RPM than the peak HP. More info on that is available in an article I wrote several years back which is posted on the GMCWS site: http://www.gmcws.org/techcenter/01-03tc32.html
>
>Emery Stora
>77 Kingsley
>Santa Fe, NM
>
>
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>Unsubscribe or Change List Options:
>http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Max torque/max RPM [message #157354 is a reply to message #157285] |
Thu, 19 January 2012 21:02 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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Emery--I do think you wrote a very nice article about this but I seriously disagree with a basic idea and that is this: First I want to tell you that horsepower is not important to a GMC owner. Torque is important. We constantly hear and read about these numbers, but what exactly are they? What are those numbers at various rpm (rotations per minute) really representing and how do you know what is going to be right for your application?
one ""
It is just the opposite. HP is work and torque is not. You can't move one inch with torque alone. You need power, and that is what horsepower is all about. The correct argument and analyses is how and where you want torque distributed. Lot's of torque may seem great, but if it is in the wrong spot, it will do no good. On the surface it may seem great to have a lot of torque at low RPM but that is not necessarily true at all. Many people have been talked into lower final drive ratios by this argument and it may be an injustice. The correct answer is determined by driving style and ratio spread. In many cases a 3.07 in second gear is better than a 3.55 in 3rd. The "torque is all that matters" is a total misunderstanding of how powertrains operate.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Max torque/max RPM [message #157357 is a reply to message #157354] |
Thu, 19 January 2012 21:20 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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On Jan 19, 2012, at 8:02 PM, Bob de Kruyff wrote:
>
>
> Emery--I do think you wrote a very nice article about this but I seriously disagree with a basic idea and that is this: First I want to tell you that horsepower is not important to a GMC owner. Torque is important. We constantly hear and read about these numbers, but what exactly are they? What are those numbers at various rpm (rotations per minute) really representing and how do you know what is going to be right for your application?
> one ""
> It is just the opposite. HP is work and torque is not. You can't move one inch with torque alone. You need power, and that is what horsepower is all about. The correct argument and analyses is how and where you want torque distributed. Lot's of torque may seem great, but if it is in the wrong spot, it will do no good. On the surface it may seem great to have a lot of torque at low RPM but that is not necessarily true at all. Many people have been talked into lower final drive ratios by this argument and it may be an injustice. The correct answer is determined by driving style and ratio spread. In many cases a 3.07 in second gear is better than a 3.55 in 3rd. The "torque is all that matters" is a total misunderstanding of how powertrains operate.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
>
I guess that we will just have to disagree with each other.
Here is an excerpt from an artikcle that I just found on the net:
The Case For Torque
Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
Emery Stora
77 Kingsley
Santa Fe, NM
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| Re: [GMCnet] Max torque/max RPM [message #157359 is a reply to message #157357] |
Thu, 19 January 2012 21:29 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
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We will have to friendly disagree on that one since I think the article is bogus as well. Regardless, you are the best resource here bar none!
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: [GMCnet] Max torque/max RPM [message #157360 is a reply to message #157357] |
Thu, 19 January 2012 21:28 |
Kosier
Messages: 834
Registered: February 2008
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Any engine builder will tell you "Torque wins races, horsepower
sells motors". JMHO
Gary Kosier with a Caddy 500 that will suck the guts out of an
Olds 455!!!
----- Original Message -----
From: "Emery Stora" <emerystora@mac.com>
To: <gmclist@temp.gmcnet.org>
Sent: Thursday, January 19, 2012 10:20 PM
Subject: Re: [GMCnet] Max torque/max RPM
>
> On Jan 19, 2012, at 8:02 PM, Bob de Kruyff wrote:
>
>>
>>
>> Emery--I do think you wrote a very nice article about this but
>> I seriously disagree with a basic idea and that is this:
>> First I want to tell you that horsepower is not important to a
>> GMC owner. Torque is important. We constantly hear and read
>> about these numbers, but what exactly are they? What are those
>> numbers at various rpm (rotations per minute) really
>> representing and how do you know what is going to be right for
>> your application?
>> one ""
>> It is just the opposite. HP is work and torque is not. You
>> can't move one inch with torque alone. You need power, and
>> that is what horsepower is all about. The correct argument and
>> analyses is how and where you want torque distributed. Lot's
>> of torque may seem great, but if it is in the wrong spot, it
>> will do no good. On the surface it may seem great to have a
>> lot of torque at low RPM but that is not necessarily true at
>> all. Many people have been talked into lower final drive
>> ratios by this argument and it may be an injustice. The
>> correct answer is determined by driving style and ratio
>> spread. In many cases a 3.07 in second gear is better than a
>> 3.55 in 3rd. The "torque is all that matters" is a total
>> misunderstanding of how powertrains operate.
>> --
>> Bob de Kruyff
>> 78 Eleganza
>> Chandler, AZ
>>
>
> I guess that we will just have to disagree with each other.
>
> Here is an excerpt from an artikcle that I just found on the
> net:
>
> The Case For Torque
> Now, what does all this mean in carland?
>
> First of all, from a driver's perspective, torque, to use the
> vernacular, RULES :-). Any given car, in any given gear, will
> accelerate at a rate that *exactly* matches its torque curve
> (allowing for increased air and rolling resistance as speeds
> climb). Another way of saying this is that a car will
> accelerate hardest at its torque peak in any given gear, and
> will not accelerate as hard below that peak, or above it.
> Torque is the only thing that a driver feels, and horsepower is
> just sort of an esoteric measurement in that context. 300 foot
> pounds of torque will accelerate you just as hard at 2000 rpm
> as it would if you were making that torque at 4000 rpm in the
> same gear, yet, per the formula, the horsepower would be
> *double* at 4000 rpm. Therefore, horsepower isn't particularly
> meaningful from a driver's perspective, and the two numbers
> only get friendly at 5252 rpm, where horsepower and torque
> always come out the same.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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| Re: [GMCnet] Max torque/max RPM [message #157385 is a reply to message #157357] |
Fri, 20 January 2012 06:53 |
jhbridges
Messages: 8412
Registered: May 2011
Location: Braselton ga
Karma: -74
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Senior Member |
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An Old NASCAR Poot once said in a conversation, the idea was to gear and setup such that the engine was kept in the 90% torque range. Plot the torque curve, and spot the low and high RPM at the 90% points... and keep it in that range. My GMC appears tro do this, so does the little Ranger pickup - and the toadstone does as well if you don't try to investigate the governor on it. Beyond noting this, the discussion become academic.Yall discuss, I'll read.
--johnny
'76 23' transmode norris
'76 palm beach
From: Emery Stora <emerystora@mac.com>
To: gmclist@temp.gmcnet.org
Sent: Thursday, January 19, 2012 10:20 PM
Subject: Re: [GMCnet] Max torque/max RPM
On Jan 19, 2012, at 8:02 PM, Bob de Kruyff wrote:
>
>
> Emery--I do think you wrote a very nice article about this but I seriously disagree with a basic idea and that is this: First I want to tell you that horsepower is not important to a GMC owner. Torque is important. We constantly hear and read about these numbers, but what exactly are they? What are those numbers at various rpm (rotations per minute) really representing and how do you know what is going to be right for your application?
> one ""
> It is just the opposite. HP is work and torque is not. You can't move one inch with torque alone. You need power, and that is what horsepower is all about. The correct argument and analyses is how and where you want torque distributed. Lot's of torque may seem great, but if it is in the wrong spot, it will do no good. On the surface it may seem great to have a lot of torque at low RPM but that is not necessarily true at all. Many people have been talked into lower final drive ratios by this argument and it may be an injustice. The correct answer is determined by driving style and ratio spread. In many cases a 3.07 in second gear is better than a 3.55 in 3rd. The "torque is all that matters" is a total misunderstanding of how powertrains operate.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
>
I guess that we will just have to disagree with each other.
Here is an excerpt from an artikcle that I just found on the net:
The Case For Torque
Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular, RULES :-). Any given car, in any given gear, will accelerate at a rate that *exactly* matches its torque curve (allowing for increased air and rolling resistance as speeds climb). Another way of saying this is that a car will accelerate hardest at its torque peak in any given gear, and will not accelerate as hard below that peak, or above it. Torque is the only thing that a driver feels, and horsepower is just sort of an esoteric measurement in that context. 300 foot pounds of torque will accelerate you just as hard at 2000 rpm as it would if you were making that torque at 4000 rpm in the same gear, yet, per the formula, the horsepower would be *double* at 4000 rpm. Therefore, horsepower isn't particularly meaningful from a driver's perspective, and the two numbers only get friendly at 5252 rpm, where horsepower and torque always come out the same.
Emery Stora
77 Kingsley
Santa Fe, NM
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Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell
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| Re: [GMCnet] Max torque/max RPM [message #157390 is a reply to message #157277] |
Fri, 20 January 2012 08:37 |
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RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
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I'm just an old Farmboy here... but my understanding of Torque is that it is a measurement of Force around an axis. You can hang a 500lb weight on a cable wrapped around a 1foot radius drum and you'd be exerting 500ft-lbs of torque, but that is static, there is no work being done until the drum starts to wind the cable in.
Horsepower is Force x distance in a period of time (velocity)
One turn of the drum would lift the 500lb weight 6.28ft.
If you applied the 500ft-lb torque on the drum turning it one revolution in one minute it would require a certain amount of power (fraction of a HP)
If you wanted to raise it twice as high, it would take twice as much HP to do it. Torque would not change (assuming a constant velocity) but the rate of doing the work has doubled.
Through gear reduction you can take a small motor and get a tremendous amount of torque, but the velocity will be very low. You could make a lawn mower engine move a train... there's lots of torque! but your top speed might be 10ft per day!
So you can have torque without movement but is no power.
I would disagree then that torque wins races. Torque that can be applied at a great rate of speed = Horsepower.
The gas engine doesn't have constant torque across all RPM's. It builds to a peak at a certain RPM then starts to fall. However it doesn't fall off quickly as the RPM climbs so the Torque x speed (RPM) = HP continues to climb the point where Torque starts to drop off faster and that is the peak HorsePower.
So my take is you can make lots of torque, but if you can't apply it at the required rate (speed) you've got no power and you're not going anywhere!
That's just my take on it. I don't know all the proper terms formulas so please don't flame me, but Google can find those.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
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| Re: [GMCnet] Max torque/max RPM [message #157394 is a reply to message #157385] |
Fri, 20 January 2012 10:25 |
 |
hnielsen2
Messages: 1434
Registered: February 2004
Location: Alpine CA
Karma: 0
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Senior Member |
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Works for me.
Max torque of 477.1 at 3100 RPM.
Last week I got all of this about H P.
I don't need no stinking H P to move our GMC.
As some one said last week H P is about getting to the wall fast, torque is
about dragging the wall with you
Johnny I'm with you.
I'll just sit back and read
Thank You
Howard
Alpine CA
74 Canyon Lands
Not quite Stock
----- Original Message -----
From: "Johnny Bridges" <jhbridges@ymail.com>
To: <gmclist@temp.gmcnet.org>
Sent: Friday, January 20, 2012 04:53
Subject: Re: [GMCnet] Max torque/max RPM
An Old NASCAR Poot once said in a conversation, the idea was to gear and
setup such that the engine was kept in the 90% torque range. Plot the torque
curve, and spot the low and high RPM at the 90% points... and keep it in
that range. My GMC appears tro do this, so does the little Ranger pickup -
and the toadstone does as well if you don't try to investigate the governor
on it. Beyond noting this, the discussion become academic.Yall discuss, I'll
read.
--johnny
'76 23' transmode norris
'76 palm beach
On Jan 19, 2012, at 8:02 PM, Bob de Kruyff wrote:
>
>
> Emery--I do think you wrote a very nice article about this but I seriously
> disagree with a basic idea and that is this: First I want to tell you that
> horsepower is not important to a GMC owner. Torque is important. We
> constantly hear and read about these numbers, but what exactly are they?
> What are those numbers at various rpm (rotations per minute) really
> representing and how do you know what is going to be right for your
> application?
> one ""
> It is just the opposite. HP is work and torque is not. You can't move one
> inch with torque alone. You need power, and that is what horsepower is all
> about. The correct argument and analyses is how and where you want torque
> distributed. Lot's of torque may seem great, but if it is in the wrong
> spot, it will do no good. On the surface it may seem great to have a lot
> of torque at low RPM but that is not necessarily true at all. Many people
> have been talked into lower final drive ratios by this argument and it may
> be an injustice. The correct answer is determined by driving style and
> ratio spread. In many cases a 3.07 in second gear is better than a 3.55 in
> 3rd. The "torque is all that matters" is a total misunderstanding of how
> powertrains operate.
> --
> Bob de Kruyff
> 78 Eleganza
> Chandler, AZ
>
I guess that we will just have to disagree with each other.
Here is an excerpt from an artikcle that I just found on the net:
The Case For Torque
Now, what does all this mean in carland?
First of all, from a driver's perspective, torque, to use the vernacular,
RULES :-). Any given car, in any given gear, will accelerate at a rate that
*exactly* matches its torque curve (allowing for increased air and rolling
resistance as speeds climb). Another way of saying this is that a car will
accelerate hardest at its torque peak in any given gear, and will not
accelerate as hard below that peak, or above it. Torque is the only thing
that a driver feels, and horsepower is just sort of an esoteric measurement
in that context. 300 foot pounds of torque will accelerate you just as hard
at 2000 rpm as it would if you were making that torque at 4000 rpm in the
same gear, yet, per the formula, the horsepower would be *double* at 4000
rpm. Therefore, horsepower isn't particularly meaningful from a driver's
perspective, and the two numbers only get friendly at 5252 rpm, where
horsepower and torque always come out the same.
Emery Stora
77 Kingsley
Santa Fe, NM
_______________________________________________
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All is well with my Lord
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| Re: [GMCnet] Max torque/max RPM [message #157401 is a reply to message #157394] |
Fri, 20 January 2012 11:58 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I am gonna take a stab at this one, one time only. What we are discussing
here is work. The technical description of work is "Moving something by
applying a force to it" Work is often expressed as Force(effort) X
Distance. or F x D = W, often expressed in pounds/feet or foot pounds. The
rate of work being done adds the further dimension of time, as is foot
pounds per second, or foot pounds per minute. That is a description for
horsepower. There is a basic formula for the rate of work that one horse
can accomplish in one minute. I am going to NOT make this into a Math
lesson, but by measuring the load to be moved, and the rate that you wish
it to be accomplished, you can figure how much effort will be required to
accomplish this task. You can drive a GMC motorhome towing a 10,000 pound
load up a 30 degree slope that is 5000 feet tall with a 100 horsepower
engine. You just can not do it very quickly. If you double the effort
(horsepower) you can do it roughly twice as fast, but the same amount of
work is still being done. One of the basic fundamentals always applies. If
the lever is twice as long, it must move twice as far to do the same amount
of work, but the amount of work performed is the same. Like Mr Fisher says,
GMCs get 8 to 10 mpg.
Jim Hupy
Salem, OR
78 GMC Royale 403 ( with 3:70 final drive) yes it does help, a lot.
On Fri, Jan 20, 2012 at 8:25 AM, Howard and Sue <hnielsen2@cox.net> wrote:
> Works for me.
> Max torque of 477.1 at 3100 RPM.
> Last week I got all of this about H P.
> I don't need no stinking H P to move our GMC.
> As some one said last week H P is about getting to the wall fast, torque is
> about dragging the wall with you
> Johnny I'm with you.
> I'll just sit back and read
> Thank You
> Howard
> Alpine CA
> 74 Canyon Lands
> Not quite Stock
>
> ----- Original Message -----
> From: "Johnny Bridges" <jhbridges@ymail.com>
> To: <gmclist@temp.gmcnet.org>
> Sent: Friday, January 20, 2012 04:53
> Subject: Re: [GMCnet] Max torque/max RPM
>
>
> An Old NASCAR Poot once said in a conversation, the idea was to gear and
> setup such that the engine was kept in the 90% torque range. Plot the
> torque
> curve, and spot the low and high RPM at the 90% points... and keep it in
> that range. My GMC appears tro do this, so does the little Ranger pickup -
> and the toadstone does as well if you don't try to investigate the governor
> on it. Beyond noting this, the discussion become academic.Yall discuss,
> I'll
> read.
>
> --johnny
> '76 23' transmode norris
> '76 palm beach
>
>
>
> On Jan 19, 2012, at 8:02 PM, Bob de Kruyff wrote:
>
> >
> >
> > Emery--I do think you wrote a very nice article about this but I
> seriously
> > disagree with a basic idea and that is this: First I want to tell you
> that
> > horsepower is not important to a GMC owner. Torque is important. We
> > constantly hear and read about these numbers, but what exactly are they?
> > What are those numbers at various rpm (rotations per minute) really
> > representing and how do you know what is going to be right for your
> > application?
> > one ""
> > It is just the opposite. HP is work and torque is not. You can't move one
> > inch with torque alone. You need power, and that is what horsepower is
> all
> > about. The correct argument and analyses is how and where you want torque
> > distributed. Lot's of torque may seem great, but if it is in the wrong
> > spot, it will do no good. On the surface it may seem great to have a lot
> > of torque at low RPM but that is not necessarily true at all. Many people
> > have been talked into lower final drive ratios by this argument and it
> may
> > be an injustice. The correct answer is determined by driving style and
> > ratio spread. In many cases a 3.07 in second gear is better than a 3.55
> in
> > 3rd. The "torque is all that matters" is a total misunderstanding of how
> > powertrains operate.
> > --
> > Bob de Kruyff
> > 78 Eleganza
> > Chandler, AZ
> >
>
> I guess that we will just have to disagree with each other.
>
> Here is an excerpt from an artikcle that I just found on the net:
>
> The Case For Torque
> Now, what does all this mean in carland?
>
> First of all, from a driver's perspective, torque, to use the vernacular,
> RULES :-). Any given car, in any given gear, will accelerate at a rate that
> *exactly* matches its torque curve (allowing for increased air and rolling
> resistance as speeds climb). Another way of saying this is that a car will
> accelerate hardest at its torque peak in any given gear, and will not
> accelerate as hard below that peak, or above it. Torque is the only thing
> that a driver feels, and horsepower is just sort of an esoteric measurement
> in that context. 300 foot pounds of torque will accelerate you just as hard
> at 2000 rpm as it would if you were making that torque at 4000 rpm in the
> same gear, yet, per the formula, the horsepower would be *double* at 4000
> rpm. Therefore, horsepower isn't particularly meaningful from a driver's
> perspective, and the two numbers only get friendly at 5252 rpm, where
> horsepower and torque always come out the same.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
>
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| Re: [GMCnet] Max torque/max RPM [message #157409 is a reply to message #157277] |
Fri, 20 January 2012 13:42 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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Ok,
Let's get this straight.
As someone already posted HP=Torque*RPM/5252 that is all there is to that. You can't have one without the other.
What makes an engine easy to use is a combination of the area under the torque curve - this creates "driveabiltiy" and the slope of this curve after the torque peak - this is called backup torque and it is the amount you don't have to downshift to climb the hill.
If torque was all that mattered, everything would be powered by reciprocating steam engines - Maximum torque at zero speed. No multi-speed transmission would be needed.
If horsepower was the answer, then everything with an internal combustion engine would have a minimum crankshaft speed of 6000~10000RPM. (And, a 15 speed transmission.)
In short, as long as the horsepower is available, it can be converted to the required torque with gears. This is what those transmissions do. This is why JimK sells different final drives.
Lots of new vehicles have lots of horsepower and 6, 9 (11 or 15 -just kidding - today) speed transmissions. Why, because variable speed engines are hard to make efficient - even with variable cam timing and all the modern magic.
Did you ever have something with a tiny motor (>125cc)? If you let it get of the power band (peak), it was all done.
Same ~~ Same.
I used to have a 100cc bike that was dynoed at 18.2HP. The jolt when I throttled up was an adrenalin rush, but it was almost unrideable. (A friend described it as backordered horsepower delivered all as once.) I did some work to the engine/pipe and got it to 16.5HP. But, now the 90% torque peak was more than three times wider. It was then a winning ride. It was still exciting, but no longer terrifying.
It is horsepower that does all the work but, if the band over which it is available is too narrow, it make it very difficult to used it effectively.
Look at the power output of an turbo-shaft power unit (like a aircraft) that does not have an output gear box. It has nearly no torque at all, but it has it at 30kRPM. Add some gear reduction and now we have power for powerplants and ships.
The cards that came in my coach say that the 455 installed is good for 265HP. That is fine with me. I still end up having to back off my throttle because the little car in front of me isn't out pulling me. No, I've never done one of the western grades, but I have been down with the trucks in the Appalachians.
So, everything is a compromise.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Max torque/max RPM [message #157410 is a reply to message #157409] |
Fri, 20 January 2012 13:56 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
|
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Matt, It is kinda like five blindfolded guys looking at an elephant. One
holding the tusk, one with his hands on the sides, one on the trunk, and so
on. None of them are willing to remove the blindfold and look at the
elephant, thus getting the complete picture. They all have a somewhat
narrow viewpoint, perhaps because of their proximity to the elephant. Stand
back, observe, smell, taste, listen, feel, and you get the whole picture.
None of them are either right or wrong, just UNDERINFORMED. Same deal with
torque and horsepower. Ya gotta see the whole critter before it makes any
sense.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Jan 20, 2012 at 11:42 AM, Matt Colie <matt7323tze@gmail.com> wrote:
>
>
> Ok,
> Let's get this straight.
> As someone already posted HP=Torque*RPM/5252 that is all there is to
> that. You can't have one without the other.
>
> What makes an engine easy to use is a combination of the area under the
> torque curve - this creates "driveabiltiy" and the slope of this curve
> after the torque peak - this is called backup torque and it is the amount
> you don't have to downshift to climb the hill.
>
> If torque was all that mattered, everything would be powered by
> reciprocating steam engines - Maximum torque at zero speed. No multi-speed
> transmission would be needed.
>
> If horsepower was the answer, then everything with an internal combustion
> engine would have a minimum crankshaft speed of 6000~10000RPM. (And, a 15
> speed transmission.)
>
> In short, as long as the horsepower is available, it can be converted to
> the required torque with gears. This is what those transmissions do. This
> is why JimK sells different final drives.
>
> Lots of new vehicles have lots of horsepower and 6, 9 (11 or 15 -just
> kidding - today) speed transmissions. Why, because variable speed engines
> are hard to make efficient - even with variable cam timing and all the
> modern magic.
>
> Did you ever have something with a tiny motor (>125cc)? If you let it get
> of the power band (peak), it was all done.
> Same ~~ Same.
>
> I used to have a 100cc bike that was dynoed at 18.2HP. The jolt when I
> throttled up was an adrenalin rush, but it was almost unrideable. (A
> friend described it as backordered horsepower delivered all as once.) I
> did some work to the engine/pipe and got it to 16.5HP. But, now the 90%
> torque peak was more than three times wider. It was then a winning ride.
> It was still exciting, but no longer terrifying.
>
> It is horsepower that does all the work but, if the band over which it is
> available is too narrow, it make it very difficult to used it effectively.
>
> Look at the power output of an turbo-shaft power unit (like a aircraft)
> that does not have an output gear box. It has nearly no torque at all, but
> it has it at 30kRPM. Add some gear reduction and now we have power for
> powerplants and ships.
>
> The cards that came in my coach say that the 455 installed is good for
> 265HP. That is fine with me. I still end up having to back off my
> throttle because the little car in front of me isn't out pulling me. No,
> I've never done one of the western grades, but I have been down with the
> trucks in the Appalachians.
>
> So, everything is a compromise.
>
> Matt
> --
> Matt & Mary Colie
> '73 Glacier 23 Chaumière (say show-me-air) Just about as stock as you will
> find
> SE Michigan - Twixt A2 and Detroit
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Max torque/max RPM [message #157411 is a reply to message #157277] |
Fri, 20 January 2012 14:09 |
Gary Casey
Messages: 448
Registered: September 2009
Karma: 0
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Senior Member |
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This subject always results in an interesting discussion, but pardon me if I don't attach the entire thread and just respond to a few comments. The good 'ol stock car boys, we were told, gear their cars so it said at "90% torque." Well, they'd never win a race doing that, so I suspect what they really meant is that they try to stay at more than "90% POWER." They were willing to run a touch higher than peak power as long as they didn't go too far below peak power rpm. And the good 'ol boys may have known what to do, but they didn't always use the words us high-brows would approve - hey, they even call engines "motors." I thought the only motor under the hood was the starter.
Someone said something like "at a given speed in a given gear all I want is torque - don't need power." Huh? At a give speed and given gear the rpm is fixed and therefore power and torque are the same. Sure, at a given speed it is nice to have lots of reserve torque because you can accelerate without downshifting. Another example - our engines might produce 250 hp at 3600 rpm and 400 ft-lb of torque at 1800. So the ratio of peak torque to peak hp rpm is 2. I could build an engine that produced 200 ft-lb of torque at 3600 and 250 hp at 7200 and it would likely propel the coach just as well. But to make it equivalent I would have to have a 6.14 final drive ratio instead of 3.07. It would probably be noisy and not too pleasant - but it would work just as well.
There is a problem with having lots of excess torque at cruising speed, and that is it will burn a lot more gas. Okay, maybe not a LOT more, but significantly more. Just to extend what someone said, it might be a better overall compromise to keep the 3.07 final drive and just downshift more. Granted, I've got a very lightweight coach (23', no generator), but I think it would be really fine to have a 350 engine that would put out peak power at maybe 4400. I would get better fuel economy and could pull hills just fine in second gear. Horsepower is hp, and that's what it takes.
Gary Casey
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| Re: [GMCnet] Max torque/max RPM [message #157412 is a reply to message #157277] |
Fri, 20 January 2012 14:29 |
bwevers
Messages: 597
Registered: October 2010
Location: San Jose
Karma: 5
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Senior Member |
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OK, so max torque occurs at 2800 rpm in the stock motor.
And with 3.70 gears that will get you ~65mph.
Has anyone tried to cam the motor for max torque at 2200-2300 RPM?
And did they get better fuel economy?
Thanks,
Bill
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose
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| Re: [GMCnet] Max torque/max RPM [message #157414 is a reply to message #157277] |
Fri, 20 January 2012 14:55 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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I wish... I wish.... there had been a 4 Speed THM425. You would then have good launch and good cruise and always be closer to an ideal gear. That said, mine cruises fine and since I like to run at 65 MPH and not be run over by traffic, the 3.07 "feels" about right to me. What I do miss is a lower first gear around town to get the weight moving. What would not be desireable is the ratios like in a THM700 where there is a big RPM drop from 1-2.
John Lebetski
Woodstock, IL
77 Eleganza II
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| Re: [GMCnet] Max torque/max RPM [message #157417 is a reply to message #157412] |
Fri, 20 January 2012 15:12 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
|
Senior Member |
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My 403 runs 3300 RPM on the tach @ 70 MPH. I run 3:70 Final Drive. I have
cammed Oldsmobile engines, 425 cu in., 400 cu in., and 455 cu in., all
undersquare engine blocks similar to the 455, with an "RV" type of cam and
advanced the timing by 4 degrees over straight up, which will essentially
move the sweet spot of the torque curve towards the lower rpm ranges that
you are talking about. They were purpose built with higher compression than
a stock engine. Around 9.2 to 1. also port matched and with higher rise
intake manifolds, but still running the marine versions of the quadrajet
carb. These engines were used in gill net fishing boats with a berkely jet
pump drive. The fishermen needed lots of low end grunt, and little high
speed running was required. They had the whole ocean to cool with, so the
higher compression was needed to keep a little heat in the engines. They
served the purposes for which they were used very well. I never put one of
them on a dyno to verify exact torque output, but compared to a stock
Crusader/Oldsmobile equipped boat of the same manufacture, the modified
boats would out perform the stock ones every time. I have also built 455
Olds engines for much lighter boats for pleasure craft. The cams, headers
porting, carburetion, manifolding all were purposefully matched so the
engines would perform at a much higher rpm than our GMCs do. Somewhere on
the upside of 5000 rpm. You can make a real handfull of horsepower with
one, if the load is light enough. When you ask a 455 to develop huge
amounts of torque at a low rpm with a fairly large throttle opening, you
are asking a lot of the pistons, rods, rod bearings, 2 bolt mains, oiling
system. They will stand it for quite a while if everything is right. I have
seen many 455s and 403s both run in excess of 150,000 miles before any
internal work is required, except for timing chains. The engines equipped
with HEI type ignition that stay in tune seem to do even better than the
ignition points equipped ones. Just what I have learned for many years of
working on these things.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Jan 20, 2012 at 12:29 PM, Bill Wevers <gmc1975@att.net> wrote:
>
>
> OK, so max torque occurs at 2800 rpm in the stock motor.
> And with 3.70 gears that will get you ~65mph.
>
> Has anyone tried to cam the motor for max torque at 2200-2300 RPM?
>
> And did they get better fuel economy?
> Thanks,
> Bill
>
>
> _______________________________________________
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> Unsubscribe or Change List Options:
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