80% of torque
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Senior User
Joined: Jan 2004
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From: Gray's Creek, NC
80% of torque
Correct me if I'm wrong, but I read the new 5.4 makes 80% of its torque below 1000rpm. The engine peaks at 3750, that would mean that there is a flat spot from 1100-until whenever the torque starts climbing again, but 20% wouldnt make much of a difference. Yes, 80% before 1000rpm is great for moving a heavy load, but how many of us need that "jerk", from what I've seen most guys with pickups never tow anythign close to the max load of their fullsize truck. To me, an ideal torque band woudl constantly climb until the peak. I'm not criticizing, I'd just liek for someone who knows more about it to explain, and in no way am I complainging about having torque as soon as I hit the gas. Thanks for any help.
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and while they are explaining, I would greatly appreciate an explanation of the importance of "torque rise" and what that means exactly. it seems to me that everyone is always harping on wanting a flat torque curve. I don't know.
Something that I have noticed, though, is that engines with torque peaks later in the rpms "feel" like that have a "hotter" motor -- pulls stronger as you climb through the rpms -- although I know that they really are not and do not accel as fast as something that is kicking out the torque down low and all of the way across the range.
just an obs
Something that I have noticed, though, is that engines with torque peaks later in the rpms "feel" like that have a "hotter" motor -- pulls stronger as you climb through the rpms -- although I know that they really are not and do not accel as fast as something that is kicking out the torque down low and all of the way across the range.
just an obs
FTE Leadership Emeritus
Joined: May 2004
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From: Melbourne, Aus
That torque is only available if you require it.
According to one of Newtons laws (can't remember which one, I am sure one of you guys will correct me...
)
Each force must have an equal and opposing force.
that torque figure is under open throttle, and the engine will only provide that torque under full load and open throttle applications.
Also having a flat torque curve is very desirable. Torque in an ideal world would be constant across the entire rev range - i.e. electric motors - and power would then linearly increase.
As power is effectively torque x speed, power will increase as revs get higher.
I shall put in a real life scenario, towing a 5000lb trailer up a 8% grade at 75mph in top gear.
Engine starts to get loaded, driver increases throttle to maintain steady speed. Transmission changes down gear, causing engine rpm to increase - hence providing more power - power to maintain a steady speed.
If torque curve is not flat, as transmission changes down, and rpm increases, vehicle may now be outside the engines "powerband", and vehicle does not have enough power to maintain speed, and needs to slow down to 70mph to maintain constant speed.
I hope that helps a bit...
According to one of Newtons laws (can't remember which one, I am sure one of you guys will correct me...
)Each force must have an equal and opposing force.
that torque figure is under open throttle, and the engine will only provide that torque under full load and open throttle applications.
Also having a flat torque curve is very desirable. Torque in an ideal world would be constant across the entire rev range - i.e. electric motors - and power would then linearly increase.
As power is effectively torque x speed, power will increase as revs get higher.
I shall put in a real life scenario, towing a 5000lb trailer up a 8% grade at 75mph in top gear.
Engine starts to get loaded, driver increases throttle to maintain steady speed. Transmission changes down gear, causing engine rpm to increase - hence providing more power - power to maintain a steady speed.
If torque curve is not flat, as transmission changes down, and rpm increases, vehicle may now be outside the engines "powerband", and vehicle does not have enough power to maintain speed, and needs to slow down to 70mph to maintain constant speed.
I hope that helps a bit...
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Joined: May 2004
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From: Melbourne, Aus
Originally Posted by EKUgrad
Something that I have noticed, though, is that engines with torque peaks later in the rpms "feel" like that have a "hotter" motor -- pulls stronger as you climb through the rpms -- although I know that they really are not and do not accel as fast as something that is kicking out the torque down low and all of the way across the range.
I would have to say that my experience would be reverse to yours in regards to a hotter motor, having a constant shove in the back makes a vehicle feel faster, instead of an sudden hit of power in an rpm zone, when an engine "comes on cam" so to speak.
I have done a lot of work with my 5.4 V8 (check out my dyno graph in my gallery) to flatten the torque curve, and I am able to get more power if I desire, but it will be at the expense of low rpm torque, and the torque curve will be more "peaky"...
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Full torque only comes with a full load. The shape of the torque curve determines the best application for the engine. The transmission "channels" the application of the engine.
- Peak early curve = good for industrial work, towing things around a workd yard
- Broad across curve = good for all applications
- Peak late curve = good for high speed, highway driving
Posting Guru
Joined: May 2003
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From: York, NE
Another advantage of low RPM torqe, besides for pulling, is that it reduces the need for a down shift on a steep grade. I agree with wanting a flat curve. Why would you want less available at the lower RPM's and have to wait for the engine to wind up to get it's torque. I would rather have as close to peak torque as possible on tap at any RPM, ready to be used when I need it.
Also correct me if I'm wrong becuase I'm not sure, but I thought that electric motors made a constant HP, not torque. My reason for thinking this is that the Electric motor in the Escape Hybrid gets 94 HP from 3000-5000 RPM. Which would be 164 ft-lbs @ 3000 and 99 ft lbs @ 5000 RPM.
Also correct me if I'm wrong becuase I'm not sure, but I thought that electric motors made a constant HP, not torque. My reason for thinking this is that the Electric motor in the Escape Hybrid gets 94 HP from 3000-5000 RPM. Which would be 164 ft-lbs @ 3000 and 99 ft lbs @ 5000 RPM.
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Elder User
Joined: Jul 2004
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From: North Carolina
Thats why I love my 352. It peaks at 3500rpm at 400ftlbs, pretty nice. Trtion does not even comptete with my truck. The torqe curve is flat as a pancake.
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From: Iowa
EKUgrad, "torque rise" is something you generally hear about only with tractors. It means that the torque peaks early, although the horsepower keeps climbing. As explained, horsepower is how quickly you can use your torque. Well, in a tractor engine with good "torque rise", as it bogs down to a lower rpm than peak HP in the field, the torque goes up (since peak hp was significantly above peak torque), and you have the capability to power through whatever was bogging you down (albeit at a lower speed).
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