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Old 03-18-2013, 07:04 PM   #11
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Physics is cool!!!
Although it can be difficult to grasp.
I've seen a loaded dump truck almost lift a front tire off the street when it launched. Torque?
I had a Rat engine in a 1972 Blazer that could lift the front end. Torque?
My current truck cannot snap me off the line.
However, it will pull our TT up a hill at 60 mph when it spins at about 6 grand. Horsies?
Torque converters and tranny gearing also play a big part in towing/speed/etc.
A low stall TC will grab the low end grunt when it is there. A high stall TC ignores the low end altogether and makes use of the horsies when an engine gets all wrapped up in itself.

All one needs to do is watch and listen when vehicles accelerate from a stop. Many cars with small/low torque engines get a little bit wrapped up b4 they really go.
Torkie engines move a vehicle off the line without any drama.

It takes a tremendous amount of torkies to haul a load up a hill and that's why we pass so many trucks (semis) - it is not practical to run a truck with the torkies of a locomotive on the road, so they slow down.
They have neither the torks nor the HP to get to the top at speed.

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Old 03-18-2013, 08:15 PM   #12
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There is no arguing the physics here. HP is calculated using RPM and TQ. Do the simple math on the TQ/HP chart shown above. Do that at 2000/3000/4000/5000 RPM's using the TQ values and you will see the HP on the graph is your calculated number. It is that simple. Of course the engine is going to generate more power at 4000 RPM's than 3000 RPM's. if it needs the power it will downshift, if it doesn't it won't.


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Old 03-20-2013, 08:14 PM   #13
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We towed out 5,500 lb RV travel trailer 3,000 miles last year from MN to the Gulf Coast and back with our Ecoboost. We got 11 mpg towing at 60 mph. It rarely needed to shift out of 6th gear; even in the hills. (3.73's) We saw 4th gear twice on an extremely steep and long hill (same hill both ways). It is a 3.5 liter engine with 420 lbs of torque; max torque at 2,500; 90% available at 1,800 rpm.

IMO, it is the equivalent of a small displacement diesel; but with more HP, less maintenance, and cheaper fuel; extremely quiet. Remember it is only 3.5 liters. Double that to 7.0 liters, like many of the big diesels, and you would be looking at 840 lbs of torque.

It really is a unique gasoline engine for towing and it works great. It's biggest limitation is probably the "1/2 ton" chassis. Payload can limit its capability although there is a HD payload option on some configurations.
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Old 03-20-2013, 09:02 PM   #14
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Old 03-20-2013, 09:21 PM   #15
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Originally Posted by jevanb View Post
no it is not... as much as I want to believe, it is not TQ

Just look at the equation and work with it and you tell me which is more important.

TQ is twisting force but NO WORK IS BEING DONE. it gets you moving but that is it...

Once you incorporate the RPM component you are then doing work over a period of time.

You don't go faster from A to B with more twisting force. You go faster from A to B by doing MORE WORK.

Why do you think all ET calculators use HP as the primary variable to determine ET and MPH?

I though your way once but I was schooled and now I know otherwise..
The calculation for work has nothing to do with speed or time. Work=Force X distance

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