How much HP @ highway speed
 

I was just wondering how much hp is required to move a midsized truck "frontier" @ highway speeds (say 65) on flat ground. I know on a car its something ridiculously low like 13 hp, but what about a truck. Any help appreciated.

If you have (or can find... Google is your friend) the vehicle's stats, you can use this tool to calculate the HP figure:

Aerodynamic & rolling resistance, power & MPG calculator - EcoModder.com
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:eek:WOW:eek:. I've been away from ecomodders for a while and must have missed this fantastic tool.... did I say :eek:WOW:eek: Book marking that bad boy. I had to guess on a lot of it IE subbed in the CD for a 90's toyota truck, and I eared on the extreme side of bad, but I think I got a good answer.

Stats I used
vehicle weight. 4215
cd: .44 (toyota 4X4)
Frontal area 2.84 sq.m. (toyota 4X4)
... and I left everything else at stock values. drive train efficiency might have been a little less as it's a 4X4.

But I got a value of 36 hp @ cruising speed. Does that sound about right?

I'd say pretty close. My 03 F250 runs 3x to 45hp at 60mph according to the Scangauge. I can actually "see" the cruise control pulse just by watching the horsepower changes.

36 hp! WOW! (My turn to say WOW :))

Rolling resistance might be higher too. The default values in that form when you first load it up are for my car in stock form. You can save the link to your inputs - grab the permalink above the output table.

Reading load, injector readings, fuel pressure, travel speed, etc directly from the ECU and looking at datalogs, it takes ~25hp to go 65mph steady on a flat road with a drag coefficient of 0.35 in my coupe. 70mph takes ~30hp. Going up a reasonable incline at 60mph takes 60hp. Tires 225/60r16. This is all at a low ~1500-1600rpm's with some very efficient small valve/high velocity heads/intake that make huge torque (400+ ft lbs) from just past idle up to 5500 rpm's at WOT before tapering off.

I would say your 36hp calculations are pretty close to accurate.

I drive a 2001 Blazer with ZR2 package - which means factory 31x10.5" tires, factory lifted & widened suspension, flared fenders front and rear to accommodate, larger rear axle which hangs lower below the body, bigass 31" spare tire mounted to rear of vehicle, etc...

65mph on a level highway with no wind seems to take 50-60hp according to scangauge, 75mph takes 85+ hp, 90mph takes 140hp, 124mph (governor deleted) takes 228hp according to scangauge - which is the highest speed I can sustain. - note that this driving at high speeds is done at Stellar Airpark where I have permission from one of the residents to occasionally borrow a side strip. (for those who point out the stock 4.3L has only 190hp, true - I've some intake and exhaust work done, retuned PCM from wait4me, MSD ignition, and have updated to MPFI from the older CSFI - the 228hp is as indicated on scanguage when travelling 124mph)

It is not a hard and fast and rule! The recommended high speed at every highway is different.