Reading this forum, I've read a few posts which complain about the HP number Ford puts out. 300 is fly wheel HP and rear wheel HP is around 235. *gasp*

One reason I bought my new 06 F-150 5.4 was the HP I needed to tow a travel trailer.

So, I'm guessing Chevy, Dodge, Toyota, etc. report FWHP as well?

How about the 1970 Dodge Charger with a 440 magnum engine that reported 410 HP. Was that fly wheel or rear wheel? My mother had a 67 Chevy with a 283 (V8) that put out 90 HP.

Do I have a truck with 300 HP or 235 HP?

Thanks all for ending my cornfusion.

 

Gawain, all manufactures advertise flywheel hp. They strap the motor to an engine dyno and get the HP rated and that is what they use.

In REAL LIFE, the Engine has to transmit the power to the driving wheels, it goes through the flywheel, to the torque converter, to the transmission to the driveshaft, to the rear diff, then to the wheels. All that traveling "sucks" up HP, thats why its referred to as drivetrain LOSS. you lose approximately 15% in a rear wheel drive car. So technically, your engine produces 300hp, but you are actually only getting 235 to the ground to move it.

 

You do know the difference between the two figures is the losses thru the transmission and rear axle assembly (drive line).
It take power to turn them so you get whats left.

 

Everything stated so far is correct, but you did not mention that the maximum horsepower rating was derived at maximum throttle. In other words lets say you are cruising down the Interstate on a nice flat terrain @ 55 mph with no added weight in the truck. Depending on throttle position, your truck at that particular time may very well be making around 90-100 horsepower. Its all relative to throttle position,air intake, timing, and on and on and on...

 

Things were murky back then.
Here's a good write-up from Wiki:
SAE gross horsepower

Prior to 1972 most American automakers rated their engines in terms of SAE gross horsepower (defined under SAE standards J245 and J1995). Gross hp was measured using a blueprinted test engine running on a stand without accessories, mufflers, or emissions control devices. It therefore reflected a maximum, theoretical value, not the power of an installed engine in a street car. Gross horsepower figures were also subject to considerable adjustment by carmakers: the power ratings of mass-market engines were often exaggerated, while those for the highest-performance muscle car engines were frequently underrated.

 

Chevy never made a 90 hp 283. Dodge never made a 410 hp 440.

The 1970 440 came in two flavors... 375 bhp (4bbl) and 390 bhp (6bbl). Top engine was the 425 bhp / 426 Hemi that was under-rated by about 40 bhp with the factory manifolds.

These were gross ratings without engine accessories.

A 1970 440-375 made around 310 bhp net (The way your truck is rated) and about 250 rwhp with a TF727 Auto.

A current Mustang GT is faster than a 1970 Charger with a 440-375.

So by 1970 standards you have about 365 bhp Gross. You also outweigh that Charger by 3/4 Ton.

 

Forget all those numbers. Your truck WILL tow your trailer. The heavier the trailer, the more you have to adjust your driving style. My truck's engine is rated for ~125hp & I have towed over 10,000 lbs. More than once. Above the speed limit. So don't sweat it.

 

LOL - I know my 5.4L doesn't sweat it w/200k

 

my 4.6 sweats! 182k lol

 

Thanks all. Now I understand why my Japanese Sport Bike was so much fun to ride. It was listed at about 119 HP and usually dyno(ed) at 98 or 99 HP to the rear wheel and only weighed 550 lbs.

Big freaking heavy truck 235 RWHP (pulls travel trailer)
very light motorcycle 99 RWHP (goes scary fast)

bike has 42% of the trucks power and what, 15% of the weight?

I'm not saying which sport bike, 'cause Gene K will tell me what kind of HP it really made... *grinning*.. (jist kidding Gene, I appreciate your information )

ps. I know it's all really about torque.. but I don't even want to go there.... *big grin*

 

By the way Gene. That 70 Dodge Charger RT was mine. Bought it with 3000 miles on it in 1971 from a Dodge dealer in Kansas. Gosh I wish I still had it. It had the torque flight tranny and of course I put big tires on it. From a standing start if I floored it in drive it would smoke the rear wheels before shifting to second where it would again smoke the rear wheels. When it shifted to third it would chirp the rear wheels. That's torque, right? Can the mustang do that?

 

All things considered, the mustand COULD do that if it had the kinda beefy tranny the RT had, and you removed all the dam computer trickery on new cars that tries as hard as possible to keep the tires from roasting.

And just to be the stickler of the group, 300 - 15% = 245. You actually loose more like 25% which would be 225hp (these numbers have been verified through several dyno runs on multiple trucks) They just don't make'em like they used to.

And my 5 speed stang could hit 1-2-3 and if you really, really tried hard, you could chirp 4th, as long as you didn't mind the $300 in repairs thereafter.

 

Yeah, and my RT had to be tuned perfectly to chirp third.

I would have had more dates in high school if I hadn't been under the hood of my charger so much of the time..

It came stock with a plate steel shatter screen under the rear end differential, dual point mallory ignition and a 5 year 50,000 mile warranty. Oh, in 1971, the price of gas wasn't even in the equation. I sold it when the oil shortage hit as I only got 7 miles to the gallon. Should of just put it in the garage.

 

Keeep in mind the torque differences as well.
Bike = no torque.
Two bike motors won't pull a 3 tons up a grade at 60mph.

For comparison, 18-wheeler:
80,000 lb trailer
400 hp
1200 lb-ft of torque

 

I still don't care about gas mileage. Average yearly total miles driven in my Navigator------------7865