Road Horse Power

[aerostealth]

Earlier I posted my HP table and the formatting was all screwed up in the process. The relevant data from my HP posting is for the 80 MPH and 85 MPH data which I will now summarize.

At 80 MPH the truck naked gets 15.1 MPG which translates to 64.2 RHP.

At 80 MPH with aero appliances 18.2 MPG which translates to 53.3 RHP.

This means it took 10.9 less HP to do 80 MPH with the aero appliances added.

At 85 MPH the truck naked gets 13.2 MPG which translates to 78.1 RHP.

At 85 MPH with aero appliances 16.2 MPG which translates to 63.6 RHP.

This means it took 14.5 less HP to do 85 MPH with the aero appliances added.

The truck naked requires 53.5 HP to do 75 MPH v 53.3 HP to do 80 MPH/aero.

The truck naked requires 64.2 HP to do 80 MPH v 63.6 HP to 85 MPH/aero.

This is an 17% and a 18% improvement at speeds respectively with aero.

[Fingie]

Soo technically you could also have a higher top speed? Isn't it that aerodynamics dictate top speed

[aerostealth]

Yes, my truck would have a higher top end speed. Aerodynamics is free HP. Phil Knox and I beleive that my F-150 should have a top end of around 150 MPH. Ford set a record of 148 MPH with a Raptor using 412 HP and my truck can produce 365 HP at 5000 RPM. At these speed regimes my aero should be worth 60 free HP. Such a test would require speed rated tires, and lubricant. It would not hurt to have a spare truck in case you blew yours up. That's where the deeper pockets Ford has is of critical importance. My aero needs improvements such as a belly pan, and boat tail extention but we beleive it could do it. In Texas there is a stretch of turnpike where the posted limit is 85 MPH and we could easily test 90 MPH out. A 100 MPH test would be nice to start forming a good graph curve. We think the engine would be in a very efficient place at 120 MPH but my current tires and limiter would not allow me to reach that speed. P.S. At 85 MPH my RPMs were 2,050.

[ennored]

I assume you are using a BSFC number to go from MPG to HP? You mentioned some numbers in your other thread that makes me think that. What are you using for the MPG (and/or fuel flow)? Just the truck's data via the OBDII port?

Are you using a single number for BSFC? Or do you have a map?

It's a useful way to think about the numbers no matter how you did it. Really shows what the aero is worth.

[jamesqf]

Originally Posted by Fingie

Soo technically you could also have a higher top speed? Isn't it that aerodynamics dictate top speed

If your gearing is tall enough so that you could reach the higher speed without redlining the engine, of course.

[aerostealth]

Yes we are using .452 BSFC per HP hour for the truck. We are assuming gasoline weighs 6.138 lbs per gallon and that our drive line loses are .893. So for the 18.2 MPG at 80 MPH our formula is

80/18.2 = 4.395 x 6.138 = 26.98/.452 = 59.68 x .893 = RHP 53.3

These are useful working assumptions as you say. At 150 MPH the truck would have to get just under 5 MPG to make these numbers work. Phil has data that says these numbers change faster you go. The relationship is not fixed the faster you go. I would have to let him address that.

[aerohead]

Originally Posted by Fingie

Soo technically you could also have a higher top speed? Isn't it that aerodynamics dictate top speed

Here you can see the relationship between drag reduction,and engine rpm (top speed for any given gearing).
*The streamlining allows engine over-speed and shortened engine life,as well as lower BSFC.
*To get the best mpg,the gearing is altered to get the engine back to it's original BSFC island,which maximizes mpg.



*If our estimates are within range at all,Aerostealth's F-150 might do 156-mph at standard atmosphere.

[aerostealth]

Thanks Phil. I worked up a graph on really large paper today showing HP on the vertical axis to 425 HP and speed on the horizontal axis up to 155 mph. It looks kind of empty with the data I have only up to 85 mph and 70 HP.

[aerohead]

Originally Posted by aerostealth

Thanks Phil. I worked up a graph on really large paper today showing HP on the vertical axis to 425 HP and speed on the horizontal axis up to 155 mph. It looks kind of empty with the data I have only up to 85 mph and 70 HP.

I've got dozens of case files for higher performance cars,some of which can easily exceed 200-mph.Over the coming months we'll be able to reverse-engineer data from their published performance which will help us think about the 'Stealth F-150.'
Here's a higher speed table from HOT ROD Magazine illustrating performance for a car of 25-sq-ft frontal area,at differing Cds.
It gives you an idea of what the F-150 is going to be capable of as its Cd continues to fall.

[gone-ot]

Hey, Aerohead, is it possible to get the issue-number/month of that HOT ROD Magazine article where that graph came from?