Any way to remove the speed limitations...

[swamp2]

OK. Here is a much better frontal area estimate. This scaled image gives the correct 77.8" height, but I reduced the entire area shown by a factor of 0.873 since the width was off by a factor of 1.14 (too wide), based on the known front track width. This app has no independent scaling of x and y separately for an imported image...

Thus A = 34.3 ft^2 . I'd guess this is within 5%, more likely a low estimate due to perspective on mirrors and cab and that the diff should probably be included. Due to this and not even really knowing the 1's digit accurately, lets round this to:

A = 35 ft^2 +/- 2 ft^2

This also bumps my top speed calculation (delimited of course) to 129 mph.

Sponsored

 

[swamp2]

I doubt any of us could provide an actual figure for a drag limited top speed on a Bronco without wind tunnel data anyway.

Disagree. Here are some sample calculations I did for an E90 M3 and Porsche 911. The M3 is within 2%.

This is probably a bit lucky as drivetrain losses are an estimate and tire losses a very rough calculation (emperical I'm sure).

 

[mpeugeot]

Coefficient of Drag could probably be estimated from a 1/4 mile trap speed and time, because you already have crank HP (although wheel HP would be a better measurement) and vehicle weight. I would have to have a certain amount of drag to limit the top speed in the 1/4 mile (14.5 @ 95 MPH) with a weight of 4750 lbs.

 

[swamp2]

Coefficient of Drag could probably be estimated from a 1/4 mile trap speed and time, because you already have crank HP (although wheel HP would be a better measurement) and vehicle weight. I would have to have a certain amount of drag to limit the top speed in the 1/4 mile (14.5 @ 95 MPH) with a weight of 4750 lbs.

Not really. It's all a bit circular...

You generally need to have ALL power losses to get accurate performance metrics of any kind. The significant losses are: aero, drivetrain and tires. All grow with speed or rpm. Drivetrain is difficult to isolate via testing, whereas the other two are easier via testing (or CFD) and semi-emperical formulae respectively.

Drivetrain losses dominate at lower speeds say 50 mph or lower whereas aero losses dominate at high speeds, say 75 mph of higher.

My Raptor model gets the 0-60, 1/4 mi time and trap quite accurately so top speed is probably fairly accurate as well. I'll post all of the results later tonight in another new thread.

 

[swamp2]

Made a full performance modeling thread on top speed and other metrics here.

Sponsored