Daniel60

If a Bullitt can get it done at 151 then I know with my mods that I can at least achieved 140.

GidyupGo

You could have gotten close without the mods. Say.......148 mph bone stock.

Daniel60

No, My car has 4:10s'. However I can't prove it but I feel faster than ever. That car is an accelerating machine. Even if you did have more top end I would still beat you because I would be so long gone you wouldn't have a chance unless we were racing on the moon.

Norm Peterson

Here are a few top speed numbers to ponder, generated by a spreadsheet that solves for the speed at which acceleration = 0 (among other things). I didn't bother to go deeper than 4.56's because the maximum top speed had already been reached in at least one taller gear. I could have picked up the rpm readings but I got a bit lazy.

I used the advertised stock torque, HP, and the rpm's at which they occur. Actual observed speeds may vary slightly, but the trends should remain the same.

The only different assumption between the manual and automatic tranny runs was a 3% greater loss of efficiency through the automatic. At a 1.5% loss the auto tranny top speeds mostly fall right on top of the MT top speeds. At identical losses, the AT speeds are a mph or two higher than the MT speeds for the 3.73's through the 4.30's.

Gear Manual Auto
3.31 146 146
3.55 147 147
3.73 148 148
4.10 149 148
4.30 149148
4.56 148 147

On edit, the very last mph can take over a minute and 2.5 miles of roadway to add . . . . quarter mile estimate for 3.55 MT is 13.8/103 . . .

Have fun.


Norm

Daniel60

https://mustangforums.com/m_1754735/tm.htm

MustangBatman1

I have 4.10s and a few other mods and a removed speed limiter

the car seemsto top out just about where it did with my 3.55s, it still pins the tac, just takes a little longer to get there

breathegood

What RPM did you use, what gear,and what tire size? By my calculations (also an excel spreadsheet), a 5spdGT with 235/50/18 tires and3.55 diffis a 221mph car in 5th gear @6000rpm(in theory). I know this is unlikely to happen, but it looks good on paper. 4th Gear is ~137mph, and 4.10s put it down to ~119mph. This seems consistent with what some have talked about topping out on the dyno.

FYI, this is the formula I used (RPM/tranny ratio/diff ratio)*tire circumference in miles*60 minutes per hour = speed in mph
(6000rpm/1/3.55)*0.001351mi*60minperhour = 137.03mph

Someone correct me if my math is wrong. I know these numbers are ideal, no friction, drivetrain loss, or aerodynamics taken into account.

99flhr

Assuming you`re in 5th gear
4.10`s with the "tac pinned" (6250rpm)would be 180 mph
Not going to happen.

Norm Peterson

It's a simulation that includes aero and rolling drag as well as a torque curve that's fit to the torque and HP data points. And a few other things like rotational inertias (I've been playing around with and refining this thing for a rather long time - decades being a convenient measure at this point).

IOW, I don't assume any rpm. I work with forces instead. Acceleration up through the gears computes the difference between the acceleration traction forces at the rear tires and the total drag at that speed. The difference in forces is what actually accelerates you. When acceleration traction forceis exactly equal to total drag force, you stop accelerating. The spreadsheet is medium-large (400k or so) and looks at acceleration in 1 mph increments (and computes a new torque for each).

Theoretical top speed is meaningless if you don't have enough power to get there.A first-cut estimate for the power required to reach a new top speed is that it's a cubic function of speed, so 220-ish mph is going toneed something like 900 hp if 300 HP is enough to get the job done at 150. A little less, actually, since the rolling drag part does not increase cubically (though it does increase some).

I used the following tranny gear data:

MT 3.38 / 2.00 / 1.32 / 1.00 / 0.68
AT 3.22 / 2.29 / 1.54 / 1.00 / 0.71

The tire size I used was 255/45-18, but as far as top speed is concerned any 27" tall tire would give the same results.


Norm

MustangBatman1

what I meant by that was the pin stops around the 150+ range