Top End Speed only limited by Redline would equal ?
 

First off, I know these trucks are built for towing and secondly I know no regular tires are built for a 7000 pound truck doing 170 mph...

That being said, with the predator 100 HP setting and if the top end speedo and tach wasn't artificially limited, what would be the top end speed on the salt flats?

It seems like it would be somewhere in the 160-170 mph range?? Oo. Oo.

Sounds like a fun test to me :)

At yesterdays DFW Dyno Day, we were seeing speeds in the 130 mph range IIRC but not at peak rpm...
just to the limit of the dyno run after a few seconds...

I've removed the speed limiter on the truck, but not in my head :-) so I've only been to about 105 on the empty stretches... (LOTS AND LOTS of rpm and peddle left !)

I've been 3300 RPM in mine which calculated to around 115. My Truck went 125 yeaterday on the dyno speedometer. The way they pull, I think they will go 135 or 140.
The truck is very stable at 115.
You would have to slam it to run 170 but I think it would be possible.

If you have a 7000 pound truck, you must have stripped it down.

It would be RPM * Final Drive * Rear End Ratio * Tire Circumference

With the appropriate conversions for minutes to hour and inches per mile and so on.

From a post from Vic_Ferrari, the final gear ratio of the five speed auto is 0.7:1 and my rear end gear ratio is 3.73:1. My tires are 30.5 inches in diameter give or take a bit.

So if redline is 4200 RPM the top speed would be about 146 MPH. This jives reasonable well with my measured speed at 2000 RPM being about 70 MPH. Actually the indicated speed on my truck is high by about 2 MPH versus what my GPS reads.

The math is 4200/min * (1/0.7) * (1/3.73) * (3.14*30.5 in) * (60 min/hr) * (mi/63360 in)) = 145.958 mi/hr

You can correct for your particular rear end ratio and tire size to come up with the actual numbers for your truck.

Note that I just did a quick measurement from top to bottom of the diameter of the tire. It would be better to chalk off a couple of rotations of the tire to find the rolling circumference versus the calculated circumference above because the tire isn't round as it sits on the ground.

Daryl

And one other factor for our shoe boxes might be wind resistance :)

but we're just trying to get in the ballpark that it's fast enough for most :-X22

Also, many vehicles won't pull redline in top gear due to wind drag and such even if rev limiters were disabled.

My sportbikes are geared to do right at about 190 MPH at redline from the factory, but will only do 172 MPH out of the box give or take a couple MPH depending upon which on I'm riding. This isn't a redline limit its a HP versus wind drag limit.

By changing sprockets on the bike I can adjust the gearing so that I'm using all the motor in top gear at a given track.

Don't know if the 6.0 would push the truck to redline or not in real world conditions with wind drag even in the 150 HP program on my SC. I'll stick to my bikes at that speed :-)

Daryl

I got my old F-250 with a 5.4 triton to 133 with a superchips 1715 in it... It took a long, long time to get there but nevertheless it arrived (this was using an autotap to confirm the speed, so i at least believe it was accurate). That was with a 4.10 rear end in a gas truck with 350 ft-lbs of torque and not quite 300 horsepower. I can assure you, the 6.0 with the superchips WILL NOT be limited by wind resistance below 150 miles an hour, due to the shear torque output of the motor, especially with the superchips. The torque curve with these things is wayyyyy out of proportion in comparison to stock, it carries its seat-gluing power all the way to redline, as i think Vic mentioned in another thread. Another thing to consider, if you were looking for top speed, would be to install an under/overdrive transmission or one of the over/underdrive transfer cases (for the 4x4s)

Wouldnt you just love to get passed by a Superduty doing about 160? You guys over there in the right lane better keep a tight grip on the wheel:-X10

I weighed mine on a scale with me (205 lb fat boy) in the seat it is 6500 lb.

Keep in mind though that your gas motor red lined some where over 5500 RPM if I remember what my '98 150 with the 5.4 l motor did, but the 6.0 won't rev that high.

Also, wind drag varies as the square of the wind speed and the square of the area. The F-250 has a more square cross section, or at least it looks that way.

My sport bike will do 170 MPH but the AMA Super bikes who make something like 190+ RW HP to my bike's 135 RW HP can only do around 200 MPH. It takes a lot more HP to overcome an additional 30 MPH of wind drag at those speeds.

The F 150 had 4.10 gears and shorter tires. We can caculate 145 before redline. The way mine was pulling at 115, I had no doubt that it will make 130 or 140.
As the wind load increases, the boost increases, up to a point.
If we were to go to the Speed Week at the Salt Flats, We would lower the truck to the weeds, get some high speed euro tires, cover the bed and add a wing, Tape every joint and cover the grill.
Then we would go out there with a couple of third members and try different gearing if we needed to.
Add a propane kit and a new agressive custom tune and with 650 HP and 1100 Ft Lb Torque, it would probably run 170 or more.

Can you imagine driving 50 MPH in your Honda Hybred in the right lane, if a PSD went by at 160, The shockwave would blow you off the road!

Oo. Oo. Oo. Oo. Oo.

now THAT would be COOL!!! :-X22

I found I need to get a GPS for the truck to see how fast I'm truly going past 100 MPH since that's the limit of the speedo. The speedo jumps back to zero and just sits there. Or find a friend with a Corvette and blow by him and ask how fast he was going when I blew by him! haha

I agree that with the appropriate mods to lower wind drag, change gearing, change tires, and increase torque that 170 MPH would be possible. And that would be pretty cool. And after all, ASCAR trucks are doing somewhere in that neighborhood, so with enough money and mods it must be possible.

But the original post was top speed if limited only by red line and I think that I provided that answer.

I think another neat question would be top speed if limited only by $1,000 worth of truck mods :-)

Daryl

Of course we would only count the cost of the gas and wire to lower the suspension. So far I've spent $370 on the Predator, $300 on the K&N filter and mass air, $250 on gages. I have exhaust on order from Motorhaven for $400. So I'm past $1000 already.

Bob,

What gauges did you get? How much? Do your own install?

Steve