cliffyk

I don't know what you mean by "true'engine' characteristics"? [/align][/align]The tiredimensionsare used (along with weight and front/rear distribution) to calculate the rolling resistance, and provide the approximate "Mustang with a 3650 tranny" engine rpm numbers.[/align][/align]Tire slip is calculated from the front toe-in and contact patch width, and drag from the aerodynamic variable inputs. The result is how much forceis required tokeep the car going at the indicated speed, that amount of force is converted to horsepower using the selected velocity (mph). [/align][/align]That's how much raw horsepower it will take to keep the car rolling that speed on flat ground, at sea level, under standard TPH (temperature, pressure, humidity) atmospheric conditions. Where the horsepower comes from; from what engine, atwhat efficiency, at what rpm, or whatever doesn't matter. Where gears and torque curves and the like come in to play is when you want to determine if your engine has what it takes to push the car that fast--in a given gear with a given rear-end. [/align][/align]Using the other tool (gears vs. speed) you can figure out what rpm your engine will be running for the selected gear and gears. If you have dyno'ed your engine then you'll know how much power it outputs at that speed and then by going to the HP vs. speed tool you can see if it's output is enough--and/or vice versa how fast can it go in that gear with the selected rear-end.[/align][/align]For example, let's say that using the gear vs. speed tool we found that in theory car "x" (set up like mine with a 3650 and 3.73 gears) would be turning 5500 rpm at 175 mph in 5th gear.[/align][/align]Next we go to the HP vs. speed chart and find that to push my car 175 mph is going to take 322 HP. [/align][/align]Finally, looking at my dyno chart we see that at 5500 rpm my engine only has 245 horses--so guess what isn't going to happen, even though I've got "the gear" to go 175 at 5500 rpm there's no way I've got the horsepower.[/align][/align]So let's go back down the HP vs. speed chart, and back and forth between it and the dyno chart, and the gears vs. speed chartand see where it all lines up. Turns out that 160 mph takes 248 HP, and that with my setup I'd be turning 5000 rpm or so at 160 in 5th, and that at 5000 rpm I've got about 250 horses on tap...[/align][/align]Real life bears this out, although getting up to 140 is easy and pretty quick, 140 to 148 (per myGPS and that fastest I've had in running) requires that you wait a bit longer, and I suspect that you'd wait abitwith you foot in the firewall to see that 160.[/align][/align]My old '90 Miata dead stock (0 rwHP) topped out at 117 mph and took 1-1/2+ miles to get from 110 to 117. Running 10 psi boost (Eaton M45) and at 175 rwHP I could pop it right up to 128 mph (redline) with plenty left if the engine could have handled it.[/align]

Sxynerd

You inadvertently answered my question. I thought maybe the engine/cam profile would create dead spots where the car just wont accelerate anymore so effectively negating the possible top speed calculation with out friction variables; making the calculators wrong at high speeds. But it appears the calculators don't waiver into being wrong but they are ideal numbers more like the Dyno numbers you referred to in one of your first posts in the thread.

Thanks,
Clear as mud!

cliffyk

All of the factors you mention would indeed affect the real top speed, that's why even to get a close to real approximation you have to shuffle between the gear vs, speed, HP vs. speed, and dyno chart to find the point where it all lines up...[/align][/align]Also, as you can see in the HP vs. speed graph aerodynamic drag is mostly all that matters at any speed...[/align]

dubarado

ok... here's an easy way to do it... DRIVE YOUR ****ING CAR REALLY FAST AND TELL US WHAT NUMBER THE NEEDLE STOPS ON.


and video tape it.

Sxynerd

I'll get right on that

richsw

I like my stock gears. Cruising at 80mph at 2200 rpm.

01snake

Machalicious

Our cars, plain and simple, are not top end cars. They are, however, set up nicely for 1/4 mile fun. InEurope they have something called the autoboun, which allows you to actually take that top end supercar to the max. Here, it's seldom that you will everget to go 150+. All those supercars sell because of what they "CAN" do.Owning a supercar in southern cali, however,you'll rarely get the chance to show it. (Unless u just want to wake up at 2am everymorning to hit the 10 freeway with no traffic). So the steeper gears will help our cars accelerate like high horsepower supercars, but since we can't rev high, and most of us don't have 500hp,we won't keep going like them.

This is slightly hard to believe since beamers and porches usually have better top end than us, but then again i remember your gears are much different than mine and you didn't specify which porche or which beamer.

cliffyk

Another point to consider is that in my 45+ years of driving I have found that there are a lot more people out there that claim to have driven at 120+ mph than actually have--a lot more...[/align][/align]This can be illustrated the next time some yuppie in a Beemer, Porsche, or Lexus wants to race on the highway--bring it up to 115-125 and they'll run out of what my mother always referred to as "testicular fortitude" long before their car does. By the time you hit a buck and a quarter (real mph per a GPS, not what the speedometer tells you) most of them will be only a fading memory in the rear view mirror. [/align][/align]Kid's in ricers are similar but often the car runs out at the same time they do, and even if they've pumped up the motor they probably still have the stock gearing and will redline at 125 to 130. In practical experience most of them go limparound 115-120 (again real mph, their OEM speedometer is probably telling them they're doing 140).[/align][/align]Here in Florida the ones that will run you are the bubba's inthese hot-diesel trucks. Some of these puppies are fast as heck and the driver's are often emboldened by having family ties to the local Sheriff's department (they also probably race super-modifieds on the local dirt track every Saturday night). These truckscan be easily modified and tuned to provide gobs of torque that can readily push 'em to 150 mph+. [/align]

ben790450

My Mustang GT stock topped out at about 145. BARELY. Id didnt pull at all after that and no ones car pulls in 5th gear stock. I dont car what they say it just doesnt happen. When i was full bolt ons (full exhaust, intake, tune, etc) i topped out at about 158. (Using a GPS nav to track my speed) Those were both only in 4th gear. My car now would probably top out at around 140 im guessing due to the gearing . . if it pulled that high up in 5th gear at all. Idk i haven't had it up past around 100.