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Old 02-14-2005   #41
GTAracer
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Re: Top Speed

Ra=(p/2)*Cd*Af*V^2

p = air density in slugs/feet cubed. Examples: 0.002378 for 0 altitude and 59 degrees F, 0.002045 for 5000 alt. And 41 degrees F
Cd measured by wind tunnel or field tests
Af = frontal area. Iím estimating 22sf. Will measure my car later to verify.
V = speed in feet per second relative to prevailing wind

Since power is a product of force and velocity:

Power Ra = (p/2)*Cd*Af*V^3 (velocity is cubed)

Since 1 hp = 550 ft-lb per second,

Hp Ra = (p*Cd*Af*V^3)/1100

Just looking at aerodynamic resistance alone:
GTA @ 0.32 ... Af~ 22 Square Feet ... p Use 0.0023
To Maintain 140mph (205.34 feet per second) you need...127 hp
Change Cd to 0.28 you need...111 hp

I'd have to research the math to figure out how much hp it would take to get to 140 mph (acceleration)...the above is only to maintain that speed. I'll do it if asked...
I'd presume that 200 mph is attainable for most cars...even up to about 0.50 drag coefficients. The 300 mph mark probably takes about 4 times more power to get there from 200mph...guessing.

I'll look up the Banks information that I have...may take a few days. I'd rather post published information than just want I might remember.
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Old 02-14-2005   #42
MunsonGTA
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Re: Top Speed

whats all this hp to maintain a certain speed have anything to do with it? we just said the gta is aerodynamic.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 02-15-2005   #43
The Anvil
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Re: Top Speed

Quote:
Originally Posted by MunsonGTA
whats all this hp to maintain a certain speed have anything to do with it? we just said the gta is aerodynamic.
Agreed.
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Old 02-15-2005   #44
GTAracer
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Re: Top Speed

Quote:
Originally Posted by MunsonGTA
whats all this hp to maintain a certain speed have anything to do with it?
That's a good question...
I'll try saying it a different way. I showed Aerodynamic resistance in terms of horsepower so that it can be more easily related or understood.
If you play with the math you will come to find out that the power to overcome aerodynamic resistance increases with the cube of velocity indicating, for example, that 8 times as much power is required to overcome aerodynamic resistance if the vehicle speed is doubled; therefore, it's clear that resistance will increase rapidly at higher speeds. More reason to argue the point that Gale Banks, Don Stringfellow, and Bruce Geisler who worked with Bob Dorn (Pontiacs Chief Engineer) and John Schinella (Pontiacs Chief Designer for the Exterior) in the early to mid 80s did not take a stock car, stuff a high power drivetrain in and go racing, leaving a high percentage of Free Horsepower on the table in terms of decreased Aerodynamic resistance. They are actually a BIG reason the drag coefficient of the STOCK car IS 0.31-0.33. And the cars they used on the salt flats were lower than 0.30 (Sorry, don't have their exact specifications). I do have Karl Steggemeier's and Gary Eaker's car...1988 TA...that they took from stock form, 0.33 Cd as measured in GM's wind tunnel, and brought it down to 0.20, as measured in GM's wind tunnel. And from an untrained eye, their car appears more "stock" than what Banks had. As far as the 91 TA mentioned...I was wrong. It was Steggemeier and Eaker that discovered the 91 would lift. They tried to fix it by adding 500lbs of ballast. His car still flew. So, no need to encourage stock bodied 91, 92 owners to try some high speed tests on the interstate.

I must note that I don't have any info on the 298 mph car someone mentioned. I'd have to do internet searches for that...and I've spent too much time here already. The fastest I have their crew's car going is 277mph...this is as of 1993. Sorry, I don't have info after that. Maybe someone here can provide.

Top Speed is also an energy argument:
Neglecting potential energy (you're not going up or down a hill) the total energy of the car is 1/2*m*v^2 where m is the mass and v is the velocity. So, every time you double the velocity, you quadruple the (kinetic) energy. You need to dump in 4 times as much energy from the engine every time you double the speed. So, since you're car can't quadruple it's energy output every time it doubles it's speed you will accelerate slower. No doubt that wind resistance and other variables are a factor, but even in a vacuum you would not be able to maintain constant acceleration due to the increased energy needs.

Basic physics.

Quote:
Originally Posted by MunsonGTA
we just said the gta is aerodynamic
To be Anal about it a School Bus is also aerodynamic. I'm just clarifying how aerodynamic a GTA is, and can be with basic mods. Instead of arguing wether Banks and others modified their car, we could be discussing simple mods they did that are effective based on wind tunnel data that can be considered "Free" horsepower. I do have first hand knowledge of some truly powerful cars that take advantage of these mods. No use discussing any of that here, though. I'm done.

If anyone wants more info from me then they can PM me.
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Last edited by GTAracer; 02-15-2005 at 10:29 AM.
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Old 02-15-2005   #45
The Anvil
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Re: Top Speed

Dude, you need to get a life.
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Old 02-16-2005   #46
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Re: Top Speed

The fastest I had mine on a country road was 145MPH... no faster,a nd it took a while cause if i tried giving more gas it would kick down.. and I have the aluminum driveshaft.. so that doesn't signify WOT 4th gear.

As for the original post... if you think about the way GTA's were built they are not a top speed car, these cars were built for acceleration. They came with the best truck engine every built.. LOL.. the TPI's have gobs of low end torque which gets you from stop light to stop light in no time...

And I wouldn't call the Trans AM a muscle car from 3rd gen up... for one reason only.. you could not order a trans am with no options like you could in the 60's and 70's. Man i wish i was alive back then... buy a camaro with absolutely no options and a huge big block... TWO LETTERS AND ONE NUMBER ZL1 BABY!! haha... oh yeah
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Old 02-17-2005   #47
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Re: Top Speed

You could order the 350 Formula if you wanted a bare bones street fighter.
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Old 02-17-2005   #48
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Re: Top Speed

Yeah... I was thinking of that as I was posting, but something about the Formula still didn't scream musclecar.. could be just the rims... I dunno.. I think the last muscle car was the 5.0L Stang, you can order that think bare bones with the 5.0 HO.... and it wasn't the best looking either, all boxy and stuff. I think the f-body's went sportscar in 1982
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Best Track Time is 14.396 @ 95.71MPH

225.5hp @ 4250rpm (at the wheels)
325.8ft-lbs @ 3250rpm (at the wheels)
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Old 02-18-2005   #49
GTAracer
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Re: Top Speed

Quote:
Originally Posted by The Anvil
Dude, you need to get a life.
That's funny...since this what I typed above is basically what I do for a living. Just attempting to offer sound advice instead of the daily monkey spank mostly offered.

I know the Formulas were the "street fighters"...but couldn't one buy a 1LE car...which was bare bones with all the performance goodies?
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Old 02-22-2005   #50
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Re: Top Speed

Quote:
Originally Posted by GTAracer
That's funny...since this what I typed above is basically what I do for a living. Just attempting to offer sound advice instead of the daily monkey spank mostly offered.
That's swell, but attempting to impress all with unneccesary and nauseatingly complicated explanations tends to turn people off. I'm sure if someone posted a question concerning ECM's, and an EE happened to be reading it and addressed it with a 10-page dissertation on functions and properties of an electron most everyone would tune out pretty quick.
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Old 08-23-2005   #51
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Re: Top Speed

I found his info to be quite interesting personaly.
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Old 08-23-2005   #52
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Re: Top Speed

lol yea me too. But I'm an engineering major...
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Old 08-23-2005   #53
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Re: Top Speed

i've been to 152 in my 87 gta. it has an L98 from an 87 vette and a 700r4 tranny with 3.27 gears. all bolt on performance parts and typical free mods.
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Old 09-05-2005   #54
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Re: Top Speed

i had an 86 iroc with a tpi 305 with a cat back gutted air box 700r4 and 323 gears my snap on scan tool showed 137mph on flat land my 91 ta convertable would hide the 120 speedo when my buddy had it i havn got it running yet to see what it will do funny thing i have a friend with a 01 stang 4.6 he sys im wasting me time with tpi its old technologyhis 4.6 gt with a cat back cold air induction 5 spd tops out at 133
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Old 09-05-2005   #55
MunsonGTA
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Re: Top Speed

tell your mustang buddy my old technology will crush his rustang anyday of the week
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 09-05-2005   #56
nblanchard
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Re: Top Speed

4.6 Garbage!!! 133MPH?? thats it??!! I've been to 145, and the only reason not anymore, is due to the kickdown problem... some mustang guys can be really ignorant sometimes
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Best Track Time is 14.396 @ 95.71MPH

225.5hp @ 4250rpm (at the wheels)
325.8ft-lbs @ 3250rpm (at the wheels)
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Old 09-05-2005   #57
twobirds
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Re: Top Speed

136 mph, in my 87 350 A4.
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Old 09-05-2005   #58
MunsonGTA
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GTA Year: 1987
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Re: Top Speed

yeah no kidding, I hit 121 and still climbing in 3rd gear...
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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Old 09-06-2005   #59
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Re: Top Speed

Just a little tid bit but John Ligenfelter (God rest his soul) pushed his 355 ci twin turbo'd T/A to an official 298 mph just shy of putting the first production car past 300mph his secret after the twin turbos..???? SIX bottles of nitrious to run through an air to air intercooler not burn it in the engine. He chose the T/A over the Vette for aero dynamics after the vette with an TH700R4 ran in the Silver state classic where he averaged 157 mph and topped out with 206 mph for 5 min !! .... I, With a 'cheetah' upgrade to the GTA with a TH700R4, I hit 135ish mph . (analog gauges)
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Old 09-06-2005   #60
MunsonGTA
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Re: Top Speed

I forgot to mention, that 121 in 3rd gear I pulled out, is with 3.70 gears out back. Give me some different gearing like the vettes and I could probably hit 140-150 in 3rd gear.
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87 GTA: Forged 408 LSX short block, TEA stage 2 cnc ported 243 heads, BTR Stage 3 stroker cam, Fast 102 intake, NW 102 TB, Longtube headers, custom 411 ECM, custom harness, custom tuned, Performabuilt stage 2 4l60E with PTC 2800 stall, 9 bolt rear with 3.70 gears and TAP girdle.

11.16 at 123 mph.
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