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I got an Idea

I know what you all should do! First ask Rudy where he got his 145mph speedometer. Then get it and install it...lol! Go and see if you are doing [email protected], then slow down to 70 and see if it is at 2000rpms :D . Now first make sure your equipment is safe (tires, driveshaft, etc). This way you guys could prove your theory.

J/K by the way! My brain hurts from reading this thread. I'm thinking to hard this late at night

Anyways, I got my mom to hit the limiter (106) on the highway...lol. Does that count?:D

EDIT: please note that I did not force her or anything to do it! Thats just the way she drives. She has done it a few times actually! Don't wanna tick anyone off... ok!;)
 

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Re: I got an Idea

Tony said:
Anyways, I got my mom to hit the limiter (106) on the highway...lol. Does that count?:D
NO!!!!!!
 

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I was curious one day

I was on the interstate and was wondering what the 'ol bird would do with the latestest mods. (I believe at that point it was the 75mm TB with the bored to match TB adapter. I had already had the j-chip for a while)

I was on the highway and there was no one in sight so I smashed the gas. To my amazement the car had buried the speedo before it shifted into 4th gear. Knowing that I was doing 120+++ when it shifted into 4th I let off of it and dropped it back into 3rd to slow down quicker because I saw traffic up ahead.

I had my thrill. I dont believe I will do it again because if a cop would have been around I think I would be riding the bus today.
 

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Doubling the rpm at 70 and projecting that you can attain 140 has one basic flaw.

At around 80 mph wind resistance, drag, becomes the greatest force to overcome, vs, rolling resistance and drivetrain friction. The problem is that you must have enough HP in the motor to push the car to 140. There are ways to figure this, but imagine an old VW bug doing 70 mph at 3000 rpm. If you spun the motor in top gear , no slippage , then you would expect to see 140 at 6000 rpm. Problem is that if the motor only makes 80 hp and it takes 120 hp to push it to 140 then you will hit a wall where the motor rpms do not rise and the car does not accelerate any more.

Now TBirds and the sibling cars are aerodynamic enough to acheive these higher speeds at lower drag values, but then you have the acceleration issue. As you approach the wall of HP vs Drag your acceleration increases at a decreasing rate. Basically, if you need 175 hp to push your car to 140 and you make 180 hp you need a REAL long road to get that high and you need to hit 140 at the peak power rpm of the motor. These motors make peak power at around 5300 rpm in mostly stock form.
You need to look at the dyno graph of a motor. Find the HP at the RPM you expect to be at when doing 140, IE 4000 rpm, and you can see you are maybe making 140HP. So, to attain the 140 with your motor at 175hp you need to be at say 5200 rpm. The only way to do that is to be in another gear or have a different rear end. Guess what that does, reduces the top speed. Doing a Bonneville run requires all this stuff to match up when shooting for records.

Now, lets say you have 400 hp to the rear wheels. The top speed has to be figured by finding out the equation of drag to determine the power required to accelerate up the range. Then you plot the HP curve of the motor against that and where they intersect is the top speed of the car theoretically. Hills and air density then start to become small multipliers in that area.
 

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exactly.

im not saying its easy to get to 140, 150, 160, im just arguing about the drivetrain slippage. you can always figure out your speed if you know engine rpm, transmission gear, final gearing and tire size if you know that the TC is locked.
 

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Geez....

Quit arguing about the driveline speeds and such..do the math!

~mph = (rpm x tire diameter) / (gear ratio x 336) ~

~rpm = (mph x gear ratio x 336) / tire daimeter ~

~gear ratio = (rpm x tire diameter) / (mph x 336) ~

~tire diameter = (mph x gear ratio x 336) / rpm ~

(4000x26.1)/((3.27x.70)x336)=135.73mph
(2000x26.1)/((3.27x.70)x336)=67.87mph

67.78mphx2=135.74mph...

end of story..
JL
P.S....I've been to 4300 in OD in my car with 3.27's...a few times:p
 

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DON'T REALLY KNOW

But like A-Train said i know it'll do 104+ some change in 13.0 seconds and has run to the 120 mark on the speedo 1 time, if the calibration on it is correct, and you can lift and cruise at 120 in OD stab the throttle & it'll put ya back some. That's all I know.
Might run 140!!!!
 

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I KNOW I CAN GET BOUT 130 WITH MY 4.10 AND STOCK DRIVE SHAFT................HAHAH.............AND AN FRIEND OF MINE RANDY HAS A 95 TBIRD AND HIT 150.IT FELT SMOOTH.......NO VIBS. WHAT SO EVER.....CAUSE ON A SUNDAY MORNING WE SAW A TRANS AM FLYING ON THE FREEWAY AND HE GUN IT.AND YOU COULD SEE THAT THE TRANS AM WAS NOT GOING ....BUT WE WERE CATCHING UP TO IT.....SLOW BUT SURLY.......THAS WEN HE HAD THE 4.6.NOW HE HAS A CABURATED 5.0...AND IT ITS BOUT THE SAME...........
 

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Yo! MRCYCOUG!!!! Stop SHOUTING at everybody. Just because you either don't know how to type properly or are too lazy to use the shift key does not mean that we care to see it. Have some respect for your fellow readers and type properly.
 

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Re: Geez....

Johnny Langton said:
Quit arguing about the driveline speeds and such..do the math!

~mph = (rpm x tire diameter) / (gear ratio x 336) ~

~rpm = (mph x gear ratio x 336) / tire daimeter ~

~gear ratio = (rpm x tire diameter) / (mph x 336) ~

~tire diameter = (mph x gear ratio x 336) / rpm ~

(4000x26.1)/((3.27x.70)x336)=135.73mph
(2000x26.1)/((3.27x.70)x336)=67.87mph

67.78mphx2=135.74mph...

end of story..
JL
P.S....I've been to 4300 in OD in my car with 3.27's...a few times:p
Good god Johnny! Fry our brains with all that math of yours! Wait a minute, if you fry our brains, we might just get dumb enough to keep trying to get our cars to 140MPH+ in public highways! ;) j/k guys :)
 

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Re: Geez....

Johnny Langton said:
Quit arguing about the driveline speeds and such..do the math!


end of story..
JL
P.S....I've been to 4300 in OD in my car with 3.27's...a few times:p

thats exactly what im saying. the argument that the other side is making is that the aerodynamic drag is causing drivetrain slippage. how they can prove this is beyond me, its just not true.
 

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Re: Re: Geez....

J-Rob said:



thats exactly what im saying. the argument that the other side is making is that the aerodynamic drag is causing drivetrain slippage. how they can prove this is beyond me, its just not true.

dude, I do not say a word about slippage in my reply. The driveline must have total lock. It has to do with the power required to attain a certain speed and the car's ability to create that power. Nothing about slippage.
What JL points out is that to curve your power as I described against the power needed to attain a certain top speed is limited by the hardware. I allude to this in the Bonneville statement.
I did not go into the math, but read it again, I IMPLIED a ton of math.
Math works. Mechanical engineers and physics folks, yes i have that education, have well founded reasoning for their preponderances. (thoughts?)

No , it is not magic or heresay.. it is a hard and fast rule.
Clear your mind first and reread it.
No matter what HP you make if you cannot get past the wall of drag,you will never make top speed above that point.
 

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Re: Re: Re: Geez....

RichardM said:



dude, I do not say a word about slippage in my reply. The driveline must have total lock. It has to do with the power required to attain a certain speed and the car's ability to create that power. Nothing about slippage.
What JL points out is that to curve your power as I described against the power needed to attain a certain top speed is limited by the hardware. I allude to this in the Bonneville statement.
I did not go into the math, but read it again, I IMPLIED a ton of math.
Math works. Mechanical engineers and physics folks, yes i have that education, have well founded reasoning for their preponderances. (thoughts?)

No , it is not magic or heresay.. it is a hard and fast rule.
Clear your mind first and reread it.
No matter what HP you make if you cannot get past the wall of drag,you will never make top speed above that point.
haha. i think you misunderstood what i was saying. the other side is saying that there is slippage. i know that there isnt, im just amazed that they could believe that their is and argue about it so enthusiastically.

i know all about physics and drag and all that beautiful stuff. i argued it all earlier in the thread. ive said pretty much all the things you just said earlier.
 

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i never said anything about slippage and i was on the other side. I just was thinking that with drag and fiction that it wouldn't work out that 2000 = 70mph and 4000 = 140mph

I now believe that it is true. Just never thought of it working that way.
 

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BlackTbird96 said:
i never said anything about slippage and i was on the other side. I just was thinking that with drag and fiction that it wouldn't work out that 2000 = 70mph and 4000 = 140mph

I now believe that it is true. Just never thought of it working that way.
as long as you know you are wrong, thats all that matters :D

j/k... i argued with a friend about this years ago for what seemed like hours, i almost wanted to grab a breaker bar and unleash on him after the first 10 minutes. it was almost as bad as the tire size conversation i had with another friends dad... to this day i still do not understand what arguement he was trying to make. i just knew that it was so incredibly far from true that it hurt my brain to think about it
 

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Lets get deep into this...

MagerThom said:
....suffice it say, drag increases as a function of
the square of its velocity....
and power needed is the cube of the velocity.

D = Cd * A * .5 * r * V^2


and
Horsepower=Drag x Speed
so:
Horsepower= Co-efficient * air density * .5 * frontal area * V^3

which leads to (won't use but good for future ref):
(horse power*2*frontal area/air density)^1/3 = speed

1hp =550lb/ft
Air density at sea level=1.5lb/ft^3
Frontal Area=3816.75in^2=26.5ft^2
Drag Co-efficient=.31 (someone correct me if I'm wrong...)

If you believe that no driveline slippage is caused, Click here for a nice speed by rpm calculator.
 

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Speed vs. RPM

I totally understand and agree that it would require MORE than twice the power to achieve 140 mph than it would to achieve 70 mph, due to the much higher rate of drag. I think some people are mis-interpreting rpm as power, to say that you would need MORE than twice the RPM to double your speed.

RPM is just a rate of speed. Speed is defined as distance over time, such as "miles per hour", or "revolutions per minute". The rate of speed that your wheels rotate will always be directly proportional to the rate of speed that your driveline and engine rotate (and vice-versa) because they are solidly connected through direct gearing (assuming the TC is locked up- anyone with a gen II chip would be locked at higher speed). Your tachometer is essentially just a speedometer for the engine.

Here's an example that everone should be familiar with, and actually applies to the above situation:
If you have a 3.73 rear end gear, your driveshaft will rotate 3.73 times for every 1 rotation of the axle (both wheels in unison). If the axle rotates 2 revolutions, the driveshaft will rotate 7.46 times (3.73 x 2). The same applies to all the other gearing between the wheels and the engine, so by doubling the wheel speed, you will double the engine speed; or by doubling your engine speed (by applying more power), you will double your wheel speed.
 
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