Sorry, but that's not true. It's ultimately HP (with the right gearing) that determines the top speed. You see, if you had to gear that 325 HP, 600 ft-lb diesel engine to go 200 mph, the gearing in order to get to 200 would cut the torque to the rear wheels way below what it would need to hit 200 mph.

The formulas used to determine a vehicle's top speed doesn't include a torque parameter, but does include a HP parameter. Torque is part of the definition of HP. Having high torque and low HP like your example is not how it works.

It all boils down to HP and gearing ... period ... (and vehicle aeros, rolling resistance, air conditions and traction).

 

I hear ya ... actually, you could probably go about 2500 mph in a vacuum with 350 hp -- ony rolling resistanc to overcome, no air drag. But of course the tires would explode before you go there !!

 

Iv'e read most of the posts, and they all refer to manual g'boxes.

Is 200mph possible in an A4 box?

is it possible by swapping out the rear end, T.C. perhaps 500hp on the motor?

 

FWIW, Check out LeMans where at this very moment some twin turbo Audi diesels with loads of torque are probably leading the race. In addition they probably have a low rpm redline and do not develop as much HP as other cars in their class, but make considerably higher torque and combined with proper gearing propel them well past 200mph. Conversely, there are many other race cars running other engine configurations racing at over 200mph and are legitamate contenders for the win as well. Point is all this going back & forth is a waist of time since many of you have valid points but just can't give up the fun

 

... it still boils down to HP. I'll bet every one of those cars going over 200 mph make more HP than required to go over 200 mph ... and are obviously geared to match the power characteristics of their motors. As said before, top speed does not depend on torque alone ... it depends on HP. For instance, you could not go 200 mph with an engine that made 5000 ft-lbs of torque at a 200 RPM redline ... no matter how it was geared.

HP = (T x RPM)/5252 = (5000 x 200)/5252 = 190.4 HP

You think a 190 HP engine that produces 5000 ft-lbs of T at 200 RPM could propel a car to 200 mph? ... think about it. The answer is no ... because if it was geared to go 200 mph the torque would be reduced significantly at the drive wheels to the point where it could only go as fast as 190 HP would ever allow it to go, regardless of how much torque the engine puts out. Remember, that it's the HP at the rear wheels (after all the gearing changes the crankshaft's torque to the drive axle torque) that's moving the car. The HP equation also applies at the rear wheels (it applies at every rotating shaft in fact), and that's where it really counts.

This is how it really works.
If "Engine A" makes say 600 HP at half the RPM, but twice the torque as "Engine B" (which also makes 600 HP), then the car with "Engine A" in it could be geared to make the car go just as fast as if it had "Engine B". It's HP that is what really counts - available torque must "tuned" with gearing to match the car and it's application. Gearing matches the engine's power output to make the car accelerate and hit the highest possible top speed based on the engine's available HP.

Bottom line -- it all comes down to HP, and appropriate gearing to match the power output of the engine based on what the car is being used for.

 

I NEVER said that horsepower was not part of the equation, go take your medication

 

You claimed those diesels "probably have a low rpm redline and do not develop as much HP as other cars in their class", but yet can go well over 200 mph.

Well, the reason for that is because they still make more than enough HP to go over 200 mph, regardless of how much torque they make.

Just trying to clarify your cryptic statements so others knew what was going on.

 

I NEVER said that they did not make enough HP to go over 200mph, please take your meds

http://en.wikipedia.org/wiki/Audi_R10

I have NEVER contradicted ANY of your posts Junior, as a matter of fact I have NEVER contradicted ANYBODY's posts. The only point of my post was to make mention that mph goals could be acheived with several variables, but the bottom line is that any vehicle needs HP & TQ to attain and maintain a given speed

 

You never clarified they had to have enough HP either to go 200+ mph, so the way it was written made it look like torque was the key to speed ... I was just clarifying for you "Mr. Touchy". I think you've OD on your meds.

 

zeeosix... hes actually arguing our point but doesnt know it yet.... the audi is very torquey, and on road courses with lots of turns, top speed is not an issue.... and since their engines lean more towards torque than top end hp, they accelerate between curves faster than other cars... but the audis do not have as high of a top speed as the other cars in their class.... and if im not mistaken, the audis have a larger displacement bc they (being deisels) were given a handicap bc no one expected a deisel could perform so well. Reminds me of when the 996 v twin ducatis used to race against the 750 inline high reving engines... but if you compare apples to apples, displacement to displacement and dont give one side a handicap, then the high hp engines will always prevail when manned by a good enough driver. High hp is harder to control than instant torque... hp you have to wait on power bands to kick in.

 

Your insecurities reveal your feelings of inadequacy

 

My Mommy & Daddy own 9 dealerships so I know everything You two get together & play spin the bottle

 

i should have thought about the superbike analogy before, it makes it easire to expalin my point. If you are buying a motorcycle, and ask for torque, they will stick you on a vtwin ducati or rc51. Then you go race a gsxr 1000, with the same displacement, but high reving inline 4, and it smokes you in a straight line, and has a higher top speed. Engines are set up for low end torque, or top end hp... its a spectrum, its a tradeoff, you cant have both if you have a limit on displacement. Typically if you ask someone for torque, the last thing they think you are after is top speed, and will usually take nagative aproaches to top end hp trying to get you more torque.

 

You are absolutely correct

 

... looks like you took about 17 too many horse pills there grandpa.

 

 

Here is a simple equation most engineers use for calculating our top speed and for figuring The Horsepower needed for 200mph

ez = 1 + z + z2/2! + z3/3! + z4/4! + z5/5! + z6/6! + Torque ... ,
cos(z) = 1 - z2/2! + z4/4! - z6/6! + z8/8! - z10/10! + Horsepower ... ,
sin(z) = z - z3/3! + z5/5! - z7/7! + z9/9! - z11/11! + drag... .
All three series are valid for all real numbers. We want to accept the first one as valid for all complex numbers z. Then substitute z = xi, expand, use the facts that i2 = -1, i3 = -i, i4 = 1, and so on, and collect real and imaginary parts. You'll see that the real part of exi is just the series for cos(x), and the imaginary part is just the series for sin(x).

z = cos(x) + sin(x) i
and notice that when x = 0, z = 1. Then differentiate,

dz/dx = -sin(x) + cos(x) i
dz/dx = sin(x) i2 + cos(x) i
dz/dx = [cos(x) + sin(x) i]i
dz/dx = zi
(1/z)dz/dx = i
ln(z) = xi + C
for some constant C, by indefinite integration. Now use the fact that when x = 0, z = 1, to conclude that C = 0. Thus

ln(z) = xi
z = exi
exi = cos(x) + sin(x) i

|z| = sqrt(a2+b2)
z/|z| is then a complex number whose absolute value is 1. Then there is some t such that

cos(t) = a/sqrt(a2+b2)
sin(t) = b/sqrt(a2+b2)
tan(t) = b/a,
t = arctan(b/a)
You can always choose t in the range 0 <= t < 2 to satisfy these conditions. There are two t values in this range with tangent b/a, which differ by . Pick t > if and only if b < 0. Pick t = if and only if b = 0 and a < 0. Then

z = sqrt(a2+b2)[a/sqrt(a2+b2) + bi/sqrt(a2+b2)]
= sqrt(a2+b2)[cos(t) + sin(t) i]
= |z|eti
= eln|z|+ti

 

I'll assume that when you say "i2=-1", that you mean "i squared" and not i2 as a term.

 

i did on mine...

the head up display only showed "00" there was no number 2 on it...

but my vert puts down 512 rwhp....

and this of course was done on a closed street

 

... those equations posted above are all rambling BS. The real equations are actually pretty simple.