How much power needed to pull in 6th?
Pro
Joined: May 2002
Posts: 678
Likes: 2
From: Lengede
I have 4.10 gears and 6th is more of use to me now. I must confess I haven't driven my Vette faster than 166 mph//4400 rpm. It will run a lot faster I'm sure, but I don't really want to. Acceleration is more important to me than top speed. I think I could go 190 mph in 6th gear if I really wanted to.
Haven't been to the dyno, but I should easily have more than 500 hp.
Arnold
Haven't been to the dyno, but I should easily have more than 500 hp.
Arnold
Melting Slicks
Joined: Jun 2004
Posts: 3,253
Likes: 2
From: Castro Valley CA
Thread Starter
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
Not exactly the feedback that I was hoping for. Anyway, I'd think that some of our over-analytical, theory members would have a decent guesstimate or some kinda software sim.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
I don't really understand the point of your question....
In 6th gear your engine rpm is going to be quite low until you get up to a pretty high speed......look at your tach, then dyno curve and you can tell how much horsepower you have available...
Your torque mulitplication will be 0.5 times 3.92 equals 1.46...so rwtq will be 1.46 times the torque on your dyno curve...
Hope this helps, but still not sure what you are after???
In 6th gear your engine rpm is going to be quite low until you get up to a pretty high speed......look at your tach, then dyno curve and you can tell how much horsepower you have available...
Your torque mulitplication will be 0.5 times 3.92 equals 1.46...so rwtq will be 1.46 times the torque on your dyno curve...
Hope this helps, but still not sure what you are after???
Thread Starter
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
I’m talking about from a top speed perspective. Sorry if that wasn’t clear. I’ve always heard that top speed is achieved in 5th due to our car’s gear ratios, hp, and aero. And that 6th gear will only bog the motor and slow it down. So, my question is…At what point do changes in horsepower and gearing make it feasible to keep accelerating after you run out of gear in 5th?
Pro
Joined: May 2002
Posts: 678
Likes: 2
From: Lengede
I'm with LT4BUD, don't really understand what you want and where you want to drive that fast, considering you live in the USA!!
Maybe this will help you:
With your gears you will be doing:
160 mph/4000 rpm
180 mph/4500 rpm
Now look at your dyno curve and see what you have on HP at 4000 rpm and 4500 rpm. You're no where near your max HP rpm.
At 167 mph/6600 rpm in 5th gear then shifting into 6th gear my engine still pulls hard, and could probably go 190 mph, but don't think you could with your setup. You would have to have an engine with a max HP rpm of about 5000 rpm to go 200 mph.
Maybe this will help you:
With your gears you will be doing:
160 mph/4000 rpm
180 mph/4500 rpm
Now look at your dyno curve and see what you have on HP at 4000 rpm and 4500 rpm. You're no where near your max HP rpm.
At 167 mph/6600 rpm in 5th gear then shifting into 6th gear my engine still pulls hard, and could probably go 190 mph, but don't think you could with your setup. You would have to have an engine with a max HP rpm of about 5000 rpm to go 200 mph.
Safety Car
Joined: Sep 2000
Posts: 3,524
Likes: 4
From: Hinckley Ohio
What happens as you increase speed the horsepower requirements start increasing very rapidly......
if you plotted horsepower required (to overcome windage, frictions, etc) vs speed and also plotted engine horsepower vs speed.....you would find that at lower speeds the motor makes more horsepower than is required to overcome windage,etc., but as speed increases the required horsepower starts increasing faster than the engine horsepower increases and finally the required horsepower is more than the motor is putting out at that speed...the curves cross and that will be the maximum speed...
problem is that in 6th gear this crossover would occur well before the engine reaches its maximum power..
do you see the picture???
if you plotted horsepower required (to overcome windage, frictions, etc) vs speed and also plotted engine horsepower vs speed.....you would find that at lower speeds the motor makes more horsepower than is required to overcome windage,etc., but as speed increases the required horsepower starts increasing faster than the engine horsepower increases and finally the required horsepower is more than the motor is putting out at that speed...the curves cross and that will be the maximum speed...
problem is that in 6th gear this crossover would occur well before the engine reaches its maximum power..
do you see the picture???
Last edited by LT4BUD; Sep 8, 2008 at 06:49 PM.
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Thread Starter
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
I understand what you guys are staying, the question is mostly theoretical, but I figured someone around here that’s big in physics, has a computer sim, or some actually real-world feedback could chime in. I am planning on building a new motor this coming winter/spring, and plan on doing some regional mile races. Anyway, this past weekend with my current setup (obviously) I had a chance to really open it up* and it was pulling like a freight train when I got out of it at/around 6,500rpm in 5th….yes, around 169mph.
*disclaimer – private closed course, and I don’t endorse, recommend, condone excessive speed on public roads
Yes, that's my point of my question....I know it's probably not an easy answer, but there's gotta be a point where power will overcome this "problem" with 6th gear.
*disclaimer – private closed course, and I don’t endorse, recommend, condone excessive speed on public roads
Yes, that's my point of my question....I know it's probably not an easy answer, but there's gotta be a point where power will overcome this "problem" with 6th gear.
Thread Starter
Le Mans Master
Joined: Jul 2000
Posts: 5,012
Likes: 5
From: OKC OK
