Top speeds capable in 6th?
Thread Starter
Melting Slicks
Joined: Nov 2000
Posts: 2,469
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From: Winchester Ontario
Top speeds capable in 6th?
At what point do you see any higher speed in 6th gear over 5th?
Is there hp or gear requirements to see faster speeds in 6th?
And, how much more of a strain on the engine would using nitrous in a higher rpm (5500 +) in 5th? Would it be as safe as say using it in 2nd and 3rd?
Is there hp or gear requirements to see faster speeds in 6th?
And, how much more of a strain on the engine would using nitrous in a higher rpm (5500 +) in 5th? Would it be as safe as say using it in 2nd and 3rd?
Elite Torch Red Member
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From: Exit 89 GSP,Lakewood,NJ The Land Of Mojo
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Don't forget the aerodynamic factor as well.
I forget the formula, but it takes something like twice the horsepower to go twice the speed or something like that.
I forget the formula, but it takes something like twice the horsepower to go twice the speed or something like that.
Race Director
Joined: Jan 2005
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From: Slidell Louisiana
Originally Posted by Mr Mojo
Don't forget the aerodynamic factor as well.
I forget the formula, but it takes something like twice the horsepower to go twice the speed or something like that.
I forget the formula, but it takes something like twice the horsepower to go twice the speed or something like that.
You would need a really torquey engine to overcome the overdrive gearing in 6th gear at high speed.
Last edited by aboatguy; Dec 12, 2005 at 10:08 PM.
Melting Slicks
Joined: Aug 2004
Posts: 3,003
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From: Indy IN
If you geared the car really short you might be able to see a higher top speed in 6th than a stock car would get in 5th. If you knew the drag of the car and knew the power you could calculate the top speed and then gear the car to achieve it. That would likely be pretty close to where the car is now, but since an LT1 has a good bit more power than an L98 it is likely that you could get 5-10 more mph out of an LT1. If an L98 with 250 hp could do 173 then, in theory a 300hp LT1 could do somewhere near 183 if geared right. That would mean that you would have to put in a 5:1 rear gear to get the right gear ratio that would max you out in 6th. Or, you could put in a 3.3:1 and have the right gearing in 5th..... Obviously it is going to be easier to get the right gear to max out top speed if you do it in 5th....
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Race Director
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Originally Posted by black_89_vette
At what point do you see any higher speed in 6th gear over 5th?
Is there hp or gear requirements to see faster speeds in 6th?
And, how much more of a strain on the engine would using nitrous in a higher rpm (5500 +) in 5th? Would it be as safe as say using it in 2nd and 3rd?
Is there hp or gear requirements to see faster speeds in 6th?
And, how much more of a strain on the engine would using nitrous in a higher rpm (5500 +) in 5th? Would it be as safe as say using it in 2nd and 3rd?
top speed in 5th without a doubt.
Le Mans Master
Joined: Oct 2004
Posts: 6,314
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From: South-central Missouri
Yep!
Originally Posted by aboatguy
I think the power increase needed is the cube of the speed. Which is why the top speeds of the LT1, L98 and the Crossfire powered C4s are so close.
You would need a really torquey engine to overcome the overdrive gearing in 6th gear at high speed.
You would need a really torquey engine to overcome the overdrive gearing in 6th gear at high speed.
It follows a "square law" - essentially power has to increase at (approx) the square of the change in speed to overcome air resistance.
And,
too w/ your torque statement. As power is the product of rpm and torque, to reach the power levels required to meet the power requirement to overcome air (and rolling) resistance increases, the torque value in the torque(ft#) = hp*5250/rpm formula has to be significant to make the power needed. This is why it is so important to optimize rpm thru gearing at desired speeds for either sustained power/speed, or for quarter mile efforts, as I suspect you are well aware of too. 
P.
Burning Brakes
Joined: Sep 2005
Posts: 993
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From: Iowa
If the bottom end of the engine is good enough to hit the nitrous in what essentially is a bog then you will be ok. Just remember that in that gear you will be hammering the bottom end. It’s all in the parts you have!
Drifting
Joined: Nov 2003
Posts: 1,637
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From: Honeoye Ny
I dont see any reason you couldnt use the squeeeze in 5th. Just don't use it for more then 10-15 sec unless you have coated, forged pistons to avoid heat buildup in the crown.
Also the solenoids don't like being on for very long. I think 30 sec is the limit before damage occurs
Also the solenoids don't like being on for very long. I think 30 sec is the limit before damage occurs
Burning Brakes
Joined: Jun 2001
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From: VA
Originally Posted by black_89_vette
At what point do you see any higher speed in 6th gear over 5th?
Melting Slicks
Joined: Jun 2000
Posts: 3,215
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From: Tampa Florida
6th gear was designed as a fuel economy gear...which is great as it works as advertised. The drop from .75 5th gear to .50 6th gear is just too great to make it work. If you gear for 6th with a very low ratio...the other 5 gears don't work so well.
I know some ZR1 folks tried to run 4.56's and the like, but still couldn't get the engine into the powerband in 6th to make it work.
Even the infamous Rick Doria was looking for not so high 6th gear ratios to run in his topend Corvette.
~6300 equals 184 MPH in a stock tired/geared LT4...with another 130 horsepower. A stock LT4 will only do 170-175 depending on condition.
stormin310: You should have been 'JUST' shifting into 5th at that speed...fourth is good to ~140 mph.
Using nitrous for topend runs is not unheard of. Visit some of the Bonneville boards...I know it has been used there. I've tempted to do it...then again...loosing an engine at ~200 mph is sure to hurt...
I know some ZR1 folks tried to run 4.56's and the like, but still couldn't get the engine into the powerband in 6th to make it work.
Even the infamous Rick Doria was looking for not so high 6th gear ratios to run in his topend Corvette.
~6300 equals 184 MPH in a stock tired/geared LT4...with another 130 horsepower. A stock LT4 will only do 170-175 depending on condition.
stormin310: You should have been 'JUST' shifting into 5th at that speed...fourth is good to ~140 mph.
Using nitrous for topend runs is not unheard of. Visit some of the Bonneville boards...I know it has been used there. I've tempted to do it...then again...loosing an engine at ~200 mph is sure to hurt...
Safety Car
Joined: Dec 2004
Posts: 4,088
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From: Poop land
Originally Posted by Baldturbofreak
@30 psi. I dunno If id have a set large enough to go beyond the double century mark. we'll see
You should have no problem pulling through 6th going thru double centuries! Any vids? 
Racer
Joined: Feb 2002
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From: Benoni Gauteng
A friend of mine and I did some high speed runs a while ago for a local magazine. His was a basicly standard ZR1 which topped out in 5th, and when he changed to 6th he just lost speed. On mine (which is 383 S/C'd) I reached 256km/h in 5th (5500 rpm limit at the time) and pulled in 6th up to 304km/h. It is possible to use 6th provided you have the right power, although i wouldn't recommend doing it to often, because i don't think the 6th gear will last too long. Oh yes and my rear is still standard 3.45