Top speed with different gears?
Pro
Joined: Apr 2002
Posts: 629
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From: Rutland Ma
Re: Top speed with different gears? (Lord Odin)
If my calculations are correct, (5000/.73/2.73/811*60) I should be able to go 185 on my current tires with my current gear. Now if I upgraded to a 3.54's, I could only go 143 mph??? That sucks! :nonod: If I can, I may just stick with my current gears or get some 3.07's.
Thread Starter
Safety Car
Joined: Jul 2001
Posts: 3,615
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From: New Lenox IL
Re: Top speed with different gears? (Chefskeez6)
Well the general rule of thumb is that the higher the gear ratio, the lower the top end speed. If my chip isn't maxing me out at 136, then I could be seeing a lot lower top end speed. I'm just trying to figure out what the potential is of the gears themselves. That way, if I add power to them later, I know what I could possibly expect.
Melting Slicks
Joined: Jun 2000
Posts: 3,215
Likes: 6
From: Tampa Florida
Re: Top speed with different gears? (Lord Odin)
Gearing is quite simple. Try this link:
http://www.f-body.org/gears/
What is your 92's redline? Should be 5500 or more...even my 91 L98 was redlined at 5500. I think they are 5700 so will use that number.
This shows that if your 92 auto could pull redline, it would go 228 mph! Well it can't because the power to push your car that fast is much more than you have so you end up with a top speed that is drag limited (not enough power). I believe an 92 auto will go ~160 mph.
If you install set of 3.54 gears then your topspeed at redline (5700) is going to be 176 mph...again you would not have the power to go that fast stock. Add some different modifications and I could honestly see that you car could run that number-ported heads, cam, etc. Only problem is the deep first gear of your auto may not like the deep rear gear (relatively speaking). I think some folks prefer the 3.07 gear for acceleration-just depends on how you modify the car-top end or not all top end.
Z06 has some deeper gears than the normal Corvette Coupe-this causes it to hit its redline at ~172 or so...if it had some more revs, it could push past this, but it has a revlimiter, like most late model cars, that stop the engine speed at ~6600 or whatever. The standard corvettes have gears that allow a drag limited top speed verses the redline limited.
Hope that helps.
http://www.f-body.org/gears/
What is your 92's redline? Should be 5500 or more...even my 91 L98 was redlined at 5500. I think they are 5700 so will use that number.
This shows that if your 92 auto could pull redline, it would go 228 mph! Well it can't because the power to push your car that fast is much more than you have so you end up with a top speed that is drag limited (not enough power). I believe an 92 auto will go ~160 mph.
If you install set of 3.54 gears then your topspeed at redline (5700) is going to be 176 mph...again you would not have the power to go that fast stock. Add some different modifications and I could honestly see that you car could run that number-ported heads, cam, etc. Only problem is the deep first gear of your auto may not like the deep rear gear (relatively speaking). I think some folks prefer the 3.07 gear for acceleration-just depends on how you modify the car-top end or not all top end.
Z06 has some deeper gears than the normal Corvette Coupe-this causes it to hit its redline at ~172 or so...if it had some more revs, it could push past this, but it has a revlimiter, like most late model cars, that stop the engine speed at ~6600 or whatever. The standard corvettes have gears that allow a drag limited top speed verses the redline limited.
Hope that helps.
Racer
Joined: Aug 2000
Posts: 339
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From: cambridge UK Cambs
Re: Top speed with different gears? (dizwiz24)
.
One thing to remember, a gearbox is at its most efficient with 1:1 ratio i.e. input and output locked. the greater the overdrive ratio the more the power loss.
I do not have any numbers to know if the difference is significant but it is certainly there.
:hat
I think this issue is more complex than any of you bargained for. Wind resistance between the coupe and the vert, engine powerband with your current mods, and your gears in the back will all have an effect.
A lot of people will say, you wont lose any top end with 4.11 gears because now 6th is usable. Ok. We all know Corvettes attain there highest top speed in 5th with stock diff gears, but will the slightly taller (compared to stock gears in 5th) gearing on 6th (with 4.11's) still allow you to fight the wind resistance to now attain the same top speed you did in 6th.
I didnt say that last paragraph well. But consider this....I have heard people say that, although you attain top speed in 6th gear, it wasnt as high as the top speed they used to get with the stock differential gears in 5th.
I have had my vert up to 148 top up, and 138 top down. I was approaching other traffic and didnt feel like blowing by them in the passing lane at twice their speed. Its interesting how at different RPM's it accelerates differently. For example, in 5th, in between 130 and 140 MPH it acceleration slows down, but hit 140 (in 5th still) and it starts accelerating quicker, despite the extra wind resistance ! (i think due to the engine being in its powerband).
Too further complicate things, sometimes i can go out on the same road at what seems like the same temperature, etc. and hit 140 real quick. Other times, it takes a long time. i still havent figured this one out....Its like that with all my cars.
Someone correct me if I am wrong, but it seems like the convertibles may not have as high a top speed as the coupe. I mean I am only talking a 6 MPH difference, but still not as high. Throw a hardtop on there, and I bet it might help out.
A lot of people here will say ' top speed is useless' . I totally disagree, that one time you are on a long trip, and theres no traffic, and the road is straight, you will wish you had all the top end in the world.
As a final note, the Corvette is not my favorite car to top end. Its the most terrifying car at high speeds. Compared to my 1995 Nissan Maxima SE 5spd which hits its max of 140 MPH no problem, the Corvette gives a much rougher ride. You feel every bump in the Corvette, and it seems like it wants to go airborne over the slight rise and fall of highway bridges at those kinds of speeds.
A lot of people will say, you wont lose any top end with 4.11 gears because now 6th is usable. Ok. We all know Corvettes attain there highest top speed in 5th with stock diff gears, but will the slightly taller (compared to stock gears in 5th) gearing on 6th (with 4.11's) still allow you to fight the wind resistance to now attain the same top speed you did in 6th.
I didnt say that last paragraph well. But consider this....I have heard people say that, although you attain top speed in 6th gear, it wasnt as high as the top speed they used to get with the stock differential gears in 5th.
I have had my vert up to 148 top up, and 138 top down. I was approaching other traffic and didnt feel like blowing by them in the passing lane at twice their speed. Its interesting how at different RPM's it accelerates differently. For example, in 5th, in between 130 and 140 MPH it acceleration slows down, but hit 140 (in 5th still) and it starts accelerating quicker, despite the extra wind resistance ! (i think due to the engine being in its powerband).
Too further complicate things, sometimes i can go out on the same road at what seems like the same temperature, etc. and hit 140 real quick. Other times, it takes a long time. i still havent figured this one out....Its like that with all my cars.
Someone correct me if I am wrong, but it seems like the convertibles may not have as high a top speed as the coupe. I mean I am only talking a 6 MPH difference, but still not as high. Throw a hardtop on there, and I bet it might help out.
A lot of people here will say ' top speed is useless' . I totally disagree, that one time you are on a long trip, and theres no traffic, and the road is straight, you will wish you had all the top end in the world.
As a final note, the Corvette is not my favorite car to top end. Its the most terrifying car at high speeds. Compared to my 1995 Nissan Maxima SE 5spd which hits its max of 140 MPH no problem, the Corvette gives a much rougher ride. You feel every bump in the Corvette, and it seems like it wants to go airborne over the slight rise and fall of highway bridges at those kinds of speeds.
I do not have any numbers to know if the difference is significant but it is certainly there.
:hat
Race Director
Joined: Sep 2001
Posts: 14,682
Likes: 753
From: NEwhere Ohio
Re: Top speed with different gears? (Lord Odin)
You know I thought of something else, Lord Odin. Before I replaced my optispark on my 93 (only had 28,000 miles) I would accelerate and sometimes hit say 105 MPH, and BAM! I hit a wall, like a governor.
Really it was my optispark shorting out under load at high RPM. After changing plug wires, and some other stuff to try to fix it I removed it and discovered a rusted rotor, broke seals, and an almost shot bearing/bushing.
Oh, and you mentioned that convertibles are slower. They are a little on top end, but shouldnt be in the 1/4. There is no more than 100 pounds weight difference between the two.
Really it was my optispark shorting out under load at high RPM. After changing plug wires, and some other stuff to try to fix it I removed it and discovered a rusted rotor, broke seals, and an almost shot bearing/bushing.
Oh, and you mentioned that convertibles are slower. They are a little on top end, but shouldnt be in the 1/4. There is no more than 100 pounds weight difference between the two.
