What's the top speed you guys have hit with other gears? 3.54, 3.73, etc?
:auto:

 

You wouldn't believe it if I where to tell you.

 

The fastest I've ever had the '87 with the stock 3.07s was 145mph at Texas World Speedway. You don't have a whole lot of room to get it up past that with a bone stock TPI motor with stock gears, but it wasn't pulling too hard at that point anyway.

 

Well in the future, I'm gonna do engine mods as well. I wanna be a lot quicker in the 1/4 but I don't wanna lose much top end because I don't have much as is right now. I was just curious how much the different gears made a difference.

 

You say you don't have much top end now? How fast do you want to go? Mine only has the 2.59 rear and it will still hit 150+. I have been told with say 3.54 gears it will still hit 150 but will get there a lot quicker. I am soon to find out, I am having 3.54's installed this week.

 

Sweet deal, let me know how it goes. I was thinking about going with 3.54's as well.

So far, I've only been up to 136 but I think the chip is to blame for that because I can feel the pedal pull back on me the exact moment I hit it. If I were to remove it, I think I'd hit 150. I was just wondering if I upgraded if I would be slowed down because I heard that they lower your top end speed the higher the number.

 

I don't know the exact formulas, but I think you'll need to be running around 5K rpms to reach 150 MPH with 3.54s. Just something to think about.

 

Hum, I've not heard of a limiter or anything on a vette, unless it has to do because yours is a convertible? Maybe someone else will chime in about that, mine has the stock chip in it and it doesn't have a limiter, or if it does it is over 153 (My top speed)

 

Thats OK with me, I've only had mine over 150 once, and that was just to see if it would do it. I personally want it quicker rather than faster.

 

OK here is how it works. Engine RPM X Transmission individual gear ratio X Rear end ratio X Tire Revolutions per mile / 60.
This is considering that the car has enough power to turn what ever RPM you pick in the given gear. You can use this for each gear. The only place that the equation won't work is when the converter is not locked. So go for top RPM. You can find your tire's revs per mile on the tire rack's site. :thumbs:

 

Correction. In the equation replace the X with / and the / with X
example 5000 / .73 / 3.07 / 800 / X 60 = MPH

 

I've hit 163+ and it was still pulling with my bone stock lt4 six speed.

 

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.

 

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.

 

The equation that I provided doesn't take wind resistance or lack of Horsepower into consideration. It is only ment to show what the potential of the gear ratio is. BTW: I have a 3.07 ring and pinion for a Dana 36 if interested. :cheers:

 

I too am interested in this, I know alot of people can show you theoretically that you should be able to attain an amazing top speed. But, I remember when the Z06 came out they said it had a slightly lower top speed than the regular C5, do to the higher numerically gear ratio. I remember reading this in a motortrend or something, so I am not certain that it is correct. :confused:


[Modified by JF_AH_64, 5:05 AM 2/11/2003]


[Modified by JF_AH_64, 5:29 AM 2/11/2003]

 

Do you mean higher numerically or "taller" higher? Sometimes a lower numerical ratio "taller" will not work out due to lack of HP to turn it to redline. Or a higher numeric ratio will go faster even though it is a ratio with a theoretically slower top speed, due to the engine's ability to actually turn it to redline. :cheers:

 

Its a proven fact that convertibles aren't as fast as the coupes. I think it has to do with wind resistance and weight.

I know temperature will affect a car but so will humidity and barometric pressure. You should check that as well the next time you test your car out. I'm sure that's playing a factor even though it doesn't seem like it.

 

Those are not gear factors. Those are engine performance factors. :skep:

 

Heres some free software you can get that will figure it for you.
http://www.simtel.net/pub/pd/14614.html