Pumba

Pardon me if this has already been posted.

Motor Trend magazine recently completed Hot Laps of Laguna Seca Raceway with 9 high-end sports cars. The results are a little surprising and very satisfying for Corvette owners.

The following are the fastest lap times for each vehicle:

~ Lotus Evola S ------------ 345 HP - 1 minute 42.49 seconds

~ Ford Boss Mustang 302 - 444 HP - 1 minute 41.06 seconds

~ Mercedes SLS AMG ------ 563 HP - 1minute 38.82 seconds

~ Porsche 911 GT3 RS ----- 450 HP - 1 minute 36.77 seconds

~ Audi R8 GT --------------- 560 HP - 1 minute 36.39 seconds

~ Lexus LFA ----------------- 552 HP - 1 minute 36.39 seconds

~ Nissan GT-R -------------- 530 HP - 1 minute 36.35 seconds

~ Ferrari Italia 458 --------- 557 HP - 1 minute 36.22 seconds

~ Corvette Z06, with Z07 -- 505 HP - 1 minute 34.43 seconds




Just imagine what a Z06 could do with 5th gear changed to 0.79:1, 6th gear changed to 0.628:1 and a 3.90:1 final drive ratio

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froggy47

I too would love to see lower gears all around, in the quest for 0-60 times & top end I think the GM engineers are leaving a lot of time on the table so far as lap records. At least US tracks. They do seem to favor Nring testing.

Pumba

Bob,

I agree !

When I watched the GM videos of their recent runs on the Ring with the ZR1 and the Z06 I convinced myself that the GM Test Driver lifted the throttle of the Z06 on the final long straight. The Z06 just stopped accelerating about half way down the straight, while the ZR1 kept accelerating.

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Rednels

I think the high gearing is more for EPA regulations than performance. I know my viper will hit 60 in first gear, I thought that was for 0-60 times. But when I got a chance to speak with engineers from Dodge, they said it was to make better fuel economy.

I think that the vette and the viper both could benefit from a little bit shorter gears.

Bill Dearborn

First gear is rarely used on the track. Most tracks 3rd and 4th gears are all you need and they seem perfectly suited for the task. I seriously doubt 3:90s would help all that much since the driver would end up using 4th and 5th instead of 3rd and 4th. You can only apply so much torque through the tires and once you are at that limit adding more torque through more power or through gear multiplication doesn't really help.

Bill

z06801

Great videos! I just watched those hot laps today and was stoked when I couldn't find one faster than the new Z06 I agree with Bill my c5 z stays in 4th gear even on Millers almost 1 mile long straight. With my new build a 433 ls2 with dry sump, I had RPM use the standard cars taller 1,2,3,4,but a shorter 5th and 6th so even with my new found torque I won't use 5th

Rednels

I agree with you on lower gears. However, in 5th and 6th, there is a definite gain to be made with shorter gears. I speaking from a tranny stand point, not the rear end gears.

When I shift from 4th to 5th it feels like I opened a parachute. At tracks like VIR and Road Atlanta those straights are super long and it would be nice to have a little more acceleration in 5th. I have never even come close to redline in 5th......

Bill Dearborn

with your argument about the long tracks and the use of 5th gear. The gap from 4th to 5th is pretty large which drops the rpms quite low when you shift. At the Glen I have never been able to get 5th up to the same speed on the back straight as I get in 4th even though close to the rev limiter in 4th at the end of the straight.

Bill

BFoster

i had standard gears in my 02z but a 4.10 rear end. i seemed to always be in the powerband at road america, and used up all of 5th gear on the long straights. same can be said about mid america motorplex, i felt the gears were a helpful mod. that being said, motors wont last long with those higher rpms i was seeing.

heavychevy

That's pretty close to the ACR (1:33.9) and with no big aero and significantly less hp.

Pumba

Bill,

I felt the same way, until I tried a numerically larger final drive ratio. As an example, a 4.10 FDR give your Corvette 20% more rear wheel torque in evey gear than the standard 3.42 FDR does. I could feel the difference in every gear and coming out of every corner. I miss my 4.10, and when and if Motive Gear makes a 3.90 FDR available for the C6 ZR1 differential I will have RPM Transmission install it.

Also, I recently had a MN6 gear set with a 0.79 5th gear and a .628 6th gear installed in my C6 ZR1 trans. There is no longer a hole when shifting from 4th to 5th or from 5th to 6th.

JR

Timz06

What tracks are you driving that you need 5th in a C6Z06 with stock power levels? The car will do 163 in 4th gear.

I drove a C5 with 4:11 gears at VIR and it was horrible. Shifting gears all of the time. The guy finally ended up changing back to a 3:42.

Tim

mcar00

I thought a stock C6 ZR1 had about a .82 fifth gear ratio and a .68 sixth gear ratio?

AU N EGL

We had one at the NCM event this summer













Very light wt wheels to reduce rotational weight

AU N EGL

4.10s had too much shifting and temps were too high

3.73 with a close ratio 5th of .85

or the standard 3.42s with a 5th at .85

Pumba

Mike,

You are correct. I don't have the stock ZR1 gear ratios even though I have a ZR1 transmission. After having driven the ZR1 ratios with a 2.423:1 first gear for almost a year, I had Paul at Liberty Performance here in Allen Park, Michigan install the following gear ratios late in August. With my existing 3.42:1 final drive ratio and 26.4-inch diameter tires, I achieve the following speeds in each gear:

1st - 2.66 - Vehicle speed at 6,500 rpm = 56 mph

2nd - 1.78 - Vehicle speed at 6,500 rpm = 84 mph

3rd - 1.30 - Vehicle speed at 6,500 rpm = 115 mph

4th - 1.00 - Vehicle speed at 6,500 rpm = 149 mph

5th - 0.79 - Vehicle speed at 6,500 rpm = 189mph

6th - 0.628 - Vehicle speed at 6,500 rpm = 238 mph


When and if Motive Gear makes a 3.90 ring and pinion set available for the C6 ZR1 differential I will have it installed by RPM Transmission. That will change the speed in each gear to the following:

1st - 2.66 - Vehicle speed at 6,500 rpm = 49 mph

2nd - 1.78 - Vehicle speed at 6,500 rpm = 74 mph

3rd - 1.30 - Vehicle speed at 6,500 rpm = 101 mph

4th - 1.00 - Vehicle speed at 6,500 rpm = 131 mph

5th - 0.79 - Vehicle speed at 6,500 rpm = 166 mph

6th - 0.628 - Vehicle speed at 6,500 rpm = 208 mph

The 3.90 ring and pinion will allow me to reach 200 mph at or around my horsepower peak in 6th gear.


For those who are interested, I have put together an EXCEL spread sheet that takes your inputs for trans ratios, differential final drive ratio, tire size, shift speed, peak torque in lb.-ft., peak torque rpm, and calculates the peak torque at your rear wheels, vehicle speed at your shift speed in each gear, and tells you if your trans ratios lets your rpms drop below your peak torque after a shift. PM me if you would like a copy.

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mcar00

Wow, thanks for such a detailed reply! I have my trans. out of my car right now and so I've been thinking about gear ratio's. It sounds like you've decided that you like the 1st-3rd Z06 ratios better than the ZR1 ratios which is interesting. I like the idea of a close ratio box like the ZR1 but I did think that with as much as we use 3rd gear on a road course that the 1.30 third gear ratio might work better. No doubt fifth and sixth work better in the ZR1 which you basically kept.

Let us know how you like the car when you change to a 3.90 rear gear ratio. I have seen guys put numerically higher rear gears in for road course use only to go back to the original ratio due to the increased number of shifts and the difficulty of modulating the throttle coming off turns.

AU N EGL

Rockland Standard can put together what you want. Stronger too.

Rednels

At Road Atlanta its close to 170 on the back straight, and VIR more like 177....

Even though I hate the drop off in 5th, I would never touch the rear end gears. I think the fix would be for a very slightly shorter 4th, and a bit shorter 5th in the transmission.

Gering

PUMBA: Very Nice Looking Vet!!!