FuzzyLog1c

iTrader: (4)

Hey all,

I've been trying to decide on a TR6060 and 9" IRS gear ratio for some time now, and put together a spreadsheet tonight that you might find useful. If you have any suggestions as to how to improve it, give me a yell. Right now, it provides comparisons between:

• The 2.97 CTS-V wide gear ratio with 4.11, 3.73, 3.55, and 3.31 final drive ratios
  
• The 2.66 C6 Z06 wide gear ratio (0.75 5th and 0.50 6th) with 4.11, 3.73, 3.55, and 3.31 final drive ratios
  
• The 2.66 C6 Z06 close gear ratio (0.80 5th and 0.63 6th) with 4.11, 3.73, 3.55, and 3.31 final drive ratios
  
• The 2.29 C6 ZR1 close gear ratio (0.84 5th and 0.67 6th) with 4.11, 3.73, 3.55, and 3.31 final drive ratios

Enjoy!

AAIIIC

iTrader: (19)

What considerations are you trying to balance as you compare the ratios? If you give us an idea of what you're trying to determine then maybe we can provide some ideas on different things to calculate.

As a couple of examples, I have a spreadsheet that I've played with for my Subaru, which has an STI 6-speed in it. Since I auto-x the car, I've got it set up to calculate top speed in 2nd gear. I also have it calculate highway cruise RPMs, since the car is primarily a daily driver and I don't want to kill mileage. (That was more a concern back when it still had a 5-speed in it, as I was trying to balance highway MPG vs having a 5th gear that would actually accelerate on long straights during track days. But anyway...)

If you're looking for good 1/4mi times and have some idea of what sort of trap speeds your combo will be capable of, you could have the spreadsheet calculate RPMs in gear at that trap speed so you can be sure you won't have to shift to 5th.

liqidvenom

iTrader: (2)

Yeah, the purpose of the vehicle is key in deciding this. Drag, road course work, mpg?

punishmentcycle

iTrader: (6)

i have a set of 3.90's if you dont mind can you add that ratio to the mix

FuzzyLog1c

iTrader: (4)

Noted. I want to do a couple of things to the spreadsheet to enhance its usefulness, most notably some drop down menus that allow users to quickly toggle between transmissions and differential gear ratios. In the meantime, just replace one of the differential ratios in any of the tabs with 3.90 and the spreadsheet will automatically recalculate the numbers to the right. The same goes for tire diameter. Change those numbers and everything will adjust.

By the way, is the spreadsheet too wide for you guys? I'm running at 2560x1600 resolution, so I have to be careful not to build something that forces people to scroll left/right a whole bunch.

MN_V

iTrader: (5)

nice work man, thanks. With a built motor and boost, I can see the 3.31 gears kicking some ***.

roninsonic

iTrader: (3)

nice work!

Just so everyone knows, you can do quick calculations like this with the following formula (It's factored out and simplified)


------------(RPM)*(Gear Ratio)*(Convertor efficiency)*(Tire Diameter)*(Pi)
MPH= ----------------------------------------------------------------------
----------------------------- (Final Drive)*1056


Where tire diameter is in inches. For manual cars, use "1" for convertor efficiency

DMM

Have you installed them yet? I keep reading about all the 3.90 ratio gears for the 8.8" are noisey as hell. Interested in these for mine down the road.

meatyCTS-V

:-| ...

ryridesmotox

Lol 294mph with 3.31 in it... That would be awesome. Could you imagine building a huge power FI motor and walking a Bugatti through its top speed? It would take miles and miles but it would be cool.

punishmentcycle

iTrader: (6)

not yet.. ive got a ton of work to do on the car soon, clutch,122,fuel system..then decide on gears.. ive got 3.55's now..3.73 and 3.90 so we'll see