Seeker1056

I have done lots of searching but no real answers.
What are you drag guys using for a rear gear to best advantage

Lets say a 28 tall tire and 3400 lbs in a twin turbo car 4l80 3200 stall
for arguements sake 750-800hp

I hear about 3.23 to 3,55s, and some in the 4s
in my experiece too much gear doesnt load the charger and blows the tires away , and too little gear wont get up and go

suggestions please

Seeker1056

wow - 144 visits and not a peep on the subject
maybe i should take a poll on what people are running for a gear?

murphinator

iTrader: (2)

probably not a lot of views from people with twin turbo 800 hp setups.

I also don't have direct experience to properly answer your question but have read enough threads to know a twin turbo setup will be happy if allowed to stay in its torque range and will easily overcome gearing that would be considered less than ideal on a NA setup.

I am thinking when someone with proper knowledge comes in here you will hear suggestions in the 3.08 to 3.42 range and lots of questions/recommendations about how high you spin the engine (max rpm), what you expect it to trap and making sure the gear you pick leaves you some room to grow beyond just allowing it to be at max rpm crossing the traps at your anticipated rpm.

This will be accomplished with some math using your tire size , gear ratio , and expected trap speed to make sure you don't run out of gear before you hit the traps then leaving margin for error.

Do you have any baseline that you are working from on your setup currently ?

Seeker1056

the car is still under construction so I do not have any baselines, and need a starting point - which is why I am here asking the question
i dont wish to run more than 6800 rpm on the top end, and lower is ok
having said that - not assassinating the tires on take off or under 30 mph is parmount
i ran the numbers through a calculator - but that only really works for N/A cars, as you said - turbo cars are a whole different animal.

murphinator

iTrader: (2)

800 hp I would expect the traps to be in the 140's properly geared

AgFormula02

iTrader: (13)

3.7x to 3.5x based on how high you want to spin it.

Blown06

iTrader: (32)

Here is how I do it (when track performance is the goal):

1. Decide what rear tire I'm gonna run (so I can have a diameter for calculations.
2. Decide at what rpm I want to be at through the traps.
3. 99 times out of 100 you will have a high gear ratio of 1:1, so I will use that and my anticipated converter slip (or 0% for lock up or manual trans) and use that information to determine what rear gear to put in the car.
4. Build the transmission with a 1st/2nd gear set that gives me the SLR the car will need for its intended purpose. Rossler offer many many 1/2 gear sets.