which pumpkin is best for the 1/4 mile

[240zprace]

between the R200's= 3.54, 3.70, 3.90... which is better for a turbo Z in the 1/4 mile????

[Thumper]

It really depends on your setup and your power band. Also if you can get the lsd 3.7 then that will prob be your best bet just because of traction and its right in the middle.

[Hugh]

Some like long gears to build load and therefore boost.

 

I run short gears because the car is faster with them. It feels faster in the seat, and its just more fun to drive. Not to mention, faster in the 1/4 mile.

 

I can see both sides of the argument, but I was running a 4.9:1 R230 in my 180sx with GREAT results. I could light off a pair of 245 Nitto Drag Radials all the way up the street and leave two deep black patches.

[Scottie-GNZ]

Ah, the old gear ratio post again.

 

Here is how I approach it. Thumper is correct when he says it depends on your setup and power band. You need to look at overall ratio, not just final drive ratio. Never forget that tire diameter has a big effect on overall ratio. You run a 3.70 with 24.5" tires then jump up to 26" 235/60-15 DR and your effective overall ratio is no longer the same. You need to figure out where in your power band you want to go through the traps at. In the stocker, 5700 is about right. You need to do the math to see what effective final drive will get you through the traps at that RPM at the MPH the car is capable of. In the case of a 240Z with a stock L28ET running a fair amount of boost, that should be about 110+. With a 24.8" tire you would go thru the traps at about 5700, just right. If you throw on a bigger turbo and more mods but leave the internals alone, you will be pushing enough power, when tuned to approach even 124+. Lots more power and torque but you will still be going thru the traps at 5700. Remember, this is not a N/A where you need a cam and have to rev the piss out of the engine to make power. WIth the same gearing and tire, you will now be trapping at close to 6400.

 

Drop the ratio to 3.54 and you will be trapping at a little over 6100 and 3.36 will have you trapping at about 5800. 3.54 and a 26" tire will have you trapping at about 5850, so you see what I mean about the effect of the tire diameter. Is the taller gear not going to hurt the acceleration? NO! This is not a N/A, remember. That extra 100hp you added to trap 124mph probably also added more than 100 lb/ft of torque AND give you higher torque down low than you had before. Now let's say you decide to add a little spray or some real race gas and run the boost most here seem to be afraid of, the car is capable of trapping in the high 120s or more but you still need to trap at 5700. On the other hand if you go with a cam and bigger valves and hogged out ports, custom intake, etc, you will now probably need to trap at 6500+ so the gear ratio will be different.

 

The more time the engine spends in 2nd and 3rd building boost in the meat of the torque curve, the quicker the car will be. Just take a look at what 240Z Turbo just did. He runs a 3.70 and went from a 3-spd JATCO with probably a 3.xx 1st gear to a 2-sp P-Glide with a 1.76 1st gear!!!! and now his car is flying with lots more potential to go quicker. That tall gearing should have slowed him down

[Hugh]

That was a lot to take in.

 

My last car had a 2000rpm power band, and my close-ratio transmission was perfectly geared for it. I would run from 5300 to 7300 in every gear. (power peaked at 7000)

 

It was crazy fast with long gears and short gears in the back. However, I started beating the crap out of some higher powered cars that were comparable to mine but had longer gears.

 

Another nice thing about shorter gears is less stress on the driveline off the launch and when shifting into second gear. My car definitely smoothed out the launch with the gear reduction of about 18%.