Best gear for nitrous

low9sGT hahajk · Mar 31, 2008

I've been thinking about adding a simple 100 shot nitrous setup, for the track. For my application (PI intake-cams, deleted cats, catback, 100 shot) how would 4.10's perform down the track on a 100 shot? I've never driven a 4.10'd car on nitrous, so I really am not sure how it would act. I'd like to pull 12's off this setup, to hold me over for a year when I go forced induction.

Jrgunn5150 · Mar 31, 2008

T45? 4R70w? Wanna spray right off the launch? or have some kind of two step?

low9sGT hahajk · Mar 31, 2008

J.R. said:
T45? 4R70w? Wanna spray right off the launch? or have some kind of two step?

T45. Yeah I'd like to spray first, but I figured I would only be able to do it through 2nd and 3rd?

Jrgunn5150 · Apr 1, 2008

3:73's will probably work better for you, plus, you have to think about whether or not you'll bump the limiter at the top of the track, in addition to the fact the the gas is gonna add like 200 ft/lb of torque, right off the line.

voidfinger · Apr 1, 2008

lol same question with a 4v b head motor with 4r70w and around 125/150 wet shot... what gear ? I'm thinking 4.10's but the limiter makes me wonder

Jrgunn5150 · Apr 1, 2008

Find a calculator and plug in your trans ratios and intended tire height, and go from there. It's safe to bump the limiter to 6500 on either, but that's about it.

voidfinger · Apr 1, 2008

I figure with the IMRC's deleted I would make peak power around the 6500 mark.

Mustangman9812 · Apr 1, 2008

I have 4.10's and spray a 125 shot in 1st gear. But i am a auto.

Bluesn95 · Apr 1, 2008

If you're planning on running slicks you'll most likely destroy your tranny or rearend if they are stock if you spray in 1st gear. I've seen pi swapped motors break those factory axles with slicks. 4.30s on a cobra with spray would be a good match. 4.10s on a 2v.

Pennywise2 · Apr 1, 2008

Since you plan on running nitrous the best gear would be
the gear ratio that puts you are the end of the 1/4 mile
without running out of gear and having to shift into 5th gear.
FRPP 3.73 or Motive 3.90 .

Jrgunn5150 · Apr 1, 2008

voidfinger said:
I figure with the IMRC's deleted I would make peak power around the 6500 mark.

Doesn't matter, if you're running a cast Mark VIII crank and rod's, I wouldn't push it any farther than 6500.

voidfinger · Apr 2, 2008

Well J.R. what would you think would be a good shift point for it? I'm just curious b/c i'm gonna have to program the computer to shift it at that point. Also i just read that the Stock Cobra made peak hp at 6200 rpms. So is that where I should shift?

bottlefed97 · Apr 2, 2008

Spraying 1st gear with 4.10's would be like dropping the clutch at 4,000 rmp in the rain! :nonono:

low9sGT hahajk · Apr 2, 2008

bottlefed, what size shot are you running? Are you running stock heads/cams/intake?

bottlefed97 · Apr 2, 2008

I ran a 125 shot on a bolt on n.p.i. motor with 100xxx miles. I had a delay box to turn it on as soon as I hit second gear, and it still spun quite a bit. I was running Khumo Ecsta Supra street tires. I also had stock 3.27 gears.

Jrgunn5150 · Apr 2, 2008

voidfinger said:
Well J.R. what would you think would be a good shift point for it? I'm just curious b/c i'm gonna have to program the computer to shift it at that point. Also i just read that the Stock Cobra made peak hp at 6200 rpms. So is that where I should shift?

Idealy, you would run it on a dyno, and set it so that it falls back to the beginning of the curve. But 200-300 rpm past peak is a safe baseline that will get you in the ballpark. You will be able to tweak it with your xcal if you get to a test and tune day.

I would run nitrous like bottlefed said, with a delay box, unless you have a built rear, and good suspension. Because if you do hook it, something will break, lol.

voidfinger · Apr 2, 2008

J.R. said:
voidfinger said:

Well J.R. what would you think would be a good shift point for it? I'm just curious b/c i'm gonna have to program the computer to shift it at that point. Also i just read that the Stock Cobra made peak hp at 6200 rpms. So is that where I should shift?

Click to expand...

Idealy, you would run it on a dyno, and set it so that it falls back to the beginning of the curve. But 200-300 rpm past peak is a safe baseline that will get you in the ballpark. You will be able to tweak it with your xcal if you get to a test and tune day.

I would run nitrous like bottlefed said, with a delay box, unless you have a built rear, and good suspension. Because if you do hook it, something will break, lol.

Yea i would do one of those dynotune WOT/TPS switch thing that you can set it to spray in any gear and what not.

Mustangman9812 · Apr 2, 2008

Shoot, You can spray a 1st gear. If you have the correct tires and suspension. I run Mickey Thompson E/T Streets and spray 125 in first gear with no spinning at all. My friend has a H/C/I 175 Shot 5-speed 3.73 geared 87 Mustang we spray 1st gear all the time and he has Mickey Thompson E/T Streets and thats it and he hooks. Heck he pulls 1.5 60' & I pull 1.7's