V-10 Killer

iTrader: (22)

Right now I'm trapping barely above 6000 crossing the 1/4 mark. I'm making my best power at 6500 and shifting at 6600 (will be raised to ~6800 after replacing rod bolts...). How much will changing from 3.73's to 3.90's change my trap RPM? Will I be able to finish the 1/4 without going into 4th gear (A4 car)? I tried the stickied posts at the top of the page but they don't really help for a pure 1/4 mile RPM question.

Thanks.

Croaker

I'm calculating roughly 6273, assuming your current trap is exactly 6000. I'm not sure if I'm doing it right though.

JRick212

iTrader: (6)

www.f-body.org/gears/

V-10 Killer

iTrader: (22)

Hey Croaker, thanks
Can anyone else verify that?

I've been aware of that link for years, but it does me no good here.
Thanks anyway though.

The fixed factor here is 1320 feet.
Changing my rear gears basically just changes (shortens) the distance needed to get to my 1-2, 2-3, and 3-4 shift points. After a gear change, that change in distance at the last feet of the run allow me to build more RPM's but I don't know how many, and that site doesn't help tell me.

How about this, where are people crossing the traps with A4 4.11 cars with 3600-4000 RPM stalls?

JRick212

iTrader: (6)

where are you getting this 6273 number? Wouldn't you need to know his tire size as well?

Ric

Welp, if you're taching 6k through the traps, if you run the EXACT SAME TIME AND SPEED with 3.90s, you'll turn 6200ish. Keep in mind that you'll likely be going faster through the traps thanks to the lower gear, so 3.90s might be the way to go if you're gonna be taching 6600 or so.

Ragtop 99

iTrader: (7)

373 to 390 = 5% increase. Trap speed will be increase by 1 mph, which is less than 1% on a car trapping 110 mph. Therefore you cross at 6% higher rpm with 3.90s than you do with 3.73s.

The only X-factor here is your converter. At higher rpm your converter could be more or less efficent (no rule of thumb applies because it is a design issue). To be safe, assume another 1% increase in rpms (i.e. assume efficency gets worse). You can measure the amount of slip at any given rpm in 2nd gear (or 3rd gear if you have a place where you can go that fast) and get an estimate from that.

V-10 Killer

iTrader: (22)

I wouldn't think things that would stay constant between the two setups would be necessary

blind527

iTrader: (8)

If I don't have a rev limiter, what do I put as the Redline RPM on that site, 7,000?

Croaker

It's a constant. I just applied the difference between 3.73 and 3.90 to his estimated 6000RPM current trap.