shift points/rpm

brian98gt · Mar 22, 2004

what rpm does everyone shift at the track. i'm looking at my dyno results and the horsepower drops off at 5100 rpms, and the torque drops off at4200 rpms. where should i shift. 5100 i''m guessing. any longer and i'ts not beneficial being that the horsepower is falling. am i correct in my thinking?

JonJon · Mar 22, 2004

You want to shift a little after your max RPM so in the next gear you stay in your powerband.

brian98gt · Mar 22, 2004

thanks, i noticed your 6o ft times. nice, how do u launch

JonJon · Mar 22, 2004

brian98gt said:
thanks, i noticed your 6o ft times. nice, how do u launch

I launch at idle, half the time I run 2.2s
Must get drag radials.

kirkyg · Mar 22, 2004

in a 99+GT optimal shift points are as follows (this is mathmatical):

1-2 @ 6300 rpms
2-3 @ 6000 rpms
3-4 @ 5700 rpms
4-5 @ 6000 rpms

You'll never need 4-5 so disregard that. Going into second you dont want to overspin your 2v so shift at 6100-6200 tops but you definitely want to be over 5000. As for torque you should worry about torque to tell you where to shift. You should look at your next gear ratio and find out where your power is (in the current gear) * your gear ratio and match that up with the next gear multipliar * your power level at that rpm you'll be when you shift.

For instance, (without taking into account gear ratio which wont matter for this calculation)

hypothetical
1st gear - 3.37 * 185 hp (@ 6200 rpms) = 623 hp
Your second gear ratio is 2.00 so you take 1.99/3.37 = .6935

then .6935 * 6200 rpms = 4300. Then you would look at your hp graph and find out how much hp you were there and say its 215 hp.

215 hp (@ 4300 rpms)* 1.99 = 428 hp

Technically if the 2valve could handle it you would want to soak a little more out of it. But 6200 is all you'll want to spin it to.

kirkyg

brian98gt · Mar 22, 2004

thank you for the very technical explenation.

Daves4.6GT · Mar 23, 2004

I usally shift at 5800 or 6000 RPM..........

Dave

Brisk281GT · Mar 23, 2004

kirkyg said:
in a 99+GT optimal shift points are as follows (this is mathmatical):

1-2 @ 6300 rpms
2-3 @ 6000 rpms
3-4 @ 5700 rpms
4-5 @ 6000 rpms

You'll never need 4-5 so disregard that. Going into second you dont want to overspin your 2v so shift at 6100-6200 tops but you definitely want to be over 5000. As for torque you should worry about torque to tell you where to shift. You should look at your next gear ratio and find out where your power is (in the current gear) * your gear ratio and match that up with the next gear multipliar * your power level at that rpm you'll be when you shift.

For instance, (without taking into account gear ratio which wont matter for this calculation)

hypothetical
1st gear - 3.37 * 185 hp (@ 6200 rpms) = 623 hp
Your second gear ratio is 2.00 so you take 1.99/3.37 = .6935

then .6935 * 6200 rpms = 4300. Then you would look at your hp graph and find out how much hp you were there and say its 215 hp.

215 hp (@ 4300 rpms)* 1.99 = 428 hp

Technically if the 2valve could handle it you would want to soak a little more out of it. But 6200 is all you'll want to spin it to.

kirkyg

6300 for 1-2??? Isn't the revlimiter at like 6200?

StangLou · Mar 23, 2004

6250 I thought was the rev limit on a stock 2v

Xanax · Mar 23, 2004

StangLou said:
6250 I thought was the rev limit on a stock 2v

Very true I also thought the stock IP heads on the
99+ GT's didn't make any power past 6000 rpm. Why would you
shift that high if your stang is going to fall flat on it's face.

kirkyg · Mar 23, 2004

Brisk281GT said:
6300 for 1-2??? Isn't the revlimiter at like 6200?

If you read the full technical explanation my point was that mathmatically 6300 is the optimal shift point but since you can't overspin the engine you should shift at 6200. The rev limiter is somewhere in that range but i never overspin my engine past 6200. Also, i think the 5 spd and auto rev limiters are different as well as their optimal shift points because of their different gear ratios.

kirkyg

DerekStangGT · Mar 23, 2004

i always thought redline was at 6025

StngStr · Mar 23, 2004

Xanax said:
Why would you
shift that high if your stang is going to fall flat on it's face.

So that when you shift into the next gear you'll be in your "sweet spot". The lower the RPM's are when you shift, the lower they will start in the next gear.

GinoGT · Mar 23, 2004

6050 is where you'll hit the rev limiter.

With a totally stock Mustang, don't bother going over 5500rpms, the powerband falls flat on its face after that. If you have 4.10's you might be able to get away with spinning it a little higher.

If you spin it too high, you might be missing out on some of that torque in the next gear.

As much as some people say it, the modular engines aren't the high-revving engines some people say they are. Sure, the potential for RPM's are there, but the stock crappy intake/heads/cams/exhaust effectively neutralize any chance of 6000+RPMs being a good idea.

P&P heads and intake, big cams, and a nice exhaust would change everything though.

brian98gt · Apr 9, 2004

i have 4.10's and i was at the track tonight and i can't seem to get my shifting right. i've been running consistent 13.8's at 101. when i had the stock gears i ran a best of 13.66 at 102. my best run withthe 4.10's is a 13.66. my 60 ft times are pretty good with consistent 2.05's but after that i must be doing something wrong. i tried shifting at 6,000 13.8 i tried at 5,500, 13.8. i can't win. i think the 4.10's are just too much and i probably should've went with a taller gear. any suggestions. like i said earlier, my dyno #'s show the hp dropping off at 5100 rpms. where should i shift with these gears.

GinoGT · Apr 9, 2004

With 4.10's you have an extra shift to make versus 3.27's.

Drive it like you hate it. Get some DR's and just powershift that bitch. That's racing.

brian98gt · Apr 9, 2004

i do have dr's, but since i got the 4.10's i can't figure out where to shift.

GinoGT · Apr 9, 2004

brian98gt said:
i do have dr's, but since i got the 4.10's i can't figure out where to shift.

Unless you've got major mods that will change the powerband of your engine (cams primarily, but also things like full exhaust or a Bullitt intake) I hear 5500 is the optimal point. Some people say you can get away with going higher in first or second gear because of that mechanical advantage. Personally, nailing a specific RPM in first gear with 4.10's and traction takes PRACTICE because it just flys by so fast.

You really just need to keep practicing and see what works best for you. On that note, I plan on installing a shift light in mine to help me with consistancy.

brian98gt · Apr 10, 2004

i was thinking of a shift light myself, because you are exactly right about the 1-2 shift. it comes up so quick that sometimes it gets over 6,000 rpms. even at 5,500 i'm still running the same times so i am going to experiment today at the track and try shifting at 5100 rpms.

GinoGT · Apr 10, 2004

I'd stick with 5500, maybe 5400. 5100 is too low, probably not hitting peak HP yet.

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