exact "optimal" shift points while drag racing??

blowbyu24 · 01-28-2006, 02:48 AM

can someone either point out where the thread is for optimal shift points while drag racing or tell me please!! thanks

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Chp_Stix · 01-28-2006, 03:09 AM

5500 rpm is good

mandangalo · 01-28-2006, 06:41 PM

Quote:

Originally Posted by 06WRX

5500 rpm is good

5500 rpm is good

drag racing isnt.

seattle944t · 01-28-2006, 06:45 PM

There is no exact optimal shift point - Its going to be based on your motor/tune and gearing. The optimum shift point is the point where you are either getting more torque to the wheels in the next higher gear, or redline the gear you are in - which ever comes first.
To figure out your shift points you need the gearing information on the car, and a dyno plot of your torque. There are a few excel spreadsheets that people have created that already have the gearing info for the WRX and the STi - youll just need to find one and input your torque data.

NattiRex · 01-28-2006, 09:55 PM

Quote:

Originally Posted by seattle944t

There is no exact optimal shift point - Its going to be based on your motor/tune and gearing. The optimum shift point is the point where you are either getting more torque to the wheels in the next higher gear, or redline the gear you are in - which ever comes first.
To figure out your shift points you need the gearing information on the car, and a dyno plot of your torque. There are a few excel spreadsheets that people have created that already have the gearing info for the WRX and the STi - youll just need to find one and input your torque data.

I made one for my PGT and really it can be applied to every or any car the hardest part being that you have to find your engines TQ every 100 rpms and input them... bottom line in most cars these days is redline it honestly....

NattiRex · 01-28-2006, 10:06 PM

The FASTEST way to figure out wether you NEED to use a spread sheet is this though:
Figure out your wheel TQ at red line in 1st, then figure out your wheel HP in 2nd at whatever rpm it would pick up in based on a 1st gear red line shift.... as long as you make more HP in 1st you can feel safe shifting at red line... if your making more power in 2nd you need to start checking lower shift points 100 rpm at a time.

What you looking for is a shift point in which the wheel torque when you leave 1st gear is as close to = and the wheel torque you will get as soon as you hit 2nd gear (or 2-3 or 3-4) the hard part is that every time you calculate a lower RPM shift you have to figure out your rpms in the next gear and 90% of the time the a 100 rpm drop in 1st does not = an easy to use rpm in 2nd... case in point a 7000 rpm shift fomr a Ford Probe GT 1st gear with a ratio of 3.331 to a second gear with a ratio of 1.833 means that second gear will pick up at 3818, while it is easy to just use 3800 rpms what do you do when you get a number like 4247 rpm and there is a 5 Lbft difference between 4200 and 4300 rpms?!?!? so there is some extrapolation... someone link me to a STOCK wrx dyno and I will run the numbers myself and post them....

01-28-2006, 02:48 AM	#1
blowbyu24 Scooby Specialist Member#: 84482 Join Date: Apr 2005 Chapter/Region: Tri-State Location: PA / Element Tuning Vehicle: 2005 STI.UR gt4088r E85 pro comp sti	exact "optimal" shift points while drag racing?? can someone either point out where the thread is for optimal shift points while drag racing or tell me please!! thanks * Registered users of the site do not see these ads.

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01-28-2006, 03:09 AM	#2
Chp_Stix Scooby Specialist Member#: 95195 Join Date: Sep 2005 Chapter/Region: W. Canada Location: Under the hood, in the seat! Vehicle: 1974 Rat Rod Bug back and white	5500 rpm is good

01-28-2006, 06:45 PM	#4
seattle944t Scooby Specialist Member#: 18308 Join Date: May 2002 Chapter/Region: NWIC Location: Seattle, WA Vehicle: 2005 WRX STi Silver	There is no exact optimal shift point - Its going to be based on your motor/tune and gearing. The optimum shift point is the point where you are either getting more torque to the wheels in the next higher gear, or redline the gear you are in - which ever comes first. To figure out your shift points you need the gearing information on the car, and a dyno plot of your torque. There are a few excel spreadsheets that people have created that already have the gearing info for the WRX and the STi - youll just need to find one and input your torque data.

01-28-2006, 10:06 PM	#6
NattiRex Scooby Newbie Member#: 96738 Join Date: Sep 2005 Chapter/Region: Tri-State Location: Nasty Natti Vehicle: 96 Talon Blue	The FASTEST way to figure out wether you NEED to use a spread sheet is this though: Figure out your wheel TQ at red line in 1st, then figure out your wheel HP in 2nd at whatever rpm it would pick up in based on a 1st gear red line shift.... as long as you make more HP in 1st you can feel safe shifting at red line... if your making more power in 2nd you need to start checking lower shift points 100 rpm at a time. What you looking for is a shift point in which the wheel torque when you leave 1st gear is as close to = and the wheel torque you will get as soon as you hit 2nd gear (or 2-3 or 3-4) the hard part is that every time you calculate a lower RPM shift you have to figure out your rpms in the next gear and 90% of the time the a 100 rpm drop in 1st does not = an easy to use rpm in 2nd... case in point a 7000 rpm shift fomr a Ford Probe GT 1st gear with a ratio of 3.331 to a second gear with a ratio of 1.833 means that second gear will pick up at 3818, while it is easy to just use 3800 rpms what do you do when you get a number like 4247 rpm and there is a 5 Lbft difference between 4200 and 4300 rpms?!?!? so there is some extrapolation... someone link me to a STOCK wrx dyno and I will run the numbers myself and post them....