simple question -- im not really into racing, but I do like running down at the local dragway.

Last time I went out I was shifting at about 4500-5000 RPM. Yielded some lame times, IMO.

Dynoed the engine and highest numbers at the wheels for torque were 316@3200 and 243@5000 for horses.

What is correct technique for manual shifting ? What am I shooting for as far as shift point ? thx.

 

rev that SOB up to 5200 RPM since your peak power is at 5000, that should give you a little leeway when you shift and put you back into your powerband.

 

if u dynoed it then u should know when to shift. right past peak pwer maybe 200 rpm past 250 most

 

Well, what you have to do is make a decission on what you want to do. If you shift after your peak horsepower, you are wasting a little time not making as much power, but you will also land higher in the power band in the next gear.

 

Ok thx. Im was confused becuase peak trq is around 3300 and peak hp is around 5000. Your all saying that its best to shift right after peak hp is attained. Got it.

 

Torque gets your car rollin, hp gets it there faster.

 

after 1st gear trq doesnt really matter as much as ur already accelratin so now ur more dependent on hp to get u moving faster trq will only carry u so far.

 

shift it at 5200

 

EXPERIMENT!!!!!!!!!

Try to make a few runs shifting at 5200 every gear, and see what your times are like. Then, try shifting at a little higher every gear, and a little lower every gear. Make 2 or 3 runs each way, then average your times, and compare. Go with whatever is fastest if you are heads up racing, and whatever is most consistent if you are bracket racing. Every car is different, so just feel it out.

 

to choose your best time to shift it kinda depends on your torque curve, gearing, and such

gears help multiply torque
so lets say at 4000rpms you make 100lbs/ft
with 10:1 total gearing ( taking transmission gearing and rear end gearing) you are putting out 1000lbs/ft of torque at the wheels assuming no drivetrain loss

so you might think ok lets ride out that gear as long as we can to make the most torque
but that isn't always the case being sometimes if you hold the rpms too long you are actually at apoint that the motor has fallen well off it's torque curve and can be making more torque to the wheels at the next gear


if you wanna post your rear end gear ratio, what transmission, and your dyno graph I can try to help you out a little bit if I can find the tranny gear ratio's as well as show how I came up with the results.


or if nothing else you can follow the easy way of shifting after such a point in the peak torque curve...



btw to those that say torque gets you started hp keeps you moving need to learn a little more about the relationship between torque and horsepower. not being to offend you but it isn't that easy to sum it up as.

 

can u sum it up in less than a few sentences

 

Think i got the answer I was looking for (5200) but what the hay, lets hash this out. At the least, I'll learn something I never knew before.

Its a WC-T5 trans
2.95 1.94 1.34 1.00 .63

Rear end gear ratio
3.27

Dyno Graph

 

Based on your graph shift at 5300rpms. At 5200rpms your torque drop meets your horsepower leveling off. Another 100 rpms past that will help you into the next gear right where hp rises steepest and torque is almost peak (probably 3000-3200rpms).

~Matt

 

Just shift where you have the most AVERAGE HP.

 

Using the method Rx7speed talked about you'll want to shift about 5500-6000 RPM.

The basic idea behind this method is that you want the Torque multiplied RWTQ to remain the same between shifts.

 

eh I'm a little late chiming in
been busy since my starter kinda took a dump on me and a few other electrical gremlins :-(



but I'm still here and have all the stuff at work right now though which I will be heading to soon


though ran into one thing I forgot about :-)
but will talk about that later