Tuning transmission for Drag Racing

[boomstick]

"engine torque means absolutely nothing""i'm talking WHEEL TORQUE, not engine torque, two completely different concepts""you need absolutely no torque to produce hp""look at jet engines for example... 0 ft lbs of torque, yet thousands of hp" "torque doesn't do anything what-so-ever""you can have 10,000 ft lbs of torque and yet not move an inch... but if you have even just 1hp, you're moving and doing work"

Im curious, since ft/lbs of torque is an actual measurement of force how can it be absolutely nothing? Isn't engine torque multiplied through your selected gear and final drive to give wheel torque? Wouldnt the max wheel torque for every given gear be at max engine torque? How can you produce hp with no torque if HP is is calculated by ft/lbs per revolution? See, torque is an actual force where as HP is the result of an equation involving.....torque. Oh and jet engines...they produce thrust, unless they are connected to a drive shaft and gear box where they produce...torque. If you have 10,000ft/lbs of torque and it wont turn(produce HP) then you have a problem. See, work(hp) is force x distance. Force(ft/lbs)x distance divided by time is HP. So HP is nothing.

 

[ReVoLuT1oN]

Using less gears can be more. Gt5 defines the max and min value for each gear. And sometimes you cant practically use every gear.

In practice, generally you want to use as many gears as possible.
Which is why it's common practice and general "knowledge" to shorten the gears when drag tuning.

 

[tt54l32v]

That all makes sense on paper, but in actuality you can over gear a car, or anything for that matter. Ever pedaled a 10 speed bike in too low a gear? You sit up there and pedal and pedal yet go no where.
And to say torque is meaningless is a bit over the top, because you cant have hp without torque, but you can have torque without hp.
And on a wheel dyno if you are in a gear lower than 1:1 it will make more torque and less power. Because you have accelerated the drum faster but spun it less.

 

[dr_slump]

has anyone messed with tuning a car for the tunnel using only 5 gears?

i ran into one guy in a zr1 and he said he stretched out the gears to where he only uses 5 gears for the tunnel. tops out around 240, tunnel end to end

i tried it the the final gear ratio had to be in the 2.2xx range

240mph is slow

 

[sprplay]

... once everyone comes to this realization there won't be any of these questions about how to tune transmissions...

This shows the exact accelerative force being applied through the tires. With this we could set gear ratios as well as shift points perfectly.

I'm perfectly in line with your writing about WHEEL torque, but how do you derive practical conclusions from the graphs you showed?

Example: On a 5-gear car where I'm perfectly fine with all gears except 2nd gear, which ratio would you choose for the most rapid acceleration to 240Km/h (ok, the example has quite a peaky torque curve ). From the 2 alternatives plotted in the graph the solid line would indicate higher torque and therefore acceleration in the range between 50 to 65Km/h, while the dotted line would accelerate faster in the range between 65Km/h to 85Km/h. How would you be able to tell which one would deliver the best overall performance?

 

[dr_slump]

Without any calculations, I guess it would be somewhere in between.

 

[sprplay]

@dr_slump: I know The 2 lines were just spread extemly to make their difference more visible.

What I was asking about is your approach, where to put them in order to achive the optimum.

 

[dr_slump]

Sure, but sometimes it's better to set 2nd a bit "too" short.

 

[Swara]

Sure, but sometimes it's better to set 2nd a bit "too" short.

This is true for some cars, like the Civic.

For high-power RWD cars, not so much lol.

 

[sprplay]

So I'd like to ask again:

Is there anybody out there who likes to unveal his knowledge and enlighten me, how to determine an optimal spacing of the gears in between 1st and highest gear, based on my chart?

What I'm looking for is to replace my trial-and-error with a more methodical approach.

 

[Slash]

2nd second gear. More torque I think.

 

[gsrboy171]

2nd second gear. More torque I think.

yep more tq

 

[Master__Shake_]

Everyone here does realize that horsepower isn't real, right? That it's just an equation from the engine's torque output to understand the overall output(workload) of the motor. I'm thinking some people here do and others think horsepower is everything and torque is meaningless.

Hats off to the people who know what they're actually talking about.

 

[dr_slump]

Everyone here does realize that horsepower isn't real, right? That it's just an equation from the engine's torque output to understand the overall output(workload) of the motor. I'm thinking some people here do and others think horsepower is everything and torque is meaningless.

Hats off to the people who know what they're actually talking about.

Power is the combination of movement and forces, nothing is meaningless.
It's wrong to say that power isn't real, cause torque and movement is real, and therefore also power, but power is easier to understand and to work with though.

 

[Master__Shake_]

Power is the combination of movement and forces, nothing is meaningless.
It's wrong to say that power isn't real, cause torque and movement is real, and therefore also power, but power is easier to understand and to work with though.

The engine makes power, yes, but "horsepower" is a term coined to understand the way torque makes this power from the motor. It's not the prime output of the motor.

 

[dr_slump]

The engine makes power, yes, but "horsepower" is a term coined to understand the way torque makes this power from the motor. It's not the prime output of the motor.

What? Horsepower is a measuring unit for power.

1hp = 745.69987158227022W

Better? Should be, cause Watt is the SI unit for power.

W=N*m/s
Force * distance per time
Force * velocity

I can give you an example of why an engine pulls harder at peak power than at peak torque, if you want.