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Old 07-26-2006, 09:22 AM   #1
Bense
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Default How to fine tune your gearing for optimal 1/4 mile acceleration.

What we're doing here -- We're using math to estimate the trap speed of a vehicle at the end of a quarter mile based off of the horsepower and weigh of the vehicle.

As many of you know, in accordance to Newton's 2nd Law of motion, Force is a product of both mass and acceleration. So, simple algebra here, acceleration is the quotient of force/mass

Using some physics and modeling, interpolation, differential equations....you know what, who cares. cause someone else has already done the grunt work and made a sweet webpage that does all the thinking for us:

http://www.stealth316.com/2-calc-hp-et-mph.htm
Such a great site.

What you wanna do here is input your estimated power, the weight of your vehicle plus the driver and get an estimation of trap speed.

Then we want to play with a gear calculator and input or vehicles specs, redline, tire size, etc.
http://www.fatboyraceworks.com/gears/

Then pick a trans configuration where 4th gear is slightly higher than your estimated trap speed.

Last edited by Bense; 11-30-2009 at 11:08 AM.
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Old 07-26-2006, 05:31 PM   #2
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Default Re: How to fine tune your gearing for optimal 1/4 mile acceleration. (Bense)

Great work as always Bense Click the image to open in full size. I debating with myself right now wether to buy a 4.9 or 1.565 thrid hmmmm decision descions. BTW: I am assuming that 1.2 4th is a typo? Also does the infintude 1.25 require grinding to move to the 4th spot?
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Old 07-26-2006, 10:44 PM   #3
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I use Gran Turismo.........

I'm not joking either.
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Old 07-27-2006, 01:50 PM   #4
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Default Re: (Mista Bone)

I feel outgunned in this thread Click the image to open in full size.
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Old 10-18-2006, 04:35 PM   #5
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Default Re: (cbmprelude)

bump for an update
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Old 10-18-2006, 06:34 PM   #6
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the calc. are pretty close
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Old 12-31-2006, 12:41 PM   #7
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Default Re: (mugenej8power)

I have a 96 Civic EX Tranny. the FD is 4.250:1 would I benefit in acceleration during daily drivingand in the 1/4 mile by upgrading to a 4.50 or 4.70 FD?
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Old 08-30-2007, 11:08 PM   #8
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Default Re: (excivicboy96)

why was the original post deleted?
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Old 10-02-2007, 03:12 PM   #9
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Default Re: (vinuneuro)

yea where is the post?
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Old 10-02-2007, 07:11 PM   #10
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Default Re: (vinuneuro)

Bense moved his tech stuff to his personal site. Something about the aliens embedded in the H-T coding are eating his brain.
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Old 10-03-2007, 04:49 AM   #11
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lol ok.. i found it last night, thanks though.

i like your name btw
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Old 11-30-2009, 11:08 AM   #12
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Default Re: How to fine tune your gearing for optimal 1/4 mile acceleration.

updated
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Old 12-05-2009, 09:47 AM   #13
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Default Re: How to fine tune your gearing for optimal 1/4 mile acceleration.

Interesting Bense, but I am confused. I am working on my own performance calculator, and have added the ET and terminal speed equations in to it, but they do not update if I change gear ratios.

However, changing to shorter gear ratios would surely improve the ET and trap speed? By my calculator, swapping from a 4.4 to a 4.9 FD on an EK4, drops the 0-100 time from 16.2 to 15.8, so surely the trap speed and ET would be different too?

So far the variables in my calculator are:

Weight
Average net torque
Tyre dimensions
Gear ratios
Rev limit
Estimation of traction improvement with LSD.
Gearshift time

This works out:

Power
Torque at the wheels in each gear
Acceleration in G per gear
Estimation of taction
Speed per 1000rpm in each gear
Speed at rev limit per gear
Shift point and rev drop between gears
Time in each gear
Time through gears
0-60 thru gears
0-100 thru gears
30-50 in 2nd
30-50 in 3rd
30-70 in 3rd
50-70 in 3rd
50-70 in 4th
60-100 in 4th.

I wonder how I can accurately calculate the trap speed and ET having got this much worked out?

(I have yet to add in rolling resitance and aero drag, if anyone knows how, let me know!)
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Old 12-05-2009, 01:57 PM   #14
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Default Re: How to fine tune your gearing for optimal 1/4 mile acceleration.

If you take a look at my thread in the FAQ you can see how gearing affects 1/4 mile times. I need to update it, but I have the same thread in the 92-00 Civic forum that is up to date (as of the last time I ran it to compare gearing in 07).
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Old 12-05-2009, 04:04 PM   #15
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Default Re: How to fine tune your gearing for optimal 1/4 mile acceleration.

Komodo, developing an accurate mathematical model to calculate all of these factors is something that is going to be pretty much beyond the scope of this forum. Not to say that it's not welcome, but what you're trying to do is essentially something that involves numerical methods, differential equations, and a lot of time and effort.

Look at the gran turismo games for example. The advanced physics engines in those games have got to have some way of factoring all of those variables.

Remember that when people say "makes 375 whp" or whatever, this is the peak. And obviously the rpm range isn't going to reflect 375 whp for the entire duration of the shift.

Anyways, if you're really serious about developing that project, I'd suggest picking up a numerical methods book. These are excellent books.

http://www.amazon.com/Applied-Numeri...0061395&sr=1-7
http://www.amazon.com/Numerical-Meth.../dp/0073101567

Sorry I can't offer more help.
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