Gear Ratio Calculator/Grapher

[Guest lan_killa]

Ive built up this excel spreadsheet to as accurately as possible Calculate and Graph Speed Vs. RPM for your vehicle.

Very simple to use, download it here: RATIOCALCGRAPH.xls

Enter in your gear ratios, final drive ratio, tyre size and RPM limit and it will produce a graph showing RPM Vs. Speed in each gear. The spreadsheet is only setup to map out to a maximum of 10,000RPM. This can be used on 1, 2, 3, 4, 5 and 6 speed transmissions, simply enter 0 for your ratio on gears that you dont have.

If you want to see more detailed data, click on the DATA sheet at the bottom of the page.

To find out what your ratios are find your gearbox code on this site: http://www.catherineandken.co.uk/sti/trans.html

I hope some of you find a use for this

[Joker]

nice

[funkytown]

cool..

out of interest - i used the standard 6mt ratios (they are all the same)..

rev limit : 7500

Tyre width: 215mm

Tyre Profile: 40%

Rim Size: 18

Tyre Diam: 24.77

are those correctish?

equated to top speed of 270kmh....

[Guest lan_killa]

thats quite possible...

The values that are in the sheet when you first open it are my car, which has a top speed of circa 240kph... In the past I have seen the speedo hit 180kph in 4th at 6500rpm ish, and this graph says exactally that

But quickly heres the math behind it

RPM: 7500

6th Gear: 0.842

Diff: 3.900

Tyre Diameter: 24.77inchs

0.842 * 3.900 Diff = 3.2838

6th Gear multiplied by the Diff ratio gives us a final ratio of 3.2828:1

7500/3.2838 = 2283.94

Every 7500 revolutions the crank does = 2283.94 revolutions of the axle

so 2289.94 = Axle/wheel RPM

24.77 * 3.14159 = 77.8171843

Tyre Diameter multiplied by PI to give us a circumfrence of 77.8171843 inchs

77.8171843 * 2289.94 = 177729.73

Distance covered per wheel multiplied by wheel rpm = 177729.73 inchs per minute

177729.73 * 0.000 015 782 828 283 = 2.80507780937395359

This is converting from inchs to miles so we get 2.80507780937395359 Miles per Minute

2.80507780937395359 * 60 = 168.30

This is converting from minutes to hours so we get 168.30 miles per hour

168.30 * 1.609344 = 270.8525952

This is converting from MPH to KPH and get get 270.8525952KPH

Looks right to me

One thing to take into account is tyre size, this can change things HEAPS. Also as your tyres wear they get smaller so your top speed becomes less

[Koom]

Why'd you use miles and inches? The world is trying to move forward you know

[Guest lan_killa]

meh... piss off blame the japs for still using imperial wheels

[Joker]

Tire diameter is in inches... yet width in mm go figure....

[Guest lan_killa]

sidewall height in percentage of a metric measurement... yup... tyre sizes are all sorts of fucked up

[Koom]

 lan_killa said:

meh... piss off blame the japs for still using imperial wheels

haha. Rollin on 558.8's doesn't have the same gangsta sound to it.

[funkytown]

so me thinks - 270 sounds crazy fast, and almost impossible to test anywhere.

Lots of people do track / rally / drags etc,

How and where is one able to do legitimate top speed testing?

* if anyone says the salt flat "I SLAP YOU >:("

Im being serious in asking, i've manged +240km once but that was in another vehicle on a less than ideal (but legal) location. Im interested to try for more

[Joker]

i had a list somewhere of speed record roads in nz...

 

Goudies Road, Reporoa

is one

Burt Monro used Oreti Beach

[newsuba]

 funkytown said:

so me thinks - 270 sounds crazy fast, and almost impossible to test anywhere.

Purely theoretical v max., with no regard for physical environment or factors like aerodynamics.

To regard as gospel is a bit like thinking your car really will do the big numbers on your (non-JDM) speedo.

;D

[funkytown]

right - ignore 270, and put xxx in, where can one test

[Joker]

 Koom']

[quote name='lan_killa said:

meh... piss off blame the japs for still using imperial wheels

/quote]

haha. Rollin on 558.8's doesn't have the same gangsta sound to it.

haha similar to 12" is still more impressive to wommin than "its 300 millimeters baby" (or for most of you's 200mm)

[Guest lan_killa]

dont think the closed road lets see how fast you can go thing happens too often, and to quailfy to enter would be fairly strict I imagine, They use that day/road for setting the NZ Land Speed records...

About the only options are SALT FLATS (OMG I SAID IT!!!!) or the autobhan

[Joker]

last one was when all those Top Secret built cars came over from Japan IIRC

was in NZPC

is a road around palmy, one near Hamiton that has also been used Canal Road IIRC

[Koom]

 funkytown said:

right - ignore 270, and put xxx in, where can one test

http://en.wikipedia.org/wiki/Ehra-Lessien

Or failing that apply for road closure of Tram road in Canterbury. Or go to the Australian Outback (they have a salt flat too )

You need a really long straight anyway and NZ's racetracks don't have huge straights (Puke would be best?)

[dubbedup]

 Koom']

[quote name='funkytown said:

right - ignore 270, and put xxx in, where can one test

/quote]

http://en.wikipedia.org/wiki/Ehra-Lessien

Or failing that apply for road closure of Tram road in Canterbury. Or go to the Australian Outback (they have a salt flat too )

You need a really long straight anyway and NZ's racetracks don't have huge straights (Puke would be best?)

Good link!

[Munkvy]

The HSV Club used to close off a road near Carterton in the Wairarapa and do 1km flying sprints. Im pretty certain it wouldnt be that hard to do so again. However you would need to get it done by an actual motorsport club to have any chance of setting it up. Could perhaps talk to Wairarapa Car Club as its their area.

Alternatively, Ohakea used to run days for Armed Forces personnel. But pretty sure you cant get in if your not in one of the Services.

Your car should see some interesting speeds at MM however on the front track. However use GPS, not the speedo to guage actual speed.

[funkytown]

 Munkvy said:

The HSV Club used to close off a road near Carterton in the Wairarapa and do 1km flying sprints. Im pretty certain it wouldnt be that hard to do so again. However you would need to get it done by an actual motorsport club to have any chance of setting it up. Could perhaps talk to Wairarapa Car Club as its their area.

Alternatively, Ohakea used to run days for Armed Forces personnel. But pretty sure you cant get in if your not in one of the Services.

Your car should see some interesting speeds at MM however on the front track. However use GPS, not the speedo to guage actual speed.

it "should do yer" but not that much more than about 220 i would pick.. last outing i was already well out past the 180 "indicator"..

thanks for the useful info too

[Munkvy]

Random trivia - according to the speed sensor used by the Link in mine 195km is almost straight down on the dash, so well past the 180km mark.

[Guest keltik]

237kph in mine is just touching the stop by zero.

Goudies road is ok.....but SH38 past Kaingaroa forest is better

Am about to stick some numbers in this spreadsheet to see how my frankenbox will drive. I want a 4.111 diff in a V2 WRX box.

[DRFVDR]

I been a tad over 250km/hr

the M1 in England at 2.30 am

in a BMW M3

racing the salesman in his BMW 850 i

Oh when i was young and foolish

[Joker]

heh - what was wrong with the top sped calc on the catherine site? apart from being in mph...

same result 269.54

TY752VBCAA (BG5C GTB)

would be cool if you could just copy paste gearbox code rather than all the values

[funkytown]

 JoKer said:

would be cool if you could just copy paste gearbox code rather than all the values

everyone runs different wheels and tyres though - so you have to do some input regardless..