How do I work out the maximum speed I can expect?

I have a Vauxhall XE - 6500-700 rpm
Type 9 Box
3.62 LSD

Must be a formula somwhere!

Engine rpm divided by gear ratio of highest gear divided by final drive times outside diameter of tire.

I belive that is it, I might have my multiplication and division mixed up.

Anyone know what ratio 5th gear on the type 9 is then?

you need to know what size tyres you will be running and the gear ratio's in the type 9 box.

Its all pretty irrelevent if your building a 7 style car because you will loose the aerodynamics battle long before you attain maximum revs in top gear with a XE lump and a type 9 box i would think.

max theoretical speed = gearing. max real speed also = air resistance, rolling resistance, and the size of your balls

There is a spread sheet about for a type 9 box that allows you to enter these parameters and get speeds for each gear (theoretical)

anyone have a copy?

atb

steve

[Edited on 21/7/04 by stephen_gusterson]

I have a great spreadsheet in excel, email me or u2u and I can send it to ya, or maybe tonight I caqn post it on my webpage and you can get it there, just remeber, my tonight is 5 hours after your tonight....

and steve is right about the last part of the equation...ball size....

David

get the speed calculator off quaife's site and search the web for type 9 gear ratio's (5th is 0.87 from memory). easy.

Ned.

Try this attached excel file (thanks to Rob Lane I think). I put in ratios for ford type 9, 5 speed. (3.656, 1.97, 1.37, 1 and 0.82 to the best of my knowledge - also very probably thanks to Rob Lane)

You need to input your tyre diameter (in inches) and diff ratio.

Note that the given terminal velocity assumes you have enough power at the wheels to match the wind resistance!

regards
Dave

[Edited on 21/7/04 by Dave Ashurst]

thats the one I was referring to dave!

atb

steve

You want to use a DOS program that was free on the web called (from memory) "cartest"
You tell it all sorts of stuff about the car & it tells you all sorts of stuff about its performance & simulates laps round various tracks. Data input includes wheel size, frontal area, drag coeff, gear ratios, diff ratio etc. etc. + you can put in your engine power curve. Google should find it....
cheers
bob
PS simple XL gear ratio calculator probably useless - if you can reach max revs in top your gearing is well screwed!- very much a sprint/trackday special.

Hopefully it will work.

Sort of like Dave's only different



David

[Edited on 22/7/04 by white130d]

According to the spreadsheet using 205/50/15 tyres I should get 148 mph at 6500 rpm!!!

Scary!!!!

these things only work on mechanical garing, remember nothing is taken into account for air/wind resistance, rolling resistance etc. you need a lot of power to pull much over 120-30mph i a 7 due to aerodynamics for example.

Ned.

every 10 year old knows that the speed of a car is related to the max figure on the speedo.

Get a 220mph marked speedo and it will be a ferrari beater!

atb

steve

Have you lads stopped wasting time with gear calculators & tried www.cartestsoftware.com
yet? Very comprehensive & seems to give the right answers with "normal" cars. Only problem with BECs is rev limit of 10000 - I had to multiply torques & cc's by primary reduction ratio to get sensible answers (R1 BEC with 133bhp max speed 135, 0-60 in about 4).
We could have a virtual race series round nurnbergring if you want.......
Cheers
Bob