Running a 893cc blade in a Mk Indy chassis with a 2.3 Diesel diff (3.14, i believe) With 195/45/15 tyres. Does anyone have a formula so i can work out road speed in various gears @ known revs.

Andy

cant be too hard.
Work out tyre circumference and times by the RPM at wheel will give you distance/minute.
Quick conversion will give u MPH

SO few things you need to know:

Gearbox ratios,
Final Drive Ratio
Wheel circumfrence nd ur away

Im bored so give me 15 minutes or so ill have knocked up an excel sheet for u all.

What a star

there is various spreadsheets on the NET, but after several goes, 84mph in first @ 11k, just dont seem right !


Andy

has anyone got any known speeds including their gear ratio and final drive ratio for me to test it?

dont want to post it with any schoolboy errors and look like a fool

a 195/50/15 tyre when laden moves 1.56 metres in 1 revolution.
there are 1609.344 metres in a mile.
If your engine does 11000 revs in 1 minute then it does 660,000 in 1 hour.

divide the revs per hour by your 1st gear ratio, then by your primary reduction ratio, then by your diff ratio. That gives you the revs of your wheel per hour. Times that by, say, 1.5 metres circumference and you get metres per hour. divide that by 1609.344 and you have miles per hour.

remember that the radius of your tyre is probably 10mm more when new than old and will vary with tyre pressure and temperature so don't work out your MPH to any decimal places and hope for it to be absolutely right.

Some real data for your spreadsheet.


195/45/15, i got 21.5" od , 68" curcum

box ratio 1st=2.76
2nd =2
3rd =1.76
456 , cannot remember the rest
diff 3.14

by my reckokning you will be going about 80 in first:S i think ive messed up somewhere

oops forgot primary ratio

Try this

I think ive cracked it:S

what the primary reduction ratio ?

Can someone give it a go with what theyve got and know?
I think ive got it all sorted

Primary reduction is the reduction from engine to gearbox

i believe its 1.13 on the blade

[Edited on 19/5/08 by Miks15]

@11000 rpm

1st = 82
2nd = 114
3rd = 129

ken i think thats without primary redcution ratio?

i got 72 in 1st

[Edited on 19/5/08 by Miks15]

blade primary reduction is 1.5. i would doubt it would pull max revs in top with a 3.14 diff unless on a long downhill slope.

[Edited on 19/5/08 by bigrich]

My 954 does 58-59mph in First with a 3.62 diff on 205/50/15's.
I can just about hit the limiter in 6th..... but would be interested on the changes a 3.14 would make to it!