Gear Ratios

[Ralphh85]

does anyone have any idea of what kind of speed they get out of each gear on v8's, since im going from an engine which revs to 7.2krpm down to the v8 which initially only does 5k its goign to drop how fast i can travel in each gear.

i will probably build a new box with higher ratio's, below is what i should be able to achive, its roughtly 10% higher than what i have now,

V8 box 5k limit - 1st - 2nd - 3rd - 4th - 5th -final drive
gear ratio -------- 2.923 - 1.75 - 1.222 - 0.848 - 0.648 3.647
top speed -------- 28.84 - 48.18 - 68.99 - 99.42 - 130.11
MPH @ 1krpm --- 5.76 - 9.63 - 13.79 - 19.88 - 26.02

48mph flat out in 2nd sounds very low to me? anyoen know what the tvr's etc achive? or any other light cars? (not landrovers).


cheers
Ralph

[ChrisJC]

Normally one changes the diff ratio rather than rebuilding the 'box.

Chris.

[Ralphh85]

Normally one changes the diff ratio rather than rebuilding the 'box.

Chris.

i have already gone to the highest final frive, which is 3.6, other available are 3.9 and 4.2,

reason for rebuild was so i could grab the high 1st,2nd,3rd from a 220 turbo box and he high 4th and 5th from the long legged deisel box. rasing the hole lot basically.


Ralph

[kiwicar]

That all looks very low, what rolling diamiter are you are you running?
If that is the best you can get and you cannot go to a bigger rolling diamiter you are going to have to add an overdrive box
Mike

[Ralphh85]

That all looks very low, what rolling diamiter are you are you running?
If that is the best you can get and you cannot go to a bigger rolling diamiter you are going to have to add an overdrive box
Mike

wheel OD is somethign like 534mm, which is why im having issues i think,

worst comes tot he worst i will go on to bigger wheels but would rather stay as i am.

still be interested to see what other cars use?


Ralph

[ChrisJC]

Normally one changes the diff ratio rather than rebuilding the 'box.

Chris.

i have already gone to the highest final frive, which is 3.6, other available are 3.9 and 4.2,

reason for rebuild was so i could grab the high 1st,2nd,3rd from a 220 turbo box and he high 4th and 5th from the long legged deisel box. rasing the hole lot basically.


Ralph

Ah yes, of course you're using the PG1.

I reckon you'll not be needing first much anyway...

[v8alex]

You've done all the calcs, but if it's of any interest, gearboxman have a ratio calculator you can download:

http://www.gearboxman.co.uk/inforatios.html

It's quite useful.

Alex

[stevieturbo]

Or here

http://www.geocities.com/z_design_studi ... z28_6.html


I guess if you could find someone to make a custom CWP....would be pricey though.

Diesel CWP's are usually the best to aim for, as they tend to have taller gearing, due to their low rpm range.