What to go for F15 or F17 or stick with F13WR? HELP

[NovaNeil]

Im really stuck! I need a gearbox. I know lots of questions have already been asked loads already about these 3 boxes. But i'd like some advice.
As some of you might already be aware I have a 1.6 Turbo with an F13WR box in it which is great for it high ratio 4th & 5th for cruising and top speed. But im getting a Diff soon and I have a Helix clutch ready to fit which means the box has to come out. So do I keep it? or put another one in? Thing is I want as fast a 1/4 mile time possible. Is the F17 or F15 going to be better for this and if so why? At the moment im crossing the line at about 5300rpm in 4th @ 99mph if this helps.

Has anyone tried the F17? Im tempted to give it a try and see what the difference is.

Cheers for any help/advice

Neil

[Aragorn]

i know ive aswered this before for u but here goes...

if u want quarter mile times then u want an F13CR or F15 with a 4.18 final drive

the F13CR, F15 and F17 are identical as far as ratios are concerned

15 and 17 being newer than the 13 but not neccesarilly stronger

ive looked into this a bit for my own car and finally decided that wacky outright accelleration may be fun - but the majority of driving i do is constant speed motorway/dual carridgeway style driving

i decided to plump for the box you have and im perfectly happy with the ratios thats in it BUT its all down to personal choice - i couldnt be arsed with motorway crusing at >4k

my current box allows 70 at 3k and 95 in 4k so its better suited to my driving NEEDS

[Dicko]

yes but were talking about a turbo here so its not 'quite' the same as NA engine. even with very low lag he doesnt wanna be having a box as low as the f13cr, itl be pure spin.

[Aragorn]

ive got a spreadsheet kicking around somewhere that cambridge done

ive modified it slightly to make it easier to use and added a more sensible graph at the bottom (rpm vs speed) rather than the previous one which was a bit harder to understand (i think his was working out the RPM required for a fixed set of speeds rather than the SPEED attained from a specific set of RPM's which makes more sense)

also fixed one of his formulas for the tire circumference where he was only adding the tire wall radius once rather than twice which was cocking the results up a bit

i just need to input the ratios for the CR box then ill post it up and u can have a fiddle :)

but basically u choose the box - input the tire sizes and select a final drive then it provides a graph of speed in each gear

you can also set the rev limit so it gives u the proper top end for each gear

[ydg27]

in the comment above it says speeds can be calculated for gears,
can this be done for mine
f13cr
195/45/15
(1.7td)

if so can ya post it below, cheers

[NovaNeil]

Nice one! That should be good to have a play with. Cheers

Has anyone got an F17? It seems lots of people talk about it but no-one seems to use it.

I need long ratios because of the amount of torque produced low down.....As Dicko said, it would just spin the wheels on the spot with an F13CR.

[cmatty]

Can't a big block box be modified for the small block engine like Dav did on his 1.6 8v turbo. He got a clutch plate made and uses 2 litre driveshafts with a f16.

[Aragorn]

right...



http://www.kevingalloway.demon.co.uk/gearbox%20graph.xls

there ya go

ydg2 just mind and adjust the rpm intervals for your engine ;)

and mind and select the corresponding gearbox from the tabs at the bottom