First things first......who brought my car ?? A guy came over from Wales last summer, but I understand he sold it a few weeks later.

I've been a dabbling (well paying someone else to do it, though I did hold the spanners..)

I've finally got around to changing the 4.2:1 LS diff on :-

R1 powered Silva Striker

to a 3.54:1 normal diff.

The reason for the change was that it was so high reving at 70ish mph, it made it uncomfortable to drive it along a dual carriageway. Don't get me wrong it was fantatsic on widey roads and single track by-passes. But once you get onto a dual carriageway/motorway, then it's not some much fun.

I'm slightly disappointed because it's still pulling about 9500rpm at 80mph and doesn't appeared to have made any real difference in respect of dropping the revs and therefore increasing the top end.

It has lost a small amount if acceleration and torque though, which to be fair was expected and worth the perceived trade.

It does feel slightly more willing to drive at 70-80mph and has less engine braking.

What am I to do from here ??

I understand that the R1 engine has a cassette gear box. Is it possible to change the ratio of the 6th gear to make it into an over drive, or would it be such a huge drop in revs and or torque that it wouldn't be feasible ??

Any ideas gratefully received.

It's not all rosie in the dark side of stupid quick.....the fug was far more comfortable. The seat was a bit higher but not so that you looked over the windscreen. The striker doesn't have as much scope, plus it's fitted with a funny curved roll cage, so I'd bang my head if I raised the seat in it....ho hum.

Cheers,

Steve

Knighty is your engine man, any advice?

Hi steve - I did recieve your e-mail - but for some stupid reason or another my works e-mail server does not like your e-mail address and it always bounces back.

anyways - here goes - before I start the hard stuff - are you 100% sure the new diff is to the ratio specified by the seller?........did you count the amount of teeth on the drive and diff gear and confirm the required ratio?.......or perhaps some external markings?.......but saying that 3.54 could still be wrong for your needs

I can calculate required diff ratio compared to top engine rpm and top speed on a bike engined car - I did it on my race car and it worked a treat, ordered the correct size front and rear chain sprockets, and it gave me bang on 130mph - which was just what I needed for UK race circuits.

please tell me the following, and I'll calculate it for you old chap:

1) required top speed engine RPM????.....your choice - but be sensible
2) required top speed - your choice again?......
3) primary drive ratio reduction between the crankshaft and clutch shaft
4) drive ratio between 6th gear sprockets
5) rear tyre diameter


regarding the drive ratios - it looks confusing but its not......all you need to remember that the R1 has 3 shafts

1) crankshaft
2) clutch shaft (holds 1st set of gears)
3) sprocket shaft (holds second set of gears and the chain sprocket)

when quoting the ratio - please tell me the amount of teeth on each gear if possible - all this sort of info will be available from a Yamaha service manual - possibly a haynes manual - but the latter are a bit crap nowdays..........and PLEASE measure the tyre outer diameter as accurate as possible :angry:

forget changing the R1 gear cluster at this stage - the gears are expensive and it will be major engine surgery..........I'd only do it as a last resort

once I have worked it out you may need to either get a lower ratio diff - or fit slightly bigger diameter rear tyres........probably the latter - I will reccomend a size for either way

Knighty, there was me thinking you didn't liek me anymore...sorry bloke, I forgot about the Aol glitch.


You have to leave this one with me, but I will get back to you.

Steve

dont be silly fella - if you need to talk urgently in future you have my phone numbers ;) if you cant be arsed to get all that info I requested - just thieve a pair bigger diameter ford fitment wheels from your next door neighbours and take it out for a blast - you will soon find out what wheel size you need........as a guess I think you have 13" or 14" rims.......try some 15" jobs from a focus/escort/mondeo and see how it goes :)

Knighty,

I've been thinking...........................................oh dear - there are lots of pictures on this forum of the results of my previous thoughts

Am I right from what your saying/asking, you will be able to calculate the theoretical top speed and 0-60 time, from the data supplied ??

You see, along time ago, as a young man, I would, like other young men fear not, this is legal would compare all the manufacturers 0-60 times - probably on trump cards !! Now do they all use the same driver, same track, same conditions, or do they calculate the theoretical 0-60 from data similar to that that you are requesting ???

With regard to changing the wheel size, is it only the rears that will make the difference or all 4 ??

Steve

nope I'm not saying I can calculate 0-60.......I'm saying I can calculate the diff ratio at top speed at a certain rpm........the required top speed and red-line / max rpm are down to you........obviously the greater the top speed the worse off the acceleration will be........its a compromise sorta thing.......I reckon if you aim for say 100mph or 110mph tops that will be sensible........as a 7 type kit car has the aerodynamics of a brick and get pretty hairy over 70mph so going silly speeds is not advised on the road........let me know what you want to do