A close ratio box with 6th like std 5th

Post by **campbell** » Sun Apr 08, 2007 9:58 pm

I like my S1 cruising at 3k rpm @ 70mph.

But I always fancied the snap-shifting experience and mild power delivery benefits / "feeling" of a CR box.

Does this box blend the best of both? ...

http://www.quaife.co.uk/Lotus-Elise-6-s ... inal-drive

Or is it the one where it's 6 ratios squeezed into the space of the 5 from the S1 CR box?

Lorra lolly right enough...Maybe once I get my head round calculating ratios vs final drives etc, I could spec a new set of custom 5 speed cogs to go into my current housing. It probably needs a rebuild one day soon anyway

Campbell

robin · Post by **robin** » Mon Apr 09, 2007 7:34 am

Campbell, your fifth has a ratio of 0.77:1 and you have a final drive of 3.94:1, i.e. total ratio is 3.03:1

The quaife box has sixth of 0.861:1.
Combined with 3.694:1 final drive gives you 3.18:1.
Combined with 3.955:1 final drive gives you 3.40:1.

3.03:1 is 22.9 mph/1000 rpm (i.e 70mph is 3050 rpm).
3.18:1 would then be 21.8 mph/1000 rpm (i.e. 70mph is 3200 rpm).
3.40:1 would then be 20.4 mph/1000 rpm (i.e. 70mph is 3400 rpm).

Now the C/R box has 19.4 mph/1000 rpm in 5th so I think any of these options would be better than the C/R box for cruising, but none as good as the standard box.

Cheers,
Robin

Post by **campbell** » Mon Apr 09, 2007 8:27 am

The 3.694 final drive is getting close though. Unfortunately a £3k+ upgrade for just a gearbox seems a little excessive

Wonder if we can find anyone who has tried this?

And the other question would be...would there be any point in asking Quaife to supply a further reduced final drive, say about 3.55, or whatever made 6th = 22.9mph per 1000 rpm

Or would that just screw all the other carefully designed ratios!

I guess I will wait until my gearbox blows up, or similar, and then decide.

All v interesting stuff though! And ta for the worked example, hopefully I can do my own math next time

Campbell

thinfourth · Post by **thinfourth** » Mon Apr 09, 2007 9:29 am

But it is straight cut

not so sensible for the road unless you are completely deaf

alicrozier · Post by **alicrozier** » Mon Apr 09, 2007 9:58 am

Nope, it's helical...
"...6-speed synchromesh gearkit, with helical cut gears, in close ratios, including a final drive from a choice ratios..."

Post by **campbell** » Mon Apr 09, 2007 10:13 am

Thank you Ali, thought I was going mad there! No way I'd pick a straight cut box for the road. We are talking about Mr Sport Tourer Spec here after all (they just hadn't invented that badge when I bought my car!!)

Anyways, like I said above, it's scary expensive for what it offers so chances look slim.

I have heard that you can spec ratios to some firms and create a custom box...so if mine was due a rebuild in any case, maybe I'd get 3rd and 4th set part-way towards the CR box ratios, and even leave 5th alone (or take it up just to the ratio that would give about 3200 rpm in 70mph). That would keep the spread of ratios fairly stable whilst putting the car a shade higher in its new powerband on each change-up than it is currently.

Hmmm.

Campbell

thinfourth · Post by **thinfourth** » Mon Apr 09, 2007 11:48 am

alicrozier wrote:Nope, it's helical...
"...6-speed synchromesh gearkit, with helical cut gears, in close ratios, including a final drive from a choice ratios..."

Ah they must have two kits as i went to the link got distracted by landrover bits and went back to lotus stuff after realising that i don't need this

That would be a silly idea

Post by **campbell** » Mon Apr 09, 2007 12:13 pm

LOL!

You always know you don't need something when the tag says "£POA"