Davrian Super Saloon gearbox

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bhofner
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Davrian Super Saloon gearbox

Post by bhofner » Fri Aug 29, 2014 5:43 pm

Hi to everybody.
We where at the Salzburgring two weeks ago and we saw that the new built 1200 ccm race engine works very good. The problem is that the 5 Speed JK box doesn´t fit with the engine. To high rev to low speed. Do anyone know something which works better or where I can get a new one or who can build one.

greatings from Austria best regards
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alan c ramsay
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Re: Davrian Super Saloon gearbox

Post by alan c ramsay » Fri Aug 29, 2014 6:09 pm

Sorry I can't help with new box or ratios....

But, I would be most interested to know what ratios you have in the box, and also your estimated speed at your max. revs in top ?
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Re: Davrian Super Saloon gearbox

Post by Lotus-e-Clan » Fri Aug 29, 2014 6:36 pm

I imagine that the torquey 1200 cc engine doesn't need (or like) to be revved much beyond 7500- 8000 rpm?

My lowered top gear in the close ratio box is between 12.1 and 12.8 mph per 1000 rpm (depending on tyre size) which means 100 mph is 8250 - 7800 rpm (depending on tyre size).

On a close ratio FIVE speed box I'd be happy for 4th gear to give 100 mph and 5th gear about 125-130 mph - so a std transaxle's 15 mph/1000 rpm 4th gear ratio would be about right.

T'is a pity the std 4 speed box doesn't have closer ratios 'cos 3rd and 4th are about right for a big torquey motor but 1st and 2nd gears are far too low and the gaps are too wide. Clan004
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Re: Davrian Super Saloon gearbox

Post by The Nun » Fri Aug 29, 2014 9:32 pm

Could you fit a Hewland box to get a better selection of ratios?
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benwick3
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Re: Davrian Super Saloon gearbox

Post by benwick3 » Sat Aug 30, 2014 9:00 am

First of all you need to know what ratios are fitted to your box along with the engine power(rev) band. Then it's a case of selecting what ratios are required for the necessary speed in each gear. Worth contacting Dave Weedon (Impecunious) who should be able to help with information on which ratios are suitable and if they are available. I'm sure he will have a list of the ratios originally available from Jack Knight. If not I have a chart given the available ratios along with details on how to calculate relevant speed. He came up with a set of ratios for my JK four speed box and 1120 engine which have proved suitable for Nuerburgring, Hockenheim, Spa and Zolder. Have also worked well with both 998 and 1040 engines.

Pete Richards

p.s. Don't have any contact with the existing people who trade under the Jack Knight name unless you want to give your money away.
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Re: Davrian Super Saloon gearbox

Post by SimonBenoy » Sat Aug 30, 2014 10:39 pm

As far as I know, all the original ratios are available for the straight cut 5 speed boxes, a lot of money has been invested in having them remade. Best to ask a transaxle specialist for advice on the best ratios, but if you always use the same tyre size, know what your max revs are and the desired top speed, the best ratio can be calculated. Once 5th is known, 3rd and 4th can be slotted in to give a good spread. My steel bodied car is geared for 120+ mph (though it hasn't quite got there yet!), a spaceframe will get there quicker, being lighter and with a bigger engine, but the aero will still limit top speed.

Good luck with sorting it - Simon
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Re: Davrian Super Saloon gearbox

Post by Adrian » Tue Sep 23, 2014 10:01 am

This will give you an idea to get started with

http://www.revilo89.freeserve.co.uk/Gea ... vilo89.htm

Adrian
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