Final drive ratio for 4 speed x1/9

Road-race engines and ancillaries - general discussion
Charlie
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Final drive ratio for 4 speed x1/9

Post by Charlie »

Hi,
I have just completed a supercharger conversion to a 1300 Fiat x1/9
and now need to change the final drive ratio to complement the increased
performance. The standard final drive ratio is 4.07 : 1 and I believe that a
3.77 :1 ratio is available for the 4 speed gearbox. Any help in aquiring these parts would be mush appreciated.

Charlie.
Guy Croft
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Re Charlie's request for help

Post by Guy Croft »

Hello Charlie

you are a bit alone with your question, typical of forums, wait weeks and no answer.

I'm sorry, I personally do not know but if anyone has the faintest idea of the answer let's hear it and quickly please!
I'm not waiting 5 years from own forum and then letting the grass grow under my feet..

This is the forum where I get things sorted guys.

Thanks,

GC
Kev Rooney
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Joined: June 26th, 2006, 7:29 am
Location: Portsmouth

Post by Kev Rooney »

Depends what sort of performance you are looking for ? A taller diff ratio ( lower numerically ) will decrease acceleration and increase top end and vice versa.
Have your mods increased your available rpm or just increased available torque?
The best bet is to be realistic about how you want to drive the car and is it to be purely road or some 'track day' work ? Then select what gearing will achieve your requirements.
Charlie
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Post by Charlie »

Firstly, the car is not for track day use, so acceleration issues are not that high on my priority scale. Actually with the supercharger set up the car will accelerate briskly up fairly steep hills in fourth gear from 3000rpm where previously you would be flogging it in third. The large gap between third and fourth gear dose not exist any more. With the amount of torque
now available fourth gear is just to low. I know that a five speed box from a 1500 with the 1500 drive shafts, hubs and some small structural mods will do the job, but I would rather retain my four speed and change the final drive ratio. Apparently a Lancia Delta 1300 GT 4 speed box has a 3.77 :1 final drive ratio which is the one I want and I think some of the 128 models had this final drive ratio as well .
Kev Rooney
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Joined: June 26th, 2006, 7:29 am
Location: Portsmouth

Post by Kev Rooney »

If you have a rolling tyre diameter I can tell you how much difference the gear change will make ie mph/1000 rpm to see if it wil achieve your goals ?
sumplug
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Post by sumplug »

exxie 4 speed box is the weak link. it can not cope with the power increase. you can use the strada/delta internals. dont know why you dont want a 5 speed box. the later tipo/uno box is much stronger with better gearing. plenty out there going for buttons. :)
Charlie
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Location: Ireland
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Post by Charlie »

The reason that I don,t want to change to a 5 speed box is because apart from the" supercharger" the car is in near concurs condition . 1300 x1/9's are thin on the ground and I have carried out the supercharger installation without any cutting or hacking off anything in the
engine bay. The car can be returned to the original speck quite easily and I have kept all the original engine components that were changed during the conversion. The 5 speed box is actually not as reliable as the 4 speed version which is good for 120bhp . although later Fiat models may have improved these issues. Fourth gear is currently 16.5 mph/ 1000rpm, 3.77 final drive ratio will give 18 mph/ 1000rpm. :)

Charlie
Guy Croft
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Post by Guy Croft »

Understood.

My advice is always to make a decision regarding aesthetics/functionality.

It may be that you have to change the gearbox internals and that being so, seeing how carefully and expertly you have undertaken the project so far, you should be talking to these people about a matching gearset & diff:

http://www.colotti.com/Engl/fiatE.htm

I have no idea whether there is any suitable OE alternative available and I would certainly share reservations as to whether it would cope with the huge extra torque anyway. I think that if there was such a thing we would have heard about it by now. that said, I do know there are a number of very expert SOHC racers in the USA, mostly members of http://www.mirafiori.com who may have another idea, one or two are already members here.

GC
Acki

Post by Acki »

I know colotti's prices for the uno turbo.
Sit down when you get's a answer ;)

Maybe price is ok when the quality is very good?!

Why you don't try to use a other gear pair from uno/tipo/punto?
It's the same gearbox. You can use the differential etc. to get your ratio.
Guy Croft
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Post by Guy Croft »

Well, I think some GC advice here.

I work at the sharp end of how much things cost. I AM one of those who gets 'expensive' rammed down my neck every day. Mostly by people I've never heard of. Colotti's price? Yes of course I know what they cost. And Quaife, Jack Knight, TranX etc etc. If you know the price: state it and leave it there. Don't remark on it, please, what they charge is not a matter for public debate here. Don't forget we're on GC's racing engine website here, racing is expensive if you want power and reliability. If you want cheap, buy from China.

I believe in the right tools for the job, engines, gearboxes, doesn't matter, money is non-issue, for me -if I cannot have it, I'll bide my time till I can. Of course price can be an issue in motorsport, but it's not the biggest issue. The question is whether you must have the thing or not, from a perfomance/reliability point of view - and - whether there is any truly suitable alternative. As I indicated earlier, someone in the USA may know.

I always advise well-infomed decisions, few make them, preferring instead to hunt around scrapyards and then agonise because the thing breaks, whilst at the same time thinking nothing of buying a ‚£8,000 fitted kitchen. At the other end of the scale I know of many tarmac/forest rally drivers in Eire who will forgo the fitted kitchen but rather spend the ‚£8000 on the six speed sequential gearbox they must have in order to be seen to be competitive, never mind win, and that's just at local level. Higher up the scale we have the guys over there who will think nothing of buying an ‚£80,000 WRC Ford Focus gearbox for the same reason. And, in absolute fairness to them, taken as a group - Irish rally drivers are the most committed and skilled - as drivers and builders of cars to be found anywhere.
And they are the dream clients because they know what they want and they don't go 'oooooh, that's a bit pricey..' I think to a great extent that they have retained an old-fashioned respect for workmanship and longevity that many other countries have lost.

As for Colotti and their pedigree they are second to none, as you will see if you read their site. I know a lot about Colotti. I imagine they feel the same as I do, I know Mr Bariani at C&B cams does, he's fed up with people 'treating his website like a sweetie shop'!!

GC
sumplug
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Post by sumplug »

guy, watch your blood pressure. dont start on about china. we know they are about to take over the world!!!
anyway, give these guys a call charlie.
http://jupiterfiatpower.tripod.com/
Guy Croft
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Post by Guy Croft »

Hi Andy,

yes, an interesting website, Jupiter, don't know them personally, but they seem to 'out there' doing the business, good luck to them.

Cannot remember where they are located. If anyone knows them well they are welcome to post a link to this site.

GC
Julian
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Post by Julian »

Jupiter racing are based in Macedonia - it might seem a strange place to have a Fiat tuning specialist but given the popularity of the Polish built cars it isnt really all that surprising.

One of my friends recently purchased a fully prepared cylinder head from them for his 1500 race engine (running in an Uno). Initial results were very good but sadly the individual responsible for assembling the engine failed to do his job and the engine was very badly damaged within minutes of starting up (another reason why we pay the real experts a lot of money for doing it right first time).

Sadly it looks as though we will not find out just how good the head is/was as it is doubtful that the head is undamaged and shipping another head from Jupiter is outside of the available budget and timescale for now.

Certainly the figures they are quoting are consistent with the results achieved by Abarth running similar setups (which suggests there may be more than a little in common). Whether or not you can realistically achieve the same when assembling the engine "at home" is another matter. It can be done of course but all too often the customer is ignorant of the fine detail work needed.
Charlie
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Joined: June 23rd, 2006, 2:30 pm
Location: Ireland
Contact:

Post by Charlie »

Thanks for the information Andy, These guys look like a good sourse for the parts that I need. I have sent them an E-mail and will up date any information on the subject here.

Charlie.
Julian
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Post by Julian »

Sorry got a little distracted - what I originally wanted to post was a commendation for Colotti. I've used them in the past and was very, very impressed with how good the service was and the quality of the resulting parts. The price may be significant but it really is worth every penny.

I think half the problem here (as in Fiat in general) is that most owners think of their cars as cheap purchases and expect cheap parts. In the UK especially this exaggerated by the generally poor residuals on the cars in general.

When it comes to custom fabricated parts the cost is much the same regardless of the car and is more related to the complexity and demands on the application than what car it is destined for.

The unfortunate aspect of this matter is that there are far too many individuals and companies out there making money out of trading second rate parts and services at top rate prices.
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