Technical Gears gears gears!?

[Hansdans]

Good day Gentle and ladiesmen! Hope all is well where ever you are.
I own a strada 2006 1.7td 72hp, it does 3100 rpm at 100kmh. It has absolute DOGSHIT fuel economy long distance, (13.5kmpl ac used) attached images show palio td doing 2500rpm at 100kmh, and youtube screenshots of a 1998 1.7td doing about 2300 rpm at 100kmh, if you didn't know it a diesel fuel economy is mostly directly associated to rpm, the fiat engine 178a3 1.7td has all its torque from 1800 to 2600 rpm,

Fuel prices only ever go up.....
Palio qouted milage highway is 5.1/100km punto is 4.9, my strada is 7.7/100, exact same engine

Local the palio 1.7td gets more economy at 120kmh than i can manage at 100kmh,

PLEASE any info on the differential final drive ratios i wil highly appreciate, especially part numbers on that 98 punto 1.7 ring and pinion gears , local shops even dealers are clueless, i am in south africa KZN, i have a spare box and looking to swop in a better ratio diff ideally 2200 rpm is sufficient , again local info /resource is very limited, hoping to gain some info from the hive mind, TNX.

 

[bugsymike]

Don't know specific about Strada but generally turbo diesels run much more economically than non turbo as the power comes from burning more oxygen, common rail diesels are even more efficient.
Re gearing if possible clearance wise could you fit larger wheels to raise gearing or higher profile tyres, both of these changes are easier than diffs, but will affect the speedo accuracy, also when working out economy per kilometer etc remember the bigger wheel/tyre will cover a larger distance per revolution.
However if engine power is the same then pulling away up steep hills will be harder.

 

[Hansdans]

Tnx, for the input, im aware of that modification however vehicle already comes with 14 inch and 80mm profile so would need 4 new wheels and tyres and not looking to do that, finding the fiat punto ring and pinion likely means that the fiat speedo cable could also be fitted as the gearbox is ubiquitous across many models only the diff ratio differs, im not really worried about the pullaway torque loss as 1st is almost a crawling gear currently,and for overalp performance loss its dead easy to wind in 3 psi of boost and still remain stock otherwise, stock boost is 7psi peak and is non intercooled, it is possible to go up to 1 bar non intercooled so 10 psi is reasonably safe .

 

[bugsymike]

Tnx, for the input, im aware of that modification however vehicle already comes with 14 inch and 80mm profile so would need 4 new wheels and tyres and not looking to do that, finding the fiat punto ring and pinion likely means that the fiat speedo cable could also be fitted as the gearbox is ubiquitous across many models only the diff ratio differs, im not really worried about the pullaway torque loss as 1st is almost a crawling gear currently,and for overalp performance loss its dead easy to wind in 3 psi of boost and still remain stock otherwise, stock boost is 7psi peak and is non intercooled, it is possible to go up to 1 bar non intercooled so 10 psi is reasonably safe .

Sorry , not trying to "teach granny to suck eggs", justsuggesting a cheap option, one I have used in the past, often steel wheels from a van.
Any chance a 6 speed from a later version with more of a overdrive top gear?

 

[Hansdans]

Yeah i understand but 4 new wheels and rubber breaks the bank, and i dont think will give me the 30% rpm drop im chasing without looking silly, Different engines 1.3jtd and 1.9,jtd is all we got here but they are crd units and may be new blocks so im not sure if the bellhousing/ gearbox sideshafts bla bla are plug and play, wel i recieved the gbox today and was sub 100 pound equivalent shipped in my weak ass currency, im open to a 5th gear swop out also, geuss ill strip of the gbox side and take it to a shop or engineer to asses whats do able, might need to combine both diff and 5th gear swop , fuel as of yesterday is 26.40 zar per liter.... also once this box is modded and fitted selling old one can recover something

 

[bugsymike]

We are paying roughly £1.55 Sterling for a litre of petrol!
Equivalent to 36.24 Zar?

 

[Hansdans]

We are paying roughly £1.55 Sterling for a litre of petrol!
Equivalent to 36.24 Zar?

Sucks to be eurolanders then 26 is alot here in our weak tea currency..