(T) MPG PROBLEMS!!

hello, i hae got a punto mk2 GO 1.2 8v.

i used to get about 40+ mpg according to the computer cloc but since i hav fitted a set of 17" i only get 30/32 MPG is there meant to be such a great difference. if anyone has had the same problem could they please tell m cos i might put it in the garage.

thanx for you help Marc.

As far as i know the larger the wheels the less performance you'll get out of your car... Apart from the fact they're heavier, the larger circumference means more revolutions of the wheel per mile.... meaning you have to rev the engine more for better performance. Am i right peeps back me up ?!!

Cinq owner, Punto on the way!

96 N Cinqo Sporting
Rosso Sporting Red
57k

You may find its the rolling circumferance difference that has put the calculations way out for the trip computer. You need to ensure that you havent changed your RC too muc as you speedo will be out as well. There are a number of online circumferance calculators, but our Bravo/a Owners site does a direct one for you.

www.fiatboo.co.uk
scroll down to the links towards the bottom.
Nige

Fiat Punto JTD
Fiat Barchetta
http://www.angeltuning.co.uk
http://www.bravo-guide.co.uk THE Fiat Bravo site

When you fit larger wheels, the car 'thinks' it's covering less distance because the speedo and trip computer count the number of revolutions of the wheel to measure distance. Therefore, if you fit a wheel with a larger diameter, when you travel 1 mile at 60mph, the car thinks it's only done (for example) 0.8 miles at 48mph, despite the fact that you've use 1mile@60mph worth of petrol - hence the low mpg.

There's no way of sorting this out at the trip computer - instead get lower-profile tyres so your circumference matches the standard. Should be 195/40 R17.

try this site out http://www.miata.net/garage/tirecalc.html you stick in yoru orgional tyre and rim sizes do the same with ya new ones and it will tell you what the difference in circumfrence is if any. also wll tell you if your speedo is lsightly out due to new wheel size

alfanige & joemck - Wrong, the car is actually covering more distance (only a fraction of a percent), the car "thinks" its covered the same as it always does.
RE: trip computer - there is no relation between the speed at which you drive and the MPG it displays.
Elchinko - spot on, the weight of the wheels reduces performance as it needs more power (more fuel) to move the car BUT
Even though the alloy is larger the tyre will be smaller leading to a very similar rolling radius. Many people have noticed (as have I) that a 16" alloy with 195/45/16 tyre causes the speedo to be totally accurate.


www.puntoforum.co.uk

Evil-Punto AKA Evilution.