Author Topic: worsererer fuel consumption (Read 4116 times)

matsu · « **on:** November 27, 2009, 08:24:02 am »

hi guys
since ive changed the rims to 19s and silly low tyres my dash tells me i now average about22 mpg and it was never below29 before-
is it the actual figure due to less effecient tyres or is it the computer calculating it differently due to the esp light flashing a few times or am i just a numpty not understanding any of this?

matsu

RedRobin · « **Reply #1 on:** November 27, 2009, 09:12:48 am »

....

Hi matsu,

Sorry if this is a silly question but have you checked whether you are reading a '1' or '2' value? Meaning whether it's an overall mpg or trip mpg (I forget which is which).

Even if your wheel+tyre combo overall diameter had significantly changed I wouldn't expect mpg to change but possibly mph. But I'm not an expert on this.

Teutonic_Tamer knows a lot about such things but he's not around at the moment.

Garth · « **Reply #2 on:** November 27, 2009, 09:24:29 am »

Probably due to the heavier wheels.

I've just gone from 17" wheels to replica 18's and my fuel consumption has gone from 36mpg average to 32mpg. Nothing else changed and they're almost all motorway miles.

RedRobin · « **Reply #3 on:** November 27, 2009, 09:40:25 am »

Quote from: Garth on November 27, 2009, 09:24:29 am

Probably due to the heavier wheels.

I've just gone from 17" wheels to replica 18's and my fuel consumption has gone from 36mpg average to 32mpg. Nothing else changed and they're almost all motorway miles.

....So does that mean that by going from 12 Kg Monza'a to 8 Kg Alleggerita's my mpg has improved?

In fact my mpg readout has improved but I didn't think it was down to my lighter wheels. I just thought it was a change as none of my journeys are very rarely the same.

Hedge · « **Reply #4 on:** November 27, 2009, 10:05:47 am »

Have you changed the rolling radius of the wheel compared to stock?

tony_danza · « **Reply #5 on:** November 27, 2009, 10:18:37 am »

Have you got some Alleggeritas, Robin??? You never mentioned it.....

Takes a lot of force to get something spinning, and the heavier and bigger diameter it is, the more force it takes. Likewise stopping it again.

Garth · « **Reply #6 on:** November 27, 2009, 10:30:21 am »

Quote from: RedRobin on November 27, 2009, 09:40:25 am

....So does that mean that by going from 12 Kg Monza'a to 8 Kg Alleggerita's my mpg has improved?

In fact my mpg readout has improved but I didn't think it was down to my lighter wheels. I just thought it was a change as none of my journeys are very rarely the same.

Possibly, yes.
Most people don't even consider the weight of wheels but it does make a difference for for performance and economy. If your car's trying to turn 4 lumps of lead, it's going to use more fuel than turning 4 biscuits!

Hedge · « **Reply #7 on:** November 27, 2009, 10:35:11 am »

Matsu - what size tyres are you running as you have changed to 19"s?

VWellsy · « **Reply #8 on:** November 27, 2009, 10:37:44 am »

Nice analagy, I assume by biscuits you mean Hob-nobs. As cornering on anything less could be interesting!!!

Garth · « **Reply #9 on:** November 27, 2009, 10:57:30 am »

Quote from: VWellsy on November 27, 2009, 10:37:44 am

Nice analagy, I assume by biscuits you mean Hob-nobs. As cornering on anything less could be interesting!!!

I was actually thinking of rich tea's as they're super-light!

RedRobin · « **Reply #10 on:** November 27, 2009, 11:20:02 am »

Quote from: tony_danza on November 27, 2009, 10:18:37 am

Have you got some Alleggeritas, Robin??? You never mentioned it.....

....Would you like to see pics? And I can also post you a link to my review of them if you like

I thought it may be useful for those who don't already know the kind of weight differences there are between wheels. Who knows, it could even lead this discussion to calculating that a weight saving of x Kg gives an improvement of y mpg - all approximately of course.

tony_danza · « **Reply #11 on:** November 27, 2009, 12:13:29 pm »

Ha ha - Nah, keep it up.

We have a special area of the forum where we play RedRobin Bingo - I've only got to get "Quaiff" before 1pm and I win a speedboat.

And with that leg pulling, I'm off - Cheeky 1/2 track day at Oulton Park is calling... bwaaaapp!

Hurdy · « **Reply #12 on:** November 27, 2009, 12:45:51 pm »

Matsu,

Take comfort in the fact that I'm on lighter wheels and my average fuel consumption is around 18.7mpg. My current tankful is 115miles travelled and 90 miles left to empty = 205 miles from a tank

and

in equal measures

matsu · « **Reply #13 on:** November 27, 2009, 12:48:50 pm »

thanks for the input i am running ....the wheels are 19x8.5 et45 and the tyres are falken fk452 215/35zr19

not sure how much diff that is to standard 17 monzas(still for sale plug plug)

my driving is not any different with the exception i,m looking out for potholes and i take corners way steadier due to the flare on the rim with no tyre protection.

also my esp light came on twice but i am very numptynewbie and not sure what i should have done at that stage- does that make the computer calculate differently?

i dont think they are that much heavier to be honest,but thats in laymans terms whist changing them over?!!

hope thats enough new info to find an answer?
thanks again
matsu

matsu · « **Reply #14 on:** November 27, 2009, 12:51:13 pm »

lol hurdy- i,m not actually worried cos i,m velly velly hoppy with my car-and will be even happier by end of jan if my next mods come off,-i just wanna make sure i understand why and if i needed to do anything to her when i changed the wheels-cos i didnt
fanx mate

matsu