350k`s to 85 ltr`s.. 4 k`s to the ltr gq ti

[HI 75]

im getting 350 k`s out of 85 ltrs with 3.9`s auto & injected pet. & 35`s

what will i now get with 4.6`s ???(just fitted)

am doing a test now & will post what i get.

anyone know what i should expect??

cheers
daz
newcastle

[chimpboy]

I estimate that you will get 300km out of 85 litres.

[HotFourOk]

Depending on driving conditions... but if around town, wont 4.6 diffs give you better pickup with the larger tyres? Hence beter fuel economy, due to the engine not having to work as hard?

[HI 75]

im hoping for 450 k`s...
not less!!!
it drives heaps better & more power again,

[HotFourOk]

That's what i was thinking

[chimpboy]

Well, we'll find out when you've done the test. But with the old diffs, you were getting roughly 25 l/100km, which is the best I've heard anyone getting with a petrol auto GQ, especially on 35s. In fact, I find it a bit hard to believe you were doing that well before.

If you were to get 450km out of 85 litres, that's less than 19 l/100km, which nobody I know of gets from a TB42E GQ on 35s even with a more efficient manual transmission.

Sure, economy can vary depending on diff ratios but they can't do magic tricks - there's just no way you can get under 19 litres/100km out of a petrol GQ on 35s.

So my guess is based on the theory that you'll still be hovering around the same fuel economy you're getting now, or else it will get worse. It's very hard to see how you could get better than your previous figure of 25l/100km with that amount of vehicle to move, a slushbox transmission, and that much rubber.

But I could be wrong! Good luck. Anyway if it drives better that's good.

Jason

[ludacris]

Dont forget you were doing more km's than what the speedo said running 3.9's and 35's.

LudaCris

[HI 75]

i expect the speedo will give me 30k`s back & an extra 80k`s from better fuel economy....
also my foot isnt going down half as much...
daz

[not not]

And at 100klms youll have the engine at a higher rev.
When i swaped out my 4.6 ratios for 4.1 i got an increase in fuel economy. Oh and its a TD4.2t formely 2.8t so now with a 285/75/16 tire my speedo is out 20klms at 100( speedo reads 80) So i think your economy will be the same give or take a litre each way.

[shorty92]

i changed mine from 3.9 to 4.3's and i now get 480ks to the tank with 33''s thats around town i had never done that before

[bucketofbolts]

i have a 4.2ltr petrol auto, carby, and on 31's i was getting 500km's/550km's , on 33's between 400km's/450km's, and my right foot isn't very light either, on 31's, i could get from maitland to oberon, near bathurst and home on a full tank, (just)

[HI 75]

i have now got 475 k`s out of a tank. thats 5.58 k`s/ltr, instead of 4.11. AN EXTRA 125 K`S TO A TANK.
WELL WORTH THE EFFORT.THIS SHOULD SAVE ME HEAPS ON FUEL TO FRASER AND BACK AT XMAS.
CHEERS
DAZ

[chimpboy]

i have now got 475 k`s out of a tank. thats 5.58 k`s/ltr, instead of 4.11. AN EXTRA 125 K`S TO A TANK.
WELL WORTH THE EFFORT.THIS SHOULD SAVE ME HEAPS ON FUEL TO FRASER AND BACK AT XMAS.
CHEERS
DAZ

Awesome... how did you measure this?

[HI 75]

475 DIVIDED BY 85

[of4x4]

475 DIVIDED BY 85

I think Chimpboy meant how did you measure the distance travelled - odometer, GPS, map, guess.....

Given the diff ratio change, there will be a impact to the Odometer (as previous mentioned). The method you used to measure the Kms needs to be given in order to give the mileage figures credibility. If you used the Odo without recalibrating it, my maths suggests that with an 18% reduction in gearing, 475Km measured actually is 390Km travelled (assuming your odo was accurate to begin with....)

Given that your Odo was probably inaccurate to begin with due to the 35's, the truth is probably somewhere in the middle of your original poor mileage and the new.

let's see. 3.9's with 35's: 12% more distance covered than measured due to larger diameter tyres. Therefore, 350kms measured actually is 392 kms travelled.

4.6;s with 35's: net 6% less distance covered than measured therefore 475Kms measured actually is 446Kms.

Somebody will need to check / correct my calculations. My head hurts now Going to lie down.....

[HI 75]

i did it off the speedo, i did the 5 km signpost test on the freeway & at 1 km i was 1.05 km`s.& so on.
very happy anyway,its now only 2 tanks to fraser, not 2.5 tanks,
cheers
daz