Under revving with CWP

[mrapocalypse]

So what happens if you stick 4.11's on but only put 265/75/16 (32") tyres on, then you are running a few percent UNDER standard gearing and over revving slightly, are you gunna use more fuel or get more benefit out of having some more torque to turn your muddies.

I imagine you are going to suffer most on the highway but maybe not... We are only talking a drop in revs of 4% here, the difference between (I think) 32" and 33" tyres....33" are the optimum tyre size for 4.11 CWP on a D2.

What's the relationship between engine working harder at lower RPM against standard gearing and taller tyres to maintain headway as oposed to sitting at slightly higher RPM... I am thinking that throttle position is pretty important in this issue particularly concerning an Auto!

Auto opinions of most interest.....

[PhilipA]

Having just driven 2000Kliks with a blocked fuel pump inlet, maybe I am qualified to comment.LOL. 3.9 RRC auto.
If I added any throttle at all the thing would backfire and die so I had to just keep a pussy foot on it.
If I changed to 3 the engine would die, so my theory is that the lower the revs the lower the fuel usage at a given speed.
Also it was surprising to me how much difference the TC lockup made. If I could get it to 85KMh, it would then gain about 10Kmh as the converter locked.
So you will use more fuel with a lower diff all things being equal, but then you use more with muddies, so don't worry about it.
it also depends on the terrain, the load, etc etc etc.
Regards Philip A

[Tombie]

My D2 is currently on 4.11s and 265-75-16s..

Revs around 2750 on 110km/h....

The vehicles been rolling on these tyres 95,000km and had the gearing done 4 months ago.

Now done 105,000km and can say about 1L/100km more fuel usage...

If you have more specific questions gimme' a call :cool: 0423 126 538 (or PM)

[mrapocalypse]

Thanks guys... Good answers.

I am going up to 265/75/16 to give them a go and was just wondering if there was an option of the lower ratios and I would think there was.

Appreciate the help

Cheers

Ian

[Pedro_The_Swift]

From nearly sold to Monster D2!!
its been interesting watching your build-up Ian:cool:

[mrapocalypse]

Thanks Pedro. I remember that. Trouble with a truck like mine is that what on earth would you replace it with. I was struggling with the repayments then. In the wash up though it was worth much more to keep it. This LR also took some time to warm to us - for it to become "Our car" because we were working too hard to use it and get any benefit from it. All that's changed now after a move to Qld.... and I did a spread sheet the other day and have spent an honest $18000 over 4 years on getting it right. Almost the value of the car over again. But now even my previously 4x4 hating wife occasionally places an affectionate hand on the bonnet with all the memories of great stuff we've experienced and places we've been in it.

Ian.