Fuel economy - how can I improve it?

Discuss technical aspects of your 4WD with other owners, and share your opinions
Navman92
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Joined: June 21st, 2018, 1:10 pm

Fuel economy - how can I improve it?

Unread post by Navman92 » June 22nd, 2018, 6:51 pm

Hey guys I'm looking for some advice on how to get better fuel economy out of my 2007 navara d40 petrol currently getting 450 to the tank with a 2inch lift and 33 inch tyres any help would be much appreciated

cbd
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Re: Fuel economy - how can I improve it?

Unread post by cbd » June 25th, 2018, 7:24 pm

G'day
You probably know already that 2 in lift and those 33s are a contributing factor to your fuel consumption. You have them for a reason so.... work with them.
Those 33 in black donuts even with no load on the made roads run them at at least 40psi. Yes and check them every fuel fill not just every now and then!
The lift that puts you higher into the brick zone above the road surface. Makes your machine a lot less aerodynamic. Lose the spotties and bar above the bonnet! Lose the basket on the roof rack for the 2 new spares ( I did). ( yes and the black angled deflector only makes it not whistle, but does not make it any more aerodynamic).
For day to day running lose all the bits that make you overweight. The pump, the recovery gear, the shovel etc. I even drop the spare and top it up.
Even check behind the back seat for any ***** you never use ie I have a jumper cable that I have never used except to help someone else out that had RACQ anyway!
And drive like you own the road; stick to 100km per hour. Lose speed on a hill so what..... catch it up on the other side. The MX3 owners do not want you around them, I reckon they have a thing about the 33s above their bonnets.
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Navman92
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Re: Fuel economy - how can I improve it?

Unread post by Navman92 » June 29th, 2018, 7:59 pm

I know this might sound dumb but what about and exhaust and snorkel the more air getting into the motor and exiting do anything

hoyks
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Re: Fuel economy - how can I improve it?

Unread post by hoyks » June 30th, 2018, 2:11 pm

I think it will do 4/5ths of stuff all. I put a snorkel on and it made no measurable difference to the fuel usage. The much vaunted ram air effect won't do anything much to increase manifold pressure when you have the engine sucking the air out of the other end.


It mainly comes down to mass and drag. It takes energy (fuel) to get stuff moving, the more stuff the more energy is required. To double your speed you need 4 x the amount of energy.
Providing the torque to turn the larger tyres takes more energy.

So, to save fuel, take it back to factory settings;
put the car on a diet
go to 30" tyres
take off bits that create drag (lights, bullbar, roof racks etc.)
don't drive as fast
buy an i30 and drive that instead.


You don't get anything for free, its against the laws of physics.

Peter Aawen
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Re: Fuel economy - how can I improve it?

Unread post by Peter Aawen » June 30th, 2018, 5:21 pm

Navman92 wrote:
June 29th, 2018, 7:59 pm
I know this might sound dumb but what about and exhaust and snorkel the more air getting into the motor and exiting do anything
Back in the early 70's when engine & air flow design was pretty rudimentary, exhaust & intake mods could & did make a difference, but since about 1974 in Aust, when the new emission control laws made things a lot stricter & manufacturers/designers had to work a whole lot harder to provide us with vehicles that'd achieve better fuel economy & meet stricter emission rules, they've been putting millions of $$ into the research & development that tends to get them pretty damn close to 'right' up front & consequently, it's become a whole lot harder for the backyard modder to make any serious gains thru simple & cheap exhaust & air intake mods! So Hoyks is right, just about anything you can readily & cheaply do to either end of the air flow circuit is only going to get you 4/5ths of 5/8ths of sweet FA!! Besides, that Ram air effect only ever worked if the air was rammed in faster than the vehicle was moving and engine was using it, and today, an engine much bigger in capacity than about a litre is going to pretty use just about everything & anything you can stuff into it hru a 4" pipe without 'artificial' or high powered help anyway, regardless of how fast you might be going or how hard you are ramming (unaided!) :gurn:

All that said, the more 'agricultural' or 'dated' your vehicle's engine design is, the more likely you are to get some (minor) improvements by updating/improving the air intake &/or exhaust, but the D40's really don't warrant the label 'agricultural' anywhere but maybe in/around the rear brakes!! So if you want improvements, you'll need to start thinking along the lines of Lower, lighter, gearing, slicks, ECU upgrades, etc; you know, all those things that risk reliability, longevity, & off road capability.... :o In fact, it basically comes down to one thing - you really need to choose between having a capable 4WD or having an on-road vehicle with great fuel economy!! It's awfully hard to get that in one package - something is going to be a compromise, & it's often fuel economy! If you really need both, that is, an economical car during the week & a capable 4WD for the weekend & holidays etc, then maybe you should consider buying a 2nd car; a Nissan Micra or Suzuki Alto or similar might fill the bill for your weekday use, & you can still keep the Nav for the weekend! ;)
An Ex-Service person is someone who thought enough about their country & how great it is, how lucky we are to live here, to write a blank cheque made out to 'The People and Commonwealth of Australia' for the value of 'Up to & including my Life!'

MYCol14
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Re: Fuel economy - how can I improve it?

Unread post by MYCol14 » July 3rd, 2018, 9:13 am

Navman92 wrote:
June 22nd, 2018, 6:51 pm
Hey guys I'm looking for some advice on how to get better fuel economy out of my 2007 navara d40 petrol currently getting 450 to the tank with a 2inch lift and 33 inch tyres any help would be much appreciated
I'm assuming your diff ratios remain standard?
As has been suggested I'd be getting rid of the 33's and going to 30's.
A solution for you may be to look at buying a set of rims and standard tyres for everyday use (I'd guess your acceleration/performance will be much better and fuel economy could be up by 15-20%).
Use the 33 inch tyres for when you think you really need the vehicle clearance off-roading or for special occasions.

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