driving style

[mgermasi]

Hi guys,
What is the best driving style for a very heavy Navara (2.8T) AUTO?
)- Taking off slowly (no more than 2700RPM) until you reach cruising speed
)- Taking off to reach cruising speed quick (let's say 3000RPM to 3500RPM) then back off

Thanks
Max

 

[KraftyPg]

My guess is you will find no definite data to prove either option because there is too many variable factors in each method. It all comes down to personal preference, where you was edumacated and which one of your balls hangs lower.

Of course it also doesn't matter a great deal because each method is only a small part of driving, how a driver operates the vehicle for the rest of the trip will have just as much bearing on the economy as they do taking off.

 

[jimmy_jay89]

well said

but with that amount of weight... taking it slower will reduce wear and tear

 

[mgermasi]

It seems it takes so long to get to next gear up and drop the RPMs down.

 

[jimmy_jay89]

thats because its an auto

 

[BravoBrad]

just drive to the conditions. Its rated to a GCM of around 5800kg

 

[mgermasi]

Also does a heavier car require higher tyre pressure?

 

[nakedape]

Yes, probably, maybe. It'll depend on what krafty said above - ie conditions, tyres (P or LT rating) etc. But generally you'll need more psi with more weight.

 

[mgermasi]

Thanks nakedape,
are we talking 4-5 PSI or more? What would tell me the right pressure other then the 4 psi rule? Sidewalls?
Thanks

 

[nathand22]

I think it depends on what tyres you are running and the quality of tyre, eg if you run a good quality A/T like BFG's and have nothing or very little in the ute i run 36psi front and 34psi rear, BUT if im loaded to the max i will run 38psi front and the same in the rear or fractionally more (maybe 40psi rear) if i add the trailer as well.

If you have a standard H/T tyre and the construction is poor then i would run 40psi with the ute empty

 

[KraftyPg]

But again tyre construction, tyre pressure and tyre tread while all contributing to economy and wear and tear are not the be all and end all and for most drivers there will be minimal change in economy or wear and tear with a few PSI or a different but like make of tyre.

Mythbusters 'proved' that running your tyres 10% higher than manufacturer recommended will make economy better, but they were under controlled conditions. Put a driver in the seat, add traffic, add wind and weather and any gain from over inflated tyres could easily be negated because of any number of reasons not to mention the possibly premature wear of the over inflated tyre.

Changing pressure depending on load can be a good idea but it will always be more beneficial for the occupants who get a better ride than it will for economy or wear and tear.

 

[nakedape]

Agreed - but with high loads under-inflated tyres generate excess heat & may go bang. Over inflate and the tyre may also go bang. There is a goldilocks pressure for every load in every condition - if you can be arsed working it out, if not approximate like the rest of the world does.

 

[KraftyPg]

This is true, don't run them flat because some nufti says you'll get a soft ride and don't run them like balloons because you are a fat bastard and push the load limits. Just drive the car and if economy and wear are a concern or something you want to fix, learn how to drive better, it's simple really.

 

[Old.Tony]

Economy is a bastard of a thing especially when you try to talk about the differences in acceleration methods. Should you hold the RPM at <2500 for 22 seconds (max fuel flow rate around 15LPH) or plant the foot and get up to speed in 16 seconds (max fuel flow rate 37LPH)?

Let's do that math. 22 seconds of 15LPH is 0.091 litres of fuel. 16 seconds of 37LPH 0.164 litres of fuel.

Where do the figures come from? The times are a guess, but my Torque application has a "Fuel Flow Rate" meter and out of curiosity I was watching it the other day as I accelerated, cruised etc. I saw a peak around 37 litres per hour and under mild acceleration she sat around 15LPH. I could get it moving with 10LPH but at the expense of some irritated people behind me whom I could have opened my window and yelled "will you die if it takes you 10 seconds longer???" but since it was an ambulance with its lights flashing I thought I'd shut my mouth.

So in a nutshell the acceleration rate DOES make a difference. I might see if I can graph RPM vs flow rate one day.

 

[nakedape]

Nothing to do today Tony?

Interesting data though!

 

[Pete22]

Like others have pointed out tyre pressure is just one of the many inputs to getting the best fuel economy out of your vehicle.....but it is an important one nonetheless. The "4psi Rule" is one that works for me but rather than me trying to explain it you could go to either of these links for a more fully articulated explanation:

http://www.aawen4x4.com.au/index.ph...ticle&id=1:4psi-rule&catid=2:current&Itemid=7

http://www.nissanpatrol.com.au/forums/showthread.php?330-The-4-psi-Rule

http://www.4wdaction.com.au/forum/viewtopic.php?t=77750&f=7

http://downunder4x4.net/forum/showthread.php?t=8197

http://www.bridgestone.com.au/tyres/passenger/care/pressure.aspx

Some folks also use the "6psi rule":

http://www2.pajeroclub.com.au/forum/showthread.php?p=255738

 

[Old.Tony]

I was thinking about this topic just the other day, and added the meter to my Torque application so I could watch it.

I've now added a graph configuration so that the next time I take the car out, it will graph rpm vs fuel flow rate. I'd like to get a chart of rpm vs time vs speed vs fuel flow - will have to see what data I can actually log and put together.

 

[nakedape]

Can you collect and feed all those variables into excel, then build a graph from there?

 

[Old.Tony]

I don't know about getting the data for Excel, but I did manage to get a scatter graph of RPM vs Fuel flow rate. It's very interesting! You'll notice that as the RPM rises, the fuel flow rate rises exponentially.

It means that higher RPM is a true killer for economy. Here's the chart, I've cropped it so that it's not too big for the forum.

 

[KraftyPg]

HUH? Of course higher RPM has to use more fuel there is no way around that and you shouldn't need a graph to tell you that, but the question was is using more for a short time to get up to speed more economical than using less and taking longer. The graph may be pretty but was never going to prove or disprove the question.