Fuel economy tips

[WiNgNuTz]

This is kinda aimed at Toms306 really, as the em pee gee guru, but thought everyone else could chip in their advice as well, to make this almost like a guide I guess. Mods feel free to move the thread if you feel it's in the wrong place.

Basically I am in Braintree at the moment for my mates radio show, but as he's a bit strapped for cash at the moment (as i think we all are), he's had to give me a bit less towards fuel. So I need to make what I've got last as best I can on the way home.

What sort of speed/rpm should I try and maintain for optimum mpg on a motorway? I was trying to keep it about 65mph/2500rpm on the way up, but had to speed up a bit towards the end of the journey due to traffic and a dwindling time limit. Made a point of sitting behind some trucks on the way up as well, whether it made ANY difference at all...

So yeah, feel free to pass on any fuel saving techniques you use, as Tesco say, every little helps!

Oh and if you like DnB music, tune in to my mates show on roughtempolive.com from now till 7. /shamelessplug

[Mattcheese31]

more like 55mph mate imo and try not to use your brakes . . .

[ally406]

The best MPG is achieved in the highest gear that the engine can comfortably pull, and certainly keeping the engine off boost will improve MPG (probably around 2,000rpm on the XUD).

Plan ahead as much as possible and try to avoid using your brakes. Braking = turning the energy the engine has created into useless heat. Come off the throttle early, move down the gears and arrive at your junction/roundabout/whatever at the correct speed and gear having not used the brakes.

Keep a good distance from the car in front so when they brake, you don't have to, just come off the throttle.

[WiNgNuTz]

more like 55mph mate imo and try not to use your brakes . . .

Ok, fair enough, will keep it down on the way home then, and i generally try and plan ahead enough to avoid using the brakes anyway.

[Dum-Dum]

I'd do 60mph behind a truck mate, You'll never really be close enough to slip stream (not safely at least) but it'll help you keep a steady speed better. 55mph is just a little slow IMHO. Try and keep a steady speed, dont spend too long accelerating as all the time you spend accelerating up to 60mph is time that you'll be doing less than optimum mpg. Look well ahead and anticipate having to slow down so you let off rather than brake.

Keep your windows shut
Check your tyre pressures (maybe even give them a psi extra)
Maybe even consider a bit of gaffa tape stream lining for what its worth


Oh and dont do the keeping it off boost thing suggested above, they need boost to be efficient.

[Kezzieboy]

Yeah, pick a lorry and sit behind it, as that's the slowest I feel safe driving on the motorway, personally, and as Dum says it'll force you to regulate your speed. Apart from that it's just all the obvious stuff, minimise acceleration and braking and where they are necessary make them as gentle as possible.

[WiNgNuTz]

Windows were open, but only a crack, kept them within the wind deflectors if that makes sense? Only cos it was so damn hot in the car! Lol. Not that it really made much difference.

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Tyre pressure I did day before yesterday, put them up to 37psi.

[Piggy]

lots of off gas braking.

use engine braking a lot....this just takes good observation.

3rd gear acceleration into 5th works well if aiming for a 50mph+ distance

[WiNgNuTz]

Regarding the shameless plug, who's logged into roughtempolive.com as BumpBumble? I see that comment, but can't use the chat room on my phone.

[silverzx]

Think all bases have been covered!

I did 170 miles each way (340 total) in one trip yesterday and managed 52MPG on the way up and 47MPG on the way back in the dogging wagon (Punto 1.2).

On way up between 55~70 but mostly 60~65. Then 75~80 on way back.

Obviously that was on my mates private runway,.

For the sake of the extra 5 miles per gallon I'd rather cut the journey time by 30-50 minutes.

[Piggy]

if stuck in traffic. consider leaving a good gap so the car is always moving rather than stop/start.
and if you do stop. dont assume stop/start for the engine is a good idea...
it takes about a minutes worth of fuel of the engine idling to start it again

[Toms306]

I've found the best way to spend less on fuel is just don't drive lol, nothing else works as well!

Pretty much what has been said though. Except keeping off boost, boost increases efficiency as Chris said. I tend to stick at 55mph (until I get fed up/panicky and creep to 90+ forgetting about mpg lol). I find 60 is annoying as you have to keep overtaking lorries - slowing behind them, then accelerating which is just throwing fuel away.

[samass]

take the boost feed off to the pump and block it up, that'll save you some fuel too, that's what I so most of the time (just a shame the roads are here are far too awesome to not have boost...

[Face.]

be very gentle with the throttle pedal use a 1/3 at most.

[Seb_Ryan]

I find with the vec on a flat road at 50 the on board is showing more mpg in 4th than 5th, so just about on boost is the best id say.. not full on boost but enough,

Uphill acceleration will kill it aswell, so try and build up speed on the flat before and coast up.

Coasting is good aswell if and when you can as it doesnt use any fuel tbh

[Dave]

When your slowing down, don't be tempted to clutch it, leave it in gear and the pump will cut the fuel off if you have not touching the throttle, as it'll always use a small amount keeping it idling if you do freewheel.

[Bender]

Easy less revs less fuel use, less gear changes less fuel use, less braking less fuel use. I go from 1st, 3rd, 5th and stay in 5th at 30mph. Or start at 2nd go up to 30 mph and just stay in 5th.

Tyre pressure at the correct amount also makes a big difference. Make the car as light as possible like an empty boot and a C5 spare wheel lol.

60 MPH will rinse the fuel, stay at 55 or less and you will save loads, all dependant on revs at those speeds, anything below 2.5 or 3rpm is fine.

A good start is having a diesel.

[Dave]

I found my economy was very good with rock hard tyres too, obviously this certainly isn't recommended but I defo noticed an improvement.

[Toby]

I find the XUD lump to be pretty efficient at speeds up to 80 mph..

I do 150 miles every day in my ph1, so have quite a lot of evidence to draw this conclusion from..

Brimming the tank with veg will always yield 600 miles, and I've had up to 650 before.. This equates to 45 - 48 mpg.. And that's averaging 75 mph +.

Also bear in mind that veg oil itself has around a 5% lower calorific value than pump diesel.

I agree with Dave, I run my tires at 45 psi all round and I do believe this makes a difference.

Maybe one week I'll limit myself to tailgating lorries and see if I can improve on my tank range..



Edit: Another weird tip; when doing long distance, not wearing a shoe on your right foot helps with using exactly the right amount of throttle

[Ruan]

Whoa whoa, the whole "keep the engine off boost" is total trash - in a petrol, yes, you've got an AFR to keep to - to stop the pistons melting..

Diesel the more air you can cram in the engine (to a point... Pumping losses...) the higher your thermal efficiency - Turbocharged Diesels use a slightly lower compression ratio, so any increase in thermal efficiency will help... That's precisely why Diesels are significantly more efficient, they've got greater thermal efficiency than a Petrol engine... 21:1 compression vs 9:1 Compression (if you're lucky)...

For example, with a OE T2 I was achieving around 45mpg on the motorway, when I fitted my VNT, that'd be producing between 8 and 10psi constantly on the motorway, my economy rocketed to ~60mpg...

Think about it in terms of power being a function of torque or RPMs... Think of your foot as a "Torque Request" pedal - that's how the governor in the pump works, the harder you press, the more torque you get - but at the same time, if you don't press hard and let the engine rev higher, you get automatically more power, since you've got the same amount of torque, it's often MORE efficient to allow the engine to rev slightly higher rather than injecting loads of fuel to create torque to tug you along...

[Dum-Dum]

Another weird tip; when doing long distance, not wearing a shoe on your right foot helps with using exactly the right amount of throttle

Make sure you hoover out your footwell's first as glass and small stones in your heel aren't fun. I drive barefoot sometimes either cos I've gone out in flip flops or when Id injured my ankle.

[Dave]

I know I'm being anal here but remember efficiency can be measured in a number of ways, this all boils down to how well they burn the fuel, being at 10psi would be much more 'efficient' than burning fuel at 2psi you'll just burn a lot more fuel but have a higher efficiency of power.

[Ruan]

A high compression ratio is desirable because it allows an engine to extract more mechanical energy from a given mass of air-fuel mixture due to its higher thermal efficiency. This occurs because internal combustion engines are heat engines, and higher efficiency is created because higher compression ratios permit the same combustion temperature to be reached with less fuel, while giving a longer expansion cycle, creating more mechanical power output and lowering the exhaust temperature. It may be more helpful to think of it as an "expansion ratio", since more expansion reduces the temperature of the exhaust gases, and therefore the energy wasted to the atmosphere.

That's what I mean when I say more boost is a better thing That wasn't necessarily to say that making more boost on the same turbo is a good thing, since yes, you'd need to consume more fuel to make enough exhaust gas to make the boost pressure go up...

[Piggy]

I noticed this last night...despite being without a aux belt...

was properly shifting in the 2.1 on motorway, around 10psi, but looking at fuel gauge, I have done about 60miles making suitable 'progress' and used about a gallon of fuel, if that.

PS ruan....check ya latest PM from me pal...something of interest to you I think

[306Puggy]

Haven't read the rest of the replies, but this is an easy subject. I have achieved 10 miles per litre using the following:

Stay below 2.5k rpm

Be smooth with the controls

Keep all windows up

And the rest sees to itself. I have to try hard to get below 45 mpg when kaning it. It really is hard to get low mpg on these engines.

[silverzx]

They sound so much better at 4.5k+ with big blowers though...

For the sake of the extra £10 a tank or whatever it is I'd rather be having fun!

[Toms306]

Puggy, 10 miles per litre IS 45mpg...

[Piggy]

guna say... 10miles per litre and you're TRYING to drive eco!!??

I could get 45average in the xud with 11mm pump...not trying to be eco and on 100% veg!

[Dum-Dum]

They sound so much better at 4.5k+ with big blowers though...

For the sake of the extra £10 a tank or whatever it is I'd rather be having fun!

Its a bit more than that. A 2.1 will do 60mpg, I know, I've done it so if I could keep my foot off the floor for a whole 14 gallon tank Id be looking at 840 miles whereas on a blast it goes down to 35mpg average (probably less for short periods) and thats 490 miles.

[zx_volcane]

I've got an app on my phone that I log all my tank fill ups and milage, so have over a years worth of data now

I've averaged about 38mpg

Can be in the low 20s if I try

Might have managed 51mpg once on a frugal run, but no higher -and I do a fair amount of motorway miles

I used to run bio - pretty sure there was zero difference with mpg