gear changes for best mpg

[MarkWales]

lots of people have different claims to mpg and so on in their tdi 150s so just wondering how do you all drive

Gear ---> speed
1st --->
2nd --->
3rd --->
4th --->
5th --->
6th --->

 

[volvic]

i personally dont think that will help as it all depends on road conditions, tilt, wind, load, tyre pressure etc

i managed 63mpg ***** footing it on a flat section of the A13, between 50 and 60mph as i was worried i was going to run out of diesel (trip showed 0miles left). i had 2 passengers and a wheelchair in the boot!

 

[tolly_tdi]

Yes higher gear changes due to acceleration will affect MPG but more likely the average across the entire trip (that MPG is based on) depends on what rev range/area the engine is operating in most of that time.
For example on my TDI 110 if I were to keep it just over 1500 rpm in gear 5 which is about 50 MPH I would probably achieve 60+ MPG conversely though 70 MPH at 2500 RPM in same gear delivers about 52 MPG which I am still happy with!
From what I understand MPG values are pretty similar on a 150 at set speeds it will only consume more if you are accelerating frequently (like most cars!) due to bigger turbo and different map etc used in acceleration

 

[powernut]

ive a old mk4 golf 90tdi 160,000 and still doing 50mpg ,,, carnt say tdis arnt a bad engine ...think its time to sell ,,,

 

[S3 AKR]

Try driving by accelerating very gently and only using revs upto 2k so that the turbo doesn't really kick in. I used to travel 160 miles a day commuting in my PD150 and by doing that I got 62MPG. Also I got bored, didn't seem to get anywhere, was late, and spent more time than I needed to commuting!! The 46 to 48mpg at 90mph on motorways seemed a fair exchange.

 

[MarkWales]

yeah bored of the slower driving allready gone back to driving it quickly

 

[devonutopia]

1st ---> change to 2nd almost right away
2nd ---> find 3rd at 20mph
3rd ---> find 4th at 30mph
4th ---> find 5th at 40mph
5th ---> find 6th between 45 and 60 depending on incline, etc
6th ---> cruuuuuuiiiiise

basically just keep it below 2000 rpm where it's off boost.

 

[stuartsjg]

As i understand peak engine efficiency in a TDI is when you have peak torque.

Find where the peak torque starts and ends and keep the revs in this range. I think the truckers call it keeping it "in the green" - referring to the green band painted on the rpm gauge showing peak engine torque for effective trucking.

Even then, if you can, keep it at the lower end of the band as higher rev's need more fuel.

I normally change up around the 1800-1900 rpm point if im not in a rush.

If you need to push on a bit but still drive efficiently, change up at the point where you know the next gear engages at the lower end of the torque band.
If you dont, when you re-engage the clutch the engine rev's drop below peak torque and you will need to floor it for a sec untill the rpm picks up and your in the torque again. THis is effectively labouring the engine and wasting fuel.

Stuart

 

[Muttley]

Peak torque is around 1800 rpm for the TDI engine.

 

[enigma]

hmm mine makes peak torque at 2500rpm on a jabbasport map

 

[Muttley]

<Sigh>

Peak torque is around 1800 rpm for the TDI engine.

As delivered by VAG.

Remap it and it's no longer standard.

 

[devonutopia]

Thing is, yes they make peak torque at 2,000 or whatever, but they're also using quite a lot of fuel to generate that torque so I don't think it's the most economical way to drive a TDI car - lorry maybe yes. Keeping it off boost and using what grunt there is below 1500 (without needing to use much more than 1/3 throttle) uses the least fuel because the turbo is not being asked to kick in. When the turbo is asked to start generating boost, the fuelling goes up as well.

Don't forget also, that decelerating in gear (engine braking) uses NO fuel whatsoever so if you're tempted to coast to a point you know you need to stop - go down the gearbox, use less brakes, save fuel.

 

[Muttley]

Well, now.

The turbocharger can be considered as a device to take energy out of the exhaust gas (that would otherwise be wasted) and increase the compression ratio. Increasing the CR increases the engine efficiency, so overall, being on the turbo should help fuel economy. That's consistent with 1800 rpm, where the VNT turbo has just come on song.

I think the best steady-state fuel economy is probably got at 1800 rpm in top gear. The original post was about how to get there most economically. My guess would be to change up at about 2000 rpm - just over the torque peak, but will drop you down below it.

 

[devonutopia]

Well, all my findings have just come from general driving, keeping an eye on revs, instant mpg, and the boost gauge. All findings found that once the boost gauge started showing close to 0.3 - 0.5 bar, the instant mpg plumetted, whereas keeping it off-boost totally and just using the diesel engine's normal pull low down (ignoring the turbo), fuel economy was maximised.

I can't say I drive like this all the time, but when I want to just cruise along gently (sometimes my mind just says "f*** it! Let's pootle!") I know I can get the car to return back high 50s mpg (on the dash, around 55mpg true)

 

[Dyscontinued]

I find the same.

Trouble is I like in Yorkshire and it's bloody hilly here! Trashes the mpg tut.

 

[devonutopia]

I find the same.

Trouble is I like in Yorkshire and it's bloody hilly here! Trashes the mpg tut.

Let speed build up on downhills, allow it to tail off a bit on uphills. That only really works on flowing roads though - in town etc it's tough titty. The A35 from Honiton down to Dorchester is a good flowing A road to allow this - up and down dale on much of it, but gathering speed on downhills (sometimes a way above NSL) means you don't use much getting up tuther side as you allow speed to retreat back to normal levels.

 

[allh2k]

best way to save fuel DONT F IN DRIVE!!! nuff said

depends on car really

My 110 has to be at around 2400 rpm before I can change gear for it not to dip below 1800 rpm where the turbo isnt active.

lots of ppl argue over whether keeping it in boost is better than keeping it below boost, I beleive keeping it above boost so I drive in the boost area1800 - 2500 rpm takes some time to get used to put u get there. Its really annouying when im doing 2300 revs at around 50 behind some idiot who seems not to be able to do that extra 10 mph!! or just 2 so that I can change gear lol

only one way to find out really, drive really slowly coming out of boost for a tank full and then drive in boost for a tank full all cars are different and act differently to different driving styles and conditions.

 

[Swig]

What figures do you get allh2k?

I think I'm with devonutopia - only use the turbo much when accelerating and sit just below it otherwise - seems to get the best economy for me.

 

[MarkWales]

ive opened a can of worms in here

 

[allh2k]

when I think about it I was getting 50 mpg ish when i first got the car and that was driving below the turbo but now I struggle to make 50 mpg driving over so I should try driving below....

She is definatly not the same as when i bought here tho tyres and no splash tray smached fog light and turbo boosting all over.

Been driving the 1.0l micra this week tho now that gets 40+ mpg