How many revs for best economy - GTI

[eeney]

Guys

This ma be a question for which there is no definitive answer but I´m interest to hear people´s advice.

When we bought our GTI we did so because a lot of our daily driving is motorway based, meaning we can get some reasonable day to day economy, with the turbo available for the sparodic blast. So please no responses such as ´should have bought a diesel´, or ´GTI isn´t designed for fuel economy´.

Now I assumed that between 100 - 120kmh that sixth gear would deliver the best economy, and usually we get around 7.5 ltr/100km, however yesterday on the same route we left the car in fifth and noticed that this figure had fallen to 6.5.

I know some new cars actually have indicators to tell you the most economical gear to be in (eg. mini cooper d), and so I´m interested to learn others experiences regarding the GTI and fuel economy depending on gear versus speed/revs.

Also I´d be interested how this changes after a remap, ie. does 5th become more economical to higher speeds, or does the extra low-down torque make 6th more economical at lower speeds.

Look forward to reading others' thoughts and experience.

[Tensixty6]

I've found that my best fuel economy reading is at a cruising speed of 90kph. On the open road this is not always achievable (slows down other traffic).

90kph (actual about 84/85) would be about 2200rpm. I've achieved 6.4L/100 on an early morning trip with no traffic to worry about. Mind you, 90kph in a GTI is pretty boring.

[blutopless2]

in my jetta tsi i can get it down to about 5.5L/100k's but at a about 65 kmh.
when i did a trip to queensland earlier this year i got around 7.5L cruising on 110 - 115kmh.

[Fanaki]

^ what gear is that in Blu?

[blutopless2]

6th... dsg.
in "D" mine short shifts at about 2000rpm to try and maintain fuel economy. so by 60k's its in 6th gear.
around town mine averages about 8L/100k's and out on freeway it can get down to about 7L/100k's.

as i mentioned above... ^^^ the trip to queensland was with 3 adults and toddler and a boot chockablock full of luggage... couldn't fit anymore into it.
so was quite impressed for just under 5000k's of travelling average fuel consumption was under 8L/100k's

[gregozedobe]

If you want to find out what works for steady speed cruising for your car, you could gather some empirical evidence rather than a whole lot of personal opinions

1 Find a long, flat road with minimal corners on a day with no wind,

2 Set your trip computer (MFD) memory (1) to display av fuel consumption,

3 Select the gear to be tested (ie 5th or 6th),

4 Set your cruise control to your desired speed (to take your right foot out of play as a variable),

5 Reset memory 1 to zero,

6 Drive for at least 1 km (or you could repeat the exercise on the same road several times in the same direction, but wind and other traffic can make your figures inaccurate),

7 Note the av fuel consumption,

Repeat 3 - 7 for your desired combination of gears and speed. This won't be totally accurate, but it should be good enough to show you which is the most economical speed and gear for your car.

Unless it was really hilly or you are going really slow (like less than 80Kmh) , 6th gear will probably the most economical, and the slower the better.

NB The average speed from the MFD will be much more accurate then the speedo reading (unless you have tweaked your speedo).

[BarneyBoy]

Conventional wisdom used to say that maximum efficiency for an engine occurs during its maximum torque range. This makes plenty of sense, as the engine is delivering the best compromise of pulling power at a rev range where the least amount of fuel is being used (revs are fuel-hungry).

On the GTI maximum torque begins at 1800 rpm and peaks at 5000 rpm.

This fits in with previous posters observations about shift points of 2000 rpm for best economy (in a DSG). If I had a manual, I'd guess that using 2-3000 rpm would deliver best economy. The only caveat her would be how hard you mash the throttle, however!

I know that with my TSI (DSG) in manual mode, 2-3000 rpm can deliver some pretty quick motoring around town. As far as the most economical speed range, mine gets its best at about 70-80 kph. 110 kph starts to factor in a fair bit of drag - it's more of a factor from 90 kph onwards.

[gerhard]

Instead of all the hassle of average fuel consumption with resetting, etc, why not just switch to immediate fuel consumption and flick between gears at cruise control maintained speed.

If 5th is more economical (which I doubt) you should get an immediate result in the consumption number.

[gregozedobe]

Instead of all the hassle of average fuel consumption with resetting, etc, why not just switch to immediate fuel consumption and flick between gears at cruise control maintained speed.

Unless the road is totally flat, straight (and level), and the wind stays exactly the same, there is no other traffic etc etc, the "instantaneous" consumption does vary quite a bit as you go up and down rises or falls that are so gentle you don't really notice them (but your ECU certainly does). Try it, you'll soon see what I'm talking about.

That's why I suggested the above method (with all its rigmarole).

[Maverick]

Conventional wisdom used to say that maximum efficiency for an engine occurs during its maximum torque range. This makes plenty of sense, as the engine is delivering the best compromise of pulling power at a rev range where the least amount of fuel is being used (revs are fuel-hungry).

But if you only need x amount of power and this can be achieved below that point doesn't it make sense to only produce the power you need? Let's assume it was 1400rpm in 6th to sit on 100???

Not that I worry about fuel efficency, I didn't buy the GTI to be frugal on fuel .... well actually that was a big part of how I justified the GT Sport TDI to the wife before I ended up getting a GTI instead.... oh well stuff it there's too much fun to be had driving it

[Fanaki]

I know that with my TSI (DSG) in manual mode, 2-3000 rpm can deliver some pretty quick motoring around town. As far as the most economical speed range, mine gets its best at about 70-80 kph. 110 kph starts to factor in a fair bit of drag - it's more of a factor from 90 kph onwards.

But is that with the slasher up or down?

^ Mav, have you been struck with the a boubt of dyslexia? you have your S's and D's mixed up

[Maverick]

^ Mav, have you been struck with the a boubt of dyslexia? you have your S's and D's mixed up

ooops

[eeney]

Hhhmmm, the idea of the point of maximum torque providing best economy makes sense.

Although I understand that the lower the revs at a given speed then the better the economy I am trying to better understand how this translates in to real world driving...... given my daily commute, 50kms of motorway with slight undulating inclines and declines in the road I was suprised to see the average fuel consumption fall in a lower gear, ie. at higher revs.

My thinking is that at say 100km, sixth gear would be the most economical on the flat or on a declilne, however could it be that at this speed the engine has to 'labour' at low revs in order to climb gently inclines and therefore is better in a lower gear, even though the revs are a little higher the engine can more easily climb the hill.

I guess it's trial and error to learn at what point the engine is 'labouring' and changing down is a better option. Afterall, I'm assuming that if the economy is lower then the engine is working less and therefore better for it?

Thanks guys.

[Transporter]

The best fuel economy is only possible to achive at the speeds up to 90-100km max. after that a lot of power is used to overcome air restriction.

[gareth_oau]

I've found through my own experience that the best way to drive is to keep your foot flat to the floor and only change up if the rev-limiter cuts in.

oh hang on, you're enquiring about econ..econo...eco..

sorry that word doesnt compute!!