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1.4 TSi ACT economy

Mr Pig

Active Member
Jun 17, 2015
1,539
439
I've just filled the tank after running a tank in Eco Mode and driving as economy friendly as I can. Most of my trips are very short, it's a second car, but it was the same type of journeys as before so a fair comparison of Eco Mode and sedate driving vs Sport Mode and using the revs a bit more.

Previous tanks average about 37-38 mpg.
This tank was 40 mpg.

I suspect most of that whole 2 mpg was due to driving style and Eco Mode does pretty much feck all. Sport Mode from now on then...
 
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Seriously?

Active Member
Apr 20, 2018
496
293
49.24MPG over the last tank for me. Measured, not indicated by the cars trip computer.
Sounds pretty good; I'm assuming that the on board computer is optimistic ( it's a VW group product after all.....o_O )
Anyone have any idea by how much ? 10-15%?
 

Glosphil

Active Member
Nov 10, 2004
89
20
Gloucestershire
Sounds pretty good; I'm assuming that the on board computer is optimistic ( it's a VW group product after all.....o_O )
Anyone have any idea by how much ? 10-15%?
My previous car, an Octavia vRS diesel was just under 5% optimistic when calculated over 40K miles. My Leon 1.4TSi (150) FR over 5K miles is currently less than 1% optimistic.
 

CupraGeezer

Active Member
May 11, 2018
262
108
Sounds pretty good; I'm assuming that the on board computer is optimistic ( it's a VW group product after all.....o_O )
Anyone have any idea by how much ? 10-15%?
Whenever I've checked my Cupra 280, it's come out at 5-6% optimistic.
 

Tass

Active Member
Mar 8, 2020
17
6
I've just filled the tank after running a tank in Eco Mode and driving as economy friendly as I can. Most of my trips are very short, it's a second car, but it was the same type of journeys as before so a fair comparison of Eco Mode and sedate driving vs Sport Mode and using the revs a bit more.

Previous tanks average about 37-38 mpg.
This tank was 40 mpg.

I suspect most of that whole 2 mpg was due to driving style and Eco Mode does pretty much feck all. Sport Mode from now on then...
So far I've discovered it's a difficult beast to drive economically. Because of the ACT setup it seems to use more fuel cruising in a higher gear with a light foot, than it does in a lower gear with moderate revs and ACT activating. Hence my economy figures don't seem to change much either when I'm being light-footed :/

I'm having to re-train myself not to change up and let the revs drop, but to always keep the revs around 1400-1700rpm (the lowest range that act will cut in)
I'll try doing a tank-to-tank comparison too and report back.
 
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KXL

KXL
Dec 15, 2016
1,399
146
London, UK
Dunno how accurate the on board consumption indicator is, but more than happy with this:
So you did 124 miles, and still had 'according ot the car' another 555 miles of range left in the tank? So a theorethical range of 650 miles from 50 litres.
 

Tass

Active Member
Mar 8, 2020
17
6
I'd love it if it were true! 17 hours between fill-ups would put me somewhere in southern France before I needed to stop.

The tiredness alert feature would be going bonkers tho :D
 

Seriously?

Active Member
Apr 20, 2018
496
293
So you did 124 miles, and still had 'according ot the car' another 555 miles of range left in the tank? So a theorethical range of 650 miles from 50 litres.
Apparently so - which was one of the reasons I questioned the accuracy of the on board consumption indications.
 

Mr Pig

Active Member
Jun 17, 2015
1,539
439
I'll try doing a tank-to-tank comparison too and report back.
I'd like to see that.

I'll be honest, I don't understand the ACT system. It's not like you're turning the engine into a three-cylinder one. It's still a four-cylinder when running on two so the rotating mass is still the same. I would have thought that moving the car a certain distance at a certain speed would require the same amount of fuel irrespective of how many cylinders that fuel is being burned in.
 

Tass

Active Member
Mar 8, 2020
17
6
I'd like to see that.

I'll be honest, I don't understand the ACT system. It's not like you're turning the engine into a three-cylinder one. It's still a four-cylinder when running on two so the rotating mass is still the same. I would have thought that moving the car a certain distance at a certain speed would require the same amount of fuel irrespective of how many cylinders that fuel is being burned in.
It's apparently due to the inefficiency of petrol engines when supplying low torque. As I understand it, two cylinders supplying moderate pushing power require less fuel to be injected overall, than four cylinders sharing the same amount of work.

This 'self study program' for dealers explains it nicely
 

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SuperV8

Active Member
May 30, 2019
13
9
I'll be honest, I don't understand the ACT system. It's not like you're turning the engine into a three-cylinder one. It's still a four-cylinder when running on two so the rotating mass is still the same.
Yes - the total friction of the engine is the same, but by running on 2 cylinders at low load requirements those two cylinders are having to run at higher torque and are running more efficiently, converting more of the fuel into motion - most piston engines are most efficient around their maximum torque - the problem being at cruising speed they are nowhere near their maximum torque. All engines are basically over sized for cruising speeds to give us good acceleration and high top speeds.

I would have thought that moving the car a certain distance at a certain speed would require the same amount of fuel irrespective of how many cylinders that fuel is being burned in.
Yes - a car moving at certain speed would require a certain amount of power, but the amount of fuel required to make the required power varies with the efficiency of the engine.

Tom.
 

KXL

KXL
Dec 15, 2016
1,399
146
London, UK
Probably why 4 engine passenger planes are disappearing for 2 engine ones. I digress...Saying that, fiat's 0.9l Twin-Air (eg..2 cylinder) motor isn't more economical than 1.0TSIs.
 

KXL

KXL
Dec 15, 2016
1,399
146
London, UK
I'd still rather have 4 engines, in case one stops there's more chance of staying aloft?
There's an airline joke, where a 4 engine plane lost an engine, and pilot assured everyone, it was ok, we would just be 1 hour late, then the 2nd went, and the pilot as calm as ever, said, no worries, just 2 hrs late, then the 3rd went, and captain said the same thing, then the passenger commented, 'man, if the 4th engine goes, we would be up here forever....
 
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GeoffGeoff

Active Member
Feb 1, 2020
184
36
Getting 38-40 on a mostly dual carriageway 11 mile trip in sports mode with mixed driving on a 130 1.5.

mused to get 44 on my previous diesel same journey and similar driving...happy with 6nog loss going from diesel to petrol.

On a longer journey I had 50mpg in the Leon and max I ever had in the diesel was 60 and that was very gene driving so I’m happy with the change to petrol and no worries about dpf’s and other expensive diesel bits to go wrong.
 
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