Hmmm... A few have said the DSG box electronically limits the power to 250Nm hence, its name the DQ250, these can be reset should you find it neccessary.

"little throttle" ??? wouldn't work in my car then !

I see yours is due soon, enjoy her.

Regards

T

Edited 27 May, 201412 yr by themanwithnoaim

I guess not judging by your Fuelly sig - I've only got that low in my Fabia vRS when batting down the Autobahn in Germany!

I don't travel in traffic, on motorways or where many police cars roam so, I tend to be a little exuberant.

I don't travel in traffic, on motorways or where many police cars roam so, I tend to be a little exuberant.

The small roads in Scotland! Now they are fun

When do the cylinders shut down with this VW engine?

Is it at low power, and when at idle? Or just at idle?

 

I saw the video explanation of the valves/cylinders and it seemed that the middle two cylinders had all valves closed, fuel is cut off but still sparking.

Surely, two  "closed" cylinders will have some resistance and use power. 

 

Equally, I'm certain the valves could not stay open because of hitting the pistons.

 

All in all, I'm glad I'm not getting ACT - better it becomes established for a year or two before it is rolled out here.

 

retiredbri

see http://www.vwgenuineparts.co.uk/vw_act_active_cylinder_technology_explained.shtml for details

Let Audi and VW owners suffer all the breakdowns and engine failures while the shortcomings get sorted before handing the old tech over to Skoda. 

I'm not sure the principle of ACT is actually that new.

 GM did this in their V8's back in the mid 80's 9it was terrible by all accounts).

Mercedes did it in 2001 (Active Cylinder Control) in the S-class  - it was optional I believe, but I can't see it being a dog if it was on Merc's flagship.

Honda have been using it since 2003 - playing with their i-VTEC gubbins - VCM.

 

So, a technology that's at least had a degree of maturity for 10 years+, with advances in engine electronics.......

Unless VW get greedy and cut corners like made (2.0 TDI PD cams/oil pump fiasco, anyone?) then it really *should* be OK.

That's said, I'm struggling to see how the 1.4 TSI can realistically even claim 50mpg in an Octavia with DSG.....figures i could live with, that's' for sure though.

I saw the video explanation of the valves/cylinders and it seemed that the middle two cylinders had all valves closed, fuel is cut off but still sparking.

Surely, two "closed" cylinders will have some resistance and use power.

Equally, I'm certain the valves could not stay open because of hitting the pistons.

All in all, I'm glad I'm not getting ACT - better it becomes established for a year or two before it is rolled out here.

retiredbri

I only have experience of Caterpillar Diesel Engines, but the theory behind is probably similar. The valves still open and close as normal, but no fuel is injected into them cylinders. As you say, the valves cannotbe left open, nor left closed, without causing damage. When you take your foot off the throttle at speed, nearly all modern cars now stop injecting any fuel. (Note on diesel Octy3, with eco tips turned on, the message "Leave in gear when revs above 1300rpm", or words to that effect).

It will be the same theory, simply stop injecting fuel on two cylinders when they are not required. Fuel quantity is altered by the ECU anyway depending on RPM, Load and Temp, so it just sets fuel quantity to zero instead

On my Cat Industrial Diesel Engines, you can stop fueling any number of cylinders while the engine is running for fault finding purposes, I'd be suprised if car manufacturers we unable to do this too

Edited 28 May, 201412 yr by Rob123

That's said, I'm struggling to see how the 1.4 TSI can realistically even claim 50mpg in an Octavia with DSG.....figures i could live with, that's' for sure though.

Currently getting 45mpg average from mine with 50+ mpg from motorway journies at a steady 70mph. More than happy with this but I think it'd struggle to average 50mpg or more over mixed journies unless driven very very carefully.

...I saw the video explanation of the valves/cylinders and it seemed that the middle two cylinders had all valves closed, fuel is cut off but still sparking.

Surely, two "closed" cylinders will have some resistance and use power.

Equally, I'm certain the valves could not stay open because of hitting the pistons...

If you follow the link in post #31 and look at Fig 5, you can see the two cam profiles. On the compression stroke, the exhaust valves are open until just before the piston would hit them.

If you follow the link in post #31 and look at Fig 5, you can see the two cam profiles. On the compression stroke, the exhaust valves are open until just before the piston would hit them.

 

I looked carefully (and at the video) and to me, it seemed like just a cylindrical profile cam when not in use which equals no valve movement?

If you follow the link in post #31 and look at Fig 5, you can see the two cam profiles. On the compression stroke, the exhaust valves are open until just before the piston would hit them.

 

 

I looked carefully (and at the video) and to me, it seemed like just a cylindrical profile cam when not in use which equals no valve movement?

 

Yep both inlet and exhaust valves remain closed while the cylinders are shut down, just like in the video and pictures.

Yes the valves stay shut. The economy gain is because pumping losses are significantly reduced at low power outputs, when traditionally pumping losses are high and reduce engine efficiency. (Remember the throttle plate is almost closed at low loads)

 

Because they can only shutdown cylinders at reasonable engine speeds to avoid excessive vibration, the feature only works at light loads but medium engine revs. The economy gain will thereforeonly be seen by drivers with a certain driving profile, gentle driving but not slogging the engine.....

 

The big question is how reliable is the actuator/sliding cam mech is in practice i.e. when abused, neglect, old engine oil, wear etc etc - think DSG actuators but in a harsher environment

 

The technique itself is new .....its not the same as other manufacturers shutdown tech which was simply fuel cutoff based with some valve timing phase change in some cases.

Edited 28 May, 201412 yr by xman