Technical Twinair cylinder deactivation

[flashyphotos]

No it doesn't, when one cylinder is on its firing stroke, the other is just finishing exhausting and beginning the inlet stroke; there is one firing pulse per crank rotation, if it worked the way you suggested, there would only be a firing pulse per two crank rotations (as a single cylinder four stroke does).

The way I described was the way it was described to me, but like I say I probably have the wrong end of the stick,

I just had a look at the Video again of the TA Cutaway, and like you say from the Valve/Cam positions it seems to be on alternating cycles.

Still I am confused.

 

[bgunn]

The way I described was the way it was described to me, but like I say I probably have the wrong end of the stick,

I dearly hope this person doesn't work for FIAT. Unless they're a salesman of course..

I just had a look at the Video again of the TA Cutaway, and like you say from the Valve/Cam positions it seems to be on alternating cycles.

Still I am confused.

Think about it - it isn't in anyway different to any other multicylinder engine, the point is, you're trying to ideally create as many firing impulses during the rotation of the crankshaft.

 

[ahmett]

In hindsight I probably should have tried turning it off and restarting. It might not have been fuel level at all, just the restart that fixed it.

The fuel light comes on at 1/4 tank, I don't know exactly when my range display goes blank but 50km sounds right. Today it said I had a 700+ km range on the full tank, not the usual ~525 I'd been getting, we'll see

So just to confim, you've all driven to absolutely no LED bars with no drama?

Yes I have driven 10 km more with no bars on. After that I don't know what goes on = )

 

[chas379]

You might just have had a coincidental coil failure - has your car been recalled to have them replaced with BREMI coils? (if it was made prior to a certain date - which I can't find right now).

Either way, I wouldn't have driven the car like that - the chances of you frying the cat is quite high, as well as causing other collateral damage.

The TA that I had suffered from coil pack failure and reverted to 1 Cyl running and 'limp home', which was quite dangerous when trying to drive home. I ran low on fuel a couple of times but did not experience OP's situation. Only time was due to coil pack failure.

 

[jrkitching]

The TA that I had suffered from coil pack failure and reverted to 1 Cyl running and 'limp home', which was quite dangerous when trying to drive home.

Personally I would not attempt to drive home after a coil pack failure. IMO the risk of expensive collateral damage is just too great for it to be worth the risk.

 

[loveshandbags]

Personally I would not attempt to drive home after a coil pack failure. IMO the risk of expensive collateral damage is just too great for it to be worth the risk.

There's a trend now for some of the newer 8 cylinder engines to de-activate 4 of the cylinders to save on fuel and it may not be long before we see the same happening with 4 cylinder engines. Thinking about that African Panda it was probably a brave trip to go with 'just' a 2 cylinder engine.

 

[306maxi]

tbh with any engine if you lose one cylinder it's game over on a trip like that

 

[loveshandbags]

tbh with any engine if you lose one cylinder it's game over on a trip like that

On a 4 cylinder engine running on 3 cylinders I reckon you'd be able to top 55mph - for how long for I don't know. But a TA on 1 cylinder might be an interesting 'exercise' particularly if there's a Rhino in hot pursuit.

 

[bgunn]

There's a trend now for some of the newer 8 cylinder engines to de-activate 4 of the cylinders to save on fuel and it may not be long before we see the same happening with 4 cylinder engines. Thinking about that African Panda it was probably a brave trip to go with 'just' a 2 cylinder engine.

It's not the same four though, the Northstar (which was the first) deactivates four randomly (but distributed in a way so as not to unbalance the engine).

It likely won't happen on fours as they'll get far too lumpy, effectively turning the engine into a Twin Air without the contrarotating balance shaft. The only reason it 'works' on an eight is because there are so many firing impulses for it not to be noticed as the engine management switches over.

 

[ahmett]

It's not the same four though, the Northstar (which was the first) deactivates four randomly (but distributed in a way so as not to unbalance the engine).

It likely won't happen on fours as they'll get far too lumpy, effectively turning the engine into a Twin Air without the contrarotating balance shaft. The only reason it 'works' on an eight is because there are so many firing impulses for it not to be noticed as the engine management switches over.

bgunn don't the new gen VW bluemotion or whatever they are called engines have the 2 cylinder deactivation on their 4 cylinder petrol engines?

 

[Most Easterly Pandas]

bgunn don't the new gen VW bluemotion or whatever they are called engines have the 2 cylinder deactivation on their 4 cylinder petrol engines?

Not that I'm aware of.

 

[loveshandbags]

bgunn don't the new gen VW bluemotion or whatever they are called engines have the 2 cylinder deactivation on their 4 cylinder petrol engines?

Looks like you beat me to it Ahmett.
http://www.motorauthority.com/news/...irst-car-with-four-cylinder-deactivation-tech

 

[bgunn]

Being VAG tech, it'll be even more overblown in its claims than FIATs then, and be far more unreliable.

 

[ahmett]

Being VAG tech, it'll be even more overblown in its claims than FIATs then, and be far more unreliable.

haha WAG tech in the house. Their cars are so boring to drive I want to sleep driving them. The WV Golf TSI 160 may be quite fast but it is so uninspiring to drive, and those 225 width tires even more so, its just a shopping trolley with fat wheels.

 

[bgunn]

haha WAG tech in the house. Their cars are so boring to drive I want to sleep driving them. The WV Golf TSI 160 may be quite fast but it is so uninspiring to drive, and those 225 width tires even more so, its just a shopping trolley with fat wheels.

Worse than that, they make cars that might 'feel' as though they're hewn from solid, good quality, but the quality of the parts that matter (wiring, engines, gearboxes, clutch etc) are really poor.

 

[jrkitching]

The biggest difficulty with these ecocar designs is that they are all trying to find the 'holy grail' of 'performance when you want it, economy when you don't'.

In engineering terms it would be much easier to design a car with sound real-world eco credentials if folks were prepared to accept a permanent performance limitation.

A bit like with a combination washer-dryer, the design requirements of the two are sufficiently different that anything which can do both will always be a compromise.

The cost, complexity & reliability of these 'advanced' ecocars is also an issue - I don't see any economic justification for something which, over the lifetime of the car, will cost more to buy and maintain than the extra fuel it saves. IMO the 500 S/S system is a good example of such a system - what is the point of saving a few eggcupfuls of fuel if the price is (for folks who stay loyal to the dealers) a £250 battery replacement every 2-3 yrs?

 

[bgunn]

The biggest difficulty with these ecocar designs is that they are all trying to find the 'holy grail' of 'performance when you want it, economy when you don't'.

In engineering terms it would be much easier to design a car with sound real-world eco credentials if folks were prepared to accept a permanent performance limitation.

A bit like with a combination washer-dryer, the design requirements of the two are sufficiently different that anything which can do both will always be a compromise.

The cost, complexity & reliability of these 'advanced' ecocars is also an issue - I don't see any economic justification for something which, over the lifetime of the car, will cost more to buy and maintain than the extra fuel it saves. IMO the 500 S/S system is a good example of such a system - what is the point of saving a few eggcupfuls of fuel if the price is (for folks who stay loyal to the dealers) a £250 battery replacement every 2-3 yrs?

You're pretty much on the money. If car manufacturers spent the investment on developing lightweight materials, and mass production techniques for them, then the fuel consumption savings, handling improvements and safety would all be pretty huge. You really would get your cake and be able to eat it if your common or garden car was made from carbon fibre, the suspension components were all made from composites, or light alloys, and the car as a whole was optimised in this way.

Unfortunately, Eurocrats (and their equivalents all over the world) make misguided legislation that drives car manufacturers down a particular path that doesn't encourage the development of lightweight cars in this way. Passive safety is seen as a good thing, over and above any active safety measures.

 

[loveshandbags]

Would agree with you JR. There's a price to be paid for in over engineering. Thought this was an interesting post
http://forums.anandtech.com/showpost.php?p=29270424&postcount=9
And this is in the context of the OHs MiTo needing a new €700 ECU.
I once thought that if one was going to have S/S that you would need to go the whole hog and have re-generation but with the conflicts off keeping costs down to make a profit the customer ultimately ends up paying the price outside the warranty period. Having owned a VW Golf diesel from the 90s, recently borrowed a terrible Polo as a loan car & the in-laws having to rebuild the gearbox on a 6 year old low mileage Passat - I wouldn't trust VAG to get it right.

 

[bgunn]

the customer ultimately ends up paying the price outside the warranty period.

Usually, the uninitiated plough those funds right back into the dealership network. A classic example is the 15p saving FIAT (and others - this is not a FIAT problem by any stretch) make by not using some form of lubricant on the brake pad sliding surfaces. It's a win-win, as they save money and time in the factory, and the pads and discs will need replacement - usually at the time of the second service. And conveniently, they're never covered under warranty!

 

[Melanabb]

You're pretty much on the money. If car manufacturers spent the investment on developing lightweight materials, and mass production techniques for them, then the fuel consumption savings, handling improvements and safety would all be pretty huge. You really would get your cake and be able to eat it if your common or garden car was made from carbon fibre, the suspension components were all made from composites, or light alloys, and the car as a whole was optimised in this way.

Unfortunately, Eurocrats (and their equivalents all over the world) make misguided legislation that drives car manufacturers down a particular path that doesn't encourage the development of lightweight cars in this way. Passive safety is seen as a good thing, over and above any active safety measures.

Good point! Although I thought that Mazda made some inroads into this with their lighter Mazda 2? I think that the engine is still pretty rough but it is around 100kg lighter than the old one... I might be wrong though...