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2 cylinders or 4?

Started by Michael_Rolls, May 30, 2017, 08:34:42 am

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Michael_Rolls

Brother in law has just taken delivery of a Skoda Kodiak and one of the features of the car which intrigues me is that when cruising at a steady speed. a message comes up saying that 2 cylinder mode is in use. Apparently the car decides to 'shut down' 2 of its 4 cylinder, presumably for economy.
Can't understand it - to propel the vehicle at a steady speed requires a steady amount of power, which presumably requires a steady amount of fuel? Why should only using two cylinders be more economic? It means that each cylinder is working harder as one of a pair rather than one of four surely?
Mike  $%&
Properly trained, a man can be a dog's best friend

Gaspin

My car runs fine on three cylinders all the time !!





THAT"S ALL IT"S GOT !!

paulinfrance

Quote from: Gaspin on May 30, 2017, 09:29:55 am
My car runs fine on three cylinders all the time !

like my wife's  Gutless ! :o  Give me 4  :co or better still 8 ^-^





THAT"S ALL IT"S GOT !
Mode 2 THE only way to fly

Chippie

4 or 8 ?

The big Jeeps featuring the hemi - V8 engines do the same.....they shut down 4 cylinders when cruising to achieve better economy.....I'm sure other big Yank engines do the same ( GM ? ).....

Long term maybe it does prove detrimental to the engine but then that works in favour for the manufacturer.....in built obsolescence?
Eccentric millionaire Financed by 'er indoors'
Site Admin and forum moderator

keithl

Ford used to do a V6 that ran on 3 when it was not under strain - was marketed as a V3+3 - I think it went in some Sierras (and they didn't use it for long).
Warning: objects in the mirror may be close than they appear (or I'm creeping up on you from behind)

RobC

Maybe the increased fuel/air charge in the cylinders in use gives a more efficient burn?  Where's PDR when you need him?
flying's easy - it's getting it back down in one piece that's the hard part

Michael_Rolls

Looked up a few articles on the subject, and whilst there was a general claim that fuel economy was improved, none of them gave any like for like comparisons. I do wonder about it -- it does seem to be in the 'something for nothing' category, and I wonder how much improved economy may be the result of folk driving more gently to enjoy seeing the '2 cylinders mode' or whatever
Mike
Properly trained, a man can be a dog's best friend

Bad Raven

Nothing new, I had a 1927 Tilling Stevens Bus which ran on 2 of the four, but I soon fixed it.
The user formerly know as Bravedan........... Well if Prince can do it....................

paulinfrance

My V8 won't shut down, I think it has something to do with my right hand foot,,,  ^-^
Mode 2 THE only way to fly

fly-navy

Feel like I'm running on two cylinders these days, and it ain't good. :'(
Madam says it's nothing new. $%&
Coming up over the border tomorrow for 16 days Mike, West Coast, will I get mugged by that Krankie bird to vote SNP :uk:
Now that I am older I thought it was nice I seemed to have more patience,turns out  I don't give  a sh*t

ludwig

The Bentley W12 engine runs on 12 or 6 according to need.

keithupnorth

Quote from: paulinfrance on May 30, 2017, 17:40:39 pm
My V8 won't shut down, I think it has something to do with my right hand foot,,,  ^-^


To true anything less than 8 is a plank with silver cross wheels?


KW

FrankS

In a petrol engine both the fuel and air have to be regulated, at light loads this means restricting the air flow to the engine, so you get some pumping losses, if when only fueling two cylinders you can open the air throttle on the other two then you reduce the friction losses on those 2 cylinders, so the engine produces the same output power with less internal losses.

Michael_Rolls

Quote from: fly-navy on May 30, 2017, 17:47:33 pm
Feel like I'm running on two cylinders these days, and it ain't good. :'(
Madam says it's nothing new. $%&
Coming up over the border tomorrow for 16 days Mike, West Coast, will I get mugged by that Krankie bird to vote SNP :uk:

Watch out for herds of rampant haggis!
Mike
Properly trained, a man can be a dog's best friend