Holden sacrifices V8 power for economy

[Johnsy]

Its not just cutting the fuel consumption. 2 racers at a set of lights. Lights go green and off they go. Then the deactivation cuts in 4 cyls go down and the driver loses and gets larfed at. This is a serious issue ppl's that cant be let happen.

not condoning street racing, but if both drivers put there foot to the floor the deactivation wouldn't kick in under full throttle it's the complete opposite to how it works...

 

[Cursed CX8]

On the V6??? Don't think so. I understand they are currently testing direct injection which will save in the order of 10% fuel (with a power gain) for the V6 motors.

Reaper

no not the v6. I was just wondering if holden would have an option for deactivation, same as some other companies. The Direct injection if about 10 years too late...

 

[Immortality]

i really can't see how reducing 10kw from peak power is going to save you fuel. when driving around day to day and even considering about trying for economy your never even going to get anywhere near to any of the fuel map where you have lost the extra power so this is a pure marketing exersize. the whole point of being able to dis-able 4 cylinders is to save fuel when cruising so there is no point de-tuning the engine also

 

[greenfoam]

Yeah there's something weird going on with the power level drop for whatever reason I sure it's seperate to the deactivation. But I'm qondering is it the same 4 cyl that deactivates all the time? because your going to end up with 4 clyinders that last 500,000ks and 4 that last 700,000 , if it's random which set of 4 it uses you would get 600,000 from the whole motor for example, that would be better

 

[Reaper]

Yeah there's something weird going on with the power level drop for whatever reason I sure it's seperate to the deactivation. But I'm qondering is it the same 4 cyl that deactivates all the time? because your going to end up with 4 clyinders that last 500,000ks and 4 that last 700,000 , if it's random which set of 4 it uses you would get 600,000 from the whole motor for example, that would be better

My understanding is that they vary the pattern. Not random but the cycle has been chosen to make the engine stay as smooth as possible. It is not a simple matter of every 2nd cyl firing.

Reaper

 

[davey g-force]

Yeah there's something weird going on with the power level drop for whatever reason I sure it's seperate to the deactivation. But I'm qondering is it the same 4 cyl that deactivates all the time? because your going to end up with 4 clyinders that last 500,000ks and 4 that last 700,000 , if it's random which set of 4 it uses you would get 600,000 from the whole motor for example, that would be better

All other AFM / DOD engines from other manufacturers rotate which cylinders they deactivate, so I'm pretty sure the Holden one will be the same.

 

[greenfoam]

My understanding is that they vary the pattern. Not random but the cycle has been chosen to make the engine stay as smooth as possible. It is not a simple matter of every 2nd cyl firing.

Reaper

I thought there would be 2 sets of 4, (two V4s) but maybe it's more complex than that

 

[Reaper]

Did a bit of hunting around and found a very interesting article here: Cylinder deactivation – Displacement on demand – Variable engine displacement

For pushrod designs—when cylinder deactivation is called for—the hydraulic valve lifters are collapsed by using solenoids to alter the oil pressure delivered to the lifters. In their collapsed state, the lifters are unable to elevate their companion pushrods under the valve rocker arms, resulting in valves that cannot be actuated and remain closed.

By forcing the engine valves to remain closed, an effective “spring” of air is created inside the deactivated cylinders. Trapped exhaust gasses (from previous cycles before the cylinders were deactivated) are compressed as the pistons travel on their upstroke and then decompressed and push back on the pistons as they return on their down stroke. Because the deactivated cylinders are out of phase, (some pistons traveling up while others are traveling down), the overall effect is equalized. The pistons are actually just going along for the ride.

To complete the process, fuel delivery for each deactivated cylinder is cut-off by electronically disabling the appropriate fuel injection nozzles. The transition between normal operation and deactivation is smoothed by subtle changes in ignition and camshaft timing as well as throttle position all managed by sophisticated electronic control systems. In a well-designed and executed system, the switching back-and-forth between both modes is seamless—you really don’t feel any difference and have to consult the dash gauges to know that it's happened.

 

[savage1987]

Yeah there's something weird going on with the power level drop for whatever reason I sure it's seperate to the deactivation. But I'm qondering is it the same 4 cyl that deactivates all the time? because your going to end up with 4 clyinders that last 500,000ks and 4 that last 700,000 , if it's random which set of 4 it uses you would get 600,000 from the whole motor for example, that would be better

That was my worry as well

 

[greenfoam]

Reaper, that's very fancy