Anyone contemplated cylinder deactivation on cruise?
Discussion
Should be quite do-able on a wasted spark set-up with a decent ECU by switching out one coil pack, say for pots 2,3,4 an 7, and simultaneously killing the same injectors (probably a tad trickier but still only a matter of logic and clever wiring - could even be the fabled third map on emerald.
45 motorway mpg anyone?
45 motorway mpg anyone?
Cylinder deactivation isn't just a case of switching off the fuel to those cylinders. If you do that, the pistons are still pumping air in and out of the cylinder, which makes them a drag on the engine and you won't see much in the way of fuel saving.
Engines with proper cylinder deactivation also have valve gear that is designed to hold both the inlet and exhaust valves permanently closed on the deactivated cylinders. Sure, you lose energy when the piston compresses the trapped air on each up stroke, but you gain back a lot of that energy when the air gets a chance to push back on the down stroke. You lose some energy as heat of course, but if you didn't have the valves held closed then every other down stroke would be pulling fresh air in (against the resistance of the throttle butterfly), which would lose a lot more energy.
Engines with proper cylinder deactivation also have valve gear that is designed to hold both the inlet and exhaust valves permanently closed on the deactivated cylinders. Sure, you lose energy when the piston compresses the trapped air on each up stroke, but you gain back a lot of that energy when the air gets a chance to push back on the down stroke. You lose some energy as heat of course, but if you didn't have the valves held closed then every other down stroke would be pulling fresh air in (against the resistance of the throttle butterfly), which would lose a lot more energy.
t400ble said:
Would the cylinder not be damaged? I.e no lubrication?
No. Oil is still being pumped around the whole engine. The fact that some of the cylinders aren't developing any power doesn't alter that.Edited by Dr Mike Oxgreen on Saturday 7th November 07:24
Pupp said:
Should be quite do-able on a wasted spark set-up with a decent ECU by switching out one coil pack, say for pots 2,3,4 an 7, and simultaneously killing the same injectors (probably a tad trickier but still only a matter of logic and clever wiring - could even be the fabled third map on emerald.
45 motorway mpg anyone?
You would need to turn the fuel off as well or you will be pumping neat petrol down the exhaust, washing the bores of the non firing cylinders and diluting the oil with fuel leaking past the rings and not save a drop in petrol.45 motorway mpg anyone?
The whole engine would need to be redesigned to effectively make this work
Nice idea, sadly if we truly understand what cylinder deactivation is and how it works we soon realise its not nearly as simple as just turning the spark and fuel injectors off.
Remembering the infernal combustion engine is really just a pump, to properly implement cylinder deactivation and see fuel efficiency benefits you'll also need some form of dynamic valve control.
In a nutshell, cylinder deactivation is simply keeping the intake and exhaust valves closed through all cycles for a particular set of cylinders in the engine.
Do do this in our Rover V8 engine you would need cam followers that can be collapsed at will, Chevrolet do this using solenoids that are opened by the ECU to allow oil pressure in the follower to be wasted back into the sump.
This explains it well...
https://www.youtube.com/watch?v=9v2ld2u2lKQ
You'll also be well advised to move away from port injection to direct injection.
If Pupp really wants 45mpg from his turbo Chimaera he should first accept his specific objective is likely to be completely impossible.
However!
Rather than trying to achieve the impossible he should take a step back and understand what 45mpg really means, 45mpg is in effect costing you £0.11p to travel every mile!
If we now admit to ourselves the attractive and important element of 45mpg is not the figure of 45 but the fact it's only costing you £0.11p to travel every mile we can then move on to looking at other ways of achieving this cost per mile figure.
Basically there are two paths to the same goal:
1. Try to make your TVR consume 1 litre of 95 Ron petrol for every 10 miles you drive (45mpg)
2. Make your TVR consume a much cheaper type of fuel
Given we've already established option one would be impossible to achieve with the Rover V8 even if we could deploy cylinder deactivation (which we can't), if we really want to hit that magic £0.11p a mile figure we are forced to accept option 2 is our only chance of success.
If I lived in France the first thing I would do would be to put my TVR on E85, ethanol in France is just 0.60 cents a litre and converting your TVR to E85 is no more complicated than replacing the fuel line flexi hoses with Teflon lined ones, upping your fuel pressure by 10% and advancing the static ignition timing by 5 degrees.
You could do all the above for £100 and you'd be burning a race fuel for £0.43p per litre, yes like LPG you'll burn 15-20% more E85 than petrol but like LPG it's so cheap to buy you'll easily achieve £0.10p per mile in your TVR, the only disadvantage being your tank range will fall by at least 45-50 miles which may or may not prove frustrating...
Sadly bio ethanol is not available in the UK and it's looking unlikely it ever will be, so sticking with option 2 (Make your TVR consume a much cheaper type of fuel), that just leaves our old friend LPG. The nice thing about LPG is it's both cheap and available everywhere... England, France, Germany, Spain, Italy, Scotland and everywhere in between
LPG is also the highest octane fuel you can buy and at 110 Ron its octane rating is even higher than E85, in the US the Yanks are currently going crazy for gaseous fuels (propane & compressed natural gas) because fracking has left them with a massive glut of these new found fossil fuels. There's so much of it they literally can't consume it all fast enough, the UK government has been watching this closely and are currently investing heavily in our own fracking operations which are guaranteed in the next few years to leave us in exactly to same place as our North American cousins.
Gaseous fuels are therefore the future, they will bridge the gap over the next 20 years while we wait for alternative energies to catch up, even then all our electric cars will actually be gas powered because the electricity they run on will come from gas fired power stations.
So if Pupp really wants to achieve his 45mpg he needs to stop thinking about the figure of 45 and start accepting what he really wants is that magic £0.11p per mile!
Once that's sunk in he should either copy my proven super efficient high performance gaseous LPG system or explore the new breed of even more efficient liquid LPG systems from the likes of Vialle.
The best thing for Pupp about liquid LPG injection is you are introducing this extremely high octane 110 Ron detonation resistant fuel at -40 degrees Celsius!!!
Making it so perfect for forced induction it's not funny
However you choose to introduce it into the combustion chamber (as a gas or still in it's compressed liquid state) LPG is without doubt the only practical way to achieve your 45mpg Pupp
Forget the cylinder deactivation mate
Remembering the infernal combustion engine is really just a pump, to properly implement cylinder deactivation and see fuel efficiency benefits you'll also need some form of dynamic valve control.
In a nutshell, cylinder deactivation is simply keeping the intake and exhaust valves closed through all cycles for a particular set of cylinders in the engine.
Do do this in our Rover V8 engine you would need cam followers that can be collapsed at will, Chevrolet do this using solenoids that are opened by the ECU to allow oil pressure in the follower to be wasted back into the sump.
This explains it well...
https://www.youtube.com/watch?v=9v2ld2u2lKQ
You'll also be well advised to move away from port injection to direct injection.
If Pupp really wants 45mpg from his turbo Chimaera he should first accept his specific objective is likely to be completely impossible.
However!
Rather than trying to achieve the impossible he should take a step back and understand what 45mpg really means, 45mpg is in effect costing you £0.11p to travel every mile!
If we now admit to ourselves the attractive and important element of 45mpg is not the figure of 45 but the fact it's only costing you £0.11p to travel every mile we can then move on to looking at other ways of achieving this cost per mile figure.
Basically there are two paths to the same goal:
1. Try to make your TVR consume 1 litre of 95 Ron petrol for every 10 miles you drive (45mpg)
2. Make your TVR consume a much cheaper type of fuel
Given we've already established option one would be impossible to achieve with the Rover V8 even if we could deploy cylinder deactivation (which we can't), if we really want to hit that magic £0.11p a mile figure we are forced to accept option 2 is our only chance of success.
If I lived in France the first thing I would do would be to put my TVR on E85, ethanol in France is just 0.60 cents a litre and converting your TVR to E85 is no more complicated than replacing the fuel line flexi hoses with Teflon lined ones, upping your fuel pressure by 10% and advancing the static ignition timing by 5 degrees.
You could do all the above for £100 and you'd be burning a race fuel for £0.43p per litre, yes like LPG you'll burn 15-20% more E85 than petrol but like LPG it's so cheap to buy you'll easily achieve £0.10p per mile in your TVR, the only disadvantage being your tank range will fall by at least 45-50 miles which may or may not prove frustrating...
Sadly bio ethanol is not available in the UK and it's looking unlikely it ever will be, so sticking with option 2 (Make your TVR consume a much cheaper type of fuel), that just leaves our old friend LPG. The nice thing about LPG is it's both cheap and available everywhere... England, France, Germany, Spain, Italy, Scotland and everywhere in between
LPG is also the highest octane fuel you can buy and at 110 Ron its octane rating is even higher than E85, in the US the Yanks are currently going crazy for gaseous fuels (propane & compressed natural gas) because fracking has left them with a massive glut of these new found fossil fuels. There's so much of it they literally can't consume it all fast enough, the UK government has been watching this closely and are currently investing heavily in our own fracking operations which are guaranteed in the next few years to leave us in exactly to same place as our North American cousins.
Gaseous fuels are therefore the future, they will bridge the gap over the next 20 years while we wait for alternative energies to catch up, even then all our electric cars will actually be gas powered because the electricity they run on will come from gas fired power stations.
So if Pupp really wants to achieve his 45mpg he needs to stop thinking about the figure of 45 and start accepting what he really wants is that magic £0.11p per mile!
Once that's sunk in he should either copy my proven super efficient high performance gaseous LPG system or explore the new breed of even more efficient liquid LPG systems from the likes of Vialle.
The best thing for Pupp about liquid LPG injection is you are introducing this extremely high octane 110 Ron detonation resistant fuel at -40 degrees Celsius!!!
Making it so perfect for forced induction it's not funny
However you choose to introduce it into the combustion chamber (as a gas or still in it's compressed liquid state) LPG is without doubt the only practical way to achieve your 45mpg Pupp
Forget the cylinder deactivation mate
^^^^^
It's even perfect for FI,,,,
So Dave,,,, here's always been my glitch when it comes to Lpg,,even in a Jag,,,,
Can you dispell the fear of fire,,,
Gaseous fuel,,,, right behind your head,
Logic tells me, a hard hit in the rear could rupture a petrol tank easy enough,,,,causing fire,
The same applies to your Lpg tanks,,,,I assume or are they inherently stronger than the original petrol tank?
I think fire and the gaseous fuel worries people,,,,,maybe wrongly,,
It's even perfect for FI,,,,
So Dave,,,, here's always been my glitch when it comes to Lpg,,even in a Jag,,,,
Can you dispell the fear of fire,,,
Gaseous fuel,,,, right behind your head,
Logic tells me, a hard hit in the rear could rupture a petrol tank easy enough,,,,causing fire,
The same applies to your Lpg tanks,,,,I assume or are they inherently stronger than the original petrol tank?
I think fire and the gaseous fuel worries people,,,,,maybe wrongly,,
Hoofa said:
With out a blah blah post, I went from semi sequential to fully sequential and noticed not only a smoother running car but a improvement in fuel economy , I guess your thinking of economy ? food for though
Can you explain exactly what fully sequential is ? Do modern production cars run with this system ?K
Ok so semi sequential , is where two injectors fire together, one you do want and one that you don't , this is because the ecu is wired with four injection outputs so has to fire two together , same as wasted spark ignition
Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
SILICONEKID345HP said:
Hoofa said:
With out a blah blah post, I went from semi sequential to fully sequential and noticed not only a smoother running car but a improvement in fuel economy , I guess your thinking of economy ? food for though
Can you explain exactly what fully sequential is ? Do modern production cars run with this system ?Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
Hoofa said:
Ok so semi sequential , is where two injectors fire together, one you do want and one that you don't , this is because the ecu is wired with four injection outputs so has to fire two together , same as wasted spark ignition
Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
So what is the down side of two injectors firing together when one of them have no fuel is going in ..Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
SILICONEKID345HP said:
Hoofa said:
Ok so semi sequential , is where two injectors fire together, one you do want and one that you don't , this is because the ecu is wired with four injection outputs so has to fire two together , same as wasted spark ignition
Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
So what is the down side of two injectors firing together when one of them have no fuel is going in ..Fully sequential the ecu can fire each injector separately , in order to achieve this, the ecu must be capable of controlling eight injectors ( have eight separate outputs ) and you also need a cam sensor.
Hoofa said:
Because both are putting fuel in when they both fire, both injectors will fire fuel into the inlet , only one is needed,
So are you saying there is combustion at the wrong time of the stroke or is it un burnt ?Why even bother with semi sequential ? Why not have fully sequential as standard ? Its only a few more electronics a sensor and one or two extra wires .
Edited by SILICONEKID345HP on Sunday 8th November 16:43
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