i know this is a really dumb Q
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Yes, car companies work on things like that where at cruising speeds some cylinders shut down as they are not needed for power. I imagine it is quite complex and is not a simple procedure. I doubt you can pull that off in any old motor, those cylinders would be flooded with unburned fuel and I doubt would just fire up normally with all that extra fuel, but yes, I think there are cars like that now other than the "valet" thing. Hybrid cars are same idea but different. (?) Thats my .02 So no, I don't think you can just change it. It will run on less cyl but not good obviously.
the firing order is the order in which the spark plugs fire, then I believe the PIP sensor sends the signal through the ignition module to the computer, telling it the base timing and all that and then the computer sends fuel based on that. If you had two computers or possibly a chip specifically to run on only 4 cyclinders, you could probably do it. You'd have to make it stop sending fuel and also somehow get it to stop sending spark...basically it would be cheaper to prob. just buy a beater if you're concerned about gas mileage and save the stang for nice weather and races lol. By the way, I've never heard of that vette w/ vallet mode...i'll have to look that up...sounds interesting and it's a good idea, but i'd prob. still have all 8 cyc. goin most of the time.
it is possible, but not really practical and nearly impossible to do on a stang.
newer cars do it (and Caddy's had it way back when, but it sucked). and it was by design.
newer cars do it by using a pin to deflate hydraulics on the cylinders not needed. this is done in conjunction with the puter pulling the fuel to those pots and adjusting the timing and other factors. and in the end, one does not save that much fuel. one of the new cars has it integrated into the normal operation of the vehicle, much like VTEC and other similar programs. when you mash the gas, it runs all the cylinders, but as you let off the gas or cruise, it cuts down to 6 or 4 cylinders. i read a review and it was said to actually be very organic and unobtrusive. but it was designed to do so; retrofitting would almost be out of the question. and the gas savings are not that impressive.
to try it: pull 4 plug wires and see how you like the way the car runs. LOL. it wont.
the thing that i worry about is what do you do when the system fails (on the new cars). that, to me, goes into the "wait and see how it does in the long run" pile, much like electro-throttles and electric steering. but like with VTEC and BMW's system (VANOS IIRC), which are some of the older ones, i have not read anything about them failing with a lot of miles. comes down to how well it was engineered.
my two cents worth. i know Michael will write a novel on this topic! (and i look forward to reading it).
newer cars do it (and Caddy's had it way back when, but it sucked). and it was by design.
newer cars do it by using a pin to deflate hydraulics on the cylinders not needed. this is done in conjunction with the puter pulling the fuel to those pots and adjusting the timing and other factors. and in the end, one does not save that much fuel. one of the new cars has it integrated into the normal operation of the vehicle, much like VTEC and other similar programs. when you mash the gas, it runs all the cylinders, but as you let off the gas or cruise, it cuts down to 6 or 4 cylinders. i read a review and it was said to actually be very organic and unobtrusive. but it was designed to do so; retrofitting would almost be out of the question. and the gas savings are not that impressive.
to try it: pull 4 plug wires and see how you like the way the car runs. LOL. it wont.
the thing that i worry about is what do you do when the system fails (on the new cars). that, to me, goes into the "wait and see how it does in the long run" pile, much like electro-throttles and electric steering. but like with VTEC and BMW's system (VANOS IIRC), which are some of the older ones, i have not read anything about them failing with a lot of miles. comes down to how well it was engineered.
my two cents worth. i know Michael will write a novel on this topic! (and i look forward to reading it).
Michael Yount
Mustang Master
You covered it pretty well Hissin - Cadillac used to have a system for deactivating cylinders/cutting fuel/runnning on a few cylinders back in the shortage days - V8-6-4; nothing but problems with it. Memory tells me it tried to use hydraulics to deactivate the valves for those cylinders. See the links below - search google under "cylinder+deactivation" - more than you want to know. As you can see by reading about it, it's not practical to implement on our engines.
THey (GM/Cadillac) and others (Honda, Dodge, Chrysler) have revived a system for their newer cars again to boost mileage - much more sophisticated, uses electronics and electro-hydraulics to kill fuel and deactivate valves in certain cylinders. We'll see how it holds up - but as hissin pointed out, we've come along way since Cadillac's original V-8-6-4 days. The BMW 7 series doesn't use a throttle to control engine speed. They have infinitely variable lift - they vary lift to control engine speed - drive by wire completely. Cadillac manages overheating with a limp home mode that kills four cylinders and let's air pump through those four to help cool the engine while you limp home - and it varies the cylinders to provide even cooling.
Like hissin, it's scary to contemplate what's gonna happen to those cars as they get older and start to fail. We'll have a new class of junkyard - economic junk -- big, expensive, nice cars that have electronic failures, but they're too expensive to be repaired by the third or fourth owners. I'm not too worried about some of the systems - variable valve timing, variable intake runner lengths have been around for almost 20 years - I think they're reliable. At least the Japanese versions - funny that Ford's making such a big deal of it on the new pickup - they and others have had versions of it on their smaller engined cars for years. It's all the electronics that concern me - the 2001 version of the new 7 series tested by C&D had 123 electric motors on it. Can you imagine the alternator needed?
http://www.delphi.com/media/news/product_info/cyl_deact/
http://waw.wardsauto.com/ar/auto_two_four_six/
THey (GM/Cadillac) and others (Honda, Dodge, Chrysler) have revived a system for their newer cars again to boost mileage - much more sophisticated, uses electronics and electro-hydraulics to kill fuel and deactivate valves in certain cylinders. We'll see how it holds up - but as hissin pointed out, we've come along way since Cadillac's original V-8-6-4 days. The BMW 7 series doesn't use a throttle to control engine speed. They have infinitely variable lift - they vary lift to control engine speed - drive by wire completely. Cadillac manages overheating with a limp home mode that kills four cylinders and let's air pump through those four to help cool the engine while you limp home - and it varies the cylinders to provide even cooling.
Like hissin, it's scary to contemplate what's gonna happen to those cars as they get older and start to fail. We'll have a new class of junkyard - economic junk -- big, expensive, nice cars that have electronic failures, but they're too expensive to be repaired by the third or fourth owners. I'm not too worried about some of the systems - variable valve timing, variable intake runner lengths have been around for almost 20 years - I think they're reliable. At least the Japanese versions - funny that Ford's making such a big deal of it on the new pickup - they and others have had versions of it on their smaller engined cars for years. It's all the electronics that concern me - the 2001 version of the new 7 series tested by C&D had 123 electric motors on it. Can you imagine the alternator needed?
http://www.delphi.com/media/news/product_info/cyl_deact/
http://waw.wardsauto.com/ar/auto_two_four_six/
You could change the firing by changing plug wires, but the computer would keep sending fuel to each piston regardless of change. You could also just unplug the plug wires, but the cylinder will flood with fuel as someone above said. But no, you can not change the firing order for a significantly better fuel/performance gain at will because of the computer.
Just FYI, the 05' Mustang will have a "Fail Safe Cooling" mode. When coolant is lost, the computer will limit it to less power to reduce heat. If below a critical leve, it will be in "Limp Home" mode. Basically when the coolant sensor detects overheating, it will fire on half the cylinders, chaning from odd to even cylinders; it can reach up to 50 mph in this mode.
Just FYI, the 05' Mustang will have a "Fail Safe Cooling" mode. When coolant is lost, the computer will limit it to less power to reduce heat. If below a critical leve, it will be in "Limp Home" mode. Basically when the coolant sensor detects overheating, it will fire on half the cylinders, chaning from odd to even cylinders; it can reach up to 50 mph in this mode.
Michael Yount
Mustang Master
GUys - to change the firing order, you have to change the camshaft. It determines when the valves open and close relative to piston position. The fuel injection and distributor wire order is simply matched to the firing order of the cam. You can't change the firing order just by changing the plug wires around. You could change the "sparking" order ( ) but unless the cam/pistons have determined the compression stroke at that time, and something delivers fuel at the right time, no "fire" will occur.
Sounds like the 05 Mustang overheat mode is a copy of the system Cadillac introduced on the Northstar quite some time ago.
) but unless the cam/pistons have determined the compression stroke at that time, and something delivers fuel at the right time, no "fire" will occur.Sounds like the 05 Mustang overheat mode is a copy of the system Cadillac introduced on the Northstar quite some time ago.
Even if you do kill the fuel to a couple cylinders, the valves are still opening and closing, which means you still get large pumping losses. You really need to have a system to prevent the cylinder from even filling with air. For example, I was reading that the new Hemi is going to have cylinder deactivation, and they are going to use solenoids to cut the oil flow to the lifters and prevent the valves from opening to that cylinder. the whole process takes 40ms. 
Michael Yount said:GUys - to change the firing order, you have to change the camshaft. It determines when the valves open and close relative to piston position. The fuel injection and distributor wire order is simply matched to the firing order of the cam. You can't change the firing order just by changing the plug wires around. You could change the "sparking" order (
Sounds like the 05 Mustang overheat mode is a copy of the system Cadillac introduced on the Northstar quite some time ago.
Thanks for the correction, I meant SPARK order.
I didn't know that Cadillac had a system like that? Was it good? Did it work well?
Michael Yount
Mustang Master
When C&D tested their first Northstar with the system (quite a number of years ago), they intentionally drained the coolant and went for a ride to see what would happen. Seems like they went 25 or 30 miles on no coolant - got bored with it, filled it back up and drove on. Worked pretty well.
bhuff - click the links/search back earlier in the thread - lots of stuff about cylinder deactivation.
bhuff - click the links/search back earlier in the thread - lots of stuff about cylinder deactivation.
JaysGreenLX
Founding Member
Sounds to me like someone was reading about the Chrysler 300C. The Hemi version has a 4 cylinder mode for highway cruising to save on fuel.
It's that or you had google handy.. lolThe gas-saving mode sounds great and all but you still have a parasitic drag where the cylinders that are firing are haveing to pull the ones that aren't around on the crank revolution, or is this not a problem?
I though Jaguar had a system like this except they had two engines running to equal a V8 and to save gas it just shut one of them down.
And if you really wanted to kill the fuel to the cylinder, just disconnect the connector to the fuel injector so it doesn't receive the pulse to fire (expect a nice mis-fire though).
I though Jaguar had a system like this except they had two engines running to equal a V8 and to save gas it just shut one of them down.
And if you really wanted to kill the fuel to the cylinder, just disconnect the connector to the fuel injector so it doesn't receive the pulse to fire (expect a nice mis-fire though).
I only skimmed through the posts so forgive me if this has been covered already:
Regardless of what you do with fuel, spark, etc... you will still not be able to just shut down cylinders on a Stang and have it run anywhere near smoothly or reliable. It looks like something very important was forgotten in this thread. THE CRANK. 5 oh cranks were not designed to run on anything less than 8 cylinders frining in the order they were inteded to fire. If you were to try running the car that way there would be huge gaps in the stroke and you can actually run the risk of a cylinder firing on the opposite of what should be the down side for the crank. Even assuming you were able to find a firing combination that allowed you to keep rotating the crank inthe correct direction, the grind and length of the stroke on a 302 running on 4 cylinders would shake your teeth loose. Those cars mentioned above that are capable of running on less than all cylinders all have computer designed cranks that allow them to be smooth and operational on the remaining cylinders. Because of that, they don't end up firing for what would amount to "one quarter" of a stroke.
Regardless of what you do with fuel, spark, etc... you will still not be able to just shut down cylinders on a Stang and have it run anywhere near smoothly or reliable. It looks like something very important was forgotten in this thread. THE CRANK. 5 oh cranks were not designed to run on anything less than 8 cylinders frining in the order they were inteded to fire. If you were to try running the car that way there would be huge gaps in the stroke and you can actually run the risk of a cylinder firing on the opposite of what should be the down side for the crank. Even assuming you were able to find a firing combination that allowed you to keep rotating the crank inthe correct direction, the grind and length of the stroke on a 302 running on 4 cylinders would shake your teeth loose. Those cars mentioned above that are capable of running on less than all cylinders all have computer designed cranks that allow them to be smooth and operational on the remaining cylinders. Because of that, they don't end up firing for what would amount to "one quarter" of a stroke.
Michael Yount
Mustang Master
87GTStang - when the newer engines go into 4 cylinder mode, they also deactivate the valves (intake and exhaust valves stay closed) on the 4 cylinders that aren't firing. Since those cylinders aren't pumping air in and out every stroke there's a significant reduction of what's called 'pumping' losses. That's part of makes the setup more efficient. Another thing that happens is that when you ask only 4 of the cylinders to do twice the work they were doing before, the throttle has to be open further - which reduces pumping losses to the four cylinders that are working. Since those four cylinders are working harder (more air and fuel per stroke) they are more efficient at filling the cylinder - and that saves fuel as well.
Now that we have the ability to more reliably deactive cylinders, and the electronic ability (computer control of ignition and fuel on a per-cylinder basis) to carefully control what's happening in the cylinders that are firing, these systems work much better. And, as Daggar points out, these engines were designed with cylinder deactivation in mind - so the firing order was likely chosen so that 4 cylinders could be used that would even out the power pulses when in 4 cyl. mode.
"The Hemi version has a 4 cylinder mode for highway cruising to save on fuel. " A BUNCH of vehicles have it now - from a bunch of different manufacturers.
Now that we have the ability to more reliably deactive cylinders, and the electronic ability (computer control of ignition and fuel on a per-cylinder basis) to carefully control what's happening in the cylinders that are firing, these systems work much better. And, as Daggar points out, these engines were designed with cylinder deactivation in mind - so the firing order was likely chosen so that 4 cylinders could be used that would even out the power pulses when in 4 cyl. mode.
"The Hemi version has a 4 cylinder mode for highway cruising to save on fuel. " A BUNCH of vehicles have it now - from a bunch of different manufacturers.
5.0fox
Member
the caddy v8-6-4 use solonoids to cut off the oil to lifters to allow them to colapse therefore not open the valve. it didnt work well and they are very rare now.
changing the firing order is a very common thing on high performance chevy v-8s they often swap the cylinders 4 and 7 to prevent air from being drawn from the same corner of the intake 2 cylinders in a row. it is said to greatly improve horsepower.
what determins the cylinders that can be swapped is the way the plug wires are arranged, the grind on the cam, and the crank throw that the rods are on. a cylinder can only be swapped with one who shares its crank throw.
i know all this and im only 16!
changing the firing order is a very common thing on high performance chevy v-8s they often swap the cylinders 4 and 7 to prevent air from being drawn from the same corner of the intake 2 cylinders in a row. it is said to greatly improve horsepower.
what determins the cylinders that can be swapped is the way the plug wires are arranged, the grind on the cam, and the crank throw that the rods are on. a cylinder can only be swapped with one who shares its crank throw.
i know all this and im only 16!
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