Creating a Switch to Shut Off Cylinders on the Fly - Gas Savers

SVOboy · 09-06-2005, 04:23 PM

I saw someone talking about how on their old volvo they had made a switch to shut off two of their four cylinders while at cruising speed. From what I understand it is just installing a switch to shut of the fuel injectors going to each cylinder, but the spark and all that keep going...so, if I do this will it harm my engine or make it wear oddly? Does this seem like a safe thing to try out in terms of engine health and all that? Hmm, thanks.

Matt Timion · 09-06-2005, 04:44 PM

Do you have a link to the guy talking about it? I'd like to read more about this.

SVOboy · 09-06-2005, 04:49 PM

I got it in an email it was just like, I did that, and nothing about it. I will look for some though eh. And something about doing it with dpfi. ^_^

diamondlarry · 09-06-2005, 04:49 PM

I'm not sure if this is what he's talking about but here is a link to something similar.
http://autos.groups.yahoo.com/group/BetterMPG/message/2595

SVOboy · 09-06-2005, 04:51 PM

That's what I was talking about, haha.

chasgood · 09-06-2005, 06:30 PM

The new Chrysler 300 V8 does something like that. It automaticly shuts off 4 cyl's when the power is not needed. So it is a doable project.
If you worry about uneven wear set up all 4 injectors and every month switch from 1 and 3 to 2 and 4.

SVOboy · 09-06-2005, 06:41 PM

Yeah, a lot of the US autos are moving that way from what I understand, but really only the gas guzzlers, so, makes people feel good about themselves for gettin 10mpg instead of 8, sigh. I dunno why they won't do it for resonable stuff like I dunno, are there any US cars that get over 30 avg...? In any case, I have a 4 cylinder, but it only has two injectors, so you think I can still do this by shutting off one injector?

chasgood · 09-06-2005, 07:31 PM

It would be the front 2 or the back 2 cyl. It would depend on the firing order. It could make the engine run to ruff. It may just work better the more cyl there is. That is why car makers only use it in V8's. Wont know till you try it.

Matt Timion · 09-06-2005, 08:31 PM

This would be a VERY EASY modifcation to use. I'm curious though as to what happens with the two other cylinders? So the injectors don't shoot gas, but they still get air. The spark still shoots. I guess the momentum of the previous cylinder's explosion will still propel the piston downward, so i guess it won't lock up or anything. I dunno. For some reason I just get the feeling that it can't be good to do this to an engine. Will it cause emission problems?

Someone with a better understanding of engines has to be able to answer these questions.

The good thing about this is that it would be a VERY easy modifcation. It would be all in-cabin wiring. You could even hook up four switches, one for each cylinder.

Maybe a device could even be created that would switch between cylinders every minute. Minute 1 injectors 1,2,3 and on, and then minute two 2,3,4 are on... etc. etc.

Someone convince me this isn't bad the the engine.

SVOboy · 09-06-2005, 08:46 PM

Hopefully he can give us a straight answer about this, and with dpfi would be good for me too...^_^ Worthless dpfi that it is.

bense · 09-06-2005, 09:31 PM

well here's the deal. you have 4 pistons (obviously) and so two of them go down, two of them come up. however it is the middle pistons that go down and the outer pistons that come up. by doing this, the motor is balanced at all times. the combustion is being put on the middle two pistons pushing them away from the head to the bottom (BDC bottom dead center) and pushing the outer two pistons to the head to the top of the combustion chamber (TDC top dead center)

if you were to disable any of the pistons, you would want to disable one of the inner two pistons and one of the outer pistons. pistons are numbered 1,2,3,4 you could either disable pistons 1 and 3 and have pistons 2 and 4 firing. Or have pistons 4 and 2 disabled and have pistons 1 and 3 firing.

now, i am not sure, however, my hypothesis is this. even if you were going to get those pistons disabled while cruising. you would have to push harder on the gas and make these two pistons work harder than they normally would.

as far as disabling a injector. the spark plug would be doing the same thing as strikign the flint on a lighter without pushing the button that releases the butane. It would spark, and that's it.

i am not necesarily sure if running on two cylinders would be advantageous or not. it makes me wonder though.

Matt Timion · 09-06-2005, 10:43 PM

Quote:

Originally Posted by bense

now, i am not sure, however, my hypothesis is this. even if you were going to get those pistons disabled while cruising. you would have to push harder on the gas and make these two pistons work harder than they normally would.

i am not necesarily sure if running on two cylinders would be advantageous or not. it makes me wonder though.

I was thinking the same thing actually. Wouldn't RPM go up at this point? Wouldn't the ECU detect a very lean mixture coming out of the exhaust and start running the two remaining injectors REALLY rich? Wouldn't this lead to wasted fuel?

SVOboy · 10-09-2005, 11:19 AM

Might as well post up this, but I recently learned this is impossible on dpfi engines because it is usually running on only one injector and then the second injector kicks in under heavy load. So I'd end up killing the only injector.

Matt Timion · 10-09-2005, 11:37 AM

Quote:

Originally Posted by SVOboy

Might as well post up this, but I recently learned this is impossible on dpfi engines because it is usually running on only one injector and then the second injector kicks in under heavy load. So I'd end up killing the only injector.

How odd. I guess this is the reason why people call DPFI a "glorified carb."

That's all it really is... just a glorified carb with fuel injectors.

MPFI seems to be the way to go.

kickflipjr · 10-09-2005, 05:29 PM

I would be able to do this on my car fairly easily. But it seems like it would be bad on the engine. With 2 cyl getting no fuel, wouldn't it put wear on the cylanders not getting any fuel.

SVOboy · 10-09-2005, 08:53 PM

It should only put as much wear on them as they would get normally, mehbe less because things are blowing up in there.

b1gmoose · 10-10-2005, 12:07 PM

Do you disable the spark plugs as well? Wouldn't a sparkplug not burning any fuel on the compression stroke burn a hole in the top of the cylinder after say 10K miles or so? Any ideas?

~ryan

Matt Timion · 10-10-2005, 12:24 PM

Quote:

Originally Posted by b1gmoose

Do you disable the spark plugs as well? Wouldn't a sparkplug not burning any fuel on the compression stroke burn a hole in the top of the cylinder after say 10K miles or so? Any ideas?

~ryan

I'm not sure how a spark without fuel would be more damaging than a spark WITH fuel. It seems to me that the violent explosion would be more damaging than a tiny little spark.

SVOboy · 10-10-2005, 12:31 PM

Quote:

Originally Posted by Matt Timion

I'm not sure how a spark without fuel would be more damaging than a spark WITH fuel. It seems to me that the violent explosion would be more damaging than a tiny little spark.

I agree, though it's easy enough just to hook the switch up along the spark plug wires if you so wish.

Matt Timion · 10-10-2005, 12:46 PM

Quote:

Originally Posted by SVOboy

Quote:

Originally Posted by Matt Timion

I'm not sure how a spark without fuel would be more damaging than a spark WITH fuel. It seems to me that the violent explosion would be more damaging than a tiny little spark.

I agree, though it's easy enough just to hook the switch up along the spark plug wires if you so wish.

Agreed. It would be best to do the switch to turn off both the injectors and the spark plugs. This would also increase the life of your plugs.

Flatland2D · 10-10-2005, 01:09 PM

Remember there are several thousands of volts across the spark plug wire. If you used a switch to directly cut off current to the plug, the high voltage would surely jump the contacts of the switch and short it out.

SVOboy · 10-10-2005, 01:22 PM

Surely there is someplace to control power to the plugs besides the actual wires? I would think so, but snuggling into the ecu might not be the best idea for something meant to be simple, or mehbe this is actually a hard thing to do. I figure someone just needs to do it and leave the plugs firing to see if it helps mpgs before we get all complicated with it.

Flatland2D · 10-10-2005, 01:44 PM

That's a good point. There's no reason to get complicated if the principle just won't work. I really don't see why you would need to worry about the sprak plug still firing. Even if they did wear out slightly faster, they are only $1.50.

I'm not an expert on ignition systems, but I would think most of the control is being done by the distributor. I know the ECU can affect timing but I'm not sure how. Maybe the ECU can only shift the timing but not cut it off completely? The entire system might be high voltage.

Come to think of it, you could effectively turn off the spark plugs by shorting them out. You'd put a switch in parallel with the plug and when it's closed, there would be no gap. You'd also need a resistive load in series with the switch, but this would probably be the simplest way of doing it.

kickflipjr · 10-10-2005, 02:40 PM

Any person who mods turbochargers will tell you that if you go too lean it will destroy the engine.

I assume it would be ok if the spark plugs were shut off along with the fuel injectors. But i'm not doing that, don't turst my wiring ability with spark plug wires.

SVOboy · 10-10-2005, 02:42 PM

That's true about being to lean, of course, but I don't think this would really lean it out, you'd still be taking in 14.7:1, just only blowing it up in two cylinders instead of four.

Diemaster · 10-10-2005, 04:27 PM

we could devise a method where, at highway speed, the injectors (mpfi) shut off for 1 & ,3 a pice of cardbord gets wedged between the contacts in the dizzy to keep the plug from firing, and a metal plumimg valve would open or vent between the spark plug and the head.
this would elimate all drag from the 2 unused cylenders. we could get advanced and evrey other fring order the 2 would switch. so 1-3-4-2 would die then next 1-3-4-2 would die. :P

in thearoy this is posible all within the ecu, except the vent valves but it could work

my car has I-VTEC & I-CCSY (cylender canceling system) :P

SVOboy · 10-10-2005, 04:30 PM

Wow, when you say in theory that this would work, I understand a bit from the ecu point of view, but not the mechanical point. So I'm wondering would you be able to chip for that and then not vent and see an improvement or would you have to do the whole damn thing?

On a related note, is chipping the pm5 possible? I want to lean out idle and some cruising speeds. ^_^

Diemaster · 10-10-2005, 04:38 PM

yes it is possable but your onn your own whin it comes to reprograming it. i spent 2.5 years looking and i couldent find ****.

SVOboy · 10-10-2005, 04:44 PM

Yes, I looked on pgmfi and the thing was just like: dpfi, the bastard that is like no others. I figure I should at least be able to find a base map to work from right?

Flatland2D · 10-10-2005, 04:58 PM

Remember that when the engine is being overdriven (coasting but still in gear) the ECU detects this condition and usually cuts off the injectors itself. There is obviously no short term effects of turning off injectors and leaving the plugs firing. I doubt there would be any significant long term damage also.