Kill Switch: 2007.5 Dodge Ram 2500 Diesel
 

Well, it took me a while but I finally got my kill switch installed and working. I thought up the idea months ago(http://ecomodder.com/forum/showthrea...tch-22336.html), but finally did it today.

I've been doing EOC by using the keyswitch and I was tired of "losing miles" during EOC during the time the key was off (while I'm waiting for the engine to come to a complete stop so I can turn the keyswitch back on).

I came up with the idea of putting a switch in the wire where the keyswitch signal goes into the ECM. I suspected that the odometer fuctions were taken car of by the body computer (not the ECM), so if I switched off the wire going into the ECm, while leaving the keyswitch itself on, I'd be able to kill the engine while keeping the body computer (and therfore the odometer) on the whole time. As it turns out I was correct.

I did some digging and found the correct pin on the ECM to switch:
http://ecomodder.com/forum/member-di...mmins-6-7l.png

I simply cut the wire, ran two wires into the cab, and wired them up to a simple household light switch. I just tried it out and it works pretty good! It kills the engine, but leaves the odometer on the whole time. It does "dong" when I kill it and displays "Check Gauges", but it hasn't tripped any fault codes (at least not yet).

I suspect this will probably increase my mileage numbers quite a bit, as I suspect I was "losing" around 5-10% of my miles.

Right now, I couldn't find a good way to get the wire from the engine bay to the cabin, so for now I just ran it through the door. If anybody knows a good way, please let me know.

I suspect this method (of switching the ECM keyswitch wire) may work on other vehicles that have separate engine & body computers, but I'm not sure.

EDIT: I should add that I don't think I'm actually turning the ECM "off"--by that I mean the power remains on to the ECM the whole time (I think). I think this should allow me to use a data logger via the OBD now. I'd tried one before and it was just a pain if I was doing EOC because it would lose connection every time, and require a rest. I haven't tried it yet, but I suspect it should be able to remain connected the whole time now.

Update: On the way to work, my trip meter clocked 24.2 miles. My average when I was using the old method (w/o the kill switch) was 22.7 miles. So I "gained" 1.5 miles (6%). I also checked myself with some mile markers on a speedometer course check that's on my way to work (I think the local Army base set them up). Over the 5 mile course I was within 0.1 miles (2%). Previously, I would "lose" ~0.5 miles or so.

So it seems to be working!

When are you killing the motor? At stoplights, on approach, etc?

Stoplights, yes, but mostly during the "glide" of the Pulse and Glide driving style I use

That is commitment to the cause.

Do you ever worry about lack of oil on the constant start and stop driving of the motor?

With the Hybrids, they seem to have an auto spooling function that somewhat pre-lubes the motor prior to firing. The same is not the case for the diesel.

How much gain have you noted from the start and stop via the kill switch?

I've switched to a 5W-30 synthetic oil from the conventional 15W-40 oil to help the cause. I also use two 150-watt oil pan heaters (in the mornings) to helps bring the viscousity down as well. Also, it's worth noting that, while my engine does have oil lubricating the turbo, it's a water-cooled turbo (not oil cooled like most older turbodiesels). As per my understanding that's the biggest issue with frequent stop-start in diesels--it's actually not so much the start as it is the hot stop, when you can coke the oil in the turbo. Water-cooled turbos don't have that problem because the coolant will continue to have some circulation through the turbo via thermal siphoning.

That being said, I've been doing engine-off pulse & glide for over a year now, and I'll be doing an oil change here in a month or two. I'd like to send my used oil in for an oil analysis to see if there's been any unusual wear.

As far as the gains from the kill switch, it doesn't actually increase my mileage--it just allows me to account for all the miles I actually travel. My average commute distance used to average 22.7 miles and now I'm at 24.3 miles so I've gained about 7%. The engine-off P&G itself gains more than that--the 7% is just the additional amount the kill switch allows me to account for.

If they are water cooled units now, that makes sense. Long overdue too.

Sounds like a plan and sounds like it is working well.

Good job and keep up the good work.

As I understand it, the motivation for switching to water cooling isn't so much because it's "better" per se. The "modern" turbos are variable geometry, which means they have an electronic acuator attached. The electronics need the water cooling, and since the water's already required, they use it to cool the turbo itself as well. If they didn't need the coolant for the electronics, I suspect they'd have stayed with oil cooling.

Water is a more effective transfer medium of heat if I am not mistaken so it would make sense that the water can remove more heat more rapidly.

I like the shift.

Update:

After the kill switch install it became clear that my odometer was off slightly. Before the kill switch there wasn't much sense in correcting the odometer (nor an accurate way to do it).

In the past, I made a couple attempts to use my GPS to determine the distance accurately, but I had issues with my GPS "assuming" my route, rather than actually measuring it. This was particularly true in one area where I typically cross through a vacant parking lot, and also in my neighborhood, which is only a couple years old and not updated yet in the GPS.

I finally gave in a got a smartphone and found a great free app called Runkeeper. It's intended for running (which I do use it for) and it measures your true distance (not assumed) on-road or off-road. I first used it over 10 trips ove various lengths (totaling 284 mi) before touching the odometer:

Min error: -2.6%
Max error: -2.4%
Avg error: -2.51%

So I got out my Smarty programmer and checked the tire size in the computer. It had been set to 30.55 inches, so I moved it up to 31.30 inches (2.45% increase). This is very reasonable since I looked up the nominal diameter of my actual tires and it's 31.40. Here are the results on the next ten trips (totaling 280 miles).

Min error: -0.4%
Max error: +0.4%
Avg error: -0.04%

In every case the error was within the decimal precision of my odometer, so now I know I'm spot on. There's also a marked 5 mi speedometer course check on my way to and from work that I've checked myself against. Every time I'm within the precision margin.

So, to summarize the kill switch gained ~6% and the odometer another 2.5%. So all told I wasn't accountng for ~8.5% of my miles in the past.

Excellent work. With real data, I'm looking forward to seeing your next best tank. And the one after that...

Me too! If I assume I was off my the same amount last summer when I pulled my best tank ever of 47 mpg, adding 8.5% is 51 mpg. And since then I've made a few more mods.

I can't wait for it to warm up! That record tank was with an average temp of 78 deg F. My last was at 29 deg F.

Hey Dave, on my diesel fords when you coast the pcm cuts fuel to the injectors. Do you see a big gain from cutting off the engine? My excursion is auto but my f250 is a 6sp. So I could try it on that.

I just wondered if the Dodge's cut fuel on coasting. You are obviously doing something right haha.

It depends on what you mean by "coasting."

There's basically 3 options (in order of best fuel economy):
A) Coasting in neutral with engine off
B) Coasting in neutral with engine on (idling)
C) Coasting in gear with engine on

I do A. Virtually all computers will turn off fueling for C, but not B. One might be temped to think that C is better for fuel economy than B because C uses no fuel. The issue is that C robs energy from the vehicle because the wheels are being forced to motor the engine, overcoming all the friction and pumping losses at an engine speed significantly over idle speed. That's why it's also called "engine braking". Option B does use some fuel, but only enough to overcome pumping & friction at idle speed--and it doesn't brake the vehicle.

I guess my question is if there is an advantage to engine off coasting vs. engine on coasting if the pcm cuts fuel when you coast. In nuetral of course.

The computer can't cut fueling if you're coasting engine-on in neutral because there'd be nothing to keep the engine turning.

Got you.. Been driving my automatic but thinking of my 6 speed haha.

Diesel_Dave, your mileage astounds me. Imagine what you could do with something smaller like a VW TDI!