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usergone 05-17-2010 06:15 PM

Manual DFCO, EGR, accessory belt "clutches"
First I'd like to say "hello!" to everyone. I came here because I am extremely into DIY and realized that this forum is quite into that.

I am a young guy in North Texas with a 1986 Jeep Comanche, 4 CYL 2.5L, mated to a 5 speed manual. It has some "All Terrain" 30s on it (same tires as when I got this truck 3 years ago). It is definitely not the best example of fuel frugality, but I believe there is some amazing potential here.

It gets about 18 MPG (yes, compensated for the big tires) and I don't exactly push it to go fast, or be quick off the line. (the fastest I have had it was flirting with 80! :eek: Horrors upon horrors! :))

Recently I had the whim of putting a switch on the injector (it is a TBI) for DFCO, and for general killing (for EOC, as well) so I went and made a big shift handle that I could put switches in. Right now it has only one hooked up: the injector kill switch. I have been using it for a few days, and I must say that it seems to work quite well (but I still need practice).

The first of my questions is this; when should I be using DFCO. I know I can use it to engine brake and not be using fuel (just making sure I keep it above ~1000 RPM), but I am sure I am missing something.

There are 5 buttons on my new shifter. one is taken up by the injector kill. What else might I use the other 4 for?

I was thinking maybe 2 for EGR: one to force it off, one to force it on, neither active for normal. I put a light bulb on the vacuum valve to see when exactly it is active. What gains would I see by messing with EGR?

Another thing: this truck has P/S. When stopped, it certainly takes a wrestling match to turn the wheel. When moving, it is actually quite nice without P/S (feel the road more)(learned this by EOC). How difficult would it be to find a clutch (like on the AC pump) to put onto the P/S pump?

My, my, my. That is a long post. Certainly left it open for conversation, didn't I? :p

RobertSmalls 05-17-2010 09:09 PM

DFCO uses no fuel, but it does drain momentum from your car much faster then engine-off in neutral. Once your engine is warm, it's better to shift to neutral earlier and EOC instead of DFCO.

Power steering: I don't think anyone's done the clutch thing. But maybe there's a manual steering rack / gearbox that will fit your car?

usergone 05-17-2010 11:21 PM

I have been thinking about that actually. If I try to DFCO, I wind up staying in gear much longer (on the gas) because it is not coasting - it is either accelerate or decelerate. If I do neither, I wind up with the engine freewheeling at a higher RPM.

Maybe I won't be DFCO-ing as much as I thought. Don't get me wrong, I never thought I would be using it solely as my "no fuel coasting" but I thought I would use it more.

Redo: it isn't a DFCO switch! It is an engine kill switch for EOC-ing! :thumbup:

I have actually looked into a manual steering box, and from my research, it seems as though one exists, but it must be an elusive endangered species - manual steering! The nerve! Why should I have to use more than one finger to steer!?

Maybe I will look harder for one of those.

Christ 05-17-2010 11:33 PM

No, keep it a DFCO switch with EOC ability.

DFCO is great for keeping your foot off the brakes when you're going down hills and such. You downshift, then kill the injector.

Piwoslaw 05-18-2010 01:46 AM

Welcome to EM:)
How about partailly electric P/S? The pump is electric, not belt driven, and you can have it turn off above a certain speed. Or just disconnect the pump and drain the fluid, that's what a few members have done.
As for switches: Maybe an alternator kill switch? Turn the field wire on when accelerating and engine braking, off when coasting.
Also, a switch for a manually operable grill block. Mine is opened/closed with a power lock motor.
Hmmm, what else? If you have A/C, you may want to manually control it. That is, if it turns on automatically, as mine does, damned engineers:mad:

usergone 05-18-2010 07:51 AM

lol, it doesn't matter what I call it, it does the same thing regardless.

Yesterday I was outside messing with the alternator. The only conclusive knowledge I gained was that my alternator is not reliable. I think it is a problem with the field circuit. Great. I have been charging the battery whenever I am at home, though.

I was thinking of making an alternator kill switch, but something else popped into my mind. I have some wires going from the vacuum valve that controls EGR to inside the cabin, to a light bulb. This makes it so that I can see what the solenoid is doing. Here's the breakdown: light on with cold engine, or engine idling/using very little power. Light off when I accelerate (even a little bit) on a warm engine.

This seems to me to be the perfect place to tap into for an "automatic" alternator de-fielding. I may still want it on a switch.

My AC pump is, thankfully, only on with certain settings. I think. I am not sure about defrost, but I know it is on for AC use! The pump is easy to disable. Sometimes it disables itself. The little wire going to the clutch comes unplugged from time to time (ah, yes, the olden days of cars with one wire signals).

Electric P/S. Not so sure about that one. Sounds like it will be more expensive than other choices, like going to straight manual.

RobertSmalls 05-18-2010 10:23 AM

I did a search for that gearbox, and got a few hits in Texas for $60+. only searches professional automotive dismantlers with computerized inventories, and you probably want a U-Pull-It.

usergone 05-18-2010 05:21 PM

Hmm, maybe I was being a bit too presumptive :rolleyes:

That is actually quite in my price range. I will indeed have to look into that. Maybe I need to stop being lazy and go to the pick-and-pull place... I have a list of parts I am looking for.

usergone 05-18-2010 08:59 PM

Out of boredom, I took apart the alternator to figure out what was wrong with it. I guess I scared it, cause when it went back together, it worked fine.

I put a relay on the field circuit, and now I have a switchable alternator. I'll have to see how far I can go without it. When it tested it, I was amazed that I could in fact feel a difference between alternator and no alternator.

usergone 05-24-2010 07:25 PM

Over the weekend I went to the car graveyard and picked up some new toys. That is, some relays, a seat belt, and a cooling fan.

Now the switches on the shifter are as follow:
Injector kill
Radiator fan
Alternator activate

I have a hierarchy set up with the relays so that the alternator can turn on independently. If I turn on the fan, the alternator comes on. If I activate the A/C pump (clutch), the fan comes on, and thus, the alternator.

Do you guys have any ideas for a thermostat for the fan? I would prefer something that does not require me to piece together an electronic circuit. Maybe a water heater thermostat?

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