Civic alternator shut off, the easy way

[brucepick]

I'm convinced that for this project to actually serve your driving needs, the deep cycle battery needs enough capacity to handle a typical day's drive, probably that would be to work and back plus a few errands. Of if your usual weekend drives are longer, you might want it sized to handle those.

SO -
If your setup has that capability, you don't need to switch the alt on and off frequently. Only for the occasional longer trip, or one that has unusually heavy use of lights and/or other electrical accessories. With that as a basis, I see it as not a big deal to pop the hood to switch the alt's output on/off, and to attach or detach the 4-pin connector. On occasion, not very often.

My alternator is unplugged and disconnected from the car's system nearly always. I find myself connecting it less than once a week on average.

Remember, if your deep cycle gets discharged so far that it needs to be charged before you get back home, you'll be charging it using gasoline - and that's exactly what you're trying to avoid with this mod. My system still has the regular starting battery, hooked up ONLY to the starter. It doesn't get very depleted from a few days use in starting the engine. If the deep cycle gets depleted, I can switch things over pretty easily without tools, to run the car off the alt and the regular starting battery till I get home.

That way the alt doesn't need to charge up a run-down deep cycle battery. Doing that regularly might wear out the alt; really it's designed to provide about 70-80A max current. That's to keep the accessories running as needed, and to top up a battery that has just started the engine, and then keep it topped up with a slight positive voltage charge on the system. Long term high current to charge up a depleted battery might not be ideal if done frequently.

[wagonef8]

I see I mostly deal with older Honda's 88-91 so maybe if you add a separate 12v wire for VSS and toggle on alternator it might work

[steffen707]

Originally Posted by wagonef8

I see I mostly deal with older Honda's 88-91 so maybe if you add a separate 12v wire for VSS and toggle on alternator it might work

If this alternator fuse is only 15amps, then it won't disable the main charging wire, because that can be 50-60amps(even higher, i don't know).

So if that's just disabling the yellow/black field exciter wire, then we're back to square 1 of, "the alternator only needs 1 wire to charge".

Or so i'm thinking. I'll have to find the alt fuse and test this theory.

Originally Posted by brucepick

SO -
If your setup has that capability, you don't need to switch the alt on and off frequently. Only for the occasional longer trip, or one that has unusually heavy use of lights and/or other electrical accessories. With that as a basis, I see it as not a big deal to pop the hood to switch the alt's output on/off, and to attach or detach the 4-pin connector. On occasion, not very often.

Yeah that certainly does make sense. I'm going to do a few more tests before I give up. Last night out of curiosity I disconnected the 4 pin plug again, made a jumper from the alternator charging control wire to ground, like in my original post on this thread, and it appeared to not be charging at all. With a large electrical load I was seeing 11.x volts, whereas with my original setup it looked to be still charging just at a slow rate. I'm wondering if some combination of this ground and pulling one of the other 3 wires will disable the alternator.

So i'm going to go out and check.

[steffen707]

I looked in the manual, the #15 fuse controls the alternator, vss, eld unit, evap purge control oxygen sensors and tcm. That's for a 96 civic anyhow.

[wagonef8]

Have you guys considered running one of these I have one on my other civic for performance

[California98Civic]

I did consider an aftermarket pulley, but bigger gains are to be had by disabling the alt's field windings, virtually eliminating parasitic load of the engine, and charging off the grid. The pulley is less effective. But I suppose if you have it already, you could put it to use: fully charge your battery off the grid each night and let the pulley do its part?

[wagonef8]

I probably do that instead I'm also running a xs power d680 battery on my Del Sol its considerably lighter then the stock battery

[steffen707]

Well I've spent hours testing today and i've confirmed and refuted some theories with the Honda alternator.

My test setup:
96 civic hatch, with 96 civic alternator on a 92 d15z1 engine. I think the obd1 civic alternators operate the same way as the obd2a civics, but I can't be certain as I didn't test it.

I had a basically dead car battery (so dead that it wouldn't run the fan or light up any lights) and hooked that up to the battery cables. I then used a known good working battery to jump start the car for the beginning of each test. As soon as the car started I disconnected the jumper cables to isolate the good battery from the bad one.

The car was brought up to operating temp.

Note: When its up to temp when you start the car, the engine doesn't rev over 2000rpm. This is an important thing to remember, because when you test the voltage at the field winding with the car off there is .01volts, when you start the car its .05-.3 volts. When you rev it past 2000rpm it now reads 3-5volts and even if you let the car idle, it will stay at 3-5 volts.

There are 5 wires at the alternator. 1 white "B" charging wire, 1 yellow/black "IG" field winding exciter wire, 1 white/green "C" charging control signal wire from the ecu, 1 white/blue "L" charging warning lamp wire, 1 white/red "FR" charging rate wire from the alternator to the ecu.

I disconnected these wires directly from the 4pin plug at the alternator for guaranteed results.

Don't try pulling the alternator fuse because the manual, says it controls the alternator, vss, eld unit, evap purge control oxygen sensors and tcm. That's for a 96 civic anyhow. Its much better to disconnect the "IG" wire at the alternator.

TESTS:

1. First test was unplugging all 4 wires together. The car immediately died after disconnecting the jumper cables, but wait..... If you rev the engine past 2000rpm before disconnecting the jumper cables, the car would run very poorly. headlights would flash, the fan would pulse, it is a not drivable but actually charging at a super small amount.

2. Disconnect all 4 wires, but ground the "C" wire, The car immediately died like in 1, but if you revved it past 2000rpm before removal of the jumper cables the car idled, but was more rough than in 1. This is because grounding the "C" wire tells the alternator to charge at the lower rate.

3. It has been thought you can simply disconnect the "IG" wire and disable the alternator. This resulted in charging the battery and providing enough power for lights, fan stereo, ect. The car idled just like normal and you could drive the car just fine. This didn't work.

4. Another ecomodder ecomodder California98Civic http://ecomodder.com/forum/showthrea...8-a-20513.html told me that he found out that if you disconnect the "IG" and the "L" wire this disables the alternator. He thought that the "L" circuit was providing enough power to energize the field windings. Well he was right. I tested this by starting the car with both "IG" and "L" disconnected and it operated just like test 1. I also tried starting the car with just "IG" disconnected, removed jumper cables, the car ran fine, then disconnected "L" on the fly, the car imediately starting running super rough like test 1.

5. I read that if you soft ground the "IG" wire via a light bulb this will disable the alternator. With just soft grounding "IG" the results were the same as test 3.

6. With disconnecting "L" and soft grounding "IG" i got better running characteristics and presumably better charging than in test 1. (I can't remember if it was like normal running, or just smoother test 1 running, sorry. This isn't a good option anyway.

People should either do 1, 2 or 4. 1 and 4 are almost the same, except with 4, the "C" wire is still connected to ecu. I feel however that 2 is the best.

So what did I end up doing? Well you can disconnect the "L" wire anywhere between the alternator and the ELD. So for ease of turning back to stock i simply took the charging bulb out of the dash and got the same results as if you disconnected it at the alternator.

I also used a dpdt switch in the UP SETTING to switch "C" to ground, and simultaneously switch off the "IG" wire. This is the same as test 2.

In the DOWN SETTING the dpdt switch will reconnect the "C" and "IG" wire to their normal connections, allowing full use of the alternator in normal configuration. The only thing is that you will never see a charging problem because you took the bulb out; however, if you use a voltmeter to monitor the battery as most would be doing, you will notice when something isn't right. We don't need no dumby lights.

This DPDT switch also has an OFF setting in the middle. In OFF mode, you get the same results as test 1 except that the "FR" wire is still connected. I didn't notice any differences in any of the tests with or without "FR" connected.

So how did the MPG compare?? I picked out a flat 35mph road and picked out 2 mailboxes 1 mile apart. Car was up to temp, car was already cruising at 40mph before I got to the first marker to eliminate variation with acceleration up to 40mph. Once I passed the marker I reset mpguino to calculate just the mile long MPG. I read what mpguino said at the mile marker and then slowed down after.

I calculated from A-B and B-A, I tested with high beams on, fan on full blast, A/C off, and rear defroster on. I did the alternator on tests with a fully charged battery first to eliminate any extra load from trying to charge up a low battery from the other 2 test types. This was a high load test, i didn't have time to also test no load, but plan to do that sometime this week.

Results A-B Full load:
Alternator On normal: 70.7, 68.8, 68.1 = 69.2 average
Alternator Test 2 setup: 73.4, 76.7, 73.6 = 74.5 average
Alternator all 5 wires disconnected: 74.9, 74.2, 74.5 = 74.5 average

Results B-A Full load:
Alternator On normal: 62.8, 61.5, 62.2 = 62.16 average
Alternator Test 2 setup: 68.7, 69.7, 69.8 = 69.4 average
Alternator all 5 wires disconnected: 69.2, 68.8, 69.0 = 69.0 average

Alternator test 2 setup and completely disconnected (except belt) resulted in almost identical results. I truly think that test 2 setup hardly provides much charge, and thus puts very little mechanical load on the engine.

In the A-B test i saw a 7.65% gain in mpg, and B-A was a 11.6% gain.

I'm going to post these results on the first post of the thread as well.

[brucepick]

Nicely done!

[steffen707]

Originally Posted by brucepick

Nicely done!

Thanks! I tried to be very thourough as i don't want to do this all again if I forgot something. I'm pretty happy with the overall results and i think that they're right in line with what others have observed.

the Honda charging system is pretty smart though, and I bet with little to no load the gains won't be as much. That being said, you could just drive farther then on the same battery, have to rely on grid charging less, or use less overall charging via the grid.

Either way i think when people are taking mirrors and wipers off to gain MPG, the alternator disable is a great way to gain MPG.

I forgot to cover that I did one test run the other day and found that without the 4pin plugged in, no load and full load both resulted in almost the same 79MPG for the same stretch of road, which makes sense. The engine is seeing the same load, even though the battery might not be.