Daox's 1997 Paseo Build Thread

[Daox]

For a while now, I really haven't been using the scangauge to track MPG. The problem I have is that when I have a short pulse followed by engine off coasting, the scangauge shuts off and throws my numbers off. It also takes the computer a long time to reboot when I switch back to run. This further throws off my numbers. Anyway, Darin seems to think that this is hurting my mpg. So, he finally convinced me to install my mpguino I've had for a few weeks now.

So, I popped off the glove box panel and went to work. The wonderful thing about the mpguino is you only have to hook up 4 wires, and two of them are power. That leaves you with just two wires to find in the mess, and with a wiring diagram or ECU pinout, its pretty easy. For my setup, I didn't cut any wires. I used an exacto knife to strip off some insulation and wound the mpguino wires around that area.





I still don't have an enclosure for it, but that'll come along shortly. I'm also still using the scangauge to measure load, and coolant temp and stuff. Here is the current dash setup.

[Daox]

Next task, alternator disable. If you read the boards you've probably seen this coming. I decided to go the route of killing the alternator field wire with a switch (for now). This seems to work great. Its a very low current wire instead of the huge alternator cable to the battery, so small electronic components work just fine.

First, I found out where the alternator field wire enters the cabin. I really didn't want to be running more wires from the engine bay back into the cabin if I could find one that was already inside. The pin is pulled out of the connector in this picture because I tested the setup this way.





Next, I cut the wire, and soldered in another length of wire to go to a switch.





With it all soldered up, things went back together.





On the other end of the wires, I added ring connectors.





I then found a switch I had laying around, tapped the terminals for a #6-32 screw, and bolted the rings down to the switch. The reason I did things this way, was if the switch ever fails on me, I should be able to just unscrew the leads and connect them together on another leg of the switch.





Last, but critically important if you're going to disable an alternator for anything more than a short duration is the deep cycle battery. This battery I got from the same guy who gave me the chassis for my mower. It is a group 24 battery (70-85 Ah), and just fits in the engine bay. I had to finagle it around so it wouldn't hit the hood. It had been sitting for 2 years or so. It seems to hold a charge alright. We'll see how it holds up over time.




I took it for a drive earlier today with the wife. We went about 15 miles with the connector like you see in the first picture. The car ran great, but the voltage was dropping down to 11.9V by the end of the trip. I'm hoping the battery just needs to be exercised a bit.

Here is a shoddy video I took when I was all done with it. You can't really see the voltage numbers on the scangauge, but you can certainly hear and see the difference in RPM.

http://www.youtube.com/watch?v=-ldSspTgIYY

[Tango Charlie]

Very nice! (love the pics... )
Where did you mount the switch then? And what is the strategy for when to switch the alternator off?

[Daox]

The switch is currently mounted to... air. I threw it in the glove box. I'd like to setup a relay so the brake light activates the alternator for a form of regenerative braking.

The strategy for using the switch is to not use it. I would like to have it off all the time. The battery (if its in good shape) should last me to work and back. I rarely take it on long trips, but if I did, I would probably turn the alternator on for the trip.

[Jetta90GL]

I want to do this on my jetta, umm .. once I get it running. I ran the car with out an alternator belt until I got around to installing the new one. I have two 5 watt solar panels in the back window that helped it charge. I leave it parked in the airport parking lot for weeks at a time, so it has plenty of time to soak up some free power.

[McTimson]

I'm sure it's been mentioned before, but are there any negative effects to flipping the switch on while you're driving? Besides the engine load, like is there any possible damage to the alternator?

This seems like a real easy mod to do, definitely looking forward to results.

[blownb310]

Originally Posted by Daox

The strategy for using the switch is to not use it. I would like to have it off all the time.

So you'll be charging your deep cycle battery at home with a portable charger then? Hmm, I like the solar charger idea too.

[Daox]

I don't think there is any chance to damage the alternator by disabling the field. I've read here that if you disconnect the main lead from the alternator to the battery there are possible problems if you do not disable the field as well. The only negative is if I ever have to flick the switch after running the battery down. In this case, I'll likely take a fair penalty in the mpg department as the alternator is going to be pumping out as much amperage as possible to recharge the battery.

[Daox]

Yeah, for now I'll just be using a normal charger. I like the idea of solar too, but they really just don't put out enough power to charge the battery if I had to drive it two days in a row.

[Daox]

I just got the car off the charger for the night. The kill-a-watt recorded .48 kWh used. When I put the battery on the charger, the charger said the battery was still at 70%. So, I have tons of capacity left in the battery which is great! I think it can be safely said that my charger is fairly inefficient since the total capacity of the battery is only .9 kWh. Anyway, today's commute was pretty bad compared to normal (accident on the way home had things really backed up), so this is about as bad as it should get.