94 Volvo 940, trying to break the 27 mpg barrier

[brucepick]

A good mod. Well done!

If you disconnect the alternator - then:
Just be sure to keep that lead acid battery charged up as much as possible via a battery charger. Yes it has xx Amp Hours capacity but the further down you drain it and the more often you do that, the shorter the overall lifespan of the battery. California98Civic had one that died after about a half year of heavy discharge use. He just got a bigger one so he won't have to drain it down so far.

My thread on my EPES project:
http://ecomodder.com/forum/showthrea...highlight=EPES
I had a few additional challenges to deal with due to a 55 mile commute, each way. So my installation is a bit more complex...

[SmellyCat]

I am running with out an alternator. I drove about 40 miles today. the battery had 12.6 volts left in it when I got home tonite. Is there a rule to how low the battery can get before it wont keep the car going? SC

[tjts1]

As voltage drops the ecu will compensate with longer injector PW and afr goes haywire. Not worth it.

[SmellyCat]

Ok tjts1, that makes sense. is there a certain voltage that the afr and pw stay stable.? I had to lookup what they are..just now.

I need to fake out the ecu so all the dash light go Off. Do I need to hook a 2nd battery across the out put wire from the alternator?

if I don't use the deep cycle to start the car. That might be better for it. Is that logical? Sc

[SmellyCat]

Today drove 50miles and started engine. 5 times. With car running , battery read 12.4 volts. What percent charge on the battery is left? sc

[California98Civic]

Actually, what tests here by myself and Sentra-SER have shown is that the warm air intake works with MAP cars and not with MAF cars (the opposite descirbed above). Also, most guys have insisted that its not changes in AFR that result in savings, since the ECU will detect less oxygen and adjust fuel. Rather it is that you will open the throttle further to get the same power, thus reducing losses from the effort to pump air past the throttle body. But at any rate, Sentra-SER showed pretty convincingly that it does not work with a MAF. And I wouldn't argue with anyone who has experience with these Volvo engines. I just know that my MAP equipped car has been running a WAI for a year, the last 14000 miles or so, without trouble from it.

[SmellyCat]

Update, TJTS1 is right. I was squeezing 25 mpg out of this pig with the alternator and 25mpg with out. I am so Bummed. It really seemed like a good Idea. I will try a switch on the Alt hot wire to see if that does anything next. Cheers. SC

[California98Civic]

Originally Posted by SmellyCat

Update, TJTS1 is right. I was squeezing 25 mpg out of this pig with the alternator and 25mpg with out. I am so Bummed. It really seemed like a good Idea. I will try a switch on the Alt hot wire to see if that does anything next. Cheers. SC

Without really controlled ABA testing, you really can't know for sure the results. You'll want weather, road, temp, throttle, speed, and route conditions all to be the same at minimum. Then there is the state of how warm the engine and tires are... the slightest changes in your throttling--imperceptible to the driver--will alter results. I hope by "the hot wire" you don't mean the alt's output wire to the battery... somebody here wrecked an alt that way, fried it, IIRC.

Sorry for the bummer... keep up the efforts... some work some don't, you know? Good luck!

james

[SmellyCat]

Thanks California Civic, A read a bunch of posts and never figured out exactly how to delete the alt correctly. On this Volvo..

One Big hot wires go to Plus battery side and and a 2nd small hot wire goes to the ignition switch.

For the last week I just had the the belt off the alternator. Do you have to disconnect the all the hot wires or just the little hot wire , or just the big hot wire? SC

[brucepick]

I'm not sure why you want to disconnect wires. If you're considering switching the charge function on and off, see my very last paragraph below.

Do you not want the red "Battery/Alt" light glowing on your dash? If so, you could remove the cluster and then remove that one bulb. However that will somewhat compromise your ability to run the alternator, if you ever do want to. On the Volvo 240's we drove for 15 years, that indicator bulb and a few others provided the "exciter" current to the alt's small red wire. If enough of those 4-5 bulbs are dead or removed, the alternator doesn't put out any charge.

A related concern -
If your alt belt is removed, I'd say it doesn't matter what else is going on - that alternator isn't going to put out any current. So it's presenting no mechanical load to the engine. In fact that setup will save your more energy than disabling it electrically, because you're also saving the mechanical effort of spinning the alternator, it's bearing friction, belt friction, etc.

You might not detect the mpg improvement due to all the other factors in play - weather, traffic, etc etc etc. But you're taking a load off the engine. You'll likely notice some increase in power available for acceleration or hill climbing.

Definitely charge your deep cycle battery as often as possible. Daily would be nice. The more time it spends fully charged, the longer it will last. That's the basic behavior of a lead-acid battery. And of course charging it off wall current is the way to go, otherwise you're back to buying gasoline to provide a charge to the battery.