i am running

electric fan
elec intercooler fans
air fuel meter
nitrous solenoids
nitrous bottle heater

seems like the truck drops below 13.5 volts after just a couple dyno pulls

when ever the volts drop during a pull to about 13.0, the mass air starts playing games and the truck goes lean

turn off all the accessories, let the battery charge 15 mins or so

and the volts stay 13.5-14.0

everything is fine with the truck,

i talked to powermaster today and he said almost all late model stuff will get screwy when the volts start to drop.

also talked to one of my good techs at the dealership today, because i keep getting the 1121 code "mass air and tps inconsistent" (this has only been happening since i put on the JLP ram air kit)

he said that from his info, anytime you get below 13.5V it's can play havic with the electrical system

so, i ordered the 200 amp alternator today, hopefully that will cure my issues.

my tech said it is a possibility that the low v's could be causing the maf / tps, i think he said if they get more than a .10 V difference that it will throw the code, it seemed like it came on when i was in like a 25mph zone

i'm wondering if with the accessories, plus the stall, once in a while it will hunt that the rpms drop down and cause the v's to drop

i guess it's also possible that the stock alternator is maybe taking a crap too

any thoughts?

 

Hey,
I don't know about the L, but my family owns an outboard shop. With all the new fuel injected outboards, battery voltage has become critical!!!! Anytime we even install a radio or gps or anything we install twin batterys with it. The computers are very sensitive. I would say, smart move on the high output alt.

 

It really seams like all your problems could lead back to a grounding issue. You sure when the motor was put in they didn't miss a ground somewhere?

 

Beef,

Every fuel injection vehicle is sensative to voltage drop. Ive known alot of mustangs and lightnings that have had this issue and even blown up due to improperly relocating their batterys. You must take the output cable from your altenator (the heavy cable, 4 gauge I belive) an hook that directly to the positive terminal on the battery. Anything that generates electrical power must be hooked right to its storage (the battery) because electricity takes the path of least resistance. If you still have your altenator output wire hooked to your starter selinoid, its going to try and power up the whole vehicle before its stores power in the battery. So during the dyno pull all the power is going through your main fuse panel to power up the vehicle and then half way through the pull the altenator cant keep up with it so it starts to drop the voltage. You need a steady voltage to run a fuel injected vehicle but you also need the battery to supply the amperage to maintain that same steady voltage. If you hook your output supply of your altenator onto the positive terminal of your battery, this way your altenator is only supplying power to the battery and the amperage that is stored in the battery will supply a steady voltage to the rest of the vehicle. If you look at the factory ford setup your altenator is hooked to your starter relay but its only a 1 foot distance from the starter relay to the battery. So the path of the power from the altenator immediatley goes to the battery before it powers up the rest of the vehicle. If you put a battery charger while its on the dyno and making a pull you will see a big difference in your airfuel. which you already found out! This goes for anyone who has relocated their battery. Hope this helps!

Jim@JDM

 

have you considered maybe doing "the big 3" upgrade? Upgrading the size of your alt to batt, etc to maybe some 1/0 guage? Usually guys with big stereo's do this but I dont' see why it wouldn't be helpful in this application...

 

Why not? Can't the alternator supply the needs of the vehicle irrespective of engine speed? Low RPMs = low alt output, High RPMs = high alt output. What is it about a 20-second dyno pull that places demands on the electrical system? Assuming that the A/C, radio, wipers, etc are turned off, and the truck still has the stock mech fan, besides the ignition system, fuel pump, and gauges, what other electricity is being consumed?

After a car is started, you can bypass the battery with a straight wire and it will continue to run, correct? So why do we need the battery to be supplying the electricity?

I'm not saying that you are wrong, I'm just trying to get my head around what you are saying. I am one of those guys with a relocated battery. I need to understand the whats and the whys of your theory.

Thanks

 

hmmnm,

i don't know if you saw my post 2 weeks ago about the maf pegging after we put the 2nd battery in line, now, i'm wondering if the reason it was doing it was because of what you said, and then adding chargin a 2nd battery to the mix,

not sure, but could be

so, i'm wondering now, if my dual battery setup would be fine if i was running from the alt to the 1st battery, then battery 1 to battery 2 and then battery 2 to the starter solenoid?

what are your thoughts?

 

tim, we were logging everything, and i watched the battery volts being irratic, dropping into the 12's, then back up, they were all over the place

and, the tuning changes every time the voltage was below 13.5 was definately noticable

 

I'm not disputing that sagging voltage is causing your tuning problems. I wouldn't know either way, but since you are seeing what you are seeing, and Jim has tuned more engines than he can count, I accept that this is the case. Since the microprocessor-based ECU could probably operate on a 9V transistor battery, it must bad data from the sensors that causes the problem.

I just want more tech on the theorized cause of sagging voltage.

In addition to solving your challenges, which may be related to your dual battery setup, I also want the tech for the rest of us. The whats are rarely good enough for me -- I want the whys!

Blowing my motor from a friggin battery cable would be most uncool.

I am just getting ready to install a Painless alternator relay for the master disconnect. If I am reading Jim's post correctly, that may not be needed if the alt output is run back to the battery.

 

A second battery is just more load on the alternator while the car is running, it's just like anything else, it takes energy to charge it up from the alternator.

I'd get the high output alt for sure.

 

If you run two batteries, adding in an autoswitching isolator to do the charging. Will charge each battery as a seperate unit, allowing the alt to work easier. Less alt load = less lost HP. Or you could put in a manual marine switch and control the use also. Another thing would be to use deep cycle batteries, they have more reserve storage ability. They also hold up better to heavy drain loads. You want to feed the electrical system from the battery to keep a more constant stable voltage. Something you would not get running directly from the alt.The other critical item is >GROUNDING< it is in some cases more critical than the positive ckt. Most functions in the cpu work on grounds as with relays and sending units and sensors.There are even several ground kits made for just this reason. Hope this might help with tracking down your problem. Artie

 

just re-read this, on a basically stock truck, i think it might be able to keep up, i think it's when you started adding a lot of extra accessories that the problem is coming in

waiting to hear from jim

 

most fuel injected units will not run properly on current supplied by
the alternator just for that fact it is a alternator
the current is not a true dc current it is a wave if you look at it on
a scope the battery acts as a storage and a capacitor smoothing out the
feed
all electronics work on dc volts if the voltage is dirty (small oscilations
from bad rectifiers diodes) the become less efficiant
I have had some units that won't even run if a battery charger
is hooked to them because the volts is so dirty
been a while since my last electronis course
if you don't understand ask me I'll see if i can help
mitchykns
ps Tim don't put a wire between batt cables it will result in a
instant smoke show

 

Ohm's Law. When one of the variables (volts, amps, ohms and watts) change, the change effects the others.

The alternator is meant to charge the battery(s) not supply the vehicle loads, that's the job of the battery. In the relocated battery scenario, with the alternator output going to the starter solenoid, the vehicle loads are taking amperage from the alternator before that amperage reaches the batteries as JDM explained. For the battery to supply 12.7 volts (maximum charged 12v battery), 100% of the battery amp capacity must be replaced. Think of the plumbing analogy and you can see that this is true.

 

That's not true actually, a fuel injected vehicle WILL run off the alternator alone. That's why when you do the remote battery setup with a cutoff switch, you have to also run the heavy alternator line to the cutoff as well. If you leave it hooked up, the vehicle will stay running when you throw the cutoff switch.