Effects of high amp alternators on the GP system

Peroni · Oct 4, 2011

Ever since I upgraded to a higher amp alternator I've had issues with the glow plugs cycling when it's cold out. I'm told this is a feature of the TDE1 programming to protect the gp system from too much amperage.

How do the ambulance vehicles deal with this with their high output alternators?

Right now if it's under 55° I have to turn the lights on, radio and put the blower on to keep the plugs from cycling on and off and it's annoying.

Can this feature be bypassed with tuning? Can I put a resistor in the feed line to gp relay?

Tom S · Oct 4, 2011

Very interesting post. I do not see it being likely of doing anything in the feed to the glowplugs to add resistance when you have 8 plugs that are already generating enough heat to get red hot. I would like to know more about how it cycles the plugs. I am not aware of that being an option in the tuning software to tweak that like there is for cold idle for instance.

JCart · Oct 5, 2011

Peroni,

How do you know your GP system is coming on? Does the dash light come on? Not doubting just wondering how you tell. I have put on a Leece-Neville 200 amp unit and have not had this happen that I am aware of. My PCM is not TDE1 though its a manual out of my '96 NAW4 with Tony Wildman tunes.

Not sure on the programming it out....guess you could always put a switch in line to the GP activation post to interrupt signal and in this way manage the signal this way?

jrc

Tom S · Oct 5, 2011

NAW4 is an auto code.

bluedge8 · Oct 5, 2011

Is it doing it while waiting and the motor not running?, if so the amperage of the alt wouldnt matter, but possibly the wiring of the alt or resting battery voltage

JCart · Oct 6, 2011

Tom S said:
NAW4 is an auto code.

Heh heh 'K how but ALF4 then Tom? Just had a well beyond middle age moment there....sorry Peroni... it's ALF4 with Wildman tunes and ZF-5 both out of my 96 into the sig truck.

jrc

PsRumors · Oct 6, 2011

The glow plugs are only going to draw what they are capable of drawing. You cannot force the GP system to pull more amps with a higher amp alternator. But if your alernator is providing to high a voltage that could create a problem.

Think about a lightbulb at 100 watts. That light bulb only pulls .83 amps. Typically a light will be on a 15 AMP circuit at 120 volts. The light bulb only pulls what it needs. Of course if you change the circuit to 240 volts the bulb will blow as soon as you turn it on.

The GPs opperate on the same way.

F-127 · Oct 6, 2011

There is in fact a function in programming that handles glow plug duty cycle in regards to battery voltage. From 0-14.01 volts, duty cycle is 99%, this then drops 0% duty cycle at 14.91V and higher. I can only speak for TDE1 though, I don't know if that is the same values for other PCMs. It can be changed in tuning, but if it was programmed that way, there is probably a reason. As you've heard, it was likely to prevent GP burnout.

Gearhead · Oct 6, 2011

Peroni said:
Ever since I upgraded to a higher amp alternator I've had issues with the glow plugs cycling when it's cold out. I'm told this is a feature of the TDE1 programming to protect the gp system from too much amperage.

How do the ambulance vehicles deal with this with their high output alternators?

Right now if it's under 55° I have to turn the lights on, radio and put the blower on to keep the plugs from cycling on and off and it's annoying.

Can this feature be bypassed with tuning? Can I put a resistor in the feed line to gp relay?

Running or not running?

Tom S · Oct 7, 2011

F-127 said:
There is in fact a function in programming that handles glow plug duty cycle in regards to battery voltage. From 0-14.01 volts, duty cycle is 99%, this then drops 0% duty cycle at 14.91V and higher. I can only speak for TDE1 though, I don't know if that is the same values for other PCMs. It can be changed in tuning, but if it was programmed that way, there is probably a reason. As you've heard, it was likely to prevent GP burnout.

Interesting info welcome to the OBS section. Matt do you have any input on this.

Gearhead · Oct 7, 2011

Tom S said:
Interesting info welcome to the OBS section. Matt do you have any input on this.

Yes at 14v the duty cycle starts to drop out.... it sounds like the voltage regulator needs to be tweaked on said alternator... 13.8 is all it should ever charge anyway.

Peroni · Oct 7, 2011

Thanks for the response everyone. This happens while running. Just as F-127 says as soon as my volts creep up to 14.1 the plugs kick out then come back on. This repeats until I either turn on the lights or the pcm determines the plugs have been on long enough and turns them off. I'm running a DC Electrical Engineering 190amp alternator, my system generally hangs between 14.1 to 14.5 volts. I don't remember what it was before my stock alternator died.

cowboy_dan · Oct 7, 2011

There is a table in the PCM of GP duty cycle (On/off basically) vs system voltage. It kicks the GP off if the system voltage gets above the set point. I remember seeing this somewhere on a site before, just don't remember where.

FWIW, I have the same issue on my truck, and it's alternator is a stock replacement as far as I know.

Tom S · Oct 12, 2011

cowboy_dan said:
There is a table in the PCM of GP duty cycle (On/off basically) vs system voltage. It kicks the GP off if the system voltage gets above the set point. I remember seeing this somewhere on a site before, just don't remember where.

FWIW, I have the same issue on my truck, and it's alternator is a stock replacement as far as I know.

http://forum.gopowerhungry.com/1994-1997-7-3l-power-stroke-diesel/5426-glow-plug-relay-cycles.html

Peroni · Oct 12, 2011

So what is the consensus? Do I call DC Power and ask if the alternator regulator can be adjusted or do I call my tuner and ask if he can play with the duty cycle?

PsRumors · Oct 12, 2011

What is so wrong about the plugs cycling?

What is the voltage when they are cycling?

Peroni · Oct 12, 2011

What is so wrong about the plugs cycling?

It's annoying as all hell, it didn't do it before the alternator upgrade and probably isn't that great for the gpr.

What is the voltage when they are cycling?

14 volts, they are rock steady on until then.

Tom S · Oct 12, 2011

I would be tempted to have the duty cycle tweaked just a hair. Do you think maybe you have a couple of plugs that are not working which leads to the voltage coming across the line to where it cycles.

cowboy_dan · Oct 12, 2011

Keep in mind that idle speed will also affect the voltage. I have a program that idles less than a hundred RPM faster than the others. Can't hear the difference, and can't tell the difference on the tach, but the voltage is slightly higher in that tune than the others.
Between the HO alternator and a tad faster idle, that could be what is letting the voltage come up high enough to cause this.

So you might want to stick AE on it and see where it is idling, then call your tuner and see if 1) that is the correct idle speed, and 2) can they lower the idle or raise the kick-off voltage.

You might want to see if you can adjust the regulator down a touch, though. If the glow plugs get too hot, you could damage them. Higher system voltage for same resistance = higher current = hotter plugs. How much current does that take? I dunno. Figure EGTs can be sustained in the 1000-1200 deg range, and I haven't seen anybody claim that is bad for the glow plugs.
Then again, the temp is the cylinder is cyclic with the (relatively) cool intake air coming in, then the compression and power strokes creating heat, then the exhaust stroke relieving some of that heat. So maybe the GP tips don't get as hot with the engine running and pulling hard as they do sitting there preheating on a cold morning. It would be an interesting heat transfer study.

Looking at the attached chart, I'd say that 1000-1200 deg is about the standard temp for a glow plug.