Increase Idle Speed Help

I've tried just about everything to bump idle speed on my 3rd gen, so that I can spin my alternator faster and generate more power to charge Lifepo4 batteries.

- VFTuner (via OTT guys) were able to bump the idle speed when the truck is in gear and stopped.
- They were NOT able to change the idle speed in VFTuner when the truck is in P or N. There is a setting but it has no effect, and the truck is stuck at 600. They said it is a bug in the VFTuner software. There's a ticket up for it but it's been a few months with no movement from the developer.
- I am running a 1.75" pulley on my alternator, which is the smallest out there and likely already pushing the limit. 2" is stock. This is a DC Power Engineering alternator.

I need the idle up at 800 in N to charge my battery bank. I've looked into:

- Tricking the throttle sensor (looks hard because it has two different pots for redundancy)
- Programming the ECU with an OBD-II device in runtime (can't find anyone else that has done this, so it might be possible but it seems near impossible to find the right CAN message to send)
- Increasing the size of the crank pulley (not sure if this is possible or safe so haven't explored much further)
- Aux Alternator with a separate pulley - would need a lot of work to cram something in there. Might end up going with this if I can't get an easier fix.

So, tuner geniuses - what options do I have for bumping the RPM?

 

Lean a properly weighted rock on the gas pedal.

As an aside, what is the larger problem you are trying to solve? Using a 3.5L V6 automobile engine to charge batteries seems non-optimal. I suspect there is a better solution to your problem than raising the idle rpm of your truck engine.

 

Heavy equipment vehicles like buses, highway trucks, etc have fist idle switches which bumps the idle up to 1100 rpm to get the air compressor pumping faster to build air in the system quicker.
Maybe something like that is what you're looking for, but programmed to the idle speed you specified.

 

Without them being able to change the programming I think your only option is a bigger or rewound alternator or:

 

What are the spec to charge the battery? 14.6V?

 

How many amps do you need to pull?

Might contact a few companies to see the specs on their idle output and find a lower RPM, high output option.

Looks like the DCPower alt. doesn't even turn on until 1230rpm


Pure Power/TAE might make one for the 3rd Gen that turns on a lower RPMs (596 RPM for the 2nd Gen)


PowerBastard claims 125 amps @ idle and 250 amps @ 1200 RPMs

 

I am running DCDC converters, so it doesn’t matter what the voltage is. I have the truck tuned for AGM, so the voltage is already higher to charge that.

keep in mind that these are alternator shaft speeds, not crank speeds. The crank has a larger pulley.

 

Maybe I'm not clear, but you've replaced your battery with one that had higher charge requirements or do you have additional batteries for other accessories?

If we're just talking about a single battery, wouldn't simply driving the truck keep the battery topped off or are you spending many hours idling?

 

True - I was just wondering if the DC power is needing higher RPMs to activate than other brands.

Might still be worth contacting a few other companies to see if a custom low-RPM, high-output alternator would be the easiest solution for you. If anything, your smaller pulley would be a benefit for any alternator, especially if the "stock" out of the box specs are better than than DC Power. From the sound of it, you've tried many different/high cost methods without the result you're wanting, so what's another 20 minutes on the phone or sending a few emails?

My 2nd Gen warm idle (in neutral) sits around 860 rpm. I'm running group 31 AGM battery and installed the Ford one-way diode to bump output voltage up (14.7v).

 

We are talking about house batteries here. I live in my Tacoma. I have 4x 100Ah battle born batteries and am trying to run 4x Victron Orion 30A 12V to 12V to keep the bank charged. I’m running big loads like a high performance Starlink dish and I’m cooking with electricity on induction.

 

All of my wiring from the front to the back is 1/0. Splits off into all the chargers on a bus bar. Here’s a pic of it. Wire is quality but I did this on the road so wire management is not the best.

 

Would it not be more efficient to use a portable generator? Isn’t that typically how RV generate power when off the power grid?

I realize it would take up space and likely require a fuel can, but the cost savings in fuel and wear and tear on your truck engine could outweigh it.

 

There is a complex Idle Speed Control logic in P and N similar to knock correction one.
There are no other way to write something to ecu via obd2.
You may trick the coolant temp sensor to read a lower temp to fool the idle speed control. But I suspect the aftermath of doing it and tinkering with the throttle control will cost you more than a pedal holder from Amazon

 

yes, I’m going to every effort to avoid that because it’s big, messy, and loud. The engine is only one of those.

 

Smaller pulley on alternator instead of bumping up the idle?

 

Like I said, I’m already running the smallest pulley I could find. 1.75 inches. Stock is about 2 inches. Next thing would be a bigger crank pulley but that’s custom work.

I wonder if there’s a gearbox solution?

 

it defiantly sounds like a hassle. I'd think it would be much easier to find some type of turnbuckle or threaded rod to gradually push on the gas pedal. Think: shower curtain rod, thread it out to make it longer and apply pressure. From there you could make marks on the rod and mounting positions, to get you back in place and close, then just fine tune with a turn.

 

I can't take no for an answer... so I figured it out with some help from TIS



AC1 is a signal to the ECU to tell it the air compressor is running for the AC. ACT is the feedback signal from the engine. If you ground AC1, the engine speeds up to about 900 rpm (just looking at the gauge) and the truck won't let the speed go under 750rpm even with all of my extra loads on.




I believe the AC1 signal is an open collector output from the AC amplifier ECU. I ran a 120 ohm resistor to ground just in case.





I haven't done the permanent wire modification yet, I was just sticking a resistor in the back side of the connectors. I'll post pics when I finish the mod. I plan to put a switch that controls 2/4 of my chargers plus this.

 

My Victron dashboard, for anyone interested: