AGM BATTERY CHARGING - ALTERNATOR VOLTAGE BOOSTER

Save yourself the grief and just replace it now if you already have the AGM. I ran mine for nearly eight months before I did anything with the charging voltage piece. I didn't even know and I've been running AGMs for years.

 

Man that's slick

 

Adding these to the OP

 

Hey guys, I had to pull this from my truck​

Some sensors and maps in the ECM are calibrated to voltage, this will throw off maps in your tune! Injector Dead Time, Ignition Dwell Time and anything else calibrated to voltage- ultimately affecting your fuel metering (mpg, among other things). Boosted guys are really affected by this. I tuned my COPs to .2v below saturation, this had me running them in saturation ever since this mod

Edit:
Warning added to OP

The circuit does not include the ECM, the ECM reads the actual voltage.

 

Dang, I guess we can't have our cake and eat it too

 

Well, you can, you just can't be running an aggressive tune to compensate for more aggressive modifications.

 

what about stock N/A trucks?

 

It throws everyone’s computers off.

Edit:
The circuit does not include the ECM, the ECM reads the actual voltage.

 

It does but there's enough flexibility in a non-flashed ECU that it should more than adjust for it. When you're running aggressive tunes, you're getting into a very narrow set of criteria you need to hit for maximum potential.

 

What if you put another diode into the power for the ECM to drop the voltage back down?

Edit: Don’t know if the diode will handle the load of the ECM.

 

It's a 20 amp (EFI) and 15 amp (IGN) fuses, I'm sure it's possible to get that in a diode rating.

 

I don't think you guys are getting what I'm saying.
The ECM sees the spoofed voltage, EVERYTHING is operating on the actual higher voltage.

At a given load, let's say the ECM tells the injectors to open for 2.5ms at 13.8v and 2.3ms at 14.2v (injector dead time is smaller as voltage increases) and the ECM sees 13.8 but the injector has 14.2 volts at it, the ECM will tell the injector to open for 2.5ms but should be 2.3ms- you just lost fuel economy. The same can be said about every sensor and electrical metering thingy throughout the vehicle. Not true, I forgot about 5v sensors, but all electrical components supplied power by the alternator.

Edit:
The circuit does not include the ECM, the ECM reads the actual voltage.

 

So the ECM is not smart enough to compensate for it if it also sees 14.2 volts? I guess I don't understand why it would be an issue and how much is affected. I'd think most of those sensors are design to operate over a wide range that the vehicle would be capable of producing.

 

Seems like I would need to hold my foot off the throttle about 9%.

 

Never!

 

I'm not saying you're wrong by any means and i understand what you are saying about the dwell times on injectors and other sensors. But I have had HPTuners for a while and did the Ford diode after the tune. I noticed no MPG difference before or after the diode or any other oddities. I think we would need to see someone with HPTuners should do a datalog before and after the diode change to see if these findings are accurate.

I agree with others that the ECM (stock or HPT) would correct for the voltage increase. Specifically regarding air/fuel ratios.

 

It’s outputs are based on what it senses, absolutely in agreement.
Maybe @JustDSM can comment

 

The stock ECU has voltage compensation tables which will account for voltage swings. All of the 5volt sensors are on a regulated power supply from the ECU which would be unaffected and still report consistently independent of the battery/charging voltage.

 

When you think about it this has to be the case, or else a dying battery would potentially crater an engine even on a stock tune.

 

True but doesn't apply to the COPs or fuel injectors, my main concern being accurate fuel metering and not burning up COPs.