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View Full Version : Voltage Increase Does NOT Assist BAP Fuel Delivery



JoeBoomz
07-09-2012, 11:14 PM
Recently I ran some tests to see if increasing the Marauder's voltage could have a positive effect on the BAP and fuel system (and at the same time, the output of the stereo amplifiers).

Car audio components are usually rated at battery voltage (~12 volts) and at operating voltage (~14 volts). Some enthusiasts will also increase the voltage further to get more power from their car audio systems.

Over-volting electronics is a technique commonly employed across many fields. The Boost-A-Pump actually does exactly this - it boosts the input voltage to the car's Fuel Pump Driver Module and then to the fuel pump.

One area that I have much experience in is the computer world - if your CPU cooler can handle the extra heat, throwing some extra voltage at the processor will usually increase your overclocking headroom (with little or no detriment to its lifespan if you keep it cooled properly).

Let me put my geek hat on here to demonstrate the overclock on the computer I am currently typing this on:
http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/CPU-Z.PNG
Stock speed on this CPU is 3.3GHz - look here I am running happily at 4.3GHz! The stock voltage for the chip is 1.2V and the overclock was done easily with an extra 0.1V.


Anyway, so I figured, let's try this technique on the Marauder; I know the car's electronics are already designed to handle voltage variations because of spikes and droops in the current from the alternator.

So here's what I did; in the car's tune you are able to specify the output voltage of the alternator based on the operating battery temperature.

Here are the stock values:
http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/Voltage%20Setpoint.PNG

Let's bring them up a bit:
http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/Voltage%20Setpoint%2015V.PNG


And verify that the setting changed after reprogramming the car and firing it up:
http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/IMG_2128.JPG



So I ran the car, drove it daily for an hour for about a week, testing to ensure everything worked properly. There was no noticeable difference in performance (or stereo output!). So after I was sure the ECU had a good fuel voltage table built, I generated a datalog:


BAP WITH KNOB AT 100% AT CAR STOCK VOLTAGES:

http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20Duty%20Cycle%202.PNG

http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20Rail%20Pressure%202.PN G

http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20STFT%202.PNG


BAP WITH KNOB AT 100% AT 15V:
http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20Duty%20Cycle%203%2015V .PNG

Notice here that some of my duty cycle values are actually higher than what I had with the stock voltage in place!


http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20Rail%20Pressure%203%20 15V.PNG

http://images.ioncross.com/mercurymarauder.net/07-09-2012-BAP%20Wiring%20Logs/AFTER%20STFT%203%2015V.PNG


There's a lot of data there to look at, but long story short is that there seemed to be little gain to be made in increasing the voltage to the BAP.
This tweak likely just resulted in the BAP working less hard (the BAP increased the voltage less than it would have at the stock car voltage as it had a higher input voltage to start with).


Nice try, but no dice!

babbage
07-10-2012, 06:02 AM
Take the BAP off and it would have worked. Nice writeup! I usually overclock all my systems a bit too. What are you running for an alternator?

JoeBoomz
07-10-2012, 10:09 AM
Stock alternator for now, car has low miles and its keeping up great to my needs.

Now you have me curious - can this method be used in place of a BAP for lower horsepower applications to save buying the BAP? :)

Taemian
07-10-2012, 10:26 AM
Great write up with data to show your progress. Sweeet!

jon5212
07-13-2012, 11:38 AM
I'm not seeing the need for a boost a pump. I'm more familiar with the LSX GM's, a lot of guys run 255 LPH or 400 LPH in tanks with no boost a pump.
There's several guys who just have twin 255 LPH fuel pumps and they are running big single turbos in the 700-900 RWHP range.