boost a pump...interesting fuel system facts

tru-boost

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2007 sunlight silver speed3
warning..... ahead is a wall of text. it is good info, but long....

ok i finally got my car back on the road ! the nitrous instal is still incomplete and i have a few bugs to work out....my boost is way high and wont come down !! i have my MBC all the way shut and i still get up to 20psi !! i must have a leak in the boost control hoses somewhere. i just havent checked it out yet...... anyways to the point.....

i installed a kenne bell boost a pump (BAP) to make sure i can get all the fuel i need up to the CDFP. my nitrous is a wet kit so it will be stealing some fuel from in front of the CDFP, thats the whole reason i did this. what i noticed is the way the ecu controls the in-tank fuel pump is rather odd. i remember hearing something in another thread but i thought i would share my findings.
after i hooked up the BAP i went straight to testing it with a volt meter. the install is stupid easy, and i have it set up to activate at 5psi. with the car running at idle (closed loop) the car only sends 10.5 volts to the fuel pump !! i thought that was odd. then when you get on it the voltage jumps to what appears to be full alternator voltage which was about 13.5 volts. those numbers are with the BAP installed but i left the pressure switch off to get "stock" readings. then i jumped the pressure switch to make the BAP active under all conditions to test the voltage adjuster knob. the first thing i noticed was it made the closed loop voltage jump to 12V, up from the original 10.5 . the thing was when i tried cranking the voltage up ...nothing happened. it stayed right at 12V. at first i though i must have wired it wrong or something, but i didnt.for some reason the closed loop voltage was not adjustable. i decided to take it for a ride with the voltage knob cranked all the way up and the boost pressure switch still jumped to make it active. with a buddy in the co-pilot seat holding the volt meter we did some test runs. it would hold that 12 volts solid all through closed loop. as soon as the car went to open loop.....thats when the BAP went into action. now instead of 13.5V i was seeing just under 17.5V !! i thought since the pump used a regulator in the tank it would run a fixed voltage, but it clearly does not. the fact that the BAP only kicks in under open loop is perfecrly fine, thats really the only time it will be needed...WOT while on the spray ! i ended up taking my jumper wire off of the pressure switch and hooking it up how it should be. the car now runs its stock 10.5V during closed loop, unless i go over 5psi...then it jumps to 12V. once i go open loop at over 5psi...its game on. i can make the pump flow as much as i want !! i have it set to hit a mere 14V for everyday use, and i will run it around 16V when the juice is on !! overall i think it is the perfect way to get the extra fuel out of the tank. i think this is an awesome solution for any big turbo/nitrous car.
i hope this info comes in handy for anyone considering this type mod.
 
im not very familiar with the KB BAP but i assume it functions in the same way a Vortech unit does. The vortech "robs" voltage off of a higher volted wire and then applies it to the pump. Knowing this, id be interested to find how you got 17.5 volts when an alternator is regulated to not run any higher than 14.5.....where did the other 3 volts materialize from. Like i said im not familiar with the KB setup so there could be something im missing.......im just curious as i have the votech unit on my cobra.
 
Thats not at all how it works. It doesnt rob power fromany other power source. The BAP simply acts as an adjustable amplifyer. You cut the power wire that runs to the fuel pump. The power then feeds into the BAP where it gets amplified, and goes out to the pump. The same way it works with amplfied subwoofers in a sound system. If that how a vortech works, thats pretty bad. Especially considering lots of alternators dont pull their weight under high load situations.
 
nice u should do a wright up with pics. very nice work bro

i considered it, but it is seriously retarded easy. i really just wanted to share what i found about the way the ecu controls the voltage, and what it does with the BAP installed. anyone who has enough mods to need something like this can install it without issue. the instructions supplied explain it all.
the only tip i can give is this. the positive wire on the FP harness is green/red. the rest is just running the wires ! i have mine mounted in the hatch on top of the wheel well. the plastic trim fits and everything. the only thing exposed is the adjustment knob, which i also mounted in the hatch area.
 

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