Fuel Pump Resistor

[bnaellis]

If i\'m running twin bosch pumps in tank, can still run them via the stock fuel pump resistor so the pumps only see low voltage at idle and cruising and full voltage under load, the same as the stock fuelp pump?
Or would I need a bigger better aftermarket one? and would I then need one for each pump. Opinions welcomed.
Nothing too techy though I just done 20hr shift at work and my head hurts.

rgds

Brian

[Spartacus]

If I were you I\'d dump the resistor and the old Mazda relays and use a new relay put close to the pumps i.e. just behind the boot side panel supplied direct from the battery (via a fuse).

This way you eliminate a lot of connections and 15 yr old relays etc so the pumps get a full battery voltage. One pump takes quite a bit of current so having 2 supplied by the old wiring and relays is asking for problems.
I did the same when I swapped in my LS1 V8.

[Prof]

I read somewhere that the main reason for the resistor was to limit fuel pressure under idle and lo load conditions by dropping pump output, as the FPR\'s used by Mazda weren\'t really good at flowing that much fuel back to the return fuel line when hardly any was going to the injectors.
 
So if you\'re using an aftermarket FPR, and no longer have the stock one in the fuel rail, then you don\'t need the resistor and can run the full 12V all the time.

[AtomicRex]

Why are you running twin pumps??

[BlitzBoy]

Because he is running a sh!t load of power lol
I run Twin pumps as well, I maxed out a single Bosch at 440 at wheels, hence why we need two.

Brian, I use seperate new relays for each pump no resistors with new wiring, relays in the boost area

[bnaellis]

I read somewhere that the main reason for the resistor was to limit fuel pressure under idle and lo load conditions by dropping pump output, as the FPR\'s used by Mazda weren\'t really good at flowing that much fuel back to the return fuel line when hardly any was going to the injectors.
 
So if you\'re using an aftermarket FPR, and no longer have the stock one in the fuel rail, then you don\'t need the resistor and can run the full 12V all the time.

Resistor doesn\'t affect fuel pressure it limits the voltage to the fuel pump to
9 volt during idle and low load conditions so the pump lives longer and fuel is cooler.


rgds

Brian

[bnaellis]

Why are you running twin pumps??

1.9 bar of boost needs a lot of fuel. I\'d rather go overkill as going underkill is what killed my last engine.


rgds
Brian

[bnaellis]

Because he is running a sh!t load of power lol
I run Twin pumps as well, I maxed out a single Bosch at 440 at wheels, hence why we need two.

Brian, I use seperate new relays for each pump no resistors with new wiring, relays in the boost area

My plan was not to use stock wiring, I plan on running new wires to the battery via new relays, but also try and wire in a fuel pump resistor inline so it performs the same function, by dropping voltage to the 044\'s during startup idle and low load, which I do a lot of in London.
Mark what do you mean relays in the boost area?
Cheers for response gents

rgds
Brian

[BlitzBoy]

i meant my relays are mounted in the "boot" area lol

[bnaellis]

i meant my relays are mounted in the "boot" area lol

lol there\'s me thinking it\'s some new technical thing having relays in the boost area:driving
I guess you have more options on the motec to trim fuel at idle and low load compared to the apexi, but I don\'t know enough about the 044\'s whether they will burn out from running at full voltage all the time.

rgds
Brian

[lee mills]

If you havent already bought this set up why not go for the aeromotive pump with a pump speed controller like this
http://cgi.ebay.com/ebaymotors/NEW-AEROMOTIVE-PUMP-SPEED-CONTROLLER-16306_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1683Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a0Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem250398840475QQitemZ250398840475QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

[bnaellis]

If you havent already bought this set up why not go for the aeromotive pump with a pump speed controller like this
http://cgi.ebay.com/ebaymotors/NEW-AEROMOTIVE-PUMP-SPEED-CONTROLLER-16306_W0QQcmdZViewItemQQ_trkparmsZ72Q3a1683Q7c66Q3a2Q7c65Q3a12Q7c39Q3a1Q7c240Q3a1318Q7c301Q3a0Q7c293Q3a1Q7c294Q3a50QQ_trksidZp3286Q2ec0Q2em14QQhashZitem250398840475QQitemZ250398840475QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories

Bugger i\'m at work and can\'t view pics but it the controller sounds like what I want. I do however already have the fuel pump kit which is a quality, just need to buy fuel pumps, pickup socks, wiring, relays, fuel filter and fuel lines.
I\'m sure if I think hard enough I can find a way to have resistors inline that are relay driven, so when the relay flips the resistors are bypassed and full voltage goes to the pumps. Otherwise i\'ll be in traffic and have my fuel boiling and bubbling in the back.:2Confused


rgds

Brian

[Spartacus]

Resistor doesn\'t affect fuel pressure it limits the voltage to the fuel pump to
9 volt during idle and low load conditions so the pump lives longer and fuel is cooler.


rgds

Brian

I think I would have to respectfully disagree with what you are saying here. After all the pump is just an electric motor which when you apply more or less voltage it will run at different speeds and deliver different amounts of flow.

Fuel pumps are designed to work at full voltage so there should be no reason why they would burn out more or less than any other fuel pump in any other car. I can’t see the benefit of the resistor in the circuit as I\'m guessing that the fpr just bleeds off any extra fuel to the tank when not required.

Just found this which might help?
http://www.stealth316.com/2-fuelpumpguide.htm

[AtomicRex]

I\'m with Sparticus on this one. Ive not seen so far in any race application anyone regulating the voltage of the fuel pump. They are designed, and manufactured to be used at 12v and so should be run accordingly.
 
I am all for pushing the envelop but usually the race fraternity is a good indication about what works and what doesn\'t.  This is something that is evidential with Brakes...you never see a GT car with a 16 pot calliper, most are running 4, 6 and starting to run 8\'s.
 
As above, the fuel pump is meant to deliver the fuel, any regulating of pressure should be done via the FPR.
 
With regards to running two pumps...what size fuel lines do people run?
 
The 044 pump is capable of delivering >200l/h so I am quite surprised that there is a need to run two pumps.

[Prof]

There is quite a lot of useful info on this thread (I know it\'s for Mitsubishi 3000, but is none the less applicable) with a lot of research and comparisons on different pumps and their ability to deliver fuel flow at different voltages / pressures.
 
http://www.stealth316.com/2-fuelpumpguide.htm
 
With regard to running the pump at a lower voltage to reduce heating effect - the load on the pump will define how hot it gets. Current in the pump will increase as it has more work to do. The dropper resistor is not in the circuit when the pump is working at it\'s hardest to maintain flow. That being said, the fuel will act as an excellent coolant, and will dissipate a lot of the heat in the pump along the fuel supply line which is mostly outside the car.
 
Oops - just noticed Spartacus put the same link up ! - Doh