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
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.
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.
Why are you running twin pumps??
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
Quote from: Prof;607245I 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
Quote from: AtomicRex;607252Why 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
Quote from: BlitzBoy;607254Because 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
i meant my relays are mounted in the "boot" area lol
Quote from: BlitzBoy;607510i 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
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
Quote from: lee mills;607519If 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
Quote from: bnaellis;607504Resistor 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
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.
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
Quote from: AtomicRex;607556The 044 pump is capable of delivering >200l/h so I am quite surprised that there is a need to run two pumps.
Its been show on many Rx7s on many dynos around the world as soon as you get near 550bhp + fly and beyond a single stock 044 just cant supply enough fuel to the injectors when on high boost and fuel pressure falls away.
The original Reworx rx7 stripey ran a modified 044 pump to get to 650 bhp, I was going to go this route of the modfied version when I hit the fuel flow problem myself but the cost of the modified 044 was more then two stock 044s put together.
So I have went two stock 044s instead running one per fuel rail on braided fuel lines forgot the size but bigger then stock anways.
There are quite a few high horsepower rx7s running twin pumps in this country at the moment.
I suppose your surprise is due that your car has to run to a certain hp in your class you are competing so is not near these HP levels maybe and will not encounter this problem I suppose.
Also found this, which was what I was eluding to in the earlier post:
http://www.rx7club.com/showthread.php?t=626724
Basically the stock FPR can\'t flow that well and struggles with the flow rate of the pump running at full 12V - hence the series resistor.
You measure voltage at the fuel pump with voltage going via the resistor. you will see a max of 9v, bypass the resistor and you will see a max of 12v.
I don\'t have a stock fuel pressure regulator so whatever the limitation of a stock one is doesn\'t affect my setup. But what I am perfectly sure of is the electrical setup of an fd\'s fuel pump circuitry.
On a stock fd pump they will fail sooner rather than later running constant 12volts, plus it does heat up the fuel more than necessary at idle and low load if it was to see 12 volts at all times, hence the reason why Mazda as do many other car manufacturers have fuel pump resistors.
My concern with my setup is not that I will burn out the 044 pumps, but that the 044\'s are best run with atleast 45 psi and I did not want to be running too rich at idle & low load, it would be preferred if during idle and low load I could run less voltage to the pumps, as the apexi pfc does not have the same granularity as Blitzboys motec for trimming fuel etc.
The second reason was I did not want my fuel to be preheated by two intank 044\'s running at 12 volts at all times.
rgds
Brian
Quote from: Prof;607576Also found this, which was what I was eluding to in the earlier post:
http://www.rx7club.com/showthread.php?t=626724
Basically the stock FPR can\'t flow that well and struggles with the flow rate of the pump running at full 12V - hence the series resistor.
I think you misread the thread. a stock fpr my struggle with an uprated fuel pump and cause excessive fuel line pressure at low load and idle. But that\'s nothing to do with runninga resistor.
rgds
Brian
Quote from: AtomicRex;607556I\'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.
My car won\'t be used for race only hence the requirement to to have variable voltage as a stock fd would.
I have not made up my mind yet on fuel line size but I am thinking 2 x -8 lines from pump to a y connector with single -8 onwards, and -6 back to fuel tank.
rgds
Brian
Still learning here but I would have thought that the ecu would be able to control the fuel flow via the injectors at idle and slow running via its map? Then with an aftermarket fpr bleed off any access pressure back to the tank.
Also just a thought but for those who are running high flow pumps or twin pumps how about using 2 of the 3 FD\'s hard lines for increased capacity and some Y connectors and do away with the emissions line?
Quote from: Spartacus;607685Also just a thought but for those who are running high flow pumps or twin pumps how about using 2 of the 3 FD\'s hard lines for increased capacity and some Y connectors and do away with the emissions line?
In my original config we did use this idea of using the the 2 hardlines to feed the primary and secondary rail individually (no Y connectors) and using the emissions line as the return, but decided to get rid of this in favor of bigger bore braided lines.
One thing to note then. If you are going ahead with retaining the resistor, it will be the wrong value, as you have 2 pumps instead of the one, and they are also different and draw different current to the stock FD / FC ones. This means the resistor value needs to be changed so that the same voltage conditions / fuel flow exist with the twin pump arrangement.
Having said that, why not switch one of the pumps off using a relay in parallel with the resistor relay, as you don\'t need 2 fuel pumps on at idle / low load crusing ? :driving
Quote from: Prof;607697One thing to note then. If you are going ahead with retaining the resistor, it will be the wrong value, as you have 2 pumps instead of the one, and they are also different and draw different current to the stock FD / FC ones. This means the resistor value needs to be changed so that the same voltage conditions / fuel flow exist with the twin pump arrangement.
Having said that, why not switch one of the pumps off using a relay in parallel with the resistor relay, as you don\'t need 2 fuel pumps on at idle / low load crusing ? :driving
Or 2 stock resistors?
having resisters in the wiring is just something else to wrong Brian. Not worth IMO, play with the pressures, injectors and tuning to get it right, it can be done.
What he said:yes
Fair point guy\'s about something else to go wrong but then on the other hand if the resistor did go wrong that would (i think) only mean the pumps would always see full voltage rather than see no voltage which could mean bye bye engine. If I had a better ecu it would make life easier but I can\'t be bothered now, just want to get the car back up and running after so longa time.
rgds
Brian
`Hi Brian,
I am running an additional 044 with an additional fd resistor, to help reduce airating the fuel and unnecassary heating as you said.
I am running a stock in tank pump, feeding a swirl pot with an 044.
I used a pair of new 40A 12volt relays topower the new 044, both relays wired in parallel, the first wired with the resistor in series which is switched on from the oem fuel pump relay, the second switched by the power fc using the same speed signal used in the oem system,it also helps quieten down the pump while cruising. I agree peoples comments about one more thing to go wrong though.