OEM fuel pump is a great pump, it just needs re-wiring?
05-03-02, 09:09 AM
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OEM fuel pump is a great pump, it just needs re-wiring?
Anyone here re-wired their OEM fuel pump?
I am having my PowerFC tuned by a rotary shop in New Zealand and they are sending me a 1.2 bar map they have been using for years on their FD with a stock ifuel system running 98 octane.
I asked the guy how they managed this, and he told me about wiring the fuel pump directly from the battery. He says that Mazda's engineers in an attempt to keep noise down, wired the pump very strangely, and in turn it only receives maybe 2-4v on the line. By wiring it directly with a circuit breaker and relay, the pump will recieve the full 12-13.5v and will actually be a great pump?
Has anyone here tried this?
I am having my PowerFC tuned by a rotary shop in New Zealand and they are sending me a 1.2 bar map they have been using for years on their FD with a stock ifuel system running 98 octane.
I asked the guy how they managed this, and he told me about wiring the fuel pump directly from the battery. He says that Mazda's engineers in an attempt to keep noise down, wired the pump very strangely, and in turn it only receives maybe 2-4v on the line. By wiring it directly with a circuit breaker and relay, the pump will recieve the full 12-13.5v and will actually be a great pump?
Has anyone here tried this?
Last edited by Pressurized; 05-03-02 at 10:54 AM.
05-03-02, 10:32 AM
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Bypass fuel pump resistor?
It sounds like they bypassed the fuel pump resistor. This will only put stress on the pump, and you will just keep pumping gas from tank to engine bay to tank at high flow. The Ecu controls the Fuel pump relay that shorts the resistor at high demand, so you normally are in bypass at high load but a low load the fuel pump can relax a bit. It shouldn't make any difference to absolute flow rates from stock pump. IMHO
05-03-02, 10:36 AM
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sounds similar to what the DSM guys have been doing for years.... rewiring to eliminate the current drop . they run a seporate relay and like 12 gauge wire wich is overkill
tests show in high load withe the current not falling they get like 15% more flow
tests show in high load withe the current not falling they get like 15% more flow
05-03-02, 10:48 AM
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Or you could just be safe and spend $250 @ the RX7store for the Denso Competition pump and be good up to 500hp (20 minute or less drop in replacement install).
http://66.216.67.51/product.asp?0=211&1=260&3=320
The pump is very quiet unlike many high performance pumps which have a very annoying whine, ie you CAN NOT hear the Denso running from in or outside the car.
After my install, I shorted the pump to verify it was running and coulnd't hear it unless I did the old screwdriver to the gas tank and side of head trick.
k
http://66.216.67.51/product.asp?0=211&1=260&3=320
The pump is very quiet unlike many high performance pumps which have a very annoying whine, ie you CAN NOT hear the Denso running from in or outside the car.
After my install, I shorted the pump to verify it was running and coulnd't hear it unless I did the old screwdriver to the gas tank and side of head trick.
k
05-03-02, 11:19 AM
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Re: Bypass fuel pump resistor?
Originally posted by luneytune
It sounds like they bypassed the fuel pump resistor. This will only put stress on the pump, and you will just keep pumping gas from tank to engine bay to tank at high flow. The Ecu controls the Fuel pump relay that shorts the resistor at high demand, so you normally are in bypass at high load but a low load the fuel pump can relax a bit. It shouldn't make any difference to absolute flow rates from stock pump. IMHO
It sounds like they bypassed the fuel pump resistor. This will only put stress on the pump, and you will just keep pumping gas from tank to engine bay to tank at high flow. The Ecu controls the Fuel pump relay that shorts the resistor at high demand, so you normally are in bypass at high load but a low load the fuel pump can relax a bit. It shouldn't make any difference to absolute flow rates from stock pump. IMHO
So now the resistor would be bypassed, BUT the new wiring would allow the pump to receive the full 12-13.8v
and would give it more power to pump...
Yeah I'm sure it would wear the pump out eventually, but I only drive my car about once a week...
Does this make sense?
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05-03-02, 02:52 PM
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All of my expirience comes from toyota turbo's. It is common for them to run a special "amplifier" to their fuel pumps to run them at like 18 volts. I had one on my toyota 22rte that was all done up, and it solved my lean condition (I had the injectors, but lacked flow). Has anyone done this with an FD?
05-03-02, 03:03 PM
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on the fc's you almost have to rewire the pump. with the headlights on the voltage gets low at the pump. it is not a bad idea to rewire the pump. my friend did his without the resistor and the car runs fine. if it was my car (more stock) i would simply replace the factory wire and keep the resistor/wiring the same.
mike
mike
05-03-02, 03:52 PM
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I'm going to try this...it sounds like a good idea, at least until I come up with enough $$$ for a hi-flow pump...
Anyone have some ideas on how to make this work?
Anyone have some ideas on how to make this work?
05-04-02, 09:51 AM
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Ok another " TO DO " on my list...
Thanks..
Just make one HOT WIRE from the battery
to the FUEL PUMP ..
Sounds simple enough...
So you guys are sure their are no SIDE EFFECTS?
or Down sides??
How about a HOT WIRE from the battery spliced into the
factory Hotwire to the fuelpump???
Thanks..
Just make one HOT WIRE from the battery
to the FUEL PUMP ..
Sounds simple enough...
So you guys are sure their are no SIDE EFFECTS?
or Down sides??
How about a HOT WIRE from the battery spliced into the
factory Hotwire to the fuelpump???
05-04-02, 10:57 AM
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Originally posted by purepsi
1 side effect is that the fuel pump will not last as long due to the increase in voltage.
1 side effect is that the fuel pump will not last as long due to the increase in voltage.
Has ANYONE done a long term higher voltage test on our stock fuel pump?
Sure, there are certain things that have limits on the FDs, but certain things, like the tranny and rear end are able to support 500+hp
05-04-02, 11:10 AM
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Originally posted by purepsi
1 side effect is that the fuel pump will not last as long due to the increase in voltage.
1 side effect is that the fuel pump will not last as long due to the increase in voltage.
Running a hot unfused wire from the battery to the fuel pump is dangerous! If that line shorts near the tank or in the pump you have no protection by fuse.....could be bye bye 7.
05-04-02, 12:51 PM
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Originally posted by luneytune
Another side effect is a Fire!
Running a hot unfused wire from the battery to the fuel pump is dangerous! If that line shorts near the tank or in the pump you have no protection by fuse.....could be bye bye 7.
Another side effect is a Fire!
Running a hot unfused wire from the battery to the fuel pump is dangerous! If that line shorts near the tank or in the pump you have no protection by fuse.....could be bye bye 7.
As for the pump not lasting as long, I don't see why it wouldn't. It's not like we're talking about overpowering it, we're talking about giving it the true voltage from the battery...I mean that's what these things are tested on at the factory so I'm sure it will be fine.
05-04-02, 01:38 PM
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the pump sees about 8-9?volts cruising around and then battery voltage after it sees 1 psi (i tested this).
you are shortening the life of the pump if you make it see 12v all the time, but when was the last time you saw one fail?? ive never seen a factory fc or fd fuel pump fail, it is something to think about but i wouldnt be worried.
mike
you are shortening the life of the pump if you make it see 12v all the time, but when was the last time you saw one fail?? ive never seen a factory fc or fd fuel pump fail, it is something to think about but i wouldnt be worried.
mike
05-04-02, 01:49 PM
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Ok, so if it sees battery voltage when we are boosting, there really isn't any sense in directly wiring it. I mean, it's getting the full amount of voltage when we need it. This could probably explain why my fuel pressure guage jumps about 10psi at boost.....
05-04-02, 02:18 PM
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Originally posted by Flybye
Ok, so if it sees battery voltage when we are boosting, there really isn't any sense in directly wiring it. I mean, it's getting the full amount of voltage when we need it. This could probably explain why my fuel pressure guage jumps about 10psi at boost.....
Ok, so if it sees battery voltage when we are boosting, there really isn't any sense in directly wiring it. I mean, it's getting the full amount of voltage when we need it. This could probably explain why my fuel pressure guage jumps about 10psi at boost.....
05-04-02, 02:28 PM
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Originally posted by Pressurized
...the poor wiring only allows maybe 10v of the possible 13.8v to reach the pump, possible even less.
...the poor wiring only allows maybe 10v of the possible 13.8v to reach the pump, possible even less.
****, maybe I should just test it myself when I get a chance
. Hmmm...I wonder if the manual says anything about maximum voltage the pump sees.
05-04-02, 02:47 PM
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Originally posted by Flybye
But j9fd3s said he tested it, and that he saw full battery voltage. You saying you tested it or these guys at that shop tested it and they only saw 10v?
****, maybe I should just test it myself when I get a chance. Hmmm...I wonder if the manual says anything about maximum voltage the pump sees.
But j9fd3s said he tested it, and that he saw full battery voltage. You saying you tested it or these guys at that shop tested it and they only saw 10v?
****, maybe I should just test it myself when I get a chance
. Hmmm...I wonder if the manual says anything about maximum voltage the pump sees.
I know this is something I'm going to look into though...