Fuel pump resistor and fuel related question
05-22-05, 07:35 PM
#1
Rotary Enthusiast
Thread Starter
Fuel pump resistor and fuel related question
Does anyone have an idea what the fuel pressure difference is between having the resistor and bypassing it? The reason I'm asking is, I was monitoring the fuel pressure while playing around with enabling and disabling the fuel pump resistor and I only saw a 1 psi change in the fuel pressure. Searched through the FSM but no luck.
Also, what would be a safe upper limit for fuel pressure? It appears I have hit a limit on the injector output when tuning the RX6 single to 15psi. The injectors are 850/1600. I will be contracting some dyno time to get the fuel pressure under boost, it just seems strange that I would hit this limit so early.
The secondary fuel rail and injectors came from the RX7-store, the primary fuel rail is stock (so is the line from the primary to the secondary), could this be the restriction that is limiting my fuel output?
Also, what would be a safe upper limit for fuel pressure? It appears I have hit a limit on the injector output when tuning the RX6 single to 15psi. The injectors are 850/1600. I will be contracting some dyno time to get the fuel pressure under boost, it just seems strange that I would hit this limit so early.
The secondary fuel rail and injectors came from the RX7-store, the primary fuel rail is stock (so is the line from the primary to the secondary), could this be the restriction that is limiting my fuel output?
Last edited by Trexthe3rd; 05-22-05 at 07:41 PM.
05-23-05, 04:21 PM
#4
RX-7 Bad Ass
iTrader: (55)
Might want to watch the voltage going to the fuel pump. The resistor bumps voltage from 12v or so to 9v at idle/light load - I believe that's done for noise reasons.
I found on my FC back in the day that the voltage to the fuel pump was VERY low, especially with a lot of load on the system (lights, stereo, AC fan, defrost, etc.) I saw as low as 10v at full throttle. Not cool.
If you start modifying your fuel system, you NEED to find out what kind of voltage the fuel pump is getting with an electrical load on, and if it's low, fix it. The easiest way is to bypass the fuel pump resistor then run a 12 gauge or so wire from the battery to the fuel pump, and use the stock fuel pump wiring to switch on the relay.
The lower the voltage the pump runs at, the less the pump puts out. It needs to be consistent.
Dale
I found on my FC back in the day that the voltage to the fuel pump was VERY low, especially with a lot of load on the system (lights, stereo, AC fan, defrost, etc.) I saw as low as 10v at full throttle. Not cool.
If you start modifying your fuel system, you NEED to find out what kind of voltage the fuel pump is getting with an electrical load on, and if it's low, fix it. The easiest way is to bypass the fuel pump resistor then run a 12 gauge or so wire from the battery to the fuel pump, and use the stock fuel pump wiring to switch on the relay.
The lower the voltage the pump runs at, the less the pump puts out. It needs to be consistent.
Dale
05-23-05, 04:42 PM
#5
Rotary Enthusiast
Thread Starter
Maybe I'm off on this but if the fuel pump can maintain a set pressure for any given flow then it should be O.K. For example, if you want the fuel pressure to be at 50 psi and regardless of whether the injectors are at 10% duty or 95% duty, the fuel pressure is kept at 50 psi (assuming there is not fuel pressure regulator).
Statically my fuel pump is putting out 95 psi of fuel pressure. If I had a voltage problem, wouldn't that be much lower?
Statically my fuel pump is putting out 95 psi of fuel pressure. If I had a voltage problem, wouldn't that be much lower?
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