BklynRX7

Ok as I posted before I had a fuel pump die and my walbro replacement possilby die(gotta test it) becasue of a crudded up fuel tank. I opened up the tank, scrubbed and rinsed and sweated for hours and have my tank clean to the point that only minor surface rust is visible and my fingers stay clean when ran across it. ALSo water left sitting overnight remains crystal clear even when stirred(kicked up). IS this good enough?? Several people warned me about tank sealers and other chemicals and I dont have the time/access/money to have it boiled.

Also I was just reading a writeup( http://www.1300cc.com/howto/how2/NOS.htm ) and it mentions being problems when putting a high flowing pump into a n/a car. WIll I experiance this problem with my walbro?? if so how can i fix it.

iceblue

Yes you will.

Wire in a low voltage resistor.

I am actualy looking into this myself.

BklynRX7

WHat will be the ill effects? just runnign rich? Would a piggyback solve this?

iceblue

Yes runing rich.

I dont know someone ells will have to chime in on this. I do not balive so though.

NZConvertible

You mean a dropping resistor? What would be the point of that? Why install an upgraded pump and then derate it? It would be far smarter to not put in an over-sized pump to start with. A Walbro is total overkill for an NA.

iceblue

Talking about a resistor pack identical as a TII. Low rpm.

Syonyk

And... you're planning to switch that resistor pack in and out based on... which control line, exactly?

I don't believe the NA ECU puts out a signal that can be used for controlling the fuel pump resistor pack.

-=Russ=-

iceblue

I have no clue Russ. That is one of the reson I said I am looking into this myself. About converting the TII resistor pack to the N/A. I want to know b/c the FD pump I have in the TII swap is pumping alot of fuel in at idle and can cause the car to flood out during warm up.

I did read a post earlyer yesterday that stated to wire in the TII resistor pack. Hinting it was posible with little effort.

My previous asumption had been to use a RPM controll such as one from summit for $30 identical to the ones people are using for electric 6pt. To wire up the TII fuel pump resistor using the RPM activator to swap between resistor relay and full power relay to the pump.


For the starter of this thread it would be best and easaly avoided to just use the correct pump.

BklynRX7

Well i installed the walbro already. i was always under the assumtion that no matter how strong the pump is, the injectors were the bottom line for the ammount fo fuel making it to the engine. Its ran fine for 2 days, no flooding or abnormal backfire.

ANyone have an opinion about the tank question?

Syonyk

The problem is not with the pump or the injectors, the problem is with the fuel pressure.

The RX-7s (and most other fuel injected cars) have a recirculating fuel system. The pump in the tank pumps constantly, feeding pressurized fuel to the primary fuel rail. The fuel flows through the primary rail (possibly getting some injected into the engine), into the secondary fuel rail (possibly getting injected into the engine), through the fuel pressure regulator, and into the return line back to the tank.

The fuel pressure is maintained by (gasp) the fuel pressure regulator. It vents excess fuel into the return line to keep the pressure constant. The problem is that it can only flow so much fuel - try to push more fuel into it, and it won't be able to pass it at the design pressure, and fuel pressure will rise.

The fuel pressure problem is worst at idle when the engine isn't consuming much fuel. The bulk of the fuel is going through the pressure regulator and back to the tank. And, with upgraded pumps, the fuel pressure regulator can't flow enough, so pressure rises.

The injectors cycle for a given period of time. Their flow is a result of the time they're open, as well as the pressure feeding them. The ECU doesn't know the fuel pressure, but it knows where it *should* be. It calculates the injector duty cycle based on what the fuel pressure should be. If the pressure is higher, more fuel gets injected, and the engine runs rich.

-=Russ=-

NZConvertible

Slight correction; the FPR is there to keep a constant pressure differential across the injectors, not a constant pressure. This is so that the injector flow rate remains constant regardless of manifold pressure. If fuel pressure was kept constant, as manifold pressure rose it would get harder to push fuel through the injector into the manifold, and hence less fuel would be injected.

Syonyk

That's right, thanks. I knew the vacuum line going to the engine was important for *something*.

-=Russ=-