Step one is complete.
1/8 in has been milled of the top of the primary rail to accept 850cc injectors.
The inlet side recieved 1/4 NPT tap for the 1/4 NPT to 6-AN elbow adaptor.

 

Can the Marren fail like the stock FPD?

 

I suppose given enough time anything is possible but it is very unlikely. I looked at the diaphram inside the Marren FPD and its pretty damn sturdy, besides it can be rebuilt easily and only costs a few dollars for the replacement diaphram.

 

Ok, I just had a milled primary rail with 850s installed and a pulsation damper...also Secondary rail with 1600s...(I thought "Damper" was wrong but I looked on the box and Mazda says its Damper not "Dampener") However, I have the SX FPR...Do I need to have both?

 

That is the question I had and the preliminary answer based on some steady state flow equations shows the damper is needed. Especially with the larger injectors and higher fuel pressure. Untill someone who is an expert in fluid dynamics rejects my findings, the answer is yes, both are needed.
Of course many people will tell you that they have eliminated the FPD without a problem, but the final choice is up to you.

 

Trexthe3rd, the pic u posted of the fuel setup, is that just to usde the Marren FPD? Or is that just a setup you will be running?

 

Hi evryone... I know thet is an old post but I would like to tell my opinion on that.

Maybe I am a noob here, but I know something about fluid dynamics. The fuel flow in the primary and secondary rail is not steady state, but it is transient (time dependent). Totaly different behavior of the flow. The pressure wave is caused because of the opening and closing injector and then it is traveling along fuel rail. The bigger the injector is and with that the fuel flow, the bigger the pressure (shock) wave it will be generated.

In my opinion, for that the FPD would be placed closer to the second fuel rail not to the first. The FPD will then be more effective of removing these pressure wave and they would be removed quicker, because of the path that it is smaller. That way the total (static+dynamic) pressure would be constant, thats what Mazda want to do, but they placed FPD before the first rail, whatever.

The FPD may be considered to be placed in the fuel system when the fuel flow is great (also short duration betven two injection) and when the amount of fuel to be injected in the chamber had to be precised. Because these pressure waves can couse undisturbed amount of fuel that injector injects.

The other thing is that the FPR can not damp these waves, because the pressure is dynamic, not static. On the other hand if the FPR have build in FPD the stock FPD is no longer needed. Because the FPR with build in FPD regulates static pressure and eliminates the dynamic one. That way you will be fine.

Someone that is freak in some way would say, why not put FPD before and after each rail.... that way the dynamic pressure would be removed even quicker, but what will you get wit that setup, will it be worth it?

 

So removing the FPD will actually hurt the engine how..?

 

As a past career hydrodynamicist, I fully agree with these statements.

As to a Pulsation Damper need in an RX-7; who really knows .. but I will add these comments:

1) our cars run high rpms, creating very high frequency injector pulsing,
2) they batch fire, again increasing pulsation frequencies,
3) the primary and secondary rails are separated so even if an aftermarket FPR provides some high frequency damping (it obviously does low frequency by its very nature) it is a very long way from stopping primary pulses from creating shock waves. Since the fuild flow is subsonic, pressure waves (traveling at speed of sound) travel both ways.

 

Might be a dumb idea but if you were to remove the Mazda FPD, which I understand is prone to failure, and instead installed a fuel pressure gauge at or near that point could the gauge do double duty? Give you fuel pressure readings and mitigate the shock in the fuel system due to the injector opening and closing cycles? It would seem that the mechanism which allows the needle to move based on pressure is similar to the function of the rubber diaphram in the FPD.

Jeff

 

^I wouldn't exactly call it "prone to failure". Yes it will fail given time, heat and usage. So will every other mechanical device under the hood - solenoids, sensors, hoses, wires etc. My replacement FPD has lasted many years and miles now.


As for your idea, a gauge probably has not have been designed to absorb those kinds of pulsation frequencies and probably won't perform the same task as a pulsation dampener as effectively as the FPD.

 

or you could just get an aeromotive FPR that has a pulse damper built in.

http://www.rx7store.net/product_p/aeromotive%20fpr.htm