Now I know there's a million FPR and FPD because I've been trying to read them all. I sent my stock injectors out to be cleaned and I've been reading that the fuel pulsation dampener is a fire hazard and it should be replaced preventatively. Now my FD is pretty much stock and I'm not planning to add much power to it, I'm more so going for reliability mods. So the way I see it going the route of removing my FPD and going with an aftermarket FPR seems more reliable and even seems cheaper now and in the long run (staying stock fuel hose lines and barbs for now) with the rising price of the two parts. I'm looking into getting the SARD adapter or one like it, but does anyone know if they will work on the primary side as well so I wouldn't have to tap my primary rail to delete the FPD? Also I've been reading the pros and cons of the Aeromotive. I'd say the two regulators I'm looking into right now are an Aeromotive and an AEM. But there are multiple of each brand. Is there anything I should be looking for when picking one? What I know is that I need one that can do the job of the FPD(not really sure what to look for, for that), adjustable PSI for stock idle at 38psi, and a pressure rate of 1:1. I'm running a walbro 255 with stock ecu if that matters. I have a PFC I'll be hooking up at some point. I've also considered keeping the OEM FPR and replacing the FPD with a Marren. But the FPR route seems like a two birds with one stone.

These are the two FPR I'm looking at right now.

AEM

 

You have a lot going on there.....

to simplify, for your set up and many others the fpd doesn't do anything and offers nothing. Same as the ast. For your set up, there's 0 reason to use an aftermarket fpr. The stock one is fine and will be fine for what you're doing.

tap the primary rail, delete the fpd, keep the stock fpr. You would benefit more from doing the full fuel hanger mod because with that 255, you will inevitably need to anyway.

 

In my opinion, the engineers installed that dampener there for a reason. If you are planning on using stock injectors and such, I would personally keep it. Maybe modern injectors aren't as susceptible to the pulses as the injectors in the 90's were, but Mazda wouldn't fit that part to every car if they didn't see it absolutely necessary. Manufactures are known to cut corners and save where they can, if this wasn't needed, they would have left it off especially given the price of it. I recently went through this same thing with my car and after all the research, this is what I came down to doing. Just keeping everything stock since I wasn't planning on going above 350hp in the future. If you are, then you will need an injector upgrade anyway and then it would make sense to replace with modern upgraded stuff. I understand that many people delete this and are "fine." but I would rather have peace of mind knowing the engineers that spent thousands of hours developing and tuning these had a reason to keep it. But the choice is yours, many have it deleted and are fine.

If you are set on deleting the FPD, then go with was FDAUTO said above, keep all your stock stuff and just do the FPD delete.

 

Fully disagree on that stance in general. Manufacturers/engineers are not infallible and do in fact infalliate lol. Also not implying we as enthusiasts are "smarter". Sometimes operating primarily off charts, graphs and other data will have you chasing things that don't necessarily translate to anything in the real world. I feel this is where the idea if the AST came from.

There is no proof whatsoever that it does anything. Simply stating that it exists so it must be important or that it was used on a race car doesn't imply significance in its operation. Just the same, it can be said that it exists in the race car BECAUSE of the same logic. The Japanese are known to do a lot of things without really knowing why.

On the flip side...... "peace of mind" means something different to everyone. If it brings you comfort to spend money on a part that has shown to serve no purpose other than fail simply because "the engineers [whatever]", then do what makes you happy.

As much time as we spend working on these cars and the amount of them that have passed through our doors, I can say with absolute confidence the AST and FPD do nothing and are best removed.

 

There are lots of articles you can dig up with the purpose of FPDs. RX7's aren't the only ones to run them. There is a lot of science behind them, everyone can look that up themselves but there are months of reading you can do about the science and engineering behind them. Lots of Rabbit holes to go down with that route. I've read a couple threads related to RX7's in general about speculation with the difference in the size of the primaries and secondaries and the effect of the pressure oscillation when the secondaries engage (which would be when it would be the most crucial to have working.) I'm a "do your own research" type of person so me being an Engineering major as well as lots of experience in the field as a tech for different manufactures, I get the logic behind its purpose and possible use cases for it. My peace of mind is knowing that it will give me that much more safety on my engine that is very susceptible to knock with catastrophic results so I decided to keep it. Like I mentioned above, many people remove it and are fine. I chose not to. My original one seems to do just fine for the first 30 years and 45K miles so I chose to keep it.

 

As one can see in just 5 posts, there are opposing views on the topic of whether to FPD or not.
Good reasoning on either side, I suppose.
It is a debate as old as which oil to use and the responses will reflect that.

Personally, I like to KISS so I run the OEM fuel setup since my car is close to OEM specs. On the flip side, I don't run an AST; but understand the theoretical value.
YMMV.

 

Absolutely... I feel in general regardless of the topic, if something can be debated in such a fashion then there is no right answer. It comes down to preference and whatever YOU feel is right for YOU.

Although, one could argue the pros and cons in this particular circumstance and there are no cons to deleting the FPD and AST but definitely cons in keeping it 😎😎😎. Call me bias for leaning more towards life experience and consistently repeatable results vs research papers discussing theory lol

Not knocking anyone who chooses to keep either... really it's just personal preference.

 

i would keep some kind of damper in the system, the stock one is fine, the failure rate is really low.
deleting it just adds an unknown variable, and for what benefit? more places to leak? the stock part isn't expensive.

part b for the regulator, SARD sells an adaptor and then you can put a regulator where you have room. pretty sure its not the same as the dampers flange, but its been a while.
or there are a few Nissan regulators that look like they would just fit.

on my car, its stock fuel too, because i need to keep the air pump and ACV. however i've heard that raising the fuel pressure helps atomization, so its tempting to try it. that and it would keep my peak duty cycle a little lower, ive been told to keep the PFC to 85% peak duty to keep the driver chip cool. so if mine tuned in at like 89% percent duty, i could bump the fuel pressure a bit and get it back in line

 

Yep.
On one side - Practically speaking, the car will run fine with and without an FPD or AST if done correctly.
On the other side - Engineering-wise, Mazda put the stuff there for a reason.

 

This is the Rabbit Hole I spoke of. If you do a search on this forum and others related to RX7's, you will find many threads like it as I did before I did my fuel system restoration. This is a question that has been pondered for 20 years which is why I say take a day, do your own research and make up your mind based off what you find, not what one of us just tells you to do. Like was mentioned above, opposing views in just a couple posts with valid arguments on both sides. Do some digging yourself and see what conclusion you reach.

 

Thanks for the responses guys. I don’t think I want to remove the FPD unless I’m putting something in to do its job, either an aftermarket Marren FPD. Or a FPR that will do its job. While I have no doubt people are running their cars fine without the FPD, I like to think that it’s there for a reason and I would rather be on the cautious side of keeping something there to do that job. My intention was not to bring this debate back into play but to find more information on how I can set mine up with something doing the FPDs job.

 

You might consider giving this thread a read (in the event that you haven't) https://www.rx7club.com/single-turbo...tions-1090373/
Lots of neat info regarding fuel pulsation with some actual data to go with it. I was formerly of the belief that it should be removed but after reading the aforementioned thread and doing more research, I am inclined to believe that it is best retained.

Hope that helps.

 

I did not see this one, I’m going to give it a more in depth read when I get off work but, I think I might just go with a Marren FPD. Then I remove the failure point and can still have peace of mind. I’m waiting on a call back from Marren to answer a few questions. If I can T it into the hose right infront of the primary rail that would be easy. I’ll still have to tap the primary unless the adapter for the fuel pressure regular fits. I might order an adapter just to test it. Looks like they have some for around $10. If not I have to decide whether I want to use a brass or aluminum fitting to the primary since aluminum likes to become one when treaded together but brass has zinc which technically isn’t good for fuel usage.

 

I'm having trouble finding the post, but I think I've seen at least one example of a car that had a weird 'lean spike' in ECU datalogs and it was solved by removing an aftermarket pulsation damper. So I would either get a new OEM one, or use an aftermarket pressure regulator only (without a separate pulsation damper). Remember to swap out any rubber fuel lines, if you still have original 30-year-old ones on the car they are likely on borrowed time. Use OEM clamps, some people prefer to use worm-drive hose clamps that tighten using with a screwdriver but they don't work as well because they don't maintain tension like spring clamps. New OEM clamps are super cheap, especially if you have the Mazda Motorsports discount.


For what it's worth my car has had an AEM pressure regulator (on an aftermarket fuel rail, with ID1000 injectors) for about 15 years and it has worked well. ECU datalogs show the fuel pressure is good, both according to the fuel pressure sensor and the wideband gauge.

 

Decided to go the FPD delete route. Unfortunately the FPD and the FPR were different sizes. So I had my FPD modified to be a tiny bird bath. Had my local shop remove the top from the FPD and then they welded to two small holes up. Gonna throw some paint over it to prevent rust. Cost me $8 and I won’t have to tap my fuel rail.

 

Radium is another option for aftermarket FPD. Since you're all OEM, I'd just replace with a fresh Mazda FPD and inspect regularly. Mazda didn't spend the money to put it there for no reason although the cases I've heard of fuel pulsations causing an issue were higher power and fuel flow rates.

Jack

 

I ordered the Aeromotive fuel pressure regulator that they say the diaphragm does the job of the FPD. Cost me about the same and I wont have to worry about it.