micah

I just spent the last hour searching about the fuel pulsation dampner problems, engine fires, banjo bolt mods, etc... Almost all of them say that it applies specifically to the 86-88, but also happens sometimes to the 89-91's. The only "Fix" is a banjo bolt mod for the S4's which isn't really a fix at all. I know it works and all, but it isn't ideal for the fuel system. It was put there for a reason. I haven't seen a fix, however, for the S5.

I raped my S5 parts cars engine bay the other day to pull the engine out and salvage parts. I started looking at the fuel rails. Whats stopping somebody from hack-sawing off the current PD, capping it off, tapping it with a fitting, and running a remote one? Seems logical to get the PD away from the heat of the engine while at the same time replacing it with a higher quality, possibly rebuildable, aftermarket one. It seems super simple to do. I have a welder and could perform this mod; what do you all think about it?

Looking specifically for replies from RETed, Aaron Cake, HAILERS, Icemark, etc.. I want to make sure there's not something I'm overlooking in this fix.

SpooledupRacing

IMO the fuel dampner is not "needed" it was there for a reason... so was the cold start assit, and the omp

however overtime we have found to remove them too

this is something that has been going on since cars begin.. engeneers put things on them and we remove them (egr valve, convertors etc)

now if they could only pluck the Cavelier from existance lol

Goofy

I think the reason the PD is where it is is because you want it as close to the injectors as possible and it fit there.

Aaron Cake

iTrader: (1)

Nothing really. In fact, this is how I add AN fittings to the stock S5 rails. Cut off the stock ends, then braze/weld on the AN flare.

Do we really have to go through this again? I'll give you the cold start assist tank; that was just a dumb idea and Mazda admitted it. The metering oil pump is another thing that people like to debate, however Mazda doesn't see it as much of an issue considering they continue to use it to this very day.

Totally different issue. These components were placed on the car to comply with federal emissions requirements.

If people REALLY want to start yet another FPR debate, they can instead simply read the one in the Archives.

micah

Thats good to know. I'll have to give it a whack soon as I get my garage cleaned up (I'm sure you can relate, I've seen pics of your basement/garage. LOL, j/k man)

Honda civics don't have OMP's... But they STILL have fuel pulsation dampeners... Most, if not all fuel injected cars do. Millions of dollars of research can't be wrong.

Cold Weather Assist AFAIK is RX-7 specific. I'm sure some other cars have something similar... And it actually works in REALLY cold climates from what I hear.

I guess that makes a little sense, but, there's no PD on the secondary fuel rail, it relies on the dampening from the primary fuel rail... and those are separated by a good amount of hose. Also, liquid doesn't really compress, so I would imagine these pulse waves would travel as far as they needed to be dissapated/absorbed. The trick would be to use large enough diameter to compensate for the distance and inconvenient location.

drago86

The larger the cars injectors, the more a PD is needed. Rx-7's have huge injectors compared to normal cars.

Black91n/a

You can't compare other car's to the RX-7 when it comes to the OMP, it's a rotory specific item, like apex seals. Some piston engines have similiar sort of things, like piston oil squirters, but that's about as close as it gets.

micah

Yeah. I suppose that was a bad example... It happens, chill out. Jerk.

A better example would be the suspension of the car.... You COULD take it off... you don't really NEED it... but if you did, it would shake the car apart as well as make your butt hurt.

If you remove the pulsation dampner, and your injectors die or what not.... after mazda rapes you for 300 bucks an injector, your butt will hurt.

Does that analogy work?

micah

I have a question about your brazing. Are you sure its strong enough? Also, are you just using a standard solder? I was going to MIG weld it.. It'll be uglier than a braze, but brazing doesn't seem strong enough. But, I guess water pipes in a house are brazed, and thats pretty high pressure.....

Any thoughts?

Goofy

Compression waves move at the speed of sound though, so you still want it close to be able to dissipate the pressure difference.

micah

Right, but what about the secondary injectors? Why don't they have their own PD?

Bama420

iTrader: (1)

what is the prpose of the PD? sorry, I'm a noob when it comes to emissins and electrical. And the rats nest in general.

micah

Every time the injectors open, they create low pressure.... everytime they close, they create high pressure. When this happens frequently, it creates rapid pulses of shock through the fuel system that can hurt the fuel injectors and perhaps other parts of the fuel system (?). The pulsation dampener is there to act like a fuel shock absorber... neutralizing the effects of these pressure waves.

At least thats my understanding... but I think its pretty accurate.

Goofy

Don't know the design off the top of my head, but I'd assume they're close enough to the primaries that the damper does fine.

micah

There's probably a foot or so of tube between them. Which makes me think that it would be okay to locate a better PD on thicker tubing, the same distance away from the primary. Maybe have one per fuel rail.

micah

What does everybody think about this:
http://www.matronics.com/fuelchec/dampener.html

Its like 47, and is simple as hell.. Uses the compression of air to absorb fuel system shock. The application they talk about is for an RV-8 plane. If its good enough for aviation its gotta be okay for cars.. right?

Aaron Cake

iTrader: (1)

Water pipes in a house are generally soldered. But we are (at least in Canada anyway) moving away from copper pipe to plastic IPEXX pipe that seals together with barbed nipples and compression fittings...at little OT though....

As for brazing, in this application it's fine. If you want to MIG weld it then that's also OK. In general a braze between two flat surfaces (think overlapping sheet metal) is basically as strong as a weld. So for close tolerances like fittings where you may be joining different metals (the fuel rails are steel but most AN fittings are aluminum) brazing is ideal. However if you have steel AN flares then MIG welding will work just fine. Make sure to pressure test it though because it's easy to make leaks. Another option is TIG, which gives you the choice of just fusion welding the fitting. This almost guarantees that it will be leak free, and the weld is tiny and neat.

ourxseven

iTrader: (1)

riverzendz

Instead of cutting, hacking, welding, etc. why not just use the primary rail from an S4? It can be done, it has been done, and it's a much easier solution. You can banjo bolt that rail easily OR run an aftermarket FPR/PD.

riverzendz

Read this thread. Specifically the comments from RotaryRessurection and Icemark.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/can-someone-direct-me-611176/

micah

Good info! I don't have access to TIG though, I wish I did... Too $$$ though. I'll have to give brazing a try. Now I just need to find AN flares just the right size. Mcmaster-carr?



Also, I don't want to put an S4 fuel rail on my S5... Not because its any different, because it WILL fit... but, the size of the fitting for the PD is smaller than I would like. If I'm going to do it, I want to have a large passageway for pulsation waves to travel.. If I'm going to remote it, I need to make sure to compensate for passage size. Even if it makes no sense, its a peace of mind thing.

Aaron Cake

iTrader: (1)

You can likely get the AN flares from a local hydraulic shop. Buy steel so it's easy to braze/weld. If you end up having to buy NPT to AN adapters then that's fine as well since you can grind the NPT thread flat so that it's a press fit into the fuel rail.