brycer_77

Can someone please tell me if the Pulsation Dampener is needed if I do the Parallel Fuel System set up. If it is do I leave it on the fuel rail or does it go somewhere else.

fcturbo2

Are you using aftermarket fuel pressure regulator?.. If so you can get rid of the stock PD.

IAN

iTrader: (3)

I will not be using mine since I will be using an aeromotive pressure regulator.

Just like what fcturbo2 said

brycer_77

I will be using an aftermarket fuel pressure regulator. So do aftermarket fuel pressure regulators have pulsation dampeners built into them or what? Or are they just designed not to need one.

SirCygnus

iTrader: (1)

i would like to know this aswell.

cbrock

iTrader: (1)

you really don't need one. As far as I know, the only use for the PD is to make a mobile grill.

Icemark

Left me speechless with that >edited for content< answer...

do you really think that??? I hope you are just joking.

A PD is required on any fuel injection system with multiple injectors on the same rail. Some aftermarket FPRs do have a PD built into it.

But I guess that is because you don't really need one according to cbrock.

NZConvertible

Ice beat me to it. If you don't know what it's for, don't guess...

RETed

I find the pulsation damper unnecessary.
Most aftermarket FPR's do their own internal dampening, so a pulsation damper on top of the aftermarket FPR is unnecessary also.


-Ted

cbrock

iTrader: (1)

See Reteds post above.

You guys like to bust everyone's *****. He was switching to an aftermarket system anyway and hence a new regulator...damn.

On the flip side, we all know it's to dampen the pulsations from the pump. But does anyone really know what happens if you were to bypass the system on a stock RX7 fuel setup?????? I'm sure both you guys have.

This is where the guess comes into play. Again, my guess is that the car will still run and honestly, if my PD were leaking, I'd much rather try bypassing it first instead of installing another POS stock PD. Hmmm...car fire or fuel pulsations in the rail? But as a disclaimer: I HAVE NOT TRIED THIS....there happy

More scientifically:
I guess if the changes in pulse were great enough you could create a hydraulic transient or "water hammer". The *could* create higher than normal pressures in the system. Which in turn *could* damage parts of the fuel system.

Icemark

Ah, right there shows that you don't really know what a PD does and why.

It has absolutely nothing what so ever to do with the fuel pump. There are not sufficient pulses from the fuel pump even making it down three of the 8+ feet that the fuel must travel.

It is only for controlling the shock waves in the fuel rail from the injectors opening and closing.

And yes it has been proven, that not using a PD on a fuel rail can result in one injector going lean at specific RPMs as well as other issues mentioned above. Hopefully for people that "don't believe in them" that lean spot is at an RPM you don't use much.

cbrock

iTrader: (1)

It can be from both. The system is closed until an injector opens, at which point pressure is dropped across that section. So yes, the injectors operating can create the pressure pulses too. But why wouldn't the fuel pump? So what if it's in the tank? That is part of the system too and with the RX7's fuel pump controller that bumps voltage and with 1:1 pressure with boost, the line pressure itself is changing all the time. This will also create pulsations and should be seen through the entire system.

Now as for the vehicle going lean, what was the test? A dyno run of a car w/o a damper? Was it a stock fuel system or aftermarket likes Reteds parallel? Was it run stock and then right after the change? Was there a fuel pressure gauge? Stock computer of stand alone?
Which injector went lean or did they all? Was the injector bad? The questions go on an on and the variations are endless.

SirCygnus

iTrader: (1)

to put it another way, do you get water hammer from your automatic sprinklers coming on in your house? the vibrations get absorbed by the hose. simple as that. how about at the gas station. do you ever hear water hammer in the gas hose? no. why not, cus the rubber dampens it.
think about it.

now if you where runing big *** injectors, then yes. but for what we use, no.

the hose absorbes it anyway. whoes ever heard of a rubber hose vibrating? now if it was a solid hose the whole way, then yes, but in this case, it doesnt apply.

just go with the flow., and do what you want.

cbrock

iTrader: (1)

You could create a water hammer in a hose...and it doesn't matter the diameter (very serious situation for fire fighters). But in most cases you aren't turning the water on and off fast enough to cause a problem. Even if there was a problem the rubber hose would stretch to account to the pressure. In our fuel systems much of the path is hard line. Mine is all stainless braided rubber hose, but that stuff doesn't give too much. So could a water hammer occur? Hmmm...maybe, but I really doubt it..but if a wave were to start, it would certainly travel through the entire system and if it were great enough would break whatever happens to be the weakest link.

But you are right, I really really don't think it matters. People have offered PD banjo kits to remove it from the system. The feeling there was that it causes no real difference...hence my first reply to this whole thread. So if you have a leaky PD and need to drive the car right away, I'd say bypass it. If you have the time to wait for the parts and the $$ buy a new factory PD..DO NOT BUY A USED ONE. Mine with 45,000 miles on it..still gold in color had the screw fall out. If you have money falling out your ***...or you're obsessed with your car and it's not your daily driver then rip out the whole system and run braided hose to a nice new FPR and be done with it.

So the REAL answer to this thread....drum roll.

If you're going with the parallel system, you will have had to have bought a new FPR and can thus remove the PD from the fuel rail. Simple and I suppose we all know how the PD really works and basic fluid mechanics

RX-Heven

iTrader: (1)

Thats funny especially since they are one of the main causes of underhood fires in our cars. Toss that junk and put in a real fpr.

NZConvertible

This has nothing to do with the pump. For starters, the pump uses an impeller, so the the pulsations it creates are tiny and completely inconsequential. Pulsation dampers are installed for one very specific and long-proven reason, and that's to ensure even pressure at the inlet of each injector in a multi-injector rail.
You're assuming this is some phenomenon specific to RX-7's. It's not! It will happen any time you have multiple injector mounted in a rail. It doesn't matter what engine you have, how many fuel rails you've got, what computer you run, whether it's modded or stock, or any of that. It's simple fluid dymanics and it always happens. The proof of that is that pulsation dampers are fitted to just about every engine equipped with EFI. Can you explain that? Do you think car manufacturers would go to all the trouble to fit millions of these things if there was no good reason?

The fact that the FC has a pulsation damper that leaks with age does not change the fact that you should have one, it just means you should replace it with a new one. If you're making major changes to your fuel system then you can fit an aftermarket one or use a FPR with one built-in.

RETed

Please, can we drop the water hammer analogy?&nbsp; This only applies to a dead-end system, and the stock fuel system (or the parallel one) is not dead-ended.&nbsp; Someone brought this up in a previous thread, and it really does not apply.

I've been using banjo bolts on numerous customer cars, and some of them are big projects using Haltech EMS units to control everything.&nbsp; If there was a lean problem, it would easily show up on the Haltech as a "spike" in the fuel map.&nbsp; All the maps have been smooth, and I've never run into any problems associated with no pulsation dampers.&nbsp; Ask the CZ guys, as none of them run the stock PD's on their FC's anymore.


-Ted