One of the main reasons for a pulsation dampner is to keep from having pulses due to the injectors opening and closing. If you start getting pulses in the fuel rails you risk flooding or leaning out. I would like to know that I'm not going to lean out because of fuel pulses. But then again I don't like blowing my motor.

- Steiner

 

This is one of those often debated things, just like 3mm seals, premix, and all the rest. Bottom line, you have a few choices:

IF you're okay with spending a few bucks, then either get a new stock PD, or modify your fuel system to run aftermarket components with an external or integrated PD.

IF you're in a bind for money, then you can choose the lesser of 2 evils: leave the PD in place to leak and burn your car up, or install the 10 dollar banjo bolt. Doing so *WILL* prevent leakage or a fire which is a SURE way to destroy your car AND engine. Doing so *may or may not* cause long term damage to injectors, fuel pump, or the engine itself (modded turbos only need to worry about this) via lean condition or uneven fuel delivery.

So, either leave it the way it is and you *know* that it's going to eventually burn up, or put in the bolt and never worry about a fire, but always wonder in the back of your head if you're causing some slow, slight damage to fuel system parts that are available all day long from partscars for little of nothing should they ever fail.

OF course the highly modded turbo guys shouldnt try to take the shortcuts, but then they're on a mission to spend money in the engine bay anyway so it's a moot point IMO.

Whatever you do, don't leave it alone.

 

A fire will most likely not destroy the engine. The electronics sensors and wires yes, but unless it gets hot enough in there for a long enough time to actually warp the housings than the actual engine will be fine. While operating without a PD for an extended period of time can cause damage to the injectos, operating without a PD for any amount of time, will risk running lean. It does not take time to make the injectors lean out without a PD, it only takes the fuel pulses. Modded turbos are also not necessarily on a mission to spend money. There are plenty of ways to make a nice turbo setup without spending countless thousands of dollars.

- Steiner

 

Do you have some proof? Cause this is looking like a real one sided argument to me. I see an experienced engine rebuilder saying that nothing will probably happen, and if it does its with inexpensive/easily accessible components. I also see RETed saying that he has run the banjo bolt for a long time and that he hasn't noticed any engine damage.

Now on the other hand I have NZ Convertible and Steiner telling me that my injectors are going to lean out, and fail. Your proof is where? Do you have an unbiased source that can back up your claims?

I agree that the FPD probably aids correct fuel metering, and the 'water hammer effect' is obviously present in this fluid system, but how strong is it? What kind of pressure differences are we talking about here? Is there any proof that there are significant enough changes in fuel pressure to damage the injectors and or change the amount of fuel inject to the point that it affects engine durability and performance?

We have a part whose failure mode can result in serious damage, on the other hand we have a modification that has no proven ill effects.

If your against the Banjo Bolt the burden of proof is on you to explain your argument.

 

A friends FD burned down. His suspension melted pretty badly. Not only that but imagine what the engine dealt with as far as temps being at the site of the fire, suspension parts are about a yard away from all the fuel ****.

 

hey! where is that parallel fuel rail thing on ReTeds site at? im looking but not finding!

 

http://fc3spro.com/TECH/MODS/FUEL/fpr.htm

 

I have the Banjo Bolt mod done to my car and feel very good about doing it. I'd rather drive my car around with the possibility (see note below) that my injectors will fail or something than thinking about the possibility that my car will burn from an engine fire.

Note: I have yet to see proof that a pulsation dampener is actually needed and that the banjo bolt mod is detrimental. All I've seen is opinions.

 

my bad. found it by accident!

 

It's a simiple manner of fluid dynamics. The basics is that the injector when it opens creates a low pressure zone, this can be transferred throughout the fuel rail. If you want more information about it read up on some physics, it's not too complictated. That said, I never said that it will fail ultimately and always fail, I said that it is a possibility, and it is not time dependent. Considering how many manufacturers are using Pulsation dampers, and the fact that mazda engineers designed the fuel system with the pulsation damper as a vital part of it, I am not going to go against the data and research that they have done. If at some point I have the time I will investigate and find out, that won't be for a long while. Unless you have proof showing that the pulsations in the fuel rail aren't large enough to cuase damage to the injectors, the rails, and the motor I will continue to utilize the research and design that mazda has already done, and keep my motor from another potential problem.

So you are saying that the suspension is going to burn down if you use an aftermarket fuel pulsation damper that doesn't leak fuel like the stock one?

- Steiner

 

Wow, I guess you never had an engine fire due to a PD leaking huh...
That ******* PD almost caused me to get rid of the FC.
This is what BURNED and how much the local Mazda dealer wanted to charge me to replace the part...
Main engine harness - $1,200
Fuel injectors - $300 TIMES FOUR = $1,200
Oil injectors - $30 TIMES FOUR = $120
Oil injector vacuum splitter - $40
Miscellaneous vacuum hoses

That's over $2,500 IN PARTS.
With labor, they were going to charge me over $5,000 with labor!

I'm not going to even mention the burnt paint on the hood...

Now, if I had paid all of that to fix the car, you would call me STUPID, right?

Because of this crap, I'm very anti-PD.
Now you know why.

I've done dozens of banjo bolt conversions, and I've never had any problems with any of them.
In fact, I only know of two confirmed reports of not having a PD was causing headaches.
One is Max, which is arguable since he thought it was fine to run the pulsewidths over 90%.
The other is YearsOfDecay, but he was running aftermarket fuel injectors that were not Nippondenso.
You might want to ask them what their direct experiences were.

Right now, the numbers of people running successful banjo bolts clearly outweight the ones that have had problems.
So, only two people have the right to bitch about it.
Everyone else is playing on fears.
It's funny they can't seem to swallow the fact that the banjo bolt DOES work - all they can claim is that it MIGHT be damaging your fuel system...

More details:
http://fc3spro.com/TECH/FAQ/pd.html


-Ted

 

i doing your parallel setup!

 

You don't get it. When you incite fears about mod that can potentially prevent a large amount of damage you have you back up your argument, not spit forth more theory and suggest some reading. I directly asked if can you say with proof that these fuel pressure fluctuations are harmful, way to dodge that one. Before you stand behind Mazda look at all the engineering mistakes they have made, hell look at all the engineering mistakes that all car manufactures have made. They are far from perfect.

I'm not saying the FPD doesn't serve a purpose, it obviously does or Mazda wouldn't have put it on the car. My question is; is it required for the safe operation of the motor?

The only reason im getting excited about this is because its not theory. FPDs fail and cars burn down. So people start using banjo bolts and uninformed people come along and say it will break your car. YES you are uninformed, you have no information to back up your claims.

 

There doesn't seem to be much debate amongst manufacturers.

No you don't "know" at all. Seriously, how common are PD-related RX-7 engine fires in the grand scheme of things? In my many years in the rotary scene, I've not heard of one in this country. Considering the number of people who are on the RX-7 forums I visit, there are very few actual incidents of fire. I'm not saying there's zero risk, and I'm not saying any fuel leak shouldn't be dealt with immediately, but stating that an engine fire in every FC with the original PD is inevitable is overstating reality quite a bit.

It is not one-sided at all. It's a few people vs. nearly every single automotive engine manufacturer in the world, not to mention numerous aftermarket suppliers. Actually maybe that is a bit one-sided...

No, I have never said that at all. Personally I don't see this doing much damage to fuel components, because I've seen nothing to back this up. What I have said is that the pressure waves present in an undamped fuel system will (at certain revs and under certain flow conditions) hit the injectors as they open, causing a variation from the proper fuel pressure. This will cause a variation in flow compared to what the ECU has calculated as necessary, meaning the wrong amount of fuel will be injected. This will result in either a rich (from a positive pressure wave) or lean (from a negative pressure wave) mixture. Under the right (or wrong) circumstances this could cause engine failure if you're already running right on the verge of detonation, possibly because of bad fuel or elevated air/combustion temps.

A new PD eliminates the risk of either fuelling variations or an engine fire.

 

Like I said Ted the pd failing can cause the wiring harness injectors clips to burn, I failed to include the paint. I don't deny that the stock pd can and has done this on multiple occasions. That's why I don't recommend the stock PD, I recommend an aftermarket one that hasn't had failures. As far as the problems with a banjo bolt, it is interesting to hear those. What is the correlation with the pulsations and the non Nippondenso injectors? Like I said I will continue to support an aftermarket puslation damper because of the engineering research mazda has done. They included it as a part of the fuel system to keep from problems relating with the injectors, and I am going to do the same on my setup. Like I have said my reasoning is to protect my motor and the components that effect it. I don't have proof because I don't have the money to pay for the SAE documentation that proves it. If you want it, go buy it yourself. So you're argument is that manufacturers make too many mistakes to be trusted. So why did you buy this car at all? I have already explained the purpose of the pulsation damper, if you don't believe it, than go find out. If you don't think that preserving the injectors and motor are good enough than by all means go ahead and run one without it. I'm sorry if my attempt to explain the worth and purpose of the pulsation damper has failed so poorly for you guys. I'll go ahead and tell mistubishi, ford, mazda and the rest of the car companies that have and still do use a pulsation damper that the research that they have done is insufficient and that they should quit wasting their money on installing a PD on their cars.
Do you have any information that shows that all the car manufacturers are wrong? That the pullses caused by the injectors aren't potentially harmful? Do you aside from the claim that people have used it without failure. If it serves no purpose than why have they been on cars since the 80's? Do you have information that aftermarket Pulsation Dampers fail so horribly so consistently that they are worthless as well? For the last time I have never said that the stock PD's don't fail, I have said time and time again that they have been known to fail. There are plenty of aftermarket PD's that don't fail. Is that so hard for people to see?

- Steiner

 

you know instead i think i will do that Parralel fuel system design that Ted has done looks very very nice, it also knocks out the fpr and PD so i like killing two birds with one stone. and theres more adjustability in that system. Ted, i think im going with you on this one

 

To say that manufacturers know everything and do everything the best way possible is hardly correct. IF so, we wouldnt have problems with the automatic sliding seatbelts on US spec s5 cars, 90* coolant hoses on t2 TB's, 75 vacuum hoses on FD engines, pisspoor electrical systems, radiators with plastic endtanks, and all the otherpoorly engineered crap that comes on FC's or cars in general.

I can count the s3 or s4 cars that I've encountered with the original PD that have NOT either leaked fuel or had the screw fallen out (ready to start leaking anytime) on one hand. And in 7 years, I've worked on or seen a good 200-300 rx-7s. I'll let you do the odds, but you're understating the facts. Just because you haven't seen many failed PD's doesnt mean I haven't. But, I probably see alot more 7's than you do, too.


Here we have it. Your theory sounds correct, and that's well and great...but I've never seen it in PRACTICE, nor have you. I WANT TO HEAR FROM SOMEONE WHO HAS EXPERIENCED A PROBLEM FROM THE PD ELIMINATION, not just theories about it or "what ifs". We can sit here and theorize that a meteor will collide with earth and cause the death of our species as a whole, but until someone shows me that happening then it doesnt make a rat's *** to me.

We have a few people who theorize that something bad *could* happen in the fuel system which *could* cause uneven fuel delivery which *could* be a contributor to blowing up an engine. And though it's possible on any ICE, this condition (if it were to happen) *could* only really affect turbo engines, and really then only the ones running considerably higher than stock boost. That's a lot of "coulds" to me...

And on the other hand you have some experienced people who've seen tens of hundreds of 7s and engines all of which had a PD that was either leaking or had the potential to leak very soon. And anyone can agree, even the skeptics, that once a leak begins you WILL have a fire in quick order, and furthermore they can agree that a fire WILL likely destroy your car, or at least cost you hundreds or thousands of dollars and tens of hundreds of hours to repair. And here we have a lot of "wills".

So would you rather worry about the "could" side of things, or do something about the "will" side?

Again, what it comes down to is:

-a good size group of people that have DONE it, and report no problems.
-a very minute group of people (see ted's post) that have DONE it and reported problems...both with highly modded cars in relatiojn to 95% of those of us on this forum.
-a good size group of people that HAVE NOT DONE the mod, and have no firsthand experience to relate, other than THEORY. Theory is great and all, and often explains things that can't be readily obvserved in life...however, for those of us with a large degree of experience in a particular field, we find that theory is often not dead on, and leads us down stray roads sometimes. By definition, to prove or disprove a theory, a lot of testing via the scientific method is required. Though no one here can say they've done this, a few of us see a lot of cars, and come closer to being able to say we have than the others who can only say they've dealt with 1 or 2 cases.

Again....if you're a whiner, a worrier, a purist, or (lets add one) a theorist about what might happen, then don't do the mod. Take your own chances. For the rest of us, we're here running our banjo bolts and never worrying about it again. Even a replaced PD can fail again.

 

This is all very funny...
Yes Ted I have run 90% duty cycles, when I had the injectors hammer shut duty cycles were the 60% range....
There is more than one car, out there that uses the same PD as the FC, I think its the 626 cars, any stories about those cars burning down..No...
The built in pulsation dampeners in the aftermarket FPR's might work for someone running smaller inectors, or something, but step to some really large primaries and they can't handle the oscillations, the needle vibration with 4x1600's is unreal, I am suprised the guage still works the way the needle was vibrating...The pulsations with the mallory fpr are less as compared to the malpassi, till I went to large primaries.... I was figuring at one time that running sequential might be the way around the problem or at least lessen the syptoms, but in further look at the gm systems, they are still using a dampener even in sequential systems..
Yeah my setup is way more extreme than most others, but the blown motor wasn't the only syptom, the chronic leaks on the fuel system was the first sign, having continuous o-ring problems was the pointer that somthing was going on there, the fucked injectors was the secondary problem that lead me to the answer...Running with no Pd INCREASES your chance of a fuel leak...
Until Rotary Resurrection can tell me why every efi car on the planet has one, he is the theorist...Max

 

I'm assuming then that you have alternative solutions to all this poor engineering, that would cost the same or less and perform the same or better. No? Then you shouldn't imply that you have a better idea about car design that actual car designers who have to design cars in the real world.

What I'd like you to explain is why does nearly every manufacturer fit a PD if they're not required? It's not something you only see on high-performance cars or expensive cars; it's on practically every one. Never mind about everything else in this discussion, I just want you to explain to us why it is you think there is an overwhelming consensus amongst the massive pool of automotive engineering designers out there that PD's are necessary. Then tell us your theory on why they're wrong.

You can add mine, since it's just fine.

Personally I find your numbers a little hard to swallow. If you're right, then nearly every person on this forum has a leaky and/or faulty PD. Are you saying we're all so dumb that we just haven't noticed this yet? All of us?

But I didn't ask about leaking PD's, I asked about actual engine fires. How many of those hundreds of RX-7's you worked on were on fire? Like I said above, I'm not saying there's zero risk, and I'm not saying any fuel leak shouldn't be dealt with immediately, but I want to know how common actual fires are.

 

How about this, big man. Every car on the planet comes with a stock catalytic convertor. Most come with an air/smog pump of some sort. As well as various vacuum solenoids, hoses, valves, and the like (there are tens of examples, varying from car to car). Now, we all know that aside from emissions testing, you can remove all this from an engine and itll still run perfectly fine...all you need is basic fuel delivery, ignition, and compression. That other stuff is just auxiliary stuff, an afterthought by the engineers, to make the car more friendly for a particular area's requirements, or for the everyday user's comfort. By no means are they required for the engine to run properly. By your logic, removing or tampering with any of those parts (PD included) will **** the car up. "Oh, can't take that air pump off, it'll **** my car up". But, we all know the reverse is true...thus, the THEORY has been disproven, by EXPERIENCE.

Again, there are those of us here with EXPERIENCE that have disproven the THEORY that a stock car requires a PD.

You missed my point. What I was getting at was that the factory does things that do not necessarily reflect optimal performance. They make compromises for creature comfort, emissions, safety, fuel economy, noise control, and greatest of all, cost. Don't you think that if a small company is able to manufacture aftermarket components as an afterthought for a given car, that a large manufacturer could do the same? Sure they could...but they can't afford to, and still sell the car to the average joe, and make it street legal for the country/state it's going to. So they make compromises...take off a little metal here, insert plastic for weight savings and cost. Put on a few extra parts here to help quiet the car down. Put on a few more extra parts here to make it run smoother when cold. Etc.

I wouldnt say they're wrong. They have to design things with LONGEVITY in mind. You want to know my THEORY on the PD? Here you go. I think that the thing is put in place for LONGEVITY of the fuel system components. They didnt want to run a risk of warranty repairs being required, which cost the company money. So they did everythign they could to engineer the car in such a way not to break, at least for a few years. To take some small amount of stress off the fuel system, they install a PD. This will allow the fuel pump, injectors, and FPR to live a longer life...by what span, nobody knows.

But, at this point in teh car's life, it's a moot point. The PD has now went from a beneficial part, to a disadvantage. IT can cost you your car in a moment's notice. What does it matter if an injector dies or a fuel pump goes out? It doesnt mean ****, it probably was about ready to go out anyway, due to regular wear and tear as a result of age and mileage. All these parts that the PD is meant to protect are available on the used or aftermarket market for $100 or less. But, if that PD does leak, it can cost you everything under the hood, and the hood itself.

How many times do you see users post on this forum: "I was thinking just last week about checking my PD to see if the screw was out, after reading a thread here. BUt, I didnt get time. Well, today my car caught on fire. Check your PD, don't let this happen to you."

Repeat monthly.

Yes, many of us on this forum have checked ours, but the majority have probably not given it a second thought. Every time an s4 car or engine gets brought to me I pull the cap off in front of the owner, show them the screw laying in teh cap, and explain what *can* happen as a result...they're always surprised.

I didnt say every one leaked. I did say that almost every screw was out of place. This is knocking on the door of a fuel leak. IT might happen tomorrow, it might happen in a year, it might take 5 or 10 more. BUT IT WILL HAPPEN, if the car is still in use at that time. S5 and s6 owners seem to be FAR less succeptible to this failure because of the updated PD with no screw to move, however it is possible for those to fail as well...my FD FPD failed earlier this year with 113k on it, the car is a 93 which puts it at 12 years old. Thing was squirting fuel about 6" in the air one day, the day before it wasn't. My bet is that anyone with an s4, with the original PD, will find a loose or fallen-out screw under the little yellow cap. I'd put MONEY on a 90% rate of the screw being loose or out on s4 cars. That's at least the rate I see here, unless the car has less than 100k miles on it...which is a rarity with these cars being 15-20 years old now.

I have worked on several cars that actually caught fire. Not nearly as many as the ones that had a screw out of place on the PD but hadn't yet caught on fire...Im going to say out of those 200-300 s3/s4 cars I've seen personally, that 10 were fire cars, and 150 or more had loose or fallen out screws, and of those 150, probably 50 had evidence of actual fuel leakage at the time I saw them. The only ones that weren't defective were either replaced (the replacements are painted a dull gray) or were very low mileage (75k or so).

I've got a box full of spare fuel rails and **** in the shop...guess what, none of them have screws in the PD. Do you think I took them out?

The point about other cars that use the same PD...I am aware of this. Why they don't have the same problem we do, I don't know. Perhaps it's because of staged injection we run, and the PD sees more pressure waves being generated in the rotary's fuel system. OR perhaps it's due to the extra heat they see on the rotary...they sit no more than 3" off the block, whereas on piston engines they usually sit 6" or more off the head, back on the intake manifold, on the opposite side of the exhaust (on an I4, anyway).

I don't know about the other cars, but I just know about rx-7s, specifically s4 cars.

 

Hydraulic hammer is a problem for any hydraulic system, not just engines. Even going into something as simple as construction, pulsation dampeners should be installed whenever a solenoid valve is installed, to prevent the water lines from blowing apart (my brother is an industrial plumber), which does happen with quite some frequency. Fireman have to ease off of their valves to prevent their hoses from exploding... are these really pressures that should be ignored? The fuel system on a vehicle is a precise device, and our engines are particularly sensitive to fuelling.

That being said, I have done the banjo bolt mod, and in higher powered cars, not been satisfied with it, and have since started adapting aftermarket pulsation dampeners.

With my experience in engineering, I can tell you these parts are installed for a reason: to promote engine and fuel system longevity, and they do their job. Automotive engineers are extremely pressured to minimize cost in order to maximize profits... if a part can be left out, it will be. If a part being left out "might" cause some damage to a few cars after 300,00 miles, its left out. If a part being left out will cause enough damage to negatively affect companies reputation and cost money in recall repairs, then it is kept.

Is it any conincidence that factory built race cars ALSO use a pulsation dampener? No one builds a race car for creature comforts or for passing emissions... they build their cars to win races, and to promote their vehicles. If this part wasn't required, it wouldn't be there.

I would not build a car for myself that did not incorporate a pulsation dampener in the system.

 

How about we leave childish sniping out of this previously civil thread? It ain't necessary.

This is a ridiculously simplistic comparison, and doesn't strengthen your argument against the PD at all. Emission controls are required by law, and in the greater scheme of things do a little bit to save the planet (maybe). Nobody has ever said they are necessary for the enigne to run. Nobody has even implied that removing them will "**** the car up" You've just made that up to try (unsuccessfully) to make a point. Every part of the car has a specific purpose, and removing each part or system has to be considered on it's own merits. Lumping them together like you did is nonsense.

I don't. The effects on mixtures from pressure waves in the fuel rails is well known. Most people try to avoid random mixture variations, and so do engine designers.

The benefits of having a new PD (stock or aftermarket) have not changed from when the car was new.

 

As usual, it's apparent that you're absolutely unwilling to even consider another point of view other than your own. I, on the other hand, have examined those points of view presented to me above, and discussed each one with my own opinions, so I can at least say that I've given them thought.

As I see it now, I might as well be talking to the wall. I guess the other readers, who don't have the time, knowledge, or desire to come out and get involved in a debate like this, can make their own decisions based upon the information presented here by both sides.

You've still never shown me a single stock or lightly modified streetcar (represents 95% of the population of this forum, which is most relevant to this discussion) that's had a verified problem out of this mod. Yet I've stated that I've had several such cars with*out* the PD that had no problem. I feel that I've presented proof to back up my side, and you've presented nothing but theory and conjecture for yours.

Enjoy the rest of your debate. I think I've made all the points that I can stand to for now.

 

ive been reading along with this whole thread and kept myself from jumping in once and a while, but sorry NZ, im with kevin, no one that states that the PD is essensial has given any proof that removing it will cause serious damage. yes removing it may shorten the life of some parts, but all parts are destined to break. nothing is going to stop that. even though i am still using my pd (which has been replaced by PO) if i still had the original or a leaking one i would probably do the banjo bolt mod. unless you have proof that removing it will GREATLY shorten the life of the other parts i dont think you would be able to win this debate, in my mind anyway.

 

Funny, I was thinking exactly the same thing. You also appear pretty firm in your opinion. It's a bit insulting however to assume that I have not considered any of the opposing points presented or given them any thought. I would've hoped you'd credit me with a bit more intelligence than that.

I've never said it was essential, I've said it was beneficial. Under certain circumstances there's a risk of briefly lean mixtures, which should always be considered risky. But since you don't think it needs to be there, can you explain why every car has one?

That's not my argument. Never has been.

See above, then go back and read what I actually wrote.