ddub

I still want to know why the Mazda training manual says its for absorbing sound then, and doesn't mention anything about pulsations in the fuel

I've heard it quoted on this site a ton of times, but I've never actually read it in an article or manual put out by a car company. Maybe I'm not looking hard enough?

HAILERS

Do a Google Search for WATER HAMMER and fluids. OR ask the guy with the convertible that lives in NZ.

Water hammer as in being in a old house and turning the water on and off rapidly and hearing the pipes rattle. That is the effect of the *water hammer *. A valve opening and closing rapidly. Much like a fuel injector opening and closing rapidly. You can ruin a pressure transducer if there is a *water hammer * effect in the system. I figure that effect does the fuel injectors no good at all. http://www.omega.com/techref/waterhammer.html a pulsation damper would be the equivilant of a Snubber.

Sideways7

iTrader: (7)

Even a stock rotary puts off much more heat than a corvette. The only car I've seen that puts off similar exhaust heat to a turbo rotary is my uncle's 935hp 12k RPM Testarossa. I've also heard of people melting glass-packs in a matter of weeks.

RXSevenSymphonies

iTrader: (2)

Interestingly, in my Automotive Fuel and Emissions book, pulsation dampers are never mentioned anywhere.

NZConvertible

That's why I don't think noise is much to do with this. If you can't hear injectors with the engine running, why spend money trying to quieten them? Manufacturers don't spend money unnecessarily.

If it's inaudible noise, then it's not an issue is it? Pressure waves in the rail is an issue.

It's not theory at all. Car manufacturers do not install parts based on theory. They do it because many years and countless dollars of R&D has proven a need. I did a search on the SAE website for papers that included the terms "fuel", "pulsation" and "damper", and amongst the 121 hits were these interesting sounding titles:

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These papers are not "theory". They are written about actual testing and practice. That last one actually mentioned noise, which is interesting...

Of course it can, but so what? That applies to any part on the car. What are the realistic chances of a 3yo PD failing? Or a 10yo one? I don't see any evidence that even hints at new PD's being a risk. It's safe to say that statistically you've got more chance of crashing your car and being injured. But you still drive it don't you?

If you're going to put your 2c in, at least try to use some semi-serious numbers. 20% risk from a new PD? Utter BS. How many PD failures do you know of that occured in say the first ten years of the vehicles life? Millions of people with banjo bolts? Seriously, there's probably only a very small percentage of FC's out there that have actually had this done.

I really don't care if anyone chucks out the PD in their car. What annoys me is all the poorly thought out, innacurate and plain ol' dodgy engineering explanations people come up with, not to mention all the "certain doom" scaremongering. I wish people would just admit they do this because they don't want to fork out for a new part. That I could sort of understand...

BTW, there are lots of SAE papers written about the rotary, many by Mazda that cover specific developments over the years. I've read a few and they're fascinating if you're into the engineering side of things. These can be posted to you or downloaded in PDF format for US$12 (non-members) if anyone's keen.

RXSevenSymphonies

iTrader: (2)

Dammit I would download those but I don't have money.. I hate money (need a job). You should send the PDF's to me in an illegal manner. Yes part of the reason I replaced the PD with a banjo bolt was because of the money, and also so I don't have to worry about it failing. But if I determine that it's a necessary part I'll definitely pay the money to have it right.

This could be what Mazda means by sounds:

"The pressure spike(acoustic wave)created at rapid valve closure can be high as five(5) times the system working pressure.

Unrestricted, this pressure spike or wave will rapidly accelerate to the speed of sound in liquid, which can exceed 4000 ft/sec."

http://www.plastomatic.com/water-hammer.html

NZConvertible

I haven't bought any either, I just found a few uploaded to people's sites.

The water hammer analogy needs to be used with great care, because it applies to closed systems, i.e the flow is shut off completely. This is not the case with EFI, since fuel is always flowing through the rails and out the return line. The pressure spikes aren't going to be anywhere near as high, but they're high enough for nearly all car makers to fit a damper. The pressure waves do travel at the speed of sound though.

RETed

I wish people would stop associating "WATER HAMMER" with pulsation damper. :P

As NZConvertible already stated, it's NOT a dead-end.
The analogy with water hammer is not a fair comparison.

Also, the FUEL PRESSURE REGULATOR acts as a pulsation damper.
A FUEL PRESSURE REGULATOR *is* a pulsation damper with a bleed.
So you're not totally eliminating all components that minimize the fuel pulsations.

The primary fuel rail is SHORT, and the primary fuel injectors fire sequentially.
This makes it virtually impossible for fuel pulsation to affect the primary fuel rail / injectors.

If you want proof, install a fuel pressure gauge and see for yourself how much the needle bounces...


-Ted

RXSevenSymphonies

iTrader: (2)

Yea that's what I was going to bring up next, so I suppose this is why people can use a banjo bolt and still get by with no noticable difference, or even measurable difference using wideband o2 according to Reted I believe. So what really is the significance in having the damper then.. just to gaurantee as accurate of injection pressure as possible at all times? But then I keep seeing that these are pressure spikes, so if anything you'll be randomly injecting slightly more fuel, never less fuel? Or is it to protect the fuel pressure regulator from damage from pulsations?
As it mentions diaphrams on that same site "Damage to seals gauges, diaphragms , valves and joints in piping result from the pressure spikes created by the pulsating flow." Then that could be why the pulsation damper fails because it's taking the damage and eventually the diaphram can't take it. But without it, it would be our fuel pressure regulators failing?

RXSevenSymphonies

iTrader: (2)

Good time to chime in RETed

RETed

This really has been answered all previously.

IME, stock or near stock fuel systems seem to have no problem running a banjo bolt and eliminating the stock pulsation damper.
Aftermarket (with stand-alone EMS') have run into problems with possible pulsation affecting fuel delivery.
This is ESPECIALLY true of stand-alone EMS' that run BATCH FIRE fuel injection (i.e. Haltech E6K / E6X, etc.) that makes this problem worse.

Mazda is not exactly the more reliable auto maker out there.
Have you ever heard of a Toyota or Honda pulsation damper failure???
Nuff said.

You realize that rubber hose also acts like a pulsation damper?
There's is enough of it in and around the fuel rail to handle stock or near-stock applications.


-Ted

RXSevenSymphonies

iTrader: (2)

ah, really? I thought I had read pretty much every pulsation damper thread on the forum.. I've heard a lot of the stuff before, but some of this is new or more in-depth, or I just didn't remember it. I haven't seen you talk about batch fire before. Fuel pressure regulator and rubber fuel lines absorbing pulsations, I have heard that.

RETed

You did read my FAQ page, right?
http://fc3spro.com/TECH/FAQ/pd.html

I'm just waiting for all the pro-PD people to starting adding their 2 cents.

I'm heavily biased against PD's, and running an aftermarket FPR eliminates the need for one - SX Performance even explicit states it's not necessary to run one if using their FPR.


-Ted

RXSevenSymphonies

iTrader: (2)

Yea I was looking on your site for your write-up on them, but I looked too fast and didn't think to check under FAQ.

RETed

I know I mentioned the word "batch fire", but it's the same as "multi point".
The old timers understand this, but this can be confusing is you're not familiar with all the fuel injection talk.


-Ted

RXSevenSymphonies

iTrader: (2)

Alright, after reading your site that makes some things clearer. I noticed you say "Below are GIF animations of the Zenki and Kouki pulsation dampers under operation. " but then you no longer have them there, did you lose the gifs that time you lost your site? Because I saved them a long time ago and I can send them to you.

RETed

No ****???
I've been trying to get those damn things, cause I was just linking them straight to offsite!
They were great animated GIFs on how the PD's work.
Can you send them to me through email?
reted_2000@yahoo.com
Or else, drop me a link?


-Ted

socalrotor

iTrader: (1)

I replaced a FPD in 3 hours...at night.......not as hard as it seems....hardest part will be separating the UIM from the lower... IMO noise is not an issue when it comes to FPD. The mechnical funtion of the FPD is to dampen the pulses in fuel presure @ high RPM. I asked rotarypower jeff, he said the banjo bolt is a no no . Jeff said it can cause drivablity problems that are a bitch to track down. IMO why would mazda manufacture the rex with a $100 dollar part if all it needed was a 50 cent banjo bolt? They must of found out they needed it when the R&D the S4, @ millions on top of millions. i find it alittle scary to think that we know better than Mazda. BTW just my 2 cents on the matter.

NZConvertible

So what about when the secondaries are firing too?

The pressure pulses caused by the injectors opening would never be seen on a basic pressure gauge. You need lab type equipment (pressure transducer and oscilloscope) because of the speeds and times involved.

So why did Mazda install one?

Look at where the PD's are positioned. Piston engine fuel rails usually leave the PD in a location that allows far more ventilation than the PD on a rotary's primary rail. Over time the Mazda PD is going to be affected by heat far more. I've mentioned before that I've not heard of anyone over here experiencing this leaky PD problem. Most if not all of the 13BT's over here are J-specs and have the PD on the secondary rail, where it's unlikely to be affected by heat to the same degree. Maybe there's a connection.

You won't see any difference with wideband for the same reason you won't see anything with the pressure gauge mentioned above. It doesn't react nearly fast enough.

That's a big part of it yes.

The pressure pulses are both positive and negative.

RXSevenSymphonies

iTrader: (2)

hmm interesting interesting, alright so why did Mazda switch around the fuel system for the U.S. version?

ddub

So they'd fail, after the warranty period of course, and fry the harness/other parts and people would hopefully come to them to buy the new parts and fix it. It's all a scheme.

Or maybe I'm just cynical..

NZConvertible

Ya think?

I have no idea why they're different. I can't think of any reason why they'd need to be.

RETed

Mazda spent millions on that K-M rear hub with the DTSS.
So why are people spending $40 for the eliminator kit just to "undo" all of that?

Mazda spent millions on the AAS.
So why do we throw them away and just get regular replacement shocks?


-Ted

NZConvertible

Because you can't replace the worn-out bushes without buying a whole new hub, so it doesn't make economic sense.

Same again. Have you seen what those shocks cost from Mazda? They quoted me NZ$750 (~US$530) each for the ones in my HB Cosmo. The adjustability was nice, but when they wore out I replaced all four of them with conventional shocks for the price of one from Mazda.

But I think you knew all that...

RETed

Hmmm...so $10 versus $100+ for a brand new OEM PD from Mazda...more for the S5 one cause it's integrated into the fuel rail.
The banjo bolt will never fail; too bad the same can't be said of a replacement PD.
I call that good economic sense.

Yeah, I assumed you knew that too...


-Ted