Fuel pulsation damper - nessesary with altered fuel system?

[SLPR]

Excellent forum hopefully I can find the person with some insight to my questions. I did not see any information relating to my post in the past threads.

In common rail (gasoline) fuel systems there are usually pulsation dampers designed in the system to decrease pulsations inside the fuel rail with may cause fuel suppl;y problems (lean conditions) under heavy cycles.

My question: (two parts)
What if any would be the effects of removing this damper from the system all together? If I would run into ill effects how could I test for it? Any thoughts?

What if the fuel system has been highly moddified?
~fuel injectors changed from 230cc to 550cc
~increased fuel feed lines and return lines
~much larger capacity fuel pump

I'm just looking for some opinions from some experienced fuel systems engineers/designers/etc. Most people I ask say to simply eliminate the damper, but I don't think that is a good enough answer if it's not backed up by some fact.

Thanks for your time,
SLPR

 

[SLPR]

As far as I know.....
Taken from the internet: "The pulsation dampner "damps" pulses from the fuel rail, a mini gasoline shock absorber. As I see it, this allows the fuel injectors to see an ABSOLUTELY constant fuel pressure. Without a damper, the injectors could fire at either a pump pulse or the time in between, where fuel pressure would be higher or lower. Higher or lower fuel pressures would allow minute differences in air fuel ratios, and with the engine running at the very edge of it safe level, you "could" go lean...."

SLPR....

 

[GregLocock]

Slight variations in fuel pressure, and hence delivery, will have their biggest effect at idle. Since idle instability is a big customer concern, but is purely a subjective issue, my /guess/ is that you won't hurt your engine by leaving it off. But it is your engine, not mine. Cheers

Greg Locock

 

[WGJ]

Your reference to "common rail" I take as meaning the fuel rail which exists on all electronically fuel injected vehicles, as opposed to older, mechanically injected systems.
In my automotive experience, dampers, as opposed to pressure accumulators, are included in systems primarily to control the noise induced in the fuel system due to the opening and closing of the injectors. Injector operation noise is most noticable at idle and light load low engine speeds. As the injectors open, a low pressure wave in the fuel moves back down the fuel rail and into the fuel line. If the line has been clipped to the body at a place where the body is receptive to vibration (an un-stiffened bulkhead or forward floor panel for example) the pulse in the fuel line is then radiated as noise by the panel.
On some vehicles I have worked on, the idle noise was described by some as a 'helicopter noise', that is, akin to the thumping noise of the rotating 'copter blades.
Adding a damper to the line between the rail connection and the first body clip usually solved the problem. The damper absorbed the pulse, not the body.
Where a simple damper is mounted on the rail, it may have been put there to help with standing waves set up in the pressurised fuel under certain speed/load conditions, which might have the knock-on effect of making the closest injectors rich or lean, depending upon the character of the standing wave.
However, as you've already said, Purchasers in the big automotive companies won't buy anything that's not necessary and the existance of standing waves in a fuel rail is something that most people wouldn't experience or be too concerned about, if the rail was anywhere near being well-designed. Such phenomena would need steady-state operation to set up and that's just not the sort of operating condition most cars experience.
Going back a while, rubber hose was used in a lot of fuel systems and this had an in-built damping quality. Once the car manufacturers went over to the nylon family pulsation noise problems occured everywhere. Fuel system manufacturers developed a range of dampers for different positions and problems, Bosch and Walbro for example.
I remember inspecting a BMW 5 Series one time which had three separate dampers on it - one after the electric fuel injection pump, one near or on the fuel rail and another in the line from the underbody lines to the rail. Very quiet.

 

[SLPR]

Hey thanks for the information WGJ that is pretty much what I found out by consulting with some other fuel system engineers. Your point about rubber fuel line having some built in dampening characteristics is something I have not thought of yet. It makes perfect sense.

I decided to go on with my fuel system build without the dampener for the decrease in flow restriction (banjo fitting restriction). The chassis running fuel lines (hardline) are being replaced with SS lines (teflon inner liner). I'm figuring that I won't have any issues with the absence of a dampener. Noise/vibration is not a concern of mine either. Besides I will be able to counter any issues with some engine control adjustments.

Thanks for all the help guys!!!!