Jay Wellwood

Having seen setups with both conditions - anyone have any specific insight on this topic?

Looking at building a custom fuel rail using as many off-the-shelf products. Right now I'm inclined to use one as it's already in the plumbing.

Dave951

I was pondering this same question today thinking about the fuel damper. I think the main reason people choose to dump the damper is to eliminate the damper jumper hose. The whole purpose of the damper is to smooth out fuel pulses "waves" of flow to the injectors. In extreme cases its supposed to cause an injector to fail.

Now a lot of fuel regulators these days like Aeromotive ones have a damper built into the regulator function.

Direct from the Aeromotive people:

"The Aeromotive bypass fuel pressure regulator works to dampen pulsations and create a smooth, stable pressure. That is how it regulates. Given a correct installation, with recommended flow path through the fuel rail and to the regulator, and mounting the regulator close to the fuel rail outlet, there will be no need for any additional “damper”."

So therefore if you are running one of those you can remove it with little effect.

Tom M'Guinn

Use a damper. It helps prevents the pressure from jumping around (so more consistent tune/AFR). And if you plan to run an 044 or similar pump, it helps (but doesn't eliminate) fuel line knocking...

thomasmryan

it was removed on the 968 with the addition of sequential injection.

Jay Wellwood

Good to know...the 044 pump will be in the system. Do you know if this 'knocking' result in visible movement/jumping of the damper return hose? Reason I ask if I've come up with a hard tubing method to replace the hose from the damper to the fuel rail.

I've moved a step back taking the 951 upper-end approach for the 968 Turbo. Based on this, I've pretty well much duplicated the fuel system at this point.

Tom M'Guinn

See a very long thread on the subject here. Bottom line is that different cars seem to have different issues. For me, I isolated the hard lines under the car with more compliant bushings to eliminate the pressure hammering I had. Scott Gomes reports in that thread that removing the damper eliminated the noise on a car he worked on -- and I'd never question Scott's opinion/results -- but when I tried removing the damper on my car the knocking got worse.

https://rennlist.com/forums/944-turb...se-survey.html

Jay Wellwood

Thanks for the thread Tom...great discussion.

odonnell

This is a key concept.

Jay, if you're going to run batch fired injectors (i.e. what 8v cars did) you may benefit from the damper... when all injectors fire at once, there's going to of course be a relatively large pressure dropoff. With sequential (or semi-sequential) injection, this is not really an issue because only 1 or 2 injectors are firing at once vs all 4.

Then again, people run their cars in batch fire without the damper and a lot have reported no ill effects. Probably all depends on the pressure dropoff, which is a function of how much fuel you're flowing and the fuel rail pressure.

With a 968 DME or aftermarket ECU, you should be going sequential provided you wire up the hall sensor.

Jay Wellwood

In my setup I'm using the 951 ECU/KLR with the M-Tune, not the factory 968 setup.

I have no idea how the M-Tune controls the injector firing. Using the 3 bar AFPR and the 044 pump.

odonnell

Batch fire. The factory harness is wired so that 1 & 2 and 3 & 4 are wired as channels. They more or less fire simultaneously. Even if you re-wired the injector harness so that each injector driver controlled them as 1 & 4 and 2 & 3, the DME logic would have to be reworked to offset their firing, probably not worthwhile (even from a performance standpoint, batch fire does the job fine).

FWIW I went to semi-sequential injection on my NA and I got a noticably smoother idle and low RPM response. But it's not a change I would make just to delete the fuel damper, it was because "I'm making a new harness and using a standalone so why not" along with similar decisions, like wasted spark and fan control. Niceties more than life changing features.