Well, Nissan put it there for a reason. And they even added a third damper on the HR. So you are just asking for trouble by removing it.

I installed the new adapter this weekend. I have not done any serious data logging yet, but from driving the car for the last three days, it seems as though the little stutters I would sometimes still get around 2000 and 3000 (on the tach, so actually like 2200 and 3200) at very low loads are gone now. When I get a chance, I will try to take a datalog and see what the A/F trace looks like now.

But for now I am happy with the way it is running and I have done all I can, short of adding a third damper. I am going to leave it the way it is and move on with fine tuning (on a dyno) probably in the spring. I just got a Haltech dual wideband and an IQ3 dash so I am going to install those over the winter.

If anyone is interested, I may be able to produce a limited number of the adapters, now that the CNC programming is all done. PM me.

 

I posted a few links to aftermarket dampers, so I might have to revisit that this fall. I'm going to go with CNG injectors later on, so I probably wont put too much effort into this until i settle on the final fuel system.

 

I’ve got a similar issue at roughly the same RPM, I’ve had the car retuned since so I’m pretty sure it’s not related to my tune… it was actually a lot worse in 1st gear but I tightened my fuel pressure sensor and that got rid of a lot of the problem when the car is warming up, but after 10 minutes of driving it shows up again.

Did you ever find a solution to your issue?

 

no solution yet. i'm gonna look into it more this winter.

 

when get under my intake manifold next time, we are going to try a fuel line update. going to run the feed lines to the front of the rail, and use much shorter lines off the back of the rails to the regulator. should help the regulator dampen. going to build it on my car, but probably just ship it to you to try it since im parting out mine anyway.

 

Thanks for the update.

I’m starting to get used to the hiccup…I think I’m going to tear my intake manifold apart next week and glance over everything then send the injectors out to get tested.

 

Do you have a damper?

If I ever go to a higher flowing fuel system, you can bet your a$$ I am going to machine some custom adapters to mount at least one damper on each rail!

 

So if I've read all 9 pages correctly... the only people having this issue have return systems? I'm trying to help a friend with their 05 turbo'd G (Osiris tune) and with a modified stock system (same as the OP used to confirm the problem with the modified system, winny bro and all) they are still having the ~2400 hesitation. The car leans out to ~ 17:1 on their PLX and the wideband 02's confirm this when reading the Osiris logs... the car can be tuned so that it will run ok but then it runs really fat at idle and cruise speeds... any help is greatly appreciated. It seems almost impossible to get it in closed loop... is it possible they messed up the stock regulator when modifying it and that's the problem?

 

OEM dampers have a tendency to go bad...might be worth replacing them. On a lighter note I have a return system with all dampers deleted and other than the annoying injector noises the A/F's do not spike anywhere.

 

My hesitation issue was completely gone before my engine bent a rod… it’s a shame since I only had a 1,000 miles or so with no hesitation, lol; I didn’t change any parts on my car, just tuning. Also, I do not have a return fuel system.

 

I don't understand why one cannot simply insert a fuel dampener inline with the feed lines to the rails. I know space is tight - is that the only issue or do they restrict flow? Maybe where the hard line ends? That's probably too far away from the injectors to dampen the effect of injectors closing and opening. Perhaps using oversized, low latency injectors is another mechanism to minimize the pulses (and this is why my HKS 1000 cc injectors in my CJM stage 2 cause only minimal lean spikes ). It was kind of a pain to tune out, but with 100 rpm resolution below 2k rpms, it's possible.

 

I have the same injectors and pretty large spikes. It sucks. Once i get it all back together i'll mess with finer tuning to see if maybe i can get it to go away but it was odd that i never had a single issue with lean spikes (we're talking 18afr spikes) until i put in my twin pump setup. Before i had a cjm stage 0 which kept use of 1 of the stock dampers.

 

I'm VERY close to taking the plunge on some of the Marren dampers and making them fit as the lean spots are annoying the crap out of me! I've taken the measurements and although it will be pretty tight with the T pieces in place I think it will fit. Would need to get replacements for the two small lines that go into the Y adaptor though as I don't think they will reach.

I spoke with Charles just a few days ago and in the next couple of weeks he's going to try re-routing the fuel lines to the rail so they are fed from the back hoping the Aeromotive damper will damper the pulses.

Matt

 

I think that will help, but will that really be easier than adding a dampener inline?

http://www.injector.com/cart/pc/view...3&idcategory=4

 

that looks perfect and should fit on our rails. I wil check the clearance between the rails and plenum sometime this weekend.

It sucks that it's 114$. That's 228$ for the package of them. I'm wondering if i can add the T fitting between the 2 return lines and my FPR so it will be sitting right on the firewall. Plenty of room there.

 

i redid my fuel setup like how Charles suggested. out of the back of the rails to the FPR. so we'll see if that makes a difference.

 

I would try the Merren dampers if I were you. Or find a way to reinstall the stock damper.

 

when will you have your stuff back together?

how much was your cost in making the new lines? I assume with the lack of flexibility of those lines you had to make new supply and return lines for the setup.

 

who knows when it will be back together. LOL

I wanted my fuel system to fit better so i just redid everything. Probably have a grand or so into the new lines and fittings.

 

the problem with adding a damper inline isnt that its difficult, its that its difficult to do CLEAN and simple. Making it even more of a pain in the butt, is the 1/2x20 thread (-5) of our fuel rails, and the lack of variety of fittings for it. every single way i have thought of adding the stock ones to our rails using already available fittings is just too messy and bulky, and thats how i feel about the Merrin ones also.

Since this is a problem that seems to effect less than 1% of cars with RFS, i believe that just about any change of the dynamics in the layout can probably have an effect. The only other factor here, is that this could be a witch-hunt. Since "mx594" is the only person to ever add a damper to a RFS, at this point its too early to say for sure that fuel pressure pulsations are even the problem that some of us have in common.

I think that the line swap is probably the best bet. After all, having the front of the rails lead to the regulator is quite a long journey back, and its not going to allow the regulator to do much dampening or respond to it quickly enough.

Now that winter is coming to an end, I can get my 350z out of storage and over the shop pretty soon. We are going to take off the intake manifold and everything, and that will be the perfect chance to size up the flow reversal hoses.