Awesome work Charles.

 

so I came across this thread when doing research for putting together my return system, just wondering if I should address possible dampening issues before installing the kit and getting tuned.

I'm currently running vortech with 3.13 pulley and ID725 cc injectors on a stock fuel system (well modified for walbro 255 pump)

I'm going to be adding 2.87 pulley, rails, aeromotive 1000 and all -6AN line back and forth, also needless to say I will be getting retuned.

My questions are:
does it matter if I run the incoming fuel to the front or rear rails? is one way preferred?
should I be worried about dampening at my hp levels (expecting 400hp on mustang dyno)
I'm guessing the need for dampening is more prevalent when running higher duty cycles? or is it just larger injectors..?

 

1. I assume you mean "to the front or the rear of the rails"? I would say no, it doesn't matter. Front would probably be better so that lines from the rear of the rails to the FPR can be shorter (the FPR is also a damper, so the closer the better).

2. The need for damping is completely independent of horsepower

3. The opposite. Its more prevalent at low duty cycles, because the pulse widths are shorter and the resonance has a greater impact. larger injectors would in theory make this worse, because they will require even shorter pulse widths at low loads. Then again, shorter pulse widths may reduce the resonance caused by the injector opening events in the first place, or at least change its frequency so its hard to say. At the end of the day, you can't really have too much damping, so get the new CJM rails and be done with it.

 

mx594 is spot on. I second his suggestions.

 

hmm, im having this issue too w my CJM Stage 0 kit.. subscribed.. will ahve this checked out soon.. i have none of the data like what is posted here, but i know that taking off from a stop light, the car feels like a plane falling out of the sky for a moment at 2200-2700 rpms.. and only when accelerating froma stop or rolling slowly in a parking lot.. emailed Charles, talked to my shoas well as some members in the thread..

 

Has anyone experienced this with the stock dampers in place? I'm running GTR injectors, DW200 fuel pump and the rest is OEM 04.5 DE fuel system and I have this lean spot as well. Do the dampers just go bad after a while? I've considered adding a third damper, but the lean spot is on both banks, despite the original damper being present on bank 2. I guess it doesn't bother me if I have to replace them, considering how repair-free this car has been in the 10 years we've owned it.

Toyota thread-in dampers are a dime a dozen.. Maybe there's room to hang a pair of them off the front ends of the rails? Brazing fittings on wouldn't be hard..

 

I haven't heard of the OEM dampers going bad. Do you have a log of your issue? A lot of people have lean spots that they blame on this that are actually tuning issues. I haven't heard of someone on here having a lean issue with the oem dampers and rails in place. That's not to say it "can't" happen but it is very unlikely. There are very specific areas that go extreme lean and it is all within 100rpm of what is posted here and always in the 3 spots.

As for the damper going bad it is a wear item so it could go bad just very rare. I guess I can dig through some of my old parts and see if I can find any of the ones I have from rail installs. You can have it for the cost of shipping if you like. Just let me find it first. Hit me up through email jeffbinder@gmail.com I wo'nt be back home until sunday to look in the garage. After 3 moves there might be a chance they were lost.

 

Here's a log, pretty sure you should be able to see it... https://drive.google.com/file/d/0B-d...it?usp=sharing

The issue I have is at 2250rpm (and less so at 1100rpm), and it just surges lean up to about 20:1, then clears up as I move out of that range. It's definitely a harmonic issue. Wider throttle openings/longer pulsewidths make the spot less noticeable. I can watch the airflow curve through that range and it's smooth, pulse widths are increasing linearly through there as well (a plenum leak would show up as a flat spot on the MAF). I've "tuned" around it in the past by spiking the MAF curve for the voltages where this is happening, but in the logs you can see the duty cycle increase with very little effect on AFR in that particular area. I tested the plenum for leaks and got nothing. Even the 20% fuel added in the comp table isn't enough to compensate..

Like I said, the driveability can be brute forced by dumping fuel with the MAF, but that whole section of the map then runs pig rich around that area (and I have an emissions test in a couple months). It's probably not as bad as others have had without the dampers, but it's definitely there and noticeable.

I'll definitely take you up on the offer if you still have them!

 

Has it always done this? Did it start after any recent changes?

trying replacing the dampers with fresh ones from Nissan and see if the problem goes away.

 

It started when I swapped the stock injectors for GTR injectors, which at 51psi test out to about 590cc/min. I was able to tune the rest of the map pretty quickly (uprev), but there was that one nagging spot. I tested the intake/plenum for leaks and found none.

I initially did some research and found that the STi guys seem to have similar resonance issues with their fuel systems and figured that was probably what was going on with my car. It made sense given what I knew about what was happening: Narrow rpm range, airflow was linear through the range, wider pulse widths masked the issue, etc. I had no idea it happened to these cars until I stumbled on another post by accident and he mentioned "that" lean spot. I had searched, but never found the right terms to use to find anything useful. I never had considered fuel dampers as wear items, but I'm at about 96k miles and have had the car for 10 years now so who knows...

 

Ya, it does kind of sound like a resonance issue with the way you have checked things over. The only thing I would be concerned with is if the resonance issue is within the fuel damper or possibly those injectors.

Check bank to bank and see what the injectors are doing and what the a/f is doing. I know at certain rpm the flow in the plenum gets pretty weird and only effects a single bank. If you only have a single wideband it would be hard to see this. So one bank could be going lean due to airflow but then the tuning would be dumping fuel in both banks so the total a/f on a single wideband would show rich while 1 bank still being lean or stoich.

When mine had an issue the car would buck hard at that lean spot and it was lean on both banks exactly the same amount.

I just got back from colorado so this week I'll try to get into the garage and find some dampers.

Send me an email at Jeffbinder@gmail.com to remind me to find them for you.

 

Email sent.

Both widebands show AFRs moving up into the 17-20 range, though bank 2 seems leaner than bank 1 under that condition. I don't think it's as bad as people have had without the dampers, but I'd rather solve the problem than try to tune it out.

 

Here's a look at an OEM GTR (injectors I'm using) rail setup:


There are 4 dampers total (or 3 and a FPR?). I think part of the issue is running the rails dead-headed and part of it is the lack of rubber in the system. It seems a lot of OEMs had resonance/noise issues when they went to the harder nylon line systems. The dead head on the forward part of the rail very efficiently reflects the waves produced by the injectors opening and closing. Notice the GTR rail links the two and gives those waves somewhere to go instead of reflecting and becoming standing pressure waves with the antinodes sitting right at the inlets of the injectors. There's also some swell to rubber hoses- even braided ones- that doesn't exist in hard lines. The subaru guys found that they could minimize the resonance by adding a few feet of rubber hose into the system (not an ideal solution, but whatever).

I can't find a schematic of how the OE fuel system works on the R35, whether it's a return or returnless, so I don't know if that's two feeds (I know it runs two fuel pumps) or a single feed and return with the rails in series. Either way, the amount of damping on that OE system is crazy and it suggests they had similar problems with these particular injectors.

If new dampers don't solve the problem I'm not sure what my next course of action would be. I think connecting the front ends of the rails would be very beneficial, but there isn't much room to do it. I suppose I could have some -4 or -6 ends brazed on and connect them with some hose.

I've also found that the later model 06+ VQs in the altima/maxipad/quest run the newer style dampers with one on each rail and a 5/16" quick connect:

I could keep the stock feed/damper, braze on a -6 fitting to the outlet of that and use a mocal -6 quick connect fitting and the spare hose/fittings I have in my garage to run the newer style rail. Mostly just thinking out loud..

 

The GTR runs twin pumps in the tank and a single 3/8 feed pipe to the engine bay.

The GTR has 1 damper on each rail, and a damper on the return line just after the regulator.

Then a 5/16 return pipe.

Eliminating the dead ends on the rails didnt prevent the aftermarket for the VQ35 from having to add dampers directly on-board. YMMV. Hopefully you find that a fresh stock damper solves your problems.

http://shop.cj-motorsports.com/media/derails1.jpg

 

Following up on this.

Binder sent me his old feed damper and I installed it as a third damper on the passenger side rail. Without touching the tune the lean spot is 100% gone. Drives like a new damn car, haha. Time to go get it smogged then put the test pipes on.

 

You should post a picture of it. Your setup was actually a simple yet genius idea.

Also, boostedperformance (sasa) on here welded 6an male fittings to the front of the oem rails to connect them. That will help with overall pressure in the rails if you wanted to do it.

 

I cut the feed line to the passenger side rail and installed the feed damper Jeff sent me on that rail, then connected the inlet to the damper to the feed pipe with 5/16" ID EFI hose and EFI clamps. I flared the feed pipe slightly so the clamps would have something to bite onto.

I don't think I'll need to go that far. On really big injectors maybe.. So maybe when I pop this motor and ditch the Vortech for twins

Thanks again, I was really worrying I'd have to do something a whole lot more inventive to fix this.

 

Finally had time to make this fix.
I can't drive the car now since I have no winter tires, but it seems like it worked. Now the engine revs smoothly from 1000-redline without any hesitation. Previously it stopped @2300 rpm and 4000 rpm or something.

I'm so happy. Thank you all for your help!!!
Big thanks also to CJmotorsports!

Here is a pic I took. It's still missing the new damper in the picture.