thatv35guy

iTrader: (1)

So, I’ve nearly resolved my idle issue and now I’m trying to tackle the next drivability issue.

I’ve had issues with hesitation at cruising speeds as long as my car was boosted, my fuel system consists of just the Deatschwerks 600cc injectors and a Walbro 255lph fuel pump, the car is running the factory return less fuel system. The only other modification to the fuel system is a ProEFI fuel pressure sensor; the sensor is on the fuel feed hose/damper with a CNC adapter.

I was wondering if the fuel pressure sensor and adapter could cause the hesitation? Any thoughts?

Thanks!

G3po

iTrader: (8)

My setup is pretty similar , but with a DW300 pump and MTM.

I had a flat spot around 2400 rpm also. It was too tough to tune around so the way I resolved my issue is with this placement.

a) fuel pressure sender on passenger side via an AAM tap block with OEM damper on the back.

b) used an extra OEM main damper , the one with the inlet hose , cut off the hose and mounted to the passenger side rail.

c) cut and flared the OEM hard pipe (a few inches after after the OEM inlet braket.

d) connected high PSI hose between the flare and the new b) damper.

The reason I put the sender on the driver side ,side it is at the end of the chain and hence most likely to allow observation of any the worst case psi fluctuation.

End result , I have three total Dampers , no psi instabilities or flat spots.

thatv35guy

iTrader: (1)

You wouldn’t happen to have any pictures of your setup would you?

thatv35guy

iTrader: (1)

This is a long shot… but would HR or 370Z/G37 fuels rails fit a DE?

G3po

iTrader: (8)

Not with me , but from the diagram you posted.

a) I use the AAM adapter (shown bottom right) on the rear of my driver side rail with the OEM damper and my fuel sender

b) I use an extra feeder damper (circled in read) , with OEM hose removed , on the rear of the passenger side. I bought a new one and hacked it.

So fuel flows ( passenger to driver side) from the tank
- to the OEM feeder damper(already there)
- to the new hacked up feeder damper
- to the AEM adapter (with it's damper and fuel sender).

The key here is that I have three total dampers. The OEM feeder damper on the passenger side is highly ineffective since it's several inches away from the fuel rail (impulse sources). We should have a damper close to each fuel rail to cancel the larger amplitude resonances created by the larger (600cc or more ) injectors.

Note before I did this, I could see psi fluctuations on my DEFI fuel gauge at three RPM points. ~2400 rpm seemed to be the worst.

mx594

iTrader: (4)

Search is your friend:

https://my350z.com/forum/9198429-post262.html

and if you feel like reading, the thread is here:

https://my350z.com/forum/tuning/4848...-what-the.html

mx594

iTrader: (4)

Also I should note that after I did all of this expirementation, CJM started adding HR dampers onto the center of their fuel rails. So per your earlier question about the HR rails fitting a DE I believe the answer is "no", but you could get the CJM rails w/HR dampers instead.

mx594

iTrader: (4)

Sorry I just realized those pictures are tiny. Here are better ones:

http://s922.photobucket.com/user/mx594/story/11619#

iideadeyeii

iTrader: (6)

What are the AFR reading at that rpm? Can't you just adjust the fuel table at that rpm?

str8dum1

iTrader: (11)

it has nothing to do with injector pulsewidth tuning, its do to oscillation of the fuel which can cause the stutters

thatv35guy

iTrader: (1)

Thanks for the input fellas!

I read the big hesitation thread mx, I was just looking for a short term solution for my returnless setup… I’m eventually going to get the CJM rails, but I probably won’t be redoing my fuel system for another few months. My car’s actually at ProEFI right now, just getting a pump gas tune for now…

binder

iTrader: (8)

why waste money on a tune if you are doing the fuel system in a few months? It will change, especially with a better flowing fuel system.

And I recommend the cjm damper rails. Fixed my 1900, 2400, and 2800 rpm lean studder (18:1)

thatv35guy

iTrader: (1)

The motor was just rebuilt (200 miles on it)... The only change was the turbo exhaust housing (upgraded from a .82 housing to a 1.06), so it should be a relatively quick retune.

G3po

iTrader: (8)

please note that what MX did and I did are similar but still a bit different.

I am return-less
and MX uses a rising rate return system.

At your power levels a return-less system should be perfectly adequate.

Adding an RR return system in itself does not replace adequate rail dampening. In some cases it can even make it worse , depending on how one plumbs the external regulator.

djamps

iTrader: (1)

If you removed the OEM dampers then that is most likely the issue. Mine are removed but i have the Aeromotive regulator which apparently adds a little damping, at least enough that I don't have any flat spots. The entire fuel system is noisy as all hell though without dampers. Sounds like a diesel under 2000 rpm.

binder

iTrader: (8)

Ic, still seems like wasted money to me.

mx594

iTrader: (4)

If you have the Aeromotive FPR mounted to the firewall, you will hear the injectors clicking. I made a bracket and mounted mine to the plenum and the noises went away.

mx594

iTrader: (4)

After thinking about your post a little further, I am a little confused/surprised that you are having the 2400 rpm issue...I think I see where you were going with this now.

When my car had the problem, the way I figured it out was by removing the fuel return system (and re-installing the OEM damper) and the leans spots dramatically improved, which led me to the conclusion that it was the missing damper that was causing the problem. What I do not remember (or didn't test scientifically) was whether or not the lean spots went completely away or just got a lot better.

djamps

iTrader: (1)

Indeed, it radiates thru the firewall, however I can hear it radiating from the fuel lines thru the floor too my exhaust is probably just too quiet for my setup.

binder

iTrader: (8)

holy crap....That never crossed my mind and I always thought I had noisy injectors. Thanks for this tip!