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Cure to 2500 rpm lean spike

Discussion in 'Engine/Tuning' started by TP03, Sep 23, 2020.

  1. TP03

    TP03 Active Member Established Member

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    I've gained so much knowledge from this forum and never really had much to give, that hasn't already been mentioned. I came across something this summer that really helped the problems I was having so I thought I'd share and maybe save someone else a headache.

    This spring I dumped quite a bit of money into my car. Mainly blower swap and full Fore return fuel system. I ended up going with a dead head setup since so many have good luck with it here and I really like how clean it looks just having two lines running into the back of each rail.

    After getting everything installed I started the process of remote tuning. Revision after revision it became apparent that at 2500 rpm I was getting a lean spike that wasn't going away. I could see it on my wideband but more so I could feel and hear it popping at that spot consistently. My tuner was very good at trying a bunch of different things, messing with transient fuel and trying to tune it out but no matter what was added it was still there.

    Finally at my wits end I took to google and figured someone else has to have some info on a similar problem. After spending a decent amount of time searching I came across some old info on a Nissan forum that talked about having a factory fuel pulse damper that smooths out harmonics in the fuel system and how one guy had low rpm lean spikes after removing it.

    This gave me a direction and something to at least try. After a quick search I came across the company "Radium" that sells aftermarket fuel pulse dampers for high pressure/flow fuel systems.
    Fuel Pulse Damper, Direct Mount Kits

    I figured what the hell it's worth a shot for $100. So I ordered a damper that I could adapt to thread into my fuel rail. After I received/installed it, On the first test drive I was completely blown away. I spent a good part of my summer with numerous tune revisions and with a 15 min install and $100 that lean spot was gone. Car ran amazing and absolutely zero lean spike. I did have to get another tune revision to take some of the fuel out of that spot that was added when trying to mask it.

    In no way am I working for or even know anyone from Radium but their product flat out worked for me and cured a lot of headaches and I thought I'd share.
     
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  2. 03cobra#2

    03cobra#2 Hobbyist Of Many Hobbies Established Member

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    Good deal! Thanks for sharing. Curious. This lean spike was only at 2500 rpm? Was it during transient fueling or was your foot steady on the gas pedal?
     
  3. TP03

    TP03 Active Member Established Member

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    996B2335-998B-4CF2-A40B-935D91E05B9D.png
    817D3122-22FC-4713-8BCC-E2970334E90D.png
     
  4. TP03

    TP03 Active Member Established Member

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    It was when my foot was steady. I could accelerate past that spot and everything was good but if I casually go thru the gears it would pop and stumble at 2300-2500 every time.
     
  5. 01yellercobra

    01yellercobra AKA slo984now Established Member

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    What pumps are you running? It would be interesting to see what the fuel pressure is doing at that point with and without that damper.
     
  6. TP03

    TP03 Active Member Established Member

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    Twin 465's. That's a good question. As far as I know the logs looked good without the damper. I also don't really want to put my tuner on the spot either but I don't think he could see a fuel pressure issue?
     
  7. 03cobra#2

    03cobra#2 Hobbyist Of Many Hobbies Established Member

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    I'm not exactly sure how you are getting a lean spike with steady pedal pressure. I guess if I looked at the logs and you are logging the frps it might make sense to me. I'm glad it worked for you.
     
  8. TP03

    TP03 Active Member Established Member

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    That's why I figured I'd post it up. My tuner has tuned hundreds of cobras and he couldn't explain why it was doing this. Although my situation might be rare, maybe it will help someone else down the road.
     
  9. RainyP71

    RainyP71 Member Established Member

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    I am far from an expert, but I have a hunch the issue would have been fixed with the same outcome switching to a return style system. Because wouldnt the pressure regulator be acting as a damper in almost an identical way to the damper you posted? Really interesting either way, thanks for posting!

    Sent from my SM-G975U using Tapatalk
     
  10. TP03

    TP03 Active Member Established Member

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    *
     
    Last edited: Sep 23, 2020
  11. TP03

    TP03 Active Member Established Member

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    This is all after I installed a Fore return system. I have some theories that it has something to do with harmonics from the injectors coupled with dead head fuel configuration at just the right spot (2500 rpm), but at that point I might as well throw on a tin foil hat and call it a day. Don't know why or how but it works.
     
  12. RainyP71

    RainyP71 Member Established Member

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    Okay so you had the issue on a dead head style system, then switched to a return style? So you went from returnless to return style? Sorry, I read your post and saw you said you went with a "dead head style" system.

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  13. TP03

    TP03 Active Member Established Member

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    Oh boy... I had a stock returnless. Changed to return style in a dead head configuration.
     
  14. RainyP71

    RainyP71 Member Established Member

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    Sorry for the ignorance, I am used to "dead head" being synonymous with returnless.

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  15. TP03

    TP03 Active Member Established Member

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    I gotcha. Another buddy of mine never heard of a return style dead headed. He argued with me about it one night. I thought you were going to do the same. Lol
     
  16. RainyP71

    RainyP71 Member Established Member

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    Definitely no interest in arguing, I watch enough people do that online already lol! But since I haven't heard of this style, where is the regulator placed? What's the route of the fuel from tank -> engine -> back? Even better if you have a diagram Id love to see it.

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  17. TP03

    TP03 Active Member Established Member

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    There's a bunch of threads and info on it here if you search it. Quick explanation... Regulator mounted in the passenger fender. Feed and return lines going from tank to regulator. Two (regulated pressure) lines coming off of regulator feeding the back of both rails.
     
  18. RainyP71

    RainyP71 Member Established Member

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    Hmm. I get it, halfway between full return and full returnless. With that, wouldnt you be 90% to a full return style already, what was your reasoning not going full return?

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  19. TP03

    TP03 Active Member Established Member

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    Cooler fuel temperatures is the biggest reason and cleaner engine bay is another benefit. All your fuel stays out of the engine bay until it's needed.
     
  20. olympic

    olympic Well-Known Member Premium Member Established Member

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    Thanks for the info! I always thought removing the factory damper was a bad idea. My car is still returnless but the factory damper was removed to install -8AN feed line and billet fuel rails. It drives fine for the most part but occasionally exhibits strange behavior when pushed hard that could be fuel pressure related. I may end up ordering one of these Radium pulse dampers as my fuel rails already have -8 ORB fittings in them so the damper would fit right in.
     
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