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  1. #1

    Need tuning advice from expert tuners please

    Tested today with the addition of a Rude charger and rrfpr. I am running lean. First off, the rrfpr is not working correclty. I'm only seeing around 2.5 psi of fuel pressure increase @ 12 # of boost, its not 1/1--I'll need to sort that out. So, I increased the fuel pressure setting on the rrfpr until I got up to 69.8# not running. The running fuel pressure is 2 psi less than the static, not running pressure. I did this to see where I was at at wot.

    Currently at wot I am at 8400 rpm's, 12# of boost, 70.5 psi fuel pressure actual and around 13.4 Afr. I only held it wot for 5-6 seconds, 1/2 tank of fuel, trim in neutral and got 81 for a top speed. The speed looks ok for the rpm with the current prop. I think the lean up top condition is costing me horsepower to pull the prop on top.

    I've attached four logs from the Af meter. It appears I'm rich down low and lean up top. With a properly working rrfpr it looks like I need to go to larger injectors and maybe drop the initial fuel pressure setting. Any suggestions would be much appreciated.

    Thanks,
    Mark

    Conditions today:
    Dry bulb 74
    Wet bulb 59
    RH% 42
    Water 60
    Bar Press 29.9


    My current setup:
    Rotax Racing Ecu
    Ported and decked head by Racetech
    Rotax racing cam and sprocket
    Honed exhaust manifold
    Rotax intercooler
    Rude supercharger
    42# injectors
    Riva rear air intake
    Riva thru hull
    Modded waterbox
    Riva intake grate
    Skat modded pump with 82mm ring and Riva/Skat 15/20.5 3-blade
    Riva pump wedge w/ ext. rod
    Rotax front engine mount
    Denso plugs
    Catch can
    Attached Files Attached Files


  2. #2

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    Either you don't have a rising rate fuel regulator or your line that is hooked up to the intake for boost is not working properly.

  3. #3
    What about the high afr at wot? What size injectors do I need?

  4. #4

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    You will need 50lb @ around 60lb fuel pressure @wide open throttle.
    The idle fuel will need to be around 42lb and idle will be rough.
    Mark @ rotax racing Race tech could sell you 48"s. I think the stock fuel pump will only push 70lb of pressure.

  5. #5
    Site Admin Green Hulk's Avatar
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    Quote Originally Posted by Mark S View Post
    What about the high afr at wot? What size injectors do I need?
    Stock sized injectors will work fine!

    Mark, first an explanation on how the RRFPR works.

    Set the base pressure at 60 psi engine not running.
    When you start the engine the the fuel pressure will drop. It will drop even further as you cruise but when the engine comes under boost the fuel pressure will raise.

    If you are thinking that you set the base pressure at 60 psi and then you hit 14 lbs of boost that you should have 74 psi of fuel pressure it doesn't work that way. Actual fuel pressure will be in the low 60's at best.

    I don't think your RRFPR is getting a good signal the way you have it tee'd off like that. You really need to drill/tap your stock IC blockoff and install the fitting so the RRFPR has it's own dedicated line.

  6. #6
    Quote Originally Posted by Green Hulk View Post
    Stock sized injectors will work fine!

    Mark, first an explanation on how the RRFPR works.

    Set the base pressure at 60 psi engine not running.
    When you start the engine the the fuel pressure will drop. It will drop even further as you cruise but when the engine comes under boost the fuel pressure will raise.

    If you are thinking that you set the base pressure at 60 psi and then you hit 14 lbs of boost that you should have 74 psi of fuel pressure it doesn't work that way. Actual fuel pressure will be in the low 60's at best.

    I don't think your RRFPR is getting a good signal the way you have it tee'd off like that. You really need to drill/tap your stock IC blockoff and install the fitting so the RRFPR has it's own dedicated line.
    Jerry:
    Did you look at the attached LM1 logs?
    The first two were with the rrfpr set @ 60.9 psi. The last log was with the rrfpr set @ 69.8. Look at the bottom of the charts, the base, running and wot fuel pressures are noted. I am running 42's now at 70.5 psi of actual fuel rail pressure and have af ratio of 13.4. I am running a dynotune digital fuel pressure gauge, so I see fuel pressure. There is not much of a differance between idle and midrange pressures, less than 1 psi.

  7. #7
    Site Admin Green Hulk's Avatar
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    Mark, you aren't seeing much of a difference between running and WOT fuel pressure because of where you are tapped into the manifold. Not near enough volume of air to actuate the diaphram in the RRFPR.

    At 69 psi of fuel pressure you should be so rich it's not even funny but you still read lean
    Is this a new 02 sensor? If so did you calibrate it? I see on some of the charts you have these lean spikes. Any idea what that's about?

    Also, where do you have your fuel pressure sensor at? Is it in the RRFPR?

  8. #8
    It's a new O2 sensor that came with the LM1, which is also new. Yes I did calibrate it. Even pulled it when I got home today to read free air O2 just to make sure it was calibrated properly. Right at 20.9%--perfect. Attached are the pics of how I set up to read fuel pressure. On the LM1 logs I eased up to wot. There was floating debris in the river today. May have chopped the throttle for a second or so to avoid debris--that may have caused a spike. Tell you what, going 80 while trying to avoid sticks, branches and debris while at the same time trying to read afr, boost, fuel pressure and rpms is a bit dicey at best.
    Attached Files Attached Files

  9. #9
    Site Admin Green Hulk's Avatar
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    Sounds like you're spot on with your AFR gauge.

    I don't know why it would make a difference with the location of your digital fuel pressure sensor, but I'm curious. Does the manual gauge on the RRFPR and the digital gauge read the same when the lanyard is plugged in?

  10. #10
    Yes, both gauges read the same with the lanyard plugged in. All the way through increasing pressures today both were exactly the same.

    Is it possible with the ported head and cam the motor is able to process the air from the Rude better resulting in the high af ratio. How many people are running the Rude with a ported and decked head and racing cam and have checked af ratio?

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