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  1. #1
    R88ory RXP's Avatar
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    AF ratios with BEGi

    OK then peeps. I need some advice on what AF ratios I wnt to tune for. Im gona be fitting a BEGi fmu to my ski alongside the rude/turbosmart reg. Now Im fully aware where my AF needs to be at full boost but what is good/safe at idle?? and through the mid range?? I know Mark S did some really good testing and got his AF to be perfect 11.7-9 right across the rev range, but is this best or should it be leaner at idle and under vacume and then start to richen up with the boost. I read a post from Boostaholic (i think) the otherday saying that 14.5 under vacume and getting toward atmosphere was safe and some1 else said that they had best hole shot with an Idle of 14.5. Im setting this ski up for CC racing so I need good throttle response and holeshot more than top speed. Thanks in advance R88


  2. #2
    Moderator beerdart's Avatar
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    I set my Begi up this past Saturday all the info is in my build thread. You will need to make a smaller restrictor for the Begi boost line I used #67 drill .032"

  3. #3
    R88ory RXP's Avatar
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    Quote Originally Posted by beerdart View Post
    I set my Begi up this past Saturday all the info is in my build thread. You will need to make a smaller restrictor for the Begi boost line I used #67 drill .032"
    Thanks Beerdart, I just read the last few pages of your build. What is your WOT fuel pressure at the mo with the lower rpm ect ect??? From testing I have seen that I need alot more fuel than most guys in the states due to cooler temps ect in the UK. I guess its a bit of suck it and see isnt it. I think what Ill do is rig up my compressor to simulat the addition of boost to the reg on the hose and see what my WOT pressure is gona be. I know where it needs to be for good AF its just the other settings I need to figue out. I think I will plum for a little leaner than you at idle as this should make the throttle response better. R88

  4. #4
    Moderator beerdart's Avatar
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    My pressures were 30psi Idle no boost line hooked to the 1:1. 50psi @ 0 boost and around 68psi @ 10# boost. To set it on the hose.

    1. Begi setting backed out.
    2. Start the motor and set Idle AFR after warm up on the 1:1
    3. Remove the boost line from the Begi and set it to 50psi.
    4. Go ride..
    5. The bleed valve on the Begi will adjust WOT. turn in = rich, turn out = Lean. Mine is four turns out.

  5. #5
    canadian iceman
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    with the nightmare i have had tuning here in canada i have been everywhere as far as afr goes....as far as performance goes the 14.5-15 is soooo crisp you will love it!! When i idle around and it is hanging on to high 14's...and i crack the throttle wo...this thing jumps...and i mean jumps to life immediately...by far the best with my setup...my wot afr is now around the 11.7-11.5 mark. With all the injector sizes that i tried the 48 lb units rock!!!...and after consulting Mark Underwood from rotax racing....these 48's are all he uses in canada....same as you cooler temps and cooler water temps....just info for you to absorb...good luck

  6. #6
    iron head's Avatar
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    Beerdart that's the same way I set my up thay work great.I have one on the ski and boat

  7. #7
    R88ory RXP's Avatar
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    Thanks for the info guys. I was going to plum for around 14 at idle when warmed up and then let the BEGi take it all the way upto prob 72psi with my 42s. Im looking at getting some 50s this winter when I up the boost. R88

  8. #8
    R88ory RXP's Avatar
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    OK then. Wel finaly got to do some water testing tonight and I got to start with the BEGi ROCKs!!!!!!!!!!!

    This reg is awsome.

    I now have

    30psi idle at 13.2 afr

    50psi no vacume in the high 13s low 14s at a cruise

    73psi at 8100 and 11.6 afr.

    My throttle response is instant so much so that it burns my prop out of the hole so that is going off for a re-pitch. If you want to add big boost on the stock ecu then IMHO this is the only way. I think you could easy run 50s with this setup maybe even 55s so that would fuel alot of boost at 8100

    My setup consists of:

    Walbro GSS 342 255lph fuel pump

    Custom Fuel rail

    42 injectors

    Turbosmart FPR 800 Fuel regulator (Rude RRFPR)

    Rude Tank insert

    BEGi 2025 FMU

    Resistor in the boost line with 0.8mm hole down the middle.

    Thanks to all those that have helped me along thae way. Rory

  9. #9
    Moderator beerdart's Avatar
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  10. #10
    speedskixp's Avatar
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    . They do work good. Your fuel needs with that set-up are very similar to what I have seen around here. 70lbs wot ussualy gets us around 11.9 A/F.
    Did removing the extra shim fix your fluctuating base pressure?

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