Thread: AF ratios with BEGi
07-15-2009, 07:29 AM #1
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
07-15-2009, 08:05 AM #2
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"
07-15-2009, 09:14 AM #3
07-15-2009, 09:48 AM #4
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.
07-15-2009, 12:30 PM #5
- Join Date
- Dec 2007
- medicine hat, alberta, canada
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
07-16-2009, 07:15 AM #6
Beerdart that's the same way I set my up thay work great.I have one on the ski and boat
07-16-2009, 09:03 AM #7
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
08-03-2009, 04:09 PM #8
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
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
08-03-2009, 04:13 PM #9
08-03-2009, 05:01 PM #10
. 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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