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Thread: My A/F ratios

  1. #1
    SC on water, TT on land
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    My A/F ratios

    I thought I would post up my results so others can see. Last weekend I went out and did a little tuning. My mods are Rude 1 Charger, XS Intercooler, 42lb injectors, solas 15/20r prop (my pitching attempts failed due to the vice, so its not pitched), rrfpr @ 60 psi, and riva 3" intake. I'm planning on keep ing the 3" right now to restrict the rude a little while tweaking everything. It was around 87 degrees and the water temps were 77 degrees


    At cruising i was seeing around 14.7, perfect! I have attached a map of one pull I recorded on my LM-1 until I could get a logger cable. I only did a pull up to around 60 mph and plan on working my way up. I didn't notice rpm levels to begin with, but that will be next. On my pull, I started off with 3/4 throttle to get the nose down and then I punched it. I've attached my A/F map.

    As you can see from the map, i'm running just a little rich as it hovered around 11.3ish. Now that I have my cable and a friend with a boat that stays permanently docked. I plan on making a couple of WOT pulls next weekend and check on rpms, then make necessary adjustments. I will post up my results.
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  2. #2
    Moderator Snoman's Avatar
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    14.7??? Im seeing almost 17s..I dont know but it looks to me like your running way lean at times..
    I see you are down around the 11s which is a tad rich but at waht RPMs are you getting them numbers??

  3. #3
    Formerly Ultra250 TN Aquaholic6801's Avatar
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    14.7 is perfect for a car, 11.8-12.3 is about where you want to be.......


    Quote Originally Posted by Snoman View Post
    14.7??? Im seeing almost 17s..I dont know but it looks to me like your running way lean at times..
    I see you are down around the 11s which is a tad rich but at waht RPMs are you getting them numbers??

  4. #4
    R88ory RXP's Avatar
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    Quote Originally Posted by Ultra250 Tn View Post
    14.7 is perfect for a car, 11.8-12.3 is about where you want to be.......
    I agree that you want to be at 11.8-12.3 but this is at WOT 14.7 is maybe a little lean at cruise but ok. Its when you come on boost that you need the AF a bit lower. R88

  5. #5
    Quote Originally Posted by R88ory RXP View Post
    I agree that you want to be at 11.8-12.3 but this is at WOT 14.7 is maybe a little lean at cruise but ok. Its when you come on boost that you need the AF a bit lower. R88
    I second this, in boost you always need to be a little rich just to be safe but on a N/A application 14.7 is fine.

  6. #6
    SC on water, TT on land
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    Quote Originally Posted by Snoman View Post
    14.7??? Im seeing almost 17s..I dont know but it looks to me like your running way lean at times..
    I see you are down around the 11s which is a tad rich but at waht RPMs are you getting them numbers??
    you may be running a bit lean when cruising. The part of my graph where i'm around 16 is idling before the pull, and when I let off is when the A/F ratio leans back up again. Haven't checked the rpms yet as it wasn't a complete pull to top speed, this was just a starting point to make sure everything looked good before continuing as I couldn't find my serial cable to download to the laptop. I've got an rpm converter but unsure of how to hook it up on the ski.

    I plan on bringing my laptop to the river this weekend and put it on a friend's boat, do a pull then go back and check it and adjust the rrfpr.

  7. #7
    Dave Sharp dav_dman's Avatar
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    stoich is 14.7..at idle thats where you want to be..anything higher than idle needs to richen up, imo. 11.8-12 at wot is about right, i think Jerry said. I run low to mid 11's on my boosted car because we've found the engines prefer rich. I think the rxp handles lean very very well and gives us a false sense of "it's okay" .

  8. #8
    SC on water, TT on land
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    Update:

    Went out tuning again after installing a new fuel pump. On a cold start, my wideband shows that I tend to run a little too rich. After things warm up it shows that I'm running a bit lean. During idling, I'm getting around 16 or so on the AFR. When cruising, it is now showing between 15.5-16 on the AFRs, and thats even when I gas it a little bit. Sometimes there is a slight hesitation in there when I gas it. However, I did one short pull on WOT (I'm using an LM-1 so I'm having to record it then load it on the computer at home later on) and the AFRs seem to hang around 11:1 (a little rich but at least it is not damaging the engine). My rude RRFPR is set at 60 PSI.

    What this is telling me is that I'm not getting enough fuel deliver down low and too much fuel delivery up top.

    Anyone else have any ideas? Maybe I need to purchase a different fuel controller? Thanks for any help provided as I would like to have this tuned a lot better!

  9. #9
    SC on water, TT on land
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    I am going to try to unhook the vacuum source and check my AFR's, but I have a feeling I will need to bump my base pressure up a little bit since my mid-range seems to be slightly lean. I am sitting at 60 PSI right now, what would be a good starting point? Maybe 65 PSI?

  10. #10

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    What 42 lb. injectors do you have? I ran almost your exact same setup (I had a 160 thermostat installed as well) at 59 lbs. key on w/ no boost line attached as my Rude / Turbosmart RFPR did not rise, but I did not check the AFRs. I sold the machine and my customer has put 70+ trouble free hours on it and still going.

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