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  1. #1
    dnielsen's Avatar
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    Wacky AFRs, Need Advice

    RXPX, Riva ECU, Riva 50s, Riva RRFPR (Static Setup, No Rising Rate) set at 62 psi. Walbro, X-Pro Charger, Stock Intercooler (Relocated), Riva Rear Air, Riva Rear Exaust and Waterbox, other basic mods...., 100 degree air temps, 90 degree water.

    AFR at 11.9 - 12.0 at WOT, 5500-7500 ARF 13.5-14 way lean, idle is 14.2 or so. this is off the trailer and in the water.

    On the trailer hooked to the hose the AFRs are really lean 14.0 - 15.0 range, thought i'd add a little fuel so bumped pressure up to around 64-65 psi then the AFRs went even further lean 15.5 and up. Quickly lowered psi down to around 57 psi and the AFR began to drop to around 12.0, lowered again to around 55 psi then the AFR was right in line with 11.9 or so.

    1) Is this normal for the AFRs to act like this on the trailer and am I wasting my time fooling with it while on the trailer?

    2) When in the water as described in the upper section why am I lean at idle and in the mid range then right on Q at WOT? I thought most people ran rich and leaned out at the top during WOT runs.

    Just starting to tinker with the AFRs so this is still kinda new to me, don't want to F up something (engine).., any help would be appreciated!!


  2. #2
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    ahh the same battle i'm facing.
    your WOT afr's are actually pretty good!

    the riva 50's really only "like" to be ran between 58-60 psi @ idle. if you turn them up (psi) the idle afr's will actually become leaner. the higher psi and the slower reaction of the injectors actually lock's them up and less fuel pass's. just the nature of the delphi(riva) injectors


    my afr at idle is similar to yours in the high 14's and will blip 15's. to be honest i think its to lean myself and doesn't quite idle right i think thats just the way riva has it mapped in the ecu.

    for some reason on mine though (same set-up as yours: rxpx, walbro, riva ecu/injectors, rrfpr @ 58-60 et137) my WOT afr's are retarded. in the LOW 11's-high 10's and i know this is correct as i can not only watch my gague but feel the laziness and lack of throttle response and watch my rpms drop off

  3. #3
    dnielsen's Avatar
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    Went back out today, managed to get the regulator set to 62 psi before the injectors would lock up causing the the engine to stumble at idle. at 63 psi the lock so I backed down to 62 and managed to run AFRs at 11.8-11.9 at WOT. Still lean at bottom and midrange, the Riva ECU is pulling fuel i'm certain. Need to get my Rude controller working, tried running it on Windows 7 but couldn't manage to get the operating system (Windows-7) to recognize the driver. I'm certain once I get this working I can install and adjust the maps to fool the ECU into adding fuel where needed. I can then set the reg back to 60 psi and all will be good. I'm pretty sure the 50s will flow enough fuel even once I get the RPMs up and around 8550.

  4. #4
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    what do you consider lean to be in the midrange. i did a lot more testing today and wanted to compare my results to someone elses

  5. #5
    speedskixp's Avatar
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    As Mike mentioned, your wacky afr's going lean when you turn up the pressure is because of the riva 50's. Because of this if you want to richen it up at idle and mid you can run the boost line and set the idle pressure around the low 50's and rise to 62ish. Sounds silly huh? Turn the pressure down to go richer at idle. You'll find this is not the case at wot though where the injector cycle is much longer.

  6. #6
    Eric Ocman's Avatar
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    As I told Mike H. My setup seems very good at this point and VERY simple. 57Lbs with key in boost line attached with Bosch 48's. 11.4 12.5 11.8

    You can pick them up here or on ebay....

    Dont over complicate your situation with the RFC. IMO you DONT need it with a Riva ECU.

    Also like speedski mentions more than likely you can attach your boost reference line. Drop the base pressure a tad which will richen up your bottom end and keep your top the same or better bro.

  7. #7
    dnielsen's Avatar
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    Thanks guys, I'll give this a whirle and see what happens. Bad news is it may be a couple weeks before I can test results (darn). I did notice when I dropped fuel pressure that the AFRs started getting down to where they should be. I'll switch it over to rising rate setup and see what happens. Feel sorry for anyone that installs all this Riva equipment as recomended and doesnt check the AFR.

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