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  1. #11
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by tiderider View Post
    Trying to get my AFRs up a tab, like .5 so it would be in the mid/high 12s at idle and 12.2ish at wot with 8500 rpms and 13psi.

    Presently with the use of 94 Octane with no ethanol is giving me about .5 AFRs below a more efficient level..

    I don't trust the 92 with ethanol pump fuel in Washington but wouldn't mind the added 10% ethanol if it helps increase my AFRs .5 across the whole band width.

    I was thinking of using the 92 with Ethanol and adding a base +4 Octane dosage with Torco booster...

    Would this help increase my AFRs, lean the readings without the risk of poor quality 92 detonation?

    Reduce ignition timing......

  2. #12

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    Quote Originally Posted by 1tommygunner1927 View Post
    Reduce ignition timing......
    Hi, thank you for the info. I am unable to see, read or change ignition timing with my 2007 Siemens ECU and Riva tune with PLX logger set up. The engine has been rebuild with .5mm oversized pistons. CP pistons with Molnar connecting rods also having a much less overall weight from stock. Each piston/rod are exactly the same weight, except for piston/rod #2 that is .5 gram lighter. Riva wants to see a log with their present tune called 60 9200 with the new engine. It really only needs .5 AFR leaner.

    I always thought that going from pure gas to 10% ethanol blend leaned out the AFRs. Isn't ethanol similar to having less power from pure gas (would simulate more air present then gas)? I read somewhere that the ethanol blend would lean it a tab like .5 Afrs..

    That's why I was considering using Washington 92 with ethanol but add perhaps even less then the minimal Torco boost of 8 oz per 5 gallons for a +4 octane boost. Perhaps use 6 oz of Torco on 5 gallons instead for +3 on the shitty 92 Washington fuel..

  3. #13

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    Quote Originally Posted by Shark View Post
    Personally, I would add a fuel pressure regulator to your setup and adjust with that. Or, I would add a few gallons of e-85 till you get your desired result. But mixing fuel is kind of a pain so Id go with the first option.
    I have a RRFPR, I am just concerned that lowering the pressure to perhaps 55 psi instead of 58 psi to achieve the leaner .5afr may also reduce fuel supply to the 60lb injectors at 8500 rpms to a level that it may damage the engine..

  4. #14
    Bob 1tommygunner1927's Avatar
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    Quote Originally Posted by tiderider View Post
    Hi, thank you for the info. I am unable to see, read or change ignition timing with my 2007 Siemens ECU and Riva tune with PLX logger set up. The engine has been rebuild with .5mm oversized pistons. CP pistons with Molnar connecting rods also having a much less overall weight from stock. Each piston/rod are exactly the same weight, except for piston/rod #2 that is .5 gram lighter. Riva wants to see a log with their present tune called 60 9200 with the new engine. It really only needs .5 AFR leaner.

    I always thought that going from pure gas to 10% ethanol blend leaned out the AFRs. Isn't ethanol similar to having less power from pure gas (would simulate more air present then gas)? I read somewhere that the ethanol blend would lean it a tab like .5 Afrs..

    That's why I was considering using Washington 92 with ethanol but add perhaps even less then the minimal Torco boost of 8 oz per 5 gallons for a +4 octane boost. Perhaps use 6 oz of Torco on 5 gallons instead for +3 on the shitty 92 Washington fuel..

    I run 4 O2 sensors on my ski: 3 in a 1" exhaust spacer at each port and one after the turbo. I tune according to the after turbo sensor due to a more accurate A/F reading. Because your O2 sensor is positioned in the exhaust manifold it will have similar readings as my 3 in the exhaust spacer. As such, the A/F ratio shown is incorrect.....showing a richer A/F than actual due to exhaust pressure.

    My data log, at 8K rpm, 184kPa (about 12 pounds of boost) the O2 sensors at each port indicated an A/F of 10.7:1 while the after turbo sensor displayed 11.75:1 (too rich). That said, I recommend you NOT lean out your A/F. Your indicated 12.2 A/F at 8500 rpm is closer to 12.7 to 12.9. If anything, add fuel!

    Also note straight gas has a stoichmetric value of 14.7, whereas 10% ethanol fuel is 14.1, and runs leaner if stoich isn't changed. 15% ethanol is leaner yet at 13.8.
    Last edited by 1tommygunner1927; 11-06-2019 at 08:13 PM.

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  6. #15
    !!!! wave jumper !!!! 05_RXP's Avatar
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    I would keep using the 94 octane fuel.
    you already have a rrfpr I would drop a psi at a time till you get the wot afr you want. Specially if its .5 to rich across the board. Wot is really the only place that afrs are critical to not be lean.


  7. #16
    boost junkie skidoochris's Avatar
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    "Wot is really the only place that afrs are critical to not be lean"
    wow, a general statement thats not even close
    load plays a big factor when in the peak torque rpms
    peak torque is the hot spot for detonation not at max rpms
    these sc motors have very linear boost so peak boost is not at peak torque rpms
    where a turbo may have max boost at those peak torque rpms
    no motor was ever hurt from being a little rich
    but lots of damage can be caused from a lean tune
    whats too lean depends on many things , timing and fuel are just the beginning

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  9. #17
    !!!! wave jumper !!!! 05_RXP's Avatar
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    Quote Originally Posted by skidoochris View Post
    "Wot is really the only place that afrs are critical to not be lean"
    wow, a general statement thats not even close
    load plays a big factor when in the peak torque rpms
    peak torque is the hot spot for detonation not at max rpms
    these sc motors have very linear boost so peak boost is not at peak torque rpms
    where a turbo may have max boost at those peak torque rpms
    no motor was ever hurt from being a little rich
    but lots of damage can be caused from a lean tune
    whats too lean depends on many things , timing and fuel are just the beginning
    Obviously a dialed in ski thru the whole range is best but your not going to burn Down a motor at idle and cruise being a little lean. You will how ever at wot.

    peak torque is the hot spot for detonation not at max rpms”
    Do you control your detonation with your afrs?

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  11. #18
    boost junkie skidoochris's Avatar
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    afr is only part of the equation
    the bosch ecu is good at detecting knock
    if you log the timing and see the timing cut where its not the same as the table
    it may be because of knock or may be from another comp table
    you also may be able to log the knock level
    you can control knock easier with octane than afr
    with the correct fuel, timing you can run in the 13s at 20+ psi safely
    the 1500 is most likely to knock at peak torque rpm 6-7000 under load
    pulling a tube or in a big boat and higher than stock boost

  12. #19

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    Wow! This has really become a truly helpful thread.
    The big players come out with great knowledge off season!
    Sounds like I am pretty much dead on with my AFRs and should simply stick to 94 Octane, pure gas.
    I do have a starting issue when the engine is shut down hot or after running. It can take 2 or 3 starting attempts to start up but will start up if I flood mode crank it after initial attempt to start..

    Thank you, everyone.

  13. #20
    Bob 1tommygunner1927's Avatar
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    Just between you & me, I'm a novice tuner. I know enough to be dangerous and blow stuff up but haven't yet! Now that I have a functioning rrfpr I can make useful and consistent changes to my current tune. Kool weather is here....not sure if I'll have another day at the lake this year.


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