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  1. #1

    Afr vs. Egt readings

    Normally tune my ski in the spring. Checked afr's a couple weeks ago and was running rich at wot...11.5, so backed off fuel pressure to run 11.8. Put the Egt probe back in the next time out and saw 865 degrees C (1589 F), which surprised me. Never have seen over 825C (1517 F). My findings were:

    64# fuel pressure @ wot was 1589 F Egt's, 11.8 Afr, 8450 Rpms.
    68# fuel pressure @ wot was 1551 F Egt's, 11.6 Afr, 8400 Rpms.
    70# fuel pressure @ wot was 1517 F Egt's, 11.5 Afr, 8300 Rpms.

    I was surprised to see such a change in rpms with such a small change in afrs. I check Egt's in the J-pipe (same place the O2 sensor goes) So, where is the balance point? Do you tune for afr and max rpm or for Egts? What is the max Egt for safety checking at the J-pipe, assuming the Egts would be a bit higher at the exhaust manifold?


  2. #2
    Moderator beerdart's Avatar
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    Aug 2006
    Interesting findings. Does Chitown use summer gas with the lower RVP? CT does and I noticed after June 1st I had to adjust AFR,s. Not a big change but a change. I know that Summer gas is the same octaine with additives to lower the RVP.

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