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Thread: Idle Fuel smell

  1. #1
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    Default Idle Fuel smell

    Now I was doing some searching around getting a fuel smell at idle even if it’s actually not rich and I came across a HP Tuners thread that talks about changing injection timing to fix this. Has anyone done this on a LS1 with success? It’s something I’m goig to work on when I get around to camming my Ute. But wondered if anyone else has done anything similar.

  2. #2
    Joe (Moderator) joecar's Avatar
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    Please post a link to the HPT thread...

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    https://www.hptuners.com/forum/showt...le-Please-Help

    https://www.hptuners.com/forum/showt...ing-calculated

    Here are the couple that I was looking through, it seems they have a different table to adjust that is also rpm based for there injection timing. I have just started going through your cax file thread to see if someone had done anything similar.

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    Lifetime Member ProperTuningOG's Avatar
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    Injection timing mod is a must for anything fairly modified. Just be sure you understand whats going on.

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    My understanding is with modifying the injection timing on an aftermarket cam that your aligning the fuel injection time with the opening of the intake valve just before it opens for better fuel atomisation? Do you have a spreadsheet or any maths surrounding a way to figure out the correct injector timing?

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    Cam Math.xlsEOIT Worksheet.xls

    Been doing some more digging and found these calculators to come up with EVC & IVO times. I have based these off a Big Mutha Thumpr camshaft. now my understanding is that I would want to put in the injector timing seconds I time between EVC & IVO to reduce the amount of fuel sucked into the open exhaust but still maintain spray onto the back of the IV, doing this at running temp and allowing a bit longer at warm-up to help fuel atomisation? Am I correct in the way I'm working this EOIT calculator.

  7. #7
    Joe (Moderator) joecar's Avatar
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    Yes, the cam's overlap now means the injector fires while the IV is open, my understanding is that you now adjust the injector timing to avoid this, you now time it at/after IVC

    ( the units and reference twists me in a knot everytime I look at this )

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    Yes it’s not the easiest table to work out what the ms numbers you adjust are actually effecting, the hpt guys have seemed to look into it a fair bit more mainly due to a few extra tables they are offered. I’m currently working on a fairly decent cam so will see what the sniff test brings up at idle by adding a small amount to the injection timing. Using the calculator takes a bit of the maths out of it.

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    Quote Originally Posted by jmsmotorsport View Post
    Yes it’s not the easiest table to work out what the ms numbers you adjust are actually effecting
    It's a mis-labeled table. Those numbers are in references pulses. Each reference pulse is 90 degrees of crankshaft rotation. Higher numbers mean the EOIT is later, lower numbers mean the EOIT is earlier. Most people can't figure it out because there's an offset. Someone did some physical testing over on the HPT forum a while ago (I think it was Bluecat) and the results of the test showed that it is reference pulses and that there is an offset.

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    So for larger cams we want the EOIT later is this correct? By making the number larger does this also change the SOIT?

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