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  1. #1

    F15x Stage 2 Macsboost Tuning Help Needed

    I have an F15x that I added the macsboost ECU and intercooler to. I put 102 octane in it and the thing has a stumble/hesitation at about 3k when you give it full throttle from a stop & a bit higher up in the RPM if you are going a bit. It now reads 'limit mode,' which means the knock sensor is registering knock at just about every time I got more than about 2800 rpms even if I very slowly apply throttle. I've replaced the plugs and that did nothing and I have a hard time believing the thing should be knocking with 102 octane in it. The first tank I blended 102 and 91 together to get 94.7 octane on the 1st tank and towards the end the knock problem emerged, but the stumble/hesitation has been there the entire time. The 2nd tank I added just 102 octane to it and the knock problem still persists.

    Is there anyone near Kansas City or the Lake of the Ozarks that could maybe help me get the tune right on this thing? I've tried contacting Mac several times and either get no response or a fairly short one that doesn't really help. Here are 2 data logs

    http://www.indykansastax.com/logs/test%20456.csv

    http://www.indykansastax.com/logs/test123.csv


  2. #2
    supermac's Avatar
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    I never received your data logs.
    I said this in email every time you said you tried to send them to me.

    I will take a look.

    Some knock indication is normal, as this is normal engine noise... steady state knock is what you should be concerned with, and only at rpm over 4500

    The indicator is very sensitive.. better this than not.

  3. #3
    supermac's Avatar
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    Click image for larger version. 

Name:	graph.png 
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ID:	333280I took a look. Things get quieter once the engine warms up.. this is normal and looks ok. things are louder when cold. The knock sensor is nothing more than a microphone.

    You need a run where the rpm change is gradual over a long run when fully warmed up to get a better look.

    This shows no knock at wot.

  4. #4
    Bob 1tommygunner1927's Avatar
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    220kPa at 7500....Nice!

  5. #5
    I took it out yesterday and the problem didn't exist at over 4500 like Mac stated. I'm guessing the end of the 1st tank was a bit too heavy on 91 from perhaps not great mixing, which is why the problem existed at full throttle even warmed up then, but now everything seems better since I ran through 5 gallons of 102 and refilled the entire tank with 93.

    The stumble/hesitation is still there though. I few times when I went out cruising yesterday at part throttle (say 30 mph or so) let completely off the gas turned the steering wheel fully and gunned it trying to spin the thing and it died from this stumble/hesitation. Because of this, I took it out again today and did a couple of runs with very slow rpm up and rpm down as well as several instances of me gunning it from low or no throttle. Even when I hit it to maybe 50-60% throttle from there the issue came up in addition to full throttle. Below is a link to the log

    http://www.indykansastax.com/logs/6-23-14%20log.csv

  6. #6
    Problem solved. Macs latest tune fixed everything. It hadn't been loaded on the ECM correctly and now that it has the thing runs perfect.

  7. #7
    supermac's Avatar
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    excellent

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