Paxton S550 Acceptable Knock range on datalog?

Discussion in 'Forced Induction - 5.0L V8 Engine' started by Justin5_oh, Oct 8, 2019.

  1. Justin5_oh

    Justin5_oh Member

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    Hey all! I have a 16 GT with a Paxton blower. Im new to tuning and reading data logs and was wondering what would the normal knock range be for this general set-up? Im seeing about +1.5 at a few points on the log but generally im always at 0 or negative which I know is good and allows for timing to advance. My main concern is the positive. any help and insight would be appreciated!
     
  2. Furious18

    Furious18 Well-Known Member

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    I’ve heard that small positive knock like that is normal with centri type blowers because their placement and engine movement. If it’s during shifts or after peak load it’s not very worrisome. I’m sure you’d rather not see any though lol
     
  3. ugstang17

    ugstang17 Well-Known Member

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    Process of elimination should begin with the fuel. Add a can of octane boost to a full tank and see if the log responds differently. Some tuners do not take full advantage of the knock technology to add timing so your log may read 0's thoughout if there is no knock being detected. Many tuners take FULL advantage of the knock sensors and in those cases you will even see negative numbers which is allowing the ECU to add timing if base max advance is has not been yet reached. Negative is good as well as zero in either case. Positive means that knock is being seen and timing will be pulled. Another thing to factor in is that HIGH IAT temps will pull timing as well. This will not be seen in the knock data but rather the spark advance PID. It helps to know what the tuner has set max timing to at WOT throttle so you can see how much is being pulled in these cases and/or at least know at what IAT temp they begin pulling timing.

    IF you are getting knock postive after adding the can of boost, then you need to begin seeing when it is occurring and try to verify the source if there is one before asking the tuner to desensitize the knock strategy. Most reputable tuners will work you through this before simply sending you an update with knock changes.

    This has been my experience on the S550 platform through 3 different tuners in the past year.
     
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    Justin5_oh

    Justin5_oh Member

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    Thanks for the info that really gave me a place to start. When I did the log I was in 3rd gear revving 3k till red line. It shows between 4k and 5.5k is where the positive knock is popping up.. I know like Furious18 said centrifugal superchargers can cause some false knock but would like to be sure that's all it is. I also did the pull at night so IATs seems to be nice and cool all thru out.
     
  5. ugstang17

    ugstang17 Well-Known Member

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    NP. Just can't beat it enough to make sure to work with the tuner to eliminate any real knock concerns before trying to coerce them to desensitize the knock PID. Knock is monitored in the 10-12K hz frequency range as a standard rule BTW. THere is a great book available on tuning by Greg Banish. Its a little dated at this point but the general theory behind it still applies. It helps you better understand load, how fuel injector data is applied and what the more important things mean, timing and air tables,Torque based control for throttle position, MAF theory, combustion theory, timing, knock, O2 sensor history and theory, a little on VCT, etc. IT can be found on amazon for about $17 bucks. Advanced Tuning is the title.
     
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  6. kcc0521

    kcc0521 Well-Known Member

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    It could be false knock but I would assume all knock is real knock. The car will knock on a gear change and if the car spins the tires. Check your intercooler piping and make sure it is not hitting the frame. also check exhaust really good as well.
     
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  7. Whitltng

    Whitltng Active Member

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    Post one of your logs..
    Like other have said fake knock should be treated as real knock. Untill you figure out what it can be.. on my setup 18 with a v3jt I see no knock and I'm on 93 18* timing
     
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    Justin5_oh

    Justin5_oh Member

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    I also am on 93 and see about 18* timing. It won't allow me to directly upload a data log. My tuner isn't taking it seriously and it's a huge tuning company. I agree that knock should be addressed specially when you are running very similar stuff and aren't seeing any.
     
  9. OP
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    Justin5_oh

    Justin5_oh Member

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    I sent you a PM.
     
  10. Rothgray

    Rothgray Well-Known Member

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    I'm on about 14-15psi on a Vortech, and 21.5* of timing, I'm seeing 0 knock during a full 1/4 mile run.
     
  11. OP
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    Justin5_oh

    Justin5_oh Member

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    What kind of fuel do you run on that setup?
     
  12. Whitltng

    Whitltng Active Member

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    E85 or boostane added for 21*
     
  13. OP
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    Justin5_oh

    Justin5_oh Member

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    I really think my fuel is total crap here in northern Florida. I will try some octane booster and go from there. What are some recommended octane boosters? I assume boostane is one?
     
  14. Rothgray

    Rothgray Well-Known Member

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    E85 out of the pump.
     
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  15. ugstang17

    ugstang17 Well-Known Member

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    I used the VP booster brand. It was on the shelf at the speed shop where I do all my business.
     
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