How To: Add Pressure Input for PC-V

Discussion in 'Rocket Performance' started by Claviger, Jun 6, 2018.

  1. Claviger

    ClavigerHP Junkie extraordinaire

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    So after a few years playing with PC-V and TuneECU, I've come to recognize a problem, exacerbated by the big cams in my bike. The fuel table using throttle position vs RPM isn't granular enough to really perfectly tune the low throttle position parts. Most of the time when riding legal speeds, the Rocket will be at 0-5% throttle position, with a lot of time at 1% and 3%. The problem with that, is the PC-V table only has 0,2,5 percent columns. How do you add granularity? Use a pressure based table because you can make it as granular as you want. Here is how:

    On my 2014 Roadster, the wires coming from the MAP sensor are:
    Pink - Reference voltage to sensor
    Pink Black Tracer - Ground
    Pink Green Tracer - Signal wire

    Tap the signal wire and run it to the "Analog input" on the PC-V.
    Enable the Pressure Sensor and add your voltage to MAP relationship. For my sensor the values were:
    4.05 Volts = 997 HPA
    2.44 Volts = 590 HPA

    PC-V will interpolate and make a voltage > value relationship (it's hidden you can't see it) based on the values you input allowing it to read outside of those two points.

    To get your sensor's values, connect TuneECU and go to "Diagnostics". On the left, look at "Barometrics" with the ignition on, but the engine off, you'll see a value and two voltages something like the below
    997 4.04 4.05

    The 997 is the hpa, the first voltage 4.04 is the sensor located under the seat, the second voltage is the one you want to use, its the MAP sensor voltage.

    Write down the hpa and MAP sensor voltage with the engine off.
    Start the bike and look again, the MAP sensor voltage will swing around a bit, but the most frequently seen voltage at idle is the one you use, mine occasionally swung from 2.44 to 2.6 or 2.8, but 2.44 was the correct voltage.

    Inside PC-V software go to "Map Tools" > "Pressure Tables" > Add Fuel Table.

    It will bring up a window asking for "Table Size" set this to 20. Here are the PSI conversions for the stock TuneECU columns in the L-Tables, I suggest doing this to make it easy to mentally transpose and adjust the base TuneECU tune if you want to do that.
    Pressure Table.jpg
    Pressures.png

    Now that you've the table made, you can go to "Map Tools" then "Advance/Demote Map" then down to the autotune area and set it to "Pressure" instead of "TPS". This will allow it to tune via pressure instead of TPS and use a far far more granular table to adjust your tune.

    For a forced induction bike, just extend the pressure table from 20 to 30 and keep adding pressure until the 2nd to last vertical column is your expected max boost, then make one more column with your expected max +5 psi, just in case of overboost situation.
     
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  2. Claviger

    ClavigerHP Junkie extraordinaire

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    Part of the challenge of tuning using only TPS based is something as simple as idle. The amount of vacuum pulled at cold idle vs hot idle is not the same, so, when setting idle in the L table, you'll have to adjust multiple areas in the 700 and 900 area across different vacuum columns. For me the range is 590 hpa at full hot idle in the afternoon and all the way to 650 at cold start idle early in the morning.

    While I don't advocate setting your idle fueling using PC-V, even if you don't use the pressure table, hooking it up and using it during datalogs will allow you to see what very minute changes to the throttle position do in the L portion of your TuneECU tune if you use L tables at all.

    For example, when my PC-V reads 2% there's a small amount of "range" within 2%. At just barely 2% I run rich, at just under 3% but still registering at 2%, I run right at 13:1 AFR. How do you tune that with only a 2% column like in the stock TPS/RPM table? You can't. Thus the need for pressure tables at low throttle position. Now consider that 0% has a range within it as well and you'll start to see the problem.

    I hope this helps anyone using a PC-V, Autotune, and POD-300, as it should yield a highly refined fuel table.
     
  3. Claviger

    ClavigerHP Junkie extraordinaire

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  4. Claviger

    ClavigerHP Junkie extraordinaire

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    An added benefit for Boosted bikes:

    You can command ignition timing based on boost, so you can run retard timing based on boost, so for example, when your turbo starts running out of breath at high RPM you can slowly feed back in a little timing to help the bike make power and retard it more at peak boost when it really needs the timing pulled back for safety.

    This is far superior to RPM/TPS based timing retard and will allow you to minimize the chance of detonation while maximizing power output above peak boost. Since boost is built at slightly different rates in different gears, often it's hard to perfect your timing map without basing timing on pressure.

    This will allow you to avoid having to add a boost retard device common on many forced induction setups and do it all in one computer instead of using a hodge podge of devices to achieve the same thing.
     
  5. Claviger

    ClavigerHP Junkie extraordinaire

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    With some tweaking here's the granularity you can achieve with Pressure tables vs normal, which one do you think is going to run smoother when tuned?

    Normal PC-V Mode:
    granularity2.png

    Speed Density PC-V Mode:
    Granularity.jpg
     
  6. barbagris

    barbagrisMad Scientist

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    Oh you bugger! - And you know I tune for smooth.

    Do you force the F/L switch in TuneECU onto FUEL rather than LOAD?
     
  7. Claviger

    ClavigerHP Junkie extraordinaire

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    I have the F/L switch at 9-9-9-3-1-0 if memory serves. I may be changing that to all zeros and just using the PC-V for the MAP based fueling though. Essentially inverting the table so it’s F only tables from 0-1800 RPM and then F tables plus PC-V speed density from 2000-8000. This is achieved by setting the AFR target tables below 2000 to zero.

    This I do because so don’t get good data at low RPM the wideband is kind of challenged at low load and low rpm with my exhaust setup and reversion screws up the AT function.

    We’ll see, will follow up with results this weekend when complete retuning using this method.

    This should also make dialing in the bigger injectors easier.
     
    Last edited: Jun 7, 2018
  8. CrzystghndKC

    CrzystghndKCTriumph guy happy he didn't work for Harley.

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  9. barbagris

    barbagrisMad Scientist

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    Hmmmm - I am off to look for a posi-tap to connect to the MAP output. I have just ordered more anyway.
    And I suppose I'll have to use windows again :x3:

    I already set AFR to 0 at low rpms (also 2000 iirc) but only in gears 1(which is also Neutral according to Dynojet) and 2.

    This pressure thing is something I have avoided so far as I assumed it was going to be difficult.
    You just had to make it easy, didn't you - my missus will be wanting to give you a good talking to now. ;)

    btw - I set the POD to light characters on dark display. Much easier to read.
     
  10. Claviger

    ClavigerHP Junkie extraordinaire

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    For forced induction guys you could use one of these to get a good balanced aggregate vacuum/boost signal to feed the PC-V and get a reliable vacuum signal. It would allow you to use a 3 BAR map sensor and not have to mess with the stock map setup, thereby allowing the ecu to continue to read the individual cylinder vacuum amounts like original. Simply remove the EVAP canister crap, use the now unused vacuum ports on each runner and tap them to the manifold block, then run one line from the manifold block to your 3 bar and Bob's your uncle.
    vacuum manifold.jpg

    After initial trials I found the vacuum buffer not required, but will certainly help smooth the signal and thereby fueling. The vacuum signal does fluctuate a lot at cruising speeds causing afrs to swing up and down by about 0.25-0.5. I will be adding the buffer to my setup and using a second stock MAP sensor dedicated to the PC-V.
     
    Last edited: Jun 10, 2018
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