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Understanding how to tune timing PV

Started by Dfpunch, October 19, 2018, 06:11:52 AM

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Dfpunch

Can anyone help me understand where to start, what to look for and how to tune spark tables. VE is cake. No specific build just dont fully understand spark and where to start.

KE5RBD

It is difficult to say the least.  Lot of folks say the Spark knock gives false readings.  It really isn't once you get the VE's and Spark advance tables working with each other.  If your VE is running Map then it is little easier as all spark tables are Map based.  If TPS then little harder to relate to what area you are in.  Map is load based and TPS is more related to Throttle position.  Lot of times the VE is too lean causing the spark knock.  You are not likely to get spark knock in the cruise area.  For map based that is 35 Kpa to 55 Kpa. for TPS based it is around 10% to 20%.  The Rpm range for cruise is around 1750 to 3500 with 3500 may be as high as 60 Kpa or 25 TPS depending on build.  You can pretty much use the 750 rpm to 1750 spark tables from the factory.  The Cruise area 2000 area around 30 is good starting point.  As you go up to 2500 around 36 and up to 2750 38 and 38 to 40 up to 3500 for cruise timing.  The timing has lot to do with heat control in cruise area also, particularly 2750 up.  Too low will tend to run hot also as will too lean.  The acceleration area is where it gets more difficult.  The factory timing is too high in most of this area.  I consider the acceleration area from 1750 up in the 55 Kpa to 100 or 20 TPS to 100 on the VE if Throttle based. Little hint that has worked for me is the WOT 90 to 100Kpa or TPS from 2500 up that 16 to 12 degrees is about all you need.  I have seen tunes fall on there face around 4500 WOT if timing is too high.  It may not spark knock but it will likely quit pulling if timing is around 20 up in that area.  Factory is sometimes 24+ and motor just doesn't seem to want to pull past 4000 WOT in the higher MPH 90+, but no one ever runs that fast.  Won't necessarily spark knock just won't pull.    In the 2500 range up at 20 TPS or 55 Kpa 24 to 16 is a likely running advance to start with.  If you are trying to optimize spark or VE without Datalogs and some software to analyze it will be most difficult and not a fast process either.  I use Mega Log Viewer and Know there are several other software packages like My Tune that can do this also. Takes about as much time to learn the software as it does to learn where you are on the VE table or the Spark Advance table.  In PV you can also play with idle timing with the idle spark advance table.  Try 20 degrees at 1000 rpms on one cylinder and 12 on the other.  Tends to give little lope if you like that.  This is above 90 F.  Below that you can run 22 or so.  It only comes into effect at closed throttle.  Also effects decel at closed throttle, but just in the rpm range listed.
2019 FLHTK Hammock Seat S&S MK 45 Slip ons Street Tuner.

Dfpunch