MSPNP MSPNP specific Megasquirt related discussion.
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Injection Timing The Other Way Around

Old 11-26-2017, 07:01 AM
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Join Date: Nov 2017
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Default Injection Timing The Other Way Around

Admittedly I am new here as a member but have spent a fair amount of time reading here before becoming a member. I have searched and did not find reference to the thought in my head so I banged out the math and thought I would share what I came up with. I repeatedly see advice of setting sequential injection timing to end of event but I do not see any solid data why it is not a reasonable idea to set it to start of event other than the popular argument that pulsewidths "change all the time". The injector pulsewidth I see per range of load stays fairly consistent across a given RPM range so I thought, "Well how many degrees did I really turn to deliver that?" First I needed to figure out degrees traveled per millisecond by RPM. Then I would need averaged PW's to factor per range. This left me with the thought process of just starting on the other side of the event for delivery. Google made quick work of the degrees over time for me and I started populating an Excel table. Next was using MLVHD to show me the average PW at a given kpa and RPM. Lastly I needed to factor where to deliver. I realize the MSPNP2 actually starts the show on the power cycle at 0 degrees and our factory cams start opening 5 degrees BTDC on the induction stroke. Figuring it this way I calculated degrees times injector pulsewidth plus 365 would put me where I needed to be. I also thought if the pulsewidth goes a little under it will cool the valve and gas on the hot runner until the valve opens and if it is slightly larger that there would be 52 degrees of open time pulling atomized mist for a clean burn. Here is what I ended up with. Also, I'm not a professional tuner but want to learn so please educate me if I'm horribly in error. I'd also love to know if this has no prayer of working smoothly on a turbo setup as my TD05H-16G(evo3) is nearly ready to be installed. Borrowed without asking from Andy Whittle's Injector timing video on YouTube. I'm not getting paid so he shouldn't get mad. It shows our relative 0 and 360 points in relation and helped me visualize where I was at in the order. I set the ranges to kpa, RPM, and PW to display the data from a recent datalog

Top left is degrees over time. Top center is my average PW with 420cc RX8 injectors. Mid-center is degrees traveled by PW. Bottom center is the calulated delivery degrees.
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