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SVTPerformance's Chain of Restaurants
Tuning À la carte
Idle tuning help Vortech SC / Comp Cams XE270
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<blockquote data-quote="Bullitt5566" data-source="post: 15208295" data-attributes="member: 119066"><p>Getting closer thanks to Decipha's write-ups, I thought I had it last night but this morning same crappy stalling idle. </p><p></p><p>I started on Saturday. I disconnected the IAC and TP plugs then set the throttle stop at the lowest RPM the car would steadily idle. About 800 rpm.</p><p>Then I datalogged the MAF counts, RPM, IAC Integrator (Air Flow Error), and IAC Duty Cycle.</p><p>I translated the MAF counts to Air Flow #/Min because I could not find another value to give the data directly.</p><p>Then I found the air flow at 800 rpm by multiplying the AF*(800/840 (actual rpm)). I multiplied that by the IAC duty cycle. And added the IAC Integrator Error #/min.</p><p>I set the Throttle Body Air Flow (100% - IAC Duty Cycle%)*AF</p><p>Set the dashpot decy and preposition. </p><p></p><p>That worked. Steady 800-850 rpm idle, IAC duty cycle 30%, and IAC Integrator 0 error.</p><p></p><p>Blip the throttle... and... Idle comes down, hangs for a second then drops to 400rpm almost stalls and recovers. FAIL! </p><p></p><p>Sunday back to datalogging. I noticed that the idle source kept hitting the MBT/MAX limit (Idle source 1). Datalogged the sprark, load, rpm. </p><p></p><p>Found that after a throttle blip the ECU was advancing the timing to catch the idle but clipping. I raised the MBT and MAX timing tables at low load and rpm.</p><p></p><p>Ended up at over 60 degrees. Then I ran into the Borderline Knock table limiting spark error, I raised that too. </p><p></p><p>The result. Seemed like it worked. Blip the throttle, rpm would drop, and stop at 800 rpm. NO DIP! </p><p></p><p>This morning, FAIL! The car kept stalling. So I flashed back to the tune from Saturday, before messing with the timing.</p><p></p><p>So I think raising the MBT/MAX timing to allow the ECU the room to correct the idle was OK, but raising the Borderline Spark was incorrect.</p><p></p><p>This afternoon, I'll set the borderline spark back to stock at low RPMs and see how that works. </p><p></p><p>Does anyone have any insight/recommendations into setting spark advance at idle?</p><p></p><p>Some key parameters</p><p>Spark Gain is 1.0999</p><p>Min Spark is 0</p><p>MBT/MAX is now 60 degrees in the lower 12 cells RPM below 2000/Load below .200</p></blockquote><p></p>
[QUOTE="Bullitt5566, post: 15208295, member: 119066"] Getting closer thanks to Decipha's write-ups, I thought I had it last night but this morning same crappy stalling idle. I started on Saturday. I disconnected the IAC and TP plugs then set the throttle stop at the lowest RPM the car would steadily idle. About 800 rpm. Then I datalogged the MAF counts, RPM, IAC Integrator (Air Flow Error), and IAC Duty Cycle. I translated the MAF counts to Air Flow #/Min because I could not find another value to give the data directly. Then I found the air flow at 800 rpm by multiplying the AF*(800/840 (actual rpm)). I multiplied that by the IAC duty cycle. And added the IAC Integrator Error #/min. I set the Throttle Body Air Flow (100% - IAC Duty Cycle%)*AF Set the dashpot decy and preposition. That worked. Steady 800-850 rpm idle, IAC duty cycle 30%, and IAC Integrator 0 error. Blip the throttle... and... Idle comes down, hangs for a second then drops to 400rpm almost stalls and recovers. FAIL! Sunday back to datalogging. I noticed that the idle source kept hitting the MBT/MAX limit (Idle source 1). Datalogged the sprark, load, rpm. Found that after a throttle blip the ECU was advancing the timing to catch the idle but clipping. I raised the MBT and MAX timing tables at low load and rpm. Ended up at over 60 degrees. Then I ran into the Borderline Knock table limiting spark error, I raised that too. The result. Seemed like it worked. Blip the throttle, rpm would drop, and stop at 800 rpm. NO DIP! This morning, FAIL! The car kept stalling. So I flashed back to the tune from Saturday, before messing with the timing. So I think raising the MBT/MAX timing to allow the ECU the room to correct the idle was OK, but raising the Borderline Spark was incorrect. This afternoon, I'll set the borderline spark back to stock at low RPMs and see how that works. Does anyone have any insight/recommendations into setting spark advance at idle? Some key parameters Spark Gain is 1.0999 Min Spark is 0 MBT/MAX is now 60 degrees in the lower 12 cells RPM below 2000/Load below .200 [/QUOTE]
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