MSPNP MSPNP specific Megasquirt related discussion.
Sponsored by:
Sponsored by:

What determines INITIAL startup idle duty?

 
Old 04-30-2017, 12:24 AM
  #1  
Senior Member
Thread Starter
iTrader: (2)
 
Onyxyth's Avatar
 
Join Date: May 2013
Location: Boyertown, PA
Posts: 729
Total Cats: 62
Default What determines INITIAL startup idle duty?

MSPNP2, 1.4.1 firmware. The issue I have is when starting the car it will zoom to ~2700 rpm for a few seconds and then slowly come down to ~1400 over the course of another 5 seconds or so. By then it's in closed loop and evens out. But what causes the initial high idle? I can't imagine revving to 2700 while the car has barely any oil pressure is doing it any good. I thought this was potentially the cranking idle duty, but that didn't make a difference.

I don't have logs at the moment but I can get some tomorrow. Just looking for a few spots to check first.
Onyxyth is offline  
Old 04-30-2017, 12:53 AM
  #2  
Junior Member
 
drizzay222's Avatar
 
Join Date: Feb 2016
Location: Mobile, AL
Posts: 45
Total Cats: 0
Default

You probably need to switch back to open loop and tune idle warmup duty until it behaves as you would like then switch back to running closed loop.
drizzay222 is offline  
Reply
Leave a poscat -2 Leave a negcat
Old 04-30-2017, 12:54 AM
  #3  
Elite Member
iTrader: (2)
 
Join Date: Aug 2016
Location: Woostuh, MA
Posts: 3,879
Total Cats: 108
Default

ridethecliche is offline  
Old 04-30-2017, 12:59 AM
  #4  
Senior Member
Thread Starter
iTrader: (2)
 
Onyxyth's Avatar
 
Join Date: May 2013
Location: Boyertown, PA
Posts: 729
Total Cats: 62
Default

I don't think there's any reason to switch back to open loop for this issue. Everything else works fine.

Originally Posted by ridethecliche View Post
Ya I should have. I'll post it tomorrow ASAP when I get to my tuning laptop (which is in the car ATM).
Onyxyth is offline  
Old 04-30-2017, 02:28 AM
  #5  
Design Engineer
iTrader: (1)
 
DNMakinson's Avatar
 
Join Date: Jan 2013
Location: Seneca, SC
Posts: 3,505
Total Cats: 468
Default

Im a bit confused by your combination is a MSPNP, which I understand is a MS2 variant, and 1.4.1 FW.

Nonetheless, for MS3, there is this:



Similarly, for MS2, there is this:

DNMakinson is offline  
Old 04-30-2017, 10:14 AM
  #6  
Senior Member
Thread Starter
iTrader: (2)
 
Onyxyth's Avatar
 
Join Date: May 2013
Location: Boyertown, PA
Posts: 729
Total Cats: 62
Default

Originally Posted by DNMakinson View Post
Im a bit confused by your combination is a MSPNP, which I understand is a MS2 variant, and 1.4.1 FW.

Nonetheless, for MS3, there is this:



Similarly, for MS2, there is this:
Sorry it's 3.4.2 firmware. The one with the sliders for idle control.

Anyway that's the exact option I was tinkering with but it did not seem to make a difference. Maybe I'll try larger/smaller values.
Onyxyth is offline  
Old 04-30-2017, 10:21 AM
  #7  
Design Engineer
iTrader: (1)
 
DNMakinson's Avatar
 
Join Date: Jan 2013
Location: Seneca, SC
Posts: 3,505
Total Cats: 468
Default

The only other variable, assuming your CL idle values, such as targets and dashpot are correct, is the Crank-to- Run Taper that controls how many seconds the Crank Duty Steps are held.

Last edited by DNMakinson; 04-30-2017 at 10:22 AM. Reason: Spelling
DNMakinson is offline  
Old 04-30-2017, 10:47 AM
  #8  
Cpt. Slow
iTrader: (25)
 
curly's Avatar
 
Join Date: Oct 2005
Location: Oregon City, OR
Posts: 12,762
Total Cats: 676
Default

Originally Posted by Onyxyth View Post
But what causes the initial high idle?
Hopes and dreams. Certainly not software calculations.

Switch to open loop, never look back, and enjoy life.
curly is offline  
Old 04-30-2017, 11:09 AM
  #9  
Boost Czar
iTrader: (62)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 76,361
Total Cats: 2,294
Default

idle cranking duty/steps table. same as with warmup.

what you need to tune now is the idle initial values table (and activate it) as well as the RPM targets tables, so you can give the PID code a rough place to start
Braineack is offline  
Old 04-30-2017, 05:47 PM
  #10  
Senior Member
Thread Starter
iTrader: (2)
 
Onyxyth's Avatar
 
Join Date: May 2013
Location: Boyertown, PA
Posts: 729
Total Cats: 62
Default

Originally Posted by curly View Post
Hopes and dreams. Certainly not software calculations.

Switch to open loop, never look back, and enjoy life.
There is no hope. I'm switching to open loop.

Kidding - it was Idle Cranking Duty as DNMakinson pointed out. I just wasn't using small enough values when I tried last time. I have it set to rev to about ~1500 on cold start, with a 4 second crank-to-run taper. Everything works great now. poscats all around.
Onyxyth is offline  
Old 04-30-2017, 05:57 PM
  #11  
Elite Member
iTrader: (2)
 
Join Date: Aug 2016
Location: Woostuh, MA
Posts: 3,879
Total Cats: 108
Default

It really helps to go through all the values on your range using the idle valve test mode and noting the important rpm: idle valve relationships that are important to the initial startup values you want.
ridethecliche is offline  
 


Thread Tools
Search this Thread

Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.