MS3x Fuel cut when IdlePWM > 38%? - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 05-13-2014, 01:04 PM   #1
Newb
Thread Starter
 
Join Date: Mar 2012
Location: Austria
Posts: 15
Total Cats: 1
Default MS3x Fuel cut when IdlePWM > 38%?

Hi

I got a second problem with my MS3x
I tried to find out the max. Idle open Duty for Closed-Loop-Idle and therefore set it to warmup mode and changed the values untill the rpm changed no more.

At least that was the plan.
When setting IdlePWM higher than 38%, rpms start hunting, AFRs going very lean while rpm is falling even though PW and Spark are still there (according to log)

Have I reached the non-linear part of the Idle Valve? Would that explain this behaviour?

I attached a datalog. Everything is fine till I turned up IdlePWM to 40% (326sec in the log)
Attached Files
File Type: msl Hunting Idle at PWM40_2014-05-13_13.20.42_LOG0246.msl (1.39 MB, 81 views)
David_G is offline   Reply With Quote
Old 05-13-2014, 04:06 PM   #2
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

did you add a flyback diode to 12v on your idle out?

your idle valve should be working between ~25-65%

without it, the valve has an effect range of like 10% from open to closed.
Braineack is offline   Reply With Quote
Old 05-13-2014, 04:09 PM   #3
Newb
Thread Starter
 
Join Date: Mar 2012
Location: Austria
Posts: 15
Total Cats: 1
Default

Yes, I did
directly on the Tyco ECU Connector

At Idle I am at about 26%, less does not give me faults but rpm is too low to be usable

CrankingPWM is set to 51%, so it should work fine at those PWM, I guess
But it just doesn't

Last edited by David_G; 05-13-2014 at 04:34 PM.
David_G is offline   Reply With Quote
Old 05-14-2014, 04:09 AM   #4
Newb
Thread Starter
 
Join Date: Mar 2012
Location: Austria
Posts: 15
Total Cats: 1
Default

I'm such a noob
Yesterday night, I found out that when %PWM where above 40, it caused the rpm going uptop 1500-1600 which lowered MAP to about 25kPA (TPS closed)

Those low kPA at idle caused the overrun fuel cutoff to activate very shortly, rpm sank again, rised because of high PWM, then again fuel cutoff, ... and so on and so on

What's strange though is, that the fuelcut-light did not light up and also in the logs it didn't show any PW changes.
I guess thats because I have set it to progressive fuelcut, so only a few Zylinders caused the rpm drop, but PW stayed where they use to be at normal running
But then again, the fuelcut-light still should have come on...
David_G is offline   Reply With Quote
Old 05-14-2014, 09:36 AM   #5
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

weird. I wouldn't think overrun would activate during CL idle. But I could never get idle to happen anywhere close to 25kPa, even at that RPM.

I had my overrun set to 28kPa, IIRC, and I typically idled at 31-33kPa. So overrun would only activate if I surpassed my typically idle load and it'd return fuel before that point for a smooth transition to idle without dips.
Braineack is offline   Reply With Quote
Old 05-14-2014, 12:28 PM   #6
Newb
Thread Starter
 
Join Date: Mar 2012
Location: Austria
Posts: 15
Total Cats: 1
Default

I set it back to warmup mode to try out the different IdlePWM's (recognized to late that there is a test mode for such things )
I set fuel overrun to activate above 1500rpm and below 30kPa or so, can't remember

Normally the rpms are never that high (or kPa that low) with closed throttle, so it was an uncommon situation, but still...
Maybe I will change back the settings where they were to find out why the light did not come on.

But first I have to eliminate those nasty sync losses
David_G is offline   Reply With Quote
Old 05-14-2014, 12:30 PM   #7
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,809
Total Cats: 1,780
Default

I'd just completely disable overrun and try to same again to really rule it out.
Braineack is offline   Reply With Quote
Old 05-14-2014, 12:35 PM   #8
Newb
Thread Starter
 
Join Date: Mar 2012
Location: Austria
Posts: 15
Total Cats: 1
Default

Yeah, I already did that and it worked fine then.
My IdlePWM range is 22%-70%, so everything fine

I then turned overrun-cutoff back on and changed it to only come on above 22kPa.
Bingo, IdlePWM still can be set to 50% or whatever without getting those rpm fluctuations.

Now that I know that was the problem, I switched overrun fuelcutoff on again and set it back to 28kPa, because in reality I won't get those high rpms at idle anyways
David_G is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
Walbro 255lph Fuel Pump $50 lsc224 Miata parts for sale/trade 2 10-01-2015 10:17 AM
"Chimney Ethanol" E100 MiataGarage Engine Performance 5 09-30-2015 12:04 AM
Got bad Crank Angle Sensor and Random Misfire codes, but runs fine. Greasyman General Miata Chat 2 09-28-2015 11:44 AM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 03:38 AM.