MS3x Hot soak stall on innitial start up - 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 09-07-2016, 07:07 PM   #1
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default MS3x Hot soak stall on innitial start up

I've done a bunch of searching and googling on this one and haven't found an answer that pertains to this set up. ( 95' 1.8, 5-speed, Braineack MS3x, Flow Force 640's, FMII with GT2560R )

The cold start seems pretty good. Although, once you bring rpm's up at all, the idle seems to stay high (around 1200 or so) . Putting the IAC in test mode drops the idle instantly to around 850 or so. Perhaps this is unrelated but I thought I'd mention it.

Attached is a Data log. I realized after I recorded the log I had the EGO Authority set to 0 as I had just been Auto tuning and forgot to set it back. The vehicle does this behavior even with the EGO at 15%.

Would someone take a look at the data log and tell me what they think? Thanks in advance.


Attached Files
File Type: msl 2016-09-07_17.59.41.msl hot start.msl (1.23 MB, 18 views)
Darkwood 1 is offline   Reply With Quote
Old 09-07-2016, 08:58 PM   #2
Boost Czar

iTrader: (60)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 70,930
Total Cats: 1,469
Default

inital duties table is probably a bit on the high side if it hovers before it stabilizes low.


you need like 10% more fuel in your VE idle table. you wont idle well if you're that lean -- the swing in RPMs has a lot to do with your wild swings in AFR.


Tune/stabilize you VE Idle Fuel Table -- get it to idle at 14.0:1 and the rest will follow.

Braineack is online now   Reply With Quote
Old 09-08-2016, 08:19 PM   #3
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default

Quote:
Originally Posted by Braineack View Post
inital duties table is probably a bit on the high side if it hovers before it stabilizes low.


you need like 10% more fuel in your VE idle table. you wont idle well if you're that lean -- the swing in RPMs has a lot to do with your wild swings in AFR.


Tune/stabilize you VE Idle Fuel Table -- get it to idle at 14.0:1 and the rest will follow.
Thanks for the quick reply, I will work on tuning the VE idle fuel table then.

I'm not sure what the "initial duties table" is. What would I be looking for here?

Thanks.
Darkwood 1 is offline   Reply With Quote
Old 09-09-2016, 06:52 AM   #4
Boost Czar

iTrader: (60)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 70,930
Total Cats: 1,469
Default

Initial duties table is the pwm% the idle vale defaults to before it enters CL.

Braineack is online now   Reply With Quote
Old 09-10-2016, 02:11 PM   #5
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default

Quote:
Originally Posted by Braineack View Post
Initial duties table is the pwm% the idle vale defaults to before it enters CL.
Thanks Braineack, bringing the values down a bit in the initial duties table fixed the high idle issue.

I'm working on the idle VE table trying to get a stable AFR. The vehicle idles well under every condition except for the hot soak start.

I'm still experiencing the big swing in AFR's and the stall after the vehicle sits hot for a while. It seems that when the IAT reads 130 or more at start up is when this occurs. AFR's swing back and forth going very lean for a brief time until the IAT temp comes back down, then it is fine again.

I looked at trying to calibrate the AIT (MAT) to have a different value at 130* plus but can't seem to find the option in Tuner Studio. Any thoughts?
Darkwood 1 is offline   Reply With Quote
Old 09-10-2016, 02:19 PM   #6
Boost Czar

iTrader: (60)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 70,930
Total Cats: 1,469
Default

make sure your MAT corrections table is 100% across.
Braineack is online now   Reply With Quote
Old 09-11-2016, 05:07 PM   #7
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default

Thanks Braineack, I decided not to mess with the MAT corrections.

I came up with a potential fix for the "Hot Soak" start that is outside of the tuning of MS.

I hooked up my stock PRC solenoid to a momentary on switch, as it was just an experiment and I didn't want to accidentally leave the switch on after a hot start usage. I warmed up the vehicle and tried to recreate the hot soak start condition. I push the button and keep it held in and start the vehicle and the idle is reasonable and doesn't stall. I let it out after a bit and I can see the AFR's stabilize. I found that activating the PRC at idle rich-ens up the AFR's by 2 points or more (16.0 : 1 raises to more than 14.0 : 1) and this is most likely how the factory ECU handles the hot soak condition.

Has anyone else experimented with this idea? I'm now thinking of how I might try to get MS3 to activate the PRC at a certain temp on start up and / or run it for a certain time at hot start. Any thoughts on how this might be done? If not, the "Hot Soak" switch might be a "low brow" fix.

It seems others who switch to a MS have this issue to some degree or another, and it dawned on me that the PRC probably gets thrown in the trash bin when making the conversion and thus creating this condition.

I will continue this experiment and report back with my findings.

Last edited by Darkwood 1; 09-11-2016 at 06:51 PM.
Darkwood 1 is offline   Reply With Quote
Old 09-12-2016, 06:54 AM   #8
Boost Czar

iTrader: (60)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 70,930
Total Cats: 1,469
Default

Looking at your log it doesn't look like MAT corrections is the issue.

I'm curious to see a log at idle when you AITs are not elevated. I think you have general tuning issues.

Consider this: I had no issues tuning a N/A car last weekend with AIT temps averaging 160F and would hit >190F
Braineack is online now   Reply With Quote
Old 09-12-2016, 07:01 PM   #9
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default

Quote:
Originally Posted by Braineack View Post
Looking at your log it doesn't look like MAT corrections is the issue.

I'm curious to see a log at idle when you AITs are not elevated. I think you have general tuning issues.

Consider this: I had no issues tuning a N/A car last weekend with AIT temps averaging 160F and would hit >190F
OK, thanks. I'm beginning to think my hot soak issue may not be related to the IAT then, as mine will do it only after the car has sat for maybe 15 min or so after being shut down. My IAT temps are not all that high at that point. Perhaps it is in the tune but being new to MS I'm at a loss.

Attached is my current data log after enriching about 10% over the previous log. I drove the car to warm it up and then restarted the car after starting the data logging. My EGO correction is on, I can re-do it with it off if that works better.
Attached Files
File Type: msl 2016-09-12_18.28.22.msl warm.msl (3.18 MB, 25 views)

Last edited by Darkwood 1; 09-12-2016 at 07:25 PM.
Darkwood 1 is offline   Reply With Quote
Old 09-13-2016, 08:23 AM   #10
Boosting since 1984
iTrader: (1)
 
stefanst's Avatar
 
Join Date: Sep 2011
Location: Levittown
Posts: 1,012
Total Cats: 41
Default

Injector heat soak is likely your problem. Drop your idle AFR target to 13.5 and make sure you got your dead-times correct. Also allow EGO correction in idle.
stefanst is offline   Reply With Quote
Old 09-14-2016, 06:21 PM   #11
Newb
Thread Starter
 
Join Date: May 2016
Location: Monson, MA
Posts: 10
Total Cats: 1
Default

Quote:
Originally Posted by stefanst View Post
Injector heat soak is likely your problem. Drop your idle AFR target to 13.5 and make sure you got your dead-times correct. Also allow EGO correction in idle.
Lots of good information on this forum, Thank you for your post.

I checked my injector dead time and it was set to 1.2. I looked up Flow Force's recommended number and they show 1.12. So I changed it to 1.12 and the car started running super lean. I did a bit of tuning to try to get it back to being 14.0. Driving it required more auto tuning.

I then remembered setting the Req. Fuel with the numbers Flow Force sent with the injectors. These are 640 cc's that flow tested to 670cc's. So I set the Req. Fuel up with those numbers. Just to see if it would richen up enough, I changed the req. fuel by doing the calculation with 640 instead. The engine richened up across the board and with this new combination, idles better.

I then tinkered with the idle VE again to try and target an AFR closer to 13.5. I found I was able to get the highest vacuum reading (greater vacuum that is) working in the 13.5:1 area but it starts to get a bit stinky (still have the cat installed). I remember the stock ECU targeting close to 14.7:1 and wonder if 13.5:1 is a bit too rich.
Darkwood 1 is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
1.8 EWG gt2560 LownSlow616 Build Threads 87 03-25-2017 10:12 PM
NB8a cold running oddity nitrodann DIY Turbo Discussion 12 09-07-2016 07:18 AM
Lean and high idle after sequential conversion WhiteMx-5 MEGAsquirt 13 09-06-2016 09:38 PM
Tune Chages Before Boost? MiataMan00 MEGAsquirt 0 09-02-2016 02:39 PM
Auto Tune, a better way? ryansmoneypit DIY Turbo Discussion 23 09-02-2016 11:03 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 11:45 AM.