LPG injection, AFR goes pisrich on first cold start
Posted: Wed May 05, 2021 4:36 am
hello guys,
I havent been around for a while, because I have been mostly on the MSEXTRA forum getting my Megasquirt system up and running:
This is the link to my tuning story so far:
https://www.msextra.com/forums/viewtopi ... 31&t=74475
I upload updates there whenever I have made progress.
Some info on my setup:
GMC C15 Suburban, see projectpage in my signature
engine: 454 Chevy Big Block low compression about 8:1
single fuel: only LPG injection
ECU: Megasquirt MS3X (see tune in attachments)
Reducer: Tomasetto AT13XP set at 150 kPa gas pressure (rail pressure - MAP)
Injectors: Valtek 30 BFC, 3 Ohm, drilled to 2.65mm (need to increase that, because I have 100% dutycycle at 4500 rpm)
Peak&Hold boards (4A/1A) from SECU-3.org
I have extra sensors for LPG connected in one integrated unit:
- gas pressure (mpxh6400a)
- gas temperature (10 kOhm NTC)
- external MAP sensor (mpxh6400a)
Ignition is:
FAST dual sync distributor for crank and cam signal
8x LS D585 coils at 3.5ms dwell
I have been chasing a weird cold start problem that started after I made a long trip of 2hours (long for my standards) to our holiday destination.
Car ran fine the whole trip. no problems.
Then after sitting for 5 days I tried to start it. started. ran fine for 10seconds and then it started going rich....psrich..AFR dropped below 10 and then it started misfiring and eventually stalled.
damnit...
It had been a cold night and it was close to freezing that morning.
I have cranked the car at lower temperatures and hev never had this problem before. So I figured must be a hardware problem. I have since then:
- replaced the reducer
- replaced the injectors (from GIAC to Valtek)
- repaced the single coil to 8 LS coils for better spark
- replaced the plug wires
- replaced the sparkplugs (it had #2 Delcos that were way too cold for this setup, now has the stock RT45TS)
and above 10C it seems fine.
But tried a cold start at 5C 2 days ago and again it went pisrich within 10-15s and allmost stalled. And it sounds like its misfiring. Runs really rough. like its working hard.
I now catch it by adjusting the WUE (warm up enrichtment) by hand. Usually Ill have to pull 15-30% fuel to keep the AFR between 13-15. Then when the engine gets to about 25-30C its gone and never returns untill the nex morning cold start after sitting a while.
Its driving me nuts, cause I cant seem to pinpoint what might be causing this.
So all ideas are welcome.
topic where I uploaded loads of log files and tunes about the rich start problem:
https://www.msextra.com/forums/viewtopi ... 49#p570549
I havent been around for a while, because I have been mostly on the MSEXTRA forum getting my Megasquirt system up and running:
This is the link to my tuning story so far:
https://www.msextra.com/forums/viewtopi ... 31&t=74475
I upload updates there whenever I have made progress.
Some info on my setup:
GMC C15 Suburban, see projectpage in my signature
engine: 454 Chevy Big Block low compression about 8:1
single fuel: only LPG injection
ECU: Megasquirt MS3X (see tune in attachments)
Reducer: Tomasetto AT13XP set at 150 kPa gas pressure (rail pressure - MAP)
Injectors: Valtek 30 BFC, 3 Ohm, drilled to 2.65mm (need to increase that, because I have 100% dutycycle at 4500 rpm)
Peak&Hold boards (4A/1A) from SECU-3.org
I have extra sensors for LPG connected in one integrated unit:
- gas pressure (mpxh6400a)
- gas temperature (10 kOhm NTC)
- external MAP sensor (mpxh6400a)
Ignition is:
FAST dual sync distributor for crank and cam signal
8x LS D585 coils at 3.5ms dwell
I have been chasing a weird cold start problem that started after I made a long trip of 2hours (long for my standards) to our holiday destination.
Car ran fine the whole trip. no problems.
Then after sitting for 5 days I tried to start it. started. ran fine for 10seconds and then it started going rich....psrich..AFR dropped below 10 and then it started misfiring and eventually stalled.
damnit...
It had been a cold night and it was close to freezing that morning.
I have cranked the car at lower temperatures and hev never had this problem before. So I figured must be a hardware problem. I have since then:
- replaced the reducer
- replaced the injectors (from GIAC to Valtek)
- repaced the single coil to 8 LS coils for better spark
- replaced the plug wires
- replaced the sparkplugs (it had #2 Delcos that were way too cold for this setup, now has the stock RT45TS)
and above 10C it seems fine.
But tried a cold start at 5C 2 days ago and again it went pisrich within 10-15s and allmost stalled. And it sounds like its misfiring. Runs really rough. like its working hard.
I now catch it by adjusting the WUE (warm up enrichtment) by hand. Usually Ill have to pull 15-30% fuel to keep the AFR between 13-15. Then when the engine gets to about 25-30C its gone and never returns untill the nex morning cold start after sitting a while.
Its driving me nuts, cause I cant seem to pinpoint what might be causing this.
So all ideas are welcome.
topic where I uploaded loads of log files and tunes about the rich start problem:
https://www.msextra.com/forums/viewtopi ... 49#p570549