POP when turning ignition on (not cranking) and burned fuel smell - Page 3 - 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 10-02-2008, 08:12 PM   #41
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Quote:
Originally Posted by elesjuan View Post
If I've been switching the ignition on and off a lot without cranking / starting, once in a blue moon I'll get the 'pop.' Doesn't happen very often though unless I'm messing with something.



This might not be a real great idea. :P
Why?
patsmx5 is offline   Reply With Quote
Old 10-02-2008, 08:23 PM   #42
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by patsmx5 View Post
Why?
Because you're deliberately spinning up the turbo just before killing the oil supply. The engine will wind down almost immediately, whereas the turbo will keep going for a while.

I just don't have the problem on my car. If I've turned the key to run, waited for prime, and then switched off, waited some more, and then back on, then yeah, I'll occasionally get the pop.
Joe Perez is offline   Reply With Quote
Old 10-02-2008, 09:05 PM   #43
Elite Member
iTrader: (11)
 
Join Date: Jun 2007
Location: Overland Park, Kansas
Posts: 5,382
Total Cats: 43
Default

Quote:
Originally Posted by Joe Perez View Post
Because you're deliberately spinning up the turbo just before killing the oil supply. The engine will wind down almost immediately, whereas the turbo will keep going for a while.

I just don't have the problem on my car. If I've turned the key to run, waited for prime, and then switched off, waited some more, and then back on, then yeah, I'll occasionally get the pop.
Yep. If its really that big of a worry, put a kill switch on the fuel relay and just kick it off and let the car die.. It won't restart perfectly either because your fuel system is empty..
elesjuan is offline   Reply With Quote
Old 10-02-2008, 09:16 PM   #44
Senior Member
iTrader: (7)
 
Join Date: Aug 2007
Location: Southern Indiana
Posts: 1,371
Total Cats: -1
Default

Quote:
Originally Posted by Joe Perez View Post
I doubt it. Again, this initial spark event takes place before the MS really has a chance to do much else in terms of priming events. If you look at the source code, you'll see that the relevant output pins get initialized way before the real meat of the main loop starts happening.
The one thing that bothers me is the fact that my pop always happens 2 seconds after the key is turned on. I can change this by changing the "Fire priming pulse" option. If i change it to on power on, it happens almost instantly at key on. If it is set to after 2 seconds, it happens after 2 seconds.
wes65 is offline   Reply With Quote
Old 10-02-2008, 09:24 PM   #45
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Ah yes, I forgot some of yall have turbos.... Yeah don't do it then. But I' N/A :( and it doesn't hurt my motor. Not that I have a pop problem with EDIS. I just have a miss!
patsmx5 is offline   Reply With Quote
Old 10-03-2008, 03:29 AM   #46
Elite AbsurdFlow Member
Thread Starter
 
Laur3ns's Avatar
 
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,058
Total Cats: 11
Default

@wes65: I was observing the samen 0s or 2s delay. Maybe I should grab a timing light, turn the ignition on and see how many pulses I get and when... maybe that will tell me something.
Laur3ns is offline   Reply With Quote
Old 10-03-2008, 09:39 AM   #47
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,847
Total Cats: 1,788
Default

For those with TPS, you could try to use the flood clear at night while cranking...should expel/burn any excess gas....

TPS VALUE FOR FLOOD CLEAR
Sometimes you might want to temporarily stop the injectors from injecting fuel during cranking to clear a flooded engine. This is achieved by holding down the gas pedal during cranking. The MegaSquirt needs to know at what point of gas pedal deflection it should turn off the injectors and a good starting point would be just before floored.
Insert this value for the TPS Flood Clear.
Braineack is offline   Reply With Quote
Old 10-25-2008, 10:07 AM   #48
Newb
 
Join Date: Dec 2006
Location: U.K
Posts: 15
Total Cats: 0
Unhappy

I have the "turn the ignition on = BANG ! ".I had my MS p&p fitted and tunned by a well trusted tunner as i just don't have the know how/skill etc.He has tried a few fixes but has come up blank.So i am following this thread with interest

Car:97 1.8 na
FI = BRP MP62 SC
Injectors: 320 cc
dave_v is offline   Reply With Quote
Old 10-25-2008, 11:34 AM   #49
Elite AbsurdFlow Member
Thread Starter
 
Laur3ns's Avatar
 
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,058
Total Cats: 11
Default

@Brain: ign on while TPS=100=floodclear still results in a backfire. It just sounds different because it goes through the intake tract.
Laur3ns is offline   Reply With Quote
Old 10-25-2008, 11:36 AM   #50
Elite AbsurdFlow Member
Thread Starter
 
Laur3ns's Avatar
 
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,058
Total Cats: 11
Default

Another thought: while the MSPNP has all outputs high while booting, is this also the case while shutting down? Maybe the inj are pulsed during shutdown and depending on time and temperature there is enough combustable fuel in one or more cylinders that will burn during the next bootup (spark output high). Idea?
Laur3ns is offline   Reply With Quote
Old 10-25-2008, 12:12 PM   #51
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by Spookyfish View Post
Another thought: while the MSPNP has all outputs high while booting, is this also the case while shutting down?
I don't see how it would be possible on the injector channels. Unlike the ignition drivers, their natural tendency is to be off, and the CPU must pull the drive lines high to turn them on.

Even if this were not the case, though, I'm having trouble visualizing whether it would be possible for the fuel to hang around. The engine does not stop spinning the instant that you turn off they key. The internals have momentum, and the crank will continue to rotate for a little while (drawing air in, compressing it, expanding it, and exhausting it) as it slows down to a stop. I just have no idea how long the engine continues to rotate for. Would it complete a full cycle (two revolutions) thus clearing the intake tract and cylinders of residual fuel? I have no idea.

Here's a wild question: Those of you experiencing this problem, are you running lightened flywheels?
Joe Perez is offline   Reply With Quote
Old 10-25-2008, 01:04 PM   #52
Elite AbsurdFlow Member
Thread Starter
 
Laur3ns's Avatar
 
Join Date: Mar 2008
Location: Enschede, NL
Posts: 2,058
Total Cats: 11
Default

I have a lightened OEM flywheel (1.8).
Laur3ns is offline   Reply With Quote
Old 10-25-2008, 01:08 PM   #53
Newb
 
Join Date: Dec 2006
Location: U.K
Posts: 15
Total Cats: 0
Default

Quote:
Originally Posted by spookyfish View Post
i have a lightened oem flywheel (1.8).
+1
dave_v is offline   Reply With Quote
Old 10-25-2008, 02:19 PM   #54
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Quote:
Originally Posted by wes65 View Post
The one thing that bothers me is the fact that my pop always happens 2 seconds after the key is turned on. I can change this by changing the "Fire priming pulse" option. If i change it to on power on, it happens almost instantly at key on. If it is set to after 2 seconds, it happens after 2 seconds.
Quote:
Originally Posted by Spookyfish View Post
@wes65: I was observing the samen 0s or 2s delay. Maybe I should grab a timing light, turn the ignition on and see how many pulses I get and when... maybe that will tell me something.
This is interesting. Because the fuel doesn't just ignite on its own. So yeah it has got to be sparking a cylinder that has an open intake valve.

Quote:
Originally Posted by Joe Perez View Post
I don't see how it would be possible on the injector channels. Unlike the ignition drivers, their natural tendency is to be off, and the CPU must pull the drive lines high to turn them on.

Even if this were not the case, though, I'm having trouble visualizing whether it would be possible for the fuel to hang around. The engine does not stop spinning the instant that you turn off they key. The internals have momentum, and the crank will continue to rotate for a little while (drawing air in, compressing it, expanding it, and exhausting it) as it slows down to a stop. I just have no idea how long the engine continues to rotate for. Would it complete a full cycle (two revolutions) thus clearing the intake tract and cylinders of residual fuel? I have no idea.

Here's a wild question: Those of you experiencing this problem, are you running lightened flywheels?
I'd say the engine makes at least 3-5 full cycles before dying.

I definitely think a timing light on every cylinder is in order. See if they're all sparking on their own randomly or what. But GL finding 4 timing lights.
patsmx5 is offline   Reply With Quote
Old 10-25-2008, 08:10 PM   #55
Elite Member
iTrader: (21)
 
paul's Avatar
 
Join Date: Jun 2006
Location: Point Pleasant, NJ
Posts: 2,957
Total Cats: 2
Default

I run a stock flywheel and i get the pop 2 secs after i turn the key.
paul is offline   Reply With Quote
Old 10-25-2008, 08:24 PM   #56
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

I have never had this problem with MS2. I could turn the key on and off 10 times and then yeah it would be flooded and hard to start but never pops. Same with EDIS now I can flood it if I prime it enough but never does it pop.

Does everyone MS 1 deal with this and not talk about it?
patsmx5 is offline   Reply With Quote
Old 10-25-2008, 08:26 PM   #57
Elite Member
iTrader: (3)
 
Mach929's Avatar
 
Join Date: Oct 2004
Location: lansdale PA
Posts: 2,500
Total Cats: 0
Default

i get it maybe once every 20 cold starts, never hot
Mach929 is offline   Reply With Quote
Old 10-25-2008, 10:33 PM   #58
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Quote:
Originally Posted by patsmx5 View Post
Does everyone MS 1 deal with this and not talk about it?
No, it seems to be only a small subset of MS1 users, and I expect probably some MS2 users as well. I do not experiance this issue and never have, nor have many others that I've spoken to.

My strongest suspicion is that this is caused by injectors leaking tiny amounts of fuel into the intake runners after shutdown.

I'm also chewing on the very remote possibility that engines with light flywheels might not complete a full cycle of rotation after shutdown, thus leaving some fuel that has been injected but not ignited in the engine. Perhaps we can gather some empirical data on this topic.

Whatever the cause, I am nearly 100% certain that it is not due to fuel being injected at or immediately following turn-on. With no airflow through the engine, it does not seem plausible that fuel could travel from the injector all the way down the intake port and into the cylinder, while remaining sufficiently atomized to be easily ignitable, in the relatively brief period of time

I've got a MS sitting on my desk nearly completed at the moment, and I'm hoping to scope its squirt and spark output lines before I have to give it back to the owner, to establish an accurate timeline of what actually happens at power-up.
Joe Perez is offline   Reply With Quote
Old 10-26-2008, 01:35 AM   #59
Elite Member
iTrader: (24)
 
Join Date: Jul 2007
Location: Cypress, TX
Posts: 3,778
Total Cats: 35
Default

Count me in as a user who experiences this Phenomenon. I've got a 7lb flywheel and MS1. It ignites as soon as the key is turned to the ON position. I hate when I have to go searching for a vacuum cap that was just propelled from my intake manifold with explosive force.

Last edited by Bryce; 10-26-2008 at 02:45 AM.
Bryce is offline   Reply With Quote
Old 10-26-2008, 03:29 AM   #60
Junior Member
iTrader: (4)
 
Join Date: Oct 2007
Location: santa cruz
Posts: 246
Total Cats: 0
Default

My flywheel is 17# (OE NB)
I get the pop with great reliability.
More time between cold-starts means a greater pop.
2 pair of professionally cleaned injectors have behaved nearly identically in 2 different engines; all configurations have popped at every cold-start; MS has been the only commonality.
Seemingly all MT settings have been tested.
The condition remains.
chucker 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
Need help - Stock Balancer and Fastforward overlay pulleys Frank_and_Beans Supercharger Discussion 13 09-12-2016 09:17 PM
Walbro 255lph Fuel Pump $50 lsc224 Miata parts for sale/trade 2 10-01-2015 10:17 AM
01-05 Fab9 PNP COPs (used) FrankB Miata parts for sale/trade 6 09-30-2015 12:48 PM
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 11:55 PM.