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01-02-2008, 11:02 PM | #1 |
Scooby Guru
Member#: 71092
Join Date: Sep 2004
Chapter/Region:
MWSOC
Location: Licking County, Ohio
Vehicle:2005 2.5RS Wagon Regal Blue Pearl |
Why Is The Engine Knocking Like Mad During Cold Snap?
OK, so we got hit by a cold snap today, about 20F colder than I've ever logged the car. I actually recorded an IAT of 5F as I started up the car! For some reason, the car was knocking LIKE MAD today. Very, very frequent knock and HUGE corrections (like 5-7 degrees FLKC+FBKC). Once the car got hot enough than the under-hood temps pushed the IATs up into the 60s (about 30 minutes of driving), the knock dropped back down to about what I've been seeing lately.
What gives? At first I thought maybe the colder air was dense enough to raise my load (increased load->increased knock), but once I looked at the data again, it's was having a fit even at part-throttle where the loads were no higher than I had been seeing (~0.6-0.8g/rev). What the heck was going on while it was so cold? |
01-02-2008, 11:12 PM | #2 | |
Scooby Specialist
Member#: 115021
Join Date: May 2006
Chapter/Region:
MAIC
Location: R.I.P Edwin 1985-2009
Vehicle:335i TurboXs~juiced AnDrEwTeCh~BuIlT |
Quote:
What kind of oil do you use?, & And when have you changed it? It is common for a slight knock in the Bloody cold, Thats why its good to use 0w30 or 0w40 In the Cold... |
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01-02-2008, 11:14 PM | #3 |
Scooby Guru
Member#: 71092
Join Date: Sep 2004
Chapter/Region:
MWSOC
Location: Licking County, Ohio
Vehicle:2005 2.5RS Wagon Regal Blue Pearl |
5w30 Royal Purple, about 1k miles into the OCI.
Keep in mind, I'm not talking about a knocking sound, I'm talking about knock events as recorded by the ECU. |
01-02-2008, 11:17 PM | #4 |
Scooby Newbie
Member#: 122595
Join Date: Aug 2006
Chapter/Region:
NWIC
Vehicle:2005 LGT Wagon ABP |
Are you telling me that your IAT is 60F when ambient is 5F? Do you have some kind of short ram intake?
Your IAT should only be 5 to 10F higher than ambient. Did you look at your total timing? Take a look at ignition compensation by coolant temperature and ignition compensation by IAT. |
01-02-2008, 11:19 PM | #5 |
Scooby Specialist
Member#: 115021
Join Date: May 2006
Chapter/Region:
MAIC
Location: R.I.P Edwin 1985-2009
Vehicle:335i TurboXs~juiced AnDrEwTeCh~BuIlT |
Plugs,Timming Belt?
Oh and if it gets colder~ do drop down in a 0w, Add life to your motor. |
01-02-2008, 11:26 PM | #6 |
Scooby Guru
Member#: 71092
Join Date: Sep 2004
Chapter/Region:
MWSOC
Location: Licking County, Ohio
Vehicle:2005 2.5RS Wagon Regal Blue Pearl |
The IATs, once the car is fully warmed, have never been lower than 30F above ambient. In fact, unlike the turbo cars, my IATs actually DROP during repeated 2k-redline WOT pulls. The stock RS intake pulls from inside the engine bay above the ABS thingy. It is most definitely a Hot Air Intake.
Though I wasn't logging coolant temp today, based on past experience, at the time I was getting the knock, the coolant temp would have been between 170 F and 195F. If it's knocking at cold IATs, is changing the IAT temp compensation the correct way to fix it, or just a bandaid? This is what the stock Timing Compensation (Intake Temp) table looks like: Code:
IAT in Degrees Farenheit -40 -22 -4 14 32 50 68 86 104 122 140 158 176 194 212 230 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -3.16 -3.87 -3.87 -3.87 -3.87 -3.87 -3.87 Code:
Coolant Temp in Degrees Farenheit -40 -22 -4 14 32 50 68 86 104 122 140 158 176 194 212 230 15.12 15.12 15.12 9.84 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Code:
Coolant temp in Degrees Farenheit -40 -22 -4 14 32 50 68 86 104 122 140 158 176 194 212 230 4.92 4.92 4.92 4.92 4.92 4.92 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 -1.05 -3.16 |
01-03-2008, 01:07 AM | #7 |
Scooby Specialist
Member#: 103320
Join Date: Dec 2005
Location: Oklahoma City
Vehicle:1998 swapped Forester L |
probably just an issue with cold internals. do you have an oil temp gauge? it takes 15-20 minutes for my oil to come up to full operating temps (90C). This is approximately 5 times longer than coolant temp! Most people mistake coolant temp to be operating temp, which is incorrect.
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01-03-2008, 03:51 PM | #8 |
Scooby Specialist
Member#: 15652
Join Date: Feb 2002
Chapter/Region:
TXIC
Location: sugar land, katy
Vehicle:2002 2.5L WRX Wag. 160K club |
I have the same issue. I find that my car has these little "transistions" where FLKC is going to happen and has to do with IAT, RPM, and Load. One day it will be good, the temps drop, it knocks, I advance the timing the knock goes away. IT warms up, and still no knock...go figure.
I am taking the path of advancement till no knock, and if it knocks when it gets warm, then I will start to mess with the compensation scaling. I have an EGT gauge and can get what I consider a fairly good representation of if I can go higher with advance. something to consider. |
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