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Old 08-11-2018, 07:28 PM   #1
John Connor
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Join Date: Aug 2018
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2004 FXT 5 speed
Silver

Default Is my knock sensor toast?

I just did my first data log with RomRaider and I think my ecu thinks I'm experiencing knock. I've heard knock before and it isn't happening. I do have a good bit of experience with hondata and some light K20 tunning, but this is my first foray into Subaru's and boost.

I'm seeing a Knock correction advance of between 2 and 8 degrees that starts around 3,000rpms and goes till redline. It fades in and then tappers off towards the end of the pull. I'd upload the XML file, but I'm not sure how to do that here.

My car is also only hitting ~10psi when its cooler and ~8psi when it's warm out.

No mods
112,000 miles

If this is in the wrong sub-forum, I'm sorry. Thanks in advance for any help.
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Last edited by John Connor; 08-12-2018 at 12:27 PM.
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Old 08-12-2018, 12:24 PM   #2
John Connor
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Member#: 489892
Join Date: Aug 2018
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Location: Moscow, Idaho
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2004 FXT 5 speed
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Here is a log I pulled this morning in third gear with ~65 degree F temps outside.

https://docs.google.com/spreadsheets...it?usp=sharing

My IAM is steady at 1, which I know is important, but not sure exactly why yet
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Old 08-13-2018, 12:07 AM   #3
John Connor
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Location: Moscow, Idaho
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2004 FXT 5 speed
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Decided to download the factory tune from RomRaider and check/replace the spark plugs. The spark plugs looked normal and the flash went fine. Knock sensor still saying I have crazy knock, but you’d think I’d see signs of it on my plugs if that were true...

Knock sensor is getting changed out tomorrow and if that fails to fix things, I’ll go get a compression test and then check the injectors.

Any input on my log and if I’m looking at real knock, or not, would be greatly appreciated.
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Old 08-13-2018, 01:10 PM   #4
X49
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Knock Correction Advance does not measure knock. It is what would normally be called Dynamic Advance in Cobb Accesstuner. It is how much timing advance is added to base timing when your IAM is at 1.0. These values will be reduced when your IAM is less than 1.0. It is not something you have to log.

Feedback Knock Correction (FBK) and Fine Knock Learning Correction (FKL) are indications of knock. FBK is real-time knock. FKL is when the engine learns what load ranges knock occurs and pulls timing pre-emptively. You have an FKL reading of -2.46, which is a concern. It's almost certainly due to real knock. You won't actually hear small knock events in these engines, nor will they necessarily damage your plugs. The cause is either running too lean or having too much ignition advance for the fuel you're using.

Edit: It looks like you actually are hitting peak boost. I'm not familiar with RomRaider, but Target Boost is about 0.7, which I assume is supposed to be 0.7 bar, which is 10.3 psi. I'm assuming you're using a base map with low boost settings.

You're probably getting knock due to MAF scaling issues, causing you to run lean. If you don't have a wideband O2 sensor, you can't actually tune this yourself, so just decrease ignition timing at the rpms and loads where you are experiencing knock.

The next step is to dial in your boost by modifying your boost tables and wastegate duty cycle tables. I'd suggest starting with a better base map that has target boost close to where you want it, to make things easier. Once your boost curve is how you want it, you can move on to dialing in ignition timing. I'd suggest doing a lot of reading first. You don't really seem to know what you're doing.

Last edited by X49; 08-13-2018 at 01:32 PM.
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Old 08-13-2018, 05:12 PM   #5
John Connor
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Thanks for the reply!

Is it normal for a factory car without any mods and a factory tune, running high octane gas to get knock and need its MAF scaled?
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Old 08-13-2018, 05:57 PM   #6
John Connor
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Also, I thought that stock boost for an 04 FXT was ~1BAR?
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Old 08-13-2018, 06:10 PM   #7
X49
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It's pretty common for a MAF to be poorly scaled. It's probably the most common cause of knock. Sometimes they're like that from the factory. My stock 2015 was running lean by up to 6% at certain rpms, causing knock. Sometimes MAFs get dirty, or airbox modifications make them read improperly. You could try cleaning it to see if it improves things.

Unfortunately, since your car doesn't have a factory wideband O2 sensor, don't know for sure how lean it's running. It's not a big deal though. Personally, I'd just richen it up a bit and pull a couple of degrees of timing in that rpm/load range and see if the knock goes away. The best way would be to get a wideband O2 or take it to a tuner.
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Old 08-13-2018, 06:41 PM   #8
John Connor
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2004 FXT 5 speed
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Thanks a bunch! I’ll make some changes and see if it helps. I picked up a new knock sensor too, so I’ll try that real quick before I flash the ECU. It might be nearly 15 years old anyway.
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Old 08-14-2018, 02:10 PM   #9
X49
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Quote:
Originally Posted by John Connor View Post
Also, I thought that stock boost for an 04 FXT was ~1BAR?
I'm not too familiar with your car, but it looks to me like you're hitting target boost based on the log. If you're at a high elevation or have high or low intake temperatures you'll have a lower target boost.

Be aware that if you're going to be changing the boost, you might need to make changes to ignition and fuel maps again since you'll be in a higher load range.
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Old 08-14-2018, 02:12 PM   #10
mr.nicknasty8
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That's not your knock sensor being faulty. You are stabbing the throttle at 2,000rpm. Lugging the car like that, will almost always cause knock. I'm guessing the timing is a little aggressive in that area or the car is running lean. Just because you can't audibly hear knock, doesn't mean there isn't any...

Edit: the car is also staying in closed loop when you are well into boost, the car is most likely running lean and that's why it's knocking.
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Old 08-17-2018, 01:38 PM   #11
John Connor
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Member#: 489892
Join Date: Aug 2018
Chapter/Region: NWIC
Location: Moscow, Idaho
Vehicle:
2004 FXT 5 speed
Silver

Default

Quote:
Originally Posted by X49 View Post
I'm not too familiar with your car, but it looks to me like you're hitting target boost based on the log. If you're at a high elevation or have high or low intake temperatures you'll have a lower target boost.

Be aware that if you're going to be changing the boost, you might need to make changes to ignition and fuel maps again since you'll be in a higher load range.
That makes sense, thanks!

Quote:
Originally Posted by mr.nicknasty8 View Post
That's not your knock sensor being faulty. You are stabbing the throttle at 2,000rpm. Lugging the car like that, will almost always cause knock. I'm guessing the timing is a little aggressive in that area or the car is running lean. Just because you can't audibly hear knock, doesn't mean there isn't any...

Edit: the car is also staying in closed loop when you are well into boost, the car is most likely running lean and that's why it's knocking.
Is all of that normal for a 100% stock car with a stock tune though? Stabbing the throttle at too low of an RPM I get, but why would those other problems exist with the above
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Old 08-22-2018, 02:09 PM   #12
mkv
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Default ecu help off subject

Off subject... I'm sorry about this off subject thing, maybe it touches the subject. I am going nuts with a no start situation. New ECU, new crank sensor, spark, fuel, compression and no start. I'm going nuts!

Any ideas?



Quote:
Originally Posted by John Connor View Post
I just did my first data log with RomRaider and I think my ecu thinks I'm experiencing knock. I've heard knock before and it isn't happening. I do have a good bit of experience with hondata and some light K20 tunning, but this is my first foray into Subaru's and boost.

I'm seeing a Knock correction advance of between 2 and 8 degrees that starts around 3,000rpms and goes till redline. It fades in and then tappers off towards the end of the pull. I'd upload the XML file, but I'm not sure how to do that here.

My car is also only hitting ~10psi when its cooler and ~8psi when it's warm out.

No mods
112,000 miles

If this is in the wrong sub-forum, I'm sorry. Thanks in advance for any help.
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