Welcome to the North American Subaru Impreza Owners Club Thursday March 28, 2024
Home Forums Images WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Go Back   NASIOC > NASIOC Technical > FA Series Factory 2.0L Turbo Powertrain

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.







* As an Amazon Associate I earn from qualifying purchases. 
* Registered users of the site do not see these ads. 
Reply
 
Thread Tools Display Modes
Old 05-03-2021, 02:48 PM   #1
Mr. REXified
Scooby Newbie
 
Member#: 109288
Join Date: Mar 2006
Chapter/Region: NWIC
Location: Kenmore, WA
Vehicle:
2018 Forester XT
White

Default 18’ Forester XT FBK

Not new to the forum or subarus but haven't posted in a looooong time. Yes my user name was created when I was in my early 20's. Not proud of it.

I currently have a 2018 Forester XT. Bought it new and have roughly 47k miles on it. Recently I changed my oil and air filter and decided to install my AP that I bought 6 months ago that's been waiting to be installed. I flashed the Stage 1 OTS maps and began monitoring my drives with the Anxiety Port. Started noticing some FBK as low as -5.92 during light throttle usually between -5 and 5 psi boost. Never registered any FBK during WOT. DAM almost always stays at 1. If I let off the throttle it goes away and the moment I give it more throttle it goes away. Also this doesn't seem to happen until the engine is warmed up. Since I was at 46k I decided to take the 3-4 hrs to change my spark plugs and walnut blasting my intake valves to see if it would help. No difference that I can notice. From what I've been reading the FA20 is pretty sensitive to knock and FBK during low throttle in the -5 the 5 psi vacuum/boost range is normal, but how much FBK is acceptable? Is this as a result of the EGR? Vacuum leak? Boost leak? I do notice my AFR is 14-15. Does that seem high? I've attached data logs if anyone would like to take a look. I have a smoke test machine that should be here to day and a boost leak tester that should be here by the end of the week. If anyone has any insight it would be greatly appreciated.

I also know Cobb OTS maps aren't the greatest which is why I plan on getting tuned later this month once I install my other supporting mods that have been sitting in my garage. Just want to rule out any issues so I don't run into problems during the tune. Mods that are pending installation and tune are TGV/EGR deletes, Perrin charge pipe, Grimmspeed EBCS, GS drop in filter and AVO Intercooler. Looking at either Ambot or making the drive down to Surgeline from the Seattle area.

Datalog

https://docs.google.com/spreadsheets...jE12Bs8WY/edit

For reference here a list of mods and work I've done that could pertain to this issue

Current Mods
-SPT Catback
-V3 AP Stage 1

Recent Maintenance Work
-Oil change 500 miles
-OEM Air filter 500 miles
-OEM NKG Spark Plugs 200 miles
-Walnut blasting 200 miles

Thanks in advance for any help or feedback
* Registered users of the site do not see these ads.

Last edited by Mr. REXified; 05-03-2021 at 07:06 PM.
Mr. REXified is offline   Reply With Quote
Sponsored Links
* Registered users of the site do not see these ads.
Old 05-03-2021, 04:46 PM   #2
tegxsi
Scooby Newbie
 
Member#: 446029
Join Date: May 2016
Location: 510
Default

If FBK occurs at low load and not WOT then it's generally not super concerning. Your FBK is high and occurs frequently. I've never logged KS noise but I've never had this issue. I do see random noise spikes between cylinders 1,2,3 but 4 is clean.

I don't really see anything that really stands out in the log. AFR is fine. I would check the engine bay for rattles. Check for rocks or foreign objects. The bottom turbo shield is a good place to check.

If you have access to E85, I would throw in 2-3 gallons to see if there is any improvement. It's one way to check for false knock.
tegxsi is offline   Reply With Quote
Old 05-03-2021, 05:18 PM   #3
Mr. REXified
Scooby Newbie
 
Member#: 109288
Join Date: Mar 2006
Chapter/Region: NWIC
Location: Kenmore, WA
Vehicle:
2018 Forester XT
White

Default

Quote:
Originally Posted by tegxsi View Post
If FBK occurs at low load and not WOT then it's generally not super concerning. Your FBK is high and occurs frequently. I've never logged KS noise but I've never had this issue. I do see random noise spikes between cylinders 1,2,3 but 4 is clean.

I don't really see anything that really stands out in the log. AFR is fine. I would check the engine bay for rattles. Check for rocks or foreign objects. The bottom turbo shield is a good place to check.

If you have access to E85, I would throw in 2-3 gallons to see if there is any improvement. It's one way to check for false knock.
I did did remove the OEM factory skid plate/heat shield about a week ago. It got damaged a while back during a snow off roading excursion and thought that might be contributing to my problem. Is there another heat shield on the turbo? I've also added a 15 oz bottle of Lucas Octane booster and that didn't make a difference. The Lucas octane booster is supposed to raise about 30 points or 3 Octane. Is e85 going to be better than that to rule out false knock?
Mr. REXified is offline   Reply With Quote
Old 05-03-2021, 10:39 PM   #4
Mr. REXified
Scooby Newbie
 
Member#: 109288
Join Date: Mar 2006
Chapter/Region: NWIC
Location: Kenmore, WA
Vehicle:
2018 Forester XT
White

Default

Found a Chevron station 15 min from me that sells E85. Gonna stop by after work and throw in 3 gallons then top off with 92 and I'll report back.
Anyone else have any insight?

Last edited by Mr. REXified; 05-03-2021 at 10:40 PM. Reason: Adding
Mr. REXified is offline   Reply With Quote
Old 05-04-2021, 01:23 AM   #5
tegxsi
Scooby Newbie
 
Member#: 446029
Join Date: May 2016
Location: 510
Default

Quote:
Originally Posted by Mr. REXified View Post
I did did remove the OEM factory skid plate/heat shield about a week ago. It got damaged a while back during a snow off roading excursion and thought that might be contributing to my problem. Is there another heat shield on the turbo? I've also added a 15 oz bottle of Lucas Octane booster and that didn't make a difference. The Lucas octane booster is supposed to raise about 30 points or 3 Octane. Is e85 going to be better than that to rule out false knock?
Yes, skid plate... I see it as a shield since it protects the low mount turbo lol.
Ethanol is a great octane booster... How did your spark plugs look when they were removed? Does it knock if you rev in park? Maybe you can have have someone lightly rev the engine while you listen around the engine bay for anything out of the ordinary.
tegxsi is offline   Reply With Quote
Old 05-04-2021, 02:24 PM   #6
Mr. REXified
Scooby Newbie
 
Member#: 109288
Join Date: Mar 2006
Chapter/Region: NWIC
Location: Kenmore, WA
Vehicle:
2018 Forester XT
White

Default

Quote:
Originally Posted by tegxsi View Post
Yes, skid plate... I see it as a shield since it protects the low mount turbo lol.
Ethanol is a great octane booster... How did your spark plugs look when they were removed? Does it knock if you rev in park? Maybe you can have have someone lightly rev the engine while you listen around the engine bay for anything out of the ordinary.
Plugs looked fine when I changed them. Not a lot of carbon build up and doesn't look like the engine was running lean. No knock when revving either.

So I put in almost 4 gal of E85 and topped off with 92 last night. Still showed a -2.81 on my short drive to work. When I was driving into work i heard a buzzing from the back. I pulled over and looked under the car and saw 2 cracks in the y-pipe of my Catback and one of the 2 cracks is fully separated all the way around. The cracks are at the flange that connects my right muffler. I have a feeling this could be contributing to my FBK. The crack is right behind my rear sway bar but I'm sure there's enough resonance to make it back to the knock sensor. I'm gonna swap my stock catback on tonight and see what happens.
Mr. REXified is offline   Reply With Quote
Old 05-04-2021, 05:54 PM   #7
tegxsi
Scooby Newbie
 
Member#: 446029
Join Date: May 2016
Location: 510
Default

Quote:
Originally Posted by Mr. REXified View Post
Plugs looked fine when I changed them. Not a lot of carbon build up and doesn't look like the engine was running lean. No knock when revving either.

So I put in almost 4 gal of E85 and topped off with 92 last night. Still showed a -2.81 on my short drive to work. When I was driving into work i heard a buzzing from the back. I pulled over and looked under the car and saw 2 cracks in the y-pipe of my Catback and one of the 2 cracks is fully separated all the way around. The cracks are at the flange that connects my right muffler. I have a feeling this could be contributing to my FBK. The crack is right behind my rear sway bar but I'm sure there's enough resonance to make it back to the knock sensor. I'm gonna swap my stock catback on tonight and see what happens.
Don't put in too much E85. About E20-25 blend should do the trick.
That would be interesting it's the cause of FBK.
tegxsi is offline   Reply With Quote
Old 05-10-2021, 09:43 AM   #8
dpetro1
Scooby Newbie
 
Member#: 487500
Join Date: Jun 2018
Location: Catonsville, MD
Vehicle:
2018 WRX

Default

Pretty sure this is just a case of the ots map. You could try the stage 0 map or just wait until you get a proper tune.
I wouldn't go down a rabbit hole of chasing a problem that is probably non existent.
dpetro1 is offline   Reply With Quote
Reply

Thread Tools
Display Modes

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
Forum Jump

All times are GMT -4. The time now is 08:40 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2024 Axivo Inc.
Copyright ©1999 - 2019, North American Subaru Impreza Owners Club, Inc.

As an Amazon Associate I earn from qualifying purchases.

When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission
Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.