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Old 11-29-2022, 04:34 AM   #1
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Angry Turbo BRZ Backfiring Under Boost

Hi,

I have been trouble shooting my car for about 3 months now with a tuner and a dedicated performance shop but am having problems that seem to be puzzling everyone.

For background I have a 2016 Subaru BRZ with the Fullblown turbo kit.

Garret 2871R
Intercooler
Oil Cooler
NGK Spark Plugs 0.028" Gap
550C Injectors
AEM 340LPH Pump
Aftermarket Downpipe & Exhaust
Stock Front Pipe with Cat Delete
No Boost Controller (Waiting to fix problem before installing ECBS)
Tial 11 PSI BOV
Tial 7 PSI WG (It was 14 PSI, I will get to that)

I Installed the kit around June and was having no problems. Then about 2-3 months ago I started getting poor performance (hesitation) and backfire while accelerating under boost. This led me to change the spark plugs to the ones mentioned above and changed the MAF sensor with a new one which fixed the hesitation. But now I am left with the car backfiring and misfiring I am assuming because the car will lose power at max boost (14 PSI at the time)

I actually was curious about my WG because I noticed I was hitting 1.83BAR when the car was first installed but was ensured by fullblown that they put a 7PSI spring. Well I pulled the WG to check and come to find out I had a 14 PSI spring the entire time. I changed it to a 7PSi spring which for now solves the problem but I am basically nerfing the car for it to not blow up. I believe I will run into issues when I meet with my tuner for a 8,10,and 12 psi map.

Looking at the logs it looks like I am running lean towards the higher RPM range but it goes back to being normal once I hit a certain RPM which is strange. The log from 11 June shows when the car was running rich (I had a boost leak at the time). The log from Nov 18 is a Revision to the tune that Fullblown gave me back in june to try to fix the new lean issue problem to no avail. With the 14 PSI spring still installed, I will get backfiring and loss of power around 4000RPM which is close to full boost and is running lean. The new log from Nov 27 is after I put the 7PSI WG spring in shows that the car isn't having problems but is running lean.

I had the shop check for vacuum leaks and exhaust leaks and they discovered a few leaks at my piping and blow off valve and fixed them. At this point I am pretty much stumped as to why the car is backfiring and loosing power once I reach a high boost level. I removed and installed the fuel pump multiple times and put an entirely new housing assembly as well. The fuel injectors were removed and there were no visible clogs or damage and the o-rings are still in pristine condition. No fuel is leaking from the port injectors.

It is just strange because even with a 14PSI spring, the car was not running lean and was actually running rich in june but has now became lean.

Last edited by kobet7; 11-29-2022 at 04:59 AM.
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Old 11-29-2022, 09:30 AM   #2
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Waiting to install the EBCS is not a good idea.
I'm assuming this turbo is externally gated because you mentioned a spring - check your wastegate lines, this behavior sounds like you've damaged one of them. Even a sliver cut into one can cause over boost. How are you monitoring boost?

Absolutely find a tuner who can manage these issues. Do not drive the car under these conditions. Between running lean and over boosting before, it's a miracle your engine hasn't started to pretzel the rods.

Can you post these logs for us to see?
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Old 11-29-2022, 02:44 PM   #3
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Quote:
Originally Posted by DarkPira7e View Post
Waiting to install the EBCS is not a good idea.
I'm assuming this turbo is externally gated because you mentioned a spring - check your wastegate lines, this behavior sounds like you've damaged one of them. Even a sliver cut into one can cause over boost. How are you monitoring boost?

Absolutely find a tuner who can manage these issues. Do not drive the car under these conditions. Between running lean and over boosting before, it's a miracle your engine hasn't started to pretzel the rods.

Can you post these logs for us to see?
Hi, thanks for your feedback, I attached the logs when making the post, but I guess it does not attach bin files. See this link, https://drive.google.com/drive/folde...zW?usp=sharing.

I will get the new logs with the 7PSI spring in there later today. For now, I have the logs from when the car was driving good in June to when it was misfireing/backfiring on the 18th with the 14PSI spring still installed. Right now, I am monitoring boost with my MAP sensor logged values. I believe the backfiring/backfiring is from the car running lean, but I have gone down the list of possibly causes for it to be lean to no avail.

At the moment I am running 7PSI straight from the compressor to the WG to prevent the combination of being lean AND at 14PSi of boost. Being lean at 7PSI seems to be alright for the time being.
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Old 11-30-2022, 09:51 AM   #4
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I would stop doing pulls on the car until you speak to a tuner
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Old 11-30-2022, 10:35 AM   #5
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Quote:
Originally Posted by kobet7 View Post
Hi, thanks for your feedback, I attached the logs when making the post, but I guess it does not attach bin files. See this link, https://drive.google.com/drive/folde...zW?usp=sharing.

I will get the new logs with the 7PSI spring in there later today. For now, I have the logs from when the car was driving good in June to when it was misfireing/backfiring on the 18th with the 14PSI spring still installed. Right now, I am monitoring boost with my MAP sensor logged values. I believe the backfiring/backfiring is from the car running lean, but I have gone down the list of possibly causes for it to be lean to no avail.

At the moment I am running 7PSI straight from the compressor to the WG to prevent the combination of being lean AND at 14PSi of boost. Being lean at 7PSI seems to be alright for the time being.

Being lean at any point outside of low load cruising is not acceptable. You need to get this whole setup retuned and evaluated by a tuner in person who can correctly troubleshoot the hardware and software components.

I am not a tuner and cannot fix this, I don't want to misrepresent my purpose here; I just want to help save you from yourself. Don't drive the car until you have this thoroughly evaluated by a competent tuner in person
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Old 11-30-2022, 02:49 PM   #6
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Who tuned this car originally? What is it tuned with, ecutek?

Need logs of current setup, upload them to datazap.me and post the link.

What is "lean" and "rich" to you? "Lean" is not ok even for 7 psi on a high compression motor like the FA20.
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Old 11-30-2022, 07:06 PM   #7
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Originally Posted by terboboost View Post
Who tuned this car originally? What is it tuned with, ecutek?

Need logs of current setup, upload them to datazap.me and post the link.

What is "lean" and "rich" to you? "Lean" is not ok even for 7 psi on a high compression motor like the FA20.
The car had a tune from Fullblown. I sent them my logs while the car was lean, and they sent me a Rev 1 to my tune and basically told me the 14 PSI spring was put there by me and that there was no way they gave me a WG with a 14 PSI spring.

I am defining lean as anything higher than the target AFR. Even now I hit low-mid 13s AFRs when the car is targeting 11 while accelerating. I am meeting with my tuner again soon to see if it is the tune.
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Old 11-30-2022, 07:08 PM   #8
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Quote:
Originally Posted by alphasaur View Post
I would stop doing pulls on the car until you speak to a tuner
Currently in touch with one. He thinks it has something to do with my fueling system, but we checked the pump, pump housing, and injectors and nothing looks out of the ordinary.
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Old 11-30-2022, 07:18 PM   #9
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Who is your tuner?

Find someone that is familiar with THIS platform and boost. Money spent on a good tuner and dyno time is the best money you will ever spend.
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Old 12-02-2022, 07:51 AM   #10
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Check the DI computer has all three bolts in and tight as well at it's mounting bracket

Load your logs to www.datazap.me and post links here
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Old 12-03-2022, 03:04 AM   #11
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Quote:
Originally Posted by kobet7 View Post
I Installed the kit around June and was having no problems. Then about 2-3 months ago I started getting poor performance (hesitation) and backfire while accelerating under boost. This led me to change the spark plugs to the ones mentioned above and changed the MAF sensor with a new one which fixed the hesitation. But now I am left with the car backfiring and misfiring I am assuming because the car will lose power at max boost (14 PSI at the time)
Why did you change the spark plugs and MAF? Just rolling the dice in hopes that this would fix the issue? What was the condition of the spark plug terminals? Was there any damage, discoloration, deposits, etc? The question is what changed? It was running fine with the 14psi spring, which, unless you are on E85, is too much boost for the stock block on pump gas and an E-tune. What is your duty cycle on your injectors? You say you were running rich at this boost, but how rich is rich to you because if you are on pump gas, you would need to run pretty rich with pretty poor timing to avoid knock at 14psi.

So the car had hesitation and misfiring and backfiring while accelerating on boost? Did you log these events at all? Are you sure you were actually accelerating? Is it possible your foot was on the pedal, but the failsafes closed the throttle body or cut ignition because of a bad condition, and then you had a backfire? It seems to me like a backfire under WOT boost would be impossible without ignition failure from a bad coil or something, or from a bad injector harness that temporarily lost power. I feel like if it was a fuel pump o-ring seal issue then the problem wouldn't be intermittent. Not using enough o-rings or having it fall apart to the bottom of the basket tends to just make the car unable to run.

Quote:
Originally Posted by kobet7 View Post
I actually was curious about my WG because I noticed I was hitting 1.83BAR when the car was first installed but was ensured by fullblown that they put a 7PSI spring. Well I pulled the WG to check and come to find out I had a 14 PSI spring the entire time. I changed it to a 7PSi spring which for now solves the problem but I am basically nerfing the car for it to not blow up. I believe I will run into issues when I meet with my tuner for a 8,10,and 12 psi map.
You say 1.83 bar; that is absolute bar, right? If so, that is 12 psi (0.83 bar over atmospheric). That seems reasonable if you believed the spring was roughly 14 psi.

Quote:
Originally Posted by kobet7 View Post
Looking at the logs it looks like I am running lean towards the higher RPM range but it goes back to being normal once I hit a certain RPM which is strange. The log from 11 June shows when the car was running rich (I had a boost leak at the time). The log from Nov 18 is a Revision to the tune that Fullblown gave me back in june to try to fix the new lean issue problem to no avail. With the 14 PSI spring still installed, I will get backfiring and loss of power around 4000RPM which is close to full boost and is running lean. The new log from Nov 27 is after I put the 7PSI WG spring in shows that the car isn't having problems but is running lean.
Do you have these logs? How lean? How rich?

Quote:
Originally Posted by kobet7 View Post
I had the shop check for vacuum leaks and exhaust leaks and they discovered a few leaks at my piping and blow off valve and fixed them. At this point I am pretty much stumped as to why the car is backfiring and loosing power once I reach a high boost level. I removed and installed the fuel pump multiple times and put an entirely new housing assembly as well. The fuel injectors were removed and there were no visible clogs or damage and the o-rings are still in pristine condition. No fuel is leaking from the port injectors.

It is just strange because even with a 14PSI spring, the car was not running lean and was actually running rich in june but has now became lean.
Do you have antilag?
What is your timing set at?
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Old 12-08-2022, 02:39 PM   #12
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Originally Posted by Irace86.2.0 View Post
Why did you change the spark plugs and MAF? Just rolling the dice in hopes that this would fix the issue? What was the condition of the spark plug terminals? Was there any damage, discoloration, deposits, etc? The question is what changed? It was running fine with the 14psi spring, which, unless you are on E85, is too much boost for the stock block on pump gas and an E-tune. What is your duty cycle on your injectors? You say you were running rich at this boost, but how rich is rich to you because if you are on pump gas, you would need to run pretty rich with pretty poor timing to avoid knock at 14psi.

So the car had hesitation and misfiring and backfiring while accelerating on boost? Did you log these events at all? Are you sure you were actually accelerating? Is it possible your foot was on the pedal, but the failsafes closed the throttle body or cut ignition because of a bad condition, and then you had a backfire? It seems to me like a backfire under WOT boost would be impossible without ignition failure from a bad coil or something, or from a bad injector harness that temporarily lost power. I feel like if it was a fuel pump o-ring seal issue then the problem wouldn't be intermittent. Not using enough o-rings or having it fall apart to the bottom of the basket tends to just make the car unable to run.



You say 1.83 bar; that is absolute bar, right? If so, that is 12 psi (0.83 bar over atmospheric). That seems reasonable if you believed the spring was roughly 14 psi.



Do you have these logs? How lean? How rich?



Do you have antilag?
What is your timing set at?
Hi, Here are the logs.
Initial logs post turbo install (RICH): https://datazap.me/u/kobet7/2016-sub...tion-turbo-kit

Fullblown Rev 1 Tune after informing them of my issues (LEAN): https://datazap.me/u/kobet7/fullblown-rev-1-tune

I changed spark plugs and MAF sensor in an effort to cure the hesitation which I also thought was tied to the backfiring under boost. The MAF sensor change actually really helped the hesitation and it is basically gone, but the backfiring did not disappear. I had a shop change the spark plugs and they did not note and damage on the coils. The spark plugs that they returned to me were pretty black which indicated the rich condition which probably went on for months.

I do not believe it is the pump because we opened the basket with my tuner present, and the pump was still where it should be, and it currently has two O-rings.

It is definitely a possibility that the car cuts the throttle, but I would think the car would have rich readings following the loss of power which it doesn't. I can only assume the car gets too lean and the fuel doesn't completely burn which makes the popping. When I say "loss of power" it's not like the car starts decelerating, it's more like the car stops accelerating at the rate it was at and accelerates much slower, but you can definitely feel some sort of light wall it feels like its hitting.

I have now changed the WG spring to 7 PSI and the car does not backfire but that is likely because its running at a lower boost while being lean.
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Old 12-08-2022, 02:58 PM   #13
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Doubt it.
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Old 12-08-2022, 09:32 PM   #14
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Quote:
Originally Posted by kobet7 View Post
Hi, Here are the logs.
Initial logs post turbo install (RICH): https://datazap.me/u/kobet7/2016-sub...tion-turbo-kit

Fullblown Rev 1 Tune after informing them of my issues (LEAN): https://datazap.me/u/kobet7/fullblown-rev-1-tune

I changed spark plugs and MAF sensor in an effort to cure the hesitation which I also thought was tied to the backfiring under boost. The MAF sensor change actually really helped the hesitation and it is basically gone, but the backfiring did not disappear. I had a shop change the spark plugs and they did not note and damage on the coils. The spark plugs that they returned to me were pretty black which indicated the rich condition which probably went on for months.

I do not believe it is the pump because we opened the basket with my tuner present, and the pump was still where it should be, and it currently has two O-rings.

It is definitely a possibility that the car cuts the throttle, but I would think the car would have rich readings following the loss of power which it doesn't. I can only assume the car gets too lean and the fuel doesn't completely burn which makes the popping. When I say "loss of power" it's not like the car starts decelerating, it's more like the car stops accelerating at the rate it was at and accelerates much slower, but you can definitely feel some sort of light wall it feels like its hitting.

I have now changed the WG spring to 7 PSI and the car does not backfire but that is likely because its running at a lower boost while being lean.
I don't see hesitation on the first one. Looks like boost builds and hits wastegate pressure at 12psi. MAF reading fluctuates a little once the wastegate opens, but MAP reading seems stable. The only odd thing that jumps out to me, as a novice looking at these things, is that your Actual AFR looks constant and your Target AFR fluctuates, and that is odd to me because usually it is the other way around. Usually the Actual AFR is fluctuating and the Target AFR is more constant.

https://datazap.me/u/kobet7/2016-sub...zoom=6541-6878
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