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Old 08-31-2020, 08:55 PM   #1
20BooSTIn15
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Default Feed back Knock

Just was cursing in my 2015 sti and noticed a couple of numbers on the access port on the feed back knock and fine knock learn. Feed back went up to -4.8 in 3rd gear at 3.8-4.5 k rpm and fine know learn was at -2.45 while dam was at 1.0. The car is not stock I have downpipe, aem fuel pump, intake, injectors 1050, fuel line, fuel rail lines, turbo inlet and itís tuned on Cobb stage 3 map. Iím just wondering if this is normal or should I be worried please help everyone? Thank you!
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Old 08-31-2020, 09:29 PM   #2
GK1707
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Originally Posted by 20BooSTIn15 View Post
Just was cursing in my 2015 sti and noticed a couple of numbers on the access port on the feed back knock and fine knock learn. Feed back went up to -4.8 in 3rd gear at 3.8-4.5 k rpm and fine know learn was at -2.45 while dam was at 1.0. The car is not stock I have downpipe, aem fuel pump, intake, injectors 1050, fuel line, fuel rail lines, turbo inlet and itís tuned on Cobb stage 3 map. Iím just wondering if this is normal or should I be worried please help everyone? Thank you!
Sounds about normal for a built motor, I have a similiar setup with a larger turbo and I get roughly the same amount of fine knock and feedback as well although everything functions as normal. Ignition system is all brand new as well and I'm pro tuned.
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Old 08-31-2020, 09:34 PM   #3
20BooSTIn15
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Originally Posted by GK1707 View Post
Sounds about normal for a built motor, I have a similiar setup with a larger turbo and I get roughly the same amount of fine knock and feedback as well although everything functions as normal. Ignition system is all brand new as well and I'm pro tuned.

Thank you for answering I wanna do a bigger turbo I was thinking fp green with a external waste gate and front mount. I wonder if I would be close to 400 whp and how reliable it would be?
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Old 09-01-2020, 09:19 AM   #4
BlackFighter
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I had a HTZ FP Green with built motor and all supporting mods pushing 420 whp on mustang dyno with a conservative tune. So getting up to 400 whp wont be a problem. Its all in the tune. I would recommend JR but there are others that are good too.
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Old 09-01-2020, 12:17 PM   #5
20BooSTIn15
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I had a HTZ FP Green with built motor and all supporting mods pushing 420 whp on mustang dyno with a conservative tune. So getting up to 400 whp wont be a problem. Its all in the tune. I would recommend JR but there are others that are good too.


So I would have to build the motor for it to be reliable or can the stock block handle 400 whp
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Old 09-01-2020, 01:51 PM   #6
BlackFighter
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Well taking in consideration that people are having stock piston ringland cracks at stock 300 hp ya at 400whp you will blow out those stock pistons. Please do your research before you waist your money. You need to take your time, read and research if you want to do it right. Are you on stock turbo?

And I said it before and say it again, don't forget about your brakes and suspension. If you can not stop or take a turn then all of that extra power is useless.

Last edited by BlackFighter; 09-01-2020 at 04:53 PM.
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Old 09-01-2020, 04:24 PM   #7
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Originally Posted by 20BooSTIn15 View Post
So I would have to build the motor for it to be reliable or can the stock block handle 400 whp
considering that's basically 50% over stock I'd say not really since you seem to want reliability too
I'm not sure any factory motor can be taken that far over stock and hold up

That would be fine if you are ok getting a flatbed home to rebuild every once in a while
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Old 09-01-2020, 04:55 PM   #8
BlackFighter
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I think you mean 25% over stock? You Philly people, haha J/K
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Old 09-01-2020, 05:49 PM   #9
GK1707
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Originally Posted by 20BooSTIn15 View Post
So I would have to build the motor for it to be reliable or can the stock block handle 400 whp

That is a question for whoever will be tuning your car. Your tuner will be able to make the best call for both driving conditions as well as their tuning ability.

Half the forums will tell you it's gonna blow up at 301whp. The other half will tell you about their buddy running 500whp on a stock unopened longblock. Ive seen both situations, your tuner will answer that question best.

However most tuners will favor a built block for the assurance of forged pistons.
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Old 09-02-2020, 01:25 AM   #10
alexmartynyuk
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Originally Posted by 20BooSTIn15 View Post
Just was cursing in my 2015 sti and noticed a couple of numbers on the access port on the feed back knock and fine knock learn. Feed back went up to -4.8 in 3rd gear at 3.8-4.5 k rpm and fine know learn was at -2.45 while dam was at 1.0. The car is not stock I have downpipe, aem fuel pump, intake, injectors 1050, fuel line, fuel rail lines, turbo inlet and itís tuned on Cobb stage 3 map. Iím just wondering if this is normal or should I be worried please help everyone? Thank you!
I would not listen to anyone telling you that the amount of feedback or fine learning you are seeing is normal. I have been tuning Subaruís and other platforms for years, various setups; stock block or built I have always been able to make sure there is no knock. And havenít had to use any spacers for the knock sensor due to a loose build that is noisy. Your tuner should be able to get the car dialed in and have IAM/DAM stay at 1 And keep feedback knock correction and fine learning knock correction at zero. I would not keep driving a car that sees that knock or any knock consistently because your are damaging internals. Stock blocks if taken care of from day one and have ran a tune that hasnít seen any knock can actually hold a good amount of power, there have been long blocks that have done over 600 at the wheels. But The problem is most people that have these cars put intakes and exhaust mods on the car and a manual boost controller with a stock tune or whatever tune was in it without having a clue how that affects the car, as a result these cars see a ton of detonation and eventually things let go. Anyway to the OP I wouldnít keep hitting boost because something will give eventually if it hasnít started to already, I would figure out why itís knocking, too much timing? Too lean? Too much boost?
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Old 09-02-2020, 06:47 AM   #11
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I think you mean 25% over stock? You Philly people, haha J/K
he said wheel hp of 400

it was my understanding the STI is nowhere near 300 whp stock, more like 260-275 ish

is that not true?
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Old 09-02-2020, 10:01 AM   #12
BlackFighter
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Clearly i was joking about he Philly thing since i am too from Philly. But ya your right more close to 252WHP on mustang dyno or so depending on the dyno. But still not 50%. Was clearly J/K and was trolling. Still 252 WHP to 400WHP is 37%. Stay strong my Philly dude

https://forums.nasioc.com/forums/sho....php?t=2696527
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Old 09-02-2020, 10:22 AM   #13
rtv900
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Originally Posted by BlackFighter View Post
Clearly i was joking about he Philly thing since i am too from Philly. But ya your right more close to 252WHP on mustang dyno or so depending on the dyno. But still not 50%. Was clearly J/K and was trolling. Still 252 WHP to 400WHP is 37%. Stay strong my Philly dude

https://forums.nasioc.com/forums/sho....php?t=2696527
yeah I know you were joking, I had no issue with that.

but I'm a math guy so I had to get technical. You are using the percentage on the wrong number.

252 is 37% LESS than 400.
400 is 60% MORE than 252
It's a percentage increase FROM the stock number, so that is the baseline.
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Old 09-22-2020, 04:22 PM   #14
mobysti
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Default

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Originally Posted by 20BooSTIn15 View Post
Just was cursing in my 2015 sti and noticed a couple of numbers on the access port on the feed back knock and fine knock learn. Feed back went up to -4.8 in 3rd gear at 3.8-4.5 k rpm and fine know learn was at -2.45 while dam was at 1.0. The car is not stock I have downpipe, aem fuel pump, intake, injectors 1050, fuel line, fuel rail lines, turbo inlet and itís tuned on Cobb stage 3 map. Iím just wondering if this is normal or should I be worried please help everyone? Thank you!
Seems normal for built car
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Old 10-22-2020, 09:47 AM   #15
Crispy 1
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Quote:
Originally Posted by alexmartynyuk View Post
I would not listen to anyone telling you that the amount of feedback or fine learning you are seeing is normal. I have been tuning Subaruís and other platforms for years, various setups; stock block or built I have always been able to make sure there is no knock. And havenít had to use any spacers for the knock sensor due to a loose build that is noisy. Your tuner should be able to get the car dialed in and have IAM/DAM stay at 1 And keep feedback knock correction and fine learning knock correction at zero. I would not keep driving a car that sees that knock or any knock consistently because your are damaging internals. Stock blocks if taken care of from day one and have ran a tune that hasnít seen any knock can actually hold a good amount of power, there have been long blocks that have done over 600 at the wheels. But The problem is most people that have these cars put intakes and exhaust mods on the car and a manual boost controller with a stock tune or whatever tune was in it without having a clue how that affects the car, as a result these cars see a ton of detonation and eventually things let go. Anyway to the OP I wouldnít keep hitting boost because something will give eventually if it hasnít started to already, I would figure out why itís knocking, too much timing? Too lean? Too much boost?
Agreed, it's hard for me to understand how someone would put parts on these cars or especially having/building a motor and not knowing these things!

These comments make it pretty clear even people that think they know what they're doing are oblivious to what their car is actually doing!
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Old 10-22-2020, 01:48 PM   #16
SaaielloWRX
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Originally Posted by 20BooSTIn15 View Post
Just was cursing in my 2015 sti and noticed a couple of numbers on the access port on the feed back knock and fine knock learn. Feed back went up to -4.8 in 3rd gear at 3.8-4.5 k rpm and fine know learn was at -2.45 while dam was at 1.0. The car is not stock I have downpipe, aem fuel pump, intake, injectors 1050, fuel line, fuel rail lines, turbo inlet and itís tuned on Cobb stage 3 map. Iím just wondering if this is normal or should I be worried please help everyone? Thank you!



Way too much knock I am fully built and rarely I will see a 1.4 feedback knock and its most likely false knock from road noise. That much knock is definitely a problem and will damage internals.
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