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Discussion Starter · #1 ·
Hello,
I am new to the Subie world and just got a 2020 STI. I recently bought an accessport and threw on the Stage 0 tune just so I can log the car, since it is new to me. I ended up getting really bad FNL readings (~ -4) and slight FBK feedback knock readings. A friend suggested that since the Stage 0 does not have a ACN tune that it is pulling timing due to bad gas.

Realizing that CA gas really sucks I'm thinking of running E85 on the car. The only thing is that I don't really want to mod anything else on the car. Is this possible with no modified intake, downpipe, or headers?
 

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You don't need to have anything else modded. You will need to have the car tuned properly to be able to run ethanol. I'm not sure if you're going to be able to do that currently. Cobb pulled support for their flex fuel set up as it interferes with factory emissions components to work. They are currently working on an updated kit which will comply with emissions regulations though.

You could always get your car professionally tuned as it is. Getting a legit tune is almost always better than one of the off the shelf generic tunes.
 

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If you have the flex-fuel kit. You can run e85 after installation and tune. But COBB no longer supports flex-fuel because of their green initiative or whatever. You don't need any other parts besides your flex-fuel kit. Adding other parts is to capitalize on gains and gain more power.

In my opinion, choosing to run e85 for this sole purpose is a waste of money, time, and is quite idiotic. 91 Pump gas is fine. If you're getting such bad readings, it aint the gas.
 

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Stage 1 ACN does not require any mods to be run on the car.
It just raises the boost a bit, with safer timing than stock.

I ran the Stage 1 ACN tune on an otherwise stock car for a couple years before I started bolting parts on and getting a protune done.

The Stage 1 + SF is the tune intended for the intake, but there is also just the plain stage 1 with no parts required.
 

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Discussion Starter · #5 ·
If you have the flex-fuel kit. You can run e85 after installation and tune. But COBB no longer supports flex-fuel because of their green initiative or whatever. You don't need any other parts besides your flex-fuel kit. Adding other parts is to capitalize on gains and gain more power.

In my opinion, choosing to run e85 for this sole purpose is a waste of money, time, and is quite idiotic. 91 Pump gas is fine. If you're getting such bad readings, it aint the gas.
I did want to add a little bit more power and run it safely. I was told that E85 is the best way to do that and plus I've never had a car run on corn so I'd finally be able to say that I've had a car running on E85. It's not that I doubt 91 but I have read some things stating that trying to modify on it can possibly hurt the motor, made me weary to say the least.

Any ideas on how I can check for issues with the readings I had? Or is going to a tuner my only shot?
 

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Discussion Starter · #6 ·
Stage 1 ACN does not require any mods to be run on the car.
It just raises the boost a bit, with safer timing than stock.

I ran the Stage 1 ACN tune on an otherwise stock car for a couple years before I started bolting parts on and getting a protune done.

The Stage 1 + SF is the tune intended for the intake, but there is also just the plain stage 1 with no parts required.
The car came with a shitty muffler delete do you think that the Stage 1 ACN tune would be alright for me to run?
 

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Alot of this has been covered already but ill add to it. In order to properly run E85, you should upgrade the injectors and fuel pump. If you plan on doing both E85 and pump fuel then you will need a flex fuel kit as welll. You will also need a professional tune on the car for E85. With Cobb no longer supporting flex fuel, protuning flex fuel on Cobb software isnt going to be possible at this time. You will have to find other means of tuning for E85 unless you want to be constantly switching maps based on your checked quality of ethanol everytime you fill up. Im sure you can see how troublesome that will be every single time.

With that said, yes E85 does offer a bit more safety when compared to pump 91 and 93 octane fuel. However, one thing that is often overlooked is that with E85, you need to use around 30% more of it give or take to get the same kind of energy output as gasoline. Yes, you can definitely get more power out of the car with E85 but you will also be using alot more fuel. Thus why you need larger fuel injectors and fuel pump when using E85. Using more fuel will mean more frequent trips to the pump. Im sure you get where this is going.

Personally, if you're going to keep the car stockish and just using flex fuel to get a little power out of it....it isnt worth it in my opinion. I think these cars really shine on E85 when you are pretty much at the point of full bolt ons and or upgraded turbo. I think in your case, you should just get the car protuned on your 91octane. It will be alot better than the Cobb OTS maps.

BTW, if you're getting high FKL readings and some FBK, it ain't the gas lol. I would figure out why this is happening before modding the car. Muffler deletes has nothing to do with it either.
 

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The car came with a shitty muffler delete do you think that the Stage 1 ACN tune would be alright for me to run?
Yes, on these cars a catback has little to no effect on anything.
It's the downpipe that effects the tune.

You can run a stage 1 ACN tune with or without an exhaust no problem.

As mentioned above, even if you don't plan to change anything else, a 'pro tune' on the dyno is still the safest option.
The Stage 1 ACN will be safer than any other tune available to you right now on the Accessport, but a protune will still be the safest.

If you are running California 91, I'd expect you'll still get some knock, even on a Stage 1 ACN, you'll just get far less than a 'Stage 0' (which is realistically programmed for 93 octane).
 

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I did want to add a little bit more power and run it safely. I was told that E85 is the best way to do that and plus I've never had a car run on corn so I'd finally be able to say that I've had a car running on E85. It's not that I doubt 91 but I have read some things stating that trying to modify on it can possibly hurt the motor, made me weary to say the least.

Any ideas on how I can check for issues with the readings I had? Or is going to a tuner my only shot?
Modifying your car when you have underlying problems will cause issues. Dont get me wrong, e85 is great. But as a first mod, it is quite unusual and not quite practical.

As with any car problems, its about troubleshooting, testing, and trying to pinpoint the area of trouble.

I am not even sure what you mean by "FNL". Do you mean fine knock learn which is FKL or feedback knock which is FBK? If it is FKL then your car is operating perfectly fine. It is learning and adjusting correctly. And it could be a multitude of things. Did it spike once to your -4 reading or consistently holding there? Maybe your AC surged, maybe a rock made a sound. So many things and none of which is worrisome or warrants what you want to modify with your car.
 

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Alot of this has been covered already but ill add to it. In order to properly run E85, you should upgrade the injectors and fuel pump. If you plan on doing both E85 and pump fuel then you will need a flex fuel kit as welll. You will also need a professional tune on the car for E85. With Cobb no longer supporting flex fuel, protuning flex fuel on Cobb software isnt going to be possible at this time. You will have to find other means of tuning for E85 unless you want to be constantly switching maps based on your checked quality of ethanol everytime you fill up. Im sure you can see how troublesome that will be every single time.

With that said, yes E85 does offer a bit more safety when compared to pump 91 and 93 octane fuel. However, one thing that is often overlooked is that with E85, you need to use around 30% more of it give or take to get the same kind of energy output as gasoline. Yes, you can definitely get more power out of the car with E85 but you will also be using alot more fuel. Thus why you need larger fuel injectors and fuel pump when using E85. Using more fuel will mean more frequent trips to the pump. Im sure you get where this is going.

Personally, if you're going to keep the car stockish and just using flex fuel to get a little power out of it....it isnt worth it in my opinion. I think these cars really shine on E85 when you are pretty much at the point of full bolt ons and or upgraded turbo. I think in your case, you should just get the car protuned on your 91octane. It will be alot better than the Cobb OTS maps.

BTW, if you're getting high FKL readings and some FBK, it ain't the gas lol. I would figure out why this is happening before modding the car. Muffler deletes has nothing to do with it either.
not quite, you can tune the car through cobb on e85 just fine, provided you keep ALL emissions related items and only run e85 100% of the time, NOT flex fuel. that said, i do agree that if that's all he's doing to the car, he doesnt really need e85,

OP, a quality protune will probably be able to net 20ish whp (dyno pending) and increase reliability assuming its a quality tune. but i also agree to what jay said about it not being the gas. a catback or muffler delete will not require any sort of tune.
 

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not quite, you can tune the car through cobb on e85 just fine, provided you keep ALL emissions related items and only run e85 100% of the time, NOT flex fuel. that said, i do agree that if that's all he's doing to the car, he doesnt really need e85,

OP, a quality protune will probably be able to net 20ish whp (dyno pending) and increase reliability assuming its a quality tune. but i also agree to what jay said about it not being the gas. a catback or muffler delete will not require any sort of tune.
Sometimes I dont word things correctly but you got the gist :)
 

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Discussion Starter · #12 ·
Alot of this has been covered already but ill add to it. In order to properly run E85, you should upgrade the injectors and fuel pump. If you plan on doing both E85 and pump fuel then you will need a flex fuel kit as welll. You will also need a professional tune on the car for E85. With Cobb no longer supporting flex fuel, protuning flex fuel on Cobb software isnt going to be possible at this time. You will have to find other means of tuning for E85 unless you want to be constantly switching maps based on your checked quality of ethanol everytime you fill up. Im sure you can see how troublesome that will be every single time.

With that said, yes E85 does offer a bit more safety when compared to pump 91 and 93 octane fuel. However, one thing that is often overlooked is that with E85, you need to use around 30% more of it give or take to get the same kind of energy output as gasoline. Yes, you can definitely get more power out of the car with E85 but you will also be using alot more fuel. Thus why you need larger fuel injectors and fuel pump when using E85. Using more fuel will mean more frequent trips to the pump. Im sure you get where this is going.

Personally, if you're going to keep the car stockish and just using flex fuel to get a little power out of it....it isnt worth it in my opinion. I think these cars really shine on E85 when you are pretty much at the point of full bolt ons and or upgraded turbo. I think in your case, you should just get the car protuned on your 91octane. It will be alot better than the Cobb OTS maps.

BTW, if you're getting high FKL readings and some FBK, it ain't the gas lol. I would figure out why this is happening before modding the car. Muffler deletes has nothing to do with it either.
Thank you. This post helped out a ton!
 

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Discussion Starter · #13 ·
Modifying your car when you have underlying problems will cause issues. Dont get me wrong, e85 is great. But as a first mod, it is quite unusual and not quite practical.

As with any car problems, its about troubleshooting, testing, and trying to pinpoint the area of trouble.

I am not even sure what you mean by "FNL". Do you mean fine knock learn which is FKL or feedback knock which is FBK? If it is FKL then your car is operating perfectly fine. It is learning and adjusting correctly. And it could be a multitude of things. Did it spike once to your -4 reading or consistently holding there? Maybe your AC surged, maybe a rock made a sound. So many things and none of which is worrisome or warrants what you want to modify with your car.
Wow yes I am an idiot I meant FKL....

And yea i would get a semi consistent rise on open throttle and WOT. Any IE recommendations for getting this issue checked out?
 

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Discussion Starter · #14 ·
not quite, you can tune the car through cobb on e85 just fine, provided you keep ALL emissions related items and only run e85 100% of the time, NOT flex fuel. that said, i do agree that if that's all he's doing to the car, he doesnt really need e85,

OP, a quality protune will probably be able to net 20ish whp (dyno pending) and increase reliability assuming its a quality tune. but i also agree to what jay said about it not being the gas. a catback or muffler delete will not require any sort of tune.
Thanks! Going to try to find a place that can check my previous issues. Im new to subies and I see a lot of different views on which things work and what doesn't. If I wanted to go the modded route what would you recommend for safe reliable power (pro-tune being an option). Or is stock my best bet for reliability with some preventive mods (AOS, Cyl4 Cooling, Radiator)
 

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Thanks! Going to try to find a place that can check my previous issues. Im new to subies and I see a lot of different views on which things work and what doesn't. If I wanted to go the modded route what would you recommend for safe reliable power (pro-tune being an option). Or is stock my best bet for reliability with some preventive mods (AOS, Cyl4 Cooling, Radiator)
you can make safe, reliable power at almost any power level, it will depend on your goals for the car, aka how much power you want to make, if you are racing it or not, and what your budget is. to make suggestions i'd need to know what your goals are overall.

the safety mods aka AOS, CYL4 Cooling, Radiatior, killer b oil pickup+baffle i'd do regardless of power goals. the oem radiator is actually not bad, pending the power levels and if you are or are not racing. an AOS and the oil pickup+baffle are a must imo,
 

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Discussion Starter · #16 ·
you can make safe, reliable power at almost any power level, it will depend on your goals for the car, aka how much power you want to make, if you are racing it or not, and what your budget is. to make suggestions i'd need to know what your goals are overall.

the safety mods aka AOS, CYL4 Cooling, Radiatior, killer b oil pickup+baffle i'd do regardless of power goals. the oem radiator is actually not bad, pending the power levels and if you are or are not racing. an AOS and the oil pickup+baffle are a must imo,
Racing is a negative, I got a ticket going 114 and got lucky for not getting anything but a fine so I'm staying clear from that. I honestly just want a fun canyon car. Not sure how subaru mods affect power increase but ~30-40 would be a goal. That being said I am ignorant to this stuff so not sure if that contradicts my previous statements.
 

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Racing is a negative, I got a ticket going 114 and got lucky for not getting anything but a fine so I'm staying clear from that. I honestly just want a fun canyon car. Not sure how subaru mods affect power increase but ~30-40 would be a goal. That being said I am ignorant to this stuff so not sure if that contradicts my previous statements.
So AOS, Cyl4 mod, pickup/baffle should be done first for reliability sake.

Unfortunately on a 2020, even with a protune, looks like downpipe isn't really a straightforward option.
Some people have done it and are able to fudge it with 02 scaling to prevent CEL's but on the newest models they are more sensitive to race cats and with Cobb disabling the ability to hide the CEL, you would have a CEL on the dash because the O2 sensor reads that the cat isn't filtering like OEM, even if nothing is wrong.
And O2 scaling is a chance play, so you might do it and it works, or you could do it and have a downpipe on the car and no way to solve the CEL issue.
It's your call if you want to chance this part, but downpipe is generally one of the bigger power adders.

30-40hp at the crank is easily doable with the stock turbo.
30-40hp at the wheels, on the already bumped up output from the RA motor in the 19+ is asking a lot and then things get much more expensive as you look towards a mild turbo upgrade... I'd avoid that on a canyon carving daily that you'd rather not touch too much.
Plus, while the 19+ motor is stronger than before, it's still more wear than a stock turbo.

The STi fuel system is already approaching it's peak on the 18+ STi, and bolting on more flow parts is going to push beyond that.
Just off the top of my head, here is what I would look into to get a 2020 to the most power possible with the least mods possible, without CEL's (in addition to the reliability mods mentioned above):

  • Equal length headers. -> KillerB is best, Tomei is a decent second - Thats what I have. This will get you a bunch more low end torque, sooner, and will bump your power up a bit throughout the whole rev range. The KillerB is noticeably better than the competition at higher power levels, but for a stock turbo they are all pretty close, as long as they are equal length. You will really notice the increased low end on a daily as the car will pull harder down low even when you aren't pushing it. Make sure this part is tuned for to maximize the gains.
  • Inlet (slight power, more throttle response) -> Needs tune to be safe
  • Injectors -> Needs tune to run at all
  • Fuel pump -> To feed the injectors, doesn't effect tune.
  • Protune -> You need this to get the car to run with above parts, and a protune is the safest and most powerful option for any car.

In addition to above you could consider an intake, but on a stock turbo this is mostly just for the wooshing sounds.
Exhaust is sound, doesn't do much until you put a rather large turbo that needs the flow.
Step-colder spark plugs are an option but not absolutely necessary, but can help a bit with safety when you are pushing the boost.
Stuff like fuel rails and such are mostly just bling until you really push the car (big turbo or e85).
Silicone intake couplers to replace the factory rubber ones are something I did. Might be good for 1hp but they are more durable 😂.

I have a 2012 that I had recently set out to max out the stock turbo with the highest reliability and the least parts necessary.
You can check my parts list on my build thread and just subtract the downpipe to give you a good idea of what would work well for you.

I'd love to say install a downpipe and get a protune, cause that honestly might tide you over and make you grin, but now that play is a gamble on if your tuner can get the o2 scaling right to avoid CEL's lol
 

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Discussion Starter · #18 ·
So AOS, Cyl4 mod, pickup/baffle should be done first for reliability sake.

Unfortunately on a 2020, even with a protune, looks like downpipe isn't really a straightforward option.
Some people have done it and are able to fudge it with 02 scaling to prevent CEL's but on the newest models they are more sensitive to race cats and with Cobb disabling the ability to hide the CEL, you would have a CEL on the dash because the O2 sensor reads that the cat isn't filtering like OEM, even if nothing is wrong.
And O2 scaling is a chance play, so you might do it and it works, or you could do it and have a downpipe on the car and no way to solve the CEL issue.
It's your call if you want to chance this part, but downpipe is generally one of the bigger power adders.

30-40hp at the crank is easily doable with the stock turbo.
30-40hp at the wheels, on the already bumped up output from the RA motor in the 19+ is asking a lot and then things get much more expensive as you look towards a mild turbo upgrade... I'd avoid that on a canyon carving daily that you'd rather not touch too much.
Plus, while the 19+ motor is stronger than before, it's still more wear than a stock turbo.

The STi fuel system is already approaching it's peak on the 18+ STi, and bolting on more flow parts is going to push beyond that.
Just off the top of my head, here is what I would look into to get a 2020 to the most power possible with the least mods possible, without CEL's (in addition to the reliability mods mentioned above):

  • Equal length headers. -> KillerB is best, Tomei is a decent second - Thats what I have. This will get you a bunch more low end torque, sooner, and will bump your power up a bit throughout the whole rev range. The KillerB is noticeably better than the competition at higher power levels, but for a stock turbo they are all pretty close, as long as they are equal length. You will really notice the increased low end on a daily as the car will pull harder down low even when you aren't pushing it. Make sure this part is tuned for to maximize the gains.
  • Inlet (slight power, more throttle response) -> Needs tune to be safe
  • Injectors -> Needs tune to run at all
  • Fuel pump -> To feed the injectors, doesn't effect tune.
  • Protune -> You need this to get the car to run with above parts, and a protune is the safest and most powerful option for any car.

In addition to above you could consider an intake, but on a stock turbo this is mostly just for the wooshing sounds.
Exhaust is sound, doesn't do much until you put a rather large turbo that needs the flow.
Step-colder spark plugs are an option but not absolutely necessary, but can help a bit with safety when you are pushing the boost.
Stuff like fuel rails and such are mostly just bling until you really push the car (big turbo or e85).
Silicone intake couplers to replace the factory rubber ones are something I did. Might be good for 1hp but they are more durable 😂.

I have a 2012 that I had recently set out to max out the stock turbo with the highest reliability and the least parts necessary.
You can check my parts list on my build thread and just subtract the downpipe to give you a good idea of what would work well for you.

I'd love to say install a downpipe and get a protune, cause that honestly might tide you over and make you grin, but now that play is a gamble on if your tuner can get the o2 scaling right to avoid CEL's lol
Austin your a G for this thank you it really does help. Okay so here's the plan:

  • Figure out what threw off my FKL -> Fix it
  • AOS
  • Cyl4 Cool Mod
  • Baffle
  • KB Headers
  • Protune

I think I'm set. Thanks to everyone who helped it really gave a good idea of how these cars can be modded. I will try to give an update of what was up with my readings soon!
 

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Racing is a negative, I got a ticket going 114 and got lucky for not getting anything but a fine so I'm staying clear from that. I honestly just want a fun canyon car. Not sure how subaru mods affect power increase but ~30-40 would be a goal. That being said I am ignorant to this stuff so not sure if that contradicts my previous statements.
i meant racing on track haha. i track mine but drive pretty conservatively on the street. i live right by skyline drive in the blue ridge mountains, and at night when those are near empty sometimes i'll have fun.

so a slight power increase, bascially everything that austin just said. i THINK you can do a downpipe and use HP tuners instead of cobb and still be emissions compliant and not have to worry there, a downpipe, headers, and a tune would get you there. talk to @yamahaSHO, he's a tuner on here, and can remotely tune your car and i'm sure if he can do a 2020 with a cat by adjusting 02 scaling he'd be able to make it work, if not he'd tell you.

all that said, a fun canyon carver is NOT going to be about power, but suspension. a quality tire, quality coilovers, control arms, geometry correction parts (quite a few to list), and bushings will make your car MUCH more fun in corners vs adding power. I really do think that seat time+suspension mods will make your car FAR faster in corners than adding 100whp would. so that is where i'd spend my money if i were you (but def do the reliability mods and a protune, even if everything else is stock).

so far as the protune, it'll be a good thing to have even if everything else is stock, but if you have a 2020, a protune will likely void the warranty, suspension, will NOT void a warranty.
 

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Discussion Starter · #20 ·
i meant racing on track haha. i track mine but drive pretty conservatively on the street. i live right by skyline drive in the blue ridge mountains, and at night when those are near empty sometimes i'll have fun.

so a slight power increase, bascially everything that austin just said. i THINK you can do a downpipe and use HP tuners instead of cobb and still be emissions compliant and not have to worry there, a downpipe, headers, and a tune would get you there. talk to @yamahaSHO, he's a tuner on here, and can remotely tune your car and i'm sure if he can do a 2020 with a cat by adjusting 02 scaling he'd be able to make it work, if not he'd tell you.

all that said, a fun canyon carver is NOT going to be about power, but suspension. a quality tire, quality coilovers, control arms, geometry correction parts (quite a few to list), and bushings will make your car MUCH more fun in corners vs adding power. I really do think that seat time+suspension mods will make your car FAR faster in corners than adding 100whp would. so that is where i'd spend my money if i were you (but def do the reliability mods and a protune, even if everything else is stock).

so far as the protune, it'll be a good thing to have even if everything else is stock, but if you have a 2020, a protune will likely void the warranty, suspension, will NOT void a warranty.
Track days are something that I would like to try out but I honestly don't think I have the dedication for. Suspension tuning is definitely next. Already have the Ohlins in mind. Thanks!
 
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