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Discussion Starter · #1 ·
I was planning on getting a downpipe on my 2018 STI. I heard that you can鈥檛 run the Cobb stage 2 with an intake. I also called a tuner and he said if I wanted to put it downpipe on there I would really need to put new injectors on. 馃

please help.
Currently running a full nameless cat back and Cobb stage 1+
 

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2020 Subaru WRX STI
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You really shouldn't run anything off the Cobb OTS maps, not for an extended period of time anyways.

Also, run far and fast. Get a different tuner.
 

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SWP 2012 GR Hatch
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Stage 2 is literally just a downpipe.
Nothing else necessary, but you can run an exhaust too if you want to (it's just for sound).
I ran Stage 2 with only a downpipe from Feb=Oct without issues before going further.

There is a Stage 1 and a Stage 1+intake.
On the new cars (2015+) the turbo hot side is more efficient than the previous gens so it's not 'safe' to run an intake and a downpipe together in Cobb's eyes.
Therefore, Stage 2 is only available for the downpipe, but no downpipe+intake.
There is some truth to what your tuner is saying, but they are probably just trying to upsell you on injectors (and fuel pump), and a tune, rather than tell you to pull the intake to go Stage 2 safely.

You'll get more power from Stage 2 with a downpipe than you would from Stage 1 with an intake, you just lose the whooshing noises.

You can go stage 2 with the stock intake, or you can do the intake and the downpipe together but you might need some fuel support because of the better flow, and you'll need a pro tune for those extra mods, plus there is no downpipe+intake tune available from Cobb anyways.

If you wana keep it simple, just do downpipe + Stage 2.
If you wana do a pro tune so you can run both, I'd think about what else you want to add at the same time.
The inlet is a big one for throttle response, the FPR for stumble, the EBCS for precision on the tune, and there are a few more things you should consider (Do you want headers? Do you want to do EGR and TCV deletes? etc.)
The hole runs deep once you jump in.

Just as food for thought, I'm stage 2+ with headers and a bunch of mods with a pro tune.
I didn't want an intake or an exhaust because I didn't want wooshing and buzzing.
I'm running headers and downpipe, stock exhaust.
KillerB Inlet and silicone Grimmspeed couplers with the stock airbox.
I don't think I'm leaving much on the table in terms of power, just noise.
The stock intake/exhaust really can handle up to 350-400whp before they become a restriction.
Point being, if Stage 2 is on the table, I'd be quicker to throw the downpipe on with the stock intake for the power than worry about not being able to run an aftermarket intake for the wooshing.
 

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Discussion Starter · #4 ·
Stage 2 is literally just a downpipe.
Nothing else necessary, but you can run an exhaust too if you want to (it's just for sound).
I ran Stage 2 with only a downpipe from Feb=Oct without issues before going further.

There is a Stage 1 and a Stage 1+intake.
On the new cars (2015+) the turbo hot side is more efficient than the previous gens so it's not 'safe' to run an intake and a downpipe together in Cobb's eyes.
Therefore, Stage 2 is only available for the downpipe, but no downpipe+intake.
There is some truth to what your tuner is saying, but they are probably just trying to upsell you on injectors (and fuel pump), and a tune, rather than tell you to pull the intake to go Stage 2 safely.

You'll get more power from Stage 2 with a downpipe than you would from Stage 1 with an intake, you just lose the whooshing noises.

You can go stage 2 with the stock intake, or you can do the intake and the downpipe together but you might need some fuel support because of the better flow, and you'll need a pro tune for those extra mods, plus there is no downpipe+intake tune available from Cobb anyways.

If you wana keep it simple, just do downpipe + Stage 2.
If you wana do a pro tune so you can run both, I'd think about what else you want to add at the same time.
The inlet is a big one for throttle response, the FPR for stumble, the EBCS for precision on the tune, and there are a few more things you should consider (Do you want headers? Do you want to do EGR and TCV deletes? etc.)
The hole runs deep once you jump in.

Just as food for thought, I'm stage 2+ with headers and a bunch of mods with a pro tune.
I didn't want an intake or an exhaust because I didn't want wooshing and buzzing.
I'm running headers and downpipe, stock exhaust.
KillerB Inlet and silicone Grimmspeed couplers with the stock airbox.
I don't think I'm leaving much on the table in terms of power, just noise.
The stock intake/exhaust really can handle up to 350-400whp before they become a restriction.
Point being, if Stage 2 is on the table, I'd be quicker to throw the downpipe on with the stock intake for the power than worry about not being able to run an aftermarket intake for the wooshing.
i really appreciate the response, just the answers I was looking for. So you don鈥檛 think running a stage 2 OTS Cobb map will hurt the motor? I am going to put the stock air box back on and just buy a Cobb downpipe.
 

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SWP 2012 GR Hatch
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i really appreciate the response, just the answers I was looking for. So you don鈥檛 think running a stage 2 OTS Cobb map will hurt the motor? I am going to put the stock air box back on and just buy a Cobb downpipe.
A pro tune is definitely "better" for sure, but the Cobb map is just conservative.
If you run good fuel you should be fine.
I'm in Canada so our gas isn't fantastic so i run 94 octane exclusively, and even ran the Cobb Stage 2 ACN tune just to be safe.
Idk what areas have the good gas in the states, but I'd be running 93 octane since the price difference isn't a ton per gallon.
Here, 94 is about 30-40 cents more per gallon but I still didn't risk it before or try to have the car pro tuned on 91 octane later because I'd rather pay an extra 5$ per tank than give up performance and increase risk.
93 oct adds safety, ACN tune adds safety, your call!
You can try the regular stage 2 on your fuel of choice and see about the "feedback knock" and "fine knock learn".
If you get anything over -2.8 for either or register higher than -1.4 on a regular basis, I'd consider the 93/ACN or a pro tune.
 

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Discussion Starter · #6 ·
A pro tune is definitely "better" for sure, but the Cobb map is just conservative.
If you run good fuel you should be fine.
I'm in Canada so our gas isn't fantastic so i run 94 octane exclusively, and even ran the Cobb Stage 2 ACN tune just to be safe.
Idk what areas have the good gas in the states, but I'd be running 93 octane since the price difference isn't a ton per gallon.
Here, 94 is about 30-40 cents more per gallon but I still didn't risk it before or try to have the car pro tuned on 91 octane later because I'd rather pay an extra 5$ per tank than give up performance and increase risk.
93 oct adds safety, ACN tune adds safety, your call!
You can try the regular stage 2 on your fuel of choice and see about the "feedback knock" and "fine knock learn".
If you get anything over -2.8 for either or register higher than -1.4 on a regular basis, I'd consider the 93/ACN or a pro tune.
i run 93 octane all the time. I just ordered the Cobb downpipe and heat shield yesterday, got a little bit of a deal with Black Friday. I鈥檓 excited to put it on and see the difference. I鈥檒l admit that I need to learn about the feedback knock and fine knock learn because I am not familiar.
 

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SWP 2012 GR Hatch
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i run 93 octane all the time. I just ordered the Cobb downpipe and heat shield yesterday, got a little bit of a deal with Black Friday. I鈥檓 excited to put it on and see the difference. I鈥檒l admit that I need to learn about the feedback knock and fine knock learn because I am not familiar.
I picked my dp up on last year's BF sale!
Wish I knew at the time I would be going further as I could have picked up a bunch more parts at the discount.

My monitors are set to:
Boost, Coolant temp, DAM, FNL, FK, and recently i added injector duty cycle when I was still on stock injectors, but this really isn't necessary.

Boost is obvious.

Coolant temp so I can gauge warmup. I don't leave the driveway till coolant hits 100 and don't get into boost till I've been sitting above 185 for around 5 mins.

DAM shouldn't change, and only really changes if FNL and FK get bad at some point, but just good to ensure it stays at 1.

FNL is the car making on the fly adjustments to the timing to prevent knock. This is a good indicator of what kind of shape the gas is in that's in the car, combined with various factors like temp. FNL isn't 'bad' for the car, but it's just good to see because if you're hitting higher numbers on this (anything above -2.8) or medium numbers regularly (around -2.8, -1.4 is fine), there is an issue, either with the car, the tune, or the gas. If this ever hits a high number, like 5, there is a good chance the DAM will drop, but that shouldn't happen (unless something is wrong).

FBK is actual knock in the engine as it's happening. FBK is always bad, but small numbers like -1.4 are tolerable and can happen here and there. It's when you're hitting -2.8 or higher that you have to be concerned, and if you get an extreme knock event like a -5, that is bad and deff something to be concerned about. If I got a feedback knock that high and I wasn't on an ACN tune, I'd deff be pulling over and switching to one, or if pro-tuned i'd start logging right away so if it happens again I'd book the car in with the tuner to review the log and address the issue.
 
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