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Old 02-14-2020, 04:43 AM   #1
srt-4
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Default Cobb Stage 2 w/ SF intake and stock fuel

Ok before you roast, I did a search and read the recommended threads. I'm still ill informed.

So, I'm getting stage 2, SF intake/box, air/oil separator, and a protune on an ' 18 type RA. I know on Cobb's site they don't recommend this setup, but the tuner said there is a lot of misinformation out there regarding this setup and says i'll be fine/safe. This is a very reputable shop that does a wide variety of cars and is a COBB certified gold protuner. (Prolly just means they paid for the title lmao)

So, since I'm sure there is a lot more people that have experience with this setup now vs the old threads I found...I'd love to hear input on people that have actually run this setup or tuners that have tuned it. Assuming no other mods, should this be ok to run with a protune? Is Cobb's non-recommendation simply because it is risky with an OTS tune?

I appreciate any input. Thank you.
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Old 02-14-2020, 09:00 AM   #2
horsePOOGAS
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If the OTS map notes don't list the mods that will work with it then it is not recommended to be used and there is a risk of a lean condition.

Now if you're getting a protune, then the tuner will be able to take care of any mods done to the car and you shouldn't need to worry. You're on the right track my listening to your tuner and what he recommends.
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Old 02-14-2020, 10:14 AM   #3
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Cobb doesn’t do it for their OTS map because they run rich putting IDCs higher with just a DP. So when you add the intake the stock injectors will be running at max if it was an OTS tune from Cobb. With a protune he will tune it to be efficient and safe so you won’t have to worry.
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Old 02-14-2020, 10:46 AM   #4
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Skip the intake IMO, the airbox is better and you can use the money for something else. There is no better intake than the stock airbox until you are pushing enough power to actually need a new one, which you aren't at stage 2. Even truer for the 18RA and 19-20 STI's which have a revised airbox and scoop setup.

I know they sound cool but IAT's will suffer and MAF scaling won't be as good as OEM.
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Old 02-14-2020, 11:26 AM   #5
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Thank you guys so much. This is pretty much exactly what i was looking for. Thanks for the help.
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Old 02-15-2020, 01:39 PM   #6
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Quote:
Originally Posted by srt-4 View Post
Ok before you roast, I did a search and read the recommended threads. I'm still ill informed.

So, I'm getting stage 2, SF intake/box, air/oil separator, and a protune on an ' 18 type RA. I know on Cobb's site they don't recommend this setup, but the tuner said there is a lot of misinformation out there regarding this setup and says i'll be fine/safe. This is a very reputable shop that does a wide variety of cars and is a COBB certified gold protuner. (Prolly just means they paid for the title lmao)

So, since I'm sure there is a lot more people that have experience with this setup now vs the old threads I found...I'd love to hear input on people that have actually run this setup or tuners that have tuned it. Assuming no other mods, should this be ok to run with a protune? Is Cobb's non-recommendation simply because it is risky with an OTS tune?

I appreciate any input. Thank you.
So are you getting a Pro-tune or are you using OTS for the mods? If Pro-tune,
Mods shouldn't matter much since the tune will be tailored for the car. The next concern should be injectors, fuel pump or Fuel Pressure Regulator.

OTS Map has Required parts list...
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Old 02-16-2020, 02:07 AM   #7
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Quote:
Originally Posted by wrxlaunch View Post
So are you getting a Pro-tune or are you using OTS for the mods? If Pro-tune,
Mods shouldn't matter much since the tune will be tailored for the car. The next concern should be injectors, fuel pump or Fuel Pressure Regulator.

OTS Map has Required parts list...
Protune. Will stay on this setup for a while and see how i like it. Next step will be fuel system with E85 conversion, but that will probably be next tax season lol.
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Old 02-16-2020, 11:01 PM   #8
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Running it right now, except with an upgraded pump and regulator pushing higher fuel pressure. Without a new pump and increased pressure it's dangerous. The stock injectors at stock pressure will get overrun but up the psi and tune for it, you're gtg. There's more to get adjusted as well in the tune. If you want more info lmk but I'm not here to steal anyone's business.
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Old 02-16-2020, 11:06 PM   #9
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Quote:
Originally Posted by wrxlaunch View Post
So are you getting a Pro-tune or are you using OTS for the mods? If Pro-tune,
Mods shouldn't matter much since the tune will be tailored for the car. The next concern should be injectors, fuel pump or Fuel Pressure Regulator.

OTS Map has Required parts list...
Parts list schmartslist... do the fpr and pump, skip the injectors... prove me wrong besides what cobb has to say.
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Old 02-20-2020, 09:36 AM   #10
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Quote:
Originally Posted by BurninSTI View Post
Parts list schmartslist... do the fpr and pump, skip the injectors... prove me wrong besides what cobb has to say.
Going to run into fueling issues... fuel system is already close to max. He'll fined out.
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Old 02-20-2020, 10:08 AM   #11
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Quote:
Originally Posted by wrxlaunch View Post
Going to run into fueling issues... fuel system is already close to max. He'll fined out.
Why do the newer STI's suddenly (supposedly) need more fuel than we ever did on the GD's? Stage 2 cars never needed injectors before, why now? They aren't making anymore power than they ever did 15 years ago.
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Old 02-20-2020, 10:49 AM   #12
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Quote:
Originally Posted by sluflyer06 View Post
Why do the newer STI's suddenly (supposedly) need more fuel than we ever did on the GD's? Stage 2 cars never needed injectors before, why now? They aren't making anymore power than they ever did 15 years ago.
exactly, for a stage 2 tune stock turbo could never push that much to need more fuel than the stock system can handle....unless the new STI is using a new bigger turbo or something...? Basically stage 2 used to consist of aftermarket exhaust and intake and a tune....
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Old 02-20-2020, 12:27 PM   #13
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Supposedly, the newer models make more power even when modded. This was initially discovered when the 15s were released.. and then another power bump was noticed with the 18 RA/19+ STIs.

One theory was that the hotside of the turbo was larger. Perrin initially speculated this and BrenTuning also noted a significant difference on the dyno when comparing a 2014 vs 2015 STI. Some members of the community then confirmed this by measuring their VF48s.

https://www.perrin.com/blog/post/per...obb-accessport

Quote:
Originally Posted by BrenTuning
While not as drastic, the 2015 STi received some changes of its own. As noted by Perrin, they seem to think that the 2015 STi received a VF-48 with a larger hotside than previous years. All of our dyno testing and comparison to previous MY agree with their findings.

2015 STi vs 2014 STi
Like mentioned earlier, the 2015 STi makes roughly 20WHP more with OEM mapping compared to the 09+WRX/STi. Below is a baseline comparison between the two vehicles (2015 STi vs 2014 STi). As you can see, the 2015 makes more power throughout the whole RPM range compared to its predecessor.

Quote:
We have compared measurements of the turbos from a 2011 sti and a 2015 sti. Below are the results. Because of the nature of the measurements, we are going to look to X.XX decimal places rather than X.XXX to reduce the human error that can be present in something like this.

2015 vs 2011:

Compressor inlet:
Intake ID=1.854"
Intake ID=1.853"

Compressor outlet:
To IC ID=1.593"
To IC ID=1.578"

The 2015 sti compressor outlet ID going to the intercooler is .015" larger. This gives the intake side going into the IC a larger flowing area of .0326 in^2. Not huge, but something.

From UP ID=1.761" = 15.714 cm^2 area (~2.04 cm^2 or 14.89 % larger)
From UP ID=1.643" = 13.678 cm^2 area

Whoa wait a minute, something has to be wrong. The 2015 sti has a larger turbine inlet ID coming from the uppipe of .118" and a larger flowing area of .316in^2. OK that's huge.

In conclusion, this is a very short and sweet theory that the 2015+ STI has a larger turbo, even though its called a vf48. What does this mean? The 15's turbos are probably part if not most of the reason there is a reported power increase.

Last edited by WRXnick16; 02-20-2020 at 01:15 PM.
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Old 02-20-2020, 12:35 PM   #14
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Quote:
Originally Posted by WRXnick16 View Post
Supposedly, the newer models make more power even when modded. This was initially discovered when the 15s were released.. and then another power bump was noticed with the 18 RA/19+ STIs were released.

One theory was that the hotside of the turbo was larger. Perrin initially speculated this and BrenTuning also noted a significant difference on the dyno when comparing a 2014 vs 2015 STI. Some members of the community then confirmed this by measuring their VF48s.

https://www.perrin.com/blog/post/per...obb-accessport
Thanks I was unaware of the changes to the stock turbo, that makes sense now.
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Old 02-20-2020, 01:05 PM   #15
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Of course Subaru never announced this and the VF48 part # remained the same. So who knows if it was an intentional design change or the result of an IHI casting/manufacturing change.
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Old 02-20-2020, 03:26 PM   #16
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Not to hijack, just curious... How much of a performance difference would there be on a 2016 STi by adding the Cobb SF intake (w/correctly adjusted tune) to a Stage 2 setup consisting of Cobb TBE exhaust, everything else stock.

I do understand IAT's will suffer, MAF scaling won't be as good as OEM and the tune will need to taper because IDCs being pushed.

Does anyone have a dyno graph comparing the two?
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Old 02-20-2020, 03:43 PM   #17
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Quote:
Originally Posted by OhThatHurt View Post
Not to hijack, just curious... How much of a performance difference would there be on a 2016 STi by adding the Cobb SF intake (w/correctly adjusted tune) to a Stage 2 setup consisting of Cobb TBE exhaust, everything else stock.

I do understand IAT's will suffer, MAF scaling won't be as good as OEM and the tune will need to taper because IDCs being pushed.

Does anyone have a dyno graph comparing the two?
I have been stage 2 (TBE) for a while now. before that I was stage 1 (SF intake and CBE) for a good while and the increase is very noticeable. I am ready to go stage 3 (stage 2 + injectors and pump) and I hope its as good a bump as it was when I went to stage 2.
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Old 02-20-2020, 04:27 PM   #18
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Quote:
Originally Posted by OhThatHurt View Post
Not to hijack, just curious... How much of a performance difference would there be on a 2016 STi by adding the Cobb SF intake (w/correctly adjusted tune) to a Stage 2 setup consisting of Cobb TBE exhaust, everything else stock.

I do understand IAT's will suffer, MAF scaling won't be as good as OEM and the tune will need to taper because IDCs being pushed.

Does anyone have a dyno graph comparing the two?
There will be minimal power difference with the intake, especially when limited by IDCs on the stock injectors. The intake will show marginal gains after 5,000 rpm even with the upgraded fuel system.. which is the region that power will need to be tapered on the stock injectors. It'll mostly be a "noise maker" mod. IMO, not worth the money for the intake & tune from a performance standpoint unless you're just after the sound.

Here are Cobb's dynos for stage 2 & stage 3 (with upgrade fuel system). There's probably a ~10-15 hp gain (+/-) after 5k rpm. Figure less than that with the tune scaled back for stock injectors.

Stage 2:


Stage 3:


I personally recommend going with an ELH before an intake. But most people just follow Cobb's stages or are just after the sound that an intake and the OEM UELH offer.

Last edited by WRXnick16; 02-20-2020 at 04:51 PM.
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Old 02-20-2020, 04:39 PM   #19
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@WRXnick16. Thanks for the insight. I appreciate it.
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Old Yesterday, 03:01 PM   #20
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Originally Posted by wrxlaunch View Post
Going to run into fueling issues... fuel system is already close to max. He'll fined out.
Well, was just out doing some on road tuning today, the only issue I have found so far is that on initial startup the fuel lines make a hammering noise that is extremely annoying... other than that doing 1-3 wot pulls the highest my idc's went was 98%, theres no way to max out the injectors in the low gears from what I have seen. Is anyone really going wot in 5th and sixth? I guess if you wanna do that then possibly they'll get overrun but you would probably need an ewg to get rid of boost creep pulling in a high gear that long anyways. I'll stick to fun below 100 and save myself the $1500 that injectors, ewg/pipe would cost me until im ready to build the shortblock.
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Old Yesterday, 07:29 PM   #21
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The highest I'd want to see my IDC is 90% tops. Calibrators aim for 80%, that's what it's at stock.

Cobb Stage 2 (catted) puts you at the limit which is why Stage 3 package includes the fuel system upgrade, and they're only adding what... their SF intake and a turbo inlet. I'd do the same going catless, at least pump and injectors.
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