Cobb Stage 2 w/ SF intake and stock fuel

[srt-4]

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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[horsePOOGAS]

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.

[08redWRX]

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.

[sluflyer06]

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.

[srt-4]

Thank you guys so much. This is pretty much exactly what i was looking for. Thanks for the help.

[wrxlaunch]

Originally Posted by srt-4

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...

[srt-4]

Originally Posted by wrxlaunch

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.

[BurninSTI]

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.

[BurninSTI]

Originally Posted by wrxlaunch

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.

[wrxlaunch]

Originally Posted by BurninSTI

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.

[sluflyer06]

Originally Posted by wrxlaunch

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.

[murrdogg24]

Originally Posted by sluflyer06

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....

[WRXnick16]

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

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.

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.

[murrdogg24]

Originally Posted by WRXnick16

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.

[WRXnick16]

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.

[OhThatHurt]

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?

[hoang5659]

Originally Posted by OhThatHurt

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.

[WRXnick16]

Originally Posted by OhThatHurt

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.

[OhThatHurt]

@WRXnick16. Thanks for the insight. I appreciate it.

[BurninSTI]

Originally Posted by wrxlaunch

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.

[siete]

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.

[SubeySTi2011]

From what my tuner told me on my RA is that just going stage 2 without injectors or any fuel modification will max out the stock injectors especially on a cold climate day they tend to go 100% very quickly. He recommended at least a fuel pump and highly suggested injectors to be safe. a set of 1050x arent too expensive for piece of mind and will make over 400whp on pump so that is what i am going to do for the time being

[WRXnick16]

Originally Posted by SubeySTi2011

From what my tuner told me on my RA is that just going stage 2 without injectors or any fuel modification will max out the stock injectors especially on a cold climate day they tend to go 100% very quickly. He recommended at least a fuel pump and highly suggested injectors to be safe.

IDC and fuel upgrade requirements vary from tuner to tuner. Most tuners will tune stage 2+ and just scale the power back to what they feel is a safe IDC. Upgrading the fuel pump with the stock injectors & FPR is... a waste of money IMO. The stock fuel pump is plenty sufficient for the stock injectors. The FPR determines the fuel pressure and amount of fuel that can be delivered by the stock injectors. Upgrading the fuel pump on its own won't provide any additional fuel or help lower IDCs. Sure upgrading the fuel pump will re-ensure that you have adequate fuel pressure.. but do you trust the reliability of an aftermarket pump over the OEM unit?

Of course, there's the debate on how Subaru's IDCs are calculated (based on IPW & RPM) and many tuners have gone well over 100% IDC (see end of post). IDC is a calculated value (with a margin of error), not a raw counter produced by the ECU. Obviously going over 100% wouldn't be possible if the IDC values were accurate, real-time values. I've seen tuners go as high as 120% IDC, but of course those tunes run a higher risk of running lean under the right conditions. In that case, you need to pay close attention to the AFRs, especially in colder weather and at high load in higher gears. Or if you spend extended periods of time at high RPMs (track car).

Cobb tests in cool climates with high atmospheric pressure (low altitude) where the air density is high (demanding more fuel) to check their IDCs. At stage 2+, their IDCs were at 107% with their AFR and they considered that unsafe for an OTS tune in that environment. Of course they err on the side of caution which is why they're known for their long-term reliability. Their tunes also run on the richer side for added safety (using more fuel) which further increases their higher IDCs. A protune will typically run leaner resulting in more power and lower IDCs. Cobb also wouldn't mind convincing you to spend more money on their fuel upgrade package nor would a shop mind selling it to you and charging you for the installation.

Subaru's reported 100% IDC != absolute 100% IDC (static injector operation). For example, 126% IDC:

[wrxlaunch]

Originally Posted by BurninSTI

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.

Who purchased a STi or WRX to only go WOT in 1-3 gear? What would happen on a cold day to that IDC?

[WRXnick16]

IDCs start to become a limitation at the top of 4th gear on Stage 2+ setups with the stock injectors.

While this is a "limitation".. how much time does an average street car spend at WOT at ~90-100+ mph?

It just so happens that 4th gear is the most commonly used for dyno tuning and the higher IDCs are observed. Tuners will of course err on the side of caution. They don't want any responsibility (blame) in you potentially running lean, detonating, and experiencing a catastrophic engine failure. They also have to assume the worst of your driving habits (ie maniacally doing extended WOT pulls in excess of 100 mph at sea level in below freezing temperatures when air is the densest despite your their warnings about IDCs with the stock injectors).

I'm not opposed to upgrading the injectors at Stage 2+, but it isn't really necessary for a daily driver unless it's spending weekends doing extended track sessions. If you have the money to burn and it helps you sleep better at night.. then by all means go for it. Or just reach out to a few experienced tuners and ask their opinion. Most will be willing to tune your setup on the stock injectors. They'll just scale power back a bit in the higher gears for safety. For example:

Originally Posted by BrenTuning

We can tune Stage2+SF setups safely with IDC at a safe level even on stock fueling. With stock fueling, the power just has to be scaled back a bit.

IDC on the Stage2+SF stock injector setup was right around 95% at the top of 4th gear. With the ID1000 injectors and DW65C pump, the IDC was around 60%. As for tuning differences go, you have to run a leaner mixture and taper the boost on the stock fueling car, with ID1000 you can run a bit more timing and boost.

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