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Old 09-17-2012, 12:51 AM   #1
DieselMaytrain
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Default Cobb SF Intake W/O Accessport

I was looking into getting a Cobb SF Short Ram intake for my 09 WRX Sedan. Do i need to have the access port too?

I don't want to have to run with the check engine light on or mess my car up in any way so i decided to ask here first!
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Old 09-17-2012, 01:01 AM   #2
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this intake requires tuning. you dont need an accessport, but you need to tune for it.

Wicked M@
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Old 09-17-2012, 01:07 AM   #3
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Great thanks. I guess that means don't run long w/out getting it tuned or getting the AP?
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Old 09-17-2012, 01:11 AM   #4
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^ What he said
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Old 09-17-2012, 01:11 AM   #5
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Originally Posted by DieselMaytrain View Post
Great thanks. I guess that means don't run long w/out getting it tuned or getting the AP?
Don't run it at all without a tune.
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Old 09-17-2012, 01:28 AM   #6
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That's what I thought. Thanks!
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Old 09-18-2012, 02:43 PM   #7
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Some intakes are acceptable to run without a tune, such as the K&N. That intake doesn't change the diameter, therefore flow dynamics are unchanged, meaning no tune is required. Is it recommended? Oh yeah. Cobb does require a tune, so please consider your engine management before doing this or any intake.
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Old 09-18-2012, 03:50 PM   #8
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Quote:
Originally Posted by Decipher View Post
Some intakes are acceptable to run without a tune, such as the K&N. That intake doesn't change the diameter, therefore flow dynamics are unchanged, meaning no tune is required.
It doesn't matter if the diameter is the same. The flow pattern is different, which throws off the MAF scaling.

ALL intakes for the 08+ WRX/STi need a tune...ALL of them, there are no exceptions. None of them measure close enough to stock to work with the stock scaling.
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Old 09-18-2012, 03:54 PM   #9
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Quote:
Originally Posted by the suicidal eggroll View Post
It doesn't matter if the diameter is the same. The flow pattern is different, which throws off the MAF scaling.

ALL intakes for the 08+ WRX/STi need a tune...ALL of them, there are no exceptions.
BINGO, except no substitute answers.
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Old 09-18-2012, 04:04 PM   #10
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this is absolutely my findings as well for 08+ cars.

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Old 09-18-2012, 04:15 PM   #11
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Save your 275$ and buy the accessport. Stage 1 with that will produce a bigger smile than the intake. Trust me.
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Old 09-18-2012, 06:47 PM   #12
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For any 08+ WRX and STi any intake changes require a tune. We did testing on this a few years ago when trying out different stuff on 08+ cars and ran into it the sensitivity issue of these cars and air flow.

This dyno plot shows the AFR curve, however we ended up having to richen the car out to correct for the change in flow when we did a drop in. I dont remember exactly the #'s but it was along the line of .5-.75:1 lean out when going from OEM to drop in high flow filter.


So in a nut shell, stick with OEM air filter and airbox unless you plan on tuning for it.

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Old 09-18-2012, 07:31 PM   #13
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Quote:
Originally Posted by RallySport Direct
For any 08+ WRX and STi any intake changes require a tune. We did testing on this a few years ago when trying out different stuff on 08+ cars and ran into it the sensitivity issue of these cars and air flow.

This dyno plot shows the AFR curve, however we ended up having to richen the car out to correct for the change in flow when we did a drop in. I dont remember exactly the #'s but it was along the line of .5-.75:1 lean out when going from OEM to drop in high flow filter.

So in a nut shell, stick with OEM air filter and airbox unless you plan on tuning for it.

Kirill
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Curios why, if you know this, you don't always correct the vendors on your site when they tell people that they don't need to tune specific intakes. Might want to look into that so people don't make their engines go pop!
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Old 09-18-2012, 07:41 PM   #14
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We do our best to educate our customers on stuff like this, however its ultimately their decision on what to get and how to modify their car.
Some manufactures state that tuning is not required based on how they designed the intake system. And others say they do, so we list information as the manufactures to stay consistent between them and us as we have not tested EVERY system on the market.

When a customer calls in and asks about it, our reps will specify that we suggest a tune for 08+ WRX's and STi's if any intake changes are made of how air flows over the MAF sensor.

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Old 09-18-2012, 07:46 PM   #15
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Quote:
Originally Posted by the suicidal eggroll

It doesn't matter if the diameter is the same. The flow pattern is different, which throws off the MAF scaling.

ALL intakes for the 08+ WRX/STi need a tune...ALL of them, there are no exceptions. None of them measure close enough to stock to work with the stock scaling.
I had this exact sediment before I did some heavy reading. Everything I read before indicated this very thing and, if you were to view my posting history, you can see just that. HOWEVER, after reading some very interesting data, I changed my feelings on this. I will try to dig up my sources and post them. I am not one to hand out poor, misinformed, and uneducated information. No matter what, I would never put an intake on and not tune for it. There are companies, however, who have the R&D into their intakes and say they run just fine without a tune. Let me find those articles.
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Old 09-18-2012, 07:55 PM   #16
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Here's a figure showing the percent change in MAF readings for 6 different aftermarket intakes versus the stock intake. The K&N IS one of those being plotted here.



If you think a 10%+ lean shift at WOT is fine, then more power to you, but I don't, and I wouldn't go around telling other people that they don't need a tune for it either. The Perrin intake is also one of those being plotted here, it's actually SMALLER diameter that stock, yet it too has a 10%+ lean shift at WOT. Just the other day one of the Perrin reps posted in a thread in the Newbie forum and backed up that statement, the Perrin intake runs 10% lean at WOT on the stock tune. They are of the opinion that a 10% shift is not enough to warrant concern since the stock tune runs so rich anyway, but I don't agree with that sentiment.
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Old 09-18-2012, 08:24 PM   #17
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These cars are so touchy, pretty much anything aftermarket you install, has to be tuned. Like I said, get the AP, and get OTS maps for it. I STILL got a protune, but if you really wanna save some cash (and run a risk over time) just get the AP. Newer gen subaru's are too damn touchy not too. I remember on my bugeye when I had a catless blitz nur spec tbe. A tune was not needed. The car ran pig rich, which was fine. Albeit I wasn't getting the most potential out of the exhaust without the tune, I could still run it without issue. These days, you just can't.
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Old 09-18-2012, 10:50 PM   #18
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Quote:
Originally Posted by Decipher
Some intakes are acceptable to run without a tune, such as the K&N. That intake doesn't change the diameter, therefore flow dynamics are unchanged, meaning no tune is required. Is it recommended? Oh yeah. Cobb does require a tune, so please consider your engine management before doing this or any intake.
I'm quoting myself to show just what I said. Some manufacturers say it's okay to run without a tune. They claim it's safe. Would I run without one? No. Did I tell the OP to run without one? No. Quite the contrary. Maybe I wasn't clear enough in my statement that the sediments of not tuning were that of manufacturers and not me. Note: I have my car tuned to my intake.

I've done my part to save face. Apologies if this wasn't clear. Nonetheless, a 10% increase in lean spots on an already grossly lean OEM tune is not acceptable by any standard.
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Old 09-18-2012, 11:51 PM   #19
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Quote:
Originally Posted by Decipher View Post
Maybe I wasn't clear enough in my statement that the sediments of not tuning were that of manufacturers and not me.
I didn't catch that in your post, no worries. I guess K&N is like Perrin in that they assume a 10% lean shift isn't enough to warrant concern on a stock tune.
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Old 09-19-2012, 08:28 AM   #20
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That's truly unbelievable. Anyways, I strongly look down on those who hand out bad info just to bump their post count. The last thing I want to do is spread bad info. Either way, Perrin and presumably K&N's stance on this lean spot is amazingly sad.

Last edited by Decipher; 10-24-2012 at 06:51 PM.
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Old 10-24-2012, 03:51 PM   #21
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Default good advice

I just ordered a cobb sf intake and thought that it was not necessary to tune it, but this thread has inspired me to order the accessport. I want to do this car right!
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Old 10-24-2012, 06:51 PM   #22
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Great choice. You won't regret it.
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Old 10-24-2012, 07:05 PM   #23
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Pretty sure MAF diameter changes, so in order for your MAF to read correctly, you need a tune / or access port to rescale for the car to run properly.
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Old 10-24-2012, 09:01 PM   #24
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Quote:
Originally Posted by Subarusaurus_Rex View Post
I just ordered a cobb sf intake and thought that it was not necessary to tune it
What on earth gave you that idea? EVERYTHING, including the website where you buy the intake, says that it MUST be tuned for.

http://www.cobbtuning.com/Subaru-SF-...t-p/715100.htm

It's even highlighted in bold red print...
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Old 10-25-2012, 10:51 AM   #25
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You should just install it and report back here after 5000 miles and let us know if your engine is still alive.
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