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2005 Forester XT
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15 Posts
Discussion Starter · #1 ·
Hello all, I am new to tuning/modding cars and was just wondering if i need a protune/cobb accessport to run a catback exhaust efficiently
 

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MY05 Forester 2.5 XT 5MT
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Changing a CatBack ? No you don't need a remap (Tune)

Changing a Cat from factory to Sports cat or De-Cat ? Yes you need a remap (Tune) or your pistons will tell you they feel about running lean.

The only exception is the Up-Pipe from the exhaust manifolt-Turbo pipe. That has a cat in the MY05 (Pre-Facelift) 2.5XT but you can remove this with a De-Cat pipe without any problems - I know because I've done this and had my fuelling checked since.

Edit: I have zero experience with generic off the shelf tuning boxes. Personally I would be very wary and prefer to get a map for my specific car and fuel....But each to their own.
 

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2005 Forester XT
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I apologize for the vagueness in my post. And I was referring to changing factory exhaust to sports catback. Thank you for the detailed explanation. I was told by the local tune shop that i need to have the tuning box (cobb accessport) in order to have a custom tune done on my car. Are they trying to rip me off of $650?
 

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2007 Forester XT
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49 Posts
Your motor will be running lean if you replace your exhaust. I experienced a loss in gas mileage when I tampered with mine without a tune. In the end I put my exhaust back to stock. I am going to wait until I get all the parts I want to put on my car then get a tune to accommodate them. You do not want your motor running lean for an extended period of time as it can cause all sorts of problems.
 

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2017 VW Golf SportWagen 5MT
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10,784 Posts
Replacing a catback (resonator pipe + axleback) will not make enough difference -- no need to retune for that.

Replacing a downpipe will make a difference -- need to tune for it, AP will work.

Downpipe + resonator pipe + axleback = turboback -- need to tune for it, AP will work.

Guessing, but better-flowing downpipe without a tune wouldn't make as big of a difference to the AFR as it would to building and controlling boost (which, I guess would throw off the AFR, so alright..). Point I'm trying to make is size of exhaust AFTER the downpipe doesn't really matter as much, unless you really choke it down.

Stan
 

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MY05 Forester 2.5 XT 5MT
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I was told by the local tune shop that i need to have the tuning box (cobb accessport) in order to have a custom tune done on my car. Are they trying to rip me off of $650?
It does sound like it - Unless the ECU for the American market was locked or runs on different programming... Unlikely but possible since you have additional emission codes and a different PCV valve setup.
You can have your Forester remapped (Tuned) via Opensource. This simply requires a laptop and cable to flash the new map onto it. These are typically carried out on a rolling road, then checked on the road afterwards.

Depending upon your power goals, you may not require a map at all. So I guess the obvious question would be, what are your power goals? Do you have any modifications at the moment?

I ask because with a Cosworth air panel filter, using the factory intake. A de-cat up pipe and a Tomei catback system (So didn't touch the downpipe or under-car cats) Along with silicone intake pipe and silicone turbo-intercooler pipe and silicone intercooler-throttle body, I made 253bhp ish on the factory map using 99RON fuel (not sure if this is available where you are) I've had it on a rolling road to check the fuelling and it was perfect :)

Post with printouts: http://www.subaruforester.org/vbulletin/f75/euro-dyno-figures-27666/index9.html#post6403705

If you want to go a different direction for more power and torque, then you will certainly require a remap, again this could be achieved via opensource if you have a mapper/tuner in your area that is able to do this.

Edit: This diagram might be useful when figuring out which pipes sections you might want to change
 

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2005 Forester XT
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15 Posts
Discussion Starter · #7 ·
I see, my power goals are similar to what you have. I would like 300+ horsepower but I don't have anywhere near the amount of money required for that kind of power. But yes I have a silicone turbo inlet ( I believe Mishimoto inlet but I have no idea ) also I have a K&N Typhoon cold air intake.

I might be wrong but I believe 91 octane fuel is the highest octane available for us here in California.

I love that diagram man! It was invaluable to me a few months ago when I was fixing a preturbo exhaust leak haha. My car literally sounded like a vacuum cleaner upon reaching 2500 Rpms.

But anyway thanks again for your detailed feedback and information man! I appreciate it
 

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2006 G35 Sedan Auto
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551 Posts
no need for a tune if you are only running a cat back exhaust. When you add a downpipe you need a tune. Accessport is the best bet, but you can get an open source tune if you want. Just know that when you have to go back to stock downpipe for smog reasons, you might throw a code(not 100% sure).

You don't really need to run an aftermarket intake. If your running a short ram, you could be losing power because you getting hot engine air and not cooler air from outside.

With an intake you need to get it tuned on Forced induction engines.
 

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2005 Forester XT
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15 Posts
Discussion Starter · #9 ·
I talked to the local tune shop, they supposedly specialize in Subaru tuning (specifically STI and XTs) they told me the specific intake I have usually doesn't require my car to be tuned/remapped. I trust them but at the same time I trust people on this forum more.

I do not plan on installing an aftermarket down pipe any time soon but thank you for your help it is much appreciated
 

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2017 VW Golf SportWagen 5MT
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10,784 Posts
Is it a shorty intake, like an exposed cone filter in your engine bay? It gets hot in Fairfield. These cars get heatsoaked pretty good under the hood with the turbo being right there, I personally would never run a shorty.

Cold air intakes, like the Prodrive one, have a pipe running into the fender well, drawing air outside of the engine bay -- you want that. Stock intake draws from a scoop above the radiator from what I remember, also oitside air.

Stan
 

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2005 Forester XT
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15 Posts
Discussion Starter · #11 ·
"Hot" is an understatement to me personally especially after this summer lol. That is beside the point though, yes I believe I have a short ram. And yes it is exposed in the engine bay. I suppose I messed up and wasted $300 on a short ram as opposed to doing a little more research and finding out what would work better. I trust you though and I most likely will switch over.

However the reason I bought the K&N was because when I bought the car 2 months ago I figured out the intake hose leading to the turbo inlet from the intake box was torn and the box itself was cracked. So I said to myself "might as well upgrade to a cold air intake as opposed to replacing OEM intake" although im beginning to realize that was a mistake frim what people are telling to me.

Like I said I trust you and I will probably swith to OEM or find a true CAI after doing more research
 

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MY05 Forester 2.5 XT 5MT
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To get around the heatsoak problem, you could try something like this:


I'm not sure if you're aware but if you go with a cone filter, there is a chance it can suck up water if you drive through deep puddles.

Personally I would stick with the factory intake system and simply install a decent air filter
You might find these 2 threads worth reading through in regards to the Cold Air Intake and the capability of the factory intake system so you can make up your own mind:
http://www.subaruforester.org/vbulletin/f75/forester-sti-does-need-remap-intake-298137/
http://www.subaruforester.org/vbulletin/f75/cai-not-worth-apparently-120996/

Just an idea but if you plan on increasing the performance, make sure the timing belt (and idler pulleys) and water pump are all up to date maintanence wise and if the radiator is the original from factory, it is on borrowed time before it cracks/leaks and could cause a major overheat... The factory radiators in my experience, generally last around 100,000 miles or 10 years. Sorting those 2 items would give you a great foundation to work up the performance on.
 

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'03 forester xs, '05 forester xt.
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15 Posts
Sorry to bump an old thread but instead of asking basically the same question again on a new thread Id try here first..

So I bought my '05 a few months ago and just had to have the transmission replaced, the coilpack n seloniods all blew out for some reason, my guy said either a short in electrical or the axels were rusted to all hell and the previous owner took them apart but didnt grease them or anything and the seized up the trans or something like that
ANYWAY while we had the trans out I noticed my exhaust is not an axelback like the guy thought but in fact a Turboxs 3in stainless turboback :eek:
Only mod that we could find, previous owner had no access port put in so should that be the first thing I do?

Can anyone point me to the best suited one?
Thanks!
 
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