Official Lowered Outback Thread V2

[MTBwrench]

There was no difference to me with a catted downpipe and a stock catback. A resonated 3" mid-pipe made hardly any difference at all too... but as soon as I changed the mufflers, dear Jesus was it loud. Since I have yet to find a good medium between the two, I have nameless deletes that are on there 90% of the time, and stock muffs get swapped back on for road trips.

[Flinkly]

just to round out the exhaust discussion, a famous exhaust dude (granted, worked on V8's most of the time) stated that:

 

- A pipe flows 115 CFM per square inch of cross sectional area

- You need 2.2 CFM of flow capacity per HP

 

(this is probably not based in science, more likely experience...)

 

So for 350hp, you need ~3" exhaust.

 

It does make me wonder what you actually need, in a science/data way...

[funkycharms]

Any of you just do a downpipe? How much that that change the sound? I loved the sound of my Cobb on my WRX, but I keep hearing horror stories about the exhausts on our wagons........ combined with dealing with the turn downs.

 

I love Rhitters comment "They are easy enough to take on and off though and a I keep doing that." I really need to leave NY. I have never done an exhaust job that didn't involve cutting.

 

I currently have a catted downpipe and stock catback.

 

I barely notice a difference on idle/Everyday driving, car still sounds stock to me. I do notice a slight difference at WOT, but that can be because car is pushing more power to the ground.

 

I know a muffler upgrade will sound good, but in the end I enjoy stock sound with extra power.

[housemusic1]

just to round out the exhaust discussion, a famous exhaust dude (granted, worked on V8's most of the time) stated that:

 

- A pipe flows 115 CFM per square inch of cross sectional area

- You need 2.2 CFM of flow capacity per HP

 

(this is probably not based in science, more likely experience...)

 

So for 350hp, you need ~3" exhaust.

 

It does make me wonder what you actually need, in a science/data way...

 

Interesting. If that theory holds true, you would think that the stock 350hp cars, i.e. BMW M's, Audi S's, etc, would roll of the assembly line with 3" exhaust.....maybe they already do? (I'm not a BMW or Audi guy), so I don't know. I haven't heard that theory before, but it kinda makes sense.

[Daniels]

I’m running fathouse fab el headers to ultimate racing EWG recirc up pipe, ultimate racing down pipe no cats, nameless mid, nameless 5”

[Rhitter]

I’m running fathouse fab el headers to ultimate racing EWG recirc up pipe, ultimate racing down pipe no cats, nameless mid, nameless 5”

 

And......your exhaust sounds good? Sounds bad? To much drone? Unrelated non sequitur?

[lilredwagon]

I've heard the "350hp requires 3" pipes" theory before. The thing is that it gets confusing when you have multiple pipes. Like the question about cars that come stock with 350hp, my guess is that they run dual pipes all the way back with a crossover pipe of some kind. So with dual pipes, do you just add the diameters of the multiple pipes? So two, 2.5" pipes would be roughly equivalent to a single 5" pipe? In our case, if we have a 2.5" pipe that splits to two 2.25" pipes at the end, but with very restrictive mufflers on it, then what would that equate to?

[Flinkly]

I've heard the "350hp requires 3" pipes" theory before. The thing is that it gets confusing when you have multiple pipes. Like the question about cars that come stock with 350hp' date=' my guess is that they run dual pipes all the way back with a crossover pipe of some kind. So with dual pipes, do you just add the diameters of the multiple pipes? So two, 2.5" pipes would be roughly equivalent to a single 5" pipe? In our case, if we have a 2.5" pipe that splits to two 2.25" pipes at the end, but with very restrictive mufflers on it, then what would that equate to?[/quote']

 

Just to "answer" the easy stuff in your post, given that most of us are Turbo'd (and/or H4), it's just one pipe unless you don't care about any of this and think having two pipes to the back is cool.

 

The other issue is that most "knowledge" comes from V8's, which by design is quite the different beast. which is where dual pipes to the rear with X or H pipes doing a crossover comes from.

 

i did also find what you are asking about, but since it is moot for me, i didn't bookmark it for later. i might be able to scare it back up (a "conversion" from single 3" to dual X.XX" inch pipes).

 

 

And honestly, at the end of the day you can make 350hp with a 2" pipe, or 4" pipe, or whatever, but the tribal knowledge helps you to get closer to an optimum size without doing CFD analysis and choosing a small RPM band that you want to optimize for. and then for what are you optimizing? sound? MPG? HP? Tq?

 

 

 

(...although none of this is really related to the thread title...)

Edited April 11, 2018 by Flinkly

[WRX USA]

I've heard the "350hp requires 3" pipes" theory before. The thing is that it gets confusing when you have multiple pipes. Like the question about cars that come stock with 350hp' date=' my guess is that they run dual pipes all the way back with a crossover pipe of some kind. So with dual pipes, do you just add the diameters of the multiple pipes? So two, 2.5" pipes would be roughly equivalent to a single 5" pipe? In our case, if we have a 2.5" pipe that splits to two 2.25" pipes at the end, but with very restrictive mufflers on it, then what would that equate to?[/quote']

 

You’d need to use Pi R^2 to compare different size pipes (given they have same length). So 2 2.5” pipes would be equivalent to 1 3.5” pipe.

[Flinkly]

You’d need to use Pi R^2 to compare different size pipes (given they have same length). So 2 2.5” pipes would be equivalent to 1 3.5” pipe.

 

this is where the "knowledge" begins to break down though (not that it was ever based in fact anyways... ).

 

While 2x 2.5" pipes are only ~2% larger cross sectional area than a single 3.5" pipe, the drag on the flow from the tube walls is (approximately; comparison of total circumference) 43% higher. If you really wanted to get to the same "performance" as a single 3.5", you'd need to go larger.

 

In simple terms, the engine is going to have to push harder to get the exhaust out the tailpipe(s) with 2x 2.5" pipes than 1x 3.5" pipes, which is lost performance. This idea is also why we use round pipes and keep it as straight as possible.

 

might be one of the reasons that Subaru did 2.5" pipe split into 2x 2.25" pipes and not 2x 1.75" pipes.

[ADIKT]

So much chatter and no pics. I'll fix that.

 

Here is my shitty race car getting moved ft. my lowered outback

 

 

[Daniels]

And......your exhaust sounds good? Sounds bad? To much drone? Unrelated non sequitur?

 

Yes

No

No

I don’t know

[Rhitter]

Early morning bike ride

[MTBwrench]

Rhitter your wheels are the only ones I've seen that I like more than mine.

[Flinkly]

Rhitter your wheels are the only ones I've seen that I like more than mine.

 

cause their awesome wheels. super light and good looking. and obviously comes in a reasonable fitment.

[Rhitter]

cause their awesome wheels. super light and good looking. and obviously comes in a reasonable fitment.

 

Correction: unreasonable fitment. 18x9 et 40 255/40/18. With substantial fender work to get them to not rub. Rears needed a 5mm spacer to not rub the inner fender liner.

 

I think 18x8.5 et 40 245/40/18 would have fit with little drama.

[MTBwrench]

cause their awesome wheels. super light and good looking. and obviously comes in a reasonable fitment.

 

Precisely why I bought the OZ's. Looks good, light(ish... they're not $600 wheels), I can run a 245/40/18 with a flat alignment, and I can make it around a track without slicing my sidewalls. Function> form.

 

Correction: unreasonable fitment. 18x9 et 40 255/40/18. With substantial fender work to get them to not rub. Rears needed a 5mm spacer to not rub the inner fender liner.

 

I think 18x8.5 et 40 245/40/18 would have fit with little drama.

 

But you have 255s... I can't imagine how much lateral grip that would produce with the right setup. I can take one of those "cloverleaf" on ramps we have all over here in Chicago at almost 70 on a dry day with my current setup. I bet with 255's on a wider wheel(aka stiffer sidewalls) it would be super confidence inspiring. (Also that 40 offset looks super cool)

[Rhitter]

Pretty sure if I tried that I would find all sorts of new rub. Hoping for a track day this year. So will see what I can get to stop rubbing before then.

[lilredwagon]

[funkycharms]

Pretty sure if I tried that I would find all sorts of new rub. Hoping for a track day this year. So will see what I can get to stop rubbing before then.

 

Ditto, I'm looking to head back out at least twice before the end of the year. Probably not in the outback though, I recently bought a 1999 prelude to goof around in. I can keep you updated with our schedule, I have a group of friends who track regularly.

 

Is your car ready now? When do you plan to attend?

[funkycharms]

Looks good! What is your setup? any rubbing issues?

 

[Daniels]

Early morning bike ride

 

 

Where do you ride in the bay? My wife got 3rd in the Lake Sonoma 50Mi ultra trail run this weekend and while I was crewing her i couldnt help to think that there are a bunch of hidden DH tracks around the lake.

Edited April 17, 2018 by Daniels

[Rhitter]

I don't know this area for hidden dh at all. I was at Crockett hills which is all xc. My hidden dh has all been done at Tahoe. I periodically see people disappearing into the woods in DH gear all around the bay area but because of the poison oak I haven't really had a desire to follow them.

 

Santa Cruz supposedly has some of the best hidden trails in the world though.

[lilredwagon]

Looks good! What is your setup? any rubbing issues?

 

Thanks! No rubbing issues - I'm still on stock wheels/tires.

 

Details of my setup are here (JDM LGT Bilsteins):

http://legacygt.com/forums/showthread.php/2008-outback-xt-big-louise-268872.html

[GTB Limited]

Trailer electrics check.