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Old 10-30-2016, 08:59 PM   #1
Varinn
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S52 exhaust

I've been down this road a few times before. I'm looking to build an exhaust for hopefully the last time on my S52 e30.

What is the ideal size for a stock motor with m50 manifold? I'll be upgrading to Schrick 256/264 cams and either Jenvey ITB's or an Eaton M90 in the next year.

Thinking to install raceland longtube headers (I know they are hard to fit, but I've seen the issues and know how to deal with it), dual 2.25" merged to a single 2.75" at the first muffler and carrying that size through to the back. Mufflers would be a 2.75" single vibrant/magnaflow and a 3" vibrant streetpower with dual 3.5" outlets at the very back. The car is going to be turned into a street legal trackday car so I'm aiming to maximize power throughout the range while keeping noise down below our 90dB limit.

Layout wise would look similar to this but with a second muffler in the stock e30 cat location to keep noise down.

I'm a fairly competent tig welder with stainless and have plans to buy mandrel bends to cut and make them fit as nice as possible.

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Old 01-20-2017, 07:44 AM   #2
Sh3rpak!ng
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Well, ideal size for a stock motor and ideal size for cammed and supercharged motor are two very different things... You can find some calculators online that will give you exhaust diameter based on your power goals. My e36 328 used to be supercharged and I recall that I was targeting 350-400 hp which matched to a dual 2.25" system. For a stockish s52 2.5" is the right size. Another thing to consider is that for a NA motor, header design ie primary runner size/length/collector size/shape, secondary runner size/length/collector size/shape and x/y merge placement are the critical parameters. But for a supercharged motor, you just basically want headers that won't hinder flow.

Regarding the raceland headers, I had them on my e36 and after going through the installation etc. I won't buy or use them again. They are just so thin, brittle, really roughly finished. It was not satisfying installing them.

Coincidentally I am in a similar situation as you with an exhaust project. I am in the midst of transforming the car from a street car that does a little autox/track to a "racecar" that does a little street time. Currently I have obd2 headers, magnaflow center muffler and vibrant streetpower muffler at the back. This combo has been fantastic. Not too loud, no drone and sounds mean on throttle. For the new setup I looked around for a long time until I found a set of euro s50b32 headers. You can actually find them and buy them pretty easily on some of the european ebay pages but they tend to be a bit pricey. But then again supersprint headers are quite a bit more expensive and the euro headers are about as good as it gets. Likely I will pair the euro headers with a tuned y merge into 3" with a muffler in the center like before going out back and splitting to a UUC RSC36 exhaust I had on my e36.

Hope this helps
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Old 01-25-2017, 11:41 AM   #3
Varinn
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I haven't been checking in here much recently, that's quite the response/build thread. I'm going to need some time to read through that. I most likely will not end up supercharging my car as goals and realistic life budgets don't always jive as well as I would like.

Part of me is debating keeping the back half of my existing 2.5" system and remaking the front portion that I'm not as happy with. A better set of headers/manifolds, Y-merge, and center resonator setup would likely make a world of difference, the back end is otherwise fairly well built.

Big reasons for wanting to go bigger were to make room for top end gains in track use when I go with a better intake, manifold, and cams. Annoyingly 2.75" seems to be missing from pretty much all aftermarket catalogs. My current setup keeps blowing out gaskets on the front OBD2 flange where it meets the downpipe. I'm looking at it like the lack of flex pipe in my design is stressing the downpipes where they expand and contract through heat cycles and pulling the flange apart.

I was thinking if I kept the modifications to the racelands minimal and focus on the subframe and swaybar mounting I might be able to use them as a temporary stopgap until the budget lets me squeak in a set of euro longtubes. From pictures I've seen of the two I was thinking they should be a direct swap, or damn close to it. I plan on using flex pipes after the first flange post-header to allow for a little flex.
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Old 02-10-2017, 10:23 AM   #4
Sh3rpak!ng
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That's weird you're blowing out gaskets. I never had that issue and didn't have a flex pipe on the exhaust for about a year initially. Almost sounds like the flanges aren't sitting totally flush. Even now the flex pipe on mine is after the y merge to 2.5 so it wouldn't do much to relieve tension on the down pipes.

As a budget setup, you could use the racelands and chop the flanges off a few inches from the 3-1 merge, from there weld vbands and make the approach to the y merge custom to fit around the subframe/swaybar/FCABs. This is the approach I will take when installing my euro headers.

I wouldn't plan on being able to do a direct swap euro headers for raceland down the road. The euro headers will fit perfectly, the racelands will not and inevitably will need coercion to get them to work which like most likely mean they won't be sitting exactly how the euro headers would. I certainly don't trust the chinese to accurately replicate the euro flanges/mounting or even reliably reproduce their own headers identically part to part.
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