what's the consensus on a fabbing race exhuast 328is plus ebay headers?

[backyardhustler]

1st thread ever hurray!

Just about finished building a 328is for lucky dog that is way way too nice. Need to fab up the exhaust system, all we have to start with is set of ebay headers. From the headers back it seems all the retail race exhausts are single pipe? so single pipe all the way back? The idea is to make the most power and not give up too many ft lbs.
ebay headers to y pipe, then 2.5? 2.75in tube? bimmer world uses 3inch seems gnarly huge? to straight through muffler out the back? testing the car starts in 8 days need to get the ball rolling asap. Exhaust fab scheduled for Tuesday.


Thanks for any input!

Daniel

[tripitz]

I've been investigating this as well. I have a thread in the M3 forum as I was debating the 3" custom vs dual pipe. At least for an S52 application, it seems that 3" single is the way to go. It's going to be lighter than dual pipes and will allow for the least restrictive flow. My local race shop is going to fab up a 3" for me with a custom Y. Not sure which headers you bought; if they are replica euro long tube headers you pretty much have to go custom (the bimmerworld kit only bolts up to stock US headers without adaptation). At that point, go 3 as there are only limited off the shelf options (e.g., SS euro race at $$$$).

[backyardhustler]

Def going custom, ebay headers, 86 bucks lol look nice fit good . Maybe 2.75 for the smaller displacement I'm thinking?

thanks for your input

[JBasham]

FWIW, I believe a single 2.5" would be way more than enough. I run a 240 HP-ish V8 through the stock exhaust (custom header collectors of course, but otherwise it's just the stock 325is E36 exhaust, cats, muffler and all) and I'm not getting any power restrictions from that setup. It's hard to make anything fatter than 2.5" clear the subframe reinforcement brace around the transition from the header collectors to the horizontal underbody exhaust tunnel on the passenger side, and even the 2.5" pipe is fat enough to stick out below the underside of the floor pan more than the ideal situation for a streetable track car.

[backyardhustler]

I mean all the turbo s52 guys run 3inch, and some 3.5. I feel like some of these race exhausts could rob the car of alot of power except at like 6500rpm+ lol. To the point where the car could suck on a tight course or up a hill climb per se. leaning towards 2.5 single after the last post. thx for the opinions the more the merrier, tuesday is coming up quick! I will post my butt analysis once the system is complete.

- - - Updated - - -

not to mention turbo guys are running 500-600+hp out of 3 inch is this not insane on NA?!?

[XXLBIMMER]

exhaust side.jpgexhaust top.jpg3 inch out the side. Just roughed in for now.

[aeronaut]

Ya know, when you cut the floor pan out to fit an exhaust, it's definately cause RACE CAR!
Wow!

[backyardhustler]

savage! have you tested this setup before or is this the first one?

[JBasham]

exhaust side.jpgexhaust top.jpg3 inch out the side. Just roughed in for now.

Dayum. Humbling.

[jakermac]

That'll be f-ing loud!!

I have a set of the Raceland shorties with a custom 2-1 merge into a 3" Vband that is currently wrapped with header wrap for sale. $200 plus shipping from Blaine, Wa 98230.

1st 3 pics are from the fabrication process. Built following Burns Stainless' direction and using one of their transitions.







Bottom one. I can take off the wrap for a prospective buyer if needed.

Header 1

[backyardhustler]

So no comments on real life experience so I'll post mine. While not totally related a lot of kids are bringing their e36's to my shop with the addition of some exhuast. Driven a few straight pipe 2in doubles. They ran like shit big power loss in the low to mid, being respectful I didn't wrap them out no comment on the top end. I can also tell you straight out the headers with no exhuast the car doesn't seem to be happy at all.
Super rumbly and stumbling. Hunting for a clean idle.

So if no one has real life experience I'm going to guess and give it my best guess. Currently leaning toward 2.5 single for the ebay headers. 1.5 days until exhuast fab.

[eye145]

I just put a single 2.5" set up with a Vibrant center resonator and muffler on a s50 swapped e30. It sounded awesome and seems to flow good. On my n/a s52 time trial car I ran a 3 inch single set up with borla resonator and Hushpower muffler made 270hp at the rear wheels. I like to use band clamps (Dynomax 33229 Stainless Steel Strap Band Clamp Butt Joint) to hold y pipe to the header then a single band clamp in the middle to make it easier to service later.

[backyardhustler]

That's what I'm talking about! Thank you. Another point for 2.5 single on the 328. Those are good numbers on your s52.
How's the midrange power on the 3inch single s52?

[jakermac]

Here's the last dyno from my built 3.0 84x89.6 motor using a single 3" exhaust with the headers/collector/merge I posted above:

[XXLBIMMER]

savage! have you tested this setup before or is this the first one?

This is the first one. The engine will eventually be a solid lifter high rpm screamer. Right now it's a 2.5 with M3 cams, so revs will be slightly limited.

[CoMZ302]

None of the race cars I run with use anything smaller than 3" but of course I don't know who has experimented and who hasn't. Testing is expensive (after all that's why we're on here asking questions instead of paying to know for certain). Mostly people copy cat the fast guys - and most of the fast guys are drivers who just put on whatever they're told. It's like a vicious cycle man.

I have a 2.8 race motor in my 328 (285whp/245tq) - I'm using the AA complete system, which I'm pretty sure is 3" all the way back. 3.91 FD with 25.4" OD tires.

While I have really good power for a 328, I find my fastest lap times are when I'm not shifting the hell out of the thing and instead, letting the torque do the work. Depends on the track, but pretty much second is a total joke and waste of time - even though I'm making way less power in 3rd and I thought shifting down to 2nd would help.

Some people run the Turner Shorties, which are supposed to make more torque (and less top end) than what I have. I am starting to think giving up 10hp and getting back 10tq would be faster. I'll probably try that next year.

[XXLBIMMER]

CoMZ302 nice truck!20170624_130520.jpg
and good taste in racecar!

[backyardhustler]

Thank you everyone for your input! CoMz302, This is around the lines of my thinking, especially running endurance races (24hr)I might stay off the rev limiter a few hundred rpm with the intent of holding this bitch together. Extra torque would be beneficial! All though I am very impressed with every ones numbers on a fat 3 inch single!

[eye145]

s54 vs s52 dyno.jpg Here is my built s52 vs some what stock s54 (epic tune and power pulleys). Both dynoed in the same car using the same trans,clutch, diff and wheels and the same exhaust with the exception of the headers. Both sets of headers were ebay super sprint replicas. Exhaust was my custom built y pipe into 3" / borla res. to hushpower muffler. The s54 is the 330hp plot

[Cobra1956]

Dont forget to factor in anywhere you run that has noise restrictions. Would suck to fab something you can't run

[badmonkey]

s54 vs s52 dyno.jpg Here is my built s52 vs some what stock s54 (epic tune and power pulleys). Both dynoed in the same car using the same trans,clutch, diff and wheels and the same exhaust with the exception of the headers. Both sets of headers were ebay super sprint replicas. Exhaust was my custom built y pipe into 3" / borla res. to hushpower muffler. The s54 is the 330hp plot

That's a strong S54 argument.

[NeilM]

That's a strong S54 argument.

My very thought.
(Wish I hadn't looked!)

Neil

[XnWarden]

exhaust side.jpgexhaust top.jpg3 inch out the side. Just roughed in for now.

Looks like a Borla xr1 muffler. I'm currently running it, am very impressed