[bonomo335i]

So i was looking around and didnt really see any exhaust that i liked especially in 3" if they even make one. Im not trying to brake my bank so i decided to make my own full 3" stainless exhaust. thoughts? any tips?

[Jaronbwall]

Unless you're experienced in building such an exhaust and have the pipe bending equipment, welder, etc it's going to cost a lot. A safe estimate would be around $750-1000. Maybe you can find someone to do it cheaper if you offer to help.

[srey]

What have you already done to your car? With the exception of catless downpipes, exhausts are one of the worst hp/dollar purchases for a 335i. If you already have an intercooler, downpipes, charge pipe, tune, etc., I understand the desire to put an exhaust on it. For the cost of doing a custom exhaust, assuming other go-fast bits have been installed in the engine bay, I'd look at rear subframe bushing and M3 control arms on the front instead.

[TemjinX2]

not really worth it on the small stock turbos unless your upgrading to a bigger turbo or a large top mount turbo. The above mentioned mods will give you more power unless your just going for sound.

[bonomo335i]

lol ive done it all. This would be a easy project for me plus since i sold my 240sx la couple years ago ive been wanted to work on something. I have a hobart tigmate and most the tools i need to finish the project. so im good on that. just going to buy all the parts including downpipes and piece it together then knock it out. and yes i want some sound. tired of the sleeper sound.i priced it all and looks like i can get it done all in stainless with 2 vibrant mufflers and single wall basic tips for around 500$. once i start i will make a thread. it will be after the new year got to replace my wifes motor in her MK6 jetta damn camshaft froze up at 100k pissed me off!

[bonomo335i]

Originally Posted by TemjinX2

not really worth it on the small stock turbos unless your upgrading to a bigger turbo or a large top mount turbo. The above mentioned mods will give you more power unless your just going for sound.

So you think that there wouldnt be a flow restriction from the stock turbos to 3" down pipes to 2.5" exhaust... the faster the air can enter and exit = more powaaaaa

[srey]

Originally Posted by bonomo335i

So you think that there wouldnt be a flow restriction from the stock turbos to 3" down pipes to 2.5" exhaust... the faster the air can enter and exit = more powaaaaa

That's true, if the exhaust is the most restrictive part of the turbo system. The inlets and air box are supposedly (anecdotally, ie I read somewhere) more restrictive than the 2.5" exhaust. Can't fart big if you're breathing through a straw.

[Emilime75]

It's dual 2.5" pipes...not very restrictive even with the common bolt ons and tune. The mufflers, cats, yes, those can be improved on. If you just want a project...go for it, but don't expect much, if any, performance gains.

[TemjinX2]

Originally Posted by bonomo335i

So you think that there wouldnt be a flow restriction from the stock turbos to 3" down pipes to 2.5" exhaust... the faster the air can enter and exit = more powaaaaa

the down pipes are the most restrictive part of the exhaust. The n54 comes with a true duel exhaust, the 2.5inch is more then enough for the stock small turbos.

best bang for your buck will be downpipes, intercooler and tune...all together would still be under $1k and make more power then a custom exhaust.

[srey]

Maybe you could do a single 3.5" exhaust like this kid. I think catless downpipes connecting to a single exhaust with a racing cat midpipe to keep down the smell and drone would be sweet. I really like the way his sounds. Exhaust clip starts around 3:40

[Emilime75]

I think he's running the BMR exhaust, and VRSF also has a single 3.5".

[bonomo335i]

yeah i wouldnt mind doing that it would save alot of time and money lol

[lightmanek]

This is my dual 3'' custom with MG Motorsports muffler and MagnaFlow Sport Cats. Sounds great







Unfortunately, my car is temporarly down due to shoddy repair of Vanos causing catastrophic engine failure, but once it's fixed, I will finally be able to test my new babies!



Too big to fit with proper piping, so there were concessions made in the block, and few other places, but more in my build thread once car is fixed

- this was with hybrid stockers

[Torgus]

3'' single is worse than stock. Stock is 60 mm or about 2.36 inches but dual. You really want a 3.5'' single. The VRSF 3.5'' is the best price on the market. Not sure it's worth the hassle of making your own even if you can...the stock parts + what your time is worth. I would hazard to guess that it will be very hard to fit dual 3'' but it should be possible.

[Bimmer_Engineer]

Originally Posted by Torgus

3'' single is worse than stock. Stock is 60 mm or about 2.36 inches but dual. You really want a 3.5'' single. The VRSF 3.5'' is the best price on the market. Not sure it's worth the hassle of making your own even if you can...the stock parts + what your time is worth. I would hazard to guess that it will be very hard to fit dual 3'' but it should be possible.

The guy in the post before yours has dual 3”...

[lightmanek]

Originally Posted by Bimmer_Engineer

The guy in the post before yours has dual 3”...

Yes

But he is right, it's not easy to fit in. Welding was slow as each section had to be done in stages to manage and minimise weld expansion/bending forces.
My mechanic did it over 4 days while rebuilding other parts of the car, but if someone really tried, probably 2 days would be enough.

BTW this is the same exhaust on stockers but with Vibrant 1792 resonators.

[Supra2k6]

I have a cheap 3'' full exhaust in VA

[Torgus]

Originally Posted by lightmanek

Yes

But he is right, it's not easy to fit in. Welding was slow as each section had to be done in stages to manage and minimise weld expansion/bending forces.
My mechanic did it over 4 days while rebuilding other parts of the car, but if someone really tried, probably 2 days would be enough.

BTW this is the same exhaust on stockers but with Vibrant 1792 resonators.

Were you able to keep the rear V brace? The 3.5 is a tight fit!

It would be neat to see the gains of dual 3" vs s single 3.5". I dont doubt there could be gains. You think there would be a good market if a vendor made a mandrel bent bolt on dual 3" solution.

And yes I saw the above post. Only dual 3" I have ever found online.

[lightmanek]

Originally Posted by Torgus

Were you able to keep the rear V brace? The 3.5 is a tight fit!

It would be neat to see the gains of dual 3" vs s single 3.5". I dont doubt there could be gains. You think there would be a good market if a vendor made a mandrel bent bolt on dual 3" solution.

And yes I saw the above post. Only dual 3" I have ever found online.

Yes, this was kept stock. Exhaust pipes are going lower than the lowest part of the floor, meaning that if I hit especially tall speed hump, my exhaust is the most likely part to catch it ... but it's only sticking out by about 1cm around the rear dif

[Riceball777]

I don’t see the point unless you doing for the sound. The stock cat back exhaust is proven to be good to over 600whp. The stock exhaust show flow more and better than a single 3 inch exhaust. High power 4 cylinder Honda’s and Evo’s all have proven a full 3 inch exhaust is good to over 700whp with no benefits of going to a bigger exhaust at these power levels.

I personally love my stock exhaust with the secondary cats cut out and with cat less down pipes. Work great for my pure stage 2 turbos running E85.

[lightmanek]

Originally Posted by Riceball777

I don’t see the point unless you doing for the sound. The stock cat back exhaust is proven to be good to over 600whp. The stock exhaust show flow more and better than a single 3 inch exhaust. High power 4 cylinder Honda’s and Evo’s all have proven a full 3 inch exhaust is good to over 700whp with no benefits of going to a bigger exhaust at these power levels.

I personally love my stock exhaust with the secondary cats cut out and with cat less down pipes. Work great for my pure stage 2 turbos running E85.

In my case, I went throught almost all variants of stock and modded stock exhaust. You're right, this isn't needed if you have modest power goals.

I have 700WHP goal at some point in the future and did it mainly for sound and because it costed me $1200 in total with muffler and cats.

Benefits are, bolts exactly like stock exhaust, looks and sounds completely different (I'm not saying better as this is personal opinion and I like both exhaust sounds) and provisions for big turbos.