[54VAGE]

Hey guys, currently looking for downpipes for my N54 E92 335i. I currently have the PE exhaust on it. I was wondering if any modification is required to fit 3" DP or if both sizes will bolt right on regardless of diameter.
Also, is there much difference in performance/sound for a 3 inch vs 2.5 inch downpipe?
Thanks

[Flex68]

Stock turbines ???

[Stucks]

3 inch downpipes bolt right up no problem. negligible difference between 2.5 and 3 inch downpipes. maybe a couple whp.

[shadow191]

3" downpipes all neck down to 2.5" where they meet the exhaust. If you look at the pics, you can see it. So they all fit just fine.

[fmoua916]

Should fit fine.

[Tiago@VRSF]

Quality 3" downpipes will fit perfectly

[Jeff@TopGearSolutions]

All the 3" taper to 2.5" to mate with stock exhaust. Most popular ones like VRSF have a good amount of a 3" before it tapers, so that's good.

[Mike@N54Tuning.com]

Originally Posted by Rashman94

Hey guys, currently looking for downpipes for my N54 E92 335i. I currently have the PE exhaust on it. I was wondering if any modification is required to fit 3" DP or if both sizes will bolt right on regardless of diameter.
Also, is there much difference in performance/sound for a 3 inch vs 2.5 inch downpipe?
Thanks

Many years ago there were several 2.5" full downpipes on the market, but now most are full 3" and taper down to 2.5" at the end.

Here is a pic of the taper on the N54 Performance Line downpipes so you can see what we are talking about. The key to a good design is a smooth taper.

[54VAGE]

Alright guys officially got 3" downpipes from ARM motor sports. For less than $200 new I couldn't go wrong. Taper wasn't bad. Fitment was perfect. And got the part in like two days. Sounds great and car kicks and growls much nicer now.

Might potentially delete secondary cat from my PE exhaust but I fear the rasp so I'll wait until I get bored of this first

[autoart]

I wonder who makes it? I just went on their website. $197. for downpipes.

[Varjo]

are there any good catted downpipes that don't break the bank? I don't like the idea of running catless.

[bradsm87]

Originally Posted by Varjo

are there any good catted downpipes that don't break the bank? I don't like the idea of running catless.

There really is no performance advantage in doing so. The modern factory cats aren't too bad and FrankenTurbo recently proved that even 3" catless downpipes only save 2psi back pressure on an 18psi tune and don't noticable change power or WGDC. Aftermarket catted downpipes would be lucky to get half again of that small gain. Aftermarket cats are terrible for emissions anyway.

[Give_Em_The_DD]

Originally Posted by Varjo

are there any good catted downpipes that don't break the bank? I don't like the idea of running catless.

If you feel u need catted- CPE makes a nice product. I ran those for a year and half no issues. Sold them to a buddy, he's ran them for an additional 11 months, also 0 issues.

[Varjo]

ok, well thanks for the advice guys. What's the best first thing to upgrade, aside from fmic, if I'm bone stock? I'd love to run stage 2-fmic on MHD.

[Icarium]

Originally Posted by bradsm87

There really is no performance advantage in doing so. The modern factory cats aren't too bad and FrankenTurbo recently proved that even 3" catless downpipes only save 2psi back pressure on an 18psi tune and don't noticable change power or WGDC. Aftermarket catted downpipes would be lucky to get half again of that small gain. Aftermarket cats are terrible for emissions anyway.

So with what the results FrankenTurbo showed, catless DP's are not worth it unless you're planning on pushing past 18psi? Don't most DP manufacturers show some dyno's saying 25-30hp increase?

[Two Snails]

Originally Posted by Icarium

So with the results FrankenTurbo showed, catless DP's are not worth it unless you're planning on pushing past 18psi? Don't most DP manufacturers show some dyno's saying 25-30hp increase?

I saw that too and I'm just intake-downpipes+tune and saw a change when adding downpipes. I really should get a charge pipe and BoV soon though. I'm on borrowed time with a 09

[bradsm87]

Originally Posted by Icarium

So with what the results FrankenTurbo showed, catless DP's are not worth it unless you're planning on pushing past 18psi? Don't most DP manufacturers show some dyno's saying 25-30hp increase?

I still think downpipes are best first mod myself. They do reduce back pressure a little which does help reliability etc. They should make a little more power for same boost.

[Tiago@VRSF]

The added power is incredibly noticeable between catted and catless. Before the DP fixes were available we used to swap downpipes for emissions and there is a night and day difference between the two.

[c131frdave]

So which is it, guys? lol I just bought my 335i a couple days ago and am looking for a first mod (with tune, of course). To me, as an aerospace engineer and current gas turbine power plant supervisor, going from 2.5 to 3 to 2.5 would hurt performance, not help it. Basic laws of pressure dynamics says the larger volume actually increases pressure in that space (and lowers velocity), and then you give yourself a choke point when you go back to 2.5, though I suspect the penalty of having the 3" would be negligible. Having not studied the issue at all, on face value you'd be better off going 2.5 the whole way back, or 3 the whole way back. You could go from 2.5 to 24", but as long as you are going back to 2.5, it would make no difference. I know because we do it every single day at work on a MUCH larger scale. With consistent pipe diameters you would avoid aerodynamic issues such as pressure surging, chokes, and turbulence. But then again, we're talking very small percentages I would imagine...

Anyway, nerd mode over; so is adding a downpipe a good first mod or not? lol

[bradsm87]

Originally Posted by c131frdave

So which is it, guys? lol I just bought my 335i a couple days ago and am looking for a first mod (with tune, of course). To me, as an aerospace engineer and current gas turbine power plant supervisor, going from 2.5 to 3 to 2.5 would hurt performance, not help it. Basic laws of pressure dynamics says the larger volume actually increases pressure in that space (and lowers velocity), and then you give yourself a choke point when you go back to 2.5, though I suspect the penalty of having the 3" would be negligible. Having not studied the issue at all, on face value you'd be better off going 2.5 the whole way back, or 3 the whole way back. You could go from 2.5 to 24", but as long as you are going back to 2.5, it would make no difference. I know because we do it every single day at work on a MUCH larger scale. With consistent pipe diameters you would avoid aerodynamic issues such as pressure surging, chokes, and turbulence. But then again, we're talking very small percentages I would imagine...

Anyway, nerd mode over; so is adding a downpipe a good first mod or not? lol

Agreed. 3" is overkill. Wagner Tuning downpipes are 2.75" and have flex sections. I've been very happy with mine.

I would do downpipes for the slightly less back pressure alone, regardless of gains.