[bradsm87]

What is the best downpipe for 535i?

I want one with mounts and a flex section.

ER, AR Design or another option I don't know about?

AR Design looks to have a little more gradual diameter transitions which I like.

Anyone have any experience with these two downpipes?

[harris69]

I am interested in knowing that as well. I am contemplating on getting the VRSF downpipe and chargepipe as they are running a sale right now but I'd like to know which downpipe has the best craftsmanship, and gains for N55s.

[5soko]

Oem downpipe gutted..

Perfect fit, all the mounts, flex section..

[BuiltnBoostedZ]

Originally Posted by 5soko

Oem downpipe gutted..

Perfect fit, all the mounts, flex section..

If you like huffing gas, yea.

[5soko]

Originally Posted by BuiltnBoostedZ

If you like huffing gas, yea.

Originally Posted by BuiltnBoostedZ

If you like huffing gas, yea.

Not sure what you are referring to? All downpipes do the same thing, remove the cat for less restriction.

[MPOSTER!]

Originally Posted by 5soko

Not sure what you are referring to? All downpipes do the same thing, remove the cat for less restriction.

Unless of course you buy a catted down pipe

[5soko]

Originally Posted by MPOSTER!

Unless of course you buy a catted down pipe

Which brings us back to square one lol

[MPOSTER!]

Originally Posted by 5soko

Which brings us back to square one lol

There are still gains to be had with a catted down pipe. Just like I'm sure there are gains to be had with an aftermarket catless down pipe vs a gutted stock down pipe.

If a catted down pipe didn't net any gains, then no one would sell them and no one would buy them.

If a gutted OEM down pipe netted the most gains, then no one would make or buy an aftermarket one.

Not everyone wants a catless down pipe, either because they don't want it to be too loud, they have to pass emissions in their state or they don't want the exhaust to smell.

[5soko]

The Gains with a catted downpipe isnt worth the Expensive price tags associated with them and labor costs just to install it.. This side of the market, states, and nose sensitivity is better off staying with the oem downpipe for dollar per hp.

A gutted vs aftermarket downpipe yield absolutely the same gains, ask me how i know Remember, turbo engine not NA.

Most people just go for an aftermarket downpipe because they dont want to ruin their stock oem downpipe and cat.. Also dont have the time to gut them or send it out to get gutted with downtime on their car.
But most aftermarket downpipes don't even simple correct mounts, or even a flex section. On top of most of them having bad fitment..

[bradsm87]

I'm not a fan of a sudden step to 6" and back down to 2.75" of a gutted stock downpipe. I've also heard too many gutted cats that make weird noises without having a straight pipe welded into them.

Maybe VRSF and weld a mounting tab to it might be the go? I'm not a fan at all of not running mounts. I don't want the turbo being yanked around and fatiguing from the exhaust.

[Charter23]

Originally Posted by MPOSTER!

If a catted down pipe didn't net any gains, then no one would sell them and no one would buy them.

If a gutted OEM down pipe netted the most gains, then no one would make or buy an aftermarket one.

You are saying that companies won't make, market & sell something unless it actually works? In what world?

The butt-dyno has been making the aftermarket industry profits since the model-t.

[Charter23]

Originally Posted by bradsm87

I'm not a fan of a sudden step to 6" and back down to 2.75" of a gutted stock downpipe. I've also heard too many gutted cats that make weird noises without having a straight pipe welded into them.

Maybe VRSF and weld a mounting tab to it might be the go? I'm not a fan at all of not running mounts. I don't want the turbo being yanked around and fatiguing from the exhaust.

Search "gutted downpipe" in any forum category but the 5 series and you will find countless examples of people loving their gutted OEM downpipes. This is not to say that aftermarket downpipes are bad btw. I just don't get why people hate on gutting OEM.

After reading up on gutted DPs in the M5 forum I am convinced they are a great way to go. Double walled, perfect fitment, reportedly not as loud as aftermarket. Oh and they are free (today anyway).

[Dollar Bill 535]

Both of my ER's have been great to me. Their F10 N55 DP and CP are top-notch.

[BuiltnBoostedZ]

Originally Posted by 5soko

Not sure what you are referring to? All downpipes do the same thing, remove the cat for less restriction.

What makes more power? 2.5" downpipe or a 4"? I gutted an oem downpipe once. I was 16. I've built plenty of race cars since then and haven't done dumb sh*t like that in over 25 years.

[MPOSTER!]

Originally Posted by Charter23

You are saying that companies won't make, market & sell something unless it actually works? In what world?

The butt-dyno has been making the aftermarket industry profits since the model-t.

No that is not what I am saying. If there were no gains to be had with a catted down pipe, then every time someone brought up wanting to buy they would get instantly flamed with everyone tell them they do not work. Were not talking about the airraid throttle body spacer here...

[Charter23]

Originally Posted by MPOSTER!

Were not talking about the airraid throttle body spacer here...

Lol, so true!

[5soko]

Here is a quick video i took of a friends OEM Catless Downpipe we just had finished.

A few key points in the video i was trying to show.

-The flange to the turbo, there is a small lip, the turbo actually has a round metal gasket that sits in a groove on the turbo, it receives this lip on the downpipe to create a seal..
If this lip is too tall or too wide, like i have seen on many aftermarket downpipes, it creates for fitment issues and leaks.

- The actuall flange. Once the downpipe is mounted to the turbo, the flange on the DP gets locked on using a clamp. Every wonder why some aftermarket downpipes are so hard to get the clamp to install on. Flange isnt a perfect fit which causes a headache to install the clamp correctly.

IMHO, the quality of the oem DP is great of course. Has the mounts, flex section, perfect fit flange, makes great power and lets our turbo free flow.
Remember, turbo cars like reduction of back pressure. Our small snails dont push enough air or psi to really warrant anything over the top like a 1,000whp build with 30-40 psi. Our small snails don't make much power, so anything we can do to help them is great.

In this case, we cut open the DP on 3 sides, opened up like a door, removed the cat, welded her back up, grinded down the welds, cleaned her up, and a finished product.

[harris69]

Are you selling these?

[Charter23]

Originally Posted by 5soko

Here is a quick video i took of a friends OEM Catless Downpipe we just had finished.

A few key points in the video i was trying to show.

-The flange to the turbo, there is a small lip, the turbo actually has a round metal gasket that sits in a groove on the turbo, it receives this lip on the downpipe to create a seal..
If this lip is too tall or too wide, like i have seen on many aftermarket downpipes, it creates for fitment issues and leaks.

- The actuall flange. Once the downpipe is mounted to the turbo, the flange on the DP gets locked on using a clamp. Every wonder why some aftermarket downpipes are so hard to get the clamp to install on. Flange isnt a perfect fit which causes a headache to install the clamp correctly.

IMHO, the quality of the oem DP is great of course. Has the mounts, flex section, perfect fit flange, makes great power and lets our turbo free flow.
Remember, turbo cars like reduction of back pressure. Our small snails dont push enough air or psi to really warrant anything over the top like a 1,000whp build with 30-40 psi. Our small snails don't make much power, so anything we can do to help them is great.

In this case, we cut open the DP on 3 sides, opened up like a door, removed the cat, welded her back up, grinded down the welds, cleaned her up, and a finished product.

Love this

[bradsm87]

Just get a big spade bit on a drill and attack the internals until it all falls out. Saves cutting and welding.

I personally still think the big open chamber but each to their own.

[5soko]

Originally Posted by harris69

Are you selling these?

no no, this is something everyone can do at home (cutting open the DP and removing the cat) and or at a shop for the welding part.

I did mine, brought it to a shop to get welded. We did the same for my good friends.

We bought the oem downpipes on ebay for $300 or so shipped, the gutting and welding was cheap..

Originally Posted by Charter23

Love this

Simple and it works.

Originally Posted by bradsm87

Just get a big spade bit on a drill and attack the internals until it all falls out. Saves cutting and welding.

I personally still think the big open chamber but each to their own.

I started that way, but i wanted to really clean things up on the walls, so i ended up cutting it open. But you can absolutely do it that way and use a wire brush bit to clean it up.
At 12-15psi of what most modded N55's run here, not nearly enough psi to be worth thinking over and talking exhaust flow dynamics.

[Charter23]

Originally Posted by 5soko

I started that way, but i wanted to really clean things up on the walls, so i ended up cutting it open. But you can absolutely do it that way and use a wire brush bit to clean it up.
At 12-15psi of what most modded N55's run here, not nearly enough psi to be worth thinking over and talking exhaust flow dynamics.

How does it sound? I want to do this but don't want it too loud.

It might be stupid but I was thinking of carefully drilling a single hole clean through the cat with a 2" hole saw bit. If it didn't compromise the integrity of the cat medium too much, I'd be interested to see how that sounded. Maybe it would even pass smog?

I have zero experience with that matrix as a material so this is probably a pipe dream (pun intended).