1M has high flow cats in downpipe???

[cbl117]

Originally Posted by HP Autosport

If you can find them cheap. You will likely gain about 10 hp by the switch. The alternative is just to save the money and put it towards a cat-back exhaust, intake of a proper software flash for the car.

Have all the mods that you list. The 1M DPs would be an afterthought if I can land a set cheap. If someone wants to donate a set I will front the dyno costs in the name of data.

[SpencerMH]

So I'm currently fob including n55 mids and with 46k miles, I have cat less downpipes sitting here to go in after my last service stop. I was planning carless dp's and put the catted n54 midpipes back in to have minimal smell and more performance than my current setup, how much better is catless dp's with catted mids than catted high flow 1m dp's and catless mids? Is it still a huge improvement like other n54's?

[Artemis]

Considered it worthwhile to repost in this thread the two following comments of forum fellow serial`.
(source: http://www.1addicts.com/forums/showthread.php?t=961330)

Originally Posted by serial`

For sure [the difference] is noticeable, and mine already had 1 cat blown just previous to installation so it was already louder.
I never got all the hate/strongly divided opinions towards DP's on 1M's on this forum, it made no sense at all from what I was taught and had experience with on other cars.
I'll do you one better than just another opinion and post pre and post catless DP video's later this week.
On a verified fully stock map.
Sounds noticeably louder to both myself and the mechanics that installed it and got to drive it a couple days later.
M mode off is quite a bit more responsive now, M-mode on not so much, except maybe just a tad after fully releasing the gas and then going WOT again.
And 1M downpipes being "high flow"?
Compared to 135i's maybe, but more bends+cats = lots of extra and unwanted resistance at the point where it matters the most... (compared to catless dp's)
Here is how "high flow" they are after 25k miles of heavy use:

View post on imgur.com

Guess you could call that high flow on a budget.

Originally Posted by serial`

Knowing that our cars tend to have difficulty dissipating all the engine heat as is, it is no wonder that the parts closest to where loads of that exits from, suffer the most from all these variables (EGT's anyone??) added up. Not the midpipes or exhaust.
Why anyone with any mechanical knowledge at all would even for a second think to advise against catless dp's on a remap where the extra power is used on track, is beyond my comprehension.
Sorry if I put it a bit bluntly (and simply, I'll admit) but this isn't just an issue of performance gains vs comfort, this is about facing the inherent issues of our cars if we want them to be more than just garage queens, and dealing with them accordingly.

[Asbjorn]

Originally Posted by HP Autosport

If you can find them cheap. You will likely gain about 10 hp by the switch. The alternative is just to save the money and put it towards a cat-back exhaust, intake of a proper software flash for the car.

It actually says here on page 16

http://www.1addicts.com/forums/attac...2&d=1396203865

that the 1-series M coupe uses the same primary cats as a Z4 35is. The reason the part number was changed, it says, was because of a different flange positioning.

BTW the part numbers for the primary cats on the Z4 35is and 35i are the same. So unless the 306hp N54 Z4 uses cats with higher flow compared to the 306hp N54 135i then they are basically the same cats. The N54 335i and N54 335is also use the same primary cats btw.

[Dackelone]

Originally Posted by Asbjorn

It actually says here on page 16

http://www.1addicts.com/forums/attac...2&d=1396203865

that the 1-series M coupe uses the same primary cats as a Z4 35is. The reason the part number was changed, it says, was because of a different flange positioning.

BTW the part numbers for the primary cats on the Z4 35is and 35i are the same. So unless the 306hp N54 Z4 uses cats with higher flow compared to the 306hp N54 135i then they are basically the same cats. The N54 335i and N54 335is also use the same primary cats btw.

It's pretty much common knowledge that the Z4 35is and the 1M's N54 produced ~370 Hp. That's bc ///M did 90% of the tuning for the Z4 thinking it would be sold as a real ///M model... then the BMW board nixed that idea at the very end. That's how we ended up with an "iS" version instead.

I also believe it was(first) Harold at HP Autowerks that said the 1M's main cats(dp's) are free-er flowing than the 135i ones.

Dack

[Asbjorn]

Originally Posted by Dackelone

It's pretty much common knowledge that the Z4 35is and the 1M's N54 produced ~370 Hp. That's bc ///M did 90% of the tuning for the Z4 thinking it would be sold as a real ///M model... then the BMW board nixed that idea at the very end. That's how we ended up with an "iS" version instead.

I also believe it was(first) Harold at HP Autowerks that said the 1M's main cats(dp's) are free-er flowing than the 135i ones.

So whether the N54 "is" engines were under-rated or not is a separate discussion. Fact is that both the 335i and 335is versions of the N54 are tunable to over 370hp with a simple ECU flash. The OEM downpipe cats are not limiting anything here it seems.

How does HP Autowerks know for sure that the 1M's main cats are free-er flowing than the 135i ones? No actual proof was ever provided.

Here are the facts anyway.

• The downpipes on the N54 1M and N54 Z4 35is are the same according to the technical training pdf. The part number was changed compared to the 135i at least for one reason: the flange positioning is different.
• The downpipes on the N54 Z4 35i and 35is uses the same part numbers.
• The downpipes on the N54 335i and 335is also uses the same part numbers.
• The water cooling system and fan was upgraded on the 1M compared the Z4 35is model, and is the same used on the 335is.
• The flywheel was made 11% lighter on the 1M compared to all other N54 models

In conclusion, the N54 engine of the 1-series M coupe may have more in common with the N54 used in the 335is than the one used in the Z4 35is. And both is-cars uses the same down pipe cats as their lower powered non-is versions.

[HP Autosport]

Originally Posted by Dackelone

It's pretty much common knowledge that the Z4 35is and the 1M's N54 produced ~370 Hp. That's bc ///M did 90% of the tuning for the Z4 thinking it would be sold as a real ///M model... then the BMW board nixed that idea at the very end. That's how we ended up with an "iS" version instead.

I also believe it was(first) Harold at HP Autowerks that said the 1M's main cats(dp's) are free-er flowing than the 135i ones.

Dack

Yes, the 1M and maybe as well as all the iS models have high-flow cats.

[bdaddylo]

Originally Posted by Asbjorn;

[*]The downpipes on the N54 335i and 335is also uses the same part numbers.

Yes, I'm confused too as when I searched RealOem, the part numbers were different for the primary cats for a E92 335i (18307553594/5) and E92 335iS (18307587609/10). Both have the same engine, N54B30A. Care to share where you pulled your parts numbers from?

HP Auto concluded that the 1M had freer flowing cats based on the additional power gains achieved by tuning versus the regular N54 found in the 135 and 335i. In other words if everything was the same in the 1M and 335i, when tuned and running the same level of boost both should be putting out close to the same numbers. This wasn't the case and the only thing that would explain this is freer flowing cats. Harold, please correct me if I'm wrong.

I'm using the term freer flowing, because I reserve hi-flow for 200 or 100 CEL cats where you can actually smell the difference is noxious gases emitted.

[MDORPHN]

I weighed the 1M downpipes and 335i downpipes and found the 1M weighed significantly less -- presumably cause of a less dense, higher flowing cat.

Old post somewhere about it.

Neil

[HP Autosport]

Originally Posted by bdaddylo

Yes, I'm confused too as when I searched RealOem, the part numbers were different for the primary cats for a E92 335i (18307553594/5) and E92 335iS (18307587609/10). Both have the same engine, N54B30A. Care to share where you pulled your parts numbers from?

HP Auto concluded that the 1M had freer flowing cats based on the additional power gains achieved by tuning versus the regular N54 found in the 135 and 335i. In other words if everything was the same in the 1M and 335i, when tuned and running the same level of boost both should be putting out close to the same numbers. This wasn't the case and the only thing that would explain this is freer flowing cats. Harold, please correct me if I'm wrong.

I'm using the term freer flowing, because I reserve hi-flow for 200 or 100 CEL cats where you can actually smell the difference is noxious gases emitted.

Yes, we came to that conclusion while working with GIAC on the 1M tune. Installing catless DP didn't net the same gains as we have seen in the past with 135/335 N54. As a matter of fact, the difference between the 1M DP and AR Design 3" carless were only 9-12 horse power on several runs.