[antaskov]

Hey guys,

I am thinking of running with stock dps with stage 2 due to noise and mainly smell. I have single midpipe with secindary cats and OPFs deleted (EU spec) that will remain on the car.

Anybody running mhd stage2 or other stg2 with OEM downpipes ? How long and what is your experience, recommendations?

[Th3Walrus]

High flow downpipes are a requirement for stage 2. If you're concerned about noise/smell, get high flow catted downpipes.

[antaskov]

Originally Posted by Th3Walrus

High flow downpipes are a requirement for stage 2. If you're concerned about noise/smell, get high flow catted downpipes.

True, however i hear a lot of people are running stock as they seem not so restrictive and wanted to get some opinions.
If i manage to sell my non catted DPs this will be the target - 200cel.

[BrockDM]

I agree with Th3Walrus. If the files were intended for stock downpipe use they would mention that. They are much more complex than just stage 2 = more boost and power. The targets are set and managed based on a higher flowing exhaust system. Wastegate duty cycle, EGT's, etc all change when you go from stock to catless/HFC.

[antaskov]

MHD has option to say if you are with stock DPs or not.

[Th3Walrus]

Originally Posted by antaskov

MHD has option to say if you are with stock DPs or not.

That's just the option to turn on/off the CEL suppression for no cats. I doubt they have an option for stock cats specifically for stage 2.

You run the risk of overheating and possibly clogging the stock cats running stage 2.

[3beeps]

"Stage 2" means you have downpipes -- it's not just a "better tune". You're better off with the stage 1 tune on stock downpipes. I highly doubt anyone that is running a "stage 2" tune with stock downpipes is logging their car and checking how its performing.

[who is this noob]

I have a sneaking suspicion that the power delta between an optimized tune on stock downpipe and an optimized tune on aftermarket downpipe is smaller than people are led to believe.

This is why none of the aftermarket pipemakers advertise back-to-back comparisons.

Think about it: if their pipe produced significantly more power than a competitor, wouldn't they be the first to measure it and promote the crap out of it? Wouldn't they do controlled tests to quantify how their pipe out-performs the others? Of course they would. But nobody does that. They just say "Stage 2 requires downpipe."

The big gains come from increasing boost, fuel, etc.

My hypothesis is that there is big profit margin in selling a piece of pipe. And low returns because no warranty, because "off-road only," because illegal.

The result is a bunch of people driving needlessly smelly and noisy* cars.

*I like a good sounding exhaust but, as I learned in the hi-fi world, louder isn't necessarily better.

[a143gsxr]

Originally Posted by antaskov

Hey guys,

I am thinking of running with stock dps with stage 2 due to noise and mainly smell. I have single midpipe with secindary cats and OPFs deleted (EU spec) that will remain on the car.

Anybody running mhd stage2 or other stg2 with OEM downpipes ? How long and what is your experience, recommendations?

I have been running stage 2 JB4 on my 2022 M4CX with MAD single midpipe. The stock cats in the downpipes flow very well and there are tuners out there that say it's perfectly fine to run stage 2 with stock primary cats in place especially with the less restrictive midpipe. I also run the e30 stage 2 map so the M4 is making over 700hp with primary cats in place on that map. Been running for a year on this setup. On my trx the stock cats are limited to about 1000hp due to overheating. Maybe heat is also a consideration in our high horse BMW's.

[Jnat]

I've referenced it before and i will again. Check out the original RK tunes video on Youtube when he originally tuned his/wifes X3M. He states that he was surprised how little power he picked up after changing to kittyless pipes, like 10whp, his words not mine. Many and i mean many of you guys and me have always changed the downpipes for the obvious reasons but on this platform the gains are negligible, it appears. Yes, they will flow better to some degree but what is that degree? Also, look at the BM3 and MHD % difference in power output expected between stages 1&2, virtually nothing. Look at the differences on another platform, much greater. Again, not my opinion i'm just going with the numbers. Many guys are running in the low tens on stock pipes maybe even high 9's. With all of that said, it's fine to change them but from what is being reported for basic stage 1&2 set ups there's not much difference so i wouldn't hesitate.

[mike@x-ph.com]

MHD and BM3 require upgraded downpipes for stage 2.

There is a reason for that; if the downpipes were not necessary, they would not require it.

These kinds of shortcuts are what lead to issues and failures down the road.

[antaskov]

Originally Posted by mike@x-ph.com

MHD and BM3 require upgraded downpipes for stage 2.

There is a reason for that; if the downpipes were not necessary, they would not require it.

These kinds of shortcuts are what lead to issues and failures down the road.

I will do custom tune if i decide to go that way.

[antaskov]

The thinking I have behind is that stock cats and DP will suppress noise much better than high flow catted DP. This is what I discussed with a guy doing my exhaust. The construction of OEM is very different from the 200cel aftermarket from what I understand.
My car is daily and i am not trying to push power as much as possible.
My goal is to get the maximum power possible keeping acceptable comfort and noise levels. So its the balance i want to find.

[95wildtt]

Originally Posted by mike@x-ph.com

MHD and BM3 require upgraded downpipes for stage 2.

There is a reason for that; if the downpipes were not necessary, they would not require it.

These kinds of shortcuts are what lead to issues and failures down the road.

Agree 100%!

Much more to be considered than just the HP increase...
As was stated earlier, exhaust flow could be hampered and would result in overheating issues (not just kittys) further upstream and a that can lead to a number of other issues.

I trust the tuning companies more than anyone, and if they recommend it, I wouldn't cut corners.

[Jnat]

Common guys, i'm reporting the numbers. Below is copy and pasted %'s presented by PTF in ref to their BM3 S58 tune profiles. The output is virtually the same, what else can we surmise with that? Also, any comment on RK saying as such, again his words. I'm not taking the position that the downpipes aren't effective at all i'm saying that on this platform they appear to be not as much of a bottleneck that they have been in the past. Also, many have reported the same, i'm not the only one. I won't post on this again because i'm not trying to start anything, i'm simply reporting what all of us can see and yes i'm aware what stage 2 says about downpipes being req'd. Also note that i've changed the downpipes on all of my turbo cars and ordered most if not all from Mike@XPH who has provided excellent customer service to me in the past. Again, this is what's being reported, i get it, downpipes are recommended but in the case with the S58, apparently it's a little different. I'm good with whatever, no position taken here.

Stage 1 ACN91 octane: 11%HP / 25% TQ
Stage 1 91 octane (95 RON): 17% HP / 28% TQ
Stage 1 93 octane: 21% HP / 31% TQ
Stage 1 E30 octane: 31% HP / 41% TQ
Stage 2 ACN91 octane: 13%HP / 28% TQ
Stage 2 91 octane: 20% HP / 30% TQ
Stage 2 93 octane: 23% HP / 34% TQ
Stage 2 E30 octane: 33% HP / 44% TQ
Stage 2 Race Gas: 33% HP / 44% TQ
Stage 2 E50 octane: 37% HP / 46% TQ

[mike@x-ph.com]

Originally Posted by Jnat

Common guys, i'm reporting the numbers. Below is copy and pasted %'s presented by PTF in ref to their BM3 S58 tune profiles. The output is virtually the same, what else can we do with that? I'm not taking the position that the downpipes aren't effective at all i'm saying that on this platform they appear to be not as much of a bottleneck that they have been in the past. Also, many have reported the same, i'm not the only one. I won't post on this again because i'm not trying to start anything, i'm simply reporting what all of us can see and yes i'm aware what stage 2 says about downpipes being req'd. Also note that i've changed the downpipes on all of my turbo cars and ordered most if not all from Mike@XPH who has provided excellent customer service to me in the past.

Thank you for the kind words

It’s not just about the power; to make a fully informed decision, we need to consider the stress on the turbo when running stage 2 boost with both stock and high-flow downpipes.

As I mentioned, PTF includes downpipes as a mandatory upgrade for stage 2. Since they don’t sell downpipes, there’s no financial incentive for them to recommend it. it would be better for them to promote making more power with stock downpipes

If PTF recommends downpipes, it’s because their testing has shown that they’re necessary. They know tuning better than anyone, so I trust what they recommend.

As long as the conversation stays respectful, it’s great to share ideas and learn from each other, that’s what forums are for. I wouldn’t be upset if I’m proven wrong; thats how i get better

[who is this noob]

To make a fully informed decision, we need data. I have looked everywhere and find nothing from these companies beyond "Stage 2 requires downpipe." If they wanted to publish test data, and show failure points in the stock hardware, presumably they could. They don't. How come? Because the market has not demanded it. Because people are buying aftermarket downpipes based on "Stage 2 requires downpipe."

In this hobby, everyone has different taste and every modification has different pros and cons:

• A big brake kit looks cool but adds weight.
• A coilover suspension lowers the car but rides stiffer.
• A downpipe might make a little more power, but also a lot more emissions.

As JNat posted above and I'm reposting below, ProTuningFreaks off-the-shelf (OTS) tunes on BM3 platform make 2% or 3% more power at Stage 2. Using round numbers, that means an X3M Competition starting with 503hp and running 93 octane, would make 608hp on stock pipe and 618hp on aftermarket pipe. Step back people, make room, we got a big power player coming through with an extra 10hp. But what are the downsides? How much more emissions? How much less reliability? Sound and smell are subjective so this is why I focus on emissions and hardware failures. These are things we can measure.

Stage 1 ACN91 octane: 11%HP / 25% TQ
Stage 2 ACN91 octane: 13%HP / 28% TQ

Stage 1 91 octane: 17% HP / 28% TQ
Stage 2 91 octane: 20% HP / 30% TQ

Stage 1 93 octane: 21% HP / 31% TQ
Stage 2 93 octane: 23% HP / 34% TQ

Stage 1 E30 octane: 31% HP / 41% TQ
Stage 2 E30 octane: 33% HP / 44% TQ

For many of us, 10hp does not justify increased emissions, smell, and sound. The juice ain't worth the squeeze.

Originally Posted by mike@x-ph.com

As long as the conversation stays respectful, it’s great to share ideas and learn from each other, that’s what forums are for.

We are all here to have fun and enjoy our cars.

[mike@x-ph.com]

Originally Posted by who is this noob

To make a fully informed decision, we need data. I have looked everywhere and find nothing from these companies beyond "Stage 2 requires downpipe." If they wanted to publish test data, and show failure points in the stock hardware, presumably they could. They don't. How come? Because the market has not demanded it. Because people are buying aftermarket downpipes based on "Stage 2 requires downpipe."

In this hobby, everyone has different taste and every modification has different pros and cons:

• A big brake kit looks cool but adds weight.
• A coilover suspension lowers the car but rides stiffer.
• A downpipe might make a little more power, but also a lot more emissions.

As JNat posted above and I'm reposting below, ProTuningFreaks off-the-shelf (OTS) tunes on BM3 platform make 2% or 3% more power at Stage 2. Using round numbers, that means an X3M Competition starting with 503hp and running 93 octane, would make 608hp on stock pipe and 618hp on aftermarket pipe. Step back people, make room, we got a big power player coming through with an extra 10hp. But what are the downsides? How much more emissions? How much less reliability? Sound and smell are subjective so this is why I focus on emissions and hardware failures. These are things we can measure.

Stage 1 ACN91 octane: 11%HP / 25% TQ
Stage 2 ACN91 octane: 13%HP / 28% TQ

Stage 1 91 octane: 17% HP / 28% TQ
Stage 2 91 octane: 20% HP / 30% TQ

Stage 1 93 octane: 21% HP / 31% TQ
Stage 2 93 octane: 23% HP / 34% TQ

Stage 1 E30 octane: 31% HP / 41% TQ
Stage 2 E30 octane: 33% HP / 44% TQ

For many of us, 10hp does not justify increased emissions, smell, and sound. The juice ain't worth the squeeze.





We are all here to have fun and enjoy our cars.

Thank you for taking the time to post the data, but I want to ensure we are on the same page.

We are not discussing whether stage 2 is worth it or not. That is a personal decision.

We are discussing whether the upgraded downpipes are needed for stage 2 or if the user can run it with stock downpipes.

[e30 4 life!]

There are plenty of custom tuned stage 1 x3m's running in the low 10's. Base tuning platform license and a custom street log adjusted tune would be my advice for a "safe" tune if that's the goal. OTS files are conservative in nature as they have to take into account a wide range of hardware and fuel quality.

[who is this noob]

Originally Posted by antaskov

My car is daily and i am not trying to push power as much as possible.
My goal is to get the maximum power possible keeping acceptable comfort and noise levels. So its the balance i want to find.

and

Originally Posted by e30 4 life!

There are plenty of custom tuned stage 1 x3m's running in the low 10's.

winner winner chicken dinner!

antaskov, is a low 10's car sufficient for your daily driving needs? Based on your goals, money is better spent on a custom tune than an unnecessary downpipe. This is probably the sweet spot for most people.

It is the best of both worlds. A fun, fast car with no huge increase in emissions or smelly exhaust fumes.

[Th3Walrus]

It's well known with most BMW engines the big gains are Stock --> Stage 1, then Stage 1 --> Stage 2+. Stage 1 --> Stage 2 usually offers little gain. But that's not what we're talking about. Stage 2 and beyond requires aftermarket downpipe(s), for BM3 and MHD. Also not talking about JB4.

[les anderson]

These cars have primary and secondary cats in the midpipe from what I understsnd. If you want to go stage 2, do you need to replace both?(all 3)

I have also read that due to the secondary cat, there is no smell when you go catless for the primaries, can anyone confirm this? I have had multiple people tell me this.

My motivation for stage 2 would be sound and cost. You can go catless on the primaries for $400-$600 and have no smell due to secondary, and then sell your OEM cats for way more than what you pay for the catless. Not a bad outcome if no smell is true.