[G.Newt]

Originally Posted by Skyhigh

That is not true. Pay attention to the fact that I am referring to a stock car. What I claim is that each factory component is "fit for purpose" and (as a general rule) does not require improvement.
B58's purpose when stock is to delivered 450NM and 326PS.
Not more, not less. What M's purpose is - is irrelevant for the discussion. You will not transfer a non-M into M, no matter how many components you replace.

https://f80.bimmerpost.com/forums/sh....php?t=1114006

I get what you're saying, but a downpipe DOES increase power just on its own.

[marcthedark]

Originally Posted by Skyhigh

That is not true. Pay attention to the fact that I am referring to a stock car. What I claim is that each factory component is "fit for purpose" and (as a general rule) does not require improvement.
B58's purpose when stock is to delivered 450NM and 326PS.
Not more, not less. What M's purpose is - is irrelevant for the discussion. You will not transfer a non-M into M, no matter how many components you replace.

Dream on. You are not an engineer if you assume BMW stock can not be improved.
Go bother someone else

[Skyhigh]

Don't feel obliged to answer
It is obvious you have no clue.
Everything can be improved. Question is what does it bring.
You can for example "improve" the air filter box by putting a carbon-fibre one instead. Does the CF add any functional/performance value? No.
But the looks is improved, your placebo is triggered and the vendor's bank account is celebrating. So go ahead.

[vcx]

Originally Posted by Skyhigh

Don't feel obliged to answer
It is obvious you have no clue.
Everything can be improved. Question is what does it bring.
You can for example "improve" the air filter box by putting a carbon-fibre one instead. Does the CF add any functional/performance value? No.
But the looks is improved, your placebo is triggered and the vendor's bank account is celebrating. So go ahead.

Hey, I also wondered why would the manufacturers use subpar design intentionnally, and how could aftermarket product be better.

Tadge Juechter (chief engineer for Corvette) answered that question on another forum.

He said that stock components must comply with so many requirement (legal, warranty, durability, etc.) and this for the whole world, including sandy condition in desert area, high altitude places, etc. and manufacturers have to find the right balance between performance, affordability, legal compliance, etc.

Therefore, it is very well possible that an aftermarket product can be designed to be more performance oriented, at the expense of other requirements (no longer emission compliant, or it won't last as much, talking about air filter, for ex., not be suitable for places where air is full of sand, etc.

In the end, every product is just a compromise between different variables, the question is where do you want to point the cursor: performance ? everyday usability ? etc.

That's why it's important to determine your needs and see what product could give you what you want.

[Skyhigh]

vcx
All of the above is absolutely true! I work with vehicle manufacturers (different type of vehicles) and I have a direct insight into the requirement specification of their components and systems. You are very correct that an OEM has to consider a lot of factors and ensure their (selected) product has the right balance.

You are also correct that by dropping some of the requirements (e.g. environmental qualification and durability, noise, etc.), one can produce a product which satisfies other requirements better.

HOWEVER:
- The number considerations OEMs have to take into account do not make their components unfit for purpose! Just because a downpipe has to comply with extreme environmental conditions, nosie regulations etc, does not make it unfit to serve its purpose (which would be a design failure). A stock downpipe must be and is perfectly capable of allowing the turbo to deliver what it is required to deliver by the stock engine and engine control unit. Yes, it may be heavier, more expensive, more restrictive, etc., etc. than an aftermarket one.... but it is still perfectly fit for purpose! Same goes for the air filter, spark plugs, you name it.
- What Aftermarket manufacturers are only interested in however is meeting the demand of the market and making their product more attractive by (over)promising. Whilst you can gain from such products, the risk is also that you don't know what they are not telling you or what they do not know themselves. Which basically means you should be damn sure you gain what you expect to gain, otherwise you are paying to add uncertainty on fronts you haven't even thought about. Speaking about gas flows - gases are a funny thing. Having worked with wind channels for determination of drag, you often see air go ways you would not anticiapte just by common sense. One wrong edge or angle and suddenly your higher diameter pipe becomes more restrictive, because you created gas recirculation and induced drag.

[marcthedark]

Originally Posted by Skyhigh

vcx
All of the above is absolutely true! I work with vehicle manufacturers (different type of vehicles) and I have a direct insight into the requirement specification of their components and systems. You are very correct that an OEM has to consider a lot of factors and ensure their (selected) product has the right balance.

You are also correct that by dropping some of the requirements (e.g. environmental qualification and durability, noise, etc.), one can produce a product which satisfies other requirements better.

HOWEVER:
- The number considerations OEMs have to take into account do not make their components unfit for purpose! Just because a downpipe has to comply with extreme environmental conditions, nosie regulations etc, does not make it unfit to serve its purpose (which would be a design failure). A stock downpipe must be and is perfectly capable of allowing the turbo to deliver what it is required to deliver by the stock engine and engine control unit. Yes, it may be heavier, more expensive, more restrictive, etc., etc. than an aftermarket one.... but it is still perfectly fit for purpose! Same goes for the air filter, spark plugs, you name it.
- What Aftermarket manufacturers are only interested in however is meeting the demand of the market and making their product more attractive by (over)promising. Whilst you can gain from such products, the risk is also that you don't know what they are not telling you or what they do not know themselves. Which basically means you should be damn sure you gain what you expect to gain, otherwise you are paying to add uncertainty on fronts you haven't even thought about. Speaking about gas flows - gases are a funny thing. Having worked with wind channels for determination of drag, you often see air go ways you would not anticiapte just by common sense. One wrong edge or angle and suddenly your higher diameter pipe becomes more restrictive, because you created gas recirculation and induced drag.

TROLL go spam somewhere else as there are enough Dynos out there showing that you have no idea what you are talking about

[vcx]

Originally Posted by Skyhigh

vcx
All of the above is absolutely true!

I fully agree with you.

The real difficulty is to determine if a specific product will really bring any real life benefit, in your own case, which can be hard to prove.

Luckily, we have dyno tests, but they are only valid (let alone the question of their preciseness) for one specific car, with one specific tune.

In my case, I am wondering if a catted DP would bring any improvement to my car, and I can't find the answer. My 340i with MPPSK is running a stage 1 MG Flash tune, with torque limiter to 540 NM to preserve the manual transmission.

I would like to know if, with this modest tune, (for which a sport DP isn't required, according to MG Flasher) a DP (akrapovic probably) would change something (faster turbo response, or less stress on turbo) or if the standard DP is already enough.

If anybody have an answer..

[kern417]

Skyhigh does this on every thread about bolt ons. If you really worked for an OEM then you'd know just how many design compromises are made. I worked for multiple (for actual vehicles) and in no way is everything designed perfectly for efficiency. It's designed to meet a requirement.

The order or priority goes something like:
1. Safety
2. Emissions
3. Quality/Sales
4. Performance

Your thought that the car is designed with maximum efficiency completely ignores how business works. If they could charge as much as they wanted for the car and felt it would increase sales, then that would be a possibility. But the fact that the stock turbo can put out over 200% of the factory boost targets shows how much they leave on the table for various reasons. Some people leave a bunch of headroom on the table, then others like Mercedes has a 400hp 4 cylinder running 25+ psi from the factory floor. It's not that everyone can't do this, but everyone has a different business model.

What's really interesting is more and more OEMs are switching to cone filters for high hp cars. That shows that even they recognize that intake surface area is important to flow on boosted applications. But if it's not needed, why bother.

A lot of people ask why these things are offered by aftermarket companies but not OEMs that have way more resources. I'll tell you 100%, no matter what design I come up with, if the cost doesn't improve sales, it's not happening. If I can't give the part to a line operator and have it installed reliably, it's not happening. If I can't find anyone to produce 500k+/year at a reasonable price, it's not happening. And aftermarket companies don't suffer from those limitations.

I tell you this every time and you just ignore it, but I feel better at least putting some truth out there.

[Ahanix]

Originally Posted by vcx

I fully agree with you.

The real difficulty is to determine if a specific product will really bring any real life benefit, in your own case, which can be hard to prove.

Luckily, we have dyno tests, but they are only valid (let alone the question of their preciseness) for one specific car, with one specific tune.

In my case, I am wondering if a catted DP would bring any improvement to my car, and I can't find the answer. My 340i with MPPSK is running a stage 1 MG Flash tune, with torque limiter to 540 NM to preserve the manual transmission.

I would like to know if, with this modest tune, (for which a sport DP isn't required, according to MG Flasher) a DP (akrapovic probably) would change something (faster turbo response, or less stress on turbo) or if the standard DP is already enough.

If anybody have an answer..

According to MG Flasher, MHD, Bootmod3 the factory downpipe is more than sufficient for the modest (Stage 1) tune that you have on your car. Based on their recommendations, you need a downpipe capable of higher flow if you are to surpass the ~16psi the Stage 1 tune has set as the ceiling without causing unnecessary backpressure on the turbo, and also negatively impacting the factory cats. If you go Stage 2 and above, you'll need an upgraded downpipe.

[kern417]

Originally Posted by vcx

I fully agree with you.

The real difficulty is to determine if a specific product will really bring any real life benefit, in your own case, which can be hard to prove.

Luckily, we have dyno tests, but they are only valid (let alone the question of their preciseness) for one specific car, with one specific tune.

In my case, I am wondering if a catted DP would bring any improvement to my car, and I can't find the answer. My 340i with MPPSK is running a stage 1 MG Flash tune, with torque limiter to 540 NM to preserve the manual transmission.

I would like to know if, with this modest tune, (for which a sport DP isn't required, according to MG Flasher) a DP (akrapovic probably) would change something (faster turbo response, or less stress on turbo) or if the standard DP is already enough.

If anybody have an answer..

Your engine is an air pump. Anything that increases air throughput without generating too much heat will net an improvement. It won't always be peak hp numbers so a dyno won't always show you this. You can also improve things like spool time, gas mileage, etc. Any restrictions are bad. This creates additional work that the engine has to overcome and robs your efficiency, i.e. performance is decreased.

Typically bolt ons like an intake and downpipe without a tune only improve response and widen the powerband. The hp gains are minimal, but that doesn't mean it's not faster.

[marcthedark]

Originally Posted by vcx

I fully agree with you.

The real difficulty is to determine if a specific product will really bring any real life benefit, in your own case, which can be hard to prove.

Luckily, we have dyno tests, but they are only valid (let alone the question of their preciseness) for one specific car, with one specific tune.

In my case, I am wondering if a catted DP would bring any improvement to my car, and I can't find the answer. My 340i with MPPSK is running a stage 1 MG Flash tune, with torque limiter to 540 NM to preserve the manual transmission.

I would like to know if, with this modest tune, (for which a sport DP isn't required, according to MG Flasher) a DP (akrapovic probably) would change something (faster turbo response, or less stress on turbo) or if the standard DP is already enough.

If anybody have an answer..

Just search as people did this before > catless DP
https://f30.bimmerpost.com/forums/sh....php?t=1229945

Wagner provides pressure drop aka increased flow charts
https://www.wagner-tuning.com/produc...027-hjs-1.html
and states
made out of high quality stainless steel 1.4301 (SS304)
complete Ø3,5 and adapter for stock exhaust
HJS (ECE approval) 300CPSI EU6 Racing Metal Catalytic Converter
100% perfect fit, replace OEM
less thermal load on the turbocharger
more power by reducing back pressure
significantly more torque
>> and Wagner is not a dinky fly by night operation

[vcx]

thanks a lot guys for your answers, very appreciated.

[Skyhigh]

Originally Posted by kern417

...

I see you are completely locked in a glossy brochure. Claiming that the OEM produces parts which are unfit for purpose and incapable of performing their intended function is.... hilarious. At the same time you point out what (safety) margins and reserves OEM components have... Go figure the contradiction.
No further comments. Trust aftermarket manufacturer's marketing. They would not survive without people like you

[Skyhigh]

Originally Posted by vcx

I fully agree with you.

The real difficulty is to determine if a specific product will really bring any real life benefit, in your own case, which can be hard to prove.

Luckily, we have dyno tests, but they are only valid (let alone the question of their preciseness) for one specific car, with one specific tune.

In my case, I am wondering if a catted DP would bring any improvement to my car, and I can't find the answer. My 340i with MPPSK is running a stage 1 MG Flash tune, with torque limiter to 540 NM to preserve the manual transmission.

I would like to know if, with this modest tune, (for which a sport DP isn't required, according to MG Flasher) a DP (akrapovic probably) would change something (faster turbo response, or less stress on turbo) or if the standard DP is already enough.

If anybody have an answer..

That's where the discussion started from. I asked myself "Would a modified DP do anything for me (stock MPPSK)" and no matter how I look at it, I see no technical explanation that can justify this particular €1000+ mod. And unlike others, I don't just do things because it says on the brochure that something will be great (again) or because it is a hype.
In your case, with the additional tune, I can see why it may help. Whether it is worth the money - different question. But better do that, than putting a crappy air filter upstream, just because of its fancy shape or carbon fiber casing. Don't be a teleshop customer.

[G.Newt]

Originally Posted by Skyhigh

That's where the discussion started from. I asked myself "Would a modified DP do anything for me (stock MPPSK)" and no matter how I look at it, I see no technical explanation that can justify this particular €1000+ mod. And unlike others, I don't just do things because it says on the brochure that something will be great (again) or because it is a hype.
In your case, with the additional tune, I can see why it may help. Whether it is worth the money - different question. But better do that, than putting a crappy air filter upstream, just because of its fancy shape or carbon fiber casing. Don't be a teleshop customer.

People have done downpipe only dynos for various types of vehicles and it's all the same: typically some small gain, with a slight change in the area under the curve.

Which question are you asking? "Does a modified DP gain me anything" vs "Are the gains worth the cost." Those are 2 different things. One is a yes/no, the other is subjective.

The link I posted above when I quoted you previously, showed quite a large gain on an F80. That's not typical but it illustrates the point nonetheless.

[Skyhigh]

Definitely not typical. I also doubt that the same conditions applied during both tests. But I have watched some further youtube videos and yes - in some (by far not all!) cases there is something to be gained. Not in terms of top engine power, but rather a slightly improved curve.

The fact that MPPSK comes with larger diameter and less restrictive exhaust system also indicates the neccessity to reduce back pressure when the demand from the engine increases. No doubt there. BMW state it themselves that this was their choice for the B58 ,whereas for previous generations they reduced the airflow resistance on the intake instead. But again my question was related to a comparison between stock engine with stock DP and stock engine with less restrictive DP and the answer is above. My own conclusion is that whilst one may (not guaranteed) gain something along the curve, it is not really worth it (also considering the price), unless it goes with a tune.

This said, I may do it anyway

[kern417]

Originally Posted by Skyhigh

I see you are completely locked in a glossy brochure. Claiming that the OEM produces parts which are unfit for purpose and incapable of performing their intended function is.... hilarious. At the same time you point out what (safety) margins and reserves OEM components have... Go figure the contradiction.
No further comments. Trust aftermarket manufacturer's marketing. They would not survive without people like you

Like I said, I've designed OEM parts, modified, cancelled them, moved them to new suppliers...the whole 9 yards. Every time I have to modify a part and improve it's reliability, it's because it doesn't meet it's intended purpose.

Before I change it, I have to submit specs for it's weight difference. Why? Because it can effect MPG.

Then I have to submit a cost analysis. Why? Because the cost of the improvement has to be less than the cost of warranty repairs.

You're literally the only clueless one spewing this info everywhere lol. I get one day you had a eureka moment and thought you were onto something, but there are huge gaps in your line of thinking. At the end of the day, you could have an engine designed at 99% capacity to hold 1000hp. But that 1% that's designed to only hold 200hp is all you need to limit the entire system's capability.

[Skyhigh]

kern417
Unlike me, you seem to have it all figured out. Good for you!
I'd watch out for that Dunning–Kruger effect though, if I were you... might get even worse.

[IMS-340C]

I agree with you in some points but if you think MPPSK makes a difference because it's less restrictive so why doesn't a downpipe also make a difference as it's also less restrictive?

Originally Posted by Skyhigh

Definitely not typical. I also doubt that the same conditions applied during both tests. But I have watched some further youtube videos and yes - in some (by far not all!) cases there is something to be gained. Not in terms of top engine power, but rather a slightly improved curve.

The fact that MPPSK comes with larger diameter and less restrictive exhaust system also indicates the neccessity to reduce back pressure when the demand from the engine increases. No doubt there. BMW state it themselves that this was their choice for the B58 ,whereas for previous generations they reduced the airflow resistance on the intake instead. But again my question was related to a comparison between stock engine with stock DP and stock engine with less restrictive DP and the answer is above. My own conclusion is that whilst one may (not guaranteed) gain something along the curve, it is not really worth it (also considering the price), unless it goes with a tune.

This said, I may do it anyway

[Skyhigh]

Pay attention to the key words in bold:
"The fact that MPPSK comes with larger diameter and less restrictive exhaust system also indicates the neccessity to reduce back pressure when the demand from the engine increases."

MPPSK comes with an engine tune, which is why a relieved exhaust can be advantageous and desirable.

DP makes sense to also possibly contribute to tuned engines.

The whole discussion I started however was about the benefit (or lack of) of a DP for a stock engine.

I also don't think an MPPSK exhaust, without the tune, would bring any noticable performance benefit. That's even less likely than for a DP.

[marcthedark]

Originally Posted by Skyhigh

Pay attention to the key words in bold:
"The fact that MPPSK comes with larger diameter and less restrictive exhaust system also indicates the neccessity to reduce back pressure when the demand from the engine increases."

MPPSK comes with an engine tune, which is why a relieved exhaust can be advantageous and desirable.

DP makes sense to also possibly contribute to tuned engines.

The whole discussion I started however was about the benefit (or lack of) of a DP for a stock engine.

I also don't think an MPPSK exhaust, without the tune, would bring any noticable performance benefit. That's even less likely than for a DP.

You are an engineer? Back pressure? That isn't a thing between engineers it is used to make a concept understandable for laymen.
A turbo works best if there is no restriction afterwards. If you have a NA engine then you want to calculate the best diameter etc to have a "push - pull" effect of the exhaust gas waves (not sure if that is the correct expression as I studied it in german ) and best here is determined "best for a certain rpm range". But everything after a turbo isn't there for efficiency/power/... and only increases the stress on the turbo. The exhaust etc is just there for emissions/noise/.....

[Skyhigh]

Yes I am and in fact also studied in German(y). In English however, the term backpressure is commonly used - both in engineering and in forums In aviation jet engines one also speaks about compressor "backpressure".

And yes, what you are saying is absolutely correct, including the difference between a NA and turbo-charged engine. A turbo charged engine does not require backpressure, whereas a NA engine requires certain "backpressure" (in reality exhaust velocity or in German - Zieheffekt) to "extract" the exhaust gases from the cylinders more efficiently.

But whilst all of the above is absolutely correct, it does not mean that a stock car and a stock turbo has any problems achieving its required performance with the backpressure created by the stock catalytic converter and DP (which is there as you have correctly noted for very different reasons). It is only when you increase that required performance (by e.g. a tune) when you may benefit from changes to the exhaust system and reduced or eliminated backpressure. This is all we are talking about. A stock car is perfectly happy to remain stock and still perform as per its stock requirements and deliver all of its stock performance as every component is, despite various forms of resistance, fully fit for purpose and perfectly capable of overcoming that resistance! It does not need you "fixing" it