[BMWsalesguyFL]

I'm confused about the whole golf tee mod after watching my exhaust flap on cold start today. I have the MPE but I was under the impression that the exhaust was louder on cold start because both valves are opened and then it quiets down because the valve closes. Before starting my car tonight, I looked into the exhaust, and the valve was completely shut. The cold start was loud as usual with the MPE but after about a minute or so the exhaust goes quiet and the valve opens up the left side of the exhaust which is the complete opposite of what I thought it did. The valve has never been closed when I look into the exhaust after driving the car which is why I am confused as to how the "golf tee mod" or keeping the valve open, would make the exhaust louder. I always drive in sport mode since I got the car about a week ago but the valve is definitely always open already when I am driving.

Is everyone confusing the valve opening as closing on cold start and doing the "golf tee mod" for no reason, or does the MPE reverse this and make holding the flap open useless since it seems to open after the car warms up anyways??

[Tditty]

Originally Posted by BMWsalesguyFL

I'm confused about the whole golf tee mod after watching my exhaust flap on cold start today. I have the MPE but I was under the impression that the exhaust was louder on cold start because both valves are opened and then it quiets down because the valve closes. Before starting my car tonight, I looked into the exhaust, and the valve was completely shut. The cold start was loud as usual with the MPE but after about a minute or so the exhaust goes quiet and the valve opens up the left side of the exhaust which is the complete opposite of what I thought it did. The valve has never been closed when I look into the exhaust after driving the car which is why I am confused as to how the "golf tee mod" or keeping the valve open, would make the exhaust louder. I always drive in sport mode since I got the car about a week ago but the valve is definitely always open already when I am driving.

Is everyone confusing the valve opening as closing on cold start and doing the "golf tee mod" for no reason, or does the MPE reverse this and make holding the flap open useless since it seems to open after the car warms up anyways??

Nope. Mine does the same thing. It's closed when I start and the car is cold. As soon as it warms up a minute it opens up. And stays open. That's why the mod us sorta useless.

[Bee Pee]

Guys,

If Fxx N55b is anything like E9x N54, then cold start has turbo wastegate open for about 60 secs to allow primary cat in the DP to warm up.

On my N54 with MPE, it got quieter still after 5-8mins of running as this was when WGDC would work fully allowing full boost targets to be achieved once oil temp gauge started to move.

Believe that WG has more impact on exhaust volume than golf tee mod....

PD.

[Vitoco]

You´re wrong. On a cold start, the valve OPENS. When it gets quieter, after a few seconds, it has closed. Start the car and go out back and watch/feel the fumes come out of the left pipe. The reason for closing the valve is for the engine to reach it´s working temp quicker, and since you´re not supposed to rev above 3000 rpms before the oil is warm there´s no reason for that flap to open either. Especially important on colder days. So for the winter, I would remove the GT-mod.

[Gio72]

Originally Posted by Vitoco

You´re wrong. On a cold start, the valve OPENS. When it gets quieter, after a few seconds, it has closed. Start the car and go out back and watch/feel the fumes come out of the left pipe. The reason for closing the valve is for the engine to reach it´s working temp quicker, and since you´re not supposed to rev above 3000 rpms before the oil is warm there´s no reason for that flap to open either. Especially important on colder days. So for the winter, I would remove the GT-mod.

No, it never happend neither to my 435i MPPK with MPE, nor to my old E91 335xi with PE.
Make somebody switch on the car (cold start) instead of you and, in the meanwhile, put yourself on the back to observe the valve

[Gio72]

Originally Posted by BMWsalesguyFL

I'm confused about the whole golf tee mod after watching my exhaust flap on cold start today. I have the MPE but I was under the impression that the exhaust was louder on cold start because both valves are opened and then it quiets down because the valve closes. Before starting my car tonight, I looked into the exhaust, and the valve was completely shut. The cold start was loud as usual with the MPE but after about a minute or so the exhaust goes quiet and the valve opens up the left side of the exhaust which is the complete opposite of what I thought it did. The valve has never been closed when I look into the exhaust after driving the car which is why I am confused as to how the "golf tee mod" or keeping the valve open, would make the exhaust louder. I always drive in sport mode since I got the car about a week ago but the valve is definitely always open already when I am driving.

Is everyone confusing the valve opening as closing on cold start and doing the "golf tee mod" for no reason, or does the MPE reverse this and make holding the flap open useless since it seems to open after the car warms up anyways??

Absolutely normal.
As I wrote before, I experienced the same behaviour on my old 335xi and my new 435i, both with MPE
I think that after moving the car at low speed the valve shuts and re-open at certain revs (around 3000).

[Vitoco]

I have been standing out back several times right after a cold start, the left pipe has exhausts coming out. And then when the engine note settles a little, you hear the valve close and you can see that there's no flow there.

[justinnum1]

so do you get more sound when it's close or open?

[BMWsalesguyFL]

Originally Posted by Vitoco

You´re wrong. On a cold start, the valve OPENS. When it gets quieter, after a few seconds, it has closed. Start the car and go out back and watch/feel the fumes come out of the left pipe. The reason for closing the valve is for the engine to reach it´s working temp quicker, and since you´re not supposed to rev above 3000 rpms before the oil is warm there´s no reason for that flap to open either. Especially important on colder days. So for the winter, I would remove the GT-mod.

Not wrong. It is closed during cold start and opens up after thirty seconds or so. I watched the valve open. Look into your exhaust and watch it. Maybe it's different with your 328i. Doubt it though.

[Vitoco]

Originally Posted by BMWsalesguyFL

Not wrong. It is closed during cold start and opens up after thirty seconds or so. I watched the valve open. Look into your exhaust and watch it. Maybe it's different with your 328i. Doubt it though.

In that case you are suggesting it's open at ALL times, exc3pt upon start-up. May I ask what function it fills then?.... yeah, none. 328i or 335i, same principle applies; it's closed when cruising along and open above 3k - closed to help the engine reach it's working temp quicker and to restrict exhaust flow at lower revs, to help with the pull. Opens up for more flow to decrease back pressure for better performance.

[DVC]

Originally Posted by CG Precision

I posted this in a different thread but think it's relevant here also.

CG Precision.

So, if the valve is closed at cold start-up, then I guess you get the louder exhaust sound while the valve is closed, right? If that's the case, is the point of the "golf tee mod" to keep the valve open and make the exhaust more quiet??
Is there a reason the valve opens at higher RPMs? (Less back-pressure, would be my guess...)

Cold-start-up = closed = louder
Idle after 55 seconds = open = quieter
Engage gear and drive off = closed = louder again
Hit higher RPMs = open = quieter again

It seems like a complicated strategy that BMW has engineered, and I'm wondering if they designed it to work this way for specific reasons.

[Professor///M]

You guys are so confusing

[steveMizdaman]

Just pull the plug, open all the time, you dont like it plug it back in. With mine open all the time, it still goes from loud to quiet on cold start up. Only diffetence I hear with the plug disconnected is slightly louder rumble driving in comfort mode at lower rpms. And of course evenly dirty exhaust tips when washing the car.

[steveMizdaman]

Just pull the plug, open all the time, you dont like it plug it back in. With mine open all the time, it still goes from loud to quiet on cold start up. Only diffetence I hear with the plug disconnected is slightly louder rumble driving in comfort mode at lower rpms. And of course evenly dirty exhaust tips when washing the car.

[BMWsalesguyFL]

Originally Posted by Vitoco

In that case you are suggesting it's open at ALL times, exc3pt upon start-up. May I ask what function it fills then?.... yeah, none. 328i or 335i, same principle applies; it's closed when cruising along and open above 3k - closed to help the engine reach it's working temp quicker and to restrict exhaust flow at lower revs, to help with the pull. Opens up for more flow to decrease back pressure for better performance

.

he stock valve closes for approximately 55 seconds upon start-up. After that, the valve is opened during idle. When driving around, depending on which mode you are in (eco-pro, comfort, sport and sport+), the valve opens and closes at specific RPM's and throttle position. Mostly, the valve is closed in the lower RPM range and open at higher RPM range. It remains opened during idle but closes when you engage any gear.

As the above quote says, I think that it is closed during cold start so that the cat can reach temperatures faster. If it was opened at cold start, it would take longer to light the cat off. I am positive that it is closed during cold start and opens after a minute or so. When it is opened and closed after that, I am not sure. I would guess that as soon as you start driving, it will close again until you hit a certain RPM or apply a certain amount of throttle which is why doing the golf tee mod may still be beneficial so that it will be open throughout the entire RPM range rather then just after 3k or whatever it is. I'm going to unplug mine like the person above did after it opens so that it will always stay open.

[BMWsalesguyFL]

Originally Posted by steveMizdaman

Just pull the plug, open all the time, you dont like it plug it back in. With mine open all the time, it still goes from loud to quiet on cold start up. Only diffetence I hear with the plug disconnected is slightly louder rumble driving in comfort mode at lower rpms. And of course evenly dirty exhaust tips when washing the car.

Like Pave Dew said, I bet the main difference in volume is due to something with the waste gate. I'm gonna unplug mine now and see how it is.

[BMWsalesguyFL]

Originally Posted by CG Precision

Apologies in advance for the long response, but I wanted to be thorough.

All cars emit the majority of their emissions during the first few minutes until the catalytic converter warms up. This is a problem for manufactures to meet new emissions requirements. This is especially bad for turbocharged vehicles because the turbo, when cold, is a large heat sink that cools down the exhaust gas before the turbo warms up. The hotter the exhaust gas, the faster the catalytic converter will warm up. Placing the cat closer to the engine helps, which is why these new turbo engines all have the cat in the down pipe. BMW has also used two more tricks to warm up the cat faster.

1) The direct injection allows more control over the air fuel mixture and allows the engine to warm up with very retarded timing and also very lean (high oxygen to fuel mixture). This is done with a highly controlled "double injection" process and results in faster cat warm up.

2) The turbocharger has an electronically controlled wastegate that bypasses exhaust gas around the turbocharger turbine wheel and into the inlet to the down pipe. BMW programmed the wastegate to be opened more fully (up to 70% open) during warmup. This keeps the turbo from sucking the heat out of the exhaust gas, so the hot gas gets to the cat and warms it up quickly.

These tricks are how the new N20 engine qualifies for SULEV status. The N55 utilizes the same tricks.

So what does this have to do with an exhaust valve for the muffler? on a turbocharged vehicle, the gas passing through the turbo quiets the exhaust noise down a lot. When the wastegate is open, the exhaust noise is much louder. BMW did not want to turn off some potential buyers with such a loud warm-up. To decrease this effect and also to allow eliminating drone under low load conditions, BMW engineered a muffler that is quieter when the valve is closed and louder when it is open.

So, during start-up the exhaust valve is closed for 55 seconds while the wastegate is open and the engine is in fast cat warm up mode. If the valve were open, the engine will be even louder on start up. After the warmup routing is done, the valve opens. But as many of you have pointed out, the car is quieter at this time. That is because the wastegate is now closed and the turbo is quieting down the exhaust too.

So to summarize, having the exhaust valve open will always make the car louder for any particular engine condition than if the exhaust valve were closed. The BMW OEM exhaust works this way, as does our VS-1 performance exhaust system. Both exhausts can be computer controlled by leaving the motor plugged in. And both can be controlled at any time by remote with our VSC-1 controller.

Perfect summary. Thank you. I just unplugged the flap so that it will be permanently open. Can having the flap open during cold start cause wear on the turbo, cat or have any harmful effects other than being louder?

[DVC]

Originally Posted by CG Precision

Apologies in advance for the long response, but I wanted to be thorough.

All cars emit the majority of their emissions during the first few minutes until the catalytic converter warms up. This is a problem for manufactures to meet new emissions requirements. This is especially bad for turbocharged vehicles because the turbo, when cold, is a large heat sink that cools down the exhaust gas before the turbo warms up. The hotter the exhaust gas, the faster the catalytic converter will warm up. Placing the cat closer to the engine helps, which is why these new turbo engines all have the cat in the down pipe. BMW has also used two more tricks to warm up the cat faster.

1) The direct injection allows more control over the air fuel mixture and allows the engine to warm up with very retarded timing and also very lean (high oxygen to fuel mixture). This is done with a highly controlled "double injection" process and results in faster cat warm up.

2) The turbocharger has an electronically controlled wastegate that bypasses exhaust gas around the turbocharger turbine wheel and into the inlet to the down pipe. BMW programmed the wastegate to be opened more fully (up to 70% open) during warmup. This keeps the turbo from sucking the heat out of the exhaust gas, so the hot gas gets to the cat and warms it up quickly.

These tricks are how the new N20 engine qualifies for SULEV status. The N55 utilizes the same tricks.

So what does this have to do with an exhaust valve for the muffler? on a turbocharged vehicle, the gas passing through the turbo quiets the exhaust noise down a lot. When the wastegate is open, the exhaust noise is much louder. BMW did not want to turn off some potential buyers with such a loud warm-up. To decrease this effect and also to allow eliminating drone under low load conditions, BMW engineered a muffler that is quieter when the valve is closed and louder when it is open.

So, during start-up the exhaust valve is closed for 55 seconds while the wastegate is open and the engine is in fast cat warm up mode. If the valve were open, the engine will be even louder on start up. After the warmup routing is done, the valve opens. But as many of you have pointed out, the car is quieter at this time. That is because the wastegate is now closed and the turbo is quieting down the exhaust too.

So to summarize, having the exhaust valve open will always make the car louder for any particular engine condition than if the exhaust valve were closed. The BMW OEM exhaust works this way, as does our VS-1 performance exhaust system. Both exhausts can be computer controlled by leaving the motor plugged in. And both can be controlled at any time by remote with our VSC-1 controller.

Thanks - the info about the waste gate clears up pretty much everything! Too bad there's no way to get the WG to stay open when so desired (or is there?)
So, as the posted above asked, is there any downside to have the valve open all the time?

[Gio72]

Originally Posted by CG Precision

Apologies in advance for the long response, but I wanted to be thorough.

All cars emit the majority of their emissions during the first few minutes until the catalytic converter warms up. This is a problem for manufactures to meet new emissions requirements. This is especially bad for turbocharged vehicles because the turbo, when cold, is a large heat sink that cools down the exhaust gas before the turbo warms up. The hotter the exhaust gas, the faster the catalytic converter will warm up. Placing the cat closer to the engine helps, which is why these new turbo engines all have the cat in the down pipe. BMW has also used two more tricks to warm up the cat faster.

1) The direct injection allows more control over the air fuel mixture and allows the engine to warm up with very retarded timing and also very lean (high oxygen to fuel mixture). This is done with a highly controlled "double injection" process and results in faster cat warm up.

2) The turbocharger has an electronically controlled wastegate that bypasses exhaust gas around the turbocharger turbine wheel and into the inlet to the down pipe. BMW programmed the wastegate to be opened more fully (up to 70% open) during warmup. This keeps the turbo from sucking the heat out of the exhaust gas, so the hot gas gets to the cat and warms it up quickly.

These tricks are how the new N20 engine qualifies for SULEV status. The N55 utilizes the same tricks.

So what does this have to do with an exhaust valve for the muffler? on a turbocharged vehicle, the gas passing through the turbo quiets the exhaust noise down a lot. When the wastegate is open, the exhaust noise is much louder. BMW did not want to turn off some potential buyers with such a loud warm-up. To decrease this effect and also to allow eliminating drone under low load conditions, BMW engineered a muffler that is quieter when the valve is closed and louder when it is open.

So, during start-up the exhaust valve is closed for 55 seconds while the wastegate is open and the engine is in fast cat warm up mode. If the valve were open, the engine will be even louder on start up. After the warmup routing is done, the valve opens. But as many of you have pointed out, the car is quieter at this time. That is because the wastegate is now closed and the turbo is quieting down the exhaust too.

So to summarize, having the exhaust valve open will always make the car louder for any particular engine condition than if the exhaust valve were closed. The BMW OEM exhaust works this way, as does our VS-1 performance exhaust system. Both exhausts can be computer controlled by leaving the motor plugged in. And both can be controlled at any time by remote with our VSC-1 controller.

Very very interesting!
Just one question: when you talk about the kat in the downpipe you mean the pre-kat, isn't it? Because the principal kat is in the middle of the exhaust-line.
Another question: before fixing MPPK I felt significant differences in the "burbles" noise between Confort mode and Sport mode, while now there is almost the same effect. This is due to valve management that is now the same with MPPK, put aside the drive mode?

[RoundelM3]

Originally Posted by DVC

Thanks - the info about the waste gate clears up pretty much everything! Too bad there's no way to get the WG to stay open when so desired (or is there?)
So, as the posted above asked, is there any downside to have the valve open all the time?

You realize that having the WG open will not allow much boost to be produced, right? It allows most of the exhaust to bypass the turbine. Why would you want to do that?

There's no "downside" to having the exhaust open all the time - same thing on the N54 engine, which had 2 turbos, 2 mufflers, and 1 flap.

[DVC]

Originally Posted by roundel335

You realize that having the WG open will not allow much boost to be produced, right? It allows most of the exhaust to bypass the turbine. Why would you want to do that?

There's no "downside" to having the exhaust open all the time - same thing on the N54 engine, which had 2 turbos, 2 mufflers, and 1 flap.

Yeah, good point on the WG... I kinda figured this would be the case.

If no downside to opening the exhaust valve, I think I'll give this a try.

[RoundelM3]

Originally Posted by DVC

Yeah, good point on the WG... I kinda figured this would be the case.

If no downside to opening the exhaust valve, I think I'll give this a try.

Let us know how it works out - I'm considering doing this myself. Particularly interested whether or not it gets too loud when cruising in comfort mode.