[drob23]

Originally Posted by roundel335

OK, so to clarify - the wastegate controls how much exhaust gas flows into the turbo versus straight out into the exhaust. It stays open at idle and up to about 1200 RPM, where it is fully closed and all exhaust gas goes into the exhaust. It opens up a bit at the top end to limit the boost (and turbine rpm) so as to keep things from literally going to pieces.

The blowoff/diverter valve (in the intake tract) is used to prevent turbine stall when the throttle closes so that pressurized air is vented to the atmosphere (blowoff valve, usually in racing applications) or back into the pre-compressor intake tract (diverter valve, which our engines have).

Now, to your point, a twin-scroll turbo (with two turbine scrolls and one compressor) will get some advantage over a single-intake scroll model, in that you have two exhaust streams (albeit from less cylinders) providing heat/pressure to drive the compressor. I can't really speak to the physics behind that, but it appears to be more efficient - the two turbines apparently getting the compressor up to speed with less engine rpm than a single. Also, turbine/compressor sizing can make a difference as well, plus we're also dealing with component weights, turbine blade shapes, and then we get into physics about pressure waves and all that. But the simple answer is yes, the twin-scroll turbo used on our N55 engines is more efficient - which is really what the N55 is supposed to be about. "Efficient Dynamics" and such.

Regarding the AT's effect on perceived turbo lag, there's another factor with that trans - kickdown - which can be perceived as lag between stepping on the throttle and the engine/trans response. In sport/sport+ mode, the trans shifts faster both up and down, and this seems to be positively affected with the MPPK in place. When accelerating and keeping a constant throttle opening, there will be some advantage over an MT in terms of keeping boost up (no throttle closing and subsequent boost drop).

Also, another poster was dubious about the new (MPPK) DME software upgrade affecting the steering, and I can only point to the various responses in the thread, and my own experience, that the steering has tightened up since the install of the MPPK. I don't know too much about how the electrically-boosted steering's control mechanisms work, but they are controlled, to some extent, by the DME software.

Once again, appreciate the response and the info. I agree that it is very hard to decouple the issue in these modern cars, with all the software overhead regarding throttle settings (sport/sport+/eco for you, comfort/auto/dynamic for me), shift maps etc. I thought the twin-scroll design uses different geometry between the two inlets to optimize turbo spoll over a wide range of exhaust pressures. Of course achieving this result requires very complex engine control as you've alluded to in the prior posts.

After considering all this, my guess is that ppk helps reduce perceived lag by making the throttle in general much more responsive, rather than changing the waste gate. Maybe a dyno before/after comparison would shine the most light on this, since WOT runs would surely isolate the turbo lag? From my time with the N55, I'd say turbo lag was non-existent, but maybe if I was driving a MT and did a 6-2 downshift it would be noticeable.

[DmitryF30]

Originally Posted by roundel335

Now, to your point, a twin-scroll turbo (with two turbine scrolls and one compressor) will get some advantage over a single-intake scroll model, in that you have two exhaust streams (albeit from less cylinders) providing heat/pressure to drive the compressor. I can't really speak to the physics behind that, but it appears to be more efficient - the two turbines apparently getting the compressor up to speed with less engine rpm than a single.

You are correct - twin scroll makes the turbo more efficient and reduces the lag.

By splitting the exhaust gasses of the engine into two ports, BMW was able to increase pressure differential accross the blades of the turbine. Because of the larger pressure differential kenetic energy of the gasses can be better utilized. Here is what TIS has to say on the issue:

[shivaswrath]

Originally Posted by ft1338

I question the steering feel upgrade with the PPK. Must be coming from another free update. I don't see the steering feel change advertised anywhere in BMW PPK docs.

Question if you like, it's the first thing I noticed and its very real.

I can see it being a PPK only update...remember, BMW is targeting it for enthusiasts that are willing to spend the $1100-2000 to buy/install.

If you're an enthusiast you won't bat an eye about updating the steering that apparently everyone hates...(I actually don't care; my Evo 8 had the most accurate steering I've ever had the joy of driving).

[BmwFlooner]

To the OP (or anyone else with a 335 MT), how's the fuel consumption?

[itwasepic]

Originally Posted by BmwFlooner

To the OP (or anyone else with a 335 MT), how's the fuel consumption?

24.5 MPG and I get a few good, smart accelerations in M Sport+ per trip to/from the office.

[JamesMA]

Originally Posted by shivaswrath

Question if you like, it's the first thing I noticed and its very real.

I can see it being a PPK only update...remember, BMW is targeting it for enthusiasts that are willing to spend the $1100-2000 to buy/install.

If you're an enthusiast you won't bat an eye about updating the steering that apparently everyone hates...(I actually don't care; my Evo 8 had the most accurate steering I've ever had the joy of driving).

I have the PPK installed. I did not notice any difference in the steering.

Don't get me wrong, I want a change in the steering and have been asking about this since I bought the car. It's the only issue with the car IMHO.

Also, I agree the PPK deals with power concerns nicely on a 6MT. No complaints in torque and power on my end.

[DarkTrigger]

Originally Posted by JamesMA

I have the PPK installed. I did not notice any difference in the steering.

Don't get me wrong, I want a change in the steering and have been asking about this since I bought the car. It's the only issue with the car IMHO.

Also, I agree the PPK deals with power concerns nicely on a 6MT. No complaints in torque and power on my end.

I guess my question to you would be do you drive mostly in sport or comfort? It was incredibly apparent to me since I drive all the time in comfort mode and that was my biggest complaint.

[RPM90]

Originally Posted by roundel335

Eliminating lag is all about getting the turbo producing boost at the lowest possible RPM, and eliminating restrictions doesn't really have that much effect until revs get well beyond the 1-2K range, where it is seen at higher/peak boost levels. Does that clear things up a bit?

Can you post the link explaining the details of the PPK tuning and what BMW altered?
Specifically, I'd like to read the info on altered waste gate tuning.

In the older days of turbo-charging, we used to use manual boost controls that could alter/delay when the waste gate would open, thus giving greater boost level, and more power, before opening the waste gate/WG to vent according to the OEM prescribed boost peak.
Yes, it was a very risky tweak, but those were the days before all of the modern ECU controlled systems.

From my experience, reducing certain exhaust restrictions will have much effect on spool up and 'lag'. To reduce lag and gain more power down pipes were and are still very liked, as the increased exhaust flow allows the turbo to spool quicker, especially coupled with less restricted higher flow cats.
Some guys removed the cats completely for best effect, but I'm not a fan or polluting with a daily driver.

Modern systems use electronically controlled waste gates to control max boost pressure and to better control boost for given rpm, load, and gear.
But, I'm still not getting why and how BMW is using waste gate activation to reduce lag at lower RPM, compared to stock.

I can see controlling the WG over the rev range to better control and smooth out boost over the rev range and thus make power delivery more linear.
And, of course the WG is used to limit max boost, as well as being utilized to get more max boost before it opens.

As for lag off the line, to decrease any lag comparing stock to PPK, you're implying that the stock tune would actually be opening the WG as soon as the driver starts to give throttle. And the PPK is keeping the WG closed in the same scenario, in order to build boost quicker.
BMW actually doing this would be contrary to building and tuning a turbo engine with near zero lag. Opening the WG even slightly right off idle would actually create lag and unnecessarily so.

It doesn't make sense to tune the WG to open right off idle with either auto trans or manual, and would be even worse for MT as the clutch needs to be engaged in order to build adequate exhaust pressure to spin the turbo in the first place. Giving throttle while in neutral or with the clutch disengaged results in very little boost build.

Your thoughts?
Help me understand how BMW have altered the WG to reduce lag, especially on take off, right off idle.

[RPM90]

Originally Posted by drob23

Thank you, this response was much more thoughtful than the last one. I definitely appreciate the insight into how things work from someone who works on engines.

My uneducated understanding was that the wastegate/blowoff valve function to (a) protect the engine from overboosting at high RPM; (b) relieve boost after up-shifting; (c) remove boost when downshifting to engine brake.

(1) Why would the wastegate setting, at the 1-2k end where lag would be most perceived, be set to open up and reduce boost? You are saying this is due to emissions? But at higher RPM's the ECU allows for more boost?

Another interesting question is whether or not an AT will remove turbo lag by maintaining higher engine RPM's through TCU software and the physics of the torque converter, while a MT is more likely to experience it due to rev-matching a downshift, 6-3 for example.

The waste gate's fundamental role is to open and allow the exhaust to bypass the compressor side of the turbo, in order to stop the turbo from pressurizing the intake any further. At it's base function the WG will open once intake boost pressure has exceeded the maximum boost level.
The WG can also be computer controlled so that it opens and closes even before the max boost pressure is reached. This can be done to limit boost pressure within a certain rpm range, load, or gear, can can be used to smooth out power delivery.

To release the pressurized air during a shift that's the job of a "blow off" valve. These come in two varieties.
One is a "recirculating valve" and the other is "vented" valve.
The"diverter valve" allows the pressurized air back into the intake stream. And if done properly will put that air right in the path of the compressor side of the turbo and can help lessen the effect of boost drop especially on fast shifts. A "vented" blow off valve opens to release the pressurized air to the atmosphere. Vented blow off valves make that cool "Phssst" sound.
Diverter valves make virtually no sound.
I love the sound of atmosphere vented blow off valves.

Auto trans has the added benefit of holding boost during shifts as the trans is constantly coupled to the engine, and the driver doesn't have to lift/close throttle in between shifts as one does when driving a manual clutch trans.
Dual clutch AT's can also hold boost, or not loose as much boost, in between shifts because the shift happens very quickly and the driver doesn't have to lift throttle in between shifts.

[RPM90]

Originally Posted by JamesMA

I have the PPK installed. I did not notice any difference in the steering.

Don't get me wrong, I want a change in the steering and have been asking about this since I bought the car. It's the only issue with the car IMHO.

Also, I agree the PPK deals with power concerns nicely on a 6MT. No complaints in torque and power on my end.

The steering and soft sport suspension are the biggest let downs with the F30.
I can't say which is a bigger let down. I do know that with both combined BMW created a big let down for BMW "SPORT" sedan lovers.

My 335i Msport was built in July and there have been at least 2 new revisions/different steering racks, and I read there is yet another one coming soon probably for the 2014 models.
Some have said that the new racks have improved steering effort and feel.
My 2013 335i isn't even a year old and it already has an outdated steering rack.
This F30 sure is something new.

BMW

[F30form]

Originally Posted by RPM90

Can you post the link explaining the details of the PPK tuning and what BMW altered?
Specifically, I'd like to read the info on altered waste gate tuning.

In the older days of turbo-charging, we used to use manual boost controls that could alter/delay when the waste gate would open, thus giving greater boost level, and more power, before opening the waste gate/WG to vent according to the OEM prescribed boost peak.
Yes, it was a very risky tweak, but those were the days before all of the modern ECU controlled systems.

From my experience, reducing certain exhaust restrictions will have much effect on spool up and 'lag'. To reduce lag and gain more power down pipes were and are still very liked, as the increased exhaust flow allows the turbo to spool quicker, especially coupled with less restricted higher flow cats.
Some guys removed the cats completely for best effect, but I'm not a fan or polluting with a daily driver.

Modern systems use electronically controlled waste gates to control max boost pressure and to better control boost for given rpm, load, and gear.
But, I'm still not getting why and how BMW is using waste gate activation to reduce lag at lower RPM, compared to stock.

I can see controlling the WG over the rev range to better control and smooth out boost over the rev range and thus make power delivery more linear.
And, of course the WG is used to limit max boost, as well as being utilized to get more max boost before it opens.

As for lag off the line, to decrease any lag comparing stock to PPK, you're implying that the stock tune would actually be opening the WG as soon as the driver starts to give throttle. And the PPK is keeping the WG closed in the same scenario, in order to build boost quicker.
BMW actually doing this would be contrary to building and tuning a turbo engine with near zero lag. Opening the WG even slightly right off idle would actually create lag and unnecessarily so.

It doesn't make sense to tune the WG to open right off idle with either auto trans or manual, and would be even worse for MT as the clutch needs to be engaged in order to build adequate exhaust pressure to spin the turbo in the first place. Giving throttle while in neutral or with the clutch disengaged results in very little boost build.

Your thoughts?
Help me understand how BMW have altered the WG to reduce lag, especially on take off, right off idle.

This is based off of one person's opinion. I would research further before taking it as gospel. For instance, maybe the tune gave the car more more advance, thus making it more aggressive off idle sooner and spooling the turbo sooner? It's all hearsay anyway. The proof is in the driving.

[RoundelM3]

Originally Posted by RPM90

Can you post the link explaining the details of the PPK tuning and what BMW altered?
Specifically, I'd like to read the info on altered waste gate tuning.

In the older days of turbo-charging, we used to use manual boost controls that could alter/delay when the waste gate would open, thus giving greater boost level, and more power, before opening the waste gate/WG to vent according to the OEM prescribed boost peak.
Yes, it was a very risky tweak, but those were the days before all of the modern ECU controlled systems.

From my experience, reducing certain exhaust restrictions will have much effect on spool up and 'lag'. To reduce lag and gain more power down pipes were and are still very liked, as the increased exhaust flow allows the turbo to spool quicker, especially coupled with less restricted higher flow cats.
Some guys removed the cats completely for best effect, but I'm not a fan or polluting with a daily driver.

Modern systems use electronically controlled waste gates to control max boost pressure and to better control boost for given rpm, load, and gear.
But, I'm still not getting why and how BMW is using waste gate activation to reduce lag at lower RPM, compared to stock.

I can see controlling the WG over the rev range to better control and smooth out boost over the rev range and thus make power delivery more linear.
And, of course the WG is used to limit max boost, as well as being utilized to get more max boost before it opens.

As for lag off the line, to decrease any lag comparing stock to PPK, you're implying that the stock tune would actually be opening the WG as soon as the driver starts to give throttle. And the PPK is keeping the WG closed in the same scenario, in order to build boost quicker.
BMW actually doing this would be contrary to building and tuning a turbo engine with near zero lag. Opening the WG even slightly right off idle would actually create lag and unnecessarily so.

It doesn't make sense to tune the WG to open right off idle with either auto trans or manual, and would be even worse for MT as the clutch needs to be engaged in order to build adequate exhaust pressure to spin the turbo in the first place. Giving throttle while in neutral or with the clutch disengaged results in very little boost build.

Your thoughts?
Help me understand how BMW have altered the WG to reduce lag, especially on take off, right off idle.

Either I mistyped or you misread - there's no implication that the stock software opens the WG as soon as the throttle opens. The WG is open at idle and then gradually closes - at least, that's how it was on my N54. There were a lot of "lag" complaints with that engine after BMW changed its base software to close the WG at a higher RPM as part of a "fix" for the HPFP problem - check the E90Post forum for some background on that. My suggestion is that if anything, the MPPK closes the wastegate a little earlier to develop boost sooner - although I really didn't feel any lag with my car before the MPPK was installed. I do have a recent build - January 2013 - so it's possible that the newer DME was responsible rather than the MPPK.

[drob23]

Originally Posted by roundel335

Either I mistyped or you misread - there's no implication that the stock software opens the WG as soon as the throttle opens. The WG is open at idle and then gradually closes - at least, that's how it was on my N54. There were a lot of "lag" complaints with that engine after BMW changed its base software to close the WG at a higher RPM as part of a "fix" for the HPFP problem - check the E90Post forum for some background on that. My suggestion is that if anything, the MPPK closes the wastegate a little earlier to develop boost sooner - although I really didn't feel any lag with my car before the MPPK was installed. I do have a recent build - January 2013 - so it's possible that the newer DME was responsible rather than the MPPK.

I think his question was a much better articulated version of mine. The simple question is whether or not MPPK can reduce turbo lag at low RPM.

My hypothesis is no based on:
1) MPPK would not retard timing at low RPM to increase exhaust pressure because this could hurt the engine, and honestly, why would you care about turbo lag at low RPM for a high performance tune?
2) The main increase in performance is in the higher RPM band, where the track driver would be anyways and the stock overboost protection is overly conservative - stock dyno runs show pretty dramatic torque drop above ~5.5k RPM.
3) You have the 8AT and probably experience a lot less lag. If there was one area I think BMW powertrain engineers really knocked it out of the park, it was tuning the ZF8.

Edit - re-read and specifically curious why the waste gate would be open at idle and gradually close? You say this is for the N54, but I'm not sure why this would be the case with the N55...

[Jamesons Viggen]

Originally Posted by RPM90

The steering and soft sport suspension are the biggest let downs with the F30.
I can't say which is a bigger let down. I do know that with both combined BMW created a big let down for BMW "SPORT" sedan lovers.

My 335i Msport was built in July and there have been at least 2 new revisions/different steering racks, and I read there is yet another one coming soon probably for the 2014 models.
Some have said that the new racks have improved steering effort and feel.
My 2013 335i isn't even a year old and it already has an outdated steering rack.
This F30 sure is something new.

BMW

BMW should retro-fit for owners who complain. I wish.

[RoundelM3]

Originally Posted by drob23

I think his question was a much better articulated version of mine. The simple question is whether or not MPPK can reduce turbo lag at low RPM.

My hypothesis is no based on:
1) MPPK would not retard timing at low RPM to increase exhaust pressure because this could hurt the engine, and honestly, why would you care about turbo lag at low RPM for a high performance tune?
2) The main increase in performance is in the higher RPM band, where the track driver would be anyways and the stock overboost protection is overly conservative - stock dyno runs show pretty dramatic torque drop above ~5.5k RPM.
3) You have the 8AT and probably experience a lot less lag. If there was one area I think BMW powertrain engineers really knocked it out of the park, it was tuning the ZF8.

Edit - re-read and specifically curious why the waste gate would be open at idle and gradually close? You say this is for the N54, but I'm not sure why this would be the case with the N55...

Not really saying anything of the sort - I'm speculating that BMW changed the wastegate close to a slightly lower RPM - or maybe not. When the N54 began having HPFP failures, BMW revised the DME software to have the low-pressure pump prime the high-pressure pump when ever the car was "waked up" (door opening, unlocking, etc.) and they also raised the rpm at which the wastegate closed completely. Why they have the gate open at idle is a question they'd have to answer, but if you read the posts, you'll also see some issues with wastegate actuators rattling, and apparently raising the rpm was part of an attempt to limit wastegate rattle. They also ended up replacing a lot of twin-turbo setups because of that problem. Nonetheless, it is within the DME's purview to decide when the wastegate closes and opens, and they did in fact raise the rpm at which it closed, resulting in much-bitched-about lag. They may or may not have lowered the RPM for wastegate close on the N55, but my point was that it is possible they did so.

[JamesMA]

Originally Posted by DarkTrigger

I guess my question to you would be do you drive mostly in sport or comfort? It was incredibly apparent to me since I drive all the time in comfort mode and that was my biggest complaint.

I drive in everything but Ecco mode regularly (I have never used Ecco). Post MPPK install, throttle and torque are much improved in comfort (most notable), sport and sport+.

Steering feels exactly the same.

[DarkTrigger]

Originally Posted by RPM90

The waste gate's fundamental role is to open and allow the exhaust to bypass the compressor side of the turbo, in order to stop the turbo from pressurizing the intake any further. At it's base function the WG will open once intake boost pressure has exceeded the maximum boost level.
The WG can also be computer controlled so that it opens and closes even before the max boost pressure is reached. This can be done to limit boost pressure within a certain rpm range, load, or gear, can can be used to smooth out power delivery.

To release the pressurized air during a shift that's the job of a "blow off" valve. These come in two varieties.
One is a "recirculating valve" and the other is "vented" valve.
The"diverter valve" allows the pressurized air back into the intake stream. And if done properly will put that air right in the path of the compressor side of the turbo and can help lessen the effect of boost drop especially on fast shifts. A "vented" blow off valve opens to release the pressurized air to the atmosphere. Vented blow off valves make that cool "Phssst" sound.
Diverter valves make virtually no sound.
I love the sound of atmosphere vented blow off valves.

Auto trans has the added benefit of holding boost during shifts as the trans is constantly coupled to the engine, and the driver doesn't have to lift/close throttle in between shifts as one does when driving a manual clutch trans.
Dual clutch AT's can also hold boost, or not loose as much boost, in between shifts because the shift happens very quickly and the driver doesn't have to lift throttle in between shifts.

So you're saying we do have a Blow off valve to atmosphere? I got totally thrashed awhile back for saying that, everyone corrected me saying it was the recirculating valve.

[DarkTrigger]

Originally Posted by JamesMA

I drive in everything but Ecco mode regularly (I have never used Ecco). Post MPPK install, throttle and torque are much improved in comfort (most notable), sport and sport+.

Steering feels exactly the same.

I think we need a poll. However, I don't think enough people have the MPPK yet.

[RPM90]

Originally Posted by DarkTrigger

So you're saying we do have a Blow off valve to atmosphere? I got totally thrashed awhile back for saying that, everyone corrected me saying it was the recirculating valve.

No. We do have a "blow off" valve, but it is a "recirculating" type, not an "atmospheric" type.

"Blow off" valve is the general term, "Recirc" and "atmosphere" describe where the pressurized air is being "blown off" to.

[DarkTrigger]

Originally Posted by RPM90

No. We do have a "blow off" valve, but it is a "recirculating" type, not an "atmospheric" type.

"Blow off" valve is the general term, "Recirc" and "atmosphere" describe where the pressurized air is being "blown off" to.

Damn, where were you when I was getting ripped a new one in my thread?? LoL, oh well.

[300hp]

Originally Posted by DarkTrigger

I think we need a poll. However, I don't think enough people have the MPPK yet.

I have the mppk count me in with those who experienced a change in steering feel especially in comfort mode.

Maybe it also depends on the packages on the 335i before mppk.

[itwasepic]

Originally Posted by DarkTrigger

I think we need a poll. However, I don't think enough people have the MPPK yet.

+1