[oc24]

I still am not 100% sure what exactly turbo lag feels like, and if my MSD81 has this lag. Let's say I'm driving at around 1500 rpms, if I gradually push down on the throttle, my car goes accordingly...slowly accelerating. Now say I go WOT at 1500 rpms in 2nd gear, there is a slight response, then 1 second later boom I go.

So I guess my question is to those who are pre 29.2, when you go WOT at 1500rpms, does the car just go instantly like an NA engine? I also found something on wiki regarding boost threshold, so I'm even more confused. Finally, the fact that BMW says full boost is available at 1400rpms, what does that mean exactly? To me, it means that the ability to accelerate at 1400rpms is the same at 5000rpms, although my car does NOT act that way at all.

[oc24]

I have a 6MT

[iScream]

Originally Posted by slubu

I have a 6MT

me too. I've posted enough details on my 29.2 lag that you can find a lot of info in my other posts, but basically if you are waiting 1 second or longer, then IMO you have the lag.

Some people do not have it, or are not aware they have it either because they drive AT or they never had pre-29.2. I am trying to figure out if there are any commonalities between those of us who have it. For example, I have iDrive, NAV, sport, premium, and I picked up my car via ED. So I did get to drive it fairly "aggressively" during the break-in period, or at least moreso than is legal in the US. It's possible that WOT driving during the adaptation period makes it into a stronger car. However, I had my adaptations reset again several weeks after 29.2, and tried (within reason and mostly within the law) to get the car to think I was a bad-ass again, but I still have the lag. So that kind of busts that theory, which to date has been BMW's best solution for my PUMA case.

Also I did have a bad HPFP, and am running on a replaced one now. The car drove fine after the replacement, until the software update.

Pre-29.2 was a few thousand miles ago for me, so I'm starting to forget exactly what it felt like. However, I do distinctly remember being able to get noticeable turbo response well within 0.5s below 2k rpm in 2nd, 3rd, and 4th gears, which is no longer possible. Now with 29.2, when I cruise around 3500 rpm and then floor it, it responds the way it used to from 1500 on up.

Lastly, there is always the possibility that 29.2 does not CAUSE the problem, but rather it (or the system reset) exposes a problem that was already present. So I am careful not to sound like a know-it-all to my SA, because all I can really say for sure is that the car does not drive like it used to.

I really wish they were allowed to downgrade the car, just so we could determine with absolute certainty whether or not it is something in 29.2. If it fixes it, then there would only be so many things that could be the culprit, and then they could probably fix everyone else's a lot faster.

HTH.

[JOe335i]

some people mix, the heavy tq coming in at 1500 rpm as a sign of lag... turbo lag is a the lag of the turbo coming on or peaking, the 335i almost peaks instantly right off the bat at 1500rpm, but lets not forget we are speaking flywheel numbers and not RW-RPM's.

again dont confuse the peak boost and full tq rush at 1500 as a OMG there was alot of turbo lag and then boom the power comes on, its just the 300 ft lb coming on hard... its aint turbo lag, its how the powerband is on this car.

[rdsport323]

placebo effect

[iScream]

I am amazed at how many people apparently think the 29.2 complainants (myself included) are complete idiots who wouldn't know the difference between our own cars and VTEC.

I drove the car for 15k miles in just about every condition, and at every speed and RPM level of which it is capable. I got to know it well. When I picked it up from my 15k service, I noticed a peculiar lag in its throttle response. At first, I thought, "no that can't be possible, must be my imagination" but over a couple weeks I realized it was apparent and persistent enough that I could no longer ignore it. See one of my first posts here:

http://www.e90post.com/forums/showth...05#post2815305

Only then did I search this board to find that others independently had the same experience. Placebos do not work that way! You can see that I was one of the first on the 29.2 check-in thread, and I did not really hang out here much until this 29.2 debacle.

I see your "placebo" and raise you one "denial", an "ignorance" and a healthy dose of "maybe some of you were lucky enough not to have this problem." But please don't tell me it doesn't exist, because you don't know.

[scalbert]

It is a combination of throttle response and boost threshold.

Throttle Response: The delay from when you apply throttle to when the vehicle responds. All vehicles, including normally aspirated, have some form of throttle response. Also, if you floor a normally aspirated vehicle at 1500 RPM, it will respond differently than doing so at 4k revs. That is just the nature of the engine setup and is the same for a turbo vehicle.

Boost Threshold: This is the lowest RPM at which there is sufficient exhaust energy to create boost. This will not be the point at which peak boost (and typically peak torque) occurs. This is the minimum RPM at which you start building boost. Again, flooring it at 1500 will cause a delay due to throttle response and then hitting the boost threshold. At which point the car will beginning accelerating faster until peak torque is reached.

The reason for mentioning the above is to identify what many are referring to as lag. To do so you need to identify the RPM you are witnessing an issue. If someone is experiencing lag and is above the boost threshold, then it falls into throttle response. What would cause the throttle response to be longer? Perhaps the wastegate is being held open longer and there is a delay in it closing when throttle is applied.

However, if you are flooring it at 2k revs and boost starts building but it takes time before reaching peak torque. That would fall into being below boost threshold.

[RMA]

After having the SSTT installed last Friday nite I can tell a huge difference in power. I must have had turbo lag as well being mine is a late model 08'.

[jpsimon]

some of you need to drive other turbo cars... then you'll see what turbo lag is.

[dmboone25]

Originally Posted by jpsimon

some of you need to drive other turbo cars... then you'll see what turbo lag is.

Touche'

You are right, from a certain point of view. But, as far as I am concerned, I shouldn't have to worry about lag because my car was MARKETED as having no lag at all. The car I test drove, and thus made my purchasing decision upon, had no noticeable lag. So, I order one, thinking that I will get the same thing. My car shows up 2 months later--but it is NOT the same car that I test drove. Much more noticeable lag--and I have a 6 MT....

All I am saying is that I should get what I paid for, and that they should have delivered to me what I thought I was buying. BMW has fallen short on both accounts.

[scalbert]

Originally Posted by dmboone25

Touche'

You are right, from a certain point of view. But, as far as I am concerned, I shouldn't have to worry about lag because my car was MARKETED as having no lag at all. The car I test drove, and thus made my purchasing decision upon, had no noticeable lag. So, I order one, thinking that I will get the same thing. My car shows up 2 months later--but it is NOT the same car that I test drove. Much more noticeable lag--and I have a 6 MT....

All I am saying is that I should get what I paid for, and that they should have delivered to me what I thought I was buying. BMW has fallen short on both accounts.

What portion of the year did you test drive the car? Was the A/C on? The A/C and the current heat during summer will decrease throttle response.

The car was marketed as have virtually no lag or less than typical but not completely absent.

[dmboone25]

Originally Posted by scalbert

What portion of the year did you test drive the car? Was the A/C on? The A/C and the current heat during summer will decrease throttle response.

The car was marketed as have virtually no lag or less than typical but not completely absent.

Test drove the demo 135--this was in March 2008. It was probably 55 degrees out....no A/C on at all. AND it was an AT.

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[scalbert]

Originally Posted by dmboone25

Test drove the demo 135--this was in March 2008. It was probably 55 degrees out....no A/C on at all. AND it was an AT.
By combining twin turbochargers with BMW"s direct fuel injection system and advanced piezo injector technology, we achieved the benefits of turbocharging without the drawbacks, namely poor fuel efficiency and turbo lag. In fact, we eliminated turbo lag altogether.

I stand corrected.

Looks like marketing overstated the laws of physics. Not the first time this has happened in history.

Some previous literature I read added virtually eliminates which is a better choice of words and can please the legal department as well.

That said, there is no way to eliminate but it can be reduced. My point was that all things need to be considered. Seeing your location and a test drive in March, I assume the weather was significantly different. The warmer weather slows everything. I am not saying there is not an issue. But considerations should be made to other possibilities or at least; other possibilities which could amplify and issue.

[BlueLion]

Originally Posted by scalbert

It is a combination of throttle response and boost threshold.

Throttle Response: The delay from when you apply throttle to when the vehicle responds. All vehicles, including normally aspirated, have some form of throttle response. Also, if you floor a normally aspirated vehicle at 1500 RPM, it will respond differently than doing so at 4k revs. That is just the nature of the engine setup and is the same for a turbo vehicle.

Boost Threshold: This is the lowest RPM at which there is sufficient exhaust energy to create boost. This will not be the point at which peak boost (and typically peak torque) occurs. This is the minimum RPM at which you start building boost. Again, flooring it at 1500 will cause a delay due to throttle response and then hitting the boost threshold. At which point the car will beginning accelerating faster until peak torque is reached.

The reason for mentioning the above is to identify what many are referring to as lag. To do so you need to identify the RPM you are witnessing an issue. If someone is experiencing lag and is above the boost threshold, then it falls into throttle response. What would cause the throttle response to be longer? Perhaps the wastegate is being held open longer and there is a delay in it closing when throttle is applied.

However, if you are flooring it at 2k revs and boost starts building but it takes time before reaching peak torque. That would fall into being below boost threshold.

Thanks

[oc24]

Originally Posted by scalbert

It is a combination of throttle response and boost threshold.

Throttle Response: The delay from when you apply throttle to when the vehicle responds. All vehicles, including normally aspirated, have some form of throttle response. Also, if you floor a normally aspirated vehicle at 1500 RPM, it will respond differently than doing so at 4k revs. That is just the nature of the engine setup and is the same for a turbo vehicle.

Boost Threshold: This is the lowest RPM at which there is sufficient exhaust energy to create boost. This will not be the point at which peak boost (and typically peak torque) occurs. This is the minimum RPM at which you start building boost. Again, flooring it at 1500 will cause a delay due to throttle response and then hitting the boost threshold. At which point the car will beginning accelerating faster until peak torque is reached.

The reason for mentioning the above is to identify what many are referring to as lag. To do so you need to identify the RPM you are witnessing an issue. If someone is experiencing lag and is above the boost threshold, then it falls into throttle response. What would cause the throttle response to be longer? Perhaps the wastegate is being held open longer and there is a delay in it closing when throttle is applied.

However, if you are flooring it at 2k revs and boost starts building but it takes time before reaching peak torque. That would fall into being below boost threshold.

Thank you Scalbert. On your car, if you floor it at 2k rpms, what happens? Do you get the same feeling as if you floor it at 4k rpms? This is what I can't figure out...if my car and the pre-29.2 cars differ in this respect.

[Mr. 5]

Drive an e46 M3.
Then drive a 335i.
Then you will know what lag is all about.

Of course, the e46 is NA and the 335 is FI, but the best way I can expalin lag in leman's terms is:

When you step on the gas, lag is the time it takes for the full power of the engine to appear. Lag happens in FI engines when the turbos go from the state of not spooling to spooling. The quicker the spool up the less lag you will get.
Bigger turbos have more lag than smaller turbos because it takes more time and energy to spool a bigger component.

[scalbert]

Originally Posted by slubu

Thank you Scalbert. On your car, if you floor it at 2k rpms, what happens? Do you get the same feeling as if you floor it at 4k rpms? This is what I can't figure out...if my car and the pre-29.2 cars differ in this respect.

There is a significant difference when I floor it at 4k revs versus 2k. At 2k, we first have to wait on the throttle response and then the power builds gradually as we are at or near the boost threshold. At 4k revs the delay is significantly less as now we are just dealing with throttle response.

[iScream]

Originally Posted by jpsimon

some of you need to drive other turbo cars... then you'll see what turbo lag is.

Maybe some do, but not me. I've driven turbo cars before, and pre-29.2 felt like something in between NA and turbo. 29.2 feels like a turbo -- not the worst one ever, but still like a regular turbo. I've never bought into the "eliminates turbo lag" marketing, and never expected it to be totally eliminated.

Hell, what we're talking about might not even technically be turbo lag. I don't care what it is. The car is less responsive than before. My BMW shop foreman, who sat next to me in the car while I demonstrated, confirmed it. But I guess I should defer to the opinion of someone on the Internet who automatically assumes I don't know what I am talking about.

Yes, the OP did ask about turbo lag in general, but it's clear he's mainly trying to figure out if his 335i is neutered, because he does not have much experience with other turbos or pre-29.2 335i's.

[oc24]

Originally Posted by Mr. 5

When you step on the gas, lag is the time it takes for the full power of the engine to appear.

Can lag appear at any RPM? This is my main question. On a one big turbo car, is there lag going WOT at 4k rpm?

Originally Posted by scalbert

There is a significant difference when I floor it at 4k revs versus 2k. At 2k, we first have to wait on the throttle response and then the power builds gradually as we are at or near the boost threshold. At 4k revs the delay is significantly less as now we are just dealing with throttle response.

I think this is the heart of my question, so basically, those with the 29.2 lag still have a delayed response at 4k rpm too?

Originally Posted by iScream

Yes, the OP did ask about turbo lag in general, but it's clear he's mainly trying to figure out if his 335i is neutered, because he does not have much experience with other turbos or pre-29.2 335i's.

Pretty much right on the head here. So on your car, at 4k rpms, you do not have response within 0.5 seconds if you floor it?

[scalbert]

Originally Posted by slubu

Can lag appear at any RPM? This is my main question. On a one big turbo car, is there lag going WOT at 4k rpm?



I think this is the heart of my question, so basically, those with the 29.2 lag still have a delayed response at 4k rpm too?



Pretty much right on the head here. So on your car, at 4k rpms, you do not have response within 0.5 seconds if you floor it?

Yes, lag can occur at any RPM. However, the amount varies based on RPM which is why I specified the two areas which influence the lag.

Pre and post 29.2 have lag at 4k revs and is due to throttle response. However, and from what I have seen, the increased delay (slowed throttle response) with 29.2 is due to the wastegates being held open; it takes a moment for them to close and then the exhaust gases to build pressure behind the turbine wheel. Apparently pre-29.2 held the wastegates closed in most cases which would allow for quicker throttle response.

[e90AW335i]

Originally Posted by scalbert

Yes, lag can occur at any RPM. However, the amount varies based on RPM which is why I specified the two areas which influence the lag.

Pre and post 29.2 have lag at 4k revs and is due to throttle response. However, and from what I have seen, the increased delay (slowed throttle response) with 29.2 is due to the wastegates being held open; it takes a moment for them to close and then the exhaust gases to build pressure behind the turbine wheel. Apparently pre-29.2 held the wastegates closed in most cases which would allow for quicker throttle response.

+1.

29.2 holds the wastegates open further than the previous progmans so that the wastegates dont rattle against the turbo housing. Because of this it increases lag like Steve just explained above.

[Mr. 5]

Originally Posted by slubu

Can lag appear at any RPM? This is my main question. On a one big turbo car, is there lag going WOT at 4k rpm?

This is what you need to think about.
Lag can happen at any RPM.
It happens when you go from off throttle or barely off throttle to WOT.
If you're WOT at 2k rpm and let off at 6k rpm, then you will not feel lag at 4k rpm because your turbos are already spooling and you are acclerating.

Let's say you're driving on the freeway. You're just cruising at 80 in 5th gear, but then you go WOT. You will most likely fee some lag for the turbo to spool.
Turbos are not spooling at all times. You only use turbos when you accelerate.
This is why there is lag with a turbo and not a supercharger.
Superchargers run all the time and increase boost as the engine acclerates.
This is one of the reasons why we get such good freeway mpg.