[MrZippy]

After plenty of reading on the matter, it seems that there is still some differences in the definition of 29.2 induced lag, throttle response, etc. Since this is a very important issue for us, I'd like to make sure that we all try to agree on some definition of what we think the 29.2 version causes. So, by the end of this thread, we would like to have some statement or two that clearly defines the negative aspects experienced as we drive the cars with this issue. I suggest that for this thread we only comment of our perception of how the car performs and not what we think the engine management computer is doing.

Also, we can use our combined observations to further clarify our mission and to provide a more consistent and unified voice to BMW.

Let see how this goes.....there is bound to be some disagreement, but that's why we need to clarify this.

[slubu]

I like this idea.

[coco_m3]

Um. i have lag.

I drove a 335i a couple months back and it was a rocketship but then after i pay 40k+ for my 135i its not the same, that is called FALSE ADVERTISEMENT!

[MrZippy]

Originally Posted by silverbullet135i

Um. i have lag.

I drove a 335i a couple months back and it was a rocketship but then after i pay 40k+ for my 135i its not the same, that is called FALSE ADVERTISEMENT!

Are you able to describe what you mean by lag?

[shaddai]

Originally Posted by MrZippy

Are you able to describe what you mean by lag?

Silverbullet135 and I (well, our cars) were on the same boat. 4/08 build date.

Description of lag:

With RPM < ~3000:

* push the "go" pedal... car starts to move forward like a 4 banger
* wait ~1 second
* car moves forward like a 6 cyl twin turbo

Regardless of vehicle speed.

[ericsmc83]

^^^ Same build date, same description.

[ezatnova]

So this is going to be Thread Number Two to follow, rather than just sticking to the very well established forty page thread already going?

People's descriptions are well laid out in that thread.

I also already laid out a summary of the impacts to 29.2 cars on the Official Check-In thread.

[kevinbahnz]

where do find the build date? is it on the side of the door jam with the VIn number. cuzz mine says 04/08 also. Does this mean my 335 have the 29.2 software??

[Quisp]

Pre 29.2 the surge in power was felt at 1400-1500 rpm and was immediate when pushing the gas pedal hard. After 29.2 and 30.0.2 or 30.2.0 or whatever that one is, the surge in power is felt at 3000 rpm. So if i hit the gas hard at 1700 rpm, the car does not respond strongly until the tach hits about 3000 rpm, thus giving the feeling of turbo lag.
2007 coupe, 6mt, 9/06 build

[iScream]

It has been a long time since I drove pre-29.2, so it's kind of hard for me to describe it exactly and in great detail. I do remember having more pull between 1500-3000 RPM than I do now. I'll admit it, sometimes I'd gun the throttle about 1/2 to 3/4 open for a second or two, just to get the rush of feeling it pull. I remember it would start pulling extra hard in under a half second.

With 29.2, which I am absolutely certain I now have, gunning the throttle around 2k RPM produces a little surge forward, a 1.6 second wait with a flat level of torque, and then a dramatic increase in torque. It's not quite the thrill it used to be.

Above 3500 RPM, with 29.2 my car performs exactly as I described the pre-29.2 behavior above.

I've tested a theory (one other member had similar results) that the magic number is actually about 3300 RPM. Around 3k RPM, the lag can seem less, but that is only because it naturally takes the car less than a second to get from 3000 to 3300 -- at least that is my observation. Above 3300 RPM, all negative effects of 29.2 disappear.

The car pops like a lawnmower when the throttle is tapped while decelerating. In the first 5 minutes after a cold start, this sound is accompanied by a short rattle from under the hood. The same rattle can be heard as the engine revs down to 3300 RPM from higher revs, regardless of how long the car has been running. I honestly don't remember if pre-29.2 was better in this regard.

Another theory I have is that 29.2 pulls just as much, if not more than pre-29.2, just later. Again, it's tough to remember 3k miles (3 months) ago, but I think pre-29.2 did not initially hit me with as much power after the brief lag. Previously, it was like an animal attacking its prey; quick response with steadily increasing aggression until full intensity a second or two later as it descends upon its victim. Now, under 3300 RPM, it is like a person who forgot the lyrics to a song trying to sing along with someone who does; once its memory is jogged and it remembers how much power it has, it bursts in all at once, too late for the cadence and out of sync. (How's that for a technical analysis?)

Lastly, my fuel efficiency has measurably and consistently dropped by about 4 MPG. This has been tested over several tanks of gas, with little to no change in gas brand/grade or driving style. Now, I may have subconsciously changed my driving style to accommodate for 29.2, thus using more gas, but it is also possible that the engine's current operation just plain uses more gas.

A little more than one or two statements, I know, but as you can see I've tried to put as much objective thought as possible into this. Every day I wonder if it is my imagination, and every day I either discover or reaffirm empirical evidence that it is not.

Edit: I forgot to mention that 3300 RPM is not a "hard and fast" rule. If I gradually depress the accelerator pedal at 2k or even 1k RPM, the car will seem to hit max torque before 3300 RPM. It is mainly when I want instantaneous power that 29.2 thwarts my efforts.

[MrZippy]

Originally Posted by Quisp

Pre 29.2 the surge in power was felt at 1400-1500 rpm and was immediate when pushing the gas pedal hard. After 29.2 and 30.0.2 or 30.2.0 or whatever that one is, the surge in power is felt at 3000 rpm. So if i hit the gas hard at 1700 rpm, the car does not respond strongly until the tach hits about 3000 rpm, thus giving the feeling of turbo lag.
2007 coupe, 6mt, 9/06 build

I doubt that this is real turbo lag -- the time required for the boost to build as the compressor wheel speed is increasing due to the inertia of the wheel -- since we have very small compressors.

So, the lag here is one due to the 29.2 code creating one either by manipulating the wastegates and/or fuel input, and/or throttle response. Sound right?

[Quisp]

Are you referring to the time for the turbo to spool up? That is the big question. Whether it is lag or 29.2 controlling things so that the turbos do not come on until around 3000. Call it lag, call it hesitation, call it whatever you want, I used to push the gas pedal down and the car would respond immediately, after the update it accelerated like an average car until 3000, then you would feel the turbos. Prior to the update he power came on at 1500. This is a comparison with the same style of driving before and after.
This is from a thread that shiv@vishnu started, it is wha he found out after looking into 29.2 and seeing what it does. If you have already seen it i apologize:

Compared to 28.x, 29.2 is very eager to cut throttle (loggable via obd-II reader) if it sees things it doesn't like. What it doesn't like isn't what I expected to see. I had initially expected it to monitor fuel output (short-term fuel trim in particular) and protest when it seems abnormally high fuel consumption (typical when running higher than stock boost). It didn't seem to exhibit this behavior at all.

Instead, most of it seems to cut throttle based upon boost management implausabilities. The tricky bit is that it is not obvious to the driver. When it cuts throttle to 50%, you might only lose 20-50lbft which is certainly noticeable but not entirely obvious. By "boost management implausaiblities" I mean perceived wastegate duty cycle necessary to acheive the boost target. With v3, our PID based boost control system keeps the ECU's perceived duty cycle wherever we want it. With one simple change, we were able to keep throttle from closing whereas before it would spend most of the single gear pull between 40 and 50% throttle.

Those who have OBD loggers and try to datalog actual throttle opening and see if their tune is inducing throttle closure.

Normal throttle opening behavior is as such: Upon WOT, you will see throttle open fully. A fraction of a second later, It may cut back down to 40-60% for a fraction of a second. After that, it should reman wide open until the rest of the run. This is good.

Abnormal throttle opening behavior is as such: Upon WOT, you will see throttle open fully. A fraction of a second later, It may cut back down to 40-60% and stay there for most of the run. You may see spikes upwards as it tries to open the throttle fully (and decides not to). And power will be lowered and reasonably inconsistent. This is not good. Wheather this behavior, or something else (like fuel flow) induces the "manipulation" code remains to be seen soon.

Another change is that wastegate duty during cruise/low load conditions has been lowered to 15-20% instead of 40-50% as with earlier ECU software versions. This makes the turbos feel a bit less responsive as well as makes the exhaust sound a bit louder/burblier.



The link to the thread is:
http://www.e90post.com/forums/showthread.php?t=142298