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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Can you explain "turbo lag" to a novice?



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      08-06-2008, 12:32 PM   #23
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Quote:
Originally Posted by slubu View Post
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?
You got a good answer to your any RPM question, which hopefully should clear things up for some.

Please allow me to explain the test I did this morning. I accelerated above 2k rpms, let off the pedal to just below 2k, and then floored it. I then accelerated above 3500 RPM, let off the pedal to just below 3500 and floored it. Then I analyzed the video frame by frame. At 2k RPM it took 1.6 seconds to go to full boost. At 3500, it was under 0.5s. I honestly don't remember if 3500 was more responsive before 29.2, and besides it'd be pretty tough to discern between say 0.1s and 0.47s when you don't spend a lot of time flooring it at those tach levels. But I am pretty damn certain that 2k was not anywhere near 1.6 seconds before 29.2.
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      08-06-2008, 12:45 PM   #24
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Quote:
Originally Posted by iScream View Post
You got a good answer to your any RPM question, which hopefully should clear things up for some.

Please allow me to explain the test I did this morning. I accelerated above 2k rpms, let off the pedal to just below 2k, and then floored it. I then accelerated above 3500 RPM, let off the pedal to just below 3500 and floored it. Then I analyzed the video frame by frame. At 2k RPM it took 1.6 seconds to go to full boost. At 3500, it was under 0.5s. I honestly don't remember if 3500 was more responsive before 29.2, and besides it'd be pretty tough to discern between say 0.1s and 0.47s when you don't spend a lot of time flooring it at those tach levels. But I am pretty damn certain that 2k was not anywhere near 1.6 seconds before 29.2.
Ok, then I definitely do have the lag, because when I do that I have the same result. That was my sole and only question. Pre 29.2 guys, do you have this same result when you do this? If not, then now I know what the difference is between your cars and ours.
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      08-06-2008, 12:54 PM   #25
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Quote:
Originally Posted by slubu View Post
Pre 29.2 guys, do you have this same result when you do this? If not, then now I know what the difference is between your cars and ours.
Can't help there, not stock and that will influence the behavior.
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      08-06-2008, 12:59 PM   #26
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Lag = over rated.

Other than the technical explanations. Lag is something that is given way to much importance. The 335 has a very quick spool up due to the size of the turbo's, so it takes minimal load (throttle, exhaust pressure, etc...) to get them going.

On another car with a large or larger turbo's you may have position yourself in the cars power band, like down shift for example.

Many people may express a feeling of lag with a 335 that is tuned because your are no longer building 8psi. So you get used to a stock car that builds 8 psi rather quickly. Now obviously it will take a tad bit longer to build full boost if you are building ~12+ psi. That is all.

In other words you get used to the early spike then the taper of the stock turbo's and boost level. Now that feeling is moved slightly higher up in the power band.

Disclaimer: Different tuning maps may offer a slightly different feeling, since different tuners may have a more or less aggressive boost, fuel, and timing maps compared to stock and other tuners maps.
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      08-06-2008, 01:02 PM   #27
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Quote:
Originally Posted by scalbert View Post
Can't help there, not stock and that will influence the behavior.
+1, haven't been stock since 500 miles on the clock....
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      08-06-2008, 01:10 PM   #28
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Quote:
Originally Posted by slubu View Post
Ok, then I definitely do have the lag, because when I do that I have the same result. That was my sole and only question. Pre 29.2 guys, do you have this same result when you do this? If not, then now I know what the difference is between your cars and ours.
Well, the easiest way to tell is to drive a pre v81/29.2 and a v81/29.2 equipped car back to back. That's how I was able to tell--and there IS a difference.

Edit: The easiest way for me to describe the lag is like a hesitation--bigger hesistation in the 29.2 car--before you are pushed back in your seat--longer amount of time.
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      08-06-2008, 01:13 PM   #29
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Quote:
Originally Posted by scalbert View Post
Can't help there, not stock and that will influence the behavior.
Quote:
Originally Posted by e90AW335i View Post
+1, haven't been stock since 500 miles on the clock....
Just curious, with your tunes is there more or less "lag feel"?
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      08-06-2008, 01:20 PM   #30
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Quote:
Originally Posted by slubu View Post
Just curious, with your tunes is there more or less "lag feel"?
Not sure which tune e90AW335i is running right now but I believe the JB3 is supposed to address the lag feel.

How does the beta JB3 handle the lag?
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      08-06-2008, 01:22 PM   #31
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Quote:
Originally Posted by slubu View Post
Just curious, with your tunes is there more or less "lag feel"?
Mine is similar to stock when you consider the increased boost and the time it takes to get to that higher level.
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      08-06-2008, 01:22 PM   #32
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Quote:
Originally Posted by dmboone25 View Post
Not sure which tune e90AW335i is running right now but I believe the JB3 is supposed to address the lag feel.

How does the beta JB3 handle the lag?
Smartass....

Boost with the JB3 comes on quick but of course there is a small lag between when you got WOT and when you get full boost. It is hardly noticable but it is there if you pay attention.
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      08-06-2008, 01:22 PM   #33
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Quote:
Originally Posted by scalbert View Post
Mine is similar to stock when you consider the increased boost and the time it takes to get to that higher level.
+1, exactly
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      08-06-2008, 01:23 PM   #34
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Quote:
Originally Posted by e90AW335i View Post
Smartass....

Boost with the JB3 comes on quick but of course there is a small lag between when you got WOT and when you get full boost. It is hardly noticable but it is there if you pay attention.
Well buddy--I think you have just about had them all at this point.

As long as the lag is more like stock-pre 29.2, I will be happy. And that is kind of what I have seen on various posts.
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      08-06-2008, 01:26 PM   #35
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Personally, I think it's funny when people talk about turbo lag on this car.
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      08-06-2008, 01:28 PM   #36
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Quote:
Originally Posted by AWD Addict View Post
Personally, I think it's funny when people talk about turbo lag on this car.
Drive a car pre v81/29.2 and then one with those, and you might not think it is so funny.
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      08-06-2008, 01:28 PM   #37
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Quote:
Originally Posted by dmboone25 View Post
Well buddy--I think you have just about had them all at this point.

As long as the lag is more like stock-pre 29.2, I will be happy. And that is kind of what I have seen on various posts.
Thanks? Hopefully my comparasions have been of some help to everyone. Mr. 5 and I have that in common except he has had more tunes that I....
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      08-06-2008, 01:30 PM   #38
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Quote:
Originally Posted by Active Autowerke II View Post

Disclaimer: Different tuning maps may offer a slightly different feeling, since different tuners may have a more or less aggressive boost, fuel, and timing maps compared to stock and other tuners maps.
Which is exactly what people with 29.2 are complaining about not, actual turbo lag as in the ability of the turbo to spool. Obviously if you had no detectable lag before and do after a software update it's the way the computer is controlling boost causing that not that the actual turbo can't spool up in the same amount of time.
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      08-06-2008, 01:34 PM   #39
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Quote:
Originally Posted by e90AW335i View Post
Thanks? Hopefully my comparasions have been of some help to everyone. Mr. 5 and I have that in common except he has had more tunes that I....
Seriously--they have been. I have never tried to tune any car I have ever owned, and it makes me a little nervous. Getting answers from people who have more experience is a huge plus, and I definately appreciate it.

Now, if I can just decide what to buy !
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      08-06-2008, 01:34 PM   #40
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I think I should just have someone local in OC that has knowledge and understanding drive my car and tell me if I have this dreaded greater lag that is induced by 29.2/MSD81.
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      08-06-2008, 01:43 PM   #41
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Quote:
Originally Posted by AWD Addict View Post
Personally, I think it's funny when people talk about turbo lag on this car.
oh, as long as we're trolling, I thought I'd just throw this 5 minutes of fine youtube viewing out there.


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      08-06-2008, 01:46 PM   #42
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Quote:
Originally Posted by dmboone25 View Post
Seriously--they have been. I have never tried to tune any car I have ever owned, and it makes me a little nervous. Getting answers from people who have more experience is a huge plus, and I definately appreciate it.

Now, if I can just decide what to buy !
I think you know which one to buy....

Feel free to PM me if you have other questions that you need answers to.
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      08-06-2008, 01:48 PM   #43
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Quote:
Originally Posted by Active Autowerke II View Post
Lag = over rated.
It's not over rated when you go from 6 individual throttle boddies to one and 2 turbos.
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      08-06-2008, 01:59 PM   #44
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Quote:
Originally Posted by e90AW335i View Post
I think you know which one to buy....

Feel free to PM me if you have other questions that you need answers to.
I meant which boost guage to buy.

Is it "mid to late" August yet?
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