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2Addicts | BMW 2-Series forum Technical Topics N55 (M235i) Engine, Transmission, Exhaust, Tuning BMW M2 Anti-Lag braaap sound after lifting the throttle

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      03-05-2020, 01:41 PM   #67
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Quote:
Originally Posted by f20two View Post
Any update?
No idea, I'm linking some content where a guy did the mod:

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      03-21-2020, 05:35 AM   #68
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If this is solved I'll buy a damn M240i or M235i

Time to move on from my M3, don't like the M4 enough to buy and a nice M235i I can get for 30k AUD where as the cheapest M2 ATM is around 60k mobdrolucky patcherkodi...

That's a lot of track mod money.

Last edited by Gaumund; 03-24-2020 at 01:28 AM..
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      04-26-2020, 08:29 PM   #69
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Bump!

Was this ever figured out?
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      01-20-2021, 03:28 PM   #70
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Quote:
Originally Posted by charern View Post
Bump!

Was this ever figured out?
Quote:
Originally Posted by thejeremyman9 View Post
I would like to hear why you think this is going to add lifespan to your turbo.
I think it's related to this:

Quote:
Originally Posted by Boss330 View Post
With valvetronic, you can have better control of valves (I guess?). For instance creating a "blow through" situation where the injected fuel is ignited but the combustion pressure isn't trapped inside the combustion chamber but released through the exhaust valves (intake valves must be closed during this stage to avoid the pressure escaping to the intake manifold) and thereby spinning the turbos. Sort of like igniting fuel in a container with a small opening, creating a "jet stream" of hot air (exhaust). That "jet stream" will keep the turbos spinning at a high rpm (stated to be around 100.000rpm!!!). Since the combustion pressure is bled out through the exhaust valves, engine braking shouldn't be adversely affected perhaps?

And I also believe that this "jet stream" will be able to sustain a certain boost pressure even under deceleration. At least that would be beneficial in reducing lag, as otherwise the turbos will need time to raise pressure. With a "anti lag base pressure" of say 0.5bar, the engine would feel much more responsive and lag will be virtually non-existent.

For the cylinders that "participate" in the anti lag function this is how I imagine the system works:

Stage 1: Air enters combustion chamber (intake valves open, exhaust valves closed - intake stroke)
Stage 2: Air is compressed (intake and exhaust valves closed, creating engine braking - compression stroke)
Stage 3: Fuel is injected and spark is introduced (both intake and exhaust valves closed, or possibly starting to open exhaust valves here - combustion stroke)
Stage 4: Combustion starts and exhaust valves are opened to vent exhaust (intake valves closed, exhaust valves open - "exhaust stroke")

Stage 1-3 is equal to a normal 4-stroke combustion cycle
Stage 4 is different because the combustion energy isn't used to push down the piston, but to create a "jet stream" of exhaust gases to the turbos and spinning them.

Fuel injected in this "anti-lag" process is measured to create a combustion needed to spin the turbos, not the same amount of fuel needed to push down the piston in a normal 4-stroke cycle.


I'm pretty sure that emission and mileage data is at the normal settings for all cars on sale today.

Quote:
Originally Posted by CanAutM3 View Post
Good analysis .

I agree that, with this feature, it is possible to keep the car "on boost" with "closed throttles". To achieve this, the intake valves would need to open as little as possible on a few cylinders (while remaining closed on others) to just sustain the exhaust "jet stream" you mention. With the intake valves mostly closed there is very little air flow into the engine and the turbos do not need to produce much work to maintain boost. By precisely adjusting the bleed off valve and Valvtronic, the turbo speed and boost pressure can be maintained.

It is very similar to an old driving technique I learned in rally school. Left foot brake to slow the car down but keep the right foot on the throttle to keep the turbo spinning and on boost (I know, there are other reasons to left foot brake but this is also one of them )

Quote:
Originally Posted by CanAutM3 View Post
When abruptly lifting the throttle on the S55, "farting" noises can be heard. There is some wizardry happening in the engine system to keep the turbos spooled. It is most probably a combination of the waste-gates, Vanos and fuel injection that come into play to maintain high energy gases in the exhaust.

Quote:
Originally Posted by Boss330 View Post
As far as I know, very few production turbo engines employ anti lag by using an open throttle and injecting fuel. The S55 and Porsche 991 Turbo S has at least "cold blowing". That is, keeping the throttle/valvetronic open on the overrun so that the engine continues to pump air and spool the turbo. The 991 Turbo S only introduced this technology on the facelifted version going on the market this year.

Quote:
Originally Posted by julienjj View Post
The shift ''farts'' are caused by the torque reduction during shift. Give the transmission a break to execute the upshift faster.

The throttle lift-off cylinder blanking last 2 seconds to keep the turbos spooled.

Since I discovered the eeprom is different I'm waiting to find a local M2 to read it from.

What i hope now is that the DSC in a non-M car can "talk" to the M dme program... since the M2 N55 use the same DSC unit as the M3&M4 and not like the M235i

Also that the automatic transmission in my car works the same (almost a given, since BMW tend to design their engine software to match virtually all transmission they make, DCT, 6MT, ZF...) but still a risk
Has anyone figure it out yet? Bob from Stage FP got the beta file if you are interested. You still need MHD to load this.
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      01-20-2021, 11:07 PM   #71
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Any updates? I need to know this! Can this be done on BM3?
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      01-22-2021, 02:19 AM   #72
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Quote:
Originally Posted by meppadua View Post
Any updates? I need to know this! Can this be done on BM3?
More and more people are interested in this. Maybe kilerek and julienjj found something.
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      01-23-2021, 10:20 PM   #73
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Ive read that BM3 is working on the Ant-Lag System, so hopefully within the next few days/months itll be updated to the OTS maps
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      01-24-2021, 11:27 AM   #74
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Quote:
Originally Posted by meppadua View Post
Ive read that BM3 is working on the Ant-Lag System, so hopefully within the next few days/months itll be updated to the OTS maps
Revisiting this thread since I like to peruse platform similarities.

Like in my last post, the "BRAAAP" isn't anti lag. It's simply the result of boost release into the exhaust.


The "anti lag" that BM3 developed and already released at least for M2s is a combat the default tuning that releases boost between shifts rather than hold it in addition to preventing full boost from beginning to build for a short delay.

BM3's fix seems to hold most of the boost and removes that delay when jumping on gas again after gear shift. You can find the discussion about this particular feature on the F87 Bimmerpost forums.

I've been on the new update for several weeks now and it's marked improvement in both easy driving and full throttle in terms of shifting feel and drivability.
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      01-24-2021, 05:54 PM   #75
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Quote:
Originally Posted by nioh_lbbm2 View Post
Quote:
Originally Posted by meppadua View Post
Ive read that BM3 is working on the Ant-Lag System, so hopefully within the next few days/months itll be updated to the OTS maps
Revisiting this thread since I like to peruse platform similarities.

Like in my last post, the "BRAAAP" isn't anti lag. It's simply the result of boost release into the exhaust.


The "anti lag" that BM3 developed and already released at least for M2s is a combat the default tuning that releases boost between shifts rather than hold it in addition to preventing full boost from beginning to build for a short delay.

BM3's fix seems to hold most of the boost and removes that delay when jumping on gas again after gear shift. You can find the discussion about this particular feature on the F87 Bimmerpost forums.

I've been on the new update for several weeks now and it's marked improvement in both easy driving and full throttle in terms of shifting feel and drivability.
So how would an M235 be able to do the boost release into the exhaust?
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      01-24-2021, 09:52 PM   #76
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OP's first YouTube video immediately reminds me of my 240 - when in Sport+ and accelerating slightly hard, upshifts make the same noise. Doesn't do that under light or hard acceleration though.
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      01-26-2021, 03:49 AM   #77
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Quote:
Originally Posted by ZHP to B58 View Post
OP's first YouTube video immediately reminds me of my 240 - when in Sport+ and accelerating slightly hard, upshifts make the same noise. Doesn't do that under light or hard acceleration though.
The noise might be similar but that's not exactly what we are looking for.

Quote:
Originally Posted by meppadua View Post
So how would an M235 be able to do the boost release into the exhaust?
Same, I would like to know how to do that.
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      02-04-2021, 02:45 PM   #78
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I assume this was never figured out but it's defiantly prevalent when he lets off the throttle in this video. I think he is a tuner/tester for wedge performance because he is active on the F22 group on Facebook and keeps us updated on the progress of his car. Doesn't seem like he gives answers as to how he replicated the sound though.

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      02-06-2021, 05:20 PM   #79
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I need BM3 to come out wit this!
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      02-21-2021, 10:39 AM   #80
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Quote:
Originally Posted by 1slow2_ View Post
I assume this was never figured out but it's defiantly prevalent when he lets off the throttle in this video. I think he is a tuner/tester for wedge performance because he is active on the F22 group on Facebook and keeps us updated on the progress of his car. Doesn't seem like he gives answers as to how he replicated the sound though.

Yup, you are right. Once he let off the throttle, you got the exact same sound for which we are looking for.
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      02-21-2021, 01:25 PM   #81
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Quote:
Originally Posted by Thomas590 View Post
Yup, you are right. Once he let off the throttle, you got the exact same sound for which we are looking for.
Yeah definitely. Im not sure 100% but I think he DCT swapped his car. That could possibly be the answer although I am not sure. He is also pushing 724 whp out of his m235i so it makes sense that he would DCT swap his car
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      02-23-2021, 04:33 PM   #82
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Quote:
Originally Posted by 1slow2_ View Post
Yeah definitely. Im not sure 100% but I think he DCT swapped his car. That could possibly be the answer although I am not sure. He is also pushing 724 whp out of his m235i so it makes sense that he would DCT swap his car
Well, this sound can be also achieved in manual and ZF auto.
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      02-24-2021, 10:17 AM   #83
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Quote:
Originally Posted by Thomas590 View Post
Well, this sound can be also achieved in manual and ZF auto.
You're right. It definitely is in the manual transmission M2s but have not seen this kind of sound in a ZF auto though
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      02-27-2021, 12:55 PM   #84
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Quote:
Originally Posted by 1slow2_ View Post
You're right. It definitely is in the manual transmission M2s but have not seen this kind of sound in a ZF auto though
Here you go:

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      02-28-2021, 07:55 PM   #85
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Quote:
Originally Posted by Thomas590 View Post
Here you go:

Ah, I see thanks. Based on what is being discussed in the 3 series group in the same thread it seems like this is only available through a custom tune
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      03-03-2021, 02:53 PM   #86
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Lightbulb

Quote:
Originally Posted by 1slow2_ View Post
Ah, I see thanks. Based on what is being discussed in the 3 series group in the same thread it seems like this is only available through a custom tune
Quick update



Quote:
Originally Posted by Dazz4C View Post
As I understand it there are tuners who already know how to and can implement it in their custom tunes.

Not available in any OTS tunes (BM3, MHD, etc.) what from what I can see.
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      03-03-2021, 06:35 PM   #87
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Quote:
Originally Posted by Thomas590 View Post
Quick update

Yeah, it looks like he made it work through his custom tune. His car is the only car I have seen with this sound though. But now we know its definitely doable
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      03-10-2021, 03:19 AM   #88
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If somebody wants to get it done:

Quote:
Originally Posted by Dazz4C View Post
Steven Brachulis @ Wedge Performance or David Shoup @ David Shoup Tuning. Not spoken to them, but they're the two discussing in the above thread.


Quote:
Originally Posted by LA1Z24 View Post
I just got an email back from Shoup. He said this noise is only available on M car DME's

"the m2 stle burb is a logic sub routine only found on M cars sadly. It would take custom logic added to the DME code to make this work. Ive spoken with MHD about it several times and they should be adding it eventually."
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