Anybody understand the F80 M3 / F82 M4 turbocharger technology?

[Boss330]

Originally Posted by F85FTW

What's your take on the "impulse charging" ?

My understanding is that this simply means that they route the exhaust from three cylinders to one turbo, as seen in this illustration:

[CanAutM3]

Originally Posted by F85FTW

What's your take on the "impulse charging" ?

It means that the exhaust routing is made to ensure each individual turbo gets equally spaced exhaust pulses coming from the cylinders.

It was more of a feat to achieve on the S63 since, on a cross plane V8, the firing order on each bank of the V is not even. So having one turbo fed off each bank would not be optimal. BMW came up with the clever solution of putting the turbos inside the V with the exhaust manifolds crossing between banks to get that optimal "impulse charging". It is also more difficult to achieve on single turbo I-6 due to the unequal length of the manifold needed to keep the turbo close to the engine and that is where twin scroll technology comes in.

I am not sure why they brag about it on the S55, as is it a pretty straight forward design (cylinders 1,2 and 3 on one turbo and 4,5 and 6 on the other) .

[A418t81]

As I stated a couple years ago, pre-tensioning means they just put the wastegates into a tighter default position. This increases shaft rpm during cruise resulting in faster transient response with the downside being a small hit to fuel economy due to excessive charge compression. That's why this function is not present in the standard start up mode.

[Boss330]

Originally Posted by A418t81

As I stated a couple years ago, pre-tensioning means they just put the wastegates into a tighter default position. This increases shaft rpm during cruise resulting in faster transient response with the downside being a small hit to fuel economy due to excessive charge compression. That's why this function is not present in the standard start up mode.

I believe it's a bit more than just the closed wastegates. BMW also mentioned software and cams as part of the pre tensioning strategy.

As we have discussed in a different thread (linked to that in one of my previous posts here), they could very well use valvetronic to keep a higher intake valve lift also during off throttle situations to keep more air flowing through the engine (feeding the turbos). In addition to perhaps retarding timing and using tiny amounts of fuel as an anti lag function. I personally doubt they use fuel for anti lag on the overrun, as that is notoriously hard on the turbos, but who knows. My suspicion is that they might employ a mild form of "cold blowing" to feed (pre tension) the turbos on the overrun.

[CanAutM3]

Originally Posted by Boss330

I believe it's a bit more than just the closed wastegates. BMW also mentioned software and cams as part of the pre tensioning strategy.

As we have discussed in a different thread (linked to that in one of my previous posts here), they could very well use valvetronic to keep a higher intake valve lift also during off throttle situations to keep more air flowing through the engine (feeding the turbos). In addition to perhaps retarding timing and using tiny amounts of fuel as an anti lag function. I personally doubt they use fuel for anti lag on the overrun, as that is notoriously hard on the turbos, but who knows. My suspicion is that they might employ a mild form of "cold blowing" to feed (pre tension) the turbos on the overrun.

Interrestingly, I believe that fuel is indeed injected on the overrun to keep the turbos spooled. I doubt that there is sufficient energy in the intake charge to keep the turbo spooled. With traditional anti lag systems that inject bursts of fuel just upstream of the turbine the resulting "explosions" are indeed quite hard on the turbos. But if fuel is injected in the combustion chambers, it would provide a more even flow of high energy gases to the turbines to keep them spooled.

[Boss330]

Originally Posted by CanAutM3

Interrestingly, I believe that fuel is indeed injected on the overrun to keep the turbos spooled. I doubt that there is sufficient energy in the intake charge to keep the turbo spooled. With traditional anti lag systems that inject bursts of fuel just upstream of the turbine the resulting "explosions" are indeed quite hard on the turbos. But if fuel is injected in the combustion chambers, it would provide a more even flow of high energy gases to the turbines to keep them spooled.

Quite possible, but dont forget that in F1 they used both hot and cold blowing to great effect. The level of downforce created by both methods was pretty similar, so even cold blowing should provide a quite substantial air flow to keep the turbos spooling.

[DKX4///M]

I don't have anything to add, as the only turbo car I had was the first Evo VIII in 2003. Seems turbo tech has come a long way.

How does the F8X measure air intake volume, and density? MAF? MAP? IAT?

Guessing BMW A Techs had to take some continuing education to keep up, diagnose, and repair issues w the newer platform...Anyone?

[CanAutM3]

Originally Posted by DKM3Power

I don't have anything to add, as the only turbo car I had was the first Evo VIII in 2003. Seems turbo tech has come a long way.

How does the F8X measure air intake volume, and density? MAF? MAP? IAT?

Guessing BMW A Techs had to take some continuing education to keep up, diagnose, and repair issues w the newer platform...Anyone?

Hot film air mass meters (items 1 and 13)

The picture comes from the S55 Technical Training document

[CanAutM3]

Originally Posted by Boss330

Quite possible, but dont forget that in F1 they used both hot and cold blowing to great effect. The level of downforce created by both methods was pretty similar, so even cold blowing should provide a quite substantial air flow to keep the turbos spooling.

I see what you are saying. Essentially using the energy of the vehicle forward momentum to drive the engine as an air pump that in turn drives the turbines.

However, the turbines still need to spool the compressors in the process, I wonder if there is sufficient energy to do so without adding fuel. Interesting...

[Boss330]

Originally Posted by CanAutM3

I see what you are saying. Essentially using the energy of the vehicle forward momentum to drive the engine as an air pump that in turn drives the turbines.

However, the turbines still need spool the compressors in the process, I wonder if there is sufficient energy to do so without adding fuel. Interesting...

I agree with you and am also intrigued to find out more about this. My suspicion is along what you mentioned, fuel is probably involved...

[DKX4///M]

Originally Posted by CanAutM3

Hot film air mass meters (items 1 and 13)

The picture comes from the S55 Technical Training document

Thanks bro.

Are you guys sure the "anti-lag" techniques are so complex. I mean they look like relatively small turbos, along with hard, thin intake piping, with smooth bends, small i/c's. And from a physics/ engineering stand point inline 6 vs V-6 has more kinetic energy and thus would drop rpm's slower between shifts or on down throttle.

With todays emissions standards combined with the fact that engineers will usually push an OEM forced induction engine on the richer side to prevent knock and the pollutants that come with it, theoretically they could probably induce a post cylinder combustion with just the hydrocarbons "left over" from the combustion but this system seems like it would already have very minimal lag...So doubtul any addditional fuel would be needed.

PS: From racing my buds 135i w stock turbo, but a high flow dp & exhaust, his car makes power instantly. Even from a roll when I'm right at 5500+RPM's his car still takes a car or two INSTANTLY then just holds the lead until about 120+mph, where my M seems to start catching up.

PLUS, a little "turbo lag" is enjoyable and one of the perks of a turbo engine IMHO.

How much boost do F8X's run stock, and whats the static compression ratio?

[SakhirM4]

Originally Posted by DKM3Power

How much boost do F8X's run stock, and whats the static compression ratio?

Boost is 18.1 psi and compression is 10.2:1

[MFNATIK]

You guys are all wrong! I work for BMW as an engineer and thats not how we implement the anti-lag technology. Its actually a trade secret. However, I've been authorized by Albert Bierman to disclose. BMW sprinkles fairy dust onto the impellers and this creates centrifugal venturical forces that increase boost pressure at the precise moment your foot touches the drive by wire gas pedal.

All I know is whatever they engineered works and I love this car!

[CanAutM3]

Originally Posted by DKM3Power

Thanks bro.

Are you guys sure the "anti-lag" techniques are so complex. I mean they look like relatively small turbos, along with hard, thin intake piping, with smooth bends, small i/c's. And from a physics/ engineering stand point inline 6 vs V-6 has more kinetic energy and thus would drop rpm's slower between shifts or on down throttle.

With todays emissions standards combined with the fact that engineers will usually push an OEM forced induction engine on the richer side to prevent knock and the pollutants that come with it, theoretically they could probably induce a post cylinder combustion with just the hydrocarbons "left over" from the combustion but this system seems like it would already have very minimal lag...So doubtul any addditional fuel would be needed.

PS: From racing my buds 135i w stock turbo, but a high flow dp & exhaust, his car makes power instantly. Even from a roll when I'm right at 5500+RPM's his car still takes a car or two INSTANTLY then just holds the lead until about 120+mph, where my M seems to start catching up.

PLUS, a little "turbo lag" is enjoyable and one of the perks of a turbo engine IMHO.

How much boost do F8X's run stock, and whats the static compression ratio?

Anti-lag is not related to the "RPM drop" of the engine, so the engine inertia is irrelevant. It is about the RPM drop of the turbo. When the throttle is lifted, there are no more exhaust gases to spool the turbine, hence the turbo slows down. 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.

[DKX4///M]

Originally Posted by Boss330

There is no BOV on the S55

Read this thread which in some way tries to explain how the S55 anti lag might work:

http://f80.bimmerpost.com/forums/sho....php?t=1211456

Sorry If you misunderstood but I was commenting on ways I cut down lag on my Evolution. Another member pointed out the lack of a BOV a few days ago

Thank you though