Anybody understand the F80 M3 / F82 M4 turbocharger technology?

[pbar]

So far I haven't seen much technical discussion of the turbocharger details from the BMW tech presentation...

The Turbocharger slide mentions 'impulse charging' as a technology to reduce lag. Is this standard tech, or something new? Google doesn't seem to know much about it ;-)

Also, there appear to be two mono-scroll turbos - each plumbed to just 3 cylinders. Is this unusual? (I'd always thought that a 'twin-turbo' setup was typically a low-pressure and high-pressure turbo in series, but feeding all of the cylinders?)

We seem to have a lot of tech folks on these forums - does anybody know whether this setup is likely to be a good one?

[Robin_NL]

Originally Posted by pbar

So far I haven't seen much technical discussion of the turbocharger details from the BMW tech presentation...

The Turbocharger slide mentions 'impulse charging' as a technology to reduce lag. Is this standard tech, or something new? Google doesn't seem to know much about it ;-)

Also, there appear to be two mono-scroll turbos - each plumbed to just 3 cylinders. Is this unusual? (I'd always thought that a 'twin-turbo' setup was typically a low-pressure and high-pressure turbo in series, but feeding all of the cylinders?)

We seem to have a lot of tech folks on these forums - does anybody know whether this setup is likely to be a good one?

The N54 .35i/ 1M turbo (each 3 cylinders 1 turbo) setup is the same.


The second bold about the 2 turbos in series: AFAIK That's the way a .35Diesel engine has its turbos positioned...




Cheers
Robin

[dhoggm3]

I'm curious as well - how do they keep those fans spooled up off-throttle? That was the single biggest fault with my 335i. Lift for a moment and you lose all your boost. I learned to deal with it by keeping on a little throttle while shifting, but going back and forth between NA and FI cars it surely would be nice not to have to think that much.

[NISFAN]

From the sketchy information we have, I suspect BMW are using old skool 'anti-lag' to maintain turbo speed. They mention it only being used in the Sport modes, and only occasionally. This is because anti lag is not good for turbo life longevity.

The layout itself, suggests two very old skool single scroll turbo chargers......NO VNT.....NO ELECTRIC ASSIST.......NO COMPOUND CHARGING.......NO SEQUENTIAL TURBO.

Note: Twin scroll would have no benefit on a 3 cylinder feed.

[NISFAN]

Originally Posted by dhoggm3

I'm curious as well - how do they keep those fans spooled up off-throttle? That was the single biggest fault with my 335i. Lift for a moment and you lose all your boost. I learned to deal with it by keeping on a little throttle while shifting, but going back and forth between NA and FI cars it surely would be nice not to have to think that much.

There is a solution.....DCT

[Needsdecaf]

Impluse charging, I believe, refers to the sequencing of the exhaust impulses to keep the turbos spinning at maximum potential.

Not sure what the anti-lag is. If it's old school dump raw fuel, then no wonder it only runs part of the time as that would be horrible for consumption and emissions.

The electronic wastegates must play some role. I'm sure instead of snapping open when boost spikes, they modulate it a bit to prevent overpressure but to keep the turbos spinning. It should be interesting to see when more details present themselves.

[mkoesel]

Wow, I had never heard of this ant-lag technique until I read this thread so thanks for the lesson NISFAN. This description sure makes it sound harsh though:

http://www.autos.com/aftermarket-par...ns-of-anti-lag

If BMW is doing anything like this, they would have to have put a lot of innovation into overcoming those drawbacks.

[A418t81]

Originally Posted by mkoesel

Wow, I had never heard of this ant-lag technique until I read this thread so thanks for the lesson NISFAN. This description sure makes it sound harsh though:

http://www.autos.com/aftermarket-par...ns-of-anti-lag

If BMW is doing anything like this, they would have to have put a lot of innovation into overcoming those drawbacks.

I can assure you that BMW is doing no such thing. It almost certainly is related to the electronic wastegate actuators which can keep the wastegates closed during shifts and the shaft speeds up. "Anti-lag" utilizing massive timing retard and "on-shift" rich conditions destroy the turbo and even more importantly would destroy any downstream catalytic convertors on the first shift.

[NISFAN]

Originally Posted by mkoesel

Wow, I had never heard of this ant-lag technique until I read this thread so thanks for the lesson NISFAN. This description sure makes it sound harsh though:

http://www.autos.com/aftermarket-par...ns-of-anti-lag

If BMW is doing anything like this, they would have to have put a lot of innovation into overcoming those drawbacks.

The interesting thing is that the VANOS system could be 'tuned' on the exhaust cam to increase exhaust manifold pressure by opening really early before the end of the power stroke. This coupled with retarded ignition could offer a 'softer' anti lag. This 'real early' has to be within the scope of the cam's natural range, but could be adjusted to provide this type of effect.

[NISFAN]

Originally Posted by A418t81

I can assure you that BMW is doing no such thing. It almost certainly is related to the electronic wastegate actuators which can keep the wastegates closed during shifts and the shaft speeds up. "Anti-lag" utilizing massive timing retard and "on-shift" rich conditions destroy the turbo and even more importantly would destroy any downstream catalytic convertors on the first shift.

Don't forget, in a Rally car, the anti lag is harsh enough to produce 'full boost' even when off throttle. No road car is going to adopt that strategy ( I doubt Mitsubishi, the Turbo supplier would support full anti lag), but the 'pre-tensioning' description, implies, to me at least, that they will use a softer version that reduces 'decay' times.

I don't see how a wastegate can act in any kind of anti lag way, sure you aren't confusing them with Blow off valves?

A wastegate has one purpose, to control Turbine speed (in a limiting way), which it does by leaking the exhaust gasses past the turbine. When off throttle there is nothing a WG can do to improve anything, it will be fully shut.

Regarding gear changing.....boost pressure decay can be slowed by using 'flatshift'. Flatshift is keeping the throttle butterflies fully open, but cutting ignition to interrupt engine torque (required during the change). I have no doubt BMW are using this technique on DSG equipped cars (can be heard in the sound on the Nurburgring video's).

We can add to that by combining 'flatshift' and retarded ignition 'anti lag', this will give more pops on gear change, but will maintain turbine speed if done correctly.

[A418t81]

Originally Posted by NISFAN

Don't forget, in a Rally car, the anti lag is harsh enough to produce 'full boost' even when off throttle. No road car is going to adopt that strategy ( I doubt Mitsubishi, the Turbo supplier would support full anti lag), but the 'pre-tensioning' description, implies, to me at least, that they will use a softer version that reduces 'decay' times.

I don't see how a wastegate can act in any kind of anti lag way, sure you aren't confusing them with Blow off valves?

A wastegate has one purpose, to control Turbine speed (in a limiting way), which it does by leaking the exhaust gasses past the turbine. When off throttle there is nothing a WG can do to improve anything, it will be fully shut.

Regarding gear changing.....boost pressure decay can be slowed by using 'flatshift'. Flatshift is keeping the throttle butterflies fully open, but cutting ignition to interrupt engine torque (required during the change). I have no doubt BMW are using this technique on DSG equipped cars (can be heard in the sound on the Nurburgring video's).

We can add to that by combining 'flatshift' and retarded ignition 'anti lag', this will give more pops on gear change, but will maintain turbine speed if done correctly.

I understand perfectly how turbochargers and engines work. I've built both myself and I have tuned lots of cars in my free time.

The wastegates on the N54, N55, and S55 are different than conventional ones. They default wide open and require vacuum to close them (S55 is electromechanical and does not require vacuum, the actuator itself does it), rather than defaulting closed and requiring boost pressure to open them. BMW chose to do it this way because it gives me ultimate control over exactly how much boost the car runs down to a single pound, and also BMW found that with small turbos there was excessive charge compression even while cruising which hurt fuel economy.

With this in mind, the wastegates on the BMW turbo motors assume a "default" wastegate position during cruise that results in some turbine wheel rpm but not enough to excessively spin the compressor that it results in extra fuel usegage. This is a fine line between keeping the turbo speed up so that transient response is prompt, but keeping it low enough to not affect fuel economy or result in "jumpiness."

The JB4 directly controls the wastegates and you can change the default WG on the fly. It is very easy to see how both throttle response and fuel economy are affected by messing with this setting and then driving around.

Anyway, the whole point of this is that the electronic WG is employed here because it does the same thing. Gives BMW ultimate control on EXACTLY how much boost the engine runs, or even if it runs any at all. They have gone to an electronic system because the mechanical/vacuum assisted system resulted in constant movement of the wastegates during any vehicle operation and lead to wearing of the WG pivots and the dreaded rattle. This gives BMW the same control, but the WG moves exactly to the position needed without "PWM" fluttering that occurs with a mechanical system.

So my point is that BMWs wastegates are NOT shut during cruise or during shifts by any means.

Also, I as I said above I can almost guarantee you that there is no timing retard on the shift that is substantial enough to keep the turbo speed up, or even accelerate it for that matter. They almost certainly just use a much more aggressive default wastegate position.

[NISFAN]

Originally Posted by A418t81

I understand perfectly how turbochargers and engines work. I've built both myself and I have tuned lots of cars in my free time.

The wastegates on the N54, N55, and S55 are different than conventional ones. They default wide open and require vacuum to close them (S55 is electromechanical and does not require vacuum, the actuator itself does it), rather than defaulting closed and requiring boost pressure to open them. BMW chose to do it this way because it gives me ultimate control over exactly how much boost the car runs down to a single pound, and also BMW found that with small turbos there was excessive charge compression even while cruising which hurt fuel economy.

With this in mind, the wastegates on the BMW turbo motors assume a "default" wastegate position during cruise that results in some turbine wheel rpm but not enough to excessively spin the compressor that it results in extra fuel usegage. This is a fine line between keeping the turbo speed up so that transient response is prompt, but keeping it low enough to not effect fuel economy or result in "jumpiness."

The JB4 directly controls the wastegates and you can change the default WG on the fly. It is very easy to see how both throttle response and fuel economy are effected by messing with this setting and then driving around.

Anyway, the whole point of this is that the electronic WG is employed here because it does the same thing. Gives BMW ultimate control on EXACTLY how much boost the engine runs, or even if it runs any at all. They have gone to an electronic system because the mechanical/vacuum assisted system resulted in constant movement of the wastegates during any vehicle operation and lead to wearing of the WG pivots and the dreaded rattle. This gives BMW the same control, but the WG moves exactly to the position needed without "PWM" fluttering that occurs with a mechanical system.

So my point is that BMWs wastegates are NOT shut during cruise or during shifts by any means.

Also, I as I said above I can almost guarantee you that there is no timing retard on the shift that is substantial enough to keep the turbo speed up, or even accelerate it for that matter. They almost certainly just use a much more aggressive default wastegate position.

Well if that truely is the case for BMW, that is a galactic-ally stupid use of a waste gate.

On almost all turbo systems the wastegate is by default closed, held closed by a spring, and this spring pressure is assisted by air. A PWM solenoid is then employed to control the air supply to adjust the WG position.

On cruise, the engine 'energy' is too low to produce much if any boost, so not much is gained by keeping the WG open. Also leaving the WG open is likely to coke up seal surface, causing a leak when it is required to be closed. Just doesn't make any sense to employ a 'PRO LAG' WG 'open by default' strategy.

[A418t81]

Originally Posted by NISFAN

Well if that truely is the case for BMW, that is a galactic-ally stupid use of a waste gate.

On almost all turbo systems the wastegate is by default closed, held closed by a spring, and this spring pressure is assisted by air. A PWM solenoid is then employed to control the air supply to adjust the WG position.

On cruise, the engine 'energy' is too low to produce much if any boost, so not much is gained by keeping the WG open. Also leaving the WG open is likely to coke up seal surface, causing a leak when it is required to be closed. Just doesn't make any sense to employ a 'PRO LAG' WG 'open by default' strategy.

That's how it works, feel free to do all the research you like. It isn't a stupid idea at all and the only time the WGs are fully open is when the car is turned off. Like I was saying, they are held at a "default" position when the car is just cruising at low load that results in just enough shaft rpm to keep transient response sharp while keeping fuel consumption from excessive charge compression to a minimum.

When you are dealing with turbos as small as the N54s where the turbine nozzle is the diameter of a pencil eraser and the turbine wheel not much bigger than a quarter, it doesn't take a lot of energy to result in excessive compressor rpm and "boost" that is just recirculated by the diverter valves.

[NISFAN]

Originally Posted by A418t81

That's how it works, feel free to do all the research you like. It isn't a stupid idea at all and the only time the WGs are fully open is when the car is turned off. Like I was saying, they are held at a "default" position when the car is just cruising at low load that results in just enough shaft rpm to keep transient response sharp while keeping fuel consumption from excessive charge compression to a minimum.

When you are dealing with turbos as small as the N54s where the turbine nozzle is the diameter of a pencil eraser and the turbine wheel not much bigger than a quarter, it doesn't take a lot of energy to result in excessive compressor rpm and "boost" that is just recirculated by the diverter valves.

No, sounds like you have this covered on N54. No wonder turbo BMW owners are nervous about lag, with BMW using this open-wastegate-strategy-because-we-put-a-too-small-turbo-on-the-engine-to-appease-the-very-people-who-don't-accept-lag. How daft?

This shouldn't be the case for S55, the torque graph shows a boost threshold above idle. So should be capable of being on cruise with WG fully shut.....as they should be.

[DKX4///M]

I see a lot of comments coming from users that seem to be well read, educated and maybe even experienced in installing turbos or building non-streetable BIG boost, engines....

Owning an e92 M3 I havent researched the turbo technology on the F series...

That being said, having a degree (and great interest) in physics, minor in engineering and over 10 years experience professionally building some serious rides....Also owned ONLY ONE turbo car years ago...But I read some scientifically inaccurate statements and without singling ppl out, who again, seem well read and knowledgeable ill add some perspective and share a few very simple and common sense ways to reduce lag....

1. smaller in diameter, shorter, and less/smoother bends with the i/c piping (and obviously an appropriately size (and type) of I/C...( I SEE TINY TURBOS W HUGE I/C'S maybe for athestics and i laugh)

2. recirculating BOV's (On cars with MAP sensors only) and setting the BOV to NOT release all the built up pressure between shifts...In an effort to get that sweet BOV "swoosh" we loosen our valves too much and lose almost all of our boost. Even I was guilty of this...

***3. I could share a few more tips, and from the comments im reading id assume many of you already know...But Im tired so 1 more "trick to ELIMINATE lag for me"

I was already running a smal but VERY efficient Twin Scroll "Big" 16G. With Hard Piping, a higher flowrate (Than OEM) INJEN I/C. 272/268 HKS Cams, HKS Downpipe into a 3" testpipe welded and combined with this badboy....

Quicktime Performance Exhaust Valve

I found that site browsing the web over 12 years ago and I can truly say I was the first to have one of those on my Evo i my area...While they never got popular, in 12 years ive seen 3-4 cars with them at the track.

The skinny hard piping , high flow i/c, small but efficient turbo, 3' dowpipe and then NO exhaust restriction allowed the gauge to go from -5psi to 30psi literally instantly with the valve open (and methanol on, to cool EGT, raise octane, etc) also had an ECU tuned for meth and high boost. retarded ignition timing, aftermarket ignition system (extremely powerful) for full burn...

Best part was, NO MORE EXHAUST TICKETS AFTER INSTALLING THIS...FIRST MOD when i S/C my 2011 M3 is the valve. While it wont ad the power like on turbo...More air in--->More out...Simple physics lol...

Hope this long post helped someone.

[F85FTW]

Originally Posted by pbar

So far I haven't seen much technical discussion of the turbocharger details from the BMW tech presentation...

The Turbocharger slide mentions 'impulse charging' as a technology to reduce lag. Is this standard tech, or something new? Google doesn't seem to know much about it ;-)

Also, there appear to be two mono-scroll turbos - each plumbed to just 3 cylinders. Is this unusual? (I'd always thought that a 'twin-turbo' setup was typically a low-pressure and high-pressure turbo in series, but feeding all of the cylinders?)

We seem to have a lot of tech folks on these forums - does anybody know whether this setup is likely to be a good one?

I assume the "impulse charging" has to do with the way the manifold routes exhaust gases to the turbo they do this in a much more complicated way on the s63tu with the cross bank manifold and twin scroll turbos. On the s55 with mono scroll turbos and 3 cylinders feeding a single turbo I assume each tube/primary are different lengths so the exhaust from each does not collide with the exhaust from the other and causes turbulence/back flow. This would give a cleaner flow to the turbo with more concentrated velocity to spin the turbocharger consistently. Just a guess as I haven't seen any explanation of it

[Boss330]

Originally Posted by DKM3Power

I see a lot of comments coming from users that seem to be well read, educated and maybe even experienced in installing turbos or building non-streetable BIG boost, engines....

Owning an e92 M3 I havent researched the turbo technology on the F series...

That being said, having a degree (and great interest) in physics, minor in engineering and over 10 years experience professionally building some serious rides....Also owned ONLY ONE turbo car years ago...But I read some scientifically inaccurate statements and without singling ppl out, who again, seem well read and knowledgeable ill add some perspective and share a few very simple and common sense ways to reduce lag....

1. smaller in diameter, shorter, and less/smoother bends with the i/c piping (and obviously an appropriately size (and type) of I/C...( I SEE TINY TURBOS W HUGE I/C'S maybe for athestics and i laugh)

2. recirculating BOV's (On cars with MAP sensors only) and setting the BOV to NOT release all the built up pressure between shifts...In an effort to get that sweet BOV "swoosh" we loosen our valves too much and lose almost all of our boost. Even I was guilty of this...

***3. I could share a few more tips, and from the comments im reading id assume many of you already know...But Im tired so 1 more "trick to ELIMINATE lag for me"

I was already running a smal but VERY efficient Twin Scroll "Big" 16G. With Hard Piping, a higher flowrate (Than OEM) INJEN I/C. 272/268 HKS Cams, HKS Downpipe into a 3" testpipe welded and combined with this badboy....

Quicktime Performance Exhaust Valve

I found that site browsing the web over 12 years ago and I can truly say I was the first to have one of those on my Evo i my area...While they never got popular, in 12 years ive seen 3-4 cars with them at the track.

The skinny hard piping , high flow i/c, small but efficient turbo, 3' dowpipe and then NO exhaust restriction allowed the gauge to go from -5psi to 30psi literally instantly with the valve open (and methanol on, to cool EGT, raise octane, etc) also had an ECU tuned for meth and high boost. retarded ignition timing, aftermarket ignition system (extremely powerful) for full burn...

Best part was, NO MORE EXHAUST TICKETS AFTER INSTALLING THIS...FIRST MOD when i S/C my 2011 M3 is the valve. While it wont ad the power like on turbo...More air in--->More out...Simple physics lol...

Hope this long post helped someone.

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

[KinoBoom]

"The M4's high-pressure, quick-response turbocharging system utilizes two TwinPower turbos to provide a broad plateu, while BMW's double-VANOS technology varies camshaft timing, allowing higher pressure to build inside the cylinder for optimal power output throughout the rev range."

I think it is pretty simple the way it was put.

[Boss330]

Originally Posted by KinoBoom

"The M4's high-pressure, quick-response turbocharging system utilizes two TwinPower turbos to provide a broad plateu, while BMW's double-VANOS technology varies camshaft timing, allowing higher pressure to build inside the cylinder for optimal power output throughout the rev range."

I think it is pretty simple the way it was put.

That is just PR speak

It doesn't really explain the concept of single scroll turbos fed by three cylinders each and the "de-throttling" that BMW M mentioned in the launch litterature. Neither does it explain what BMW means by "pre tensioned" turbos

That the engine has two turbochargers and high cylinder pressure doesn't really explain a lot...

[8600RPM]

Ya despite them kept using dethrottling, I'm not entirely sure what that is. I surmise they mean creating a shorter pathway from the intake to turbo and thus a more direct response since less volume of air has to fill the pathway. But not entirely sure

[Boss330]

Originally Posted by 8600RPM

Ya despite them kept using dethrottling, I'm not entirely sure what that is. I surmise they mean creating a shorter pathway from the intake to turbo and thus a more direct response since less volume of air has to fill the pathway. But not entirely sure

De-throttling is getting rid of obstacles in the airflow, like the throttle body (which is always wide open on a VALVETRONIC engine, since it's the valve lift that acts as the "throttle").

I also suspect it means using high valve lift on the intake valves during some off throttle situations to keep the air flowing through the engine and feeding the turbos.

Like the F1 tech explained here:

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

[F85FTW]

Originally Posted by Boss330

De-throttling is getting rid of obstacles in the airflow, like the throttle body (which is always wide open on a VALVETRONIC engine, since it's the valve lift that acts as the "throttle").

I also suspect it means using high valve lift on the intake valves during some off throttle situations to keep the air flowing through the engine and feeding the turbos.

Like the F1 tech explained here:

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

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