S55 Anti Lag vs F1 "blown diffuser" tech - Possible explanation on S55 ALS?

Boss330 · 03-12-2016, 01:21 AM

Quote:

Originally Posted by RSXDC5

Quote:

Originally Posted by Boss330

There has been some discussion and speculation on how the S55 Anti Lag System (ALS) operates.

I remembered that a few years back Formula 1 had a big debate on the "blown diffuser", where exhaust gases was exiting in the diffuser, thereby creating an added downforce by keeping air flow (or in this case, exhaust flow) through the diffuser. Of course this works great under throttle/acceleration, but on the overrun (engine braking) the exhaust flow disappears as the throttle valves close and no air is pumped through the engine and into the exhaust manifolds.

F1 engineers at used a loophole in the regulations and programmed the fly by wire throttle valves to be kept open also on the overrun (engine braking). This means that there is still airflow through the engine and into the exhaust manifolds. Various degrees of throttle opening was used by the different manufacturers.

The official line why they employed the open throttle on the overrun was to "cool the exhaust valves"...

Some teams/engine manufacturers used only "cold blowing" but others used "hot blowing". The difference between them being that the cold blowing only used the open throttle to allow air to be pumped through the engine, while hot blowing also employed fuel injection on the overrun. The fuel added, combined with retarding the ignition perhaps as much as 45 degrees, ignites in the hot exhaust manifolds and creates a hot exhaust gas going to the diffuser. Hot blowing creates a gas flow on the diffuser that is more similar to the gases under acceleration (hot exhaust gases).

Reading the technical manuals on the S55 I suspect that a similar strategy is used for the anti lag system. The valvetronic, or throttle valve, is kept open on the overrun (and most likely also on the upshifts on the DCT) creating a gas stream in the exhaust manifold also under engine braking. And thereby spooling the turbos/keeping the turbos spooled.

Whether the S55 uses cold blowing or hot blowing I'm not sure of. But BMW has said that fuel consumption increases when ALS is activated, suggesting that some form of hot blowing is taking place.

Listen to the second car in this video (Red Bull) and compare that to the "fart" created by the S55 at "off throttle" situations.

Here are some different blown diffuser sounds:

Here is a quite good article on the blown diffusers and how they achieved this concept:

http://www.formula1-dictionary.net/o...e_overrun.html

An article more about the diffuser concepts, but with a good explanation on hot and cold blowing:

http://www.formula1-dictionary.net/diffuser_blown.html

Cool thought, but in short, the answer is no. That will not work on our cars. They are completely different executions of an antilag concept.

I guess you didn't read that Porsche is doing exactly this on the 911 Turbo S?

And how do you know this isn't done on the S55?

Yes, both cold and hot blowing will work on a turbo engine. Keeping gas flow high also under off throttle situations by not shutting the throttle. Just as Porsche has confirmed they are doing...

Boss330 · 03-12-2016, 01:27 AM

Quote:

Originally Posted by Who's on first

Quote:

Originally Posted by MNoob

18,000 rpm. Crazy.

No .. what's crazy was Ferrari was doing over 20K, before regulations started pulling them back. The true good old days, of our generation .. 03'-04'05' ..now that was a sound you never forget.

They all did 20k back then. Actually it was Cosworth who was the first to run an entire race with a 20k redline.

I've been in this dyno room and seen a prototype of that engine running

RSXDC5 · 03-12-2016, 01:37 PM

Quote:

Originally Posted by Boss330

I guess you didn't read that Porsche is doing exactly this on the 911 Turbo S?

And how do you know this isn't done on the S55?

Yes, both cold and hot blowing will work on a turbo engine. Keeping gas flow high also under off throttle situations by not shutting the throttle. Just as Porsche has confirmed they are doing...

On the F1 cars in the blown diffuser era, the engine control units are set to force excessive amounts of air through the engine on off throttle events, enough to have a tangible effect on a diffuser that needs an extreme amount of air passing over it to create negligible downforce. Our cars do not do this, our "anti-lag" parameters simply keep our turbines rotating at a medium rate of speed between throttle events. The amount of air created during this time is not enough to "blow" a diffuser with enough air to create tangible downforce. Also, we would need a diffuser that is set-up to accept being blown over by exhaust hot exhaust air to actually have a downforce benefit

Boss330 · 03-12-2016, 03:31 PM

Quote:

Originally Posted by RSXDC5

On the F1 cars in the blown diffuser era, the engine control units are set to force excessive amounts of air through the engine on off throttle events, enough to have a tangible effect on a diffuser that needs an extreme amount of air passing over it to create negligible downforce. Our cars do not do this, our "anti-lag" parameters simply keep our turbines rotating at a medium rate of speed between throttle events. The amount of air created during this time is not enough to "blow" a diffuser with enough air to create tangible downforce. Also, we would need a diffuser that is set-up to accept being blown over by exhaust hot exhaust air to actually have a downforce benefit

I think you misunderstand what we are trying to say here. There is NO downforce effect from the exhaust at all in this scenario on the F8x. The exhaust doesn't even enter inside the diffuser as it did on the F1 cars back then... We are ONLY talking about employing the same strategy to keep the turbo spinning.

The ECU can't "force excessive amounts of air through the engine". In fact the only thing the ECU can do is keeping the throttle open and retard ignition timing (and inject fuel if "hot blowing" is employed). A internal combustion engine is basically a air pump. The exhaust flow that created downforce by "cold blowing" is dependant on two parametres: RPM and throttle opening. For "hot blowing" it's three parametres: RPM, throttle opening and fuel injected.

By keeping the throttle open on the overrun, the engine keeps pumping just the same amount of air as it was doing when on throttle. As RPM decreases, so does the volume of air (per minute) the engine pumps out via the exhaust. But if the throttle was closed, it wouldn't pump any air at all... It was this fact that was used in the F1 engines. At any given rpm and any given throttle opening, the engine pumps just the same amount of air regardless of whether the car is accelerating or decelerating. As long as the throttle stays open, the engine just keeps on pumping that air through to the exhaust manifold. Thereby keeping exhaust flow sufficient to either have an effect on the diffuser (F1) or on the turbo (S55 and 911 Turbo S)

Introduce some fuel and the velocity of the air in the exhaust system increases. Thereby increasing the effect of the exhaust (either on the diffuser on the F1 cars, or on the turbo).

The Porsche 911 Turbo S does EXACTLY the same to the exhaust flow to the turbo as what "cold blowing" did to the exhaust flow to the diffuser in F1. It keeps the throttle open so that the engine still continues to pump air and thereby the turbo spooled.

There is no way the ECU can force more air through the engine than it's mecanically capable of though...

RSXDC5 · 03-12-2016, 04:26 PM

Quote:

Originally Posted by Boss330

I think you misunderstand what we are trying to say here. There is NO downforce effect from the exhaust at all in this scenario on the F8x. The exhaust doesn't even enter inside the diffuser as it did on the F1 cars back then... We are ONLY talking about employing the same strategy to keep the turbo spinning.

The ECU can't "force excessive amounts of air through the engine". In fact the only thing the ECU can do is keeping the throttle open and retard ignition timing (and inject fuel if "hot blowing" is employed). A internal combustion engine is basically a air pump. The exhaust flow that created downforce by "cold blowing" is dependant on two parametres: RPM and throttle opening. For "hot blowing" it's three parametres: RPM, throttle opening and fuel injected.

By keeping the throttle open on the overrun, the engine keeps pumping just the same amount of air as it was doing when on throttle. As RPM decreases, so does the volume of air (per minute) the engine pumps out via the exhaust. But if the throttle was closed, it wouldn't pump any air at all... It was this fact that was used in the F1 engines. At any given rpm and any given throttle opening, the engine pumps just the same amount of air regardless of whether the car is accelerating or decelerating. As long as the throttle stays open, the engine just keeps on pumping that air through to the exhaust manifold. Thereby keeping exhaust flow sufficient to either have an effect on the diffuser (F1) or on the turbo (S55 and 911 Turbo S)

Introduce some fuel and the velocity of the air in the exhaust system increases. Thereby increasing the effect of the exhaust (either on the diffuser on the F1 cars, or on the turbo).

The Porsche 911 Turbo S does EXACTLY the same to the exhaust flow to the turbo as what "cold blowing" did to the exhaust flow to the diffuser in F1. It keeps the throttle open so that the engine still continues to pump air and thereby the turbo spooled.

There is no way the ECU can force more air through the engine than it's mecanically capable of though...

First off, I thought you wanted to employ blown diffuser tech via the anti-lag setup on the S55.

That being said, of course the ecu cant force more air through the engine than it's mechanically capable of. What you were incorrectly referring to was when I was mentioned the ecu can go through different protocols to keep blowning air (through the engine/turbo) at an accelerated rate while off throttle...

Now if you mean that we could theoretically modify the S55 anti-lag setup by injecting fuel (as you say the new 911 turbo does), that is potentially possible once the tuning is available to support that. I do question why you would want to do that though, is the S55 anti-lag not sufficient for you?

Boss330 · 03-12-2016, 05:11 PM

Quote:

Originally Posted by RSXDC5

Quote:

Originally Posted by Boss330

I think you misunderstand what we are trying to say here. There is NO downforce effect from the exhaust at all in this scenario on the F8x. The exhaust doesn't even enter inside the diffuser as it did on the F1 cars back then... We are ONLY talking about employing the same strategy to keep the turbo spinning.

The ECU can't "force excessive amounts of air through the engine". In fact the only thing the ECU can do is keeping the throttle open and retard ignition timing (and inject fuel if "hot blowing" is employed). A internal combustion engine is basically a air pump. The exhaust flow that created downforce by "cold blowing" is dependant on two parametres: RPM and throttle opening. For "hot blowing" it's three parametres: RPM, throttle opening and fuel injected.

By keeping the throttle open on the overrun, the engine keeps pumping just the same amount of air as it was doing when on throttle. As RPM decreases, so does the volume of air (per minute) the engine pumps out via the exhaust. But if the throttle was closed, it wouldn't pump any air at all... It was this fact that was used in the F1 engines. At any given rpm and any given throttle opening, the engine pumps just the same amount of air regardless of whether the car is accelerating or decelerating. As long as the throttle stays open, the engine just keeps on pumping that air through to the exhaust manifold. Thereby keeping exhaust flow sufficient to either have an effect on the diffuser (F1) or on the turbo (S55 and 911 Turbo S)

Introduce some fuel and the velocity of the air in the exhaust system increases. Thereby increasing the effect of the exhaust (either on the diffuser on the F1 cars, or on the turbo).

The Porsche 911 Turbo S does EXACTLY the same to the exhaust flow to the turbo as what "cold blowing" did to the exhaust flow to the diffuser in F1. It keeps the throttle open so that the engine still continues to pump air and thereby the turbo spooled.

There is no way the ECU can force more air through the engine than it's mecanically capable of though...

First off, I thought you wanted to employ blown diffuser tech via the anti-lag setup on the S55.

That being said, of course the ecu cant force more air through the engine than it's mechanically capable of. What you were incorrectly referring to was when I was mentioned the ecu can go through different protocols to keep blowning air (through the engine/turbo) at an accelerated rate while off throttle...

Now if you mean that we could theoretically modify the S55 anti-lag setup by injecting fuel (as you say the new 911 turbo does), that is potentially possible once the tuning is available to support that. I do question why you would want to do that though, is the S55 anti-lag not sufficient for you?

You keep missing the point we are making here.

We are speculating if the anti lag on the S55 is similar to the method used in F1 when they had the blown diffusers. Further we are speculating if the S55 uses cold or hot "blowing" to keep the turbo spooled. No modifications. Just trying to understand how the S55 anti lag works. I think this was pretty clear from the OP...

Now we recently got confirmation that the latest 911 Turbo S employs cold blowing (confirming my original theory in the OP about a possible anti lag method).

Exactly what kind of "protocols" can the ECU use to keep up exhaust flow at "an accelerated rate"???? Apart from the ability to control the throttle opening (cold blowing), and injecting fuel while under off throttle scenarios with throttle open (hot blowing). Which is exactly what was explained in the OP...

Remember that the exhaust flow isn't accelerated neither during hot or cold blowing compared to what it is while under throttle... Hot or cold blowing is just a method to maintain a portion of the exhaust flow the engine had under acceleration instead of stopping it as it would with a closed throttle.

RSXDC5 · 03-12-2016, 05:34 PM

Quote:

Originally Posted by Boss330

You keep missing the point we are making here.

We are speculating if the anti lag on the S55 is similar to the method used in F1 when they had the blown diffusers. Further we are speculating if the S55 uses cold or hot "blowing" to keep the turbo spooled. I think this was pretty clear from the OP...

Now we recently got confirmation that the latest 911 Turbo S employs cold blowing (confirming my original theory in the OP about a possible anti lag method).

Exactly what kind of "protocols" can the ECU use to speed up exhaust flow????

Jesus.

Why does it even matter if the S55 anti-lag is similiar to the F1 blowing tech, it's not like we could additionally leverage that knowledge to a potential advantage in our cars.

Again, misinterpreting what I was saying about "ecu protocols". What I said was the the S55 engine computer KEEPS the turbines spinning at a medium/high rate of speed in off throttle events, THAT is the protocol I am referring to (compared to a standard turbo engine, that does not do this)

I do not have specific knowledge to whether hot or cold blowing is employed on the S55, but again, even if it was either hot or cold blowing, so what??

I would assume cold blowing is used as hot blowing creates a ton of heat in the engine and exhaust, something that is not sustainable over time in a production car...probably why porsche adopted cold blowing (as you mentioned)

Boss330 · 03-12-2016, 05:53 PM

Quote:

Originally Posted by RSXDC5

Quote:

Originally Posted by Boss330

You keep missing the point we are making here.

We are speculating if the anti lag on the S55 is similar to the method used in F1 when they had the blown diffusers. Further we are speculating if the S55 uses cold or hot "blowing" to keep the turbo spooled. I think this was pretty clear from the OP...

Now we recently got confirmation that the latest 911 Turbo S employs cold blowing (confirming my original theory in the OP about a possible anti lag method).

Exactly what kind of "protocols" can the ECU use to speed up exhaust flow????

Jesus.

Why does it even matter if the S55 anti-lag is similiar to the F1 blowing tech, it's not like we could additionally leverage that knowledge to a potential advantage in our cars.

Again, misinterpreting what I was saying about "ecu protocols". What I said was the the S55 engine computer KEEPS the turbines spinning at a medium/high rate of speed in off throttle events, THAT is the protocol I am referring to (compared to a standard turbo engine, that does not do this)

I do not have specific knowledge to whether hot or cold blowing is employed on the S55, but again, even if it was either hot or cold blowing, so what??

I would assume cold blowing is used as hot blowing creates a ton of heat in the engine and exhaust, something that is not sustainable over time in a production car...probably why porsche adopted cold blowing (as you mentioned)

If you don't have any interest in finding out how stuff works, then this thread has no value for you...

The whole point was to point out a possible anti lag method. One we later have learned is used by Porsche. There was quite a bit of discussion when the F8x was launched about what was meant by "pre tensioned" turbos. So this thread was an attempt at explaining one possible method that could be used.

It's not about "using it to our advantage" (Even though a tuner could do just that by having a more agressive setup on throttle opening and/or fuel, like the M4 GTS most likely has). It's just a discussion about a possible method for anti lag in the S55. Some people, like me, want to understand how technology works. Others don't. Simple as that.

Some people are happy about not knowing how a DCT transmission works as long as it shifts how it's supposed to. Others also want to find out how the double clutch system works. This thread was for those that wants to know how stuff works...

milk242 · 03-12-2016, 07:23 PM

Wouldn't it be easy to tell which is employed through logging? I don't know about BMW platforms, but when I had an Audi with VagCom, I could log throttle position.

terahertz · 03-12-2016, 08:55 PM

Quote:

Originally Posted by milk242

Wouldn't it be easy to tell which is employed through logging? I don't know about BMW platforms, but when I had an Audi with VagCom, I could log throttle position.

Someone from a similar thread has noted that the throttle plate stays wide open after lifting for a couple seconds. Also, valve timing goes really negative or something like that. So yes, it is pretty much confirmed that they are doing some of this fancy stuff.

From my experience driving the car, I think the car does cold blowing and hot blowing depending on the situation. Sometimes when you lift halfway, you'll get a humming sound, this seems more like cold blowing to me. When you lift abruptly around 3-4k rpm, sometimes you get pops and bangs, that's definitely hot blowing. It feels like every other cylinder is getting fuel when this happens, which was why I was saying how Porsche says they "interrupt fuel injection" could be interpreted as cold blowing or hot blowing 50% cylinders.

I have active sound turned off and valves open, so these things are easier to hear.

It's interesting to compare to F1 because Mercedes hot blows 50% cylinders and Renault cold blows, but they are blowing it for an entirely different reason.

Boss330 · 03-13-2016, 04:05 AM

Quote:

Originally Posted by terahertz

Quote:

Originally Posted by milk242

Wouldn't it be easy to tell which is employed through logging? I don't know about BMW platforms, but when I had an Audi with VagCom, I could log throttle position.

Someone from a similar thread has noted that the throttle plate stays wide open after lifting for a couple seconds. Also, valve timing goes really negative or something like that. So yes, it is pretty much confirmed that they are doing some of this fancy stuff.

From my experience driving the car, I think the car does cold blowing and hot blowing depending on the situation. Sometimes when you lift halfway, you'll get a humming sound, this seems more like cold blowing to me. When you lift abruptly around 3-4k rpm, sometimes you get pops and bangs, that's definitely hot blowing. It feels like every other cylinder is getting fuel when this happens, which was why I was saying how Porsche says they "interrupt fuel injection" could be interpreted as cold blowing or hot blowing 50% cylinders.

I have active sound turned off and valves open, so these things are easier to hear.

It's interesting to compare to F1 because Mercedes hot blows 50% cylinders and Renault cold blows, but they are blowing it for an entirely different reason.

That's correct. However I am still waiting for someone to log MAF... That would tell us how much air is flowing through the engine under these situations.

The throttle valve on a valvetronic engine is just part of the equation... If valvetronic is at minimum lift, then the throttle valve being open doesn't make any difference...

BTW. It was on page 1 of this thread datalogging was brought up. Not on a different thread.

jaybird124 · 06-19-2016, 06:52 PM

Was anyone able to unearth the specifics of the S55 system?

d k · 06-21-2016, 11:46 AM

That McLaren MP4/7A is blowing INTO the diffuser.....

Obviously that design didnt stick around too long

Boss330 · 06-21-2016, 02:55 PM

Quote:

Originally Posted by d k

That McLaren MP7A is blowing INTO the diffuser.....

Obviously that design didnt stick around too long

MP7A?

Do you mean the F1 cars with blown diffusers?

It only disappeared due to being banned in the regulations.

BTW, this thread isn't about the aero advantages (downforce) that the F1 cars gained from the blown diffuser. But how the same engine mapping can be used as anti lag on a turbo engine.

Skid123 · 06-24-2016, 03:11 AM

I think OP's observation is spot on. There might be other ALS tricks, for example another way of hot blowing the turbo:

The guy also talked about ALS through ignition timing, which has been mentioned in the thread.

d k · 06-27-2016, 07:41 PM

Sorry MP4/7A

I was just commenting how the exhaust was blowing under the diffuser, which isn't exactly the best way to create a low pressure area.

Quote:

Originally Posted by Boss330

MP7A?

Do you mean the F1 cars with blown diffusers?

It only disappeared due to being banned in the regulations.

BTW, this thread isn't about the aero advantages (downforce) that the F1 cars gained from the blown diffuser. But how the same engine mapping can be used as anti lag on a turbo engine.

CanAutM3 · 06-27-2016, 08:13 PM

Quote:

Originally Posted by d k

Sorry MP4/7A

I was just commenting how the exhaust was blowing under the diffuser, which isn't exactly the best way to create a low pressure area.

Well actually it is...

The point of the diffuser is not create a low pressure area at the diffuser itself, but rather to leverage the low pressure area behind the car to accelerate the flow under the car. When air flow velocity is increased, pressure is decreased. The low pressure area is upstream of the diffuser. Injecting the exhaust gases serve the same purpose where the exhausts act like a "jet pump" accelerating the air flow under the car.

Intensemojo · 06-27-2016, 08:42 PM

Button's title year

Boss330 · 06-28-2016, 04:38 PM

Quote:

Originally Posted by CanAutM3

Quote:

Originally Posted by d k

Sorry MP4/7A

I was just commenting how the exhaust was blowing under the diffuser, which isn't exactly the best way to create a low pressure area.

Well actually it is...

The point of the diffuser is not create a low pressure area at the diffuser itself, but rather to leverage the low pressure area behind the car to accelerate the flow under the car. When air flow velocity is increased, pressure is decreased. The low pressure area is upstream of the diffuser. Injecting the exhaust gases serve the same purpose where the exhausts act like a "jet pump" accelerating the air flow under the car.

Exactly! And is why F1 teams routed the exhaust flow through the diffuser as long as they where allowed to before the FIA made it illegal.

03-12-2016, 07:23 PM	#31
milk242 Captain 184 Rep 760 Posts Drives: Car Join Date: Apr 2008 Location: Dallas iTrader: (4)	Wouldn't it be easy to tell which is employed through logging? I don't know about BMW platforms, but when I had an Audi with VagCom, I could log throttle position. __________________ 14 Audi S4 (sold) 16 BMW M3 (sold) 16 VW Golf GTI (sold) 20 Tesla Model 3 23 Audi R8 (on order, never came )
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06-19-2016, 06:52 PM	#34
jaybird124 Major 157 Rep 1,046 Posts Drives: 2017 M3 ZCP Join Date: Nov 2005 Location: Florida iTrader: (0)	Was anyone able to unearth the specifics of the S55 system? __________________ '17 M3 Imola Red/Carbonstructure Cloth, Competition, Lighting, 6MT Retired: '93 325i \|'99 Jeep Wrangler Sport \|'06 330i Sport \|'08 335i Sport \|'08 328i Sport \|'09 335d Sport
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06-21-2016, 11:46 AM	#35
d k Second Lieutenant 47 Rep 210 Posts Drives: BMWless for few weeks Join Date: Nov 2011 Location: SoCal iTrader: (0)	That McLaren MP4/7A is blowing INTO the diffuser..... Obviously that design didnt stick around too long Last edited by d k; 06-27-2016 at 07:39 PM..
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06-24-2016, 03:11 AM	#37
Skid123 Private First Class 49 Rep 111 Posts Drives: None Join Date: Apr 2016 Location: None iTrader: (0)	I think OP's observation is spot on. There might be other ALS tricks, for example another way of hot blowing the turbo: The guy also talked about ALS through ignition timing, which has been mentioned in the thread. Last edited by Skid123; 06-24-2016 at 03:29 AM..
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06-27-2016, 08:42 PM	#40
Intensemojo Private First Class 88 Rep 149 Posts Drives: BMW M4 Join Date: Jul 2015 Location: Chicago iTrader: (0)	Button's title year
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