Roundel Magazine Dec 2013 M4 Article

[Sir Loin]

I haven't read it myself, but I don't think there is anything that we don't already know.

[nonagon]

This bit on how turbo lag is eliminated is interesting.

[swamp2]

Nice article.

My main take-aways:

6MT and CSiC brakes required to hit 1500 kg... Exactly as I predicted...

E92 is the steering benchmark (that bar is not set very high)? Sure the E92 has good steering but it has some very odd little foibles as well. The steering was better in the E46 M3. That being said I am not in the least bit worried about the new EPS system.

[Boss330]

Originally Posted by swamp2

Nice article.

My main take-aways:

6MT and CSiC brakes required to hit 1500 kg... Exactly as I predicted...

E92 is the steering benchmark (that bar is not set very high)? Sure the E92 has good steering but it has some very odd little foibles as well. The steering was better in the E46 M3. That being said I am not in the least bit worried about the new EPS system.

My main take-away was the turbo tech and apparent lack of lag! Perhaps it's not only Ferrari that want a virtually lag free engine...

[CanAutM3]

Originally Posted by nonagon

This bit on how turbo lag is eliminated is interesting.

Finally some insight on the tech used to minimize/eliminate turbo lag

[GOLFFRR]

nice, thanks for posting.

excited to see what is revealed on the 12th

[jsublime]

Overall a good piece. Although at one point it seemed like they were trying to say it's a parts bin car - tranny from 1M, diff from m5, etc.

Mentioned tire sizes of 255/35/19 and 275/35 for the rear - 19s are required to clear CCB. So let me get this straight - you have to spend $$$$ to save a few pounds but then you are required to put heavier wheels/tires on? Doesn't that defeat the purpose?

[CanAutM3]

Originally Posted by jsublime

Overall a good piece. Although at one point it seemed like they were trying to say it's a parts bin car - tranny from 1M, diff from m5, etc.

Mentioned tire sizes of 255/35/19 and 275/35 for the rear - 19s are required to clear CCB. So let me get this straight - you have to spend $$$$ to save a few pounds but then you are required to put heavier wheels/tires on? Doesn't that defeat the purpose?

IIRC, the froged 19" 220M on the E9X were lighter than the baseline cast 18" rims. Plus 19" tires are less heavy than 18"...

...will need to do an actual weight comparison of the 18" and 19" on the F8X before we can draw conclusions here.

[RMB]

Very nice article, and as others have said, it has given us more information about the technical aspects of the new M3/M4. Thank you for posting.

[basscadet]

Originally Posted by CanAutM3

Plus 19" tires are less heavy than 18"...

How is that possible?

[tdizzle]

Originally Posted by basscadet

How is that possible?

Less sidewall to fit perhaps? Same size/profile, I'd expect them to be heavier, but perhaps going from 275/40/18 to a 275/30/19 (random example), perhaps the 19 will be lighter.

Time to check the weights on tirerack!

[Suave]

It's a good read to bring those who do not follow forums to get a summary of what FXX brings to the table. Nothing really new even about the Turbos but informative nonetheless.

[mkoesel]

In Sport or Sport Plus modes, when you lift, the computer quits sending fuel pulses to some - but not all - of the cylinders. The remains cylinders continue to keep the turbines spinning...

So it's vaguely like an Antilag system in that it uses fuel, but it is much less harsh since the fuel is igniting in the cylinders as normal. Yes?

http://en.wikipedia.org/wiki/Antilag_system

This begs the question: if such a simple solution is possible, why hasn't it been implemented long ago? We need more details. I am also curious how this effects the feel and behavior of the car when active. I.e. does the car seem to decelerate at a lower rate than you would expect? For that matter, can you feel the system disengage?

Also I notice this is only for the more aggressive modes. I wonder if it will mean that they will state fuel efficiency and emissions numbers without these systems in the mix.

Interesting though.

[JoeFromPA]

Mkoesel,

I do not know the system, but the main goal is to continue venting exhaust gases right? And to do it while decelerating, you need to eliminate or really limit compression while keeping sufficient exhaust volume flowing. My guess is that the valvetronic system is being used to independently

Simultaneously, you need to keep the turbo unloaded so that it keeps spinning but is not loaded down with compressing air.

So my guess is, based upon the descriptions I've seen thus far:

BMW is continuing to inject fuel and air into 3 cylinders during decel, keeping the intake and exhaust valves open to optimize exhaust flow.

My guess is they are then keeping the wastegate open to vent compressed air to enable the turbo to spin at maximum speed.

...

As for why this has never been done before: I think that's like asking why Nissan was one of the first to offer rev-matched downshifts on their manual transmissions in the 370z.

I think it became possible in the last 10 years and no one has incurred the design cost to do it. Because to your point, all the components are there.

However, it may also require unique turbocharger design...and many manufacturers use a nearly pre-existing turbo.

[Boss330]

Originally Posted by mkoesel

So it's vaguely like an Antilag system in that it uses fuel, but it is much less harsh since the fuel is igniting in the cylinders as normal. Yes?

http://en.wikipedia.org/wiki/Antilag_system

This begs the question: if such a simple solution is possible, why hasn't it been implemented long ago? We need more details. I am also curious how this effects the feel and behavior of the car when active. I.e. does the car seem to decelerate at a lower rate than you would expect? For that matter, can you feel the system disengage?

Also I notice this is only for the more aggressive modes. I wonder if it will mean that they will state fuel efficiency and emissions numbers without these systems in the mix.

Interesting though.

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.

[CanAutM3]

Originally Posted by basscadet

How is that possible?

Simple: less sidewall.

Check on the Michelin site and compare 18" and 19" tire weights with similar overall diameter, you'll see.

The PSS 265/35R19 1.1 kg lighter than the 265/40R18...

[CanAutM3]

Originally Posted by mkoesel

So it's vaguely like an Antilag system in that it uses fuel, but it is much less harsh since the fuel is igniting in the cylinders as normal. Yes?

http://en.wikipedia.org/wiki/Antilag_system

This begs the question: if such a simple solution is possible, why hasn't it been implemented long ago? We need more details. I am also curious how this effects the feel and behavior of the car when active. I.e. does the car seem to decelerate at a lower rate than you would expect? For that matter, can you feel the system disengage?

Also I notice this is only for the more aggressive modes. I wonder if it will mean that they will state fuel efficiency and emissions numbers without these systems in the mix.

Interesting though.

As others have stated, IMO, it is the complex interaction between Valvtronic and the electronic wastegates than can make this happen. The basic concept is simple but making it happen is much more complex. We are probably at a point where the technology (speed and precision) of the Valvtronic system and the computing power of the ECU are finaly capable of such a feat.

As you specify, the main drawback is increased fuel consumption and is probably the reason it is not the "standard" drive modes.

[CanAutM3]

Originally Posted by Boss330

With valvetronic, you can have better control of both exhaust and intake 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.

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 )

[Groundpilot]

Originally Posted by CanAutM3

Simple: less sidewall.

Check on the Michelin site and compare 18" and 19" tire weights with similar overall diameter, you'll see.

The PSS 265/35R19 1.1 kg lighter than the 265/40R18...

I bet 265/35 R18 is lighter than 265/35 R19
19 inch tires are significantly more expensive and the selection is limited. I dont even think r-comp.tires are available in 19in.

[CanAutM3]

Originally Posted by Groundpilot

I bet 265/35 R18 is lighter than 265/35 R19

How much do you want to wager, I'm in for easy money

According to the Michelin website, the 19" 265/35 PSS is still lighter than the 18" 265/35 by 0.5 kg; but it is not the same diameter so it is not a fair comparison.

[Boss330]

Originally Posted by Groundpilot

I bet 265/35 R18 is lighter than 265/35 R19
19 inch tires are significantly more expensive and the selection is limited. I dont even think r-comp.tires are available in 19in.

You obviously mean 265/40R18 vs 265/35R19? They can't have the same aspect ratio of 35% in both 18 and 19 because that wouldn't work out with achieving a similar rolling circumference...

But a Michelin Sport Plus as these weights:

265/35R18 - 26,1lbs
265/40R18 - 27,3lbs
265/35R19 - 25lbs

So even a 265/35R18 is heavier than a 265/35R19...

[mkoesel]

Great replies on how the "antilag" system works.

So it's not a matter of keeping the combustion process going in a sort of "skeleton crew" fashion as I had thought. It is about hijacking the subsystems that normally drive said combustion process and using them in an innovative way to instead apply pressurized gasses to the turbines in the turbochargers. Very clever. And yes, I agree that this is probably only recently possible with the latest Valevtronic technology.