# Question About Interview of Ulrich Bruhnke



## Malibubimmer (Sep 28, 2005)

There is an interview of Ulrich Bruhnke as a sidebar to an article in December 2005 Automobile Magazine (page 78) comparing the M6 to the CLS55 AMG.

Bruhnke says the following:



> _*Bruhnke Interview In Automobile Magazine*_
> This business is as pragmatic as it is emotional. For example, we won't do an M7, but *I would never dismiss turbocharging*. After all, BMW once won the Formula 1 world championship with a turbocharged engine. In the end, it's the result that matters, not so much how we generate it. [Grinning broadly he adds] But I can assure you that *a supercharged BMW won't happen.*


Can someone explain to me why the chief of the M Division (and formerly head of AMG) would rule out supercharging a Bimmer, but not turbocharging it -- especially since he says "it's the result that matters, not how we generate it" ?

And why was he observed to be "grinning broadly"?

What am I missing? Is it the German sense of humor? :dunno:


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## Mr Paddle.Shift (Dec 19, 2001)

Two things I think why:

1. Turbocharging has been more of a BMW tradition. Not just the early days of F1. But the 2002 and several Turbo diesel for production cars and touring race cars. 

2. Alpina is already supercharging the B7, B5 and possibly right down to B3.


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## Malibubimmer (Sep 28, 2005)

Mr Paddle.Shift said:


> Two things I think why:
> 
> 1. Turbocharging has been more of a BMW tradition. Not just the early days of F1. But the 2002 and several Turbo diesel for production cars and touring race cars.
> 
> 2. Alpina is already supercharging the B7, B5 and possibly right down to B3.


Thanks for your comments, but I don't think they quite answer my question. Why did Bruhnke say he would rule out supercharging a Bimmer, but not turbocharging it -- especially since he says "it's the result that matters, not so much how we generate it." Don't supercharging and turbo(super)charging do the same thing to the "result" -- add more horsepower?


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## Mr Paddle.Shift (Dec 19, 2001)

I would think he rules out SC because turbo has a better torque level throughout the RPM band. Plus the two reasons I mentioned based on tradition and Alpina's involvement.


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## Malibubimmer (Sep 28, 2005)

Mr Paddle.Shift said:


> I would think he rules out SC because turbo has a better torque level throughout the RPM band. Plus the two reasons I mentioned based on tradition and Alpina's involvement.


Thanks. That helps to answer it for me - except I thought (apparently incorrectly) - that there was more lag with turbocharging than supercharging. I will read here more carefully. Perhaps you can point out the flaws in this on line article:


> Superchargers afford the engine immediate response since the supercharger is always compressing intake air, provided that the engine is rotating. Although this initial boost is very small, it's growth is gradual with increased engine speed, resulting in a smooth increase in power. Turbochargers, on the other hand, suffer from what is refered to as turbo lag. Becuase of the inertia of the turbocharger rotating assembly, the turbo must "spool up" before it is able to compress air, so there is no power increase at low engine speeds, as the turbo impeller starts rotating.


This quote is found at: http://www.turbocalculator.com/turbocharger-supercharger.html


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## Mr Paddle.Shift (Dec 19, 2001)

Well, then it really opens up a discussion on Turbo vs SC. And within the SC family, there are the centrifugal, roots and twinscrew compressors. There are various opposing views on which system is better. Folks who debated have agreed to disagree. I'd like to avoid that discussion here cos it will alwaysend up at the same place. I have a centrifugal SC, I track it and I love it.

That statement does hold some truth. Yes, a centrifugal SC (since i t's belt driven) is more linear in terms of power delivery. But turbo applications these days have come a long way to minimize lag as well. Biturbo application for one. Folks who track their STi and Evos have their ECU tuned such that the section before the boost kicks is linearized.

Btw, that quote from that website makes some sense but there are other things they say which are quite incorrect. So I will take anything on there with a grain of salt. Check out books by Corky Bell instead.


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## BeRzErKaS (Jan 1, 2004)

Mr Paddle.Shift said:


> Two things I think why:
> 
> 1. Turbocharging has been more of a BMW tradition. Not just the early days of F1. But the 2002 and several Turbo diesel for production cars and touring race cars.
> 
> 2. Alpina is already supercharging the B7, B5 and possibly right down to B3.


 I would tend to agree. I think it's much easier for ///M purists to stomach the idea of turbo bmw's seeing as how the turboM20 made such a rich contribution to the ///M pedigree.

But, that said, does anyone else find it ironic that the only aftermarket FI tuner endorsed by BMW (dinan) is now specializing in superchargers? If you look back to the early '90s you'll even find that Dinan's previous specialty was in fact TURBO's. They produced quite a few turbo e30's some of which can be seen on e30 forums still running strong today.

If this is the way BMW truely feels then I bet it ruffled quite a few feathers when Dinan chose to change their focus. I wonder what the reasoning was behind the switch... ??


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## SmoothCruise (Jul 23, 2005)

Malibubimmer said:


> Thanks. That helps to answer it for me - except I thought (apparently incorrectly) - that there was more lag with turbocharging than supercharging. I will read here more carefully. Perhaps you can point out the flaws in this on line article:
> 
> This quote is found at: http://www.turbocalculator.com/turbocharger-supercharger.html


There's also the "twin charger" which VW came out with. It has two blowers, one driven by the belt, another by the exhaust, and an ecu to switch smoothly between the two. The idea has been around for a long time, but the technology hasn't matured enough until now. So you get the immediate results of the SC, and the higher torque of the turbo. Pretty neat.


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## Alex Baumann (Dec 19, 2001)

SmoothCruise said:


> There's also the "twin charger" which VW came out with. It has two blowers, one driven by the belt, another by the exhaust, and an ecu to switch smoothly between the two. The idea has been around for a long time, but the technology hasn't matured enough until now. So you get the immediate results of the SC, and the higher torque of the turbo. Pretty neat.


Yup, very neat indeed.

http://www.bimmerfest.com/forums/showthread.php?t=110345

I'd really like to test drive this car just to see the engine characteristics.


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## Mr Paddle.Shift (Dec 19, 2001)

Actually, Dinan is not endorsed by BMW in any way. I do agree that they are *closer* to BMW in the US than any other tuners. But Dinan is not one of the factors that affect the decisions BMW makes.

The only true recognized tuner/remanufacturer is Alpina.



BeRzErKaS said:


> I would tend to agree. I think it's much easier for ///M purists to stomach the idea of turbo bmw's seeing as how the turboM20 made such a rich contribution to the ///M pedigree.
> 
> But, that said, does anyone else find it ironic that the only aftermarket FI tuner endorsed by BMW (dinan) is now specializing in superchargers? If you look back to the early '90s you'll even find that Dinan's previous specialty was in fact TURBO's. They produced quite a few turbo e30's some of which can be seen on e30 forums still running strong today.
> 
> If this is the way BMW truely feels then I bet it ruffled quite a few feathers when Dinan chose to change their focus. I wonder what the reasoning was behind the switch... ??


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## Mr Paddle.Shift (Dec 19, 2001)

SmoothCruise said:


> There's also the "twin charger" which VW came out with. It has two blowers, one driven by the belt, another by the exhaust, and an ecu to switch smoothly between the two. The idea has been around for a long time, but the technology hasn't matured enough until now. So you get the immediate results of the SC, and the higher torque of the turbo. Pretty neat.


Lancia had a SC/TC combo working together. I need to dig out some old info I posted before. A subsidary company of ZF worked on the system but company shut down. Interestingly enough ASA (supplier of SC for Alpina) is occupying the foundry.


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## SmoothCruise (Jul 23, 2005)

Alex Baumann said:


> Yup, very neat indeed.
> 
> http://www.bimmerfest.com/forums/showthread.php?t=110345
> 
> I'd really like to test drive this car just to see the engine characteristics.


There's also another supercharger that I forgot the name. I'll call it the centripetal supercharger which is basically a centrifugal supercharger but instead of shooting air away from the axis of rotation, the blades are shaped to suck air inwards. Since there is less volume closer to the axis of rotation, the air not only speeds up like the centrifugal blower, it also compresses. The overall net effect is to have a SC with the characteristics of both a centifugal charger and a twin-screw (Lysholm) charger.

Guess who has the patents for it? I'll give you some scroll space so you can guess....

VW.

I don't think they've tried spinning those centripetal blades with exhaust pressure yet? I bet you can get even more boost per given spin rate. Ofcourse, hasn't everyone thought of all these blower ideas out there? I've thought of all these ideas independently while dreaming about ways to speed up automobiles, especially my 6er. But, also at my desk is the fortune cookie tape which states:

"Some people never have anything except ideas. Go do it."


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## bjacques (Feb 18, 2005)

BeRzErKaS said:


> I would tend to agree. I think it's much easier for ///M purists to stomach the idea of turbo bmw's seeing as how the turboM20 made such a rich contribution to the ///M pedigree.
> 
> But, that said, does anyone else find it ironic that the only aftermarket FI tuner endorsed by BMW (dinan) is now specializing in superchargers? If you look back to the early '90s you'll even find that Dinan's previous specialty was in fact TURBO's. They produced quite a few turbo e30's some of which can be seen on e30 forums still running strong today.
> 
> If this is the way BMW truely feels then I bet it ruffled quite a few feathers when Dinan chose to change their focus. I wonder what the reasoning was behind the switch... ??


There's an easy answer to why any tuner chooses a centrifugal supercharger... It's really easy. A centrifugal blower has the space envelope of a turbo (small), with a supercharger's simplicity. You don't have to redesign the exhaust manifold or run pipes all over the engine bay. Often, the lubrication is much simpler. Boost control is dead simple... The pulleys dictate how much boost you'll produce. You never have to worry about getting the wastegate aerodynamics wrong and ending up with huge spikes or nasty creep, or god forbid a hose blowing off and dangerously overboosting. With the supercharger, all you need is two pulleys, a belt, bracket and some air tubes.

Also, take into account the manufacturing difficulties. A turbo exhaust manifold is a relatively complex casting. Ancillary exhaust and air piping is also expensive to duplicate en masse. A turbo will tend to have a longer run of air piping. The supercharger's bracket, however, is simple to duplicate. It can be cnc machined out of flat sheet, water jet cut, laser cut, EDM'd, stamped, or very easily cast. The supercharger can usually be placed very close to the intake manifold, so the pipe run is short.

-B


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## Mr Paddle.Shift (Dec 19, 2001)

bjacques said:


> You never have to worry about getting the *wastegate aerodynamics * wrong and ending up with huge spikes or nasty creep...


Just curious..what's wastegate aerodynamics?


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## bjacques (Feb 18, 2005)

Mr Paddle.Shift said:


> Just curious..what's wastegate aerodynamics?


Meaning flow into or out of the wastegate. If you mess this up, very bad things can happen, like rendering the wastegate useless, etc.


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## Mr Paddle.Shift (Dec 19, 2001)

I just didn't know the principles of _aerodynamics_ are used in designing a wastegate. Or maybe my thinking is way too old school.


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## FenPhen (Jan 13, 2004)

Malibubimmer said:


> Can someone explain to me why the chief of the M Division (and formerly head of AMG) would rule out supercharging a Bimmer, but not turbocharging it -- especially since he says "it's the result that matters, not how we generate it" ?
> 
> And why was he observed to be "grinning broadly"?


It's probably a dig at Mercedes, since they supercharge everything ("Kompressor").

Plus, he used to work at AMG. :dunno:


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## Malibubimmer (Sep 28, 2005)

FenPhen said:


> It's probably a dig at Mercedes, since they supercharge everything ("Kompressor").
> 
> Plus, he used to work at AMG. :dunno:


I believe they turbocharge the V12s.


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## bjacques (Feb 18, 2005)

Malibubimmer said:


> I believe they turbocharge the V12s.


They do turbocharge the V12's... Both the "standard" and the AMG to some truly insane power levels. The "standard" makes roughly 500hp and 600lb-ft... The AMG is about 600hp and 750lb-ft. I swear that's enough torque to move a battleship!




Mr Paddle.Shift said:


> I just didn't know the principles of aerodynamics are used in designing a wastegate. Or maybe my thinking is way too old school.


I know, it's a little counter-intuitive... But exhaust gas is subject to all of the physical laws of any other high-velocity gas (it can exit the port at as much as 350ft/sec!).

-Brendan


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## FenPhen (Jan 13, 2004)

bjacques said:


> They do turbocharge the V12's... Both the "standard" and the AMG to some truly insane power levels. The "standard" makes roughly 500hp and 600lb-ft... The AMG is about 600hp and 750lb-ft. I swear that's enough torque to move a battleship!


Yeah, twin-turbocharged.

Just for comparison, an Iowa-class battleship (fastest ones ever built) develops 212,000 shaft horsepower, which accounts for roughly 10% losses, at 2100 rpm... translates to ~590,000 ft.-lbs. of torque.  It also has a rough equivalent of a turbocharger.


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