# Throttle on a diesel?



## lpcapital (Mar 1, 2007)

A simple question: we all know that in Diesel engines, power output is regulated with the amount of fuel, not the amount of air... So why is there a throttle valve on BMW (and maybe other) Diesel engines? (it's right in front of the EGR valve)

Does it have to do with emissions? Or is it a way to provide engine brake (because we all know that Diesel engines, since don't have a throttle, basically have no inherent engine brake... And why big rigs make that loud noise when engine braking...)?


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## F32Fleet (Jul 14, 2010)

#1 To prevent a runaway. http://en.m.wikipedia.org/wiki/Diesel_engine_runaway

#2 Big Rigs have a "Jake Brake". http://en.m.wikipedia.org/wiki/Compression_release_engine_brake


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## lpcapital (Mar 1, 2007)

I like the idea of the throttle to be a safety in case of runaway.

Maybe in response to situation like these: 
https://www.youtube.com/watch?v=M-pxsViKF88&feature=youtube_gdata_player?

As far as the brake, we know the X5 doesn't have the compression brake. However I was surprised of the amount of engine brake on the car (much comparable to my gasoline Z4): could it be that at 0 throttle the throttle valve closes?

Sent from BimmerApp mobile app


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## d geek (Nov 26, 2008)

discussed at length here:
http://www.bimmerfest.com/forums/showthread.php?t=709379


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## BB_cuda (Nov 8, 2011)

A different point of view to offer. A friend of mine that went through mechanical engineering school at same time as I is a turbo diesel expert. He has worked at Aerodyne (turbo house in Dallas), Cummins, Catapillar, John Deer, and now Komatsu. He did what he termed "air handling" for a 76L engine for a giant mining dump truck for Cat (he was a Cummins employee then). It produced ~3500 hp.

I discussed (only a 30 min phone call) the emissions aspects of our 3L turbo diesel as well as JBD boxes. We came upon the subject of the throttle in the context of the high pressure EGR. He strongly felt that the only reason that the throttle was there was to allow a local reduced pressure temporarily (perhaps 300 msec) to allow EGR pressure. He says in the earlier days the delta P across the engine was positive and it was easier as you didn't have to fight the pumping losses associated with a negative delta P. His point is the pressure at the point of EGR injection is likely lower than the incoming charge pressure coming from the intercooler. By partial close of the throttle, the down stream pressure can be reduced so that exhaust can flow into the inlet stream otherwise charge pressure would try to back flow into EGR tract.

I'm not discounting point of runaway though. The guy is a turbo system designer and knows his stuff. Off topic, he asked two things about our turbos.
*1) who makes them for BMW?
2) Are the turbos variable geometry? (this means the vanes move to change the pitch angle to augment boost)*
He recommended that I speak with Gale Banks concerning enhancements to our system. He personally knows him. Gale wanted to hire him but my friend declined.

I will continue dialogue with him this weekend when we both have more time.


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## d geek (Nov 26, 2008)

BB_cuda said:


> A different point of view to offer. A friend of mine that went through mechanical engineering school at same time as I is a turbo diesel expert. He has worked at Aerodyne (turbo house in Dallas), Cummins, Catapillar, John Deer, and now Komatsu. He did what he termed "air handling" for a 76L engine for a giant mining dump truck for Cat (he was a Cummins employee then). It produced ~3500 hp.
> 
> I discussed (only a 30 min phone call) the emissions aspects of our 3L turbo diesel as well as JBD boxes. We came upon the subject of the throttle in the context of the high pressure EGR. He strongly felt that the only reason that the throttle was there was to allow a local reduced pressure temporarily (perhaps 300 msec) to allow EGR pressure. He says in the earlier days the delta P across the engine was positive and it was easier as you didn't have to fight the pumping losses associated with a negative delta P. His point is the pressure at the point of EGR injection is likely lower than the incoming charge pressure coming from the intercooler. By partial close of the throttle, the down stream pressure can be reduced so that exhaust can flow into the inlet stream otherwise charge pressure would try to back flow into EGR tract.
> 
> ...


Interesting input. Thanks for sharing that. His explanation of the temporary use of the EGR butterfly to allow more EGR flow makes sense and validates what the other poster was saying in that other thread. Thanks for the info.
1) google searching led me to this: "Borg Warner - 3K - Schwitzer" I think B W is OEM.
2) I recall that at least one of the turbos was VNT, but haven't been able to verify yet.


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## Hoooper (Jun 17, 2013)

I can confirm that the turbos are Borg-Warner. K26 is the small turbo and kp39 is the bigger turbo. On the variable geometry portion supposedly either one or both is variable geometry, I have not really checked on the borg warner sheet to find out though since I dont really have any interest in messing with the turbos


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## floydarogers (Oct 11, 2010)

The 328d uses a single "variable geometry" turbo. So does the newer N57 for the 530d version.


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## lpcapital (Mar 1, 2007)

All this is great info: say thanks to your friend!!!

I would be curious on a couple of other things:
1) why not only use a LP EGR since it allows to use after DPF exhaust, cooler-denser, and greater flow? I suspect it has to do with delta P and pumping losses
2) what are the development of using variable cam timing to do internal recirculation
3) any other interesting development in reducing tailpipe NOx, with less EGR, thus recuperating the efficiency of pre-EGR diesel engines?


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## F32Fleet (Jul 14, 2010)

d geek said:


> Interesting input. Thanks for sharing that. His explanation of the temporary use of the EGR butterfly to allow more EGR flow makes sense and validates what the other poster was saying in that other thread. Thanks for the info.
> 1) google searching led me to this: "Borg Warner - 3K - Schwitzer" I think B W is OEM.
> 2) I recall that at least one of the turbos was VNT, but haven't been able to verify yet.


M57: fixed vane turbos. N57: variable vane.


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## F32Fleet (Jul 14, 2010)

BB_cuda said:


> A different point of view to offer. A friend of mine that went through mechanical engineering school at same time as I is a turbo diesel expert. He has worked at Aerodyne (turbo house in Dallas), Cummins, Catapillar, John Deer, and now Komatsu. He did what he termed "air handling" for a 76L engine for a giant mining dump truck for Cat (he was a Cummins employee then). It produced ~3500 hp.
> 
> I discussed (only a 30 min phone call) the emissions aspects of our 3L turbo diesel as well as JBD boxes. We came upon the subject of the throttle in the context of the high pressure EGR. He strongly felt that the only reason that the throttle was there was to allow a local reduced pressure temporarily (perhaps 300 msec) to allow EGR pressure. He says in the earlier days the delta P across the engine was positive and it was easier as you didn't have to fight the pumping losses associated with a negative delta P. His point is the pressure at the point of EGR injection is likely lower than the incoming charge pressure coming from the intercooler. By partial close of the throttle, the down stream pressure can be reduced so that exhaust can flow into the inlet stream otherwise charge pressure would try to back flow into EGR tract.
> 
> ...


Interesting, and makes complete sense. I guess we would know if one of you guys with your software could find out where the throttle is simply open/close.


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## d geek (Nov 26, 2008)

Hoooper said:


> I can confirm that the turbos are Borg-Warner. K26 is the small turbo and kp39 is the bigger turbo. On the variable geometry portion supposedly either one or both is variable geometry, I have not really checked on the borg warner sheet to find out though since I dont really have any interest in messing with the turbos


Well, I thought that was a VNT, but here is what on B-W site:
"_With our *KP* and K0 turbocharger ranges, *which use waste gates*, we offer you sophisticated and high performance turbocharging systems for low to mid power densities.

The range stretches from the extremely compact KP31, right up to the K03 for light commercial vehicles. With this range we offer seamless coverage for engine displacements from approximately 0.8 to 3.0 liters - and provide you with the best possible turbocharger based on your requirements and the space available.

The K turbochargers are particularly affordable, yet are highly robust and manufactured to the familiar, high BorgWarner quality standards.

Our *BV range* includes pioneering turbocharging systems *with variable turbine geometry *which ensure precise adjustment to the respective engine operating points. Optimum power output with the greatest fuel efficiency is the result of this advanced technology.

The BV turbochargers achieve their extremely high degree of efficiency through a CFD-optimized and BorgWarner patented vane design. A robust VTG mechanism ensures that the turbocharger operates efficiently, reliably and durably, even under the toughest of conditions.

The BV turbochargers can be combined with pneumatic actuators with position sensors or with electrical actuators. For applications with severe thermal loads, we also offer water-cooled bearing casings as an option. The BV range stretches from the BV35 right up to the BV50 and thereby covers diesel engines with displacements of 1.2 to 3.0 liters_."


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## lpcapital (Mar 1, 2007)

BMWTurboDzl said:


> M57: fixed vane turbos. N57: variable vane.


That's quite a broad generalization and it is inaccurate. There's a ton of M57 with different exhaust configurations some fixed, some variable. Same with the N57. This the famus N57S of the 50d that has 3 turbo 2 variable and one fixed.

In the specific of the version of M57 mounted on the 335d and the X5 35d for the US market it has two exhaust turbocharger, one HP and one LP. The HP is fixed while the LP is variable geometry. Looking down on the engine bay, the HP sits up top, while the LP is below. It's hard to see the actuator of the vanes since it's underneath, but is there. The size of the housing is also a clue.

The diagram in the white paper about BMW Advance Diesel can be confusing, but it clearly show a turbine control valve at #26: at first I thought was some kind of valve or a bypass but #26 is the controller of the LP vanes.

I have no clue what is the model designation of the turbine and who makes them.


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## F32Fleet (Jul 14, 2010)

lpcapital said:


> That's quite a broad generalization and it is inaccurate. There's a ton of M57 with different exhaust configurations some fixed, some variable. Same with the N57. This the famus N57S of the 50d that has 3 turbo 2 variable and one fixed.
> 
> In the specific of the version of M57 mounted on the 335d and the X5 35d for the US market it has two exhaust turbocharger, one HP and one LP. The HP is fixed while the LP is variable geometry. Looking down on the engine bay, the HP sits up top, while the LP is below. It's hard to see the actuator of the vanes since it's underneath, but is there. The size of the housing is also a clue.
> 
> ...


I'm about 90 sure the M57 in our cars does not have VVT. I'm going off literature I read in 2007. IIRC one of the advancements of the N57 was the introduction of VVT.


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## Hoooper (Jun 17, 2013)

Wait vvt or vnt/vgt/vtg? Vvt typically means variable valve timing which would be something new at least from ours. Haven't heard vvt used for variable turbo but I guess that could stand for variable vane turbo.


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## F32Fleet (Jul 14, 2010)

Hoooper said:


> Wait vvt or vnt/vgt/vtg? Vvt typically means variable valve timing which would be something new at least from ours. Haven't heard vvt used for variable turbo but I guess that could stand for variable vane turbo.


I'm incorrect.


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