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Author Topic:   GM Shows Orbital Combustion Process in V8

jimh posted 09-15-2007 12:46 AM ET (US)
According to a GM blog, the automaker is developing a 300-HP 4.3-liter V8 engine which will use the Orbital Combustion Process (OCP) from Orbital Corporation of Australia. This is the same combustion process used in the Mercury OptiMax.
The new engine, known as the XV8, will implement the technique in a substantially different way than Mercury has employed in their OptiMax outboard.
The most significant departure from the OptiMax configuration is the integration of the XV8's air compressor into the engine assembly. Alan Hayman of GM said the GM XV8's air compressor is "integrated to the back of the cylinder head and all of the fluids are transferred through this interface. This avoids the requirement for the myriad of hoses that would have traditionally been required including the avoidance of having to run a separate air-assist rail."
In the Mercury OptiMax the air compressor is a separate assembly which is bolted onto the engine and driven by a belt. The compressor is thought to have been produced from an old 2-HP outboard motor block. And there are plenty of hoses and fuel- and air-rails in the engine. The Mercury OptiMax was not a clean slate design, but an adaptation of OCP to an existing V6 outboard power head.
For more details on this XV8 OCP engine from GM, see:
/forums.gmsupercar.com/modules.php?name=News&file=showarticle&t=4& op=nextnewest
However, there are mentions of this engine going back to 2001, so it appears this may have been only a concept or prototype engine. I do not see anything that indicates it is going to be made in production volume. It is, however, a rare appearance of the OCP in an automobile engine. Will we see more from Orbital?
sosmerc posted 09-15-2007 08:26 PM ET (US)
Orbital has showcased a variety of auto engines with their system in the past. They had a six cylinder inline BMW that traveled around the country to demo their tech. Ford had a fleet of Fiestas with Orbital equipped DFI engines for a 2 year testing program that was completed years ago.
Many Orbital shareholders (such as myself) have been waiting "forever" for mass production in auto applications...but there must be some major stumbling block that keeps this from happening. DFI is no longer an Orbital exclusive technology. There are now competing systems. Indeed, there are already exiting cars on the road that are being powered by DFI equipped engines...but these systems are not Orbital.
I'd be more than happy just to see Merc and Nissan/Tohatsu continue to use Orbital and expand the use of the system to smaller engines in their lineup. And yes, it would be awesome to see an Orbital equipped 4 stroke outboard, especially if it is enhanced with either turbo or super charging.
GSH posted 09-17-2007 09:26 AM ET (US)
Sosmerc, could you please explain what the Orbital technology would have to offer a four-stroke engine? To me, the Orbital technology seems a little complex compaired to, say, the Volkswagen FSI. Am I missing something?
-Seb
sosmerc posted 09-17-2007 02:26 PM ET (US)
DFI on 4 strokes will improve performance while at the same time help reduce emissions. It does add some additional complexity and cost, but this is the price that has to be paid to extend the use of internal combustion engines. Eventually the advancements in injector design and precise engine controls will make DFI the next logical step and it will probably become as common as EFI within the next few years. Orbital has alot of experience with their system on both 2 and 4 stroke engines and is even perfecting ad adaptation of their system for various different fuels such as JP5, and even natural gas.
XStech posted 09-17-2007 04:45 PM ET (US)
"""could you please explain what the Orbital technology would have to offer a four-stroke engine?"""
Stratified charge.
GSH posted 09-17-2007 04:58 PM ET (US)
Thanks! Since you know alot about Orbital, can you also tell me why Tohatsu/Nissan 'only' have two star ratings for their DI two-strokes?
-Seb
XStech posted 09-17-2007 05:23 PM ET (US)
"""why Tohatsu/Nissan 'only' have two star ratings"""
I don't know why, but if I had to guess, I would say because they don't have to to be 3 star.

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Author	Topic: GM Shows Orbital Combustion Process in V8
jimh	posted 09-15-2007 12:46 AM ET (US) According to a GM blog, the automaker is developing a 300-HP 4.3-liter V8 engine which will use the Orbital Combustion Process (OCP) from Orbital Corporation of Australia. This is the same combustion process used in the Mercury OptiMax. The new engine, known as the XV8, will implement the technique in a substantially different way than Mercury has employed in their OptiMax outboard. The most significant departure from the OptiMax configuration is the integration of the XV8's air compressor into the engine assembly. Alan Hayman of GM said the GM XV8's air compressor is "integrated to the back of the cylinder head and all of the fluids are transferred through this interface. This avoids the requirement for the myriad of hoses that would have traditionally been required including the avoidance of having to run a separate air-assist rail." In the Mercury OptiMax the air compressor is a separate assembly which is bolted onto the engine and driven by a belt. The compressor is thought to have been produced from an old 2-HP outboard motor block. And there are plenty of hoses and fuel- and air-rails in the engine. The Mercury OptiMax was not a clean slate design, but an adaptation of OCP to an existing V6 outboard power head. For more details on this XV8 OCP engine from GM, see: /forums.gmsupercar.com/modules.php?name=News&file=showarticle&t=4& op=nextnewest However, there are mentions of this engine going back to 2001, so it appears this may have been only a concept or prototype engine. I do not see anything that indicates it is going to be made in production volume. It is, however, a rare appearance of the OCP in an automobile engine. Will we see more from Orbital?
sosmerc	posted 09-15-2007 08:26 PM ET (US) Orbital has showcased a variety of auto engines with their system in the past. They had a six cylinder inline BMW that traveled around the country to demo their tech. Ford had a fleet of Fiestas with Orbital equipped DFI engines for a 2 year testing program that was completed years ago. Many Orbital shareholders (such as myself) have been waiting "forever" for mass production in auto applications...but there must be some major stumbling block that keeps this from happening. DFI is no longer an Orbital exclusive technology. There are now competing systems. Indeed, there are already exiting cars on the road that are being powered by DFI equipped engines...but these systems are not Orbital. I'd be more than happy just to see Merc and Nissan/Tohatsu continue to use Orbital and expand the use of the system to smaller engines in their lineup. And yes, it would be awesome to see an Orbital equipped 4 stroke outboard, especially if it is enhanced with either turbo or super charging.
GSH	posted 09-17-2007 09:26 AM ET (US) Sosmerc, could you please explain what the Orbital technology would have to offer a four-stroke engine? To me, the Orbital technology seems a little complex compaired to, say, the Volkswagen FSI. Am I missing something? -Seb
sosmerc	posted 09-17-2007 02:26 PM ET (US) DFI on 4 strokes will improve performance while at the same time help reduce emissions. It does add some additional complexity and cost, but this is the price that has to be paid to extend the use of internal combustion engines. Eventually the advancements in injector design and precise engine controls will make DFI the next logical step and it will probably become as common as EFI within the next few years. Orbital has alot of experience with their system on both 2 and 4 stroke engines and is even perfecting ad adaptation of their system for various different fuels such as JP5, and even natural gas.
XStech	posted 09-17-2007 04:45 PM ET (US) """could you please explain what the Orbital technology would have to offer a four-stroke engine?""" Stratified charge.
GSH	posted 09-17-2007 04:58 PM ET (US) Thanks! Since you know alot about Orbital, can you also tell me why Tohatsu/Nissan 'only' have two star ratings for their DI two-strokes? -Seb
XStech	posted 09-17-2007 05:23 PM ET (US) """why Tohatsu/Nissan 'only' have two star ratings""" I don't know why, but if I had to guess, I would say because they don't have to to be 3 star.