Turbo Compounding
10-01-2009, 08:54 AM
#2
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I doubt it. Cummins seems to be set using VGT to drive the required amount of egr. Ford is the only one now using compounded turbo's , and once again that is for emissions not performance. Cat used compounds for the accerts but has since discontinued manufacturing over the road engines. I believe Detroit was experimenting with a compound design, but the second turbo was linked directly to the drive line and did not increase manifold pressure.
10-01-2009, 09:08 AM
#3
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Just watched DD's promotional video on their DD15 where they claim it adds 50 free hp and improves fuel economy by 5%. I'm a total n00b, so some of what you said went over my head, to be perfectly honest. 
Any chance you wouldn't mind explaining your comment a bit further in lamens terms?
Can you also confirm that my understanding of DD's setup is that it's just another turbine that runs an electrical motor to push the driveline? Are there other types of turbo compounding or am I just way off to begin with?
Any chance you wouldn't mind explaining your comment a bit further in lamens terms?
Can you also confirm that my understanding of DD's setup is that it's just another turbine that runs an electrical motor to push the driveline? Are there other types of turbo compounding or am I just way off to begin with?
10-01-2009, 09:31 AM
#4
Administrator ........ DTR's puttin fires out and workin on big trucks admin
Just watched DD's promotional video on their DD15 where they claim it adds 50 free hp and improves fuel economy by 5%. I'm a total n00b, so some of what you said went over my head, to be perfectly honest.
Any chance you wouldn't mind explaining your comment a bit further in lamens terms?
Can you also confirm that my understanding of DD's setup is that it's just another turbine that runs an electrical motor to push the driveline? Are there other types of turbo compounding or am I just way off to begin with?
Any chance you wouldn't mind explaining your comment a bit further in lamens terms?
Can you also confirm that my understanding of DD's setup is that it's just another turbine that runs an electrical motor to push the driveline? Are there other types of turbo compounding or am I just way off to begin with?
Ford uses compound turbo's to drive egr (exhaust gas recirculation) to lower harmful emissions, Cat uses them for mostly same reasons with the only exception they don't use EGR. Cat got out of the class 8 engine market due to the new emission standards. OTR truck engines were a very small percentage of their overall business.
Cummins along with Navistar, DD, Isuzu, Hino,all went with VGT- variable geometry turbo. The turbo has multiple air discharge veins within the housing to accommodate variable flow rates based on certain conditions and demand. VGT's do not use a waste gate like a normal turbo,they exhaust excess air pressure back into the intake. VGT's were implemented solely as an emission control device, however they are used as an integrated exhaust brake, an added bonus.
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10-01-2009, 12:43 PM
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The DD15 is not 2 turbos. the 1st is a Holset HX55, no wastegate, no VGT, no VNT. the second is a turbine that drives a small gearbox with fluid coupler that puts power directly into the flywheel via a small drive pinion much like the starter gear. its always engauged but has an overrunning clutch on the drive gear.
10-01-2009, 02:49 PM
#6
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I think DD turbo was linked to some kind of gearbox. I am not completely sure. I read it in one of the heavy truck repair monthlies I get.
Ford uses compound turbo's to drive egr (exhaust gas recirculation) to lower harmful emissions, Cat uses them for mostly same reasons with the only exception they don't use EGR. Cat got out of the class 8 engine market due to the new emission standards. OTR truck engines were a very small percentage of their overall business.
Ford uses compound turbo's to drive egr (exhaust gas recirculation) to lower harmful emissions, Cat uses them for mostly same reasons with the only exception they don't use EGR. Cat got out of the class 8 engine market due to the new emission standards. OTR truck engines were a very small percentage of their overall business.
Cummins along with Navistar, DD, Isuzu, Hino,all went with VGT- variable geometry turbo. The turbo has multiple air discharge veins within the housing to accommodate variable flow rates based on certain conditions and demand. VGT's do not use a waste gate like a normal turbo,they exhaust excess air pressure back into the intake. VGT's were implemented solely as an emission control device, however they are used as an integrated exhaust brake, an added bonus.
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So can you not have a VGT that compounds as well? Is one design more efficient than the other?
Also, 1-5-3-6-2-4, thanks for the pics. These are some awesome looking machines.
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10-01-2009, 06:16 PM
#8
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Seems to be a bit of confusion here between compound turbos and turbocompounding.
Compound turbos is two turbos in series, the larger feeding the smaller.
Turbocompounding uses an exhaust turbine to feed power into the crankshaft. There may or may not be a turbocharger installed on a turbocompounded engine. One of the most successful turbocompounded engines was the Wright R-3350, it was supercharged by a gear driven centrifugal supercharger rather than being turbocharged.
I think turbocompounding is a great idea, it recovers heat energy that would normally be wasted and converts it to usable power. I don't see it appearing on small engines like the B series Cummins. Think about it this way: A "B" Cummins is less than half the displacement of a DD15, meaning it puts out roughly half the exhaust - thus you only stand to gain 25 HP at best. Under light load the turbocompound stuff is just along for the ride. The added cost, weight, and complexity of the turbocompound unit just doesn't make sense except on a big engine that works hard all the time. I do think it will spread down to the 12 liter class of engines, but I don't see it hitting the 8 - 10 liter range any time soon.
Compound turbos is two turbos in series, the larger feeding the smaller.
Turbocompounding uses an exhaust turbine to feed power into the crankshaft. There may or may not be a turbocharger installed on a turbocompounded engine. One of the most successful turbocompounded engines was the Wright R-3350, it was supercharged by a gear driven centrifugal supercharger rather than being turbocharged.
I think turbocompounding is a great idea, it recovers heat energy that would normally be wasted and converts it to usable power. I don't see it appearing on small engines like the B series Cummins. Think about it this way: A "B" Cummins is less than half the displacement of a DD15, meaning it puts out roughly half the exhaust - thus you only stand to gain 25 HP at best. Under light load the turbocompound stuff is just along for the ride. The added cost, weight, and complexity of the turbocompound unit just doesn't make sense except on a big engine that works hard all the time. I do think it will spread down to the 12 liter class of engines, but I don't see it hitting the 8 - 10 liter range any time soon.
10-04-2009, 09:38 AM
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Thanks for clearing that up Dave-- a lot of people are confused by the difference between "turbocompounding" and "compound turbos" and I think you explained it well.
Cummins experimented with turbocompounding on an L10-- the proto sits in the tech ctr breezeway near the all-aluminum B series.
Turbocompounding as used on the DD15 is not a new idea, but it's somewhat new to the OTR market. Initial test data from what I have heard shows that the DD15 is going to be the only real competition for the new ISX in terms of mpg and power.
With a fixed frame (non VGT) turbo, the turbocompounding will be most efficient when the actual turbocharger isn't taking much energy from the drive stream. The more power goes to the turbine of the turbocharger, the less is left for the turbocompound turbine. So turbocompounding actually helps the most at steady state light cruise as far efficiency.
As load on the engine increases, the turbocompound will increase the power it adds, but by ever-decreasing amounts. In other words, it's becoming a much smaller piece of a much larger pie.
One nice thing about turbocompounding is that it can help with launch out of the hole if an engine is lacking that. Note how the DD15 has peak torque at slightly lower RPM:
Meanwhile, the ISX continues with the 1200 RPM peak that is the "standard" point. This is mostly because the existing transmission gearing and axle gearing on the market and also because the ISX has plenty of pull on bottom. Besides, OTR engines spend most of their time over 1200 rpm cruising on the road, and Cummins designed the coming ISX with fuel economy being the single greatest design goal-- and that means not compromising the more important parts of the power band to add bottom end pull that no one really has been asking for.
Maxxforce is going to be a bust (and when Wal-Mart ordered a TON of new INternational ProStars, not a *single* one has International's own Maxxforce in it!).
Cat is no longer a player (and hasn't been since 05 or so when their ACERT engines will exposed as junk).
Cummins experimented with turbocompounding on an L10-- the proto sits in the tech ctr breezeway near the all-aluminum B series.
Turbocompounding as used on the DD15 is not a new idea, but it's somewhat new to the OTR market. Initial test data from what I have heard shows that the DD15 is going to be the only real competition for the new ISX in terms of mpg and power.
With a fixed frame (non VGT) turbo, the turbocompounding will be most efficient when the actual turbocharger isn't taking much energy from the drive stream. The more power goes to the turbine of the turbocharger, the less is left for the turbocompound turbine. So turbocompounding actually helps the most at steady state light cruise as far efficiency.
As load on the engine increases, the turbocompound will increase the power it adds, but by ever-decreasing amounts. In other words, it's becoming a much smaller piece of a much larger pie.
One nice thing about turbocompounding is that it can help with launch out of the hole if an engine is lacking that. Note how the DD15 has peak torque at slightly lower RPM:
Meanwhile, the ISX continues with the 1200 RPM peak that is the "standard" point. This is mostly because the existing transmission gearing and axle gearing on the market and also because the ISX has plenty of pull on bottom. Besides, OTR engines spend most of their time over 1200 rpm cruising on the road, and Cummins designed the coming ISX with fuel economy being the single greatest design goal-- and that means not compromising the more important parts of the power band to add bottom end pull that no one really has been asking for.
Maxxforce is going to be a bust (and when Wal-Mart ordered a TON of new INternational ProStars, not a *single* one has International's own Maxxforce in it!).
Cat is no longer a player (and hasn't been since 05 or so when their ACERT engines will exposed as junk).
10-04-2009, 10:13 PM
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Cat is no longer a player (and hasn't been since 05 or so when their ACERT engines will exposed as junk).
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Being 07 Cat certed..........I'm giving you that one. Past Cat shop boss, I hated the updates on those engines. Cat seems to think they have enough Off Road funds coming in, they don't need the on road.
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Being 07 Cat certed..........I'm giving you that one. Past Cat shop boss, I hated the updates on those engines. Cat seems to think they have enough Off Road funds coming in, they don't need the on road.
10-05-2009, 08:55 PM
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Pat, it's an old concept engine (P-pump) that was briefly explored. It drops about 133# off the engine when it's aluminum blocked.
Alas, Aluminum isn't a good block material for commercial duty type engines where weight isn't much of a factor. It's lots of bona fide cost for dubious benefit.
Think about it: you'd pay another $2500 or so to drop the equivalent of half a Reunel bumper or so...
Justin
Alas, Aluminum isn't a good block material for commercial duty type engines where weight isn't much of a factor. It's lots of bona fide cost for dubious benefit.
Think about it: you'd pay another $2500 or so to drop the equivalent of half a Reunel bumper or so...
Justin
10-06-2009, 07:58 AM
#14
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Pat, it's an old concept engine (P-pump) that was briefly explored. It drops about 133# off the engine when it's aluminum blocked.
Alas, Aluminum isn't a good block material for commercial duty type engines where weight isn't much of a factor. It's lots of bona fide cost for dubious benefit.
Think about it: you'd pay another $2500 or so to drop the equivalent of half a Reunel bumper or so...
Justin
Alas, Aluminum isn't a good block material for commercial duty type engines where weight isn't much of a factor. It's lots of bona fide cost for dubious benefit.
Think about it: you'd pay another $2500 or so to drop the equivalent of half a Reunel bumper or so...
Justin
But I would pay $2500 to have the only one in the world....... Polished up, that thing would look good in Greenie.
10-06-2009, 03:01 PM
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Some companies are going CGI for blocks and such. I think CGI is a good block material, but the coming ISX will continue with gray iron. It costs a lot less to make and TONS less to machine. CGI is very tough on the tooling, because your machine tools will hit those carbide flakes and dull quickly.
Grey iron is lower cost for Cummins and for Cummins Customers who depend on being able to get affordable rebuilds/recon engines. It also has good damping that helps make the engine quieter.
I think Cummins will eventually go CGI, but it will be a long time away. There's just not much demand for it, and Cummins' customers have made it pretty clear that they're not interesting in paying another grand or two (or more!) for an engine that's a little lighter.
The coming ISX block is more of an evolution of the same old ISX block that's been around for awhile. So it's not really a good call to make the exact same design out of CGI.
Only when they radically retool the block will it make sense to switch.
Grey iron is lower cost for Cummins and for Cummins Customers who depend on being able to get affordable rebuilds/recon engines. It also has good damping that helps make the engine quieter.
I think Cummins will eventually go CGI, but it will be a long time away. There's just not much demand for it, and Cummins' customers have made it pretty clear that they're not interesting in paying another grand or two (or more!) for an engine that's a little lighter.
The coming ISX block is more of an evolution of the same old ISX block that's been around for awhile. So it's not really a good call to make the exact same design out of CGI.
Only when they radically retool the block will it make sense to switch.