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#1
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
Here's some pics of a compound twin turbo setup on a Cummins.
![]() ![]() Like the name implies, compound turbocharging compounds the boost. The first turbo compresses the air charge to ~30 psi* into the second turbo which yields ~60* pounds of boost into the intake manifold. (*Arbitrary numbers) How does the second turbo not surge, spin twice as fast and blow up? Simply, compressor surge and compressor speed are not directly related to the amount of airflow through the turbo but rather the amount of boost the turbo is trying to create. While both turbos are creating ~30 pounds of boost more than the inlet pressure, they are behaving the same. The above explanation is assuming two equal sized turbos, some of the truly insane compound setups involve two "small" 90mm+ turbos right off the header pressurizing the inlet on a massive 100mm+ single turbo. These are the 100-150psi 2,000-4,000bhp engines used in tractor pulls. |
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#2
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
More pics: http://www.texasdieselworks.com/twinspics/
QUOTE Want serious lungs for your Cummins Dodge? BD’s Super B Twin Turbo is a smart choice from a variety of standpoints. Why two turbos? It’s not just about doubling the amount of boost available by adding a second turbo, though you’ll generate much more boost than a stock single turbo unit. It’s more about broadening the power available over a much wider rpm range. The two turbos have different boost characteristics that compound each other. The smaller turbo spools up faster and gives more boost and power at lower rpms. The second unit is larger and spools up slowly, but has the capacity to offer more boost at higher engine speeds. When combined with increases in fuel rate, rear-wheel-power outputs of 500 horses are possible. What’s more, the increased airflow has a cooling effect if sensible fuel rates are used. For example, one test showed that at a rear-wheel-power output of 450 horses at 51psi boost, a 2002 Cummins developed an EGT of only 1175 degrees and low smoke levels. For more info, contact BD at 800-887-5030 or see www.dieselperformance.com
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#3
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![]() International Superstar ![]() ![]() ![]() ![]() ![]() Group: Moderators Posts: 7,121 Joined: 26-August 03 From: Connecticut, USA Member No.: 5 Car: 2002 BMW M3 ![]() |
that is a cool looking turbo setup. interesting stuff. i always wondered how they got such insane power out of turbo diesels.
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#4
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Uh been around for awhile.
Ever hear of sequential turbos? |
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#5
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Living the dream ![]() ![]() ![]() ![]() ![]() Group: Moderators Posts: 8,859 Joined: 27-August 03 Member No.: 28 Car: Ford F-150, Mercury Grand Marquis, Volkswagen Beetle ![]() |
How fast do turbos typically spin? I'm going to guess around 30,000RPM. We have some turbomolecular pumps in the lab that spin at that speed and they sound about the same. We also have a roots booster pump that sounds like a supercharger. It's like working in a performance shop sometimes except much cleaner.
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#6
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![]() That Frigging BMW Driver ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 6,727 Joined: 7-December 03 From: Raleigh, NC Member No.: 222 Car: 1997 BMW 328i ![]() |
that's an interesting setup.
I am such a diesel nerd, it's not funny. Has anyone seen the stock Holset turbo that's on the Cummins? That's a big motherfuckin' hairdryer, yo. that's an interesting setup. I am such a diesel nerd, it's not funny. Has anyone seen the stock Holset turbo that's on the Cummins? That's a big motherfuckin' hairdryer, yo. |
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#7
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
Uh been around for awhile. Ever hear of sequential turbos? Sequential turbo setups are completely different. They use a series of vacumn activated control valves to route the exhaust gases and intake air through a small turbo at low RPM and through a larger turbo at high RPM. Sequential turbo setups were perfected in the early 90's at about the same time single turbos were made efficient enough to render them obsolete. Currently the only production vehicles that use sequential systems are turbodiesel passenger cars, notably BMW. Full explanation of Sequential Turocharging and diagrams of Supra TT setup. ![]() How fast do turbos typically spin? I'm going to guess around 30,000RPM. 115,000 RPM at full boost, off idle they spin at ~30K so admittedly the sound would be the same. |
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#8
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![]() Talkin' the talk since 2003 ![]() ![]() ![]() ![]() ![]() ![]() Group: Admin Posts: 28,271 Joined: 27-August 03 From: Seattle, WA Member No.: 27 Car: 2004 VW GTI 1.8T ![]() |
I was just waiting for somebody to confuse it with sequential turbos...
It's a cool idea; seems like it offers a lot of the benefits of sequential turbos without the problems of trying to make the pass off from small to large turbo smooth and predictable. |
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#9
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Its the exact same concept as a sequential turbo.
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#10
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Grease Monkey ![]() ![]() Group: Members Posts: 205 Joined: 23-January 05 Member No.: 1,430 ![]() |
Wonderful images
![]() I know diesels are less affected by inlet temperature due to the wasted air fuel ratios - but the inlet temperature at 4 bars must be immense? A simpler way of looking at turbo sizing in compound applications is looking at pressure ratio and not boost or flow per se. The turbo is only affected by the difference between inlet and outlet pressure (within reasonable levels obviously) - so wether the inlet sees slightly below ambient or 2.0 bars makes little difference. Which is partly why turbocharging is such a benefit for high altitude four stroke engines. I'm a bit intrigued by the description of different sized turbos in a compound setup. I wathced a two stage compound similar turbo setup on a street driven Merc once, the thing had the most insane boost rush I've ever seen. When provoked (i.e. driven from idle in gear) it went like lagging.... lagging... wheeeEEEEEEE *surge* *SURGE* *WHOOOOOOOSH* When boost arrived i shot a black jet of compact smoke several meters out the tailpipe and promptly went sideways with crazy wheelspin in third! Useless but fun to watch ![]() |
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#11
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
It's a cool idea; seems like it offers a lot of the benefits of sequential turbos without the problems of trying to make the pass off from small to large turbo smooth and predictable. Definitely, the compound setup provides the holy grail of turbocharging, massive low end power and torque while still maintaining top end boost and efficiency, too bad it only works on diesels. Since cooling the air charge to prevent detonation isn't an issue, there's no intercooler and ancillary piping and no intake piping. This setup is much lighter and more compact than any gasoline multi-turbo setup could ever be. Pretty amazing stuff. |
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#12
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![]() Talkin' the talk since 2003 ![]() ![]() ![]() ![]() ![]() ![]() Group: Admin Posts: 28,271 Joined: 27-August 03 From: Seattle, WA Member No.: 27 Car: 2004 VW GTI 1.8T ![]() |
Its the exact same concept as a sequential turbo. It works very differently...and I wouldn't even call it the same concept anyway, it's just trying to solve the same problem that sequential turbos are trying to solve. But there I go arguing semantics again so nevermind me... |
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#13
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Why wouldn't you want an intercooler....?
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#14
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
Why wouldn't you want an intercooler....? The primary porpose of an intercooler on a gasoline engine is to cool the intake charge as a safeguard against detonation. Since diesels are compression fired, every cylinder firing is controlled detonation. An intercooler on a turbodiesel would only yield insignificant power gains. Most stock turbodiesels use intercoolers for emissions and fuel economy, not specifically for performance. |
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#15
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Uhm not really. Intercoolers offer a bigger advantage of being able to cool the flow of hot compressed air. Cooler intake air means a denser gas which means better burn.
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#16
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![]() Aeternum vale ![]() ![]() ![]() ![]() Group: Members Posts: 4,810 Joined: 6-March 04 Member No.: 636 ![]() |
As if 60-100psi wasn't dense enough?
My point is that, unlike high boost gasoline engines, intercoolers aren't critical equipment. |
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#17
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![]() Talkin' the talk since 2003 ![]() ![]() ![]() ![]() ![]() ![]() Group: Admin Posts: 28,271 Joined: 27-August 03 From: Seattle, WA Member No.: 27 Car: 2004 VW GTI 1.8T ![]() |
Dayum PBB, that's what we call OWNAGE
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#18
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Dude PV=nRT. If you take two gases at the same pressure the cooler one will always be denser...
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#19
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![]() Talkin' the talk since 2003 ![]() ![]() ![]() ![]() ![]() ![]() Group: Admin Posts: 28,271 Joined: 27-August 03 From: Seattle, WA Member No.: 27 Car: 2004 VW GTI 1.8T ![]() |
You're talking about changing (delta)p from 85 psi to 86. It's insignificant.
It's not like in a gasoline powered turbocharged engine where a PSI makes for a 5-15% difference in the pressure. This is barely a percent. So why spend the money on an intercooler? |
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#20
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![]() I will stand, or I will fall. But I will not sit. ![]() ![]() ![]() ![]() ![]() ![]() Group: Members Posts: 13,576 Joined: 4-September 03 From: Somewhere between Chicago and Indianapolis Member No.: 58 Car: Miata & RX-7 ![]() |
Wtf? I'm not talking about changing the pressure at all...
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Lo-Fi Version | Time is now: 26th April 2018 - 05:00 PM |