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962 962 is offline
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Single or Twin Turbo with EFI

Is it that much more expensive to build a twin vs a single?

What are your thoughts ??





Old 06-05-2012, 06:53 AM
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It depends on what turbos etc you use. It is not necessarily more expensive but twins would be my choice (and it is on my 2.5 SS turbo build) on 911 engine.
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Old 06-05-2012, 12:18 PM
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twins would cost much more due to the added fab work involved in making it all fit. I considered twins on my 930 till I realized the amount of work it would take
Old 06-05-2012, 01:14 PM
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Under 650 a single over twins or if you want faster spooling or just WANT them, then just do it!! But.... If you want BIG numbers you will have spooling just like a big single but top end well above a big single. It just takes 1 extra turbo + 1 extra waste gate + 1 extra blow off valve. If you can fabricate then thats good for you. But if your having someone doing the work for you it starts adding up. You still need to fabricate the same components just adding the exta items into the mix. The turbo technology of today has brought us fast spooling singles that can perform just as good as twins from 15 years ago and pull just as hard. It boils down to fabrication required, performance and specific wants.

Last edited by GJF; 06-05-2012 at 01:42 PM..
Old 06-05-2012, 01:39 PM
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I can speak from experience - YES.....





Although I wouldn't necessarily say that its twice as expensive, there is considerably more cost to do a Twin Turbo build. The main reason that I found for this is nearly everything that you need is "custom" as there isn't a lot of aftermarket parts out there for TT builds. From the headers, turbo mounting, waste gates, fresh air plumbing, inter-cooler, oil supply to the oil return - everything needed to be custom fabricated or made.

One benefit that I have from doing this project is that I am now the proud owner of a MIG welder, TIG welder, vertical milling machine and a lathe - as I found that it was more cost effective to do the work myself.

I was aiming for HP as well as "looks" therefore I was determined to do a TT build. However if I had to do it all over again I would likely call Chris at Turbokraft and order a complete, large single turbo engine that incorporates proven / tested components.

Richard
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Old 06-05-2012, 07:31 PM
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Quote:
Originally Posted by drmatera View Post
twins would cost much more due to the added fab work involved in making it all fit. I considered twins on my 930 till I realized the amount of work it would take
If it is custom anyway, then there is only minor difference. Of course, I am talking from the DIY-er perspective, obviously having it all made will cost some significant money but that applies to single turbo also.

And you don't need extra BOV. Why would one run separate banks at all after compressors? I personally will use only one wastegate also for two turbos to eliminate syncing problems between turbos.
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Old 06-05-2012, 09:55 PM
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I would recommend contacting Pat Williams Racing. They specialize in TT Porsches and while work is custom, economy of scale will apply to some degree. When it's time for my rebuild, I will go with TT as my use is 99% track.
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Old 06-06-2012, 03:46 AM
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Quote:
Originally Posted by motley911 View Post
I can speak from experience - YES.....





Although I wouldn't necessarily say that its twice as expensive, there is considerably more cost to do a Twin Turbo build. The main reason that I found for this is nearly everything that you need is "custom" as there isn't a lot of aftermarket parts out there for TT builds. From the headers, turbo mounting, waste gates, fresh air plumbing, inter-cooler, oil supply to the oil return - everything needed to be custom fabricated or made.

One benefit that I have from doing this project is that I am now the proud owner of a MIG welder, TIG welder, vertical milling machine and a lathe - as I found that it was more cost effective to do the work myself.

I was aiming for HP as well as "looks" therefore I was determined to do a TT build. However if I had to do it all over again I would likely call Chris at Turbokraft and order a complete, large single turbo engine that incorporates proven / tested components.

Richard
Richard - awesome build, what did you end up with for power and torque?
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Old 06-06-2012, 03:48 AM
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BOV are only to protect the thrust bearings and to help faster boost recovery between shifts. And you don't divide banks from one another . The BOV many times is placed after the IC which does nothing that it is intended to do other than make RICER sounds. They need to be placed as close to the compresser as close as possible to work properly. One waste gate could be used but there is no synchronization between turbos or waste gates it all just combines to the intake. If the wastegate isnt sized properly and or the routing of the exhaust to the wastegate isnt fabricated in a efficient manner boost control WILL be a problem.
Old 06-06-2012, 07:26 AM
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Richard, looks good how bout some detailed pics?
Old 06-06-2012, 07:44 AM
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Quote:
Originally Posted by motley911 View Post
I can speak from experience - YES.....
...
I was aiming for HP as well as "looks" therefore I was determined to do a TT build. However if I had to do it all over again I would likely call Chris at Turbokraft and order a complete, large single turbo engine that incorporates proven / tested components.
Richard
Thanks, Richard!
We also build complete Twin Turbo systems, from individual components, to complete shipper systems for final installation & tuning by the client. 2 examples:




Quote:
Originally Posted by Raceboy View Post
If it is custom anyway, then there is only minor difference. Of course, I am talking from the DIY-er perspective, obviously having it all made will cost some significant money but that applies to single turbo also.
Not really, because doing a single turbo allows you to use some off-the-shelf components with little or no modifications, ex: headers & muffler. Even easier when the 1995 993 engine is going in an earlier chassis and getting programmable engine management.

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Old 06-06-2012, 09:06 AM
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I prefer two, all depends on how much power. i experimented with lots of header designs. it funny seen long tube headers on turbo. i guess you can charg more money for the looks but doesn't work, believe me. the SHORTER THE BETTER... street,drag,and road racing.
Old 06-06-2012, 04:45 PM
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Shorter primaries = quicker spool
Old 06-06-2012, 06:50 PM
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Eddie do you have any performance data you would share comparing longer tube vs short tube twin turbo set up?

Kudos on the Texas mile run. Simply awesome to see!
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Old 06-07-2012, 04:04 PM
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Had an exahust manifold made for my single turbo RX-7 back in 2000... G&S racing out of Florida made it based on their NHRA drag car which had very long runners compared to the kit manifolds available in the day.

Carlos gave me some insight on how he determined length via trial-and-error... something to do with being able to see a change in the metal color and that telling him when the fuel had expended most of it's energy. He'd cut the pipe there and weld up the rest of the exhaust.

When I dynoed my car, I did have a higher peak horsepower with the new manifold, but noticeably slower spool time. This was the old Dynamic Turbo RX-7 from Miami in the late 90's.


Quote:
Originally Posted by EBELLO RACING View Post
I prefer two, all depends on how much power. i experimented with lots of header designs. it funny seen long tube headers on turbo. i guess you can charg more money for the looks but doesn't work, believe me. the SHORTER THE BETTER... street,drag,and road racing.
Old 06-08-2012, 06:26 AM
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You need exhaust energy / velocity to spool up the turbocharger. Shorter primaries will give quickest spool. That's why Porsche only twin turbocharge since the 993TT, and use very short headers to maximise responsiveness and low down torque. Long gone are the days of using long headers for street turbo's.

Last edited by 911TT33; 06-08-2012 at 06:50 AM..
Old 06-08-2012, 06:40 AM
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Carlos gave me some insight on how he determined length via trial-and-error... something to do with being able to see a change in the metal color and that telling him when the fuel had expended most of it's energy. He'd cut the pipe there and weld up the rest of the exhaust.

When I dynoed my car, I did have a higher peak horsepower with the new manifold, but noticeably slower spool time. This was the old Dynamic Turbo RX-7 from Miami in the late 90's.

It is no black magic, it is common knowledge of 4stroke engine and turbochargers.

Since spinning the turbine is all about energy, the less energy you waste before it reaches turbine, the best spool and power you get as it is not the speed of the gases that turns the turbine, it is the heat energy of the exhaust. The faster you get the gas onto turbine blades, the less energy is wasted by cooling (=heating the exhaust manifold). This is the reason for opting for smaller headers.
The reason behind the most power with long headers was because the turbine was single inlet type and the primaries were just separated longer thus not letting the pulses to work against each other. Twin turbo (one bank of cylinders feeding each turbo) or twin-scroll turbine housing do the same with very short headers.
And when searching for the point where most energy is expanded (though I cannot see any reason why one needs to find it) can be found easier: using EGT sensor and moving it in the exhaust.
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Old 06-08-2012, 08:58 AM
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I must respectfully disagree.
Header design is specific to application. Heat and velocity run a turbo, meaning the pipe size is critical. Short tube headers work and are easy to make and package well which is why they are the standard. Also EFI narrows the advantages of a tuned system as opposed to "dump it quick as you can get it there" system. Street turbos spend little time on boost which is where a properly sized tuned system helps out. There is also a bump in HP at the top end as the organized pulses hit the turbine in order. Even without all that the sound is worth the effort. Exotic, no more motor boat.
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Old 06-08-2012, 10:18 AM
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Eddie do you have any performance data you would share comparing longer tube vs short tube twin turbo set up?

Kudos on the Texas mile run. Simply awesome to see!
Just look at the 935 K3's...short log headers and the quickest paths to the turbos.
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Old 06-08-2012, 10:43 AM
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The back of your car is just Sick.How much hp, engine size? Please, more pics.

Old 06-08-2012, 10:52 AM
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