Twin-scrool vs. Open scroll test!
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Joined: Sep 2005
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From: Chicagoland
I would have to agree with te B in his arguments and questioning...seems 9sec240 is only ever focuses on flat foot, already spooled, drag racing type powerbands; which is not what a TS is designed to benefit. It is designed to benefit turbo response in time (not RPM) as pointed out by Ted B and 9sec 240 in the diesel comparison.
A TS is a great design for people auto-xing and tracking (road course) their cars...it is what I look for as I've been spoiled tracking/auto-xing Formula SAE cars.
I really would like to see a more scientific test done...make it more like a lab report... show various graph's: both power in relation to time and rpm...also pressure in relation to time and rpm. These would show that a TS either does or doesn't truly benefit over a smaller a/r SS turbo and would show what is the better product.
Of course then there are variables that can't be identical such a exhaust manifold, but that is part of the trade off of TS vs SS and what you can get.
A TS is a great design for people auto-xing and tracking (road course) their cars...it is what I look for as I've been spoiled tracking/auto-xing Formula SAE cars.
I really would like to see a more scientific test done...make it more like a lab report... show various graph's: both power in relation to time and rpm...also pressure in relation to time and rpm. These would show that a TS either does or doesn't truly benefit over a smaller a/r SS turbo and would show what is the better product.
Of course then there are variables that can't be identical such a exhaust manifold, but that is part of the trade off of TS vs SS and what you can get.
HOW MUCH TIME DO YOU SPEND ACCELERATING WHILE THE TURBO IS SPOOLING VERSUS ACCELERATING ONCE THE TURBO IS SPOOLED???????????????? Keep in mind we are talking about ACCELERATING and not putzing through traffic.
If the benefit of the TS is better spool and you are spooling 10% of the time and at full boost 90% of the time, doesnt it make WAY MORE SENSE to improve the power once on boost versus trying to get the turbo to spool quicker????????????
This doesnt just benefit the drag racer, it benefits the road racer and the every day street warriors. There are SOOOOOOOoooo few instances where I could possibly see any need to be at 3000 rpms at WOT trying to accelerate hard.
If somebody here really needs to be able to accelerate hard at 3000 rpms, then they need to sell their low displacement turbo car and buy a Viper.
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Joined: Sep 2005
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From: Chicagoland
Is it really?
Don't both applications aim to spool a relatively large turbo using a relatively small air mass, with relatively long intervals between exhaust pulses? Whether it's a high displacement, low rpm engine trying to spool a turbo, or a small displacement, high rpm engine trying to spool a large turbo, the principle is the same.
The real question is (as far as I am concerned) not if it works (it definitely does), but as the turbine housing A/R increases, if the benefit of the TS design persist beyond the point where the TS housing equals the power of the open housing. FWIW, I've seen more testing to this point indicates that it does than not.
Don't both applications aim to spool a relatively large turbo using a relatively small air mass, with relatively long intervals between exhaust pulses? Whether it's a high displacement, low rpm engine trying to spool a turbo, or a small displacement, high rpm engine trying to spool a large turbo, the principle is the same.
The real question is (as far as I am concerned) not if it works (it definitely does), but as the turbine housing A/R increases, if the benefit of the TS design persist beyond the point where the TS housing equals the power of the open housing. FWIW, I've seen more testing to this point indicates that it does than not.
If you are shooting for better spool up, then yes, there are similarities. But the APPLICATION is NOT the same. We are NOT trying to tow anything or haul heavy loads. We are trying to ACCELERATE as quick as possible. This requires high RPM TQ where spool is not a factor.
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From: Chicagoland
Former Sponsor
Joined: Sep 2005
Posts: 984
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From: Chicagoland
And you know this how? Anything done on the exhaust side to increase spool will hamper HP up top regardless of turbo size.
Would changing from a TS to OS setup, would the car need to be re-tuned even if the same turbo with the same exact A/R were used?
Last edited by LilRico; Aug 29, 2007 at 07:03 PM.
I know you did not ask me specifically, but I figured I would chime in.
In my opinion, you would need to build two equal length manifolds that were identical to each other with the exception of the collector. One would be a 4 into 1 collector for the open scroll and the other would be a 4 into 2 for the divided scroll.
The reason for the same design manifolds would be to insure that the header is not attributed to any power gains. Obviously a well designed TS header will preform better than a crappy open scroll header.
The reason for the equal length would be to insure that the open scroll would benefit from separate exhaust pulses like the TS artificially creates.
You would use ONE turbo and change only the turbine housings.
You would need to test ALL the turbine housing AR ratios available for both open and divided.
Each test should be done at two boost levels. One level representing average street boost and one level representing "race" boost levels.
Obviously, the same car would need to be used for all testing with nothing but the header and turbine housing being changed.
Testing on the same day with weather conditions being the same all day would be preferred.
Obviously this would be a huge undertaking with a massive investment in money and time. I would PERSONALLY help in any way I can.
In my opinion, you would need to build two equal length manifolds that were identical to each other with the exception of the collector. One would be a 4 into 1 collector for the open scroll and the other would be a 4 into 2 for the divided scroll.
The reason for the same design manifolds would be to insure that the header is not attributed to any power gains. Obviously a well designed TS header will preform better than a crappy open scroll header.
The reason for the equal length would be to insure that the open scroll would benefit from separate exhaust pulses like the TS artificially creates.
You would use ONE turbo and change only the turbine housings.
You would need to test ALL the turbine housing AR ratios available for both open and divided.
Each test should be done at two boost levels. One level representing average street boost and one level representing "race" boost levels.
Obviously, the same car would need to be used for all testing with nothing but the header and turbine housing being changed.
Testing on the same day with weather conditions being the same all day would be preferred.
Obviously this would be a huge undertaking with a massive investment in money and time. I would PERSONALLY help in any way I can.
I know you did not ask me specifically, but I figured I would chime in.
In my opinion, you would need to build two equal length manifolds that were identical to each other with the exception of the collector. One would be a 4 into 1 collector for the open scroll and the other would be a 4 into 2 for the divided scroll.
The reason for the same design manifolds would be to insure that the header is not attributed to any power gains. Obviously a well designed TS header will preform better than a crappy open scroll header.
The reason for the equal length would be to insure that the open scroll would benefit from separate exhaust pulses like the TS artificially creates.
You would use ONE turbo and change only the turbine housings.
You would need to test ALL the turbine housing AR ratios available for both open and divided.
Each test should be done at two boost levels. One level representing average street boost and one level representing "race" boost levels.
Obviously, the same car would need to be used for all testing with nothing but the header and turbine housing being changed.
Testing on the same day with weather conditions being the same all day would be preferred.
Obviously this would be a huge undertaking with a massive investment in money and time. I would PERSONALLY help in any way I can.
In my opinion, you would need to build two equal length manifolds that were identical to each other with the exception of the collector. One would be a 4 into 1 collector for the open scroll and the other would be a 4 into 2 for the divided scroll.
The reason for the same design manifolds would be to insure that the header is not attributed to any power gains. Obviously a well designed TS header will preform better than a crappy open scroll header.
The reason for the equal length would be to insure that the open scroll would benefit from separate exhaust pulses like the TS artificially creates.
You would use ONE turbo and change only the turbine housings.
You would need to test ALL the turbine housing AR ratios available for both open and divided.
Each test should be done at two boost levels. One level representing average street boost and one level representing "race" boost levels.
Obviously, the same car would need to be used for all testing with nothing but the header and turbine housing being changed.
Testing on the same day with weather conditions being the same all day would be preferred.
Obviously this would be a huge undertaking with a massive investment in money and time. I would PERSONALLY help in any way I can.
I'll follow this procedure exactly as posted. After every scenario has been exhausted, we will post the results.
Evolving Member
Joined: Dec 2006
Posts: 391
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From: Palatine, IL
I love these kind of threads
, just be reading just a few post by Ivan i learned some much about TS and OS thanks Ivan
Former Sponsor
Joined: Sep 2005
Posts: 984
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From: Chicagoland
Yes, tuning would have to be done. I would shoot for the same AF and timing for each boost level. Reporting on what tuning was needed for each combo would also show where the gains and losses are.
