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Discussion Starter · #1 ·
I have a somewhat awkward question. As we all know the the Supras had the option of a turboed model. Of which was a sequential setup. Has anyone every created another type of Sequential setup. Here is my first idea. Two turbos (obviously) one small one large, two exhuast manifolds, two wastegates, and the two turbos. Plumb the "cold side" of the small turbo to the cold side input of the big turbo. The second exhuast manifold just feeds the big turbo, the bypassed gas from the first turbo would be fed into the a pipe that would koin exhuast gases from the other manifold prior to the second wastegate and also help spool the big turbo . Obviously after all pressurizing the air would be intercooled. What is your take on this idea. Inefficient?

Second idea, use one exhuast manifold two wastegates and two turbos. Set the wastegate on the small turbo to become open at a designated pressure. Allow the small turbo generate about 10-15psi. The dumped gas is then sent off to turbo number 2. Getting this done could be done via reentering the exhuast manifold or by plumbing a tube that is outside of the manifold but joins the gas flow prior to the second wastegate to feed the second turbo. Also mind you that the small turbo would always be spinning and pressurizing the big turbo. When the small turbo is being spooled the pressurized air would be routed to the inlet of the second turbo. Then the final air volume pressurized by the big turbo is intercooled.
Your take on this idea?

Third idea. By far the most complex. One manifold two wastegates two turbos and a two way valve on the small turbos "cold side outlet". The idea should allow for the least amount of lag an great power thorughout the powerband. Make the small turbo generate about 10-15psi. The valve on the outlet of small turbo would allow air to go directly to the intercooler up till the maximum set boost for that turbo 10-15psi. Then the valve would redirect the air to the big turbo for the remainder of the powerband in order to help spool the big turbo. The valve is used to not lose boost at low rpm due to resistance by the big turbo. Note that once the 10-15psi is met by the small turbo, not only would the output boost pressure spool the big turbo but the gases redirected by the wastegate would also help spool the big turbo. Not sure if the big turbo would need a fresh air supply on the inlet of the cold side when air is not being bypassed to it from the small turbo. If needed two pipes could be spliced onto the big turbo; one that would come from the small turbo the other being a fresh air supply.

with the thrid setup the lower rpm and low midrange woud look like Small turbo feeding 80-90% of boost and minimal boost coming from the big turbo
The high midrange and high rpm would look like 80-90% boost coming from big turbo being "prespooled" consistently with 10-15psi of air pressure and bypassed exhaust gases from the small turbo. The most obvious problem with this setup would be plumbing.

I need some opinions. Goals are this, a linear powerband, not a huge power jump at high rpm. Good low end power and high low end torque and a peak horsepower over 900hp (aiming for for 9sec et's in the 1/4mile) . Essentially I'm researching to find a minimal lag system that can generate a lot of power and offer good power at all rpm. The engine is the infamous
2JZ-GTE engine. What is your take on these ideas?

Feel free to criticise, as it can only enrich my knowledge of these complex systems. I see it this way. One big turbo, lots of lag huge power jump at high rpm, no good. Two small turbos working in parallel, consistent power low lag, lack high horspower potential. Sequential setup, could be the holy grail for little lag, power everywhere, and high horsepower capabilities.
 

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T88 YOU
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3,567 Posts
the only real way to do this with a long term goal in mind is close to the 3rd setup you mentioned with some sort of exhaust control valve. the problem i see with first two setups is mostly in the wastegate routing. you cant route the wastegate of the smaller turbo into the turbine of the larger turbo, there is backpressure in the larger turbo which defeats the purpose of the wastegate which is to relieve the pressure buildup to lessen the exhaust gas pushing the turbine. the first idea is completely out of the question, when you say 2 exhaust manifolds, i assume you mean like 3 and 3 cylinders, or 2 and 4... you will see that this will put quite and imbalance on the cylinders and will screw everything up, especially when it comes to tuning it... can you say INDIVIDUAL CYLINDER TUNING!!! that could also throw off the balance in the crankshaft and cause harmonic problems. there is a reason toyota/yamaha designed the stock sequential system with an exhaust gas control valve, its just about the only way to make a proper sequential system. the only other option for the goal you are going for is something like the turbos that come on the new 997 turbo with variable vane technology, OR just stick with a smaller turbo...
 
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Discussion Starter · #4 ·
MtFujiSupra said:
You're not really a newbie and this isn't your first post is it...
No I am not a newbie, well maybe to complex turbo setups, but not simple ones. This is my first post on this forum. It just seemed appropriate to post this question on a supra forum and not on a Z car forum. i'm trying to do some research for my co-worker. He's building a 2JZ engine that will be in a Lexus SC300.

I am far more familiar with Nissan Engines and Z car stuff.

I am going to search around in your forums some more because I am startinng to find others that are on the road as me. I just need to keep digging, getting close to an actual setup that can be executed. I'm gonna do some more research and then if no answers present themselves I'll be sure to revisit this thread.
 

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Registered
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1,655 Posts
I understand trying a new set up that nobody has is cool but the cost's and headache's sometime's aren't worth it unless you own a shop. That being said, if you live here in vegas I would get a hold of dana since he's done SC300's and go a single.
 

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Alpine Hardtopper
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1,096 Posts
In general there are very few cases where running two sizes of turbo are desirable. Some of the large diesel engines are running two in series just to get pressure high enough (~75 psi of boost in some cases).

But in a car like the Supra or SC300, it just doesn't pay off. I've gotten several designs to work on paper, and even doing thermodynamic calculations...there is a benefit to it. But by the time you get the wastegates and one-way valves in there....and make room for two turbos and the valves/plumbing you really don't have much practical improvement. And you have a system that requires a lot of control to operate correctly. In an effort to make two different sized turbos work together, the exhaust backpressure usually takes a hit that's *not* insignificant.

Think of it this way....the stock sequential twins on the Supra are about as simple as it gets, and even *they* have problems. The boost is highly non-linear in sequential mode. And when one actuator starts malfunctioning, the whole system doesn't work correctly.

All that being said, in some of my odd twin designs, there's ALWAYS been a cheaper way to get faster spool or lower boost threshold using a single turbo. More recently, the variable vane turbos are just awesome.

It's cool that you're thinking outside the box. Lots of great ideas come from just that. Some will be good, and most won't. <grin>
 

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feeding your habit
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this has all been gone over ad noseum (sp?).... use the search feature. Twins aren't going to do as well as a nicely sized single. The twins of old were not as efficient as todays single. I have great respect for the stock twins..... but....
 

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Alpine Hardtopper
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1,096 Posts
Link worked fine for me. If you do a search for "Sequential Turbochargers" you'll find it as the first result (thread title). Last post was 6-6-06 and it's in the "General Chat Forums" > "General Supra Forums" location
 
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