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Discussion Starter #1
Ok this might not be the place to ask this but i am going to try.

lets say with xxx type turbo the engine can make 350whp at lets say 20 psi but the turbo is at its max efficiency. Then what if you put two xxx turbos on at the same 20 psi what could the out come be? is there any typical% of increase? mind you both properly tuned of course.

And before anyone freaks out its not for a honda its for a 2.8 or 3.2 i6 i have not decided what one i am going to build yet. I am looking to build a kit that would be good road racing this is not a drag car. I am sure it is hard to get all three low/mid/high but i am going to try.

I hope you guys understand what i am trying to say here:turned:
 

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You should get one small turbo and a big one, let the small one help the big guy build boost, forgot what that's called. Sorry for not answering your question lol
 

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I don't know to much about how that works and I don't see many people doing it. Btw my engine makes about 220 flywheel in na form. I am looking to make 450ish on low boost so any ideas would be great. And if anyone cares I will put up a build thread once I figure out what I am going to do.
 

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Look at compressor maps. That will help you size a turbo to your engine/needs

How deep is your back pocket? You can get all 3 with a properly sized turbo, IMHO a ball bearing turbo is gonna help you the most
 

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I don't know to much about how that works and I don't see many people doing it. Btw my engine makes about 220 flywheel in na form. I am looking to make 450ish on low boost so any ideas would be great. And if anyone cares I will put up a build thread once I figure out what I am going to do.
Third Gen RX-7's used the sequential turbo setup...

but, i agree with others, picked/setup single turbo would work for your needs...

sloopy.
 

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compound turbo set up.
this answered your original question...

Two GT2560 BB turbos, 3 cylinders for each.
is a good answer to the over all question of how to get boost in all rpm ranges...

However for better clarification, what is the rpm range you are looking for exactly? this would be a huge beneficial factoid that could make or break a suggestion.
 

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Discussion Starter #11
ok compound is not what i am looking for

I just have this feeling if i go single its going to lag if i want around 450whp or be too small and run out of air up top. i would say the range of rpm is going to be 3.5k to 7.5k maybe 8k max this is just a good guess btw.

Ok this mught sound weird but i want it to feel super smooth as if it was a factory turbo car. Not that dead feeling tell 4k then all the power at once.

ok this is old and no i dont own a skyline but this is kinda my Inspiration i guess. Anyone know if they are set up sequential? starts at like 1:30
 

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Yes compound is what you want lol the small turbo pushs boost till the big one spools giving you a way wider power band if done right you could pull boost from 3k to 8k at lease
 

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if you google the twin turbo supra's that came from factory they used 2 different sized turbos and had a contoll system that determines when the motor get boost from which turbo. or you can use a compound turbo where one feed the other

or if you search this is the future of spooling turbos (something like that) you could use something with that sort of technology. which would be totally awesome
 

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Discussion Starter #15
Oh sorry forgot that its a e36 BMW engine but I think I am going to go with the m3 3.2 as the parts are more avaible.
 

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So you want power all threw out the power ban for road course racing, why not just get a centrifugal SC?
 

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So you want power all threw out the power ban for road course racing, why not just get a centrifugal SC?
WHAT?!

if you google the twin turbo supra's that came from factory they used 2 different sized turbos and had a contoll system that determines when the motor get boost from which turbo. or you can use a compound turbo where one feed the other
No, they didnt. The Supra used 2 of the same sized turbo. While in vacuum and low boost the car ran on one turbo, the other being isolated by a throttle on the compressor and a throttle on the turbine. Then, at a particular boost level, the throttles opened allowing the car to run on 2 turbos. This allows for more flow so it doesnt choke as it would on a single small turbo.
You cant have 2 different sized turbos plumbed in parallel because the gas will take the path of least resistance which would be through the larger turbo, then the charged air from the large turbo would backflow through the small turbo (which is no longer being spooled). It would be an absolute clusterfuck.

I just have this feeling if i go single its going to lag if i want around 450whp or be too small and run out of air up top. i would say the range of rpm is going to be 3.5k to 7.5k maybe 8k max this is just a good guess btw.

Ok this mught sound weird but i want it to feel super smooth as if it was a factory turbo car. Not that dead feeling tell 4k then all the power at once.
A properly sized turbo for 450 hp will not spool slow on a 3.2 liter engine. But I understand why you may think that it would.
Factory turbo cars are extremely restricted by exhaust, the catalytic converter and chambered mufflers needed to pass emissions and make them quiet also slow down spool significantly. This means that they have to keep turbos pretty small, which of course limits power.
With the right turbo, good tuning and full 3" exhaust you will have better response and faster spool than a factory turbo BMW.
 

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WHAT?!



No, they didnt. The Supra used 2 of the same sized turbo. While in vacuum and low boost the car ran on one turbo, the other being isolated by a throttle on the compressor and a throttle on the turbine. Then, at a particular boost level, the throttles opened allowing the car to run on 2 turbos. This allows for more flow so it doesnt choke as it would on a single small turbo.
You cant have 2 different sized turbos plumbed in parallel because the gas will take the path of least resistance which would be through the larger turbo, then the charged air from the large turbo would backflow through the small turbo (which is no longer being spooled). It would be an absolute clusterfuck.
Actually, the 2J sequential hits the second turbo at an RPM, not a boost level. First turbo is about 10 psi and spools instantly so you've got 10 psi from 2000 rpm all the way to 3800, then at 3800 like clockwork the second turbo comes online and it's a big kick in the pants. So even with the sequential system you're still waiting for 4 grand before you're really going anywhere. It's nice around the city though, lots of jam from any rpm. I'm still going to go single on mine.

You can hear when the second one hits, it goes completely crazy and then shifts to second and starts boiling the rubber away. :)

 
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