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PureBlood
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Just an Idea i've been tossing in my head, if anyone has any ideas or thoughts, drop a line.
Take a small turbocharger one which spools fast (t25 or smaller) and run the exhaust manifold through it so it spools first and quickly, Now, there are still three open Ports 1 Exits the exhaust Gases One Collects Fresh Air, One sends this "fresh" air into the engine. If one were to pipe the outlet for the exhaust gases and the "Fresh air into the engine" port BOTH into a larger t3/t4 or t4 turbo, would the larger turbo produce more air, twice as quickly?
--Just a thought, i don't have $6k to test this theory but in my mind it works. Anyone care to disprove me so that i can sleep again? Thx.
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JonBoy
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In my opinion, no, it won't produce more air twice as quickly, since that assumes that the exact flowrate of air is coming/going through each pipe. This won't happen, since the inlet and exit are of different sizes on many vehicles, thus having different airflow properties. However, speaking from a fluids point of view, the big turbo SHOULD spool faster and therefore provide more boost faster as well - I just can't say how much faster (ie 2x, 1.5x, etc, etc).
Of course, you're going to need extra "plumbing" for even more cooling, I would imagine, since you now have two turbos spooling up, heating the air, etc, etc... This would require a fair bit more room, not to mention some pretty nifty engineering to make it all fit and work without making your engine bay overly claustrophobic. I think you'd be looking at a lot more than $6K for the job - more like $10K, if not more.
That said, I don't know a TON about engines (yet) so I don't even know if there are other restrictions I haven't though of. I'm doing mech. engineering but haven't really dwelt much on engines (aside from some thermodynamics)....
Jonathan
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notyper
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I believe you're trying to describe compound turbocharging. This has historically been used on large industrial engines, maybe aircraft and large diesel engines too.
If memory serves, compound turbocharging is much as you describe. Intake air is compressed by aone turbo, and then sent to another turbo for further compression. I don't know if the same exhaust gas is reused, since it will lose much of its energy in powering the first turbo.
Compound turbos only tend to be used when you need a lot of boost. A typical single turbo charger simply doesn't want to _efficiently_ provide pressure ratios of more than about 2.5-3:1. that means that if you want to run more than 35-40 psi of boost, you need to think about compound turbocharging. In lower boost situations, such as on any sort of production (and most racing) autos, single, parallel or series turbos are better.
SC
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RDMag44
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While at first glance it would seem that you would be pumping more air, we are stealing energy from the exhaust stream to impart to the intake, so the net work that can be done by this combined gas stream will be no greater than that of the original exhaust stream. Also, having a larger turbo on the exhaust side of our small turbo will greatly reduce the velocity over the exhaust side turbine - it needs a high pressure differential to spin up fast, and the backpressure of the second turbo would greatly increase the spooling time.
Now, are you talking both outlets of turbo 1 going into the exhaust inlet of turbo 2 (and a separate air intake for turbo 2)? If so, that's a no-go. What is needed to spool up the large turbo faster is to increase the pressure (and thus flow velocity) applied to the turbine inlet of the large turbine. Now, by feeding both outputs of the #1 turbine to the same input, we have effectively tied them together, such that the pressure at both port must equalize. So, what happens when we pump output into this system? Before the turbine has a chance to spool, there is exhaust pressure being applied to the outlet of the fresh air side, greater then the air pressure outside. This would try to make turbo #1 spin backwards, but since the same force is being applied from the engine side it would likely just stall and get really hot, creating heavy backpressure and serving as nothing more than a complicated exhaust leak!
I would expect that you might be able to get higher boost, but at slower spool, as Notyper notes already, by running them sequentially (i.e. fresh out 1 -> fresh in 2, and use common exhaust). A more practical approach, which has been used by several including Mazda RX-7 and Toyota Supra, is to use 2 turbochargers, possibly of different sizes, both feeding the intake manifold. This allows the use of a smaller turbo charger that spins up faster for more immediate power, while having a second turbo to still allow for stronger boost at higher RPMs. These setups typically have valves that cut the 2nd turbo off until needed, and some have a separate set of valves to allow the 2nd turbo to spin up without a load as the cut-in RPM is approached.
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mugen_integra
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I don't know for sure about t3/t4 turbo, but on the Supra's. The twin turbo spools faster then the upgrade one or big turbo. But as soon as the bigger turbo spool, there will be more air then a small turbo. That's why other Supra are afraid of big Single turbo then twin turbo. So my point is that the bigger turbo will spool a little bit slower then the small ones but once you get it going, there will definately be more air going into your engine.
I will also recommend you get a better intake manifold cause its another thing to get more air in. Your turbo start spooling when you build enough pressure in your intake manifold, not just because of your RPM.
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Fujiwara_Bunta
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OK...
1 - I didn't get the point of your theory! Do you need a big boost or do you need a better response (less turbo lag?)
2 - Do you have a V6 or a L4?
3 - Are we talking about normal or ceramic turbines?
WHY?
1 - If you need a big boost than your theory is wrong! As posted by RDMag44! For That you should use a Hibrid Turbo.. This is a small turbine on a bigger compressor.....on the other hand if you seek response then goto 2
2 - Do you have a v6.. as you should know from RDMag44's post the RX7 uses this supercharging method and the supra does the same thing BUT.. The double rotor is compared to a 6 cilinder conventional.. like the supra's L6.
Why? 4 cilinders produce a poor air pump if devided by 2!!!! where the 6 cilinders provide a reasonable pump if devided by 2!!! So if you apply 2 turbos on a L4 Vtec none of them could spin correctly.. so you'd need the V6 Vtec from the NSX!
3 - To reduce LAG, ceramic trubines are used.. not only they are better heat resistent, more important they are lighter, therefor producing less inertia, and starting to spin earlyer, reducing LAG!
Solutions:
1 - Use a volumetric compressor inlined with the turbo.
2 - Use a VARIABLE Geometry Turbo. Garret VNT25 for Example.
3 - Buy a state of the art Hybrid Ceramic Turbo...
BY THE WAY RDMag44 - Good post
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