Twin turbo a 4cylinder engine (1big and 1 small turbine)

mag9556

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Hi all,

Nothing to do try to do some research online but seem a bit blur here.
Let say if we have K3VETT with 1 ori IHI RHF4 turbine for pickup and another with bigger size for end power, what will be the advantage and disadvantages ya..
or we change to one IHI RHF3 and another one bigger..

Thinking of this since if small turbine no end power and big turbine will lag..

Any know please share ya:rock:
 

vr2turbo

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How will you install so that small will feed low and big will feed high? I know the SC and TC combi system does the same thing. SC boost low and TC boost high but many say difficult to do....
 

ixeo

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No such thing as a K3VETT...

You answered yourself... big turbo will lag, small turbo run out of breath. What’s your objective anyway?
 

mag9556

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Wah.. so fast found the answer d... lol:adore:
Where got finish.. what is the advantage and disadvantage d...:hello:

No such thing as a K3VETT...

You answered yourself... big turbo will lag, small turbo run out of breath. What’s your objective anyway?
K3VETT... planing to do R&D more to come out with one d..:laugh:
finding something different to discuss d...
trying to pull the engine juicy higher without lag

:marchmellow:
 

Izso

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nice wira .. but i wonder how he runs it? Daily driven or race only spec? Cuz this K3VETT fella sounds like a daily
 

mag9556

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Nightstalker1993

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Well, for one, it's called compound charging, not twin turbo and the plumbing is really complicated. I highly doubt you would want to go down that route as I don't think you have the engine bay space to accommodate it.

Advantages is that you get the power low down from the small turbo and also power up top from the large turbo, but the power up top in theory would be slightly lesser than if you were running a single large turbo only as the air has to pass through the small turbo which causes a slight restriction, but basically you get best of both worlds. Disadvantages is plumbing nightmare, need to buy 2 wastegates and possibly tuning nightmare as well.

Here's an image I borrowed off Google



So basically plumbing wise, exhaust manifold goes to small turbo, the output of that goes to the large turbo, the wastegate of the small turbo also goes to the large turbo, then the large turbo exhaust goes out as normal. For the cold side, the air goes through the large turbo first, then into the small turbo, then to the intercooler then engine.

At lower RPM, the exhaust gas is enough to spool the smaller turbo to reasonable speed, the compressor will then draw air THROUGH the large turbo and compress it, then once the exhaust gas is enough to spool the large turbo, the large turbo will push more air than the small turbo, and is basically forcing air into and through the small turbo. Basically you should be able to hear your turbo spool up twice, once at low rpm and another time at a higher RPM.

I also considered of doing this, but limited engine bay space and high cost and effort prevents me from doing so. Now I just run a single TD05 twin scroll turbo on my 1.8L engine and it gives me full boost from around 3.5-4k rpm all the way to my 8400rpm redline.
 

vr2turbo

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Isn't the current twin scroll or VGT does the same thing? Technically I am old school only...lol
 

Nightstalker1993

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Isn't the current twin scroll or VGT does the same thing? Technically I am old school only...lol
No, it is far from the same thing. Twin scroll and VGT tries to expand the efficiency range of an existing turbo, but it won't be anywhere near the powerband of a properly setup compound charge system. Imagine 2000rpm-5000rpm full boost handled by the smaller turbo and 4500-8000rpm full boost by the larger turbocharger, in all you get a fat 2000-8000rpm powerband!

Also, VGT is only recently getting into petrol turbocharged cars in the Porsche if not mistaken, before this only Diesels use VGTs as it cannot sustain the high temperatures of a petrol engine. Twin scroll works by dividing the cylinder pulses entering the turbo, improving the spool up time and boost threshold slightly.
 
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vr2turbo

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Twin scroll for daily will be nice, flat torque range. Compound will be good for track full power all the way.....:driver:
 

Nightstalker1993

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Twin scroll for daily will be nice, flat torque range. Compound will be good for track full power all the way.....:driver:
Actually it's the other way round. Compound charge will be damn nice for daily and a twin scroll would be good for racing. Imagine daily driving your car you can floor it at 2000rpm and get full boost going up that flyover and you're lazy to change gear, yet also able to pull all the way to 8000rpm when that idiot high beam you on the road not knowing what's under the hood.

You really only need a single large turbo for racing as your engine rpm will be operating at a very narrow range which would be the effective operating range of your turbo and a twin scroll turbo can expand that powerband slightly to make it even more useful.
 

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