Poor man's Variable turbo?
Thread Starter
Teching In
Joined: Nov 2014
Posts: 10
Likes: 2
From: Montreal, QC
Poor man's Variable turbo? Hi there.
Disclaimer: If you don't like newbies ranting about technology they don't know much about, please, stop here.
So I was reading some fine article about koenigsegg's variable geometry turbo.
Very simple, one single moving part, very clever.
You can see M. K himself talking about it there :
So, from what I've understood, the deal is about not having too little exhaust gas rushing into a too big housing, loosing velocity and thus unable to push on the turbo vanes.
So here I am thinking : twin-scroll turbo are pretty similar.
Why not using such turbo with a valve:
At low rpm you let the exhaust only goes into on scroll.
As you go higher you open up the second scroll.
From the drawing it look like Koenigsseg's has a fancy shape to optimize the aerodynamic, would it work without those?
I couldn't think about a better place to get experts' opinion.
What you guys think?
Disclaimer: If you don't like newbies ranting about technology they don't know much about, please, stop here.
So I was reading some fine article about koenigsegg's variable geometry turbo.
Very simple, one single moving part, very clever.
You can see M. K himself talking about it there :
So, from what I've understood, the deal is about not having too little exhaust gas rushing into a too big housing, loosing velocity and thus unable to push on the turbo vanes.
So here I am thinking : twin-scroll turbo are pretty similar.
Why not using such turbo with a valve:
At low rpm you let the exhaust only goes into on scroll.
As you go higher you open up the second scroll.
From the drawing it look like Koenigsseg's has a fancy shape to optimize the aerodynamic, would it work without those?
I couldn't think about a better place to get experts' opinion.
What you guys think?
TECH Fanatic
Joined: Jun 2013
Posts: 1,163
Likes: 16
From: Avon, Ohio
I've done a simple set up with wastegates.
Think of a large twin scroll turbine. Now, block one side. Then, take your wastegate dump and dump it AFTER that block on the one side. Do it right with fluidynaimics in mind shockingly well. The only disadvantage is controlling your variable vain is not as easy as a true VV turbo. It works best if you "set it and forget it" unless you have a big dollar boost controller.
Gate one @15psi dumps back into the turbine.
Gate 2 (your boost control) dumps to atmosphere. So, at 10 psi you are on one scroll all the time. At 20 psi, you will have much quicker spool, and big top end benefit with both scrolls working.
Just an idea.
This unit from SP works under a similar premise, but is much more expensive. It is a bolt on piece however...
http://www.spracingonline.com/projec.../3643%E2%80%9D
Think of a large twin scroll turbine. Now, block one side. Then, take your wastegate dump and dump it AFTER that block on the one side. Do it right with fluidynaimics in mind shockingly well. The only disadvantage is controlling your variable vain is not as easy as a true VV turbo. It works best if you "set it and forget it" unless you have a big dollar boost controller.
Gate one @15psi dumps back into the turbine.
Gate 2 (your boost control) dumps to atmosphere. So, at 10 psi you are on one scroll all the time. At 20 psi, you will have much quicker spool, and big top end benefit with both scrolls working.
Just an idea.
This unit from SP works under a similar premise, but is much more expensive. It is a bolt on piece however...
http://www.spracingonline.com/projec.../3643%E2%80%9D
Restricted User
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
Someone had a picture of a very clever idea using an external wastegate to control flow to one side of the turbine. I wish I could remember who posted it. There were a few different ideas that came about after that picture was posted.
Thread Starter
Teching In
Joined: Nov 2014
Posts: 10
Likes: 2
From: Montreal, QC
This is clever, and much more serviceable since the valve is a standard piece.
I come to realize that Koenigsseg's VTG is a lot of hype for what is a improvement of a existing idea.
Now, there is one test that would be cool to make : compare a front mounted turbo setup to a rear turbo setup with quick spool. Would the quick spool compensate the lag?
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Restricted User
Joined: Mar 2014
Posts: 7,192
Likes: 109
From: Ohio
I believe the idea I had seen was with a divided T4 turbo.
The exhaust merged 8-1 going into just one side of the turbine. The merge was just small enough to fit one opening in the turbine so it would obviously choke up top, but spool extremely quick. Then there was a large 60+mm external wastegate plumbed into the merge about 8" before the turbo (before it had necked down to a size small enough to fit half the turbine) that dumped into the other side of the divided T4 inlet.
All 8 cylinders would pump into one side of the inlet low in the rev range for maxiumum velocity, and when boost would climb, the wastegate would open and allow for full flow into the turbo so it wouldn't choke the top end.
I've seen half a dozen variations of this setup in the last couple of years. One was a fully divided T6 setup, no merge. Large external gates were plumbed inline before the turbo so that all gasses had to pass through them, there was no bypass. They were actually used as the 90* bend into the turbo. They were ran without the fire rings, no boost controller, and soft springs. They would let just enough exhaust past them as boost was building to maximize velocity into the turbine. As exhaust backpressure climbed the gates would slowly open so that flow was unrestricted. Unfortunately, I never seen the results of this.
Denpo, Zombies did a test a few years ago with spool valves and rear mounts on this forum.
The exhaust merged 8-1 going into just one side of the turbine. The merge was just small enough to fit one opening in the turbine so it would obviously choke up top, but spool extremely quick. Then there was a large 60+mm external wastegate plumbed into the merge about 8" before the turbo (before it had necked down to a size small enough to fit half the turbine) that dumped into the other side of the divided T4 inlet.
All 8 cylinders would pump into one side of the inlet low in the rev range for maxiumum velocity, and when boost would climb, the wastegate would open and allow for full flow into the turbo so it wouldn't choke the top end.
I've seen half a dozen variations of this setup in the last couple of years. One was a fully divided T6 setup, no merge. Large external gates were plumbed inline before the turbo so that all gasses had to pass through them, there was no bypass. They were actually used as the 90* bend into the turbo. They were ran without the fire rings, no boost controller, and soft springs. They would let just enough exhaust past them as boost was building to maximize velocity into the turbine. As exhaust backpressure climbed the gates would slowly open so that flow was unrestricted. Unfortunately, I never seen the results of this.
Denpo, Zombies did a test a few years ago with spool valves and rear mounts on this forum.
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