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I hear about them, but I have never seen one applied, why is that? From what I have heard of them they are pretty trick. Can one of our turbo gurus enlighten me? Boost is in my future and I want to know what the turbo world has for me.
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Patrick Scott
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Last edited by PatScottAKA99XE : Jun 11th, 2002 at 09:10 PM.
Variable Area Turbine Nozzle... i think they're still trying to perfect it but in it's final stage it will take over boost control from the wastegate. I think you still need the wastegate though... don't know about the details. The lag is suppose to be very low though.
Originally posted by PatScottAKA99XE I hear about them, but I have never seen one applied, why is that? From what I have heard of them they are pretty trick. Can one of our turbo gurus enlighten me? Boost is in my future and I want to know what the turbo world has for me.
Originally posted by James Variable Area Turbine Nozzle... i think they're still trying to perfect it but in it's final stage it will take over boost control from the wastegate. I think you still need the wastegate though... don't know about the details. The lag is suppose to be very low though.
I was just doing a bit of reading on the internet, you'll have to forgive me the book I was reading about the VATN was old so I didn't know there's already ppl using them. There's a lot of info on the web about it. Don't know what Mike's experience is but here's a link of a guy who used it on his Miata.
Just did some more reading. Apparently, the reason why the aerocharger has had such a bad rap is because when the turbocharger first came into production the material they used for the housing was not the right formulation of metal which caused it to expand and take away valuable clearance in the turbine causing it to sieze. While this has been solved, they (ie ppls opinion and experience) have found that the VATN is still less reliable than the run of the mill turbo.
Originally posted by James Just did some more reading. Apparently, the reason why the aerocharger has had such a bad rap is because when the turbocharger first came into production the material they used for the housing was not the right formulation of metal which caused it to expand and take away valuable clearance in the turbine causing it to sieze. While this has been solved, they (ie ppls opinion and experience) have found that the VATN is still less reliable than the run of the mill turbo.
They are laggy, make no power and blow up when you try to turn up the boost, the suck ass no matter what you read in magazines and books.
Yeah I heard about some failures as well(old stuff though) wasnt sure if they had been improved. Nice concept..too bad it doesnt work as well as it was intended to. For what its worth I heard no waste-gate was needed.(again old stuff).
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Patrick Scott
Yeah, thats a roll cage in there.
I shall call him...Mini-Me
They are laggy, make no power and blow up when you try to turn up the boost, the suck ass no matter what you read in magazines and books.
VNT's kick ass when done right! They have better low-end response and less high-end backpressure than even the best ball bearing wastegated turbos. Garrett produces over 3000 VNT's per DAY (yes, per DAY) in Europe, and reliability isn't a major problem. On passenger car diesels.
Unfortunately, nobody has really ever been able to make one work on a gasoline engine. EGT's are too high, or so the thinking goes.
The Aerocharger VNT's seem to have bearing problems more than anything else. The non-pressurized wick-fed bearing system doesn't have the stability to cut it.
VNT's are the wave of the future. They have literally transformed European passenger car diesel engines from foul smoking turb mobiles into clean-running fun-to-drive rocket ships. It is only a matter of time before they get applied to gasoline engines.
However, that will require some serious OEM-level R&D budgets. Not the kind of thing you want to take on by yourself.
REALLY? I keep reading about it and Corky Bell talks about it like it's THE turbo to get. What are your thoughts on making it work for Gasoline engines? What if the housing of the turbine is tapped and instead of the self contained lubrication system you put in a self contained oiling system, maybe run a different oil then what's in the motor?
Originally posted by James REALLY? I keep reading about it and Corky Bell talks about it like it's THE turbo to get. What are your thoughts on making it work for Gasoline engines? What if the housing of the turbine is tapped and instead of the self contained lubrication system you put in a self contained oiling system, maybe run a different oil then what's in the motor?
I may be mistaken, but I believe that Bell Engineering (aka Corky Bell) was involved in the Aerocharger development. Not exactly an unbiased opinion!
The non-pressurized ball bearing system doesn't have the rotordynamics for high shaft speeds (meaning high boost, meaning lots of power). I don't think that you can just swap in some other bearing.....rotating machinery rotordynamics is a very complex subject and you have to have some good analytical and experimental capability to do it right. Garrett has a pretty strict shaft motion qualification test... No turbo makes production until shaft motion is proven out. Even then, it can bite you.
The way that aerodyno mount their turbine and compressor wheels nearly back-to-back effectively rules out the ability to adapt a competing turbo company's bearing design to the aerocharger.
The bearings are only a part of the story. The big concern is how do you keep the vane mechanism from scaling, sticking, and failing at the elevated EGT levels typical of gasoline engines.
Is there another company out there that has taken this info and is currently trying to improve it? To me it seems like the VNT can work but needs perfecting. Well, thanks for the info Rob.
I have been very interested in these for quite some time now. When I eventually go turbo I will be aiming for as little exhaust manifold pressure as possible. That being difficult without crazy turbines that dont do me much good at low RPMs.
They are definitly more expensive, but the wastegate-less setup would make up for a portion of that. Not sure how boost control would work out.
Mike, could you expand on your comment you made? When where why kinda thing.
Has anyone since the start of this thread gained any additional knowledge towards this topic?
sounds iffy, though... why not try compund-charging? Turbo-tech has a very interesting article on it... using a supercharger to eliminate turbo-lag... but the added complexity of programming takes some of the flexibility away... maybe mike could fill us in...
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