David Buschur should build a turbo like this
David Buschur should build a turbo like this
The turbocharger has undergone a continuous evolution in the hands of Porsche engineers. Variations in turbine size, the addition of the intercooler, the move to twin turbochargers and advances in engine-management systems have all wrung greater performance from the basic concept of an exhaust-driven compressor. In the new 911 Turbo, Variable Turbine Geometry (VTG) provides a revolutionary step forward.
It’s well understood that a smaller turbine will generally reach optimum speed more quickly than a larger, heavier turbine. But as engine revolutions continue to climb, exhaust flow tends to overwhelm the smaller turbine; the resulting backpressure robs the engine of power at high rpm. Larger turbo units have the opposite tendencies. They work well at mid- to high-range engine speeds, but it takes them longer to spin up to speed, resulting in “turbo lag.”
The 911 Turbo offers a revolutionary solution to this dilemma. Its win inter-cooled turbochargers feature the application of Variable Turbine Geometry (VTG). With Variable Turbine Geometry, the exhaust flow is channeled into the turbines by way of electronically adjustable guide vanes. By changing the angle of these vanes, the system can replicate the advantages of a small turbo at low rpm, and a larger turbo as the tachometer climbs.
While this technology has been used in diesel engines since 1996, Porsche uses Variable Turbine Geometry for the first time in the new Turbo. The system is capable of handling the significantly hotter exhaust from a gasoline engine by using heat-resistant materials first developed for aerospace.
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Joined: Aug 2006
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From: Chi-Town, IL
Porsche's Technology is just amazing i just finished watchin the Tech vid...i bet they spent a pretty penny on that. I would buy one just to strip it and track race it...jp lol just buy and track!
this technology has been around for years. Porsche didn't invent it. search for VNT turbo.
http://en.wikipedia.org/wiki/Variabl...y_turbocharger
http://en.wikipedia.org/wiki/Variabl...y_turbocharger
Last edited by honda-guy; Dec 13, 2006 at 03:23 AM.
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Yeah twin scroll doesn't hold a candle to variable vane. What most people dont realize is a if our 4g63 has a powerband with torque exceeding 400ft lbs it only holds 400ft/lbs for 500-1000rpm or so. This porsche has 400+ from 1900-5000rpm. Thats 3100rpm band of juice. Porsche and Honda are the first to offer variable vane on a production car. Look at hondas turbo. Much more reliable approach to variable geometry and easy to copy and reproduce for any turbo.
here's a picture of the honda variable flow turbo. the honda design seems to be more reliable (less moving parts) but probably not as efficent as the other design. it looks similar to an internal wastegate
Last edited by honda-guy; Dec 13, 2006 at 06:31 AM.
Actually I think the opposite is true. take a look at dynographs of 6 cylinders vs 4g63 . 6 cylinder graphs from nissan, toyota, bmw, and others will have a very short peaky dynocurve. Much shorter than a typical 4g63 curve. I think cylinder count has nothing to do with it. Its has more to do with the bore/stroke/ and cylinder head flow.
VNT turbos have been used for a number of years already on diesel passenger cars in Europe.
The Honda design has the benefits of being simplier and cheaper, but it doesn't have the same ability as a VNT using infinitely variable vanes. It's like VTEC with 2 steps vs. something like Double Vanos which is infinitely variable.
The new thing on the diesels in europe is called a sequential parallel twin turbo setup.
Uses a small turbo at low rpms (but I think it blows through the big turbo to help spin it up), both turbos at mid-range, and the big turbo at high rpms. One or both of the turbos uses VNT, can't remember.
The Honda design has the benefits of being simplier and cheaper, but it doesn't have the same ability as a VNT using infinitely variable vanes. It's like VTEC with 2 steps vs. something like Double Vanos which is infinitely variable.
The new thing on the diesels in europe is called a sequential parallel twin turbo setup.
Uses a small turbo at low rpms (but I think it blows through the big turbo to help spin it up), both turbos at mid-range, and the big turbo at high rpms. One or both of the turbos uses VNT, can't remember.
Actually I think the opposite is true. take a look at dynographs of 6 cylinders vs 4g63 . 6 cylinder graphs from nissan, toyota, bmw, and others will have a very short peaky dynocurve. Much shorter than a typical 4g63 curve. I think cylinder count has nothing to do with it. Its has more to do with the bore/stroke/ and cylinder head flow.
6 cylinder turbo will have a broader torque curve over 4 cylinder turbo at the same hp level. you can use a smaller turbo on the 6-cyl which will have less lag. you were comparing 400 ft/lb of a 4-cyl turbo vs. 6-cyl turbo. of coarse the 6-cyl turbo is going to have a broader torque curve. unless you're talking about huge single turbo 900+ hp 6-cyl turbo.
