I was just reading up on this the other day since my Jetta TDI uses this technology and I was curious to why no one made an EVO replacement with a Varialble Geometry/Vane Turbo. Apparently, the difference in exhaust temperatures of gas (~1100F) vs diesel (~850F) has made quality heat resistant materials difficult to develop for gassers. Porshe got with Borg Warner, I think, and was able to make one work well. If it makes all the HP & TQ of a turbo with the efficiency and mileage of a N/A, it seems the way to go.

 

Heat is indeed the problem. Even on diesels (I have a Jetta TDI too!) the VNT mechanism tends to coke and seize, on a gasser I would think the differing materials coeff. of expansion would be a problem, as would microcracking of new age materials like ceramic. It could work, but I'd hate to be driving the first car with this technology on a gasser as the longevity would be unproven.

 

the porsche and honda offerings for variable geometry turbos are different.

the porsche offering is a way to move the fins on the inducer. the honda offering is a way to actually change the size of the inducer inlet, basically a trapdoor wastegate.

 

All the VW's have this (98 and up TDI, and all new platform cars) and..... it sucks.
God I HATE german enginnering

 

are YOU serious? you spend your commute in the 2-3k rpm range and on both a gt35r equipt evo and an s2k you'll thank them for their gas mileage.

now that we're NOT talkin' about commutes anymore... it's a fantastic engine because i don't think there are any examples of brilliant naturally aspirated technology that don't directly transfer performance value to turbocharged application.

 

And yes we replace alot of turbo's at work, they **** alot of oil into the intake system and it cause's engine lights
Don't miss those oil changes and ALWAY use recommended oil..... ahhh, they still fu*k up alot

 

umm... NO!

both the 2.0L and the 2.2L are rated at 240 hp at the crank. the americans get the the 2.2L in 2004 because they b1tch about how the engine has no torque for the daily commute. although they increase the torque with the 2.2L engine, the max rpm was reduced to 8000 rpm. the rest of the world still gets the amazing 2.0L to comply with certain racing class.

 

the honda version of the variable flow turbo seems to be more reliable because it only has one flap although probably not as effective as the other setup. there's a nice flash on the acura website that shows how the variable flow turbo works.

 

see, next, my apologies, hit the wrong button, tried to fix it, messed it up again...

 

Chevy uses almost the exact same turbo as the one on the 6.0 in their isuzu engines. At first there were issues with these turbos but they have all the bugs worked out now, and that's both companies. I'm not sure what line of work you are in using an F550 but cleanliness is an issue. Change your oil often and don't use synthetics. Synthetics will retain some of the dirt particals that would be washed out with normal diesel oils. Synthetics have suspensoin properties that are harmful to the injectors and small sensors on these highly sophisticated engines.
As far as the way of the future, I can see that, however they are a lot heavier and larger than normal turbos, compare the size of a wastegated 7.3 liter turbo to a 6.0 turbo. However the 6.0 turbo will boost higher, all across the board, if they can make them smaller for applications like these evos, you will have no lag, much higher response, and just as good if not better boosting capabilities.
Since you guys are using an F550, I am assuming it's a fleet vehicle. Those are the most troublesome because they are not properly maintained. The other day I saw a guy that was driving an ambulance complaining about performance, he had 11,000 miles on the oil change and the engine mostly sat at idle, i'm shocked it still was even running.
I do know that for the new ford engine by international, the issue of the vgt valve and variable geometry turbo will be fixed.

 

Since I design axial compressors, I might have a little something to add here. Variable vane technology is not new. Like stated before, its been around in all shapes and forms for a while.

The whole aspect of using variable vane technology does help spool quicker, but does anyone know why? Because you are changing the characteristics of the flow is the simple answer. More complex is the surge line. Most of our compressors are designed to not surge at peek boost or pressure ratio...what hurts here, is on the bottom end of the curve where the flow may not be laminar, which we all experience as turbo lag. By changing the relative velocities of the flow, one can design the compressor blades to produce maximum (or theoretical maximum) lift at lower fluid velocities. Think of it as flaps on an airplane wing. At low speeds, pilots use the flaps to produce more lift. At high speeds, the flaps would genereate too much drag, or the flow would become turbulent over the wing and the airfoil would stall (surge for compressors). So after achieving lift off, (or low engine speeds in our case), you change the wing shape, i.e., retract the flaps (in our case, change the vane angles so that the relative velocity doesn't produce turbulent flow over the airfoil).

Not a new science, but definitely a cool technology to be applied to our turbos.

 

To give a little more help to what 56Hotrod is saying, here's a link

http://en.wikipedia.org/wiki/Variabl...y_turbocharger

This will help those who don't understand, here's what he's saying into picture form. I don't design the turbo's, but I have seen, tested, and modified thousands of vgts. I didn't realize they have been around on gas engines, my only experience is with diesels.
C

 

I havn't taken my fluid-dynamics refresher lately... so all I'm gonna say is +1

 

using fluid dynamics to change aerodynamics....mmmm...physics...mmm

 

You obviously haven't driven one. Do urself a favor and go drive one before sticking
ur other foot in ur mouth.