VNT/VGT Turbo's

[speed]

Will variable nozzle or variable geometry turbo's ever be a viable option for our cars?

My knowledge is very limited on such systems. I do remember much talk on them in the 90's and am aware that many manufacturers use VNT setups on diesel powered vehicles.

The concept is very attractive.

I've read about issues with petrol engines using such setups due to excessive EGT's and also the vanes clogging up with carbon and exhaust particles on diesel applications locking the vanes until dismantled and cleaned.

Apparently Porsche have had success on petrol engines but the cost of the turbo's is extremely excessive.

Could we see reasonably priced and reliable VNT or VGT turbo's in our future?

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[NitroDann]

We already have turbos which make >350rwhp and are lag free.

How much bigger a turbo do you want?

[The Zork]

Variable vane technologies were developed for the turbo F1 days. My 911-997 Turbo had this setup, which is standard Porsche from 2006 onwards. It is designed to get maximum torque out of the turbo at much lower engine speeds with reduced lag, then the vanes get streamlined as the speeds increases. The Turbo had 95% of peak torque from 1200rpm and felt like a rocket ship. Audi do this now also with great effect. I don't know whether a diesel turbo would be ok on a petrol engine.

[speed]

We already have turbos which make >350rwhp and are lag free.

How much bigger a turbo do you want?

Not really after more top end power.
I am interested in the concept of having all the power super low in the rev range and also up top.

I wasn't really planning on changing my setup per se just interested in the technology available.

As much as I enjoy my setup for what it cost me, an old school T28 slapped on the side of a B6 seems to be 1 size too large for anything low in the rev range.
A T25 would have been more suitable but after experiencing the kick the T28 gives, I couldn't go back to a smaller turbo.

Maybe one of your manifolds and a BB turbo would give better flow and spool up fast enough to address this.
In your experience, can the lag I'm experiencing with my setup be tuned out with boost control?

Variable vane technologies were developed for the turbo F1 days. My 911-997 Turbo had this setup, which is standard Porsche from 2006 onwards. It is designed to get maximum torque out of the turbo at much lower engine speeds with reduced lag, then the vanes get streamlined as the speeds increases. The Turbo had 95% of peak torque from 1200rpm and felt like a rocket ship. Audi do this now also with great effect. I don't know whether a diesel turbo would be ok on a petrol engine.

Apparently the Porsche turbos cost >10k US. Audi, Mercedes etc do run VNT diesel setups but all at lower boost. They are still exposed to clogging up and seizing the vanes.
Petrol engines do emit greater exhaust temps than diesels which is one of the reasons why the Porsche VNT setup is made of more whiz bang materials and cost significantly more.

The concept appears sound but the reliability and longevity on mainstream vehicles does not appear to have developed enough for our use.

Garrett have appeared to overcome this with their slider on the compressor side but I've not heard anyone using it.

It's all interesting stuff but maybe no longer a viable option with all the other readily available tech improvements in combustion engines over the years and a traditional BB turbo.

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