what is the difference between turbo and VGT ( variable geometric turbo)

can anyone please explain the difference between the above two and how the performance of a engine differs in both cases.

regards

Turbo

A turbocharger consists of a turbine and a compressor linked by a shared axle. The turbine inlet receives exhaust gases from the engine exhaust manifold causing the turbine wheel to rotate. This rotation drives the compressor, compressing ambient air and delivering it to the air intake manifold of the engine at higher pressure, resulting in a greater amount of the air and fuel entering the cylinder. Click this LINK/SOURCE of information, for further details.

VGT

Variable geometry turbochargers (VGTs) are a family of turbochargers, usually designed to allow the effective aspect ratio (sometimes called A/R Ratio) of the turbo to be altered as conditions change. This is done because optimum aspect ratio at low engine speeds is very different from that at high engine speeds. If the aspect ratio is too large, the turbo will fail to create boost at low speeds; if the aspect ratio is too small, the turbo will choke the engine at high speeds, leading to high exhaust manifold pressures, high pumping losses, and ultimately lower power output. By altering the geometry of the turbine housing as the engine accelerates, the turbo's aspect ratio can be maintained at its optimum. Because of this, VGTs have a minimal amount of lag, have a low boost threshold, and are very efficient at higher engine speeds. Click this LINK/SOURCE of information, for further details.

Great explanation by Pankaj. And the provided link also gives good information. Ofcourse a little knowledge of engines before helps. I also stumbled across this LINK where Turbo Charger design details of FIAT FIRE engine (which is doing duty on Bravo) is explained. Also written about is a brief on the already famous JTD range of engines.

Nice graphical representation provided at this link. And just looking at the numbers is mind blowing. 1.4L MPI Turbo charged being able to generate 148BHP!!! Just for this engine (1.4L) some highlights mentioned are:

1. 148 BHP
2. Top speed 209.3 kmph @ 5476 rpm (high speed @ lower rpm guess is good for mileage)
3. 0-100kmph in 9 secs!!!
4. 0-100kmph within 148.9 mtrs
5. 15% less CO2 emissions (ready for Euro V)
6. Turbo lag is less than or equal to 2 secs

What a list!! Looks like a wish list. And if i am not wrong then this could be on the Bravo which will be in India.

Bhusan, the information/link provided by you is indeed great. Thanks

Anurag, I'm happy that the link was useful to you.  Try the link Bhusan has referred to - I'm sure you too will like it.  Besides, I request if you can participate in the forums - there are many interesting dicussions going around & will definitely interest you. Thanks

148 BHP from a 1.4 litre engine         thats great for a petrol engine. they are also going to offer tata a new 1.2 ltr vtt engine to tata for indica. that engine is also claime to be very much ahead of the engines currently available here.

meanwhile now a 1.4 dicor inindica from tata is generationg only 70 bhp , i would like to confirm is tata using a turbo charger in indica or not because even in an indigo dicor with turbo they are giving same figures

Indica DiCOR, Indigo DiCOR & Indigo TDi are all turbo-charged (1.4 ltr engines).  The power & torque generated are...

1. Indica DiCOR:  70ps @ 4000rpm & 140nm @1800rpm.
2. Indigo DiCOR:  70ps @ 4000rpm & 140nm @1800rpm.
3. Indigo TDi:       70ps @ 4500rpm & 125nm @ 2500rpm.

try to clear when we accelerate some noise devoleped in vgt fitted vechcle.

Hi Pankaj

Just wanted to know whether the VGT turbo needs the ECM to control it.

Incase not hten can we replaces the old turbocharger of the TCIC Tata Safari with the NEW VTT Turbo. And if this is possible then what all changes will I have to do.

I would be very greatful  as I get very little tme to access met and that too after many days.

Thanks

Vineet Kaushik