I was reading the review of the new Fiat 500 Abarth and it mentioned a variable impellor wheel turbo (although I think its called an ihi turbo), this design of turbo is also used in the porsche 911 and is supposed to eliminate lag.

Thought someone might like to fill in the gaps and explain what they are and if they could be fitted to a 20vt

The answer will be something along the lines of yes if you've got enough money. I'd imagine a lot of mapping time would be needed.

Variable Vane Turbo (VVT), these have been used in diesels for a few years and now they are starting to make their way into petrol engines e.g. 997 turbo. They are a complex bit of kit as the actual geometry of the turbine and housing is changed so that spool can be increased at low rpms but efficiency retained for boost at high rpms. Fitting one to a coupe would be very hard to do and would require an aftermarket ecu to control the turbo geometry.

I don't call it VVT as people get confused with Variable Valve Timing. The name is VNT (Variable Nozzle Turbine). It’s good as it acts like a small A/R housing at low rpm and a high A/R at high rpm with a smooth transition between the two. It is always worth considering however it is far more expensive and has a poorer durability that the standard GT series although they are improving over time.

Here is a pic:
http://images.superstreetonline.com/techarticles/130_0508_turbo_15_z.jpg

If they are anything like the variable nozzle turbines like Nissan use, lots will be seizing-up.

a friend had one on a 1.4 R5 gtt, with suitable internal mods (fully forged, lightened & balanced)

trouble with traction sometimes, but was very very quick, would easily leave most coupes in the lower gears. full boost around 2ish k

Expensive or not, i would love to get one of these installed in my car

I don't know if the variable turbine is mechanical or if it's controlled by electronics.

I agree with Flea. I know for sure on a 16VT you would have problems mapping the car on a stock ecu because it's verry slow reacting to boost. I spent ages sorting the fuel enrichment during the spoolup zone on a 16V with a roler bearing turbo.

IHI is a verry good brand, i've got one of those on my delta.

one of my housemates has 3 garret gt28 variable vane turbos which he was going to put onto his supra but hase decided to go for a large single turbo instead and put up with lag. thinking of buying one off him to have a play with as he wants rid of them. if anyone wants to buy the other and have a play let me know.
they are a very good bit of kit and there as rare as rocking horse 5h1t, he imported them from the states, i guess it'll be worth it but will cost a lot.
btw you can just run them as a normal turbo at low boost so think i'll get mine installed then worry about the programming.

this is an interesting example of how they work

http://www.technologie-entwicklung.de/vtg-sequenz.gif

Surely for a coupe though a GT28 is too small as even a GT2871r isn't TOO laggy. A GT30 VNT would be a better bet.

its an equvilent to a gt28 will have to check the a/r range or compressor map to see if it'll work on a coupe. unfortunatly its a b1tch to find any info on the things as theyre so rare and from the states. will post a pic of them up when i can.



Dink - it works by an acturator connected to a control box which you connect to the inlet manifold by vacuum tubing, it regulates the actuator (and therefore vane angle). the manifold pressure is used to open and close teh actuator and is regulated by a valve in the control box (rather like a boost controller)

pwm?


if so, we could install an external boost controller and use the stock circuit for the EBV to run this via the overboost table...

Xav and others what do you think?

V.

The downside for tuning is that these turbos won't take extra boost very well. If you look at the aftermarket tuning pckages for the 997 turbo you'll see that most change the turbo

there are many vnt types on the market :
vnt with electronic control
vnt with oil pressure control
and vnt with pneumatic control..
and what comes to the size... gt30, gt35, gt42 and even gt45 is there ! gt30 is about 50mm / 50mm wheels,
gt40, what I have seen was 63mm compressor inducer and 65mm exhaust wheel. I can post you some Finnish e300 td mercedes pics with gt37 vnt turbo, if you want.. ( +400hp / 700nm )

VNT can replace the need for a wastegate also. They are not at all common in aftermarket applications. Only a few odd engines, usually diesels and small capacity ones.