[hayasa]

Anyone know any of the stats related to the twins? Make? Boost levels? I had heard that they were "variable geometry" (seriously question that) and were twin scroll (also wonder if that is possible with three pipes feeding the spinner) - lots of weird speculation in the media write-ups I've seen...

 

[Nova]

I only see "variable geometry" with respect to the turbo in the diesel, which is likely very different from the one used for the gasoline engines.

The twin turbo low inertia design is more or less 'tried and true' by now. The BMW 335 demonstrated that this was a great way to get a lot of power with no noticeable turbo lag. I don't know how it is done in the Ghibli, but it likely doesn't stray too far from the 335:

Two low inertia turbos in parallel feeding a common intake plenum that is "by-passed" rather than blown-off on throttle lift-off. This keeps a part of the intake "on boost" during fast throttle transitions. This design dovetails with the overall low-boost design which in turn allows the low inertia design of the turbos. The 335i's stock boost was below 9 PSI, so I would be really surprised if the Ghibli's boost is significantly higher. I would say it's likely around 12-13 PSI at the high end.

 

[pitchfork]

Anyone know any of the stats related to the twins? Make? Boost levels? I had heard that they were "variable geometry" (seriously question that) and were twin scroll (also wonder if that is possible with three pipes feeding the spinner) - lots of weird speculation in the media write-ups I've seen...

Without seeing an engine cutaway its hard to say.

Do you have any photos of how the turbos are fed?

variable geometry? that sound confusing.

 

[Nova]

I found some photos of the Quattroporte V6, which is shared with the Ghibli S Q4:

Maserati - V6 e V8 Bi-Turbo ID e nuova 4x4 by Magna-Steyr

You can see the little turbo on the side of the engine. Nothing new or novel.

 

[hayasa]

Wow - some serious car porn at that site! Looking at the turbos on the V6 and V8, there is definitely something funky going on with those exhaust headers. The one on the V8 almost certainly is a twin-scroll from the exterior design, and the one on the V6 (and Ghibli) has some sort of pseudo-twin scroll (look at the tube coming off the middle port). There is also some sort of black plastic servo mounted at the intake side of the turbo - I'm thinking that is controlling the variable geometry, or maybe that is just a pressure sensor. Either way, I'm totally geeking out over the mechanical elegance of that set-up.

 

[Nova]

Right, the V8 is definitely a twin scroll design. The black plastic thing based on size definitely looks more like a servo than a boost sensor. Here's a similar variable geometry turbo design that has a similarly sized actuator also located on the intake side of the turbo:

http://www.movingmagnet.com/medias/applications/engine-management/variable-geometry-turbo.jpg

So it's looking increasingly like that the gasoline twin turbo V6 engines will also have variable geometry, which makes sense given that it'd be tough to do a twin scroll design on 3 cylinders. I found even higher resolution photos:

http://www.autowp.ru/pictures/engines/maserati_3.0_v6_twin_turbo_1.jpg
http://www.autowp.ru/pictures/engines/maserati_3.0_v6_twin_turbo_2.jpg
http://www.autowp.ru/pictures/engines/maserati_3.0_v6_twin_turbo_3.jpg

And even more photos:

http://www.bmwpassion.com/forum/showthread.php?246380-Maserati-nuovi-V6-e-V8-Bi-Turbo

 

[hayasa]

Here's a similar variable geometry turbo design that has a similarly sized actuator also located on the intake side of the turbo:

http://www.movingmagnet.com/medias/applications/engine-management/variable-geometry-turbo.jpg

So it's looking increasingly like that the gasoline twin turbo V6 engines will also have variable geometry, which makes sense given that it'd be tough to do a twin scroll design on 3 cylinders.

Very strange - I've never seen a turbo with variable vanes on the intake side. It is usually the exhaust side that mechanically adjusts to best match the exhaust flow, a la Porsche Turbo. Nice to see a short path from exhaust to turbo, too, which should really help with boost lag (in addition to being variable geometry.)

Any idea what they are talking about with the intake boost being "by-passed" on throttle lift? Maybe just fed back into the plenum? Aren't most stock turbos this way? (Before "tuners" install their blow-off valves, I mean.)

 

[pitchfork]

looks like a regular old turbo to me.

http://www.bmwpassion.com/forum/showthread.php?246380-Maserati-nuovi-V6-e-V8-Bi-Turbo
That V8 above in the link isn't for the Ghibli.

 

[hayasa]

looks like a regular old turbo to me.

Seriously? That thing looks like a work of art! Look at that den of snakes coming into the twin scroll! Still wondering about that black piece on the inlet, though.

I was looking at the Italian link and it says that the turbos are made by IHI, which makes sense since they have supplied Masers and several other major car companies with turbos in the past.

 

[Nova]

The actuator could really be anywhere, all it has to do is rotate the ring bracket that in turn rotates the vanes on the exhaust side of the turbine. Since we see multiple instances of variable geometry turbo having the actuator on the intake side, thus must be a common design.

These photos we've been looking at are from the new Quattroporte, which is why there is the V8. The V6 is the same, however, as the one in the Ghibli S Q4. The concept of a variable geometry turbo is not really new or novel either, although with electronic controls, the possibilities are more interesting.