Exclusive sequential turbos?

[maat]

All right, let me disclaim this by telling you all I've only recently gotten into cars and especially forced induction, so I might be talking out of my ass. That and I know even if this is at all feasible it would mean a lot of expensive custom fabrication. At any rate, any comments would be appreciated (even if it means you're uprooting my most basic notions about how this all works)

So I'm looking to make a fast dsm a fun daily driver. For the fast part I'd need a big turbo, but for the fun daily driver I'd need a small turbo.

If I were interested in paying $30g for a supra I'd just use a conventional twin turbo setup. But the 2 liter 4g63 doesn't put out enough exhaust pressure to power two turbos simultaneously (afaik).

So here's my idea. Basically I want to get the two turbos spinning exclusively of each other. So when you're in the low rpm's, all the exhaust pressure goes toward spinning the first, smaller turbo. Gases go out the engine, through the turbo, out the wastegate and out of the car.

But then when you hit some critical point in the rpm range, maybe 3500 rpm's, or wherever the second, bigger turbo could be making a good amount of boost, we make the transition. This transition involves a couple of valves, which can all handle high pressure gases, switching at the same time. First, we're going to route all exhaust from the engine (that was going to the first turbo) directly to the second turbo. This turns off the input to the first turbo, so eventually it'll wind down. But instead of just letting it go, we're going to switch its output (that was originally going to the intercooler) to go to the exhaust input of the second turbo instead. This puts the first turbo's leftover angular momentum to good use, and should get the second turbo up to speed a lot faster.

Opposite for the transition from the second turbo to the first.

The only sketchy things I see are fabricating valves that can handle that kind of pressure, and when you're moving through the transition RPM's you won't have a steady amount of power. But that's the case anyway with any big turbo, and if we want a real daily driver we can just disable the second turbo entirely (as all the valve switching will be handled by some electronic unit anyway).

Thoughts? Has this been done before and I didn't catch it? Bashing encouraged.

 

[TurBoGs-T]

My personal opinion.

Don't even Phuck with it. Get you a big ass turbo and an electric boost controller. Have a high setting for race night and stock setting for daily driving.

 

[TurBoGs-T]

I didn't see a car in your profile so i dunno which one you have but instead of this two turbo idea why not just have a 2g as a daily driver with the small turbo and a monster 1g with the big turbo. For the cost of fabbin that twin turbo setup you can probably get you a nice 1g and a few mods.

 

[maat]

I'm under the impression that a big turbo won't give you much extra power at all at low rpm's, regardless of boost controller settings. I'd like more than the 135 lb/ft of torque or whatever these engines do without boost at low daily driving rpm's.

 

[90AWDTalon]

I've heard of this being done with a roots style super charger and a large turbo. Turbo Magazine did a write up of this on an mr2. The blower gives the car good low end torque untill the big turbo can kick in. On they're application they didn't use each one exclusively, both were going at all times. A similar setup can probably be done with a small turbo and a very large turbo, with out all the valves turning one off and the other on. This would be very complicated and expensive to do, they're are turbo's availible for DSM's that offer very good driveablilty and lots of power, the 50 trim turbo's are an excellent example.

If you want to do something no one else has done and you don't car how much work or money it takes, go for it. Other wise just get one of the many great turbo's available for our cars.

 

[TurBoGs-T]

I'm under the impression that a big turbo won't give you much extra power at all at low rpm's, regardless of boost controller settings. I'd like more than the 135 lb/ft of torque or whatever these engines do without boost at low daily driving rpm's.

Give us some more numbers.. What type of power are you looking to make on the daily driver side and what type on the race night side???

 

[kpt4321]

This sort of setup is very possible, and can be done with the right fabrication. However, ther are some difficult parts, such as when to switch turbos, and how to set up the piping. It's going to be difficult to cram all the stuff in a DSM engine bay.

If you want to talk tech, let me know.

 

[KFT0001]

For the cost of fabbin that twin turbo setup you can probably get you a nice 1g and a few mods.

You could probably get something a lot nicer than a 1g for the price of fabricating what he's talking about. Or you could probably even afford a vatn turbo (lags like a small turbo but makes power like a big one). Also, I agree that a supercharged plus turbocharged setup will be more feasible, as well as more efficient.