Quad Turbo

[tinnmann]

OK, so I have a neat but maybe improbable idea. A V12 engine with 4 turbochargers. One turbocharger for every three exhaust ports. And if possible a cold air intake on each turbocharger. The turbochargers would be smaller than normal ones, as to reduce blowback into the combustion chamber. I know the smaller turbos have special blowout valves so they dont blow up because of high pressure at really high speeds.

 

So is there anything that I should know before i get to involved and start making designs. Or does anybody know if this has already been done.

[Ndi]

Not likely to be done because it's not efficient.

 

An optimal capacity per cylinder is roughly 500 cmc. Meaning you get long life and prosperity from 2L inline 4, 3 liter-ish V6, 4 liter V8 and so on. A V12 is likely to be around 6L and 4 turbos would mean a turbo for each 1.5 liter. There's a reason 1.5 engines don't come in turbo too often.

 

The point is that if the engine is too small, the backpressure created by the turbo is kinda high. You have a lower efficiency than a 2.0 engine with a turbo.

 

Also, the engine needs to spin the turbine at a decent RPM, so the turbo needs to be spinning decently at around 2500-3000 RPM, meaning that by 5000 it's already near peak, at 6000-7000 it no longer delivers as it should, acting as a restriction. A turbo that is larger can move more air and can be more efficient, but needs more pressure to work.

 

For a V12 the better setup would be a twin turbo, each on each 3 liter bank. The turbos are quite large and can serve, but they take time to spool, so turbo lag is an issue.

 

If you really want to design a quad turbo setup, look at cascading turbines or try to make it a twin turbo per bank, with a smaller turbo that spins at 1500, faster, and delivers up to 3000, giving the larger one time to spin and deliver over that. You can achieve that by wastegates/blowoffs and maybe electric valves. A good place to start is the Porsche 911 biturbo, I understand it uses a cascading setup (not sure though)

 

You should look at the 12 cylinder as two in-line 6 engines and try to maximize those. In practice, a V has two intakes and two exhausts so you can use that to your advantage.

[tinnmann]

I did some research on the topic of quad turbo and I found that the Bugatti Veyron uses 4 turbochargers. But that engine is a W16. Thats pretty much 2 V8s side by side.

[Ndi]

It's an 8-liter engine, making the quad setup

 

a) necessary - each bank needs a turbo, but also

b) expected - each turbo is on a 2 liter bank, which is just about right for the expected capacity for a turbo - 1.8-2.2

 

You can have the same setup for a V12, with a turbo on each 3-cylinder bank - it's been done before - it's the capacity that bothers me. You'll get one heck of a drag car but it's unlikely it will set any speed record.

 

Edit: It's not pushed all the way yet. You can expect improvements on the engine if they want to.

[chilehed]

A V12 engine with 4 turbochargers. One turbocharger for every three exhaust ports...So is there anything that I should know before i get to involved and start making designs...

The first thing you should know is that you'd better have a LOT of spare cash to blow. You'll need it.

 

This is a very difficult project, but I think it could be done. The dynamics of exhaust flow are such that banks of three cylinders per turbo are ideal. Sizing the turbos won't be any more complicated than for a twin-turbo application, each turbo just handles less flow. It will be a nightmare dealing with the plumbing and the heat radiating from the exhaust system.

 

Unless you have a strong engineering background, a lot of practical experience desining multi-turbo systems, or have hit the lottery, I'd leave this idea alone.