ledzepp3

iTrader: (1)

So this is just an idea... But I've never really seen it done.

I've seen people run compound boost setups with a turbo feeding into a roots or twin screw blower, but has anyone run a turbo into a centrifugal supercharger? It just seems like a weird concept but one that could have its merits, that you have double boost (assuming it would work) at the top of the rev range.

Meth Sled

iTrader: (1)

Sub'd! I've thought about this as well, makes me wonder if you can spin the centri. fast enough it'll start spinning the compressor wheel, in turn, spinning the exhaust wheel and thennnnn sucks exhaust out of the motor! Makes sense in my head, lol

stevieturbo

You would not have double boost and really overall airflow will still be limited by whichever is creating the most airflow.

You twin charge so one type of boost will assist where the other might lack, so in the case of turbos and centri you'd maybe want to use very small turbos and blow the centri through them.

Turbos take care of the low end, centri takes care of the top.

Or with much larger turbos the centri wil take care of low-mid ( yes they dont make much boost, but they still help the engine make power ) with larger turbos taking over to make power up top, with the turbos blowing through the centri this time

Or blow a centri through a Rootes like this

ledzepp3

iTrader: (1)

It seems like without pushing ridiculous amounts of boost, the parasitic loss of running a double blower (centrifugal and twin-screw) wouldn't be worth it.. I was just curious as to why nobody turbos into a centrifugal blower, but what would be the benefits of putting something like a ProCharger onto a twin-screw?

RonA

iTrader: (1)

This one's a bit different.

stevieturbo

On a twin screw, probably none.

But on a far less efficient Rootes like in the video which are crap at higher rpm or boost its more obvious why.

Still more of a novelty in reality though

1CAMWNDR

iTrader: (21)

That is the way it really should be done. F1 or similar centrifugal overdriven to make boost just off idle feeding a larger turbocharger. Seen this done on several diesels with good results. Will it work for a gas engine? Don't know. Is it any better that a properly sized single or twin turbocharger? Doubt it.

stevieturbo

That's a large blower feeding a small turbo, the turbo will be providing the low end, with the big Procharger taking over up top.

JoeNova

A while back, Hellion pushed twins though a blower (can't remember if roots or screw). Made like 1100 wheel at 44 PSI. The turbos alone made 1000 at 26 PSI. The blower was just super-heating the air

Most big power compound guys run a turbo into a turbo. This is how the diesel guys hit 80-100 PSI.

zrultima

Yeah i can tell you from experience i have a 63mm feeding my s480 in my truck i can hit 70 psi easy. But i keep blowing boots

stevieturbo

Compound is largely for boost multiplication though which isnt something you need on a spark ignition engine for the most part.

Using 2 different types or sizes of FI on an SI engine are generally to give a better spread of power over as wide an operating range as possible.

SO perhaps thread title is a little wrong for how it should be implemented here

1CAMWNDR

iTrader: (21)

Aha! OK then.

chuntington101

Volvo has done some very interesting stuff around this recently. On their Diesel engines they are looking to use compressed air injected into the exhaust manifold to help spool the turbo(s) quicker. On their spark engines they are using an electric supercharger to supplement the turbos down low.

BMW tend to go for sequential turbos and their latest diesels are tuning 3! That's one large on and two smaller units. One small one at low rpm and then the big one and the nice smaller on right at the top.

Porsche have don't VNT turbos but are probably just selecting a better matched turbo with the next 911 engine (that is turbo'ed).

Again it all depends on what you are trying to achieve. Do you really want supper low end boost? If so drop a heartbeat or whipple on the car and be done. If you want mid to top end power look at turbo(s) or centri supercharger.

The reason the diesel guys are doing it is they want over 100psi manifold pressures. That's around 8 time atmospheric pressure at sea level! A single state turbo can probably get you around 4 times atmospheric efficiently. So you need at least two stages to get you to target boost.

stevieturbo

Some modern Porsches do have VNT

That or staged sequential probably are the future whilst keeping costs and reliability viable.

chuntington101

I don't know steve, these electric superchargers seem to be making some progress. Then there is the KERS style systems used on the Hyper cars. These are the real answer but probably some time away from mainstream use.