The V8 Owners Forum -

Hi all, the rotex or procharger design chargers seem to have a turbo front on them, could one be home made converting an old turbo ??. If so what internals would be needed and does anyone know of a picture or diagram of the inside of one ???. rich

I have had the same thought.

They are called a Centrifugal supercharger and like you say are basicaly the compressor part of a turbo with a gear box on the back.

There is no reason why it couldn't be done if you can make your own high speed gearbox. They spin from 60,000 to 120,000 rpm depending on comrpessor size. I couldn't so brought a second hand procharger of the bay.

Rotrex, Procharger, Vortex, Powerdyne, Paxton to name a few are all centrifugal superchargers.

Tom.

Could be done but as said the gearbox would be the hard part not only in the gear cutting but in the choice of materials. Balancing would have to be done as well. You would also need to machine a housing/body as well of course but that's probably the easy part assuming you have the machinery and the know how

I'd have a go, but due to the fact they go to about 60,000rpm I'm not going to even try! Far too much to go wrong at that speed IMO. If I had a CNC mill etc and could make it to the thou it might be a different story...

As said above it can be done, you need to choose the right compressor wheel and housing, you need to hit the high efficiency platau just before peak power RPM, and run up through it to max RPM on a high flow compressor, the matching is different to that of a turbo application. As you don't have a waste gate to control the boost you can't run up parralel to the surge line and come across into the high efficiency zone as in a turbo application. It has to be a much larger housing and wheel, the sort of thing you would find on a big deisel (10 to 12 litre) engine application. The rest is as said above, a case of ballancing and a gearbox. Fortunatly these units tend to run at max revs of about 60-70K rather than the 100 to 150K range. have a look at some of the maps here http://www.rbracing-rsr.com/turbotech.html
Best regards
Mike

not a weekend job then , and i take it i will need more than a grinder and vice then, thanks for the replies , they spin up high then. thought the gears could be got rather than make. rich

Easier just to keep the hot side of the turbo and place it in the exhaust like everyone else does!

topcatproduction wrote:I'd have a go, but due to the fact they go to about 60,000rpm I'm not going to even try! Far too much to go wrong at that speed IMO. If I had a CNC mill etc and could make it to the thou it might be a different story...

Your alternator probably goes to 20,000 rpm when you hit peak engine revs. Just have a look at the sizes of them drive/driven pulleys.

You might even be able to run a turbo at somewhere near that speed if you used the correct V belt pulleys. Or use a larger (truck sized) turbo impeller end and run slower rpm?

20k is a long way short of 60k. You also need a largish charger pulley so you get a decent amount of belt wrap or the belt will slip. If it was as easy as using different pulleys I am pretty sure The manufacturers would have went that route instead of developing expensive gearboxes.

well it seems to be complicated, the gears seem to be the problem? rich

katanaman wrote:20k is a long way short of 60k. You also need a largish charger pulley so you get a decent amount of belt wrap or the belt will slip. If it was as easy as using different pulleys I am pretty sure The manufacturers would have went that route instead of developing expensive gearboxes.

I'd guess they want reliability and maintenance free operation for a gazillion miles.
You could use double pulleys, different diameters on the same spindle, to get the multiplication factor.

Maybe the torque would simply be too much for a V belt as well, when the boost builds up?

Toothed belts then?

It's one of those things I'll try for myself, one of these days......

There are two issues with sizing, firstly as I said above, you have a fixed ratio between engine revs, flow and boost set by the gear ratio you drive the thing at and compressor itself, you have have to hit the boost and flow you want at peek power somewhere in the high efficiency region and pass on up through it as revs increase past max power, that is fixed by the gear ratio. The second issue is related to the way the flow (and resultant boost) changes with revs, it isn't a linear relationship, double the revs of the charger multiply the flow by 4, this means at low revs around idle you have to ensure the compressor and housing can deliver enough flow for the engine, a big housing and compressor will deliver enough flow at low revs without over boosting the engine at max power.
Best regards
Mike

Rich,
my Paxton may be for sale if the news from V8 D next week aint good,
let me know if interested.

Thanks for the offer Tony, but hopfully you will have good news ,besides ive still got the twin turbos sitting here if i ever wanted to go forced. I just wanted to know if a charger could be done ,but it seems to complicated to me so better stick to nos me thinks. rich