I will say this, IF you have a NA motor using 500 lbs fuel per hr at .500 BSFC PER HP and the blown motor uses 550lbs perhr at .550 bsfc per hp then the number would be 10%, IE they both make 1000 hp output but the blown motor is using 1100 hp worth of fuel to make that same 1000hp which translates to 100 hp, it also has the HEAT being transferred thru pistons to oil of a 1100 hp motor and 10% more stress on piston and other parts. If bsfc was .575 vs .500 that same 1000 hp example would be using 150 hp worth of fuel and mathmatecially using 150 hp to turn blower. The slower you can turn the blower the less parasitic loss their is. I tested a procharger m-3sc and it used about 50 hp to make 14 psi boost, bsfc went from about .495 to .520 which also translates to 50 hp or so at 1000 hp output, FWIW, Smitty

8000hp parasitic 600hp = 8%

That would mean 72hp parasitic loss on 900 hp. But I`m not pushing 74psi either so my belief is still less than that.

another factor is the more boost the harder the charger needs to work,that means the charger eats more power as boost goes up.smitty,i remember a post that said you were really over driving the 3sc.did you have issues with the drive belt slipping.reason i am asking is i have a 565 with a 3sc going to the dyno soon.

So in a essence by the enter cooler creating a air restriction it is creating boost and heat before the intake charge even goes through the inter cooler.

So to really confuse the matter. Why the resistance to turbo charging .

Back n the day Brownie talks of all the old turbo charged Daytona motors and what a hot package they were.

Than Mercruiser came out with the 454 daul turbo motor that made 475 horse with its tiny non water jacketed housings.

I ran little 300 horse turbo Yanmar diesels that had no lag what so ever . So what is the hold up with turbos?

yes but not much.

In this day and age,nothing,turboes can spool real nice now and self tuning efi can take the fear out of them.price may scare people off as turboes can get up there when needing custom.and no one really wants to buy used turboes,could be a time bomb just waiting to send a compressor wheel thru your intake system.
but I love the power you can get from them.
In a boat,it would solve some of the noise issues associated w/ big hp blower motors.

My guess, would be somewhere in the area of 50-100hp, on something like we have.

A 500HP engine, with 14.7lbs of boost, should theoretically make 1000HP, or double its power. And engine with 7lbs of boost, should gain 50%. So a 500HP, engine , should make 750HP . , with no parasitic losses.

My engine made 800HP with 7lbs of boost, and a roots blower. If the parasitic loss was 150hp, that would mean 950hp without the parasitic loss. With 7lbs of boost, that would mean my engine, n/a , would be making around 635hp. A 468 with dart heads, 9:1, and a 236/245 hyd roller, isn't gonna make 635HP at 6000. My guess would be somewhere around 550-575HP at 6000. That would put me at 850HP theoretical, and 800HP at the flywheel, so say 50HP loss to drive the blower.

50hp makes sense to me. I can't see my little crappy 10 rib drive belt, lasting very long if it had to turn a load of 150HP.

Most roots blowers have big cog tooth belts. Lots of marine guys run a 16 rib belt to drive their 871, 1071, etc. It works for that. I would not try running a 16 rib serpentine belt, in a blown alcohol engine, making 30 plus pounds of boost, because at that level, you need the big cog belt to drive the blower, as its taking a lot more HP than it is at say, 7lbs.

Heres a comparison of a centrifugal vs roots on Vortech's website. They are showing a "best selling roots', whatever that is, to be consumimg 69hp, while their centrifugal is consuming 48hp. About a 20hp difference. I'm guessing thats a pump gas low boost comparision.

A roots style blower is an air compressor...a whipple is an air mover and does not compress the air like a roots. That's why they run so much cooler and take less power.

I think you have that backwards scott. A roots moves air and does not compress it within the case, where as a whipple does compress it .

I belive a screw has less drag due to the much finer tolerances and no contact of rotor stripping , etc .