99SS-T

iTrader: (5)

I did a fast search adn came up with nothing. Im sure its out there but im tired as **** but wont remember to ask this question tomorrow. Why is it that Roots blowers are able to make all teh boost they want, nearly as soon as the car goes WOT? At nearly any rpm? Im pretty familiar with how the blower forces the air in but im not sure why a centrifugal supercharger cant do the same?
This question stemmed from this video and dyno graph. Thanks
http://svtperformance.com/forums/sho...d.php?t=308626


John

fastformula309

huh i never knew a sentrifical charger couldnt..

bboyferal

iTrader: (9)

You didn't? Well, a centrifugal supercharger's boost relies heavily on rpms... You just can't go WOT at any rpm and expect boost... Max boost at redline with a linear curve.

ponygt65

Roots spins differently. 'more direct' than the centrif. The centrif also has to push the air up the inlet to the TB. The Roots, is manny mounted and air goes in direct, hence quickly.

Centrif. are great for 'building' boost and max HP. Roots (manny mounted) are great for TQ, and intant boost. Just depends on what type of power you are looking for really.

gametech

iTrader: (1)

Thie roots blows the same amount of air per revolution at any rpm(disregarding certain inefficiencies of course). This is why it is called a positive displacement blower. Unfortunately, it generates a lot of heat in the process. The centrifugals are more like a turbo. They are most efficient at high impeller speeds. The amount of air they move is not linear, it is exponential. Think fan vs air compressor.

ponygt65

Sure, get technical on us......J/P

30th t/a

iTrader: (51)

dammit why isnt KB or whipple making a roots type supercharger for the Fbodys????? jezzzz!!!

engineermike

An internal combustion engine is a positive displacement device. So, you add a positive displacement supercharger that will directionally flow more air than the engine. The excess of flow translates into "boost". Since they are both positive displacement devices, then it doesn't matter how fast you spin it, it's just more of the same. However, a centrifugal supercharger has completely different flow characteristics than a PD supercharger. Pressure is proportional to the shaft speed squared. Divide by the linear airflow requirement of the engine, and you get a linear rising boost curve.

Mike

Project GatTagO

iTrader: (7)

Neither KB or Whipple use roots style superchargers. KB uses Autorotor (made by Opcon) superchargers which are a twin screw design. Whipple used to use Lysholm (also made by Opcon)superchargers. Now they have ripped off that design and are making their own superchargers. Twin screw superchargers actually build pressure inside the case.

Andrew

chriswtx

iTrader: (5)

I ditched my Magnacharger(roots) for a Paxton Novi 2000(centrifugal) and couldn't be happier. The roots did make instant TQ and boost, but the power and boost really fell off above 4800rpm. By 4000rpm the Paxton is making more torque and hp than the maggie ever did and with 2psi less boost. I made 510rwhp at 12psi with the maggie. Changing nothing but the supercharger over to the Paxton and running 10psi I made 617rwhp and picked up 4mph in the 1/4 mile. Not to mention the heat soak problems with the Roots and Screw style chargers at the track since there all water to air cooled. The intercooler water and charger gets really hot between runs. If I were to ever make a change it would be to switch to turbos sometime in the future....

hawk584

iTrader: (1)

is there a Roots for an Lt1?

fastbasser

iTrader: (1)

Yeah but the Roots type blowers look great!! How much HP can you REALLY use??

bboyferal

iTrader: (9)

Besides, EVERYBODY LOVES to point out, "Oh, but the Roots/Twin Screw dies at the top of the powerband," or, "Oh, but it doesn't make the peak numbers of the centrifugal..."

Any Roots can make any numbers that a centrifugal can if it's the right size, which when both are at equal peak power outputs, the positive displacement SC will be better ALL AROUND anyway... WHICH is a moot point ANYWAY because, as it stands now, NO Roots/Twin Screw fits on an F-body any way of any size... Well, not without moderate fabbing... Not exactly a neat "fit."

Anyone seen the 2.6 KB for the Vette's power curve?

N4cer

iTrader: (11)

Why is it all these FI companies come and go claiming to be the shiznit, but none have the skill/***** to make a roots or a twin screw for the f-body? Despite their setbacks, they would sell like crazy!
I'm calling you wannabe innovators out! Do something, ya sissies!

99Hawk262

iTrader: (19)

Hell yeah. I'd be all over it.

bboyferal

iTrader: (9)

I guess maybe would-be developers feel there is no market of people willing to chop-up some cowl... I know, there definitely are some people... Maybe not enough.

N4cer

iTrader: (11)

Would you estimate they could sell 30? 50? I'd say that's an easy sell.

bboyferal

iTrader: (9)

I agree.

****, I love turbos... But even I may have gone Twin Screw.

I went turbo for area under the curve... And that Vette dynograph is just plain SICK. Twin Screw ftw!

I love how some Procharger/Vortech people (SOME) will criticize the lack of instant boost with a turbo, i.e. boost matched per rpm with the centri vs. spool/lag upon WOT with turbo, forgetting about early peak boost and area under the curve (With even some excuses like, "Ohhh, It would be hard to drive. ")...

And then go on to criticize, ironically enough, the positive displacement blowers CURRENTLY AVAILABLE for LS1's (the poor Magnacharger, for instance) by appeal to its lack of peak numbers after 600 rwhp, but not mentioning boost response at that time of course (read: INSTANT BOOST with this sucka!).

If SOMEONE was willing to make a BIG Twin Screw, so peak numbers WOULDN'T be an issue (~900 rwhp let's say), with some kind of BIG hood (like some Camaro owners, and a few Firebird owners, have ANYWAY on their cars FOR NOTHING BUT LOOKS), I bet people would literally freak the **** out... I would have to buy one myself!

LS1 performance industry, listen up! MAKE IT HAPPEN!!!

BUILD IT already!!!

LS1 Twin Screw!!!

N4cer

iTrader: (11)

Heck, the Maggie would be fine IF one of these wannabe tough companies would make it as a kit. HECK YES I'll cut my cowl! And my wife can lean over in my lap if she doesn't like the lack of a windshield wiper on the passenger side.
Guess I'll stay h/c for now, since last time I checked it's about $5k for a D-1SC with all parts I'd need just to run 5-6lbs. Not worth it to me for now.

bboyferal

iTrader: (9)

Yeah, man... The driver's the one that needs to see anyway!

And if you're driving a Roots/Twin Screw blown LS1 in the rain, you're just plain clueless anyway!