Centrifugal Supercharger
05-20-2004, 12:02 AM
#31
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by Fluid Dynamics' date='May 19 2004, 08:59 PM
Lol, yeah, 2 psi aint much, but I don't want to pop my NA block. The higher CR rotors should respond a little more than if we were talking 2 psi on a turbo II block, but yeah, I won't exactly be running low 13s at the dragstrip. Mid 13s perhaps? 6 psi with water injection @ 7500 rpm on a streetported NA block with full exhaust should be (conservatively) worth mid 200ish crank HP. My FC weighs 2400 lbs empty right now . . the SC would not add much to that weight.
The Whipple is a twin screw supercharger that works similarly to the roots type (full boost right away) but is much, much more efficient, and needs less intercooling for a given amount of boost, and this allows it to run more boost and take less drivebelt power to do it. I've heard that most top fuel dragsters use twin screw superchargers. As you saw (Jeff20B), there is no contact inside the moving parts, just close tolerances. There are apex strips on the tips of the rotors of roots type blowers that seal the
The Whipple is a twin screw supercharger that works similarly to the roots type (full boost right away) but is much, much more efficient, and needs less intercooling for a given amount of boost, and this allows it to run more boost and take less drivebelt power to do it. I've heard that most top fuel dragsters use twin screw superchargers. As you saw (Jeff20B), there is no contact inside the moving parts, just close tolerances. There are apex strips on the tips of the rotors of roots type blowers that seal the
05-20-2004, 08:16 AM
#32
Senior Member
Join Date: Nov 2003
Posts: 480
Originally Posted by j9fd3s' date='May 19 2004, 06:39 PM
thats because he did it for like $52. i notice those guys will spend $200 on a peice of lexan but they dont want to pay $3 for an o ring to make the car run. its very odd
He seems to think he's got the obvious problem licked by adding a bypass valve. Well, it takes vacuum to open the thing, so as soon as the vacuum level drops too low, the valve closes and the system goes into "stupid mode", wherein it makes a gazillion psi upstream of the throttle. Even with a super huge blow off, it's still making too much psi. Gotta do wonders for throttle response too. It would take a book to explain all the flaws, but the problem is that anyone who needs them explained probably wouldn't understand anyway - until they try it and find out it doesn't work right.
Yeah, they were all proud for having "proven the experts wrong". Turns out the experts aren't so dumb after all.
Whipple supercharger - I believe this is a Lysholm type. I got to check out a Mazda Millennia S supercharger a while ago. The rotors are geared up and spin at a much higher rate than a roots. I read it was 21,000 and 35,000 for each rotor respectively at max engine RPM.
05-20-2004, 08:28 AM
#33
Senior Member
Join Date: Jun 2002
Location: PA
Posts: 354
my friend put a centerfugal supercharger on his bmw, and basically you coulnt tell. it did feel like it had a larger engine but watching the boost guage was kind of uninspiring, 1-2psi in the midrange and maybe 6psi by redline?
What's nice about an SC is you can just change the pulley to up the boost. My best friends Supercoupe makes 11-14lbs at WOT and he only runs the midrange pulley. We threw that pulley on in about ten minutes one afternoon...It was a SICK little upgrade from stock. As long as you have fuel to give, it's simple to add power with the SC.
05-20-2004, 10:54 AM
#34
Senior Member
Thread Starter
Join Date: Dec 2003
Location: Corvallis, Oregon
Posts: 419
Yeah, I'm on stock exhaust right now! The car pulls .5 g in first, .35 in second and about .25 in third gear. 0-60 is around 6 seconds, but I haven't tried doing a quarter mile or rwhp run in my Gtech yet.
My header is sitting about three feet away from me as I type. I'm just waiting on a few things before I install it.
My header is sitting about three feet away from me as I type. I'm just waiting on a few things before I install it.
05-20-2004, 11:12 AM
#35
Senior Member
Join Date: Jul 2002
Location: Fayetteville, Georgia
Posts: 2,483
Originally Posted by j9fd3s' date='May 19 2004, 10:39 PM
thats because he did it for like $52. i notice those guys will spend $200 on a peice of lexan but they dont want to pay $3 for an o ring to make the car run. its very odd
05-20-2004, 11:45 PM
#36
Senior Member
Thread Starter
Join Date: Dec 2003
Location: Corvallis, Oregon
Posts: 419
True. You can, however, get away with running more timing and a more aggressive fuel map if the intake air is cooler than that which comes right out of the blower. Any time any air is compressed, it heats up, whether it came out of a turbocharger or whipple twin screw blower. And besides, FMICs scare off the ricers so you can save your fuel for impressing the chicks.
05-21-2004, 03:56 PM
#38
Senior Member
Join Date: May 2002
Location: California
Posts: 22,465
Originally Posted by Fluid Dynamics' date='May 20 2004, 07:54 AM
Yeah, I'm on stock exhaust right now! The car pulls .5 g in first, .35 in second and about .25 in third gear. 0-60 is around 6 seconds, but I haven't tried doing a quarter mile or rwhp run in my Gtech yet.
My header is sitting about three feet away from me as I type. I'm just waiting on a few things before I install it.
My header is sitting about three feet away from me as I type. I'm just waiting on a few things before I install it.
06-11-2004, 12:32 AM
#39
Senior Member
Thread Starter
Join Date: Dec 2003
Location: Corvallis, Oregon
Posts: 419
Well if anyone cares, I've kind of given up on the SC idea for now. Good compressors are just too expensive for me, but usable stock turbos / manifolds are cheap as dirt on Ebay.
I'm leaning towards fabbing up a stock TII turbo, large FMIC, water injection, adjustable FMU, TII injectors, TII fuel pump, SAFC, BOV and ~5 psi on my streetport NA block for a goal of ~220 rear wheel hp and quick turbo spooling.
Three things about supercharging kind of suck:
1. Noise - NA rotaries with open exhaust are loud as **** for street driving.
2. Cost - a good centrifugal blower is at least 800 bucks used
3. Potential - Turbos are just more efficient and 300 rwhp looks much more achievable with turbo than a supercharger, if I ever get bored with a low 14 sec / high 13 sec car.
I'm leaning towards fabbing up a stock TII turbo, large FMIC, water injection, adjustable FMU, TII injectors, TII fuel pump, SAFC, BOV and ~5 psi on my streetport NA block for a goal of ~220 rear wheel hp and quick turbo spooling.
Three things about supercharging kind of suck:
1. Noise - NA rotaries with open exhaust are loud as **** for street driving.
2. Cost - a good centrifugal blower is at least 800 bucks used
3. Potential - Turbos are just more efficient and 300 rwhp looks much more achievable with turbo than a supercharger, if I ever get bored with a low 14 sec / high 13 sec car.
06-11-2004, 07:32 AM
#40
Senior Member
Join Date: Nov 2003
Posts: 480
if I ever get bored with a low 14 sec / high 13 sec car.
I did that with a street ported FB (NA 12A) - I would have thought the same could be achieved with an FC. Does the FC weigh enough to counter the improvement in power potential?
(and yes, it was pretty loud)