Centrifugal Supercharger
05-19-2004, 04:22 PM
#21
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Lol, Nopistons has better info when you can see through the postwhoring, especially in the porting section. Kids seem to post more often than adults, and that may be why there is so much juvenile crap in cyberspace. 
Re. throttle response, etc. My main beef with the TII was the need to put my foot ALL the way in the gas and then wait a second or two to feel any real acceleration. My NA with stock exhaust and a street port / ported intake just jumps with a little touch of the gas . . I gave it a small but late closing primary port and it has excellent low end for an NA. I just want some instant boost on top of that. I don't want the full PSI low in the RPM range, but I want my little Wankel to still have some character, and turbo lag just ain't for me! After about half throttle I see atmospheric pressure in my intake manifold, and perhaps a little belt driven pressure could deepen the throttle range and keep the responsive feel.
Re. throttle response, etc. My main beef with the TII was the need to put my foot ALL the way in the gas and then wait a second or two to feel any real acceleration. My NA with stock exhaust and a street port / ported intake just jumps with a little touch of the gas . . I gave it a small but late closing primary port and it has excellent low end for an NA. I just want some instant boost on top of that. I don't want the full PSI low in the RPM range, but I want my little Wankel to still have some character, and turbo lag just ain't for me! After about half throttle I see atmospheric pressure in my intake manifold, and perhaps a little belt driven pressure could deepen the throttle range and keep the responsive feel.
05-19-2004, 05:33 PM
#22
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Interesting on the exhaust porting... I had late closing exhaust at
one point, and it basically acted weird - turbo didn't really wake up
until 4000, then came on hard. Then at 6000 it would creep another 3
psi until I changed to an electronic boost controller. Finally did new
housings, with stock closing and a little earlier opening - worked
alot better for me. I would have expected the airflow characteristics
to be shadowed in an NA application.
one point, and it basically acted weird - turbo didn't really wake up
until 4000, then came on hard. Then at 6000 it would creep another 3
psi until I changed to an electronic boost controller. Finally did new
housings, with stock closing and a little earlier opening - worked
alot better for me. I would have expected the airflow characteristics
to be shadowed in an NA application.
05-19-2004, 06:39 PM
#23
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Join Date: Jun 2002
Location: PA
Posts: 354
Correct me if I'm wrong with my train of thought. I'm not stupid, but I'm not an expert!
For pure driveability, a supercharger is a perfect thing (assuming that some complicated multiturbo setup is out of the question). Yes it saps power from the motor to drive itself, but that power is deducted from the power the supercharged motor makes, not what it would make NA...so it's a HP gain no matter what. A properly set up SC will register at 0 (no boost, no vacuum) at idle or maybe making a little boost, so the HP loss has already been overcome at idle by tuning. In essence, the driver would never feel the drag, only the benefit. In a turbo, until it spools you are running essentially as an NA. I guess what I'm saying is that it's more likely that an SC would make power earlier and smoother (though maybe not topping out at as high HP #'s as a turbo), making the choice a no brainer for someone wanting predictable driving characteristics.... As far as simplifying driving and making power it makes more sense than a single turbo.
Is my thought process faulty anywhere?
Personally, I want an SC on my 7 so bad I can taste it.
For pure driveability, a supercharger is a perfect thing (assuming that some complicated multiturbo setup is out of the question). Yes it saps power from the motor to drive itself, but that power is deducted from the power the supercharged motor makes, not what it would make NA...so it's a HP gain no matter what. A properly set up SC will register at 0 (no boost, no vacuum) at idle or maybe making a little boost, so the HP loss has already been overcome at idle by tuning. In essence, the driver would never feel the drag, only the benefit. In a turbo, until it spools you are running essentially as an NA. I guess what I'm saying is that it's more likely that an SC would make power earlier and smoother (though maybe not topping out at as high HP #'s as a turbo), making the choice a no brainer for someone wanting predictable driving characteristics.... As far as simplifying driving and making power it makes more sense than a single turbo.
Is my thought process faulty anywhere?
Personally, I want an SC on my 7 so bad I can taste it.
05-19-2004, 07:54 PM
#24
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Join Date: Jul 2002
Location: Fayetteville, Georgia
Posts: 2,483
Originally Posted by 1gendreemer' date='May 19 2004, 07:39 PM
Correct me if I'm wrong with my train of thought. I'm not stupid, but I'm not an expert!
For pure driveability, a supercharger is a perfect thing (assuming that some complicated multiturbo setup is out of the question). Yes it saps power from the motor to drive itself, but that power is deducted from the power the supercharged motor makes, not what it would make NA...so it's a HP gain no matter what. A properly set up SC will register at 0 (no boost, no vacuum) at idle or maybe making a little boost, so the HP loss has already been overcome at idle by tuning. In essence, the driver would never feel the drag, only the benefit. In a turbo, until it spools you are running essentially as an NA. I guess what I'm saying is that it's more likely that an SC would make power earlier and smoother (though maybe not topping out at as high HP #'s as a turbo), making the choice a no brainer for someone wanting predictable driving characteristics.... As far as simplifying driving and making power it makes more sense than a single turbo.
Is my thought process faulty anywhere?
Personally, I want an SC on my 7 so bad I can taste it.
For pure driveability, a supercharger is a perfect thing (assuming that some complicated multiturbo setup is out of the question). Yes it saps power from the motor to drive itself, but that power is deducted from the power the supercharged motor makes, not what it would make NA...so it's a HP gain no matter what. A properly set up SC will register at 0 (no boost, no vacuum) at idle or maybe making a little boost, so the HP loss has already been overcome at idle by tuning. In essence, the driver would never feel the drag, only the benefit. In a turbo, until it spools you are running essentially as an NA. I guess what I'm saying is that it's more likely that an SC would make power earlier and smoother (though maybe not topping out at as high HP #'s as a turbo), making the choice a no brainer for someone wanting predictable driving characteristics.... As far as simplifying driving and making power it makes more sense than a single turbo.
Is my thought process faulty anywhere?
Personally, I want an SC on my 7 so bad I can taste it.
So many turbo guys don't understand the benefits of SC a car. "Oh it's not using wasted energy," or "oh it doesn't have as much top end" or some other crap. The bottomline is if you want a smoother powerband, there is no substitute.
A supercharger installation is brainless according to all the instructions I've read...if you can change a tire you can do it. It will work as long as you have adequate fuel.
Not so with a turbo system.
Worried about spooling going around a corner and losing control? Not so with a turbo.
I won't be supercharging my motor, but you can see that I'm definitely not biased.
05-19-2004, 08:47 PM
#25
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Location: Corvallis, Oregon
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Originally Posted by 1gendreemer' date='May 19 2004, 03:39 PM
In a turbo, until it spools you are running essentially as an NA.
Yep, you guys understand what I'm after. I already know that you would never feel the drag of the SC when driving, just the net power it produces. It is like taking the NA engine you currently have and increasing its displacement by 30-50%. Same or very similar power band and response, just more of it, like when you install a header on a rotary. The power change is so subtle that you almost forget it's there, until you spank some ricers or break traction more often.
05-19-2004, 09:37 PM
#27
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Join Date: May 2002
Location: California
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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?
05-19-2004, 09:39 PM
#28
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Location: California
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Originally Posted by Fluid Dynamics' date='May 11 2004, 08:15 PM
I didn't read very far on the supercharger fab thread on the evil forum. The whole project looked hacked and not properly done. I would never run a supercharger at 8 psi on an NA block with:
1. No intercooling
2. Stock ECU
3. Stock injectors
Look at the mile long chain of fools bowing down to the guy who succeded in "hooking up" a supercoupe M90 roots blower to his FCNA. He basically made a bracket, some adapter pipes, an idler pulley, and hooked up a boost gauge. Tells you something about that place, doesn't it?
Thanks for the replies regarding the sound of superchargers, though. I like the idea of instant throttle response and a car that whines a little when it gets in boost. I drove a stock TII once and the (minor) boost lag and need for full pedal to get any torque wasn't my style. I'd rather keep the rotary and charge it instead of dropping in a larger NA engine that has pistons.
1. No intercooling
2. Stock ECU
3. Stock injectors
Look at the mile long chain of fools bowing down to the guy who succeded in "hooking up" a supercoupe M90 roots blower to his FCNA. He basically made a bracket, some adapter pipes, an idler pulley, and hooked up a boost gauge. Tells you something about that place, doesn't it?
Thanks for the replies regarding the sound of superchargers, though. I like the idea of instant throttle response and a car that whines a little when it gets in boost. I drove a stock TII once and the (minor) boost lag and need for full pedal to get any torque wasn't my style. I'd rather keep the rotary and charge it instead of dropping in a larger NA engine that has pistons.
05-19-2004, 10:52 PM
#29
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Join Date: Nov 2001
Posts: 2,284
I got to look at a Whipple SC today. It looks promising. Is it what you'd call a twin-screw? It had two large drillbit-looking things in it that fit with very close tolerances and no seals. It took like no effort to spin it just sitting there without a belt on it. I'd think it'll require less HP to run it than a roots (peanut) type.
05-19-2004, 11:59 PM
#30
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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