Theory on dropping 0-60 for you n/a!
07-10-2001, 07:12 AM
#16
Race Director
There are a couple of issues here:
1. POSITIVE DISPLACEMENT - this means for each rotation of the blower, you need a set volume of air moved. Unlike a squirrel-cage or regular leaf-blower fan-baldes, roots-type supercharger has sealed rotors, so if you have restrictions, the pressure will increase continuously with each rotation (like pumping up bike-tire). If you completely block off a leaf-blower or squirrel-cage, it will stop flowing, but it won't build pressure either.
2. VARIABLE-VOLUME ON DEMAND - Turbos and superchargers are RPM-sensitive devices. An engine at 6000rpm requires 2x as much are as 3000rpm. At 15psi of boost, it requires 4x as much air. How can you achieve this with an electic motor? Remember, these leaf-blowers are about the size of a turbo. But can they run at 125,000rpm like a turbo? That's the kind of volume that you need.
3. EFFICIENCY - Electric motors are notoriously inefficient. But that's not all there is to it. First you have to convert mechanical energy from the crank into electricity in the alternator. So you lose 30-40% there. Then you conver this BACK into mechanical energy to drive the blower (losing another 30-40%). So you expend 10hp to create an airflow that contains just 2hp of energy. Better to use that crank power to blow the air directly like in a supercharger.
We went through all of this about a year-and-a-half ago on the email list. After much heated debate, the electric supercharger guy still wouldn't produce a dyno chart. Someone mentioned that the electric supercharger would be better used as a turbine facing backwards. From the stated amount of thrust it gives, the math indicates it is worth about 0.3-lbft of torque at the crank (while sucking up 5hp of electricity).
Check out these legitimate power boosters:
http://www.geocities.com/MotorCity/D.../poweradd.html
-danno
1. POSITIVE DISPLACEMENT - this means for each rotation of the blower, you need a set volume of air moved. Unlike a squirrel-cage or regular leaf-blower fan-baldes, roots-type supercharger has sealed rotors, so if you have restrictions, the pressure will increase continuously with each rotation (like pumping up bike-tire). If you completely block off a leaf-blower or squirrel-cage, it will stop flowing, but it won't build pressure either.
2. VARIABLE-VOLUME ON DEMAND - Turbos and superchargers are RPM-sensitive devices. An engine at 6000rpm requires 2x as much are as 3000rpm. At 15psi of boost, it requires 4x as much air. How can you achieve this with an electic motor? Remember, these leaf-blowers are about the size of a turbo. But can they run at 125,000rpm like a turbo? That's the kind of volume that you need.
3. EFFICIENCY - Electric motors are notoriously inefficient. But that's not all there is to it. First you have to convert mechanical energy from the crank into electricity in the alternator. So you lose 30-40% there. Then you conver this BACK into mechanical energy to drive the blower (losing another 30-40%). So you expend 10hp to create an airflow that contains just 2hp of energy. Better to use that crank power to blow the air directly like in a supercharger.
We went through all of this about a year-and-a-half ago on the email list. After much heated debate, the electric supercharger guy still wouldn't produce a dyno chart. Someone mentioned that the electric supercharger would be better used as a turbine facing backwards. From the stated amount of thrust it gives, the math indicates it is worth about 0.3-lbft of torque at the crank (while sucking up 5hp of electricity).
Check out these legitimate power boosters:
http://www.geocities.com/MotorCity/D.../poweradd.html
-danno
07-10-2001, 11:13 AM
#17
Instructor
Join Date: Jun 2001
Location: Washington, DC
Posts: 124
Likes: 0
Received 0 Likes
on
0 Posts
I really can't believe people are looking into this idea seriously. Oh well, I guess it just goes to show how creative some people will be in their quest for more power. From the math side of things I have to agree with Danno. Most things electric will probably suck more power than they will give back in HP. I should talk to my dad though, he designs special project alternators for a military contractor, maybe he can cook something up for you guys on a group rate or some such thing to power all those leaf blowers 
. Good Luck in the quest for cheap HP.
. Good Luck in the quest for cheap HP.