Alright, I am prepared to take heat/ get laughed at for this. I know a lot of people already have their opinions about these, but...
I will start with a little back ground info here:
I'm a Georgia Tech electrical engineering student. I like to mess with stuff just to learn, and especially if it hasn't been done commonly.
A couple weeks ago I came up(or thought I did) with the idea to use an electric motor to somehow boost my car. I have since done a little research and run some preliminary figures.
I have seen all of the cheap ebay "e-chargers" that are just fans in the intake and I agree that they are BS...
I have found one such system that I believe works.
http://www.boosthead.com/home.php
He uses a battery bank to power an electric motor turning a centrifugal supercharger for short periods of time(1/4 mile runs).
Before I jumped into buying parts and just throwing something together, I wanted to see how the numbers worked out. So I pulled out my copy of Pocket Ref by Thomas J. Glover
I found the P5's theoretical airflow at redline to be 228.5 CFM based on the formula CFM=[CID x RPM x VE] / 3456 where:
CFM is airflow in cubic feet per minute
CID is engine displacement in cubic inches
RPM is revolutions per minute
VE is volumetric efficiency ( I used 100% even though I know its wrong. I don't know the right answer)
I then calculated the theoretical horsepower to compress air to 6 PSI @ 230CFM to be 5.3 HP (this sounds low to me) using the formula:
HP=0.2267 Q[ (PSI / 14.7) + 1] ^ 0.283 -1] where:
HP= Theoretical Horsepower
Q= flow rate in CFM
PSI= gauge pressure in pounds-force per square inch
and under the conditions:
I then looked at the compressor map for a Garrett T25-60 turbo( only bc I have one (cabpatch)). http://www.not2fast.com/turbo/maps/t2560trim2kw.gif
I will assume air density of about .1 lb/cubic foot
@ 230CFM that is 23 lbs of air per minute
On the compressor map there is no data at that point, but a quick visual extrapolation leads me to believe the efficiency to be less than 50%
resulting in the need for 10 or more HP
Knowing all of this i searched for an appropriate motor solution and came up with this:
http://www.hobbycity.com/hobbycity/..._80-85-A_250Kv_Brushless_Outrunner_(eq:_70-40)
it is not ideal but it is cheap
it puts out roughly 8 hp
I have a four 18Ah 12v lead acids that can pump out enough current to run the motor at 8 hp laying around. I think i can use these to run the motor for a few minutes at a time.
so my plans are to design a custom housing to mount the motor and a set of gears to get the speed in the proper range and to have mounts for the compressor side of my T25.
I will then either find someone with a Bridgeport who is willing to let me use it or send it to one of my friends who is a CNC machinist.
This project is going to be a slow moving one bc school comes first and money is in short supply, but any comments would be appreciated.
Criticism will only help me improve my designs and any sage advise is always welcome.
Anyway, dinner time so more later.
Matt
I will start with a little back ground info here:
I'm a Georgia Tech electrical engineering student. I like to mess with stuff just to learn, and especially if it hasn't been done commonly.
A couple weeks ago I came up(or thought I did) with the idea to use an electric motor to somehow boost my car. I have since done a little research and run some preliminary figures.
I have seen all of the cheap ebay "e-chargers" that are just fans in the intake and I agree that they are BS...
I have found one such system that I believe works.
http://www.boosthead.com/home.php
He uses a battery bank to power an electric motor turning a centrifugal supercharger for short periods of time(1/4 mile runs).
Before I jumped into buying parts and just throwing something together, I wanted to see how the numbers worked out. So I pulled out my copy of Pocket Ref by Thomas J. Glover
I found the P5's theoretical airflow at redline to be 228.5 CFM based on the formula CFM=[CID x RPM x VE] / 3456 where:
CFM is airflow in cubic feet per minute
CID is engine displacement in cubic inches
RPM is revolutions per minute
VE is volumetric efficiency ( I used 100% even though I know its wrong. I don't know the right answer)
I then calculated the theoretical horsepower to compress air to 6 PSI @ 230CFM to be 5.3 HP (this sounds low to me) using the formula:
HP=0.2267 Q[ (PSI / 14.7) + 1] ^ 0.283 -1] where:
HP= Theoretical Horsepower
Q= flow rate in CFM
PSI= gauge pressure in pounds-force per square inch
and under the conditions:
- dry air at sea level
- atmosphereric pressure = 14.7 PSI
- single stage adiabatic compression
I then looked at the compressor map for a Garrett T25-60 turbo( only bc I have one (cabpatch)). http://www.not2fast.com/turbo/maps/t2560trim2kw.gif
I will assume air density of about .1 lb/cubic foot
@ 230CFM that is 23 lbs of air per minute
On the compressor map there is no data at that point, but a quick visual extrapolation leads me to believe the efficiency to be less than 50%
resulting in the need for 10 or more HP
Knowing all of this i searched for an appropriate motor solution and came up with this:
http://www.hobbycity.com/hobbycity/..._80-85-A_250Kv_Brushless_Outrunner_(eq:_70-40)
it is not ideal but it is cheap
it puts out roughly 8 hp
I have a four 18Ah 12v lead acids that can pump out enough current to run the motor at 8 hp laying around. I think i can use these to run the motor for a few minutes at a time.
so my plans are to design a custom housing to mount the motor and a set of gears to get the speed in the proper range and to have mounts for the compressor side of my T25.
I will then either find someone with a Bridgeport who is willing to let me use it or send it to one of my friends who is a CNC machinist.
This project is going to be a slow moving one bc school comes first and money is in short supply, but any comments would be appreciated.
Criticism will only help me improve my designs and any sage advise is always welcome.
Anyway, dinner time so more later.
Matt
