e-charger/electric supercharger

[mateo9944]

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:

1. dry air at sea level
2. atmosphereric pressure = 14.7 PSI
3. single stage adiabatic compression

(yes i know this is also idealistic)

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

 

[NCZ13]

If you do go through with it, it will definitely be a first for these boards that ive seen.

Its obvious you know what your talking about. When i saw this thread title i thought to myself "well i guess we were due for this kind of question" as it has been a good couple of months since the last electrical s/c thing came up.

however its pretty clear you put some thought into this. However remember that you cant just shove air into the engine w/o compensating with fuel. The stock ECU isnt going to know what to do with it all the air, and the AFRs is whats going to hold you back, so some open loop tuning will be required for this to work...

 

[TWISFM]

wow not what i was expecting at all.. DO IT! then let us all know how it feels.. then we buy.

 

[TWISFM]

woah just saw... 4 grand for a super charger turbo thing... i think not.

 

[mp3-79bronco]

that sounds like a cool project...no need for a intercooler, should have a very responsive turbo lol....u just hit the switch and all of a sudden your boosting full psi

 

[lil_red_wagon]

(outie)

 

[ForceFed]

(outie)

^ I'm with this guy.

 

[mateo9944]

however its pretty clear you put some thought into this. However remember that you cant just shove air into the engine w/o compensating with fuel. The stock ECU isnt going to know what to do with it all the air, and the AFRs is whats going to hold you back, so some open loop tuning will be required for this to work...

I forgot to mention this part of my plan....
I am planning on controlling the motor's speed using an avr based controller.
The goal is to use enough sensors that you can feed the controller the amount of boost you want and it regulates the motor speed to maintain that level.

Somewhere along the way i got the notion that I can run up to 2 PSI with the stock ECU and be ok(someone correct me if I am wrong). So I was planning on getting it to work at 2 PSI and then going for megasquirt so I can manage fuel and timing.

 

[mateo9944]

that sounds like a cool project...no need for a intercooler, should have a very responsive turbo lol....u just hit the switch and all of a sudden your boosting full psi

Thats the idea! I really don't want something that runs all the time as it is my daly driver, but occasionally a little more low end torque would be nice. I'm looking forward to having imediate boost at the flip of a switch

 

[Mustang Matt]

Did you go through with it?