Calculating power required to drive a supercharger

[mgbizzle]

Does anyone know how to calculate how much horsepower or torque is used from an engine to power a supercharger?

Does anyone also know a company that produces small superchargers (possibly for bikes) that would have performance maps on their website.

[sparkyt]

Paxton do a small ish charger . But wouldn't a turbo be better on a bike .. as you would need the changer to spin to very high revs 12? To 14 ? K and the pully gearing for that wouldn't give you much lower down ...

[sparkyt]

www.eaton.com/Eaton/ProductsServices/ProductsbyCategory/Automotive/AutomotiveAftermarket/Superchargers/index.htm. eaton charger have maps on the site ..

[mgbizzle]

I looked at eaton but there superchargers are to big. It will be for a small car engine so I thought a something from a bike could be suitable.

[torment]

a freind of mine has a rotrex blower on his harley v rod,its making around 250 bhp at the wheel.

[sparkyt]

It's better the charges don't like being over reved as they get to a point when the boost starts to get hot and air density gets lower . The eaton m45 unit is not that big and suited to small engines I used the one from a merc as its ports and well placed for making up connections the mini unit was not so good .. you don't realy need to worries about the HP losses as they make HP almost from idle ..

[mgbizzle]

Jan 17, 2012 23:51:01 GMT sparkyt said:

you don't realy need to worries about the HP losses as they make HP almost from idle ..

This is all for a theoretical situation as I want to drive the supercharger from an electric motor, and so I need to know how much power would be required to drive the supercharger.

[stealthstylz]

Sprintex do the smallest supercharges that are easily available irrc.

[mgbizzle]

Jan 18, 2012 0:32:19 GMT stealthstylz said:

Sprintex do the smallest supercharges that are easily available irrc.

Brilliant the S5-150 is bang on what I want

[kabman]

I can't tell you about superchargers specifically but from working with air pumps in the past the torque is going to be a function of mass flow rate and pressure ratio. And I'm sure you know the power is a function of torque and speed. At a rough guess, a 1 litre engine at 2 bar and 6000rpm would be about 15kW. Is it a 12V motor you're thinking of? It will need to be HOOOOGE, heavy and suck a lot of current. A typical starter motor is about 1 or 2kW.

[claymore]

I ran my Fiat on the rollers with the charger boosting and not boosting

Results eaton m45
Standard HP: 147bhp
supercharger spinning but not boosting: 123bhp
Supercharger boosting: 186bhp

hope thats of some help

[sparkyt]

Maybe a roots is not the best .. nic the pump head off a turbo . Then the only problem you have is spinning it fast enough to produce boost . If you van find a motor to run it up to 75 to 90 k rpm your golden . Truck compressors from the states run from a 48v 3 phase ac supply rev to 75k rpm but cost is the problem . New the pump was over 3000 and the controller was over 2000 usd

[mgbizzle]

Jan 18, 2012 8:11:50 GMT claymore said:

I ran my Fiat on the rollers with the charger boosting and not boosting

Results eaton m45
Standard HP: 147bhp
supercharger spinning but not boosting: 123bhp
Supercharger boosting: 186bhp

hope thats of some help

Do you have the torque figures as well?

[chairchild]

Jan 18, 2012 0:21:17 GMT mgbizzle said:

Jan 17, 2012 23:51:01 GMT sparkyt said:

you don't realy need to worries about the HP losses as they make HP almost from idle ..

This is all for a theoretical situation as I want to drive the supercharger from an electric motor, and so I need to know how much power would be required to drive the supercharger.

Seriously? It's not even worth your time to look into it. They take SEVERAL Horsepower to spin up - I have seen one electric supercharger developed that *could* work... it was powered by essentially 3 VERY large starter motors. Consumed around 500-600A @ 12v


If it's for a small engine, ie: bike. A turbo is by FAR the better option


Just my 2p

[Bozwell]

Top Fuel Dragsters use 700 (yes seven hundred) horsepower just compress the air to 49 psi. (santa pod statistic)

[RobinJI]

Jan 18, 2012 8:11:50 GMT claymore said:

I ran my Fiat on the rollers with the charger boosting and not boosting

Results eaton m45
Standard HP: 147bhp
supercharger spinning but not boosting: 123bhp
Supercharger boosting: 186bhp

hope thats of some help

What do you mean by "supercharger spinning but not boosting"? If it was venting to atmosphere then it's worth noting that it will take more power to drive it against a pressurised intake than against the open atmosphere because of the pressure difference over the rotors.

It sounds like you've found what you're looking for now, but out of interest what's this going on? I'll echo what the others have said about the motor having to be pretty large.

[bm0p700f]

You have to assume adbiabitc heating of the air in the charger. Factoring heat loss is mathematically difficult.

For any abiabtic process PV^g = const. Intergrating PdV for a change in volume give work done. Volume has to change for work to be done.

At some point I have done the same calculation for a turbo charger and the formula I used was

W = (CpT/e)((p2/P1)^((g-1)/g)-1)

W is work
Cp is a heat capasity =1108 Jmol^-1K^-1
P2/P1 is the pressure ratio
g =1.4 and the ration of heat capasities cp/cv
e is the efficency of the compressor
T is the thermodynamic temperature

However I cannot tell you know how I arrived at this.

Doing some research for any abiabatic process the work done in compressing the gas is as follows:

W = nR(T2-T1)/(g-1)

n is the number of moles of gas you have
R is the gas constant

I do not know how accurate these formula are here they are in these links
www.engineeringtoolbox.com/horsepower-compressed-air-d_1363.html
www.truetex.com/aircompressors.htm

[bm0p700f]

Rotrex do a range of superchargers as well.

[lewist123]

In theory, you could look at using a brushless RC 'plane motor. You can get some SERIOUS power outputs from the little buggars (like a few Kw!). But you really really need to run them at very high voltages to reduce current draw and heat loading. You would need to match KV rating of the motor, to the input speed of the charger vs voltage input and power dissipation.

All possible though. Don't use a brushed starter type motor. They are just too inefficient.

[mgbizzle]

Jan 18, 2012 16:07:35 GMT RobinJI said:

It sounds like you've found what you're looking for now, but out of interest what's this going on? I'll echo what the others have said about the motor having to be pretty large.

This isn't going on anything, I'm completing a project for university. Although the more I'm looking into it the more viable it is looking using an brushless motor designed for r/c use.

Obviously on a large engine an electric motor isn't viable, but on things under 1400cc its a realistic idea. I'm also only investigating use for something like a hillclimb event where the system doesnt have to run for very long and will use its on battery circuit.