Induction?

[Rich328]

Ive been reading alot about induction kits for cars.

Im just wondering whether it is worth putting one on my 328i Convertible, what differences would it make (if any).

I had one on my previous car - but that was only a 1.2i 16v and it seemed to make a difference to that.

[BlantonG13]

depends what kind of induction...forced, Short Ram, CAI, etc...specify?

[Rich328]

well the type i had on my previous car was a K&N air filter - it was shaped like a cone.

can u tell me possibly what the better one is and there main differences etc.

thanks

[bitcore]

Forced induction = Turbocharger & Superchargers

A turbocharger relies on exhaust gas pressure to spin up an intake turbine, which creates a higher compression ratio inside the engine. These suffer from "turbo lag" because, to spin up the intkae turbine, an addex exhaust pressure needs to be there to spin up the exhaust turbine. http://www.howstuffworks.com/ Article about how turbochargers work is on the front page of hostuffworks.com right now. (direct article link)

a Supercharger is basically a belt driven turbocharger and dosn't put backpressure on the exhaust which is a good thing for high end torque, bad thing for low end torque.


Naturally Aspirated: (AKA: N/A)
Basically an air filter. Stock airfilter is an airbox with a rectangular filter.

Cone filters in the engine bay replace the airbox and are less restrictive, you need a heat-shield to prevent hot engine air fron being sucked into the intake.

Cold Air Intakes (CAI's) are basically an extension of a cone filter, the filter is placed somewhere away from the engine to suck up colder air, which allows the air to expand more when the fuel is burned, producing more power. In BMW's, usually the airfilter is placed in the front air-duct and a tube is ran from the engine's intake to the filter.



There has been talk of electric superchargers, (advantage is they remove load on the engine's belt system) but there isn't an electric engine powerful & small enough to provie an efficent ammount of thrust.

[ClarenceT]

Originally posted by bitcore@Jul 28 2004, 02:37 PM
There has been talk of electric superchargers, (advantage is they remove load on the engine's belt system) but there isn't an electric engine powerful & small enough to provie an efficent ammount of thrust.

Actually there's definitely powerfull enough, and yes you can get them in pretty small packages. The problem is efficiency - that thing will suck your battery dry, if you got one that could match the output of even a smallish mechanically driven compressor. To make up for that, you'd have to go to a larger output alternator, which once again is an extra load on the motor. Just because it's electric doesn't make it "free" - that energy has to come from somewhere. All the electric turbo kits out today are scams. Meybe some day they'll make something worthwhile, but don't hold your breath.

[bitcore]

piston-driven electric compressors do not output air fast enough, they have lots and lots of power and can compress air to high pressures, but they are slow and produce spurts of pressure. Piston compressors are the 'diesel engines' of the compressor world, lots of torque, not so much horsepower. Turbo-fan and piston compressors are two different animals.

Typically, if your nuts enough to use an electric supercharger, you have a totally isolated electric circuit ran on a seperate battery (or a nice batcapp) somewhere else in the car, not being charged by the alternator. (or switched so you can charge the battery when you don't need the boost)
To spin the turbine fast & hard enough, you need some hefty torque, electric motors capable of produceing enough torque are rather large and draw a BUNCH of current. EXTREMELY high current at low voltages such as 12V

1/2 HP electric motors that run on 120v 60hz AC are rather large and draw a TON of current. At 120V AC, they draw about 10 amps, so about 1200 watts. At 12V DC, taking into consideration the inefficeny of such low voltage and voltage drop when running high current from a battery, you need about 110 amps (probably much more) of juice to run a badass electric supercharger that's powerful enough to produce enough boost at all. Hell, stock E36 alternators are 80 amps, some 30 of those amps are used continuiously for ignition, etc etc. and 80 amps is never actually produced untill RPMs are very high.


Yes, electric superchargers arn't that great now-a-days and I don't foresee them becoming any better or useful as opposed to a NOS or other FI system.

[BlantonG13]

couldn't have explained it better myself fellas...good puddin