DtS

..or is it engaged all the time. If it isn't how does it work? Is there some kind of magnetic "clutch" or something like that? I wonder because I think I can hear a clicking sound from the engine (just a single click) somewhere around 1500 rpm. Is this when the kompressor engages? When revs go down, from above to below ~1500 rpm, I don't hear this click....

Will you please educate me???

renncpe

There is no clutch on the 2002 C230K. The supercharger is spinning all the time. The older model kompressor motors did have a clutch system.

Randy

kompress

I understand that the supercharger is always blowing, and proportional to the engine speed, since it runs off of the crankshaft. That's why I prefer a supercharger to a turbocharger-- no turbo lag. It is also traditionally supposed to have better cooling characteristics.

bajaiman

I never hear any clicking sound from my C200K sedan (at the moment its at 15000 kms) at the rpm range you mentioned .... or maybe its so faint that i could not hear it.....did you just notice it recently?

CHECKMATE

Constant blow

DtS

Noticed it a couple of days ago. Well, it is very faint: I can't hear it with the AC on. After switching off the AC (which I regulary use in Auto-mode) I can hear something that reminds me of a "click" just around 1500 rpms. My car also has ~15000 kms. Going in for first service in two weeks, and will ask them about it...

NANA

I have read somewhere that the supercharger kicks in @ 2000 rpm and this is one reason why you feel the lag on automatics.

sdcaclint

re-read the thread, renncpe already said it doesn't kick in at any speed, it is always turning.

Iceman's C230

There is no clutch on the 2002 c230k. It is allways spinning...Constant Air Flow.. That's why i like S/C over Turbo.

Cryptnotic

A turbocharger or supercharger pre-compresses air coming into the engine so that the intake stage of the engine is easier and/or so that compression is easier (I forget which). How much compression you get is based on how fast the engine is spinning (i.e., higher rpms -> more compression).

A turbo charger is powered from a turbine in line with the exhaust. Turbos have a clutch device so that they "kick in" after a certain RPM. If they were on all the time, the turbine would cause too much back-pressure on the engine at low RPM's and would detract from performance.

A supercharger is powered from the drive shaft and has no turbine in the exhaust path, so it doesn't interfere with the exhaust at all.

At least, that's my understanding, which might be a bit flawed.

By the way, the pulley kits that people talk about increase the "spin" of the compressor fan, thus increasing the compression effect.
The compression causes a bit of a strain on the engine, but it should probably improve fuel efficiancy since more oxygen is getting into the cylinders to burn the fuel.





Cryptnotic

sdcaclint

i am going to put this as delicate as possible. Cryptnotic, you need to do a little more reading, and a little less posting.

Flashman

Actually, I haven't heard that clicking, but it does remind me of something else I wanted to ask. Does anyone know if/when the AC disengages when you accellarate the car for maximum horsepower?

My 1993 Miata disengaged the A/C for 2 seconds every time it went over 4,000 RPM. A feature designed to let you get maximum horsepower when you revved the car high. Though God help you if you happen to cruise at 4,000 RPM (on/off/on/off/on/off)...

My guess is that a car as advanced as the C230 probably does something similar, but more efficiently. But I don't know exactly how/when. Does anyone know?

Cryptnotic

Okay. Tell me how I'm wrong, and I'll read your response.

Spyke

Tee hee hee...

Yes, there was a flaw or two in the turbo description...

There is no clutch on a turbo. The turbine and the compressor are mounted on the same shaft. The turbine is always in the exhaust flow and the relative lack of power from a turbo engine at low rpm is more due to the engine's lower compression ratio than any added backpressure: remember, at low rpm there isn't much flow so there isn't much backpressure.

The "kick in" effect you're refering to is "turbo lag". At low rpm the turbine isn't spinning all that fast so neither is the compressor, meaning there is no boost. When you stomp on it, the turbo takes a little time to "spool up" to where it's going fast enough to provide any boost. This lag is more pronounced the larger the turbo is... when it finally does start providing boost, the effect CAN be rather pronounced so it seems like it's kicking in. It all depends on how the system is designed. It is also possible to design a turbo system that is virtually undetectible, other than the engine feeling larger than it is.

A turbo is simply one type of supercharger. All any supercharger does is provide a positive pressure in the intake manifold so more air is forced into the engine (forced induction) rather than relying on atmospheric pressure to do all the work. (No, a piston doesn't "suck" the air in, atmospheric pressure pushes it in. The higher the ambient pressure, the more flow you get)

There really is no "fan" on the C230's supercharger. It's a pair of (more or less interlocking) rotors that spin around... higher rpm = more mass flow = more "boost" = more power. The blower on our cars doesn't interfere with the exhaust, you're right, but don't be fooled. It takes one heck of a lot of power to spin those rotors at high rpm. Luckily, in our case spinning them creates more power than it requires.

Or something like that.

FrankW

mine engages at 3000 rpms if not under hard throttle. but if under hard throttle if will engage at even 1000 rpms.

for the curiousity i have a C32 AMG

Cryptnotic

Okay, that seems to make sense.

By the way, I'm not the only one with incomplete understandings of how these things work. It's something that seems to be going around.

I wonder if that clutch idea would work... if disengaging the turbine so that it didn't interfere with the exhaust would help things... You're probably right though, low RPM stuff wouldn't really matter... Engine design stuff really seems to be about trade-offs... trying to find the best performance that fits into certain constraints such as weight, size, reliability, complexity, fuel economy, etc...

Of course, by modifying things we can increase performance by reintroducing complexity and discarding concerns for fuel economy and reliabilty.

Spyke

Yeah, there does seem to be some interesting views on how engines work on this forum... (which isn't to say I'm always 100% correct by the way!)

Anyway, the turbine will be in the exhaust flow no matter what, clutch or no clutch, and again, at low rpm, there isn't enough flow to make backpressure a concern.

A lot of people get hung up on this backpressure thing, yet few seem to remember there's this big restriction in the intake called a throttle... if it's not WFO, backpressure isn't what's holding you back. If it _IS_ WFO, then you want the turbo to be spooling up as fast as possible, meaning no extra mass from something like a clutch.

KJ-TypeR

Another common misconception is that a Supercharger is better than a Turbo.

The reality is that a Turbo is more efficient than a Supercharger.

A Supercharger uses engine power to help itself make power.

In other words, since the Supercharger is run by a pulley on the engine, the Supercharger creates parasitic drag on the engine. The engine has to use part of it's power to spin the turbine in the Supercharger. This is very inefficient. As an example, for every 1hp the Supercharger makes, the engine wasted 0.5hp to help make it. The net result? 1hp - 0.5hp = 0.5hp.

On the other hand, a Turbocharger uses exhaust gases to spin the turbine (instead of a pulley on an engine). Exhaust gases are on their way out of the engine anyway, so there is a minimal loss in efficiency. In reality, most turbo's are fully spooled up by 3000 rpms, so if you are flooring it at 3000+ rpm's, you will notice NO LAG at all.

If a Turbo is small enough, there will be no lag even at low rpms (<3000 rpms).

The net result for a Turbocharger is this...1hp made by the Turbo = 1hp net, since the turbo isn't robbing any engine power to make power.

VoyagerDude

Is this really true?

WyattEarp

For the efficiency part absolutely yes. The problem usually is that Turbocharged engines are slightly more difficult to design (blowout valve, wastegate, turbine vs compressor size) and the Turbo itself is more prone to failure (oil cooling, Turbo bearings).

Spyke

I wish I could remember the numbers... but I think the blowers on top fuel cars use an even higher percentage than that.

As for saying a turbo is better than a roots blower, or vice versa, you'd have to define "better". Either one can be made to look better depending on the criteria.

I prefer positive displacement superchargers over turbos myself...

avlis

The solution is to replace turbos and superchargers with enormous compressed air tanks. That way you get the higher compression without any parasitic drag. You'll just have to fill the tank up every 1/4 mile.

There was a dragster that was built before I was born that did exactly that. Of course, it was only designed to go 1/4 mile at a time. Anyone familiar with this car? It's in the Garlits(sp) drag racing museum.

I think they realized they could do the same thing with nitrous oxide and use a much smaller tank?

KJ-TypeR

But NOS is better than that.

Too much air, and not enough gas causes the car to run lean which is VERY dangerous.

NOS is NO2.

1 part Nitrogen and 2 parts of Oxygen.

The Nitrogen acts as a buffer so the combustion is slower and controlled. As most of you know, pure oxygen ignites easily and can explode if heated enough. This is why the Nitrogen is there to buffer the reaction.

Cryptnotic

I thought NOS was 1 Nitrogen, 1 Oxygen, and 1 Sulphur.

I heard they put the sulphur in to keep kids from filling baloons with the stuff and inhaling it.

Lynn

NOS stands for Nitrous Oxide Systems, Inc.
http://www.holley.com/HiOctn/ProdLine/Products/NOS/

It is also used generically to mean any nitrous oxide system.

The actual molecule is one nitrogen atom and two oxygen atoms. If sulphur were added, the EPA would be all over it to get is banned, because sulphur oxides are a major component of smog.