Turbo Vs Super...

[Nd4SpdSe]

This isnt really an Mx-3 Turbo vs Super Charger thread, its just about them in general

Me and a co-worker we just talking about Turbo vs Super Charges, and i was wonder why most people do turbo and not a supercharger. (Correct me if in wrong at any pont, my forced induction knowledge is limited). I know superchargers output power more linear than a turbo, which is why i woudl think it would be a better choice..but most people on the quest for more power seem to turbo rather than supercharge their engines. Is there a limiting factor on about superchargers that im not awair of that make turbos a better option?

[Spydie]

this is my understanding anyway.
Superchargers create power similar to a turbo. A fan compresses air and forces it into the intake.
SC uses a belt and pully system to run. As the engine turns the belt turns the pully which in turn drives the SC. This wastes energy because some of the engines stock HP now has to turn the SC instead of going to the wheels. so it takes energy to make energy. The boost is felt instantly. the SC will spin as fast as the engine will turn.
A turbo on the other hand uses exhaust gas to spin an impeller which spins the fan, which compresses the air and forces it into the intake.
Since it works off of exhaust gas there is no "parisitic energy loss" so you keep the stock hp to the ground as well the boost. This means it's more efficient. Boost takes a tad longer to achieve because the fan requires a brief moment to reach speed from the exhaust. So the waste is sorta reused to make boost.
'Some' superchargers (like the vortech) are bolt ons and can be installed with hand tools in a day or less. Turbos generally require some welding.

[Nd4SpdSe]

but wouldnt the turbo add restricton to the exaust, decreasing power, adding a load to the engine as a supercharger would, but in a different way?

[OsoSlo z28]

the only time the turbo proves to be a restriction is if the wrong housing/turbine combo is used for the intended purpose. (ie, .48 t25 housing/stage 1 wheel on a single turbo supra) this creates reversion which is when the exhaust gas creates so much backpressure, it's forced back into the combustion chamber.

the supercharger is less effecient in more ways than one. main factor is that it uses engery to make energy. second, is that it creates a higher air charger temp which robs you of potential power. the positives of a s/c are instant boost, and simplicity.

[mx3frik]

The pressure does built up on the exhaust side of the turbo, that's the only way the turbine could be driven. That's why wastegates are needed so that when a certain threashold is reached it'll let some of the pressure out, then reversion would be less of an issue if at all.

Keep in mind supercharged air can be intercooled too if desired to keep the temperature down.

In some cases supercharger is desired since turbo charged cars suffer a short period of time between the driver stomping on the gas and exhaust pressure to build up to turn the turbine fast enough to create usable boost. This lag is known as turbo lag (go figure) and this is one area where supercharger has the advantage. So in spirited driving (a lot of "jabbing the padel", turns, auto-x, drifting, even gear shift etc) a car equipped with a supercharger might be more suitable for the situation.

To counter the effect of turbo lag rally cars are equipped with what's known as the anti-lag or misfirging system where (explaining using simplified model) a spark plug is added into the exhuast manifold, when the driver lets of to gas to shift gera that plug will fire making the manifold a temp. combustion chamber keeping the exhaust pressure up even when the engien slows down. What's the flame out of the exhaust and the popping noise you hear when you watch a rally race. The average life of turbo/exhaust components of this setup is around 5000km...

I could go on and on but I gotta get back to work....

BTW, whats' with the "MR." Ashley Fowler? inside joke?

Cheers,

Eugene

[jplar]

You mentioned a life of 5,000 km for turbo parts, but what about the expected life of a s/c? And do either of these setups reduce the life of the engine?

[Sonicxtacy02]

He was referring to that particular rally setup i believe. And turbo parts just as S/C parts can last the lifetime of the car depending on quality of parts used, management system and efficency of the system as a whole.

[OsoSlo z28]

i agree to a point. the wastegate's purpose is not to relieve built up exhaust pressure, but to bypass the turbo all-together to achieve a certain boost level. back-pressure is caused by the restriction of the turbine housing/wheel. the smaller the turbine housing, the faster the spool, but at higher rpm's, back-pressure will create higher temperatures and reduce power output. too small of a turbine housing could create reversion in the higher rpm scale. if you were to have an extremely large turbine housing on say the bp 1.8, then lag will be horrible, but next to no back-pressure will accure, therefore eliminating the chance of reveresion.

with a turbo and s/c setup having the same cooling system, the s/c would still create more heat due to the s/c design compared to the turbo's.

the part about anti-lag is a bit different from what i've seen/read. from what i understand, when the foot comes off the gas pedal, the ignition timing is backed down(retard) a considerable amount. also, the air/fuel mixture is richened along with the throttlebody plate staying partially open. with the timing retard, most of the exhaust gases are still unburnt, and the ignition spark occurs right when the exhaust valves are opening. with the spark and the high heat of the exhaust runners, the unburnt fuel is ignited right in the exhaust manifold...right next to the turbo. same principle as what you stated, minus the sparkplug in the manifod.

the "mr." part is because i'm a guy, and my name is ashley. i had WAY too many people thinking i was a girl

[Nd4SpdSe]

Originally posted by Eugene H.:
To counter the effect of turbo lag rally cars are equipped with what's known as the anti-lag or misfirging system where (explaining using simplified model) a spark plug is added into the exhuast manifold, when the driver lets of to gas to shift gera that plug will fire making the manifold a temp. combustion chamber keeping the exhaust pressure up even when the engien slows down. What's the flame out of the exhaust and the popping noise you hear when you watch a rally race. The average life of turbo/exhaust components of this setup is around 5000km....

AHHH! I understand now! I was watching Initial D and one guy driving a Lancer Evo was bragging about his mis-firing system...now i know why!

[mx3frik]

Thanks Mr. Ashely, what you said makes the name "misfirign system" more suitable. I think you're probably right.

I did look up the misfiring system a long long (can't stress that enough) time ago when I just started watching rally races (when it was like box-car racing) and when I looked it up I had to use yahoo translation on the only few pages I found on such system...I (I want to blame yahoo mostly I even got a mod chip so I can play the initial d game on ps2. Heard they're coming up w/ the 4th stage in 2k4?

Eugene

[Gkreator]

From what I'm undersanding at this point, the superchargers have a switch on your dash that you turn on before use. The Turbo's are always running. Am I correct Ashley?

[Sonicxtacy02]

Originally posted by Gkreator:
From what I'm undersanding at this point, the superchargers have a switch on your dash that you turn on before use. The Turbo's are always running. Am I correct Ashley?

Most certainly not, turbos and superchargers both run when the car runs. Either one is controllable with a boost controller, but neither has a feature where you can turn it on and off by a switch. That would be nitrous

[Spydie]

or the TKT electric SC. Not one of those ebay ones...this one is actually pretty cool. It is a MINI Eaton SC with 3 starter motors hooked up to it. starter motors spin VERY fast. You flip a swith hit WOT and you get a 15 sec burst before the battery drains. For track sprints.
Would I buy it? Hell NO!!!! but it's not absolutely terrible. the price is like the same as a real turbo or SC. works sorta like nitrous but you charge a battery rather than fill a bottle

[VizualXTC]

Originally posted by cre8v mx3:
the "mr." part is because i'm a guy, and my name is ashley. i had WAY too many people thinking i was a girl

You're not a girl? OMG!!! What's with all the love letters you've been sending me?

Oh, and if you install a turbo onto your car you are creating resistance. Even if the turbine is spinning fast enough that the gases don't have to push it anymore, it's still taking up room in the pipe forcing the gases to compress inside the piping. Also, you're putting a 90* angle in there also, which causes restriction. I agree that it is a very very little varience compared to the drag caused by a supercharger, but it is still there.

And the wastegate is not to reduce backpressure. It is used to route the exhaust past the turbo so that it's doesn't spin it too fast. If you didn't have one, you'd see boost at 1psi around 2500rpm, 10psi around 5000rpm and 30psi around 8000rpm. (not real numbers) The wastegate will see the boost on the intake side at 10psi, then will open to allow part of the exhaust gas to bypass the turbo so that the turbo spins a the right speed to keep the psi at 10.

The way to make more boost on a turbo is to make the wastegate open a little later in the powerband so that it will let the turbo spin faster. The way to up the boost on a supercharger is to change the pully that is attached to the charger.

[Spydie]

Originally posted by cre8v mx3:


the "mr." part is because i'm a guy, and my name is ashley. i had WAY too many people thinking i was a girl

AWWWW CRAP!!! guess I'll just give these flowers to my wife instead.