Whats the difference between a turbocharger and a supercharger? How much would you expect to pay for them (new and used)? How much of a gain would they give me in a 305 TBI?

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1992 Pontiac Firebird
- 5.0L V8 TBI
- Automatic Trans

 

If you mean operating differences it's simple. A turbocharger takes exhaust pressure and adds it right back into your intake, thus not really taking anything from the engine except for engine "waste." A supercharger runs off your belt system and blows air into your intake, thus "Blower." IMO, I like turbo better because it does not run off of your pulley system. Also, with a turbo, the boost has time to build up when you take off. Kinda like it doesn't turn on until you're already going. Supercharger is basically always on. It's always putting some boost on your engine because the pulley is constantly turning.
If I'm wrong, I'm more than willing to be corrected. I admit that I am not the most knowledgeable person when it comes to power adders.

Price-wise, I know nothing.

Installation wise-supercharger would be the way to go. There's kits that install in under 6 hours, and are fairly simple to do. Turbo's are a little harder and require special headers to accommodate them, and other lil things that are a b*tch to put in.

 

Little quote for you (jump in flame suit): "There's 2 kinds of people who run Power Adders....those who've rebuilt their engine, and those that are planning to!"

 

BTW, I'm throwing this question in here along with yours.

With a turbo, after you run it hard, you're supposed to let it run for 5 minutes before you turn it off. Is the same true for a supercharger?

 

the reason you run it for 5 minutes is to allow it to cool with oil still flowing through it. I don't think you have to do this for a supercharger because they probobly run much cooler since they don't have 1000 degree exhaust going through them, but i may be wrong.

 

A supercharger is driven by a belt off an engine accessory. A turbocharger is driven by the flow of exhaust from your engine.

Superchargers come in many different styles that use different methods of creating boost pressure. The typical style used for late model cars is the centrifugal style like Vortech, ATI, and others. These are not positive discplacement superchargers like the roots blowers and screw compressors. They have a centrifugal compressor in them that creates boost pressure relative to engine speed. In other words, the faster you turn your engine the more boost they make (up to a point). If you see a kit that makes 8 psi of boost you will only make that boost near redline right before you shift. The rest of the time it will be making moderate to no boost at all.

A turbocharger does have turbo lag because it takes time for the exhaust sytsem to develop enough flow to make the turbos work well. However, this doesn't take long at all and the whole turbo lag issue is far overrated. In addition, a turbocharger will make full boost much sooner then a supercharger and you will be able to accelerate under full boost for several thousand rpms. This alone will make a turbocharged car quicker and more powerful then a centrifugally supercharged car. But the other thing that helps is many turbo designs are more efficient then superchargers and will allow you to make more boost pressure without detonation then allowable with a supercharger. Again, this is more power. The drawback is you have to use a snake den of exhaust tubing to have a turbo on your car. The packaging can be a real issue.

As far as reliability goes that is a non-issue as long as you work within the parameters of what your engine can handle. Of course, like anything else a purpose built engine will be more durable and last longer.

 

I would say no...

The "run it 5 minutes" is to allow oil to circulate and cool the turbo housing. Since the superchargers aren't exhaust-driven, they don't get nearly as hot as a turbocharger does.

 

Another thing about the "cool down" period for Turbos.... As this is a quite simply, a small turbine engine, the turbine needs time to "spin down". It is turning at some ourtrageous RPM, and the idea of letting your engine idle for a few minutes before shutting down is to give the turbine time to slow down while still getting oil. Otherwise, the turbo will simply keep on a-goin', coke the oil that is just sitting there, and score the shaft and bearings.... Not good.

 

Okay, so the pressure of the exhaust gases coming out of the engine is what turns the turbo? Can anybody tell me what kind of velocity those exhaust gases are moving at and when the turbo spools up, what kind of RPM's is it pushing?

 

Actually the exhaust flow doesn't turn the turbo, it's the expansion of the exhaust gases that turns the turbo.
The size of the turbo, the way the exhaust is routed to the turbo, and any restriction in the engine air flow all effect turbo spool up times, most turbo's spin at very fast rpm's, somethin' like 30,000 rpm's.
later
larry

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MÅN¡ÅÇ ©
88 IROC 5.7L,edelbrock TES,random tech cat,borla exhaust,chip,sfc,accel wires,airfoil,k&n's,ETC..
and NOW supercharged!!!
http://maniac.megamania.com

 

Centrifugal superchargers generally max out around 30,000 rpm. Turbos commonly turn at 80,000 rpm.

If you took apart a turbo you would notice there are two seperate sides connected to the same shaft. One side has an impeller that uses exhaust gas to spin the turbo and the other side of the shaft has an impeller that is creating the boost to your engine. One side processes exhaust to power the turbo and the other side processes the air to provide air to your engine.

 

Okay. Thanks guys. Just one more question then I'm done, lol. Those cars I sometimes see at drag strips with the twin turbo hoods . . . the turbos are exposed to the open air right? Does exhaust gases still turn these too?

 

By definition, yes. As I explained before all turbos are driven or powered from exhaust gas flow. This then drives the impeller that feeds outside air to your motor. If it's not driven by exhaust gas flow then it's not a turbo.

 

One of the past few HOT ROD mag's had a decent turbo article. At least for a turbo ignorant guy like me.

 

I dunno about turbos.. but cent. S/C's (from ATI) turn up to 65k, others, such as paxton, only go to around 50k, limiting your max engine rpm to a much lower number. (big ATI fan, dont have one, but hopefully soon...)

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• 83 Z28--ttops, 200k miles--very ragged out. sold, thank goodness
• 74 Z28--slightly modded 383, TH400 tranny, not too quick but fun to drive