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Discussion Starter · #1 ·
i have an itch for how they work , , , is it possible to make a turbo work driven by a belt? . . .
 

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No, because it would be a supercharger not a turbocharger if it was driven by a belt. Maybe I'm missing something here :?
 

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Discussion Starter · #3 ·
I think the cuestion should be , why a turbo is driven by exhaust . . .and a supercharger by a belt . . is it the only difference between . . . the way they're driven ???

the idea is to get more air to the intake . . . as i see both systems do it, one is belt and other exhaust . . .

lets say that I have a turbo ( dont really know where it came from, says holster or something like that on it ) and I want to use it somehow . . . could I just belt drive it . . . ?

I also have the intercooler and some ducts . . . is there anyway I can use them in my MKII ??
 

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Turbos are effectively "free" power, in the sense that they create no physical drag on the engine. The exhaust gases are what drive the turbo. The drawback here is that since you're not mechanically driving the turbo, you don't have instant boost. You can see this in a dyno chart where the power sharply rises while the turbo spools, and then once full boost is reached follows a normal power curve. Smaller turbos minimize the delay time between pushing the pedal and the giddyup, but also just produce less giddyup. :?

A supercharger is belt driven off an accessory pully. This means you add a physical mass the engine has to drive, which to me simply means a supercharger will deliver a bit less power per pound of boost. BUT, since it's mechanically driven, a positive displacement type supercharger delivers full boost throughout the entire RPM band (dyno chart from supercharged camaro) Ignore the numbers and look at the curve

Superchargers tend to be more difficult to mount due to needing access to a pulley. Also, most superchargers I see don't utilize an aftercooler, so efficiency is decreased. Personally, I prefer a supercharger because I like the linear power curve...I can hit the gas coming out of a turn w/o worrying about when the power might come on suddenly breaking the ass end loose, and as such can drive more aggressively. SC's are just too expensive for my pocket due to all the fabrication required (nothing pre-existing for our cars).

Added note: On the whole, superchargers just aren't as efficient as a turbo, and so more heat is developed. As such, more boost can be run with a turbo with less risk of detonation. If big power is the goal, then the turbo is the best option.

And one more, a good link to more info:
http://speedoptions.com/articles/3682/
 

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CT26's are cheap, take the guess-work out and easily turbo your car. Check the FAQ for more ideas on making your 5m-ge a 5m-gTe.

Now, If you really really want to use that turbo you have, you will want to take some measurements to see how it will perform on a 2.8L motor. You will want to see the entry diameter and overall diameter of the compressor wheel as well as the exhaust turbine. Also you will want the inlet and outlet diameters of both sides. Also (sounding like a broken record here) you will want to make sure the compressor outlet points in the same direction as the exhaust inlet due to limited mounting room.

There are pretty much two types of superchargers. One, the standard old-school bigblock blower. It has two rounded-triangles that move against eachother (similar to our oil pumps) and force air out the other side. The second type looks like the compressor side of a turbo with a gearbox behind it and a pulley sticking out the back. This type is becoming ever more popular for many reasons.

Couple things to keep in mind, most low end superchargers do not have wastegates. Infact, I dont know that I have heard of any superchargers with wastegates. The drive is linear, for example, (numbers may be b.s.) if at 3000rpm, your supercharger spins 30,000rpm, it will spin 60,000rpm at 6,000rpm. That means you will only build full boost at full rpm. If you want full boost at 3000rpm, you will be making too much at 6000rpm. Nice thing about turbos, it can full boost all the way from 2,500rpm to redline, no pulleys to change or whatnot.

Uhm, superchargers are silly.
Turbos are yummy.

http://webpages.charter.net/wackskier/turrrboooo.jpg

--BillyM
 

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atdsupra said:
I think the cuestion should be , why a turbo is driven by exhaust . . .and a supercharger by a belt . . is it the only difference between . . . the way they're driven ???
Yes,

turbo= compressor driven by the exhaust gas
supercharger(blowers)= compressor driven mechanically by a belt(usually) of the crankshaft

There are two main types of superchargers. Centrifugal which is like a one sided turbo and a Roots type which looks nothing like one. Its not like you can easily take a turbo and use it as the other supercharger. The compressor wheels in turbo and supercharger are usually much different sizes. Turbos spin really fast and hence use a smaller compressor wheel (generally) while centrifugal superchargers usually have a much bigger compressor because they spin slower. Check out the following site for the basics on turbos and blowers.

http://auto.howstuffworks.com/turbo.htm

http://auto.howstuffworks.com/question122.htm

You're really thinking too hard about this. Turbos are very easy to install on MkII. Check here for an install guide;

http://geocities.com/aarongarney/5mgte.html

HTH
 

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The full boost only at redline does apply to a centrifugal type SC, where the boost rises as the square of its driven speed. The positive displacement type generates full boost all the time.

This clip explains better than I can:
"What this means is you set the pulley ratio for whatever max boost your require. Because the positive displacement supercharger delivers airflow linearly (like an engine) it will maintain full boost throughout the rev band. At 3250 rpm you would have 8psi and you will also have 8 psi at 6500 rpm. In theory you should have full boost at idle but it doesn't actually work that way because of air leakage around the rotors inside the blower when it is turning at very low RPM. Still on my car I get 2psi of boost at 1k rpm. Almost the amount of boost a centrifugal (with the same max boost level) would produce at more the 3x the engine speed."
 

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Heres a suggestion for ya. Hea ddown to the local Bookstore and order this Book:

"Maximum Boost" written by Corky Bell.

Its the bible of forced induction. Read thru the first two chapters to get a feel for the basics, and most of what these guys have said will make tons more sense...


But, in a nutshell, on a very VERY basic level, yes, the only difference between a supercharger and a turbo is the source of the compressor wheels power. The reason one is driven by exhaust and the other is by a belt.. simply put... is for different applications. Sometimes the fact that boost isn't limited by engine RPM means that a turbo is more appropiate... while other times, the instant boost response of a Supercharger is more whats called for.

As for which is better... :confused: each has a strong and weak point.
 

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Supercharger/Turbo

I like to think of the the Supercharger as a great street weapon :evil: Fast response and less lag than a turbo. Might beat the turbo opponent in the streets do to faster response 8)

But a turbo is so much easier to manage and I think more potential in everything except the turbo lag :twisted:

But I have seen like a year ago in SuperStreet and SCC an Integra thats both Super & Turbo charged. As well as an MR2 w/4AGZTE :shock: Imagine that, both fast response and topend power 8) :twisted:
 

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Turbos are effectively "free" power, in the sense that they create no physical drag on the engine. The exhaust gases are what drive the turbo.
The power required to compress the intake air comes from nowhere?
If only it were true. How about additional exhaust back pressure that the engine has to overcome.
 

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Re: Supercharger/Turbo

DannyG said:
I like to think of the the Supercharger as a great street weapon :evil: Fast response and less lag than a turbo. Might beat the turbo opponent in the streets do to faster response 8)

But a turbo is so much easier to manage and I think more potential in everything except the turbo lag :twisted:

But I have seen like a year ago in SuperStreet and SCC an Integra thats both Super & Turbo charged. As well as an MR2 w/4AGZTE :shock: Imagine that, both fast response and topend power 8) :twisted:

superchargers are better on high output engines that can afford the parasitic loss more easily.
ever driven/ridden in a supercharged genIV camaro or firebird?
youll know what i mean, they FLY, and they seem much faster than a similar output turbo camaro, although the turbo is usually just as fast or faster.

turbos do add backpressure, but its miniscule...a couple percent (1-5% iirc), compared with the 5-10% loss thats been seen in dyno tests of supercharged vehicles.


superchargers are great, in their place, but for a smaller engine, turbos are more generally more efficient.
 

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The power required to compress the intake air comes from nowhere?
If only it were true. How about additional exhaust back pressure that the engine has to overcome
of course the power comes from somewhere, but the bulk of it does not come from "backpressure" that the engine has to overcome. engine exhaust gases for a naturally aspirated motor as well exit combustion at high temperature and high pressure (and high enthalpy). as the gases goes out the exhaust piping, they will expand and give off heat and end up at a low enthalpy state, whether there's a turbine in its way or not. the turbine is just something that creates power from the expansion of the hot exhaust gases to lower pressure. without a turbine, there would just be a drop in enthalpy of a lot of gas with no useful work done. so it really is "free" power.

the presence of a diffuser, exhaust housing and turbine wheel are not parasitic in nature. your point of the backpressure is valid in that they can reduce engine power by creating more pumping losses and lower VE cause of reversion and stuff but that change in engine power due to the restriction in the exhaust is definitely not where the power to compress intake air comes from.

sorry, you probably knew all that, but the statement really implied that the loss in engine power is what compressed the intake air. i remember being confused about stuff like that before i read about turbos and wanted to make sure that didn't happen to ne1 else

shiva
 

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Discussion Starter · #14 ·
wow :shock: , pretty much informative and looks like you already gone thru this . . .
I'll have to read a lot now . . .

where can I get a ct26 (somebody mentioned as "cheap") and all required to go turbo ?

thanks to all for the info . . . if possible, keep it coming :D
 

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the presence of a diffuser, exhaust housing and turbine wheel are not parasitic in nature. your point of the backpressure is valid in that they can reduce engine power by creating more pumping losses and lower VE cause of reversion and stuff but that change in engine power due to the restriction in the exhaust is definitely not where the power to compress intake air comes from.
The turbo takes energy (enthalpy ~ heat + pressure, for anyone not familier with the term) from the exhaust stream which leaves less energy
to blow the exhaust into the atmospheric pressure, thus back pressure. It would be nice if someone knew of BSFC comparative curves for the same mechanical engine (and a/f ratio) with a supercharger and then with a turbo intake. Then we could see the difference.
 

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The turbo takes energy (enthalpy ~ heat + pressure, for anyone not familier with the term) from the exhaust stream which leaves less energy
to blow the exhaust into the atmospheric pressure, thus back pressure.
stan are you sure about this? going from high enthalpy (post combustion, right out of the cyl) to low enthalpy (lower temp and atmo out the tailpipe) doesn't require work...

but yes, there will be backpressure with a turbocharged motor.

It would be nice if someone knew of BSFC comparative curves for the same mechanical engine (and a/f ratio) with a supercharger and then with a turbo intake. Then we could see the difference.
that would be interesting to see. but whatever the difference may be, it still doesn't mean that the backpressure is what is responsible for spinning the turbine, though the inverse of that statement is true.


atdsupra: i'd suggest that you don't immediately settle for a turbo off ebay unless you are really comfortable with the description of it. i'd check supraforums.com or supramania.com or i-supra.com first. chances of getting one with a known history for less money are much higher.

but if you are itnerested in a turbo'd motor in your car, search, read threads in hte 5/6/7m-gte section, check out some of the member web sites off http://www.celicasupra.com/memberbyyear.htm. be sure to check aaron garney's and phil dupler's site while you are there. also check out some of the 7m-gte sites, like Andy's and Jim's. check out rabidchimp.com.

shiva
 

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We're prolly the only 2 reading the thread by this time. A "simple" way
to "measure the difference is to dyno (or drive) a na car. Then install a
turbo in the exhaust stream but still run the car with it's na intake. Let
the compressor empty into a small manifold (metal box) with a short constricting exit pipe (or hole) as the manifolds outlet so the compressor "thinks" it's seeing an engine intake (adjust the exit pipe or hole dia so mani pressure builds up to say 5psig at a given flow rate, say 300 CFM which corresponds to approx 270hp on an na engine). Now re-dyno(drive) the car to see the power difference if any.

haven't had time to sort out the problem but most of the compressor power could be coming from the hi temp (internal energy) of the exhaust as u say.
 

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going from high enthalpy (post combustion, right out of the cyl) to low enthalpy (lower temp and atmo out the tailpipe) doesn't require work...
Peeps wrap na headers and catback to get more power. don't they?
i thought it was energy required to blow into exhaust atmosphere.
 
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