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Probably a dumb question but I was wondering...


Guest tony78_280z

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Guest tony78_280z

If you took a turbo and mounted it up someplace near the alternator and put a belt on it would it run like a supercharger? I'm sure it'd need to be balanced in some way but someone has had to fabricated something bizare like this.

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Guest crazycustom240z

You couldn't get enough revolutions to get it work right and you would have to make some kind of crazy pulley adapter. I think it would be a great waste of time. better off getting some kind of supercharger. they pump more air than a belt driven turbo.

 

sorry man

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I can't see doing this with a turbo... but there are plenty of superchargers out there that do exactly what you're talking about (I'm assuming you know this, though)

 

 

I prefer turbo because once it reaches efficiency, your boost controller keeps it at it's efficiency point until you're done using it.

 

Sure, the supercharger would be nice to get that immediate boost, but the way the boost rises and drops in each gear irritates me.

 

A properly tuned turbo motor is taking advantage of everything the turbo can give it all the time after it spools. (great for drag racing, since you just two-step it to spool off the line :-P )

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Tony, if you had clicked the links above, you would have seen this:

In order to achieve this boost, the turbocharger uses the exhaust flow from the engine to spin a turbine, which in turn spins an air pump. The turbine in the turbocharger spins at speeds of up to 150,000 rotations per minute (rpm) -- that's about 30 times faster than most car engines can go.

 

Please re-read that quote a few times. Not to mention, that you would have a useless exaust side of a turbo. Please read those links I posted. For the amount of work it would take to get the turbo geared up to speed, you would be better off just using the turbo where it was meant to be. Superchargers have a parasidic loss of power (running off the crank), it's like running the A/C all the time, but they have almost instant response, which a turbo does not.

 

!M!

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That would be going backwards actually. Turbos are free horsepower' date=' they work off spent exaust. You need to read up a bit. Go here:

How a turbo works

What is the difference between a turbocharger and a supercharger on a car's engine?

 

!M!

 

its not totally free power as that would defy the laws of physics and whatever but its damn close. they are way more efficient than all other forms of forced induction out right now.

 

reason why this wouldn't work too well is simple... a turbo spins in excess of 100,000 rpm. a roots supercharger that uses the same basic turbo compressor design spins a maximum of about 40,000 rpm. this is because the wheel was designed to push the high amount of boost at that speed compared to the turbo which is designed to create the boost at does at the very high speeds it does.

 

lets say for instance you have an engine that will spin to 10,000 rpm. to get a pulley setup that would spin the turbo's compressor wheel at the 100,000+ rpm needed the pulleys would need to be something like this:

 

Crank pulley - 10 inches

Turbo pulley - 1 inch

 

Or to minimize the size

Crank pulley - 5 inches

Turbo pulley - .5 inches

 

this would land you 100,000 rpm compressor speed at 10,000 rpm engine speed. now... lets make it more realistic.

 

6,000 rpm redline

Crank pulley - 10 inches

Turbo pulley - .6 inches

 

Crank pulley - 5 inches

Turbo pulley - ~.3 inches

 

If you were at 3,000 rpm with this setup the compressor would be spinning at half the speed, 50,000 rpm which most likely is either not producing much boost or is out of the turbo's efficiency range.

 

Basically that's the reason why that wouldn't work out too well (considering a .5 inch or even a 1 inch pulley would most likely be hard to come by and even make work as would a 10 inch pulley on the crank... ouch).

 

(i'm pretty sure i got the pulley calculations right, someone please correct me if i'm wrong)

 

Now... the reason why you 'wouldn't' want to do this is because:

 

1. a belt driven compressor is inefficient compared to an exhaust driven compressor. its been proven that s/c's take quite a bit of power from the engine to run. for instance... they estimate up to a 500 hp loss on very high hp drag cars. (its too bad turbos aren't allowed in those races... that'd prove to everyone that turbos are better... ******* idiots paying people off to keep turbos out so they don't lose s/c sales most likely icon8.gif)

2. boost isn't attained till redline (centrifugal) or boost tends to drop off nearing redline (roots)

3. centrifugal s/c's still have a sort of lag... they basically don't produce boost instantly. a roots does... however due to their nature they aren't made to boost very high and are pretty hard to cool (the air charge)

 

in the end, a good ol' regular turbo setup can't be beat. if i remember correctly a magazine (hot rod or something like that) did a test with a mustang using a roots, centrifugal, and a turbo setup on it. they didn't change anything between the tests at all except for the type of forced induction and everytime the turbo came out on top.

 

more reasons they're better... older f1 cars used to use turbo's and it is estimated they pulled about 1,500 hp... ... ... out of a 1.5 liter engine! makes you wonder what one would do on a funny car... :D

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