# Supercharger V Turbo



## Guest (Jul 11, 2003)

I was wondering what would generally be better in a car, Super or Turbo? I am new to this so please don't flame me. 

a) Which one is less damaging to your engne?
b)Which is more efficient?
c)Which is more bang for my buck? 

Also I heard that superchargers last forever and turbos don't. I am sure that there is something wrong with that statement can some one please clarify? I am brand new to the car scene please have some patience with my ignorence. Thanks


----------



## Murph (Aug 8, 2002)

search...

both put extra stress on your engine
turbo is more efficient
bang for buck is relative.

take time to search this stuff and learn it.


----------



## Adam (Apr 30, 2002)

a)both
b)turbo
c)turbo, S/C's are pretty damn expensive


----------



## olsaltybastard (May 11, 2003)

It pretty much comes down to what you like more. I am a SC fan, not that turbos aren't worthwhile. I like the whine a SC makes at idle. If you start from scratch, a SC may be a little easier to install, due to less fabrication required. You will still need to fab things, so if you aren't good at this, a kit is your best bet.


----------



## Nizmodore (May 9, 2003)

Turbos is not more efficient at all......

A supercharger does indeed require power to drive it. The power required is actually mass airflow times boost. You also need to include the extra power required due to efficieny losses in the blower caused by heating of the air above that which occurs because of compression. Also belt drive losses need to be taken into account.

If you do the maths you will probably find between ten and twenty percent of crankshaft power is lost driving the blower in a typical modern street engine.

Now a turbo also requires power to drive it. The power developed by the exhaust turbine is once again mass airflow times boost, plus efficiency losses, plus bearing losses. If your supercharger has 70% adiabatic efficiency, and your turbo runs at about 70% adiabatic efficiency then the actual shaft horsepower required is going to be identical !

But to drive the exhaust turbine there must be a pressure drop across the exhaust housing and turbine wheel. This is basic thermodynamics. you cannot get power out of something without putting power in.

If you have ever measured the pressure drop across the exhaust turbine you will find it will be typically betwwen twice boost pressure, down to the same as boost pressure if you are really lucky.

But how does this extra back pressure in the exhaust manifold effect engine power ? Well again research has been done into this and the results have been published.

Typically an engine looses 1% of crankshaft power for each psi of back pressure in the exhaust manifold. Surprise ! ! you are going to lose about ten to twenty percent of crankshaft power to drive your turbo, exactly the same as that required to drive a supercharger.

Ah but if you loose 1% of power per psi that means at 100psi back pressure you would have no power at all ? Yes indeed.

When the exhaust valve opens there may be roughly about 100psi left in the combustion chamber trying to get out. If there is no exhaust flow, the engine will stop. Hence zero output power.

The myth that superchargers draw power from the crank, and turbos are free power for nothing is just that, a myth.

(thx Warpspeed)

With my engine (RB30ET) I'm building a system with both a turbo and blower (Blower is a SC14 off a Toyota Crown @ 9psi).....No turbo lag and great topend power  Anyway my Supercharger cost me $350 Aus (about $160 US) so they are not expensive at all. Now for you smaller 2L engines a SC14 is a bit large, maybe a cheaper blower off a Suburu or sumthing would be better (seen one @ 10psi on a SR20DE) anyway these blowers are cheaper @ $175 AUS.....good stuff


----------



## chimmike (Oct 17, 2002)

Munchmild said:


> *I was wondering what would generally be better in a car, Super or Turbo? I am new to this so please don't flame me.
> 
> a) Which one is less damaging to your engne?
> b)Which is more efficient?
> ...


a) if not done right, they are both damaging to your engine.
b) In most aspects, turbo is most efficient, and this has been proven.
c) turbo is more bang for the buck. A lot easier to up the boost than s/c (so long as fuel system is comensated as well, for both turbo and s/c)

Superchargers AND turbos can last forever if taken care of like they should be. 

and it really all depends on what kind of car you're talking about when deciding between turbo and s/c. if I had a Z28, I'd want a supercharger more than turbo..............................but my sentra, I want turbo because my top end is teh suck. Lag is pretty negligible in our cars unless you're running a big t3/t04e at high boost (but you'll make over 300whp normally, too. lol)


----------



## Nizmodore (May 9, 2003)

How has this been proven?


----------



## chimmike (Oct 17, 2002)

read other posts that have discussed this.


----------



## javierb14 (Jul 9, 2002)

right, turbos require energy to work.....heat, pressure, and flow from the exhaust gas have these energies. a turbine uses these normally "wasted" energies. in that sense it could be considered more efficient. it has also been tested that approximately 1/3 of the combustion heat energy is lost in the exhaust gas stream...why not use it?

and backpressure within the exhaust mani can be related to turbine size and ar. small turbine means high backpressure and large means less:

for example:
T25 high backpressure....quick response....good light to light turbo
T4 lower backpressure.....less response....great top end

but ive also seen 2* the pressure in the exhaust mani as the IM at full boost and WOT.....not all the time though

and its a *fact* that the power loss of a turbocharged engine by means of the turbine driving the compressor is far less than using a supercharger with a belt driving the compressor. pick up any engineering book dealing with FI.

then u can also get into the topic of charge temps with turbo vs supercharger....then lag (not all sc's are instant boost)....then ability to intercool blah blah blah.


----------



## Nizmodore (May 9, 2003)

true, also depens what type of SC you use, eg roots, whipple etc. The Whipple is the king of forced induction however....


----------



## javierb14 (Jul 9, 2002)

eh....have u ever compared dyno's of superchargers vs turbos for the same engine configurations? the right turbo is hard to beat


----------

