What spins a turbocharger?

[TomFraser]

Some people are arguing that if cold air instead of exhaust was used to spin a turbocharger it would be beneficial as the cold air is more dense.

Others argue that the energy of hot air is better for spinning a compressor wheel, and give examples such as turbos mounted on top of engines spinning better simply by insulating the pipe going from the exhaust to the turbo.

Others argue that air is air and it does not matter.

This Link is a page of arguments posted by people.

I have no opinion on the subject as I am not well educated on it, however I am wondering if some people here have an opinion either way?

 

[A. Jay]

Air travels from hot to cold, the bigger the difference the faster it'll do it. Also, lower density air is easier to push. It's true that colder exhaust still works (diesels, remote turbos), but what are they suggesting, that you cool the exhaust down? Lmao

- from my Archos 5 IT

 

[te72]

Water/methanol injection cools down EGT's and intake temperatures as well, but not sure it has any measurable or appreciable effects on how fast a turbo spools up...

 

[digihonk82]

seems like the article in the link is about an unrelated scientific principal of heat transfer and the people aren't talking about turbos.

 

[tjzyx]

I found the Corvair example pretty funny. If you cool the exhaust before it enters the turbo you will lower the volume of exhaust moving through the turbo. Obviously the lower volume will not spin the turbo as fast. I don't see how this is related to the argument. you are lowering the volume and the heat. If you could achieve the same flow rate with cold air you would have the same result. What the entire argument is ignoring is that the function of the heat is to increase the flow rate. It would require more pressure applied to the turbine inlet to achieve the same flow rate because you would not have the temperature difference helping flow.

 

[hvyman]

Pressure produces heat. Its always going to have heat. Its what inter coolers are for.

Water meth kit is great for this purpose or even ic sprayers.

Also could always use nos.

 

[SupraMario]

That physic's shit they tell you is a big lie.

 

[bioskyline]

That physic's shit they tell you is a big lie.

LOL awesome pic. that explains my lag problem, hes just to old to run that fast

but i dunno, hot, cold ive never noticed a difference in turbo performance, other than hitting fuel cut early from driving in sub zero temps.

colder turbine housing temps may increase turbo life, but not perfomance.

 

[TomFraser]

The temperature of the intake side of the turbo is not what is in question... it's the exhaust side of the turbo that people are arguing about...

 

[Poodles]

It's an idiotic and pointless arguement. If you're cooling the exhaust before it enters the turbine, you're going to loose velocity through and induce lag because of the extra piping (hence why rear mount turbos suck). Removal of the heat reduces the pressure and lowers velocity. Heat = energy

 

[flight doc89]

Exhaust gasses moving at high velocity spin the turbocharger.
When you lose heat from that gas before it reaches the turbo, you are losing energy, energy that would have been spinning the turbine and thus driving the compressor.

but i dunno, hot, cold ive never noticed a difference in turbo performance, other than hitting fuel cut early from driving in sub zero temps.

That has nothing to do with EGT. That is because - if pressure remains constant - colder air is more dense than warmer air. The airflow meter detects that too much air is entering the engine, and it cuts the fuel before the injectors max out.

 

[91Supra313]

That physic's shit they tell you is a big lie.

DAMN IT MARIO!!!!!!!!!!!! As soon as I saw the title of the thread I was going to do this exact same shit. lmao. I couldn't help myself on it, and so I decided to look in here and see if someone had beaten me to the punch. Low and behold.....someone did....DAMN IT.......... good one though.

 

[GrimJack]

Folks get into this 'turbo' debate all the time, and the fact is what they are bringing up is theoretical, first of all, and secondly not really germane to the actual reasons why turbos work so well.

The reason turbos work is because they use exhaust flow to compress intake air. More importantly, the volume of exhaust coming out of an engine is MUCH larger than the volume of air going in, by virtue of the fuel being added that comes in as liquid and leaves as a gas. As we all know, a small amount of liquid creates a very large amount of gas.

If we could replace the hot exhaust with another gas, that was much cooler, but still moved at the same velocity / volume as the exhaust, then yes, it should theoretically spool a turbo faster. I say theoretically because it's simply not possible to achieve without working in a lab with a lot of bulky, heavy equipment that wouldn't fit in a car. Furthermore, due to the increased volume due to density at lower temps, you would lose on the top end, as the point where the exhaust housing topped out in flow would be sooner.

Bottom line - it's a pointless debate, don't get sucked into it looking for effective real world applications.

 

[SupraMario]

DAMN IT MARIO!!!!!!!!!!!! As soon as I saw the title of the thread I was going to do this exact same shit. lmao. I couldn't help myself on it, and so I decided to look in here and see if someone had beaten me to the punch. Low and behold.....someone did....DAMN IT.......... good one though.

Ninja masta!

This thread is pretty pointless, as it has been stated countless times, heat = energy. It seems most of these questions stem from people who never open a book or read anything about thermodynamics. :/

 

[te72]

I'll just leave this here...

[video=youtube;YupwgBpiOn4]http://www.youtube.com/watch?v=YupwgBpiOn4[/video]

 

[hvyman]

^ his bov was sick. I want!!