Lsos

I always read that heat and exhaust velocity are what drive a turbocharger (or any turbine). I can understand the exhaust velocity part, but what role does the heat play? Does it simply increase the pressure, or is there more to it than that?

I know people wrap their manifolds and whatnot to keep in the heat, but I just read here somewhere that heat doesn't really play much of a part. Can anybody knowledgeable shed some light on this?

HondaHead211

heat is the enemy of a turbo car. the reason a turbocharger is so efficent is that it uses the exhaust gases of the car that wouold otherwise just be wasted and turns it into energy....basically free energy. Heat is the enemy of all engines but especially turbo engines. the reason people use intercoolers inb turbo cars is to cool the air entering the engine. colder air makes for denser air therefore increasing the amount of air in the combustion chamber which increase the amount of fuel used which increases power.people heat wrap rubos to keep other engine heat away from the turbo so it runs cooler. the cooler the air the more air there is and more fuel which creates more power.
as for how a turbo works....once the exhaust gases leave the engine the spin the hot side of the turbo....those gases the exit the car through the exhaust pipe. now that the hot side of the turbo is spinning it turns the cold side. once the cold side starts spinning it creates a vaccum and begins to suck in pressurized fresh air at a high rate. this is boost. thia air is then directed through an intercooler to cool it and then into the engine.
hope this helps.

Si Shane

AFIAK: Because intake manifold pressure is a function of exhaust manifold pressure, it is best to keep the 'energy' inside the gas to allow for more transfer through the turbine. It is the pressure drop, the amount of energy released that controls spool more than the actual velocity of the air.

Lsos

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Si Shane &raquo;</TD></TR><TR><TD CLASS="quote">AFIAK: Because intake manifold pressure is a function of exhaust manifold pressure, it is best to keep the 'energy' inside the gas to allow for more transfer through the turbine. It is the pressure drop, the amount of energy released that controls spool more than the actual velocity of the air.</TD></TR></TABLE>

This is what I'm trying to understand...you're saying it's best to keep the "energy" inside the manifold. By "energy" I assume you mean heat. How does this heat energy get transferred to spin the turbine? I mean...if I heat up a pot on a stove it doesn't just start spinning. Is it the increase in pressure that the heat casues?


<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by HondaHead211 &raquo;</TD></TR><TR><TD CLASS="quote"> heat is the enemy of a turbo car. the reason a turbocharger is so efficent is that it uses the exhaust gases of the car that wouold otherwise just be wasted and turns it into energy....basically free energy. Heat is the enemy of all engines but especially turbo engines. the reason people use intercoolers inb turbo cars is to cool the air entering the engine. colder air makes for denser air therefore increasing the amount of air in the combustion chamber which increase the amount of fuel used which increases power.people heat wrap rubos to keep other engine heat away from the turbo so it runs cooler. the cooler the air the more air there is and more fuel which creates more power.
as for how a turbo works....once the exhaust gases leave the engine the spin the hot side of the turbo....those gases the exit the car through the exhaust pipe. now that the hot side of the turbo is spinning it turns the cold side. once the cold side starts spinning it creates a vaccum and begins to suck in pressurized fresh air at a high rate. this is boost. thia air is then directed through an intercooler to cool it and then into the engine.
hope this helps.</TD></TR></TABLE>

I understand heat on the intake side is bad, but the thing is that heat on the exhaust side is apparently good. I don't see how wrapping a turbo and exhaust manifold would keep it cooler, as exhaust gas is substantially hotter than underhood temperatures. Obviously the wrap serves to keep the heat in, no out.

tallyturbo

when the exhaust goes out of the engine it spins the turbine and in turn make the other side of the turbo spin. the more exhaust comming out the faster the other side spins, thus pushing more air.

beepy

As turbomachinery is concerned, temperature does not matter. However pressure does matter, since it is the pressure drop that is transformed into mechanical work in the turbocharger. If you recall the gas law, if volume and mass remain constant, and you increase temperature, pressure increases. That is why keeping the temperature in the manifold translates to more power in the turbine.

Si Shane

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beepy &raquo;</TD></TR><TR><TD CLASS="quote">As turbomachinery is concerned, temperature does not matter. However pressure does matter, since it is the pressure drop that is transformed into mechanical work in the turbocharger. If you recall the gas law, if volume and mass remain constant, and you increase temperature, pressure increases. That is why keeping the temperature in the manifold translates to more power in the turbine.</TD></TR></TABLE>

Roger that, and thats why temp matters if EMP controls IMP. So far everything fits together, heh!

By energy I mean everything that makes matter move. Like beepy said, all things being equal more heat = more pressure, and since empressure controlls impressure you get 'faster spool' or maybe more power. You use exhaust energy to spool the turbo then you supply a smaller amount of energy to keep it running.

There is a lot more I would like to say but due to my lack of understanding have lots of trouble typing it out. There are some good technical articles on google scholar about wg and em pressures if you care to give a search a go.

I can somewhat understand the spool, but the "steady" state &gt; me.

Lsos

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by beepy &raquo;</TD></TR><TR><TD CLASS="quote">As turbomachinery is concerned, temperature does not matter. However pressure does matter, since it is the pressure drop that is transformed into mechanical work in the turbocharger. If you recall the gas law, if volume and mass remain constant, and you increase temperature, pressure increases. That is why keeping the temperature in the manifold translates to more power in the turbine.</TD></TR></TABLE>

I guess that's what I was thinking. How much difference does it make though? I've been recently hearing people say it makes negligible difference (such as in this thread https://honda-tech.com/zerothread?id=925312 ). If you ran the exhaust through an intercooler, for example, and then to a turbo...would the turbo even work?

Si Shane

You forgot that the airflow is energy. It is about a pressure drop across the turbine.

Pressurize your EM without letting any air out, no flow, lots of pressure, and the turbo doens't spin. You release the pressure and it **flows out of the manifold. You flow air across a restriction and you get a pressure drop. So, since EM pressure dictates IM pressure, the downpipe controlls boost too, since EM pressure is realy a function of how fast the pressure can drop across the turbine. Whoowee


Theory and understanding FTW, who cares about the HP you might get. Don't ask these questions for 5hp, ask them because you are curious.

beepy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Lsos &raquo;</TD></TR><TR><TD CLASS="quote">
If you ran the exhaust through an intercooler, for example, and then to a turbo...would the turbo even work? </TD></TR></TABLE>

Yes, the turbo would still work. However since the intercooler would cause a drop in pressure due to the cooling (and pipe losses, but ignore that), there would be less pressure available for the turbo to drop.

p10hlm

http://forums.evans-tuning.com/viewtopic.php?t=43 I hope this helps.