rjardy

Just wondering what everyone thinks is more effiecient. Keep in mind that our cars have an average eficiency of 25 to 30 percent. Evan the best internal combustion engine designed, runs at only 60 percent eficiency. I am not talking about fuel eficiency here. Actual eficiency. Keep this formula in mind G+W=W (heat +work equals work) We all know that a turbocharged motor creats allot of extra heat. Physics tells us that HEAT is the only form of wasted energy. Heat is the only non-scavangable form of energy. Second law of thermo dynamics will allso apply here, very much so.(there is no such thing as a free lunch) I know the text book answer just want to get some engineers prespective on this. Im sure this has been covered before, but not in this manner. Let's keep this intelectual, and not just say, turbo wins, it makes more power.......That is only part of the eficiency piece of the pie.

Robert

VTC_CiViC

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjardy &raquo;</TD></TR><TR><TD CLASS="quote">Just wondering what everyone thinks is more effiecient. Keep in mind that our cars have an average eficiency of 25 to 30 percent. Evan the best internal combustion engine designed, runs at only 60 percent eficiency. I am not talking about fuel eficiency here. Actual eficiency. Keep this formula in mind G+W=W (heat +work equals work) We all know that a turbocharged motor creats allot of extra heat. Physics tells us that HEAT is the only form of wasted energy. Heat is the only non-scavangable form of energy. Second law of thermo dynamics will allso apply here, very much so.(there is no such thing as a free lunch) I know the text book answer just want to get some engineers prespective on this. Im sure this has been covered before, but not in this manner. Let's keep this intelectual, and not just say, turbo wins, it makes more power.......That is only part of the eficiency piece of the pie.

Robert </TD></TR></TABLE>

..threads like this is why I love H-T

*VTC props his feet up and adjusts his glasses getting ready to read*

rjardy

Come on people, use your nuggets!


Rob

leadfoot78

I'm no engineer but maybe I’ll start and others can give their $.02. If u compare two different engines it's hard to say which is more efficient, but if u compare an NA B18 and turbo B18 the turbo may be more efficient. If you talk about the heat generated by the engine it self, there is not much difference since most people are making almost twice the power of a stock motor but stock cooling system. But of curse the turbo, and the whole exhaust system generates a lot of heat too, substantially more than NA. The variables are endless: more fuel and EGT goes down, les energy wasted in heat but more wasted in fuel(fuel is energy too). Exhaust heat can be controlled by piping diameter too, a 3in pipe can flow more faster and will make the EGT's go down. Also, fuel octane and timing will make a difference. Am I talking out of my ***?


Oh, and I like turbo, it just makes more power, isin't that why we are all here?

Mike D

well the actual internal combustion process should not be any more efficient whether or not its NA or FI.....follow me? i say this because the actual process does not change.


so i would think that if you looked at the two engines as systems, although the turbo might put out more hp/liter, the fuel input/power output should be the same, or close atleast.

This is considering that we all live hypothetical world where every engine uses the stochiametric air/fuel ratio of ~14:1. But we all know that doesnt happen, so they should be close in efficiency, but not exact.

Mike

MADEINIRAQ

you are saying 25-30% efficient as in.. the other ~70% (of heat) is lost through exhaust and radiator.

I would say since you are using some of the lost heat to spin the turbo, you are gaining efficiency but you are also losing some by forcing more air into the engine and creating even more heat

lazerus

1.6L na..

1.6L turbo

which will make more power?

obviously with the displacement, the turbocharged motor will be more efficient in terms of power per litre, but it will be less efficient as far as BSFC because of the richer AFRs you generally run with a turbocharger..

I think it's all about your perspective though.

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by leadfoot78 &raquo;</TD></TR><TR><TD CLASS="quote">I'm no engineer but maybe IÂ’ll start and others can give their $.02. If u compare two different engines it's hard to say which is more efficient, but if u compare an NA B18 and turbo B18 the turbo may be more efficient. If you talk about the heat generated by the engine it self, there is not much difference since most people are making almost twice the power of a stock motor but stock cooling system. But of curse the turbo, and the whole exhaust system generates a lot of heat too, substantially more than NA. The variables are endless: more fuel and EGT goes down, les energy wasted in heat but more wasted in fuel(fuel is energy too). Exhaust heat can be controlled by piping diameter too, a 3in pipe can flow more faster and will make the EGT's go down. Also, fuel octane and timing will make a difference. Am I talking out of my ***?


Oh, and I like turbo, it just makes more power, isin't that why we are all here? </TD></TR></TABLE>

You are forgetting the equation. When you add a turbo, that becomes part of the work, part of the proccess, its in the eqation as work, to make final out come. It makes ALLOT of heat. allot of wasted energy. Please people this is not about power out put, its about eficiency.

Rob

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by madeiniraq &raquo;</TD></TR><TR><TD CLASS="quote">you are saying 25-30% efficient as in.. the other ~70% (of heat) is lost through exhaust and radiator.

I would say since you are using some of the lost heat to spin the turbo, you are gaining efficiency but you are also losing some by forcing more air into the engine and creating even more heat</TD></TR></TABLE>

You are not using lost heat to spin the turbo, you are using the force created by the piston to push the spent combustion gasses out of the chamber. Thats what is spinning the turbo. YOU CAN NOT USE HEAT FOR ANYTHING. it is wasted energy, unscavangeable.

Rob

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mike D &raquo;</TD></TR><TR><TD CLASS="quote">
This is considering that we all live hypothetical world where every engine uses the stochiametric air/fuel ratio of ~14:1. But we all know that doesnt happen, so they should be close in efficiency, but not exact.

Mike</TD></TR></TABLE>
Thinka about this, we run turbo cars at around 12:1, why? because if we ran stioch, it would pre ignite or detonate, why? because why you compress somthing it heats up, therefore bringing you closer to your flash point of the mixture. So we put more fuel in there to compensate and allow it to not pre ignite, thats a big handicapp in favor of the un-eficiency of a turbo charge engine.


Rob

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by leadfoot78 &raquo;</TD></TR><TR><TD CLASS="quote">


Oh, and I like turbo, it just makes more power, isin't that why we are all here? </TD></TR></TABLE>

I'm here for intelectual conversation

Rob

Mike D

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjardy &raquo;</TD></TR><TR><TD CLASS="quote">
Thinka about this, we run turbo cars at around 12:1, why? because if we ran stioch, it would pre ignite or detonate, why? because why you compress somthing it heats up, therefore bringing you closer to your flash point of the mixture. So we put more fuel in there to compensate and allow it to not pre ignite, thats a big handicapp in favor of the un-eficiency of a turbo charge engine.


Rob</TD></TR></TABLE>

very true. but i think that with most NA tuned to 13:1 or even 13.5:1, most of the inefficiency would come from the turbo, especially since even the better turbos are only around.....say 75-80% efficient?

Still though, the overall efficiency should be that different between the two, correct?

Mike

94dxt

Wouldn't a NA motor be more efficient since it takes more fuel for an FI motor to make 200hp than it does an NA motor to make 200hp? Although a FI motor is going to make alot more torque. I'd have to say FI is more efficent for torque and NA for HP

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 94dxt &raquo;</TD></TR><TR><TD CLASS="quote">Wouldn't a NA motor be more efficient since it takes more fuel for an FI motor to make 200hp than it does an NA motor to make 200hp? Although a FI motor is going to make alot more torque. I'd have to say FI is more efficent for torque and NA for HP</TD></TR></TABLE>

Please read the whole post, eficiency is not rated on HP...


Rob

rjardy

Keep in mind that everything that the motor does requires energy, therefore increasing that side of the equation.
Everything from opening the fuel injector, to actuating the wastegate. All the little things like that require energy in one form or another. That is whats in the equation. Once again its not about the HP of a turbo car VS. that of a NA car, i think that we all know the answer to that one.

Rob

tjbizzo

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by rjardy &raquo;</TD></TR><TR><TD CLASS="quote">

You are not using lost heat to spin the turbo, you are using the force created by the piston to push the spent combustion gasses out of the chamber. Thats what is spinning the turbo. YOU CAN NOT USE HEAT FOR ANYTHING. it is wasted energy, unscavangeable.

Rob</TD></TR></TABLE>

Um...you mean like a steam engine, i.e. the boiler at a fossil fuel or nuclear (nukulur for you Bush fans) power plant? So yes, you can use heat for lots of things. It's just that you CAN'T convert heat to ANY OTHER FORM of energy with perfect efficiency, while you CAN convert EVERY OTHER FORM into heat with perfect efficiency. ENTROPY, can ya dig it? And yes, you are using what is normally considered waste heat energy in the exhaust, in the form of the expansion energy of the hot gas, to spin the turbine. If you don't believe me, put an egt gauge before the turbo and put one after the turbo. There will be a huge difference in temperatures because of the heat energy used to spin the turbine. And before you say "Nuh unh, it's da force created by da piston dat spins duh terbin" then consider this: if the piston just stopped at bottom dead center as the exhaust valve began to open, a LOT of hot exhaust gas would still rush out under high pressure. The piston just gives it a little more energy, but it gets most of its energy from the combustion of the fuel. Cheers

rjardy

Bottom line is that an NA motor will be more eficient. when you add a turbo charger in to the system, the ratio will increase. Both sides of it. Heat+ work over work. Heat is increased as is work, and as in the final out come, work. The ratio will not stay the same as the heat and work increase compared to that of the turbo engine. Keep this in mind, your power increases, so does the work, like this, more fuel in combustion chamber to prevent pre- ignition. And under extreme conditions,you will have to intorduce more spark the mixture, thus further icreasing the ratio in the favor of the NA motor. I know its a bit to grasp, but just think about it for a while.


Rob

rjardy

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by tjbizzo &raquo;</TD></TR><TR><TD CLASS="quote">

Um...you mean like a steam engine, i.e. the boiler at a fossil fuel or nuclear (nukulur for you Bush fans) power plant? So yes, you can use heat for lots of things. It's just that you CAN'T convert heat to ANY OTHER FORM of energy with perfect efficiency, while you CAN convert EVERY OTHER FORM into heat with perfect efficiency. ENTROPY, can ya dig it? And yes, you are using what is normally considered waste heat energy in the exhaust, in the form of the expansion energy of the hot gas, to spin the turbine. If you don't believe me, put an egt gauge before the turbo and put one after the turbo. There will be a huge difference in temperatures because of the heat energy used to spin the turbine. And before you say "Nuh unh, it's da force created by da piston dat spins duh terbin" then consider this: if the piston just stopped at bottom dead center as the exhaust valve began to open, a LOT of hot exhaust gas would still rush out under high pressure. The piston just gives it a little more energy, but it gets most of its energy from the combustion of the fuel. Cheers</TD></TR></TABLE>

Entropy as stated in the laws of thermodynamics states that everything is going to a greater dissorder. So basically if you have 2 tanks of equal amount of volume but they are at different temeratures, heat will then transfer to the tank with less heat. To the point of equalibrium. Thats entropy...


YOu mentioned steam engine. is it just using heat? NO is water not in the equation? yes it is. You can transfer the heat. but you cannot convert heat to work.
heat cannot creat usable work by itself.
You say the boiler, take the water out of it and see how it works. It wont..

Rob

rjardy

Allso, molecule expansion is not the biggest factor in spining the turbine...
I think that you understand that. Will it play a role? sure anything that expands is going to try and move whatever is in its way..


Rob

SoulSurfer

Why are you trying to make us feel stupid, Rob?

JM Performance

BSFC (break specific fuel consumption?)

basically how much power you make per part of fuel.

NA cars are .45 to .50
Turbo cars are .60 to .65

That should answer it, no?

rjardy

if fuel eficiency was what we were talking about then yes. But its not, fuel consumption is just a small part of over all efficiency.


Rob

pornstarSR

ok let me try and take a stab at it...

efficeincy...not fuel economy, not horsepower...but the ration of the fuel burnt, and the power produced....but not the way you think..not HP total...

say if you put one squirt of fuel into a NA 14:1 comp LS/vtec
you also put that one squirt(SAME volume) in a 10:1 comp LS/vtec(to be fair and equal)turbo

the fact that the NA engine will produce more power on the fuel it ingested at that moment.

see this is hard to explain, i understand what your trying to say RJ....but its hard to bring it out without saying horsepower...cause thats not what its about...

its kind of like a Ball bearing turbo and a non-ballbearing turbo...it take more force to spin a non ballbearing turbo(not alot of force) because of the friction, thus saying that it is not a very efficient use of the force

i might be stabing in the dark with it..but hey im trying

nigel

wheres stoopid when you need him, and j davis. are they both rocket scientists?

Dr Honda

ok... I read threw the post, and I'm not understanding what you are trying to get at. Yes... an internal combustion engine is a total waste when it comes down to "Pure thremo efficancy". (one of the first things you look at in thermodynamics) But if you are trying to say a turbo engine is less efficiant thermo-ly, then a NA engine... it realy doesn't mater. the efficancy difference would only be a few percent. (too close to care about) besides... yes, the turbo is reclaming heat to create the boost. if the air comming out of the engine wasn't hot and expanded (the nateral gas law is part of thermo. PV=NRT)... it wouldn't be able to drive the turbine to the point that it could compress the cool intake air.

But over all... as far as an engine is concerned... the turbo engine is more efficint volumetricly. obviuosly... it makes more power per displacment.

If we wanted eficiant engines... we would all have diesels under our hoods... or better yet... sterling engines. (do you know what those are) But we don't care about the thermo efficancy... we care about HP.

Anyway... if you can find a real way to get 100% thremo efficancy from a fuel... we could run our cars for our entire lives on one tank of gas. (breaking down the fuel at the atomic level)

Oh... how can you simply have work on both sides of your equation?? How can work + ANYTHNG = work? please explain. I will understand... I have B.S. degrees in both physics and chem.

Lastly... There is a way to directly make work from Heat. If I light a fire in the chair your sittign on... I bet you will work to put it out. (or puch me in the throat )

so... were you just board, or are you going threw a thermo class?