SOHC50shot

whats up guys, this is a pretty general question that differ's between many cars. But does anyone have any idea what pressure or velocity the exaust needs to create to spin the exaust side of a turbo (T3 for example). By spin i mean enough to create a decent amount of boost. Any information even relating to that subject would be helpful. Thanks guys

The Original Whitey

This might help you:


http://not2fast.wryday.com/gasflow/velocity.shtml

0xenocron

edited because people complain even when you are trying to help


Modified by xenocron at 7:19 PM 12/16/2004

Full-Race Geoff

thats not entirely true. a lot of people say that and have no reason why they say that.

The Original Whitey

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xenocron &raquo;</TD></TR><TR><TD CLASS="quote">the exhaust wheel is spun by heat energy, not pressure or air flow

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

Mass flow rate is what spins a turbine, heat is a very disorganized form of work. You can think of one of those lawn fans, which spins it fast; putting it near a heater or spraying a hose into the blades.

SOHC50shot

did you say heat energry?? where are you pulling this from thats retarded.. i need some expert advice, not guys guessing.. that link was helpful thanks

spitz7985

Let me specify the question (no offense, josh). This is what we are trying to figure out.

Basically, what is the average rate that the exhaust is entering the turbine at X rpm? I realize this varies incredibly with the engine, turbo-back exhaust, manifold, turbine inlet size, etcetera. We are just looking for a range.

Another thing that could help would be the pressure inside the exhaust manifold at X rpm. Again, I know this varies.

Thanks,
Brandon

0xenocron

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Full-Race Geoff &raquo;</TD></TR><TR><TD CLASS="quote">thats not entirely true. a lot of people say that and have no reason why they say that.</TD></TR></TABLE>

And why do people coat turbo headers and wrap them in thermal tape to keep as much heat inside the manifold as possible?

Geoff is an engineer...I'm not, I know he can explain it better and wish he just would instead of hinting at things

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC50shot &raquo;</TD></TR><TR><TD CLASS="quote">did you say heat energry?? where are you pulling this from thats retarded.. i need some expert advice, not guys guessing.. that link was helpful thanks</TD></TR></TABLE>

Read this link:
http://www.mustang50magazine.c...17739/

Notice especially where the author says, and I quote, "Incon’s design also places the turbos as close to the exhaust ports as possible and keeps the gases hot inside thick, cast-iron manifolds, because it is exhaust heat energy, not gas movement, that drives the turbine section."

Another link I came across stated, "The hot gas in the turbine expands to develop mechanical energy, as expanding steam does in a steam turbine."

Heat energy EXPANDS (what a concept). Try pouring boiling hot water in a tupperware container, put the lid on & shake it very close to your face...then please tell me what happens.

Here is another good explanation:
http://www.turboclub.com/turbotech/TurboFun2.htm

Full-Race Geoff

think about what the guy you are quoting just said

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

...and I quote, "Incon’s design also places the turbos as close to the exhaust ports as possible and keeps the gases hot inside thick, cast-iron manifolds, because it is exhaust heat energy, not gas movement, that drives the turbine section."
</TD></TR></TABLE>

read that to yourself, over and over. do you really think this guy should be writing articles? Dont automatically assume that because you read something, it is true.

0xenocron

Thats why I referenced more than one source and put the least reliable 1st.

Why dont you explain it better for us?

Full-Race Geoff

saving heat is like saving drops of water out of a hose. if you wrap/coat your dp you are helping things a little bit, but it doesnt make a big difference. What makes a difference is velocity, flow quality, and pressure. im goin to bed but i think one thing worth thinking about is the barrel of a gun. im goin to bed got a lot of work tomororow. ill help u out more tomororow if you need any specific quesitons answered


Modified by Full-Race Geoff at 1:27 AM 12/16/2004

The Original Whitey

heat does not spin a turbine Heat is a VERY disorganized. Mass flow rate is what spins a turbine! Heat helps a little bit but does not spin a turbine like the mass flow rate of the gas. This is one of the first things you learn in a thermodynamics class.

0xenocron

Mass Flow Rate
Definition:
The transfer of a mass of substance per unit of time.

Ok...I'm no fricken engineer, so I may not be explaining (understanding) this as well as I had hoped...but I know it cant just be Mass Flow Rate spinning a wheel. Obviously it takes a mass to move the wheel.

However, MF into the engine does not equal MF coming out of the engine, so it cant just be mass flow. There is something that increases the Mass Flow, heat energy, no? So the expansion of hot gases (molecules with mass) coming out of the engine are expanding and speeding up from a location of higher energy to a location of lower energy.

BTW, Whitey...you suck, I'm going to come down to philly one of these days and kick your ***

The Original Whitey

Alright, basically you treat the gas a a liquid. So think of it as if liquid is coming out of your motor. What spins the turbine faster; the liquid moving faster or the liquid being hotter? The velocity of the liquid is what makes the turbine spin fast. Yeah heat to a point does spin a turbine but its minimal to the mass flow rate.


Think of Nuclear power plants. A Nuclear power plant basically just heats water to spin a turbine. The actually steam itself is what spins the turbine blades of the generator. Yeah they use heat to change the water into vapor but its the vapor (not the heat) that is actually producing the work. If you take a thermodynamics class you study alot of steam tables, a steam table basically tells you the 'quality' of the steam (how dense it is). So to spin a turbine in a power plant (same deal with a turbo) the expanding water vapor is what does the work. The heat is only used to get the quality of the vapor right (too dense a mixture cause condensation and tears the **** out of the blades.)

BTW xenocron, I'm comming to kick your *** for making me post and be viewed as a "Honda-Tech" member

SOHC50shot

Getting off the subject of this heat spins the turbo BS.. any ideas on the origional question?? Ive asked a couple of my professors here at MSOE, and all they tell me is how to measure it. Is this knowledge outhere or am i chasing a white rabbit?

Full-Race Geoff

the question you are asking is somewhat open ended, there is certainly no "right" answer. The pressure and velocity needed depends on many many variables.

I recommend actually solving backwards by finding a turbine map, and then you can use that to figure out what flow and how much you want to get a certain turbine wheel speed.

dennis

Christ.... Does anyone do their own research or just duplicate what they heard.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">2. The turbo derives its energy source from:
A. The temperature of the exhaust gas
B. The pressure of the exhaust gas
C. Both the temperature and pressure of the exhaust gas
D. The engine power</TD></TR></TABLE>

Answer is C (According to Garrett, I'm guessing they have a clue...)


Read/Learn:
http://www.honeywell.com/sites...me=P1

Quiz:
http://www.honeywell.com/sites...t.htm

I'd probably listen to Geoff too since I'm guessing he has a clue as well - and as he stated, pressure/velocity is going to vary greatly depending on engine size, VE, turbine size yadda yadda yadda...

Read/Listen/Evaluate/Test/Challenge - Form your own opinions after doing such.

toolowsol

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by xenocron &raquo;</TD></TR><TR><TD CLASS="quote">Ok...I'm no fricken engineer, so I may not be explaining (understanding) this as well as I had hoped...but</TD></TR></TABLE>

Ok then please do not try to discuss this issue. There is a big *** equation to solve for all the variables here, but pretty much the only guys that understand it completely are mechanical engineers. The question has already been answered probably as best it can be here. You need to figure out at what velocity you want to move the air, what temperature you want it, to solve for other things you need. In order to get answers, you MUST make assumptions about other things. Using bernouslies (spelling ) equation, you can figure out most of it. You must also use the turbine map as Geoff stated to work backwards to figure out what you want to solve for. This isn't an easy question to answer, as you will need to modify the anser based on your particular case. Expect to spend a day or 3 solving it.

Full-Race Geoff

cute quiz question. I think it actually should read:

c: both the temperature *differential* and pressure *differential*

dp/dt &lt;- this means delta p by delta t, or pressure differential by temperature differential.

the differential is what matters, not the actual value.

SOHC50shot

sounds good everyone.. I will try working with it and i'll see what i can come up with, Thanks for the input everyone, mostly Geoff. I found an equation i can work with here in "Maximum Boost" by Corky Bell Airflow rate of a NA motor is as follows
cid x rpm x .05 x E (subscript) v
-----------------------------------------
1728

E (sub) v being the volumetric efficiency
1728 converts cubic inches to cubic feet

Hopefully i can play with that equation to get a good start point

GREAT Turbo book by the way, i recommend it to any forced induction fan.


Modified by SOHC50shot at 4:41 PM 12/16/2004

dennis

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Full-Race Geoff &raquo;</TD></TR><TR><TD CLASS="quote">cute quiz question. I think it actually should read:

c: both the temperature *differential* and pressure *differential*

dp/dt &lt;- this means delta p by delta t, or pressure differential by temperature differential.

the differential is what matters, not the actual value.</TD></TR></TABLE>

There you go! Case in point why you don't go around believing/repeating everything you read/hear.

spitz7985

Dennis, your replies were a bit nasty, I hope they were directed only at xenocron and not myself or sohc50shot. Both he and I are mechanical engineers-in-training and know a bit about what we are talking about, though are still learning.

Anyway, we didn't really expect a straight answer on this, as it is too speculative, but it was worth a shot.

xenocron, no one would be mad at you if you would have said something like "I think I heard somewhere..." but instead you stated it as a fact when you were not sure.

AND, fellow engineers, does pressure not partially depend on temperature anyway? Of course the flow rate is dependent on both. Pressure is what makes flow, is it not?

-Brandon

dennis

My posts weren't directed at anyone in particular. They are, however, directed to everyone who wants to be spoonfed and everyone who acts like a parrot on HT.

That's great you're a mech. engineer in training. I wish there were more like you on HT. You should know more than anyone that there's probably a vast amount of theory behind the aforementioned question. I do commend you though for actually trying to figure out the theory behind something - that's rare around here.

I'm not trying to be a dick. I've just got a lot of work to do here at work, but I don't want to do any of it. So I read HT too much in procrastination. The more I read, the more I get upset with useless posts with no effort in trying to figure out the answer to their own question. (not saying this is one of them)

Everything I know is from things I've read/seen/heard/tried/failed/blownup/crashed/succeeded in myself and I expect others to do a little footwork before asking questions - and if you did do some footwork, explain that in your question. You'll get much more respect.

PS, If you want to get deep into theory of various subjects, I suggest you hang around the theoldone.com board. Ask for Luke

Full-Race Geoff

PV=mRT of course this is almost uselss in anything but thermo 1, but it does give you an idea of how gasses behave (they never follow the laws, and they are compressible and they are more than 1-D and etc etc etc)

what year are you guys? Once you get into thermo 1, thermo 2 and fluids it all starts to come together

SOHC50shot

Modified by SOHC50shot at 2:17 AM 12/17/2004