rear mounted turbos are nothing new on bent 8 engines. i have seen a few aftermarket setups for c*&^ys that mount two turbos at the rear. i too would think there would be some serious lag though. also there is a really awsome even if it is a bent 8 pon&^7c tem(*st that has twin rear mounted turbos and is a super sleeper car. search for it on you tube. this is an interesting idea i just wonder if the ford 6 puts out enough exhaust pressure quick enough to make it work.
Rear mounted turbo...
- Thread starter Falcon Ranch
- Start date
Army of Six
Well-known member
JGTurbo":eij2j4m2 said:
now im confused. Heat good? heat bad? heat doesnt matter?
tjnavyblue
Well-known member
JGTurbo":3gnw0iu5 said:
Course not. It's pressure differential. BIG difference.
Falcon Ranch
Well-known member
That's funny CobraSix...when I mount the turbo in the back, I'm eliminating the muffler all together...NO MUFFLER...the turbo will do a good job to muffle the sound, not to mention the awesome exhaust note it will make while under boost...the header has a high temp coating and does a great job keeping the heat inside the header, so I can wrap the remaining exhaust if needed to retain heat...from the back of the header to where I would mount the turbo is only about 4 ft of pipe.
JGTurbo...that sounds great 300+hp would be awesome!...so the turbo is good for another 300 or 300+ total output?..sorry, no calipers here...my brother has some, but an hours drive away...I so much appreciate your input...do you know where I can find this flange you speak ofand will it work with any WG?...I could always add it in later with a hole saw right?...I'm a pretty good welder/fabricator...it's not like I'm trying to work around the engine anyway...there will be lots of room to work...of course I would have to remove the turbo so I can clean the metal shavings.
JGTurbo, another question...if I do run this thing without WG or a BOV I should be OK right?...how much power is lost by heat...I am really not trying to build a world record holder, I just want to be able to get a nice in your seat feel of acceleration...like the motor is actually bigger then it is...since I am running the turbo in the rear of the car with all that air flow, I should be able to safely run another 2-3 psi without any problems right...of course I need a boost gauge to safely test the boost say 1 psi at a time and see what the turbo will actually do right?...any suggestion about how to do this safely...recommended threads to read about timing and dizzy mods...I got the carb thing figured out with help from Does10's.
Again, I want to thank all the pro's for their technical support...I could not do this turbo swap without your help...besides, I want to be the first person to have a rear mounted turbo in a Falcon body!
Dave 8)
JGTurbo...that sounds great 300+hp would be awesome!...so the turbo is good for another 300 or 300+ total output?..sorry, no calipers here...my brother has some, but an hours drive away...I so much appreciate your input...do you know where I can find this flange you speak ofand will it work with any WG?...I could always add it in later with a hole saw right?...I'm a pretty good welder/fabricator...it's not like I'm trying to work around the engine anyway...there will be lots of room to work...of course I would have to remove the turbo so I can clean the metal shavings.
JGTurbo, another question...if I do run this thing without WG or a BOV I should be OK right?...how much power is lost by heat...I am really not trying to build a world record holder, I just want to be able to get a nice in your seat feel of acceleration...like the motor is actually bigger then it is...since I am running the turbo in the rear of the car with all that air flow, I should be able to safely run another 2-3 psi without any problems right...of course I need a boost gauge to safely test the boost say 1 psi at a time and see what the turbo will actually do right?...any suggestion about how to do this safely...recommended threads to read about timing and dizzy mods...I got the carb thing figured out with help from Does10's.
Again, I want to thank all the pro's for their technical support...I could not do this turbo swap without your help...besides, I want to be the first person to have a rear mounted turbo in a Falcon body!
Dave 8)
Work output = Energy input - losses
If you think of it in terms of exhaust gas energy before and after the turbine, then you realize that it's all just different forms of the same thing and the goal is to transfer as much energy as possible to the turbine while the exhaust gasses are passing through it. The amount transferred is the amount available to do work.
I don't have the time or the interest to do so but if you run the analysis, I'll bet dollars to doughnuts that the energy transfer is more efficient at higher gas temperatures.
If you think of it in terms of exhaust gas energy before and after the turbine, then you realize that it's all just different forms of the same thing and the goal is to transfer as much energy as possible to the turbine while the exhaust gasses are passing through it. The amount transferred is the amount available to do work.
I don't have the time or the interest to do so but if you run the analysis, I'll bet dollars to doughnuts that the energy transfer is more efficient at higher gas temperatures.
Falcon Ranch
Well-known member
tjnavyblue":3bmnyy7e said:JGTurbo":3bmnyy7e said:
Course not. It's pressure differential. BIG difference.
If that's the case then, having a short piece of pipe out the turbo would cause a huge pressure difference...I'm talk 'n something like 15-18" long...the way my turbo faces, the outlet is straight out the side of the body with a chrome tip welded on...should sound really sweet!
tjnavyblue
Well-known member
StrangeRanger":1hnf5ato said:
.JGTurbo":1hnf5ato said:
Seems to me we are on the same page. I can't imagine a case in which you would have a pressure differential with no increase in temperature. The two are intertwined, with the outcome measurable in the form of the volume of air coming out the exhaust.
JGTurbo
Well-known member
Strange Ranger, I agree with you that the exhaust has more energy when it
is hotter. The exhaust is carrying many forms of energy (kinetic, thermal,
sonic...) I was just trying to say that I think the turbo is driven by the kinetic
energy (related to the velocity) of the exhaust (that's why the turbo forces all
the air through such a small spiral, it increases velocity, which is squared in
the equation). The air moves because of the pressure differential between
the inlet and outlet sides of the turbine. In a closed, free flowing exhaust
system, the pressure at the turbine inlet should be the same whether it is
located at the front near the engine or at the back of the car. I know that the
heat in the exhaust is energy, I'm just not seeing how the turbo makes use of it.
I know you're an engineer as well, so correct me if I'm wrong.
is hotter. The exhaust is carrying many forms of energy (kinetic, thermal,
sonic...) I was just trying to say that I think the turbo is driven by the kinetic
energy (related to the velocity) of the exhaust (that's why the turbo forces all
the air through such a small spiral, it increases velocity, which is squared in
the equation). The air moves because of the pressure differential between
the inlet and outlet sides of the turbine. In a closed, free flowing exhaust
system, the pressure at the turbine inlet should be the same whether it is
located at the front near the engine or at the back of the car. I know that the
heat in the exhaust is energy, I'm just not seeing how the turbo makes use of it.
I know you're an engineer as well, so correct me if I'm wrong.
Falcon Ranch
Well-known member
This is all good stuff!...myself and others who read this thread are learning some great info...and thank you JGTurbo for sticking up for me...I am a firm believer that whether I mount my turbo in the front (like everyone suggests)or at the rear of the car, I'm going to get the same response...just because the turbo is 8-9 feet behind me doesn't mean it will take eternity to build any kind of good boost.
Look at it this way...if you took a ten foot PVC pipe and blew through one end with an air hose and measured the time it took to move a napkin that dangled as a flap over the other end, the napkin would move the instant you caused an air difference inside the pipe...the end with the air hose would need to be sealed as would a exhaust system...now add another piece of ten foot pipe and have it return where you are to simulate a turbo set up...so now you have 1 ten ft pipe going away, then it take a 90 turn, a short piece of pipe, another 90 turn and a 2nd ten ft pipe...now squeeze the air and watch the napkin move again...about the same time as it was with a single pipe...whether you have 1 or 2 pipes in the equation, the pipe itself has a certain body of air that already exists...take an empty bottle of water and cap it off...you say it's empty, right...wrong!, now try to squeeze that bottle, you can only squeeze it a little because the air inside take up space just like my exhaust and my intake return will...I'm sure there are limits to how many pipes can be added before there is a delay, but for the distance I'm using I'll be OK...I'm no physicists but do understand the laws of physics...to a certain extent.
Now envision my turbo sitting in the back of my Ranchero...this is the best I can do to explain to those who think mounting the turbo in the rear of my Ranchero is going to take forever to make boost or have so much turbo lag that I am wasting my time...try the experiment for yourself
Dave 8)
Look at it this way...if you took a ten foot PVC pipe and blew through one end with an air hose and measured the time it took to move a napkin that dangled as a flap over the other end, the napkin would move the instant you caused an air difference inside the pipe...the end with the air hose would need to be sealed as would a exhaust system...now add another piece of ten foot pipe and have it return where you are to simulate a turbo set up...so now you have 1 ten ft pipe going away, then it take a 90 turn, a short piece of pipe, another 90 turn and a 2nd ten ft pipe...now squeeze the air and watch the napkin move again...about the same time as it was with a single pipe...whether you have 1 or 2 pipes in the equation, the pipe itself has a certain body of air that already exists...take an empty bottle of water and cap it off...you say it's empty, right...wrong!, now try to squeeze that bottle, you can only squeeze it a little because the air inside take up space just like my exhaust and my intake return will...I'm sure there are limits to how many pipes can be added before there is a delay, but for the distance I'm using I'll be OK...I'm no physicists but do understand the laws of physics...to a certain extent.
Now envision my turbo sitting in the back of my Ranchero...this is the best I can do to explain to those who think mounting the turbo in the rear of my Ranchero is going to take forever to make boost or have so much turbo lag that I am wasting my time...try the experiment for yourself
Dave 8)
JGTurbo
Well-known member
Here's a great video to watch. It's an STS turbo kit on a 2003 Dodge Ram. Yes, the guy did wrap his exhaust system, but STS systems are not usually wrapped. Cool video anyway:
http://www.youtube.com/watch?v=2ahXbH1TrVU
http://www.youtube.com/watch?v=2ahXbH1TrVU
When hot gasses expand, they cool. The hotter they are, the more energy they have to give up in the cooling process. This is exactly what goes on in the turbine.
Falcon Ranch
Well-known member
StrangeRanger":3345bnoq said:
I do agree...I'm only look 'n for a 5-8lb boost, if I get more then that then I still won't complain...I'm not trying to build a rocket ship...so no matter what you guys say to try and convince me otherwise, it's still going in the back.
Dave 8)
Falcon Ranch
Well-known member
JGTurbo":36va6y3o said:
Cool vid
...I watched the video 2 times and could not here any turbo lag when he got into the throttle...it seemed to have way more power then he needed A TRUE SLEEPER!
Dave 8)
Have you considered what happens when you splash through a water-filled chuckhole and splash 50° water all over a 200+° turbo? Just a thought.
Falcon Ranch
Well-known member
StrangeRanger":3bcsybl9 said:
I was planing on installing a splash shield...even though it only rains here in Texas like 5 days a year...I did plan to install one.
Dave 8)
let's restate it another way.
Would you put an intercooler on the exhaust BEFORE the turbo (yes, i know intercoolers don't go on the exhaust at all)? That is basically what you are doing. You are adding an intercooler with all the exhaust piping. Even if wrapped you are still losing heat.
Simple version: Hot gases more faster and will exert more energy on the turbines. Turbines basically use the PV=nRT (ideal gas law) equation for creating energy. They use pressure and temperature to create the energy. It's not just physics, it's fluid dynamics and gas laws. If you drop pressure, or drop temperature, you lose energy. Using derivations of the ideal gas law, you will find that a molecules kinetic energy is direction proportional to it's absolute temperature. (that's stating it simply).
Additionally, your pipe example is not a realistic example of the system you intend to build. One part that you simplified and left out is air is a compressible fluid. If you wanted to simulate the system, you have to put a restriction simulating your turbo on the other side. Turbos are great because they only react as exhaust pressure increases due to load. Otherwise they don't provide much. This is because the turbo requires a certain amount of pressure to spin and create boost. If you put a turbine on the end of your 10 foot pipe and then ran a 10 foot pipe back, and then if you compared it to a system with 2' of pipe total you'll see a difference because the amount of time it takes for that air to fully compress is increased on the longer system.
As for the bottle example, try comparing a large 2L bottle filled with the same amount of air as a 12oz bottle and try squeezing them. You'll find you can't squeeze the 12oz bottle but should be able to squeeze the 2L bottle.
OTher problem that will come into play is the general throttle response. For this to work, your intake will I assume be on back of the car by the turbo? You'll end up with a 6-8 foot intake which will make throttle response when you aren't until boost sluggish.
If a remote turbo was a truly good design, then other applications would utilize it. I work extensively in the marine engineering field and on marine engines, we want the turbos as close as possible to the exhaust because we want the turbo be as efficient as possible. Short runs for gases are always ideal when you are trying to create and retain energy.
No one here is saying it isn't possible or can't be done or that you won't make boost and improve the HP of your car. Personally I think you are going a little overboard on trying to be unique when a turbo charged inline 6 falcon is generally a rare and unique thing already. Why hide the turbo? I really don't think the system you are envisioning is going to be easier to install.
And I may just be getting older, but the thought of an open 6 cylinder exhaust with a turbo on the end of it just makes be cringe and think of all the rice burners around.
Would you put an intercooler on the exhaust BEFORE the turbo (yes, i know intercoolers don't go on the exhaust at all)? That is basically what you are doing. You are adding an intercooler with all the exhaust piping. Even if wrapped you are still losing heat.
Simple version: Hot gases more faster and will exert more energy on the turbines. Turbines basically use the PV=nRT (ideal gas law) equation for creating energy. They use pressure and temperature to create the energy. It's not just physics, it's fluid dynamics and gas laws. If you drop pressure, or drop temperature, you lose energy. Using derivations of the ideal gas law, you will find that a molecules kinetic energy is direction proportional to it's absolute temperature. (that's stating it simply).
Additionally, your pipe example is not a realistic example of the system you intend to build. One part that you simplified and left out is air is a compressible fluid. If you wanted to simulate the system, you have to put a restriction simulating your turbo on the other side. Turbos are great because they only react as exhaust pressure increases due to load. Otherwise they don't provide much. This is because the turbo requires a certain amount of pressure to spin and create boost. If you put a turbine on the end of your 10 foot pipe and then ran a 10 foot pipe back, and then if you compared it to a system with 2' of pipe total you'll see a difference because the amount of time it takes for that air to fully compress is increased on the longer system.
As for the bottle example, try comparing a large 2L bottle filled with the same amount of air as a 12oz bottle and try squeezing them. You'll find you can't squeeze the 12oz bottle but should be able to squeeze the 2L bottle.
OTher problem that will come into play is the general throttle response. For this to work, your intake will I assume be on back of the car by the turbo? You'll end up with a 6-8 foot intake which will make throttle response when you aren't until boost sluggish.
If a remote turbo was a truly good design, then other applications would utilize it. I work extensively in the marine engineering field and on marine engines, we want the turbos as close as possible to the exhaust because we want the turbo be as efficient as possible. Short runs for gases are always ideal when you are trying to create and retain energy.
No one here is saying it isn't possible or can't be done or that you won't make boost and improve the HP of your car. Personally I think you are going a little overboard on trying to be unique when a turbo charged inline 6 falcon is generally a rare and unique thing already. Why hide the turbo? I really don't think the system you are envisioning is going to be easier to install.
And I may just be getting older, but the thought of an open 6 cylinder exhaust with a turbo on the end of it just makes be cringe and think of all the rice burners around.
Falcon Ranch
Well-known member
CobraSix, if you back up a few posts...7 I think, I did say I was going to leave the carb mounted at the manifold :roll:
We're all getting older CobraSix...have you gone to the STS website and listened to any of those videos...there are a few great twin turbo and single turbo cars with no muffler...they're actually quieter then a 40 series flowmaster, even under boost...in my opinion.
The bottle theory is a no brain'r...duh..I way only using it as an example to show that objects take up space...I wasn't trying to win a Nobel prize and compare bottle space VS another...and yes my example had flaws in it as is did not have any resistance(turbo)...but my point was to prove that the length of pipe I was going to use wouldn't make any difference...I wasn't going into the whole fluid dynamics and kinetic energy thing as I'm not a physicists...I just made a simple example.
I appreciate the fact that there are many here who understand the laws of physics or have an engineers degree in thermodynamics...or what ever the case may be...I think backwards if you will...if someone tells me that it can't be done, then I'll try to prove them wrong, degree or no degree...it's what makes us human and different...and I have always been different...all the rodders on my block have supped up Chevy street rods...I'm the only Ford guy here, and to be different I have a supped up six and now to be even more unique, I'm going to mount my turbo in the back of my Ranchero...it is something that I have been meaning to do for some time...in fact, I think I thought of it long before STS started their business...I'm just the little guy with no research funds
CobraSix, I appreciate your input as this is what drives interest among these threads...as knowledge is shared and viewed by many interested parties...I am among the few, well, I think I am the only one here and a couple of others who believes in the STS layout...there are many here are skeptical whether or not I'm just wasting my time...as I have read many posts here on this forum, I see a good percentage of them proven to work despite the negative feedback...I'm not saying it's wrong, it's just human.
Dave
We're all getting older CobraSix...have you gone to the STS website and listened to any of those videos...there are a few great twin turbo and single turbo cars with no muffler...they're actually quieter then a 40 series flowmaster, even under boost...in my opinion.
The bottle theory is a no brain'r...duh..I way only using it as an example to show that objects take up space...I wasn't trying to win a Nobel prize and compare bottle space VS another...and yes my example had flaws in it as is did not have any resistance(turbo)...but my point was to prove that the length of pipe I was going to use wouldn't make any difference...I wasn't going into the whole fluid dynamics and kinetic energy thing as I'm not a physicists...I just made a simple example.
I appreciate the fact that there are many here who understand the laws of physics or have an engineers degree in thermodynamics...or what ever the case may be...I think backwards if you will...if someone tells me that it can't be done, then I'll try to prove them wrong, degree or no degree...it's what makes us human and different...and I have always been different...all the rodders on my block have supped up Chevy street rods...I'm the only Ford guy here, and to be different I have a supped up six and now to be even more unique, I'm going to mount my turbo in the back of my Ranchero...it is something that I have been meaning to do for some time...in fact, I think I thought of it long before STS started their business...I'm just the little guy with no research funds
CobraSix, I appreciate your input as this is what drives interest among these threads...as knowledge is shared and viewed by many interested parties...I am among the few, well, I think I am the only one here and a couple of others who believes in the STS layout...there are many here are skeptical whether or not I'm just wasting my time...as I have read many posts here on this forum, I see a good percentage of them proven to work despite the negative feedback...I'm not saying it's wrong, it's just human.
Dave
JGTurbo
Well-known member
I just visited the STS F.A.Q. section to see what they had to say about all this. This is what I have been trying to say this whole time:
Doesn't heat create the velocity in the exhaust gasses to spool the turbo?
No, heat doesn't create velocity. Heat creates volume. If you look at any
of the physics laws for gasses, you will find that pressure and volume and
heat are related. PV=NRT is a popular one, The V isn't for velocity, it is for
Volume.
The turbine housing is what creates the velocity. The scrolling design that
reduces the volume of the exhaust chamber as it scrolls around causes the
gasses to have to increase in velocity and pressure to maintain the same
flow rate.
Hotter gasses have more volume, thus requiring a higher A/R which in
effect means that it starts at say 3" and scrolls down to approximately 1".
Lower temperature gasses are denser and have less volume, so they
require a lower A/R housing which would start at the same 3" volume, as
the turbine housings use standard flanges, and scroll down to say 3/4".
Now if you were to reverse the housings in application, the conventional
turbo would spool up extremely quick, at say around 1500 rpm but would
cause too much backpressure at higher rpms because the higher volume
of gas couldn't squeeze through the 3/4" hole without requiring a lot of
pressure to force it through. On the reverse side, the remote mounted
turbo with its cooler denser gasses, wouldn't spool up till say around 4000
rpms but once spooled up would make efficient power because it doesn't
require hardly any backpressure to push the lower volume of gas through
the larger 1" hole.
Doesn't heat create the velocity in the exhaust gasses to spool the turbo?
No, heat doesn't create velocity. Heat creates volume. If you look at any
of the physics laws for gasses, you will find that pressure and volume and
heat are related. PV=NRT is a popular one, The V isn't for velocity, it is for
Volume.
The turbine housing is what creates the velocity. The scrolling design that
reduces the volume of the exhaust chamber as it scrolls around causes the
gasses to have to increase in velocity and pressure to maintain the same
flow rate.
Hotter gasses have more volume, thus requiring a higher A/R which in
effect means that it starts at say 3" and scrolls down to approximately 1".
Lower temperature gasses are denser and have less volume, so they
require a lower A/R housing which would start at the same 3" volume, as
the turbine housings use standard flanges, and scroll down to say 3/4".
Now if you were to reverse the housings in application, the conventional
turbo would spool up extremely quick, at say around 1500 rpm but would
cause too much backpressure at higher rpms because the higher volume
of gas couldn't squeeze through the 3/4" hole without requiring a lot of
pressure to force it through. On the reverse side, the remote mounted
turbo with its cooler denser gasses, wouldn't spool up till say around 4000
rpms but once spooled up would make efficient power because it doesn't
require hardly any backpressure to push the lower volume of gas through
the larger 1" hole.
