under body turbo
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From: Gie
I would LOVE to see this in place of the catcon. It seems like there is a perfect amount of space for it.
Due to the cooler air well downstream of the exhaust ports, the medium would be more dense (taking up less space). While the total mass flow rate would remain the same, the volume flowrate would decrease due to the higher density.
mdot = ro * V * A
Q = V*A
mdot = ro *Q
where:
mdot = mass flow rate
ro = density
V = velocity
A = cross sectional area
Q = volume flowrate
If density increases, flowrate must decrease.
The lower flowrate would not be able to spool the turbo as quickly as if it were placed much further upstream...unless the turbo was considerably smaller. Sized appropriately, I would suspect that spool time would not be an issue. This only applies to the turbine side of the system. The compressor side would not have to be resized as the fluid properties (temps/densities) would not have changed.
Due to the cooler air well downstream of the exhaust ports, the medium would be more dense (taking up less space). While the total mass flow rate would remain the same, the volume flowrate would decrease due to the higher density.
mdot = ro * V * A
Q = V*A
mdot = ro *Q
where:
mdot = mass flow rate
ro = density
V = velocity
A = cross sectional area
Q = volume flowrate
If density increases, flowrate must decrease.
The lower flowrate would not be able to spool the turbo as quickly as if it were placed much further upstream...unless the turbo was considerably smaller. Sized appropriately, I would suspect that spool time would not be an issue. This only applies to the turbine side of the system. The compressor side would not have to be resized as the fluid properties (temps/densities) would not have changed.
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From: Sellersburg, IN
[QUOTE=Wildncrazy,May 26 2006, 11:52 AM] If you size the turbo for the cooler air then you can get just as quick a spool up. (FYI it ain't the heat that turns the turbo it is the movement of the air)
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From: Gie
Originally Posted by Wildncrazy,May 26 2006, 10:52 AM
If you size the turbo for the cooler air then you can get just as quick a spool up. (FYI it ain't the heat that turns the turbo it is the movement of the air) According to them the long piping takes the place of the intercooler so doesn't really add all that much throttled air space.
Frankly, if everything was sized appropriately, it wouldnt matter where you placed the turbo (within reason).
Conventional placement with a large turbo and large intercooler would (in theory) provide the same spool characteristics and intake flow rates as downstream placement with a small turbo and small intercooler.
Then again, I could be talking out of my ass.
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From: Gie
Originally Posted by Spoolin,May 26 2006, 01:42 PM
I'm not going to get into a huge debate here. Turbines are much more efficient with hotter air; period. Hot air creates a tremendous amount of velocity over cool air. Spool up time is going to be much greater.
Even if you accomodate the turbine for the heat loss/velocity loss, your turbine would more than likely run out or surge before you got to 8 or 9000 rpm. I would love to see this work but I just don't see it feasable with our engine.
Even if you accomodate the turbine for the heat loss/velocity loss, your turbine would more than likely run out or surge before you got to 8 or 9000 rpm. I would love to see this work but I just don't see it feasable with our engine.
You have a good point. If the air cools down TOO much, you might run out of the effective operating range for the turbo and it would become innefficient.
My point is that you could probably place the turbo where ever you wanted to and still achieve the same performance characteristics if the turbine was sized properly and performing in its operating range.
You could probably do a comparison as follows. All turbos have an efficiency map. They are more efficient at certain operating speeds and flow rates. A small turbo at the rear of the car operating at X flowrate may be more or less efficient than a large turbo in the engine bay operating at the same X flowrate. I'm gonna go check out som compressor maps.
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From: Sellersburg, IN
Originally Posted by slimjim8201,May 26 2006, 02:56 PM
I knew you were going to append your post
You have a good point. If the air cools down TOO much, you might run out of the effective operating range for the turbo and it would become innefficient.
My point is that you could probably place the turbo where ever you wanted to and still achieve the same performance characteristics if the turbine was sized properly and performing in its operating range.
You could probably do a comparison as follows. All turbos have an efficiency map. They are more efficient at certain operating speeds and flow rates. A small turbo at the rear of the car operating at X flowrate may be more or less efficient than a large turbo in the engine bay operating at the same X flowrate. I'm gonna go check out som compressor maps.
You have a good point. If the air cools down TOO much, you might run out of the effective operating range for the turbo and it would become innefficient.
My point is that you could probably place the turbo where ever you wanted to and still achieve the same performance characteristics if the turbine was sized properly and performing in its operating range.
You could probably do a comparison as follows. All turbos have an efficiency map. They are more efficient at certain operating speeds and flow rates. A small turbo at the rear of the car operating at X flowrate may be more or less efficient than a large turbo in the engine bay operating at the same X flowrate. I'm gonna go check out som compressor maps.
Let use know if it looks feasible to do this with our engine. I think that turbine will surge before hitting top end.
I definitely would love to see it happen, I just don't see it working properly with ours.
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From: Mesa
The only things that really concern me:
Lots of piping and connection points = lots of potential leak points.
Road debris = possibility of a cut oil feed line (effects the turbo and the engine), damage to the turbo and all that piping.
Underbody air filter = no matter where you mount it under there it will be in a significanty more dirty and abusive environment than under the hood. Not to mention you would need to have the car on stands or a lift just to inspect/replace the filter.
Since its pretty non-evasive - I would be willing to try it out.
Lots of piping and connection points = lots of potential leak points.
Road debris = possibility of a cut oil feed line (effects the turbo and the engine), damage to the turbo and all that piping.
Underbody air filter = no matter where you mount it under there it will be in a significanty more dirty and abusive environment than under the hood. Not to mention you would need to have the car on stands or a lift just to inspect/replace the filter.
Since its pretty non-evasive - I would be willing to try it out.
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From: Gie
I just realized that these are COMPRESSOR maps and not TURBINE maps. Maybe a turbo expert can tell us if they are interchangable...I doubt that they are...
Anyways, if they were:
Lets hold constant at 120,000 RPM and try out two different flow rates (representing two different locations in the exhaust system).
TD04-13G (small)
Downstream 0.08 m^3/s: 1.72 @ 77%
Upstream 0.12 m^3/s: 1.53 @ 70%
TD04H-15G (large)
Downstream 0.08 m^3/s: 1.88 @ 67%
Upstream 0.12 m^3/s: 1.86 @ 76%
You can see that the 13G is more efficient for the lower flowrate (downstream) and the 15G is more efficient for the higher flowrate (upstream). Both operating at the same rotational speed and at similar efficiencies...
Again, this assumes that these maps are for turbines, not compressors, and that we are operating them backwards...can you do that???? It's interesting nonetheless.
Anyways, if they were:
Lets hold constant at 120,000 RPM and try out two different flow rates (representing two different locations in the exhaust system).
TD04-13G (small)
Downstream 0.08 m^3/s: 1.72 @ 77%
Upstream 0.12 m^3/s: 1.53 @ 70%
TD04H-15G (large)
Downstream 0.08 m^3/s: 1.88 @ 67%
Upstream 0.12 m^3/s: 1.86 @ 76%
You can see that the 13G is more efficient for the lower flowrate (downstream) and the 15G is more efficient for the higher flowrate (upstream). Both operating at the same rotational speed and at similar efficiencies...
Again, this assumes that these maps are for turbines, not compressors, and that we are operating them backwards...can you do that????
It's interesting nonetheless.