Bling Porn " WARNING GRAPHIC"
12-22-2010, 10:19 AM
#31
Race Car
Nice shiny parts….and since I just finished setting up the train under the Christmas tree I can give you the ‘engineers’ point of view – 
1) If you want to be truly accurate the two intercooler pipes need to be handled differently – when under boost the turbo to intercooler pipe will have air that is hotter than ambient engine bay temps, the intercooler to throttle pipe should have air that is cooler than ambient engine bay temps (once the engine bay is heat soaked). So if you want to be a true geek one side needs to be insulated and the other needs cooling fins.
2) Combustion does take place in the headers. If you are running a rich mixture – anything past mid 12’s – you will be still burning fuel in the headers.
1) If you want to be truly accurate the two intercooler pipes need to be handled differently – when under boost the turbo to intercooler pipe will have air that is hotter than ambient engine bay temps, the intercooler to throttle pipe should have air that is cooler than ambient engine bay temps (once the engine bay is heat soaked). So if you want to be a true geek one side needs to be insulated and the other needs cooling fins.
2) Combustion does take place in the headers. If you are running a rich mixture – anything past mid 12’s – you will be still burning fuel in the headers.
2. Excessive ignition retard will also cause this. The guys that drag race turbos use what is called a "2 step" ignition module to retard timing. This is also done with OBD II cars by OEM's at part of catalyst light off strategy. Finally, some folks will hook up a device to their clutch pedal such that when it is engaged, it will retard the timing. All of that works by running a lot more air through the engine at a given RPM, and effecitvely completing combustion in the header/manifold.
So now Lart you've heard from a few engineers.
12-22-2010, 12:49 PM
#34
1. Absolutely!!!! In my prior car, I used different materials, as well. ALuminum, which dissipates heat very well, on the turbo to IC side, and steel, which insulates (relative to aluminum) on the other side. I would speculate on most turbocharged cars, the intake air is cooler than the underhood temps. Which also means that polishing the outside of the intake manifold should help (on an academic basis).
2. Excessive ignition retard will also cause this. The guys that drag race turbos use what is called a "2 step" ignition module to retard timing. This is also done with OBD II cars by OEM's at part of catalyst light off strategy. Finally, some folks will hook up a device to their clutch pedal such that when it is engaged, it will retard the timing. All of that works by running a lot more air through the engine at a given RPM, and effecitvely completing combustion in the header/manifold.
So now Lart you've heard from a few engineers.
2. Excessive ignition retard will also cause this. The guys that drag race turbos use what is called a "2 step" ignition module to retard timing. This is also done with OBD II cars by OEM's at part of catalyst light off strategy. Finally, some folks will hook up a device to their clutch pedal such that when it is engaged, it will retard the timing. All of that works by running a lot more air through the engine at a given RPM, and effecitvely completing combustion in the header/manifold.
So now Lart you've heard from a few engineers.
As far as #2 goes, my original statement was meant to imply primary combustion, not secondary or incidental combustion. And as far as turbo applications go, creating an adiabatic system is a benefit, so ideally you'd try to keep as much heat from escaping the header pipes as possible, altho increasing heat thru secondary combustion is a hinderance to the pipe flow and should be avoided.
Porsche did an outstanding job designing the 951, from a fluid dynamics perspective. They didn't leave the intake and cam tower surfaces rough because they were too lazy to polish it, it was left that way for a reason.
And its still all academic, the differences in performance on a street car aren't going to make much difference.
Degreed in Math/Physics here, with 3.5 years of Mechanical Engineering (with an emphasis in Fluid Dynamic systems) school before changing my major.
12-22-2010, 04:26 PM
#35
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With reference to your last sentence in #1, you'd have to assume that the intake is an adiabatic boundry for this to be true. Its not, you get more thermal transfer from the cylinder head to the intake than you get from the engine compartment ambient temp to the intake, hence having surface area available to dissipate the engine heat is a greater benefit. Same thing goes for the IC pipe that attached to the turbo, except that it doesn't have the advantage of the rough surface of the intake, so they painted it black instead.
As far as #2 goes, my original statement was meant to imply primary combustion, not secondary or incidental combustion. And as far as turbo applications go, creating an adiabatic system is a benefit, so ideally you'd try to keep as much heat from escaping the header pipes as possible, altho increasing heat thru secondary combustion is a hinderance to the pipe flow and should be avoided.
Porsche did an outstanding job designing the 951, from a fluid dynamics perspective. They didn't leave the intake and cam tower surfaces rough because they were too lazy to polish it, it was left that way for a reason.
And its still all academic, the differences in performance on a street car aren't going to make much difference.
Degreed in Math/Physics here, with 3.5 years of Mechanical Engineering (with an emphasis in Fluid Dynamic systems) school before changing my major.
As far as #2 goes, my original statement was meant to imply primary combustion, not secondary or incidental combustion. And as far as turbo applications go, creating an adiabatic system is a benefit, so ideally you'd try to keep as much heat from escaping the header pipes as possible, altho increasing heat thru secondary combustion is a hinderance to the pipe flow and should be avoided.
Porsche did an outstanding job designing the 951, from a fluid dynamics perspective. They didn't leave the intake and cam tower surfaces rough because they were too lazy to polish it, it was left that way for a reason.
And its still all academic, the differences in performance on a street car aren't going to make much difference.
Degreed in Math/Physics here, with 3.5 years of Mechanical Engineering (with an emphasis in Fluid Dynamic systems) school before changing my major.
I have a polished intake on one of my old track cars – It made cleaning up the engine much easier – and I was always doing something to the engine. The smooth finish was much easier to care for and look a lot better.
In the good old days (60’s and before) most open wheel racers had chrome finishes on the A arms and suspension components so that they could be easily and quickly cleaned after a race. Then they found out that chroming can cause hydrogen embrittlement….no more shiny suspension parts!
12-22-2010, 08:59 PM
#36
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If I remember right the "2 step" module does something along the lines of killing every other cylinder when staged for the start of drag race. The first step I think is a chip set to your stage RPM (say...4200 rpm) and then a 2nd chip for your high speed ignition interupt.
That system especially helps the turbo guys as it's one less thing to worry about on the line when building boost.
I used MSD's electronic engine retard along with two stage nitrous systems in the past...that may have been what you were referencing 67?
That system especially helps the turbo guys as it's one less thing to worry about on the line when building boost.
I used MSD's electronic engine retard along with two stage nitrous systems in the past...that may have been what you were referencing 67?
2. Excessive ignition retard will also cause this. The guys that drag race turbos use what is called a "2 step" ignition module to retard timing. This is also done with OBD II cars by OEM's at part of catalyst light off strategy. Finally, some folks will hook up a device to their clutch pedal such that when it is engaged, it will retard the timing. All of that works by running a lot more air through the engine at a given RPM, and effecitvely completing combustion in the header/manifold.
So now Lart you've heard from a few engineers.
So now Lart you've heard from a few engineers.
12-23-2010, 12:34 AM
#37
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12-23-2010, 12:36 AM
#38
Race Car
With reference to your last sentence in #1, you'd have to assume that the intake is an adiabatic boundry for this to be true. Its not, you get more thermal transfer from the cylinder head to the intake than you get from the engine compartment ambient temp to the intake, hence having surface area available to dissipate the engine heat is a greater benefit. Same thing goes for the IC pipe that attached to the turbo, except that it doesn't have the advantage of the rough surface of the intake, so they painted it black instead.
As far as #2 goes, my original statement was meant to imply primary combustion, not secondary or incidental combustion. And as far as turbo applications go, creating an adiabatic system is a benefit, so ideally you'd try to keep as much heat from escaping the header pipes as possible, altho increasing heat thru secondary combustion is a hinderance to the pipe flow and should be avoided.
Porsche did an outstanding job designing the 951, from a fluid dynamics perspective. They didn't leave the intake and cam tower surfaces rough because they were too lazy to polish it, it was left that way for a reason.
And its still all academic, the differences in performance on a street car aren't going to make much difference.
Degreed in Math/Physics here, with 3.5 years of Mechanical Engineering (with an emphasis in Fluid Dynamic systems) school before changing my major.
As far as #2 goes, my original statement was meant to imply primary combustion, not secondary or incidental combustion. And as far as turbo applications go, creating an adiabatic system is a benefit, so ideally you'd try to keep as much heat from escaping the header pipes as possible, altho increasing heat thru secondary combustion is a hinderance to the pipe flow and should be avoided.
Porsche did an outstanding job designing the 951, from a fluid dynamics perspective. They didn't leave the intake and cam tower surfaces rough because they were too lazy to polish it, it was left that way for a reason.
And its still all academic, the differences in performance on a street car aren't going to make much difference.
Degreed in Math/Physics here, with 3.5 years of Mechanical Engineering (with an emphasis in Fluid Dynamic systems) school before changing my major.
As for why the intake is rough - no one polishes intakes, it is way too time consuming and expensive. If anything, they would have addressed the inside of the runners, rather than the outside. It is rough because it was sand cast. Nowadays, die casting is more common (at least for cam covers). No one roughs up those surfaces. I anything, they are powder coated (not painted due to environmental regulations), which would serve as an insulator. Of course, nowadays intakes are all plastic, so they are smooth and insulating!
Speaking of intakes, you give Porsche WAY too much credit. That intake, from a fluid dynamics perspective, is a textbook case of what NOT to do. You have runners wtih different geometries, you have more S curves than the Tail of teh Dragon without sufficient distance between changes of direction (4 times ID) and you have sharp bends (R<2 times ID) in several places. That intake was an exercise in packaging, not in fluid flow. I shudder just looking at the thing. It certainly wouldn't have gotten out of of my department, though that was 15 years after Porsche did this engine, and models are much more sophistocated (and emissions much more stringent).
There will be very little heat conducted from the turbo's housing to the intercooler pipe. That rubber is an extremely strong insulator, and there is a very small conductance path. The heat going into that pipes comes from the air flowing through it.
On the cold side pipe, it was painted black for aesthetics. Note Porsche did not paint the intercooler (many do, and old radiators used to be painted black, as well).
2 engineering degrees, though both in Materials. Professionally, I used to do engine development for Ford (7 years), which was more ME type of stuff.
12-25-2010, 12:11 AM
#43
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