Exhaust temperature of RX-8
02-07-2007, 11:41 PM
#2
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02-08-2007, 09:31 AM
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There is a video in one of the threads here of the engine running without the exhaust manifold and it was shooting constant blue flames. That should be pretty damned hot.
02-08-2007, 10:44 AM
#5
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Right at the exhaust ports at full throttle you may see 1800*F but 2000*F isn't unheard of. The temps sensor on the cat says much less (around 1650*F or so) but there is a lot of heat lost in the exhaust system over a very short distance.
02-08-2007, 06:20 PM
#6
hot enough on my current tune to turn my custom 20/18 Ga T321 exhaust bright cherry red past the cat, towards where the trans ends, fortunately this cat can take over 1000 degC, Racing Beat claims the OE cat will fry over 1650 degF
the black HPC Extreme ceramic coating I had installed on the manifold has now turned a nice blue hue
the black HPC Extreme ceramic coating I had installed on the manifold has now turned a nice blue hue
02-08-2007, 06:26 PM
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Originally Posted by TeamRX8
Racing Beat claims the OE cat will fry over 1650 degF
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Last edited by Renesis_8; 09-11-2011 at 11:52 AM.
02-10-2007, 01:04 PM
#13
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With my custom exhaust sleeves on a 13B, the very first engine they ever went in had a T-04 on it. The turbine wheel was not inconel. It melted within a few minutes and folded the turbine blades over. The stock 13B exhaust sleeves expand to over double their area within the span of about 2". My sleeves hold the exhaust port shape and area constant and the header pipes are formed to match. They are smaller and higher velocity. I've seen temps of 2000*F with them.
02-10-2007, 01:34 PM
#14
Originally Posted by rotarygod
With my custom exhaust sleeves on a 13B, the very first engine they ever went in had a T-04 on it. The turbine wheel was not inconel. It melted within a few minutes and folded the turbine blades over.
What was going on there?
Last edited by MazdaManiac; 02-10-2007 at 05:25 PM.
02-10-2007, 08:58 PM
#16
Power!!
the temperature where steel starts to yield is much lower than the melting temp. It is also dependent on the forces it sees at a given temperature. As the temperature rises the meterial will yield faster for a given temp at doesn't necessary need to be near the melting temp.
Here's a quick chart to illustrate this. I don't know what the typical forces are on a spinning tubine vane but if it's in the 39 to 50K PSI range you could deform a 304 turbine vane at 1300 F.
2. Properties at elevated temperatures
All these values refer to 304 only.
304L values are not given because its strength decreases markedly above 425oC.
Time Elevated Temperature Tensile Strength
Temperature, oF 1112 1292 1472 1652 1832
Tensile Strength, PSI 55130 39171 24663 13057 7254
Creep data Stress for a creep rate of 1% in 10 000 h.
Temperature, oF 1022 1112 1202 1292 1472
Stress, PSI 174093 11606 7254 4352 1451
Here's a quick chart to illustrate this. I don't know what the typical forces are on a spinning tubine vane but if it's in the 39 to 50K PSI range you could deform a 304 turbine vane at 1300 F.
2. Properties at elevated temperatures
All these values refer to 304 only.
304L values are not given because its strength decreases markedly above 425oC.
Time Elevated Temperature Tensile Strength
Temperature, oF 1112 1292 1472 1652 1832
Tensile Strength, PSI 55130 39171 24663 13057 7254
Creep data Stress for a creep rate of 1% in 10 000 h.
Temperature, oF 1022 1112 1202 1292 1472
Stress, PSI 174093 11606 7254 4352 1451
02-11-2007, 02:38 AM
#18
Power!!
I don't know what the forces or metal surface temps are for the rotor housings. You could probably tell me. I would assume that the housings are cooled by the water jacket so that their surface temp does not reach the plastic region. That and the housings have more surface area than the turbine wheel blades so they distribute the load better. Also based on what I'm hearing from RG and what I know from my turbomachinery experience the hottest gas temps seem to be at the engine outlet. Which must be why they have inconel sleeves on the exhaust ports of the Renisis (understand we aren't talking about it but using it as analogy) but the rotor housing aren't nickel based.
Just to reiterate, my point was to say that you will see deformation of metal before you reach it's melting point based on the forces placed on it and the operating temperature of the metal. It's just physics.
Just to reiterate, my point was to say that you will see deformation of metal before you reach it's melting point based on the forces placed on it and the operating temperature of the metal. It's just physics.
02-11-2007, 03:38 PM
#21
Power!!
^^That helps too.
MM: I'm not much of a fabricator at all myself, I'm more of a machinist (milling and grinding specifically) who did some design work a long time ago. I have always had great respect for the art of welding and metal forming. Whatever system you have it works and I always appreciate your contributions and knowledge.
MM: I'm not much of a fabricator at all myself, I'm more of a machinist (milling and grinding specifically) who did some design work a long time ago. I have always had great respect for the art of welding and metal forming. Whatever system you have it works and I always appreciate your contributions and knowledge.
02-11-2007, 06:27 PM
#22
Registered
Originally Posted by MazdaManiac
Since its melting point is 1k°F less than steel, why doesn't aluminum of the rotor housings deform when confronted by 2000°F exhaust temps?
Racing Beat's aluminum side and intermediate housings are all aluminum, including the surfaces. They are nitride coated for wear resistance but that's it. They get all the heat. They don't melt because the cooling system does it's job. On Mazda's factory race peripheral port housings, the intake and exhaust ports are both just aluminum. The exhaust ports get blasted with this heat straight on uncoated aluminum. They don't melt because of the heat rejection from the coolant. Without coolant, the engine will literally melt inside.
02-11-2007, 07:43 PM
#23
I guess there are all kinds of physics going on with the movement of heat.
Cooling system or not, the combustion itself is 1600°F, so there is fluid at that temperature present at the surface of that aluminum.
There must be something in the dynamics of that energy transfer that keeps the aluminum from becoming plastic, despite the actual presence of that kind of heat.
In fabrication, you are above 9000°F , so melting is never an issue - it always happens!
Cooling system or not, the combustion itself is 1600°F, so there is fluid at that temperature present at the surface of that aluminum.
There must be something in the dynamics of that energy transfer that keeps the aluminum from becoming plastic, despite the actual presence of that kind of heat.
In fabrication, you are above 9000°F , so melting is never an issue - it always happens!
02-11-2007, 10:50 PM
#24
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Thread Starter
Good information. I was wondering about this because I have been studying the variable geometry turbo in the Turbo 911 as well as models made for diesel engines. All I have read indicates that the additional exhaust temp would make these problematic in the rotary and I did remember RotaryGod talk about the melted turbine. The movable vanning on the 911 seems overly complicated
http://paultan.org/archives/2006/08/...geometry-work/
so I was looking at a diesel design were the vanes do not rotate instead they are stationary and the housing sides up and down the vanes to increase or decrees the intake area. Only one moving part.
http://www.everytime.cummins.com/eve...sp?s=broadband
I just wonder if it would be as easy as making the vanes and turbine out of ceramic to eliminate the heat issue. As pointed out the housing will be saved by coolant.
These types of turbos are with out a doubt the future of turbo charging. They do what the 3rd generation RX-7 did with one turbo and a lot less weight and complexity. I would also bet better performance in the end.
http://paultan.org/archives/2006/08/...geometry-work/
so I was looking at a diesel design were the vanes do not rotate instead they are stationary and the housing sides up and down the vanes to increase or decrees the intake area. Only one moving part.
http://www.everytime.cummins.com/eve...sp?s=broadband
I just wonder if it would be as easy as making the vanes and turbine out of ceramic to eliminate the heat issue. As pointed out the housing will be saved by coolant.
These types of turbos are with out a doubt the future of turbo charging. They do what the 3rd generation RX-7 did with one turbo and a lot less weight and complexity. I would also bet better performance in the end.
02-11-2007, 10:55 PM
#25
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Thread Starter
Originally Posted by MazdaManiac
I guess there are all kinds of physics going on with the movement of heat.
Cooling system or not, the combustion itself is 1600°F, so there is fluid at that temperature present at the surface of that aluminum.
There must be something in the dynamics of that energy transfer that keeps the aluminum from becoming plastic, despite the actual presence of that kind of heat.
In fabrication, you are above 9000°F , so melting is never an issue - it always happens!
Cooling system or not, the combustion itself is 1600°F, so there is fluid at that temperature present at the surface of that aluminum.
There must be something in the dynamics of that energy transfer that keeps the aluminum from becoming plastic, despite the actual presence of that kind of heat.
In fabrication, you are above 9000°F , so melting is never an issue - it always happens!
I believe it is the fact that the aluminum is acting like a ferry moving the heat to the coolant never letting enough heat accurate in the metal to cause problems. Take want I say with a grain of salt, it's been a long time since I was sitting in a Thermodynamics class.