Turbocharged Engine exhaust Systems
Thread Starter
Turbocharged Engine exhaust Systems
Exhaust System Technology: Science and Implementation of High Performance Exhaust Systems
An interesting technical article on engines, which got me thinking about exhaust systems. There are numerous companies around the world who market header systems for naturally aspirated engines, some claiming anything up to 15% increase in Hp. But has anyone tried it with a turbocharged engine.
Looking at a typical Chieftain, Cirrus turbo engine shows the exhaust primary tube is a simple log type manifold. One would assume there would be loots of counterproductive interference with the exhaust pulses. I was wondering about the efficiency of these OEM exhausts and do they cause a little or significant increase in fuel consumption compared with a perfect header type system.
An interesting technical article on engines, which got me thinking about exhaust systems. There are numerous companies around the world who market header systems for naturally aspirated engines, some claiming anything up to 15% increase in Hp. But has anyone tried it with a turbocharged engine.
Looking at a typical Chieftain, Cirrus turbo engine shows the exhaust primary tube is a simple log type manifold. One would assume there would be loots of counterproductive interference with the exhaust pulses. I was wondering about the efficiency of these OEM exhausts and do they cause a little or significant increase in fuel consumption compared with a perfect header type system.
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
N/A engine needs a tuned length to scavage the exhaust gas out of the chamber to let the incoming change in. In a blower engine this is not require as it has a positive px that's why it's not as important the exhaust system is tuned It all about the inlet.
Cheers
Cheers
Thread Starter
Ok, I stand corrected. I had thought that but discarded it. So when you say inlet, are we talking about the inlet to the exhaust side of the turbo or the induction side of the engine as a whole?
Join Date: Jul 2007
Location: in the classroom of life
Age: 55
Posts: 6,864
Likes: 0
Received 1 Like
on
1 Post
The high claims for special exhausts are something that I take with a pinch of salt without back to back Dyno data.
As you can imagine I have some info on this from George Braly, one of the few folk who has actually done a fair bit of Dyno work on Piston Aero engines, and quite likely more than anyone else on the planet.
His discovery for several exhausts on NA TCM 6 cylinder engines is the torque peak moves around a bit, so at a particular RPM you get a small gain but lose it say at 2700.
When asked he refers people to the guys who buy up all the NA exhausts of Cirrus and Beech that buy them from TAT when they do a turbo upgrade.
Read between the lines
For Turbo engines all the best gains come from intercoolers and ones that are engineered with higher efficiency. Every turbo should not just have one but a good one. Problem is most will never get one coz the cost of paperwork and R&D.
Cheers
PS if Walter and JD wander past they might have some good first hand info to share.
As you can imagine I have some info on this from George Braly, one of the few folk who has actually done a fair bit of Dyno work on Piston Aero engines, and quite likely more than anyone else on the planet.
His discovery for several exhausts on NA TCM 6 cylinder engines is the torque peak moves around a bit, so at a particular RPM you get a small gain but lose it say at 2700.
When asked he refers people to the guys who buy up all the NA exhausts of Cirrus and Beech that buy them from TAT when they do a turbo upgrade.
Read between the lines
For Turbo engines all the best gains come from intercoolers and ones that are engineered with higher efficiency. Every turbo should not just have one but a good one. Problem is most will never get one coz the cost of paperwork and R&D.
Cheers
PS if Walter and JD wander past they might have some good first hand info to share.
Exhausts with turbocharged engines are a bit of a compromise.
In terms of heat energy you want the turbo to be as close to the engine as possible to minimise losses, and that usually means simple log-style manifold.
But in terms of pressure recovery you want a good straight length after the collector to help smooth out the pressure pulses that the turbine section receives, again for best power & efficiency.
A well-designed set of extractors (header is the US terminology) must be very difficult in an aeroplanes engine cowling due to the lack of room available. So a simple log-style of manifold is often used and they work just fine for the application.
In terms of heat energy you want the turbo to be as close to the engine as possible to minimise losses, and that usually means simple log-style manifold.
But in terms of pressure recovery you want a good straight length after the collector to help smooth out the pressure pulses that the turbine section receives, again for best power & efficiency.
A well-designed set of extractors (header is the US terminology) must be very difficult in an aeroplanes engine cowling due to the lack of room available. So a simple log-style of manifold is often used and they work just fine for the application.
The turbo needs energy in terms of heat, pressure, and velocity, its not px this is a myth that it require px, correct size tube in large tube out.
Join Date: Apr 2008
Location: Australia
Posts: 490
Likes: 0
Received 0 Likes
on
0 Posts
Fixed that for you
The velocity through the turbine comes from the difference in pressure from one side to the other. If you have no difference in pressure you can have the same or more energy (pressure, heat), but no rotation.
At 2700 rpm, the idea that gas flow restrictions in a manifold are a significant source of losses is ludicrous provided the manifold is adequately sized, you might just as well make it out of water pipe with right angle elbows. *
If you were running Four valves at 5000 rpm with much higher gas velocities it would be different.
* this begs the question of equal air fuel distribution which is a different matter.
If you were running Four valves at 5000 rpm with much higher gas velocities it would be different.
* this begs the question of equal air fuel distribution which is a different matter.
Andrew, PV = NRT where n is quantity, r is the universal gas constant and T is temperature.
work is the integral of P with respect to V
Hot high pressure gas at one side of the wheel, cold low pressure gas on the other side.
work is the integral of P with respect to V
Hot high pressure gas at one side of the wheel, cold low pressure gas on the other side.
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
The turbine in the turbo is an airfoil and the greater the velocity the faster it will spin. It's no different to a wing. Faster the airflow the greater the lift. It's not about px it velocity.
Cheers
Cheers
Join Date: Nov 2004
Location: Perth - Western Australia
Age: 75
Posts: 1,805
Likes: 0
Received 0 Likes
on
0 Posts
The greatest restriction in airflow in an IC engine is the intake port around the valve seat. This is why racing engines often have up to 5 different angles cut in the seat face, to ensure smoother flow.
Last edited by onetrack; 4th May 2014 at 09:20. Reason: spellink ...
Join Date: Apr 2007
Location: australia
Posts: 1,044
Likes: 0
Received 0 Likes
on
0 Posts
Sunfish suggest you study bgt namely GG and GH. V increase PX decrease temp decrease.
The scroll increase velocity into the turbine ( divergent duct ) iT moves across the turbine airfoil this creating rotation (ie lift ) then exits velocity decreases pressure increases temp increases.
Inlet side
Compressor opening is large into the comp it is compressed velocity is increased px decreased temp decreases as it passes through the scroll divergent now velocity decreases px increases temp increase
The compressed gas will only compress if the engine cannot use all of the flow that it is at it's use.
Simple basic gas.
Cheers
The scroll increase velocity into the turbine ( divergent duct ) iT moves across the turbine airfoil this creating rotation (ie lift ) then exits velocity decreases pressure increases temp increases.
Inlet side
Compressor opening is large into the comp it is compressed velocity is increased px decreased temp decreases as it passes through the scroll divergent now velocity decreases px increases temp increase
The compressed gas will only compress if the engine cannot use all of the flow that it is at it's use.
Simple basic gas.
Cheers
The 1971 book by Smith & Morrison " The scientific Design of Intake & Exhaust Systems" is still the bible.
The scientific design of exhaust and intake systems - Philip Hubert Smith, John Cruickshank Morrison - Google Books
The scientific design of exhaust and intake systems - Philip Hubert Smith, John Cruickshank Morrison - Google Books
