What is Twinport ?

User Tag List

+ Reply to Thread
Results 1 to 14 of 14

Thread: What is Twinport ?

  1. #1

    Join Date
    13-12-2005
    Location
    Birmingham
    Age
    27
    Posts
    32,880
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    What is Twinport ?

    Twinport

    This question comes up now and again answers are mixed and occasionally confused due to sources on the internet not making sense.

    Basically this thread will describe what Twinport is, that is to say, just the Twinport technology, nothing else that is included on the new Twinport engines such as the enhanced EGR system, this is just about the Twinport mechanism, how it works and why it's used.

    Background on emissions


    The first point to note is that the engine has been designed to conform to emissions regulations and to be efficient and driveable. To ensure low emissions you want to reduce the amount of un-burnt fuel that goes through the exhaust. To ensure the maximum amount of fuel gets burnt it must have enough time in the cylinder to mix with the air, and it must have the right amount of air in the cylinder ideally a bit lean and with a good mixture composition. The amount of time is determined by engine speed, which is low for the emissions regulation checks. The volumetric efficiency of the air and the composition of the air-fuel mixture, is influenced heavily by inlet design. Now that you understand what is required to ensure low emissions you will have a better understanding of Twinport technology.

    What is it in simple terms?

    Twinport technology simply put involves partially blocking off one of the two inlet ports on each cylinder at low engine speeds. The 4 valve per cylinder engine design shows why there are two inlet ports.

    How does it work ?


    Twinport works by a spring loaded acctuator contracting at high rpm. At rest and low RPM the valve is left out. This acctuator controls (by way of a plastic rail) the 4 metal plates in each of the inlet port pairs.

    http://www.corsa-c.co.uk/gallery/fil...9/DSC00705.JPG

    My hand is controlling the spring loaded valve at this point, pushing it in moves the flaps up, letting it out let’s them fall to their default position.

    Default Closed position at low RPM < ≈ 3000


    http://www.corsa-c.co.uk/gallery/fil...9/DSC00701.JPG


    The pressure difference between the cylinder and inlet tract is what causes the air to rush towards the cylinder. As the inlet valve opens there is a vacuum in the cylinder compared with the ambient pressure, this causes air to rush in, thus filling the cylinder. This is why the air tries to travel with a constant mass flow rate. Mass flow rate is the product of air density, velocity and the area through which the matter is flowing. The area has clearly decreased through blocking off one port. Therefore to maintain a constant mass flow rate of air the velocity must increase.

    This faster moving air improves the low engine speed volumetric efficiency of the engine due to the increased inertia of the air (due to the increased velocity) resulting in greater amounts of air filling the cylinder after the piston has reached BDC. With the fixed cam timing on the engine after BDC as the piston rises air is forced out of the closing inlet valve. With increased air interia from the faster moving flow, air can continue to fill the cylinder or at least slow down the rejection of air from the cylinder, resulting in a greater amount of air in the cylinder during the compression phase.

    This faster moving air induces turbulence as it travels through the inlet pipework. Extra turbulence is caused by the blocked port. This excited turbulent air is easier to mix with fuel particles. This results in more air and more fuel being mixed at the same time (homogeneous mxiture). The more turbulent tumble of the air fuel mixture inside the cylinder also promotes a more turbulent flame front upon ignition which also improves the burn phase of the fuel and subsequently reduces emissions.

    This reduces emissions as un-burnt fuel containing hydrocarbons is not being wasted. Fuel economy increases, emissions drop and you can get a possible torque increase at low RPM compared to Non-Twinport. In this writers opinion it is other changes made to the newer engine through changed engine geometry, cam and head design which directly alter the peak bhp value.

    Midway
    http://www.corsa-c.co.uk/gallery/fil...9/DSC00703.JPG

    This picture is just showing the path the block off plate will take. Note the holes in the plate are to ensure that the air does not get backed up . If it were completely solid it may result in the airflow of the system being slower than is required. The holes in the plates allow for excess which has gone down the blocked off channel to vent around it. A solid plate might stall the airflow and could slow the neighbouring airThe transition between this phase and the next “open” phase happens almost instantaneously it is only to show the mechanism.


    Open – High RPM > ≈ 3000
    http://www.corsa-c.co.uk/gallery/fil...9/DSC00702.JPG

    At this engine speed the airflow is high enough to sustain proper air-fuel mixing, and any blockage reduces volumetric efficiency. This is combined with the fact that the engine speed is out of emissions testing regulations so it’s not required to provide perfect air-fuel ratio.
    Last edited by gtc; 05-01-2009 at 01:42.

  2. Remove Advertisements
    Corsa-C.co.uk
    Advertisements
     

  3. #2

    Join Date
    01-01-2007
    Location
    Winchester
    Age
    32
    Posts
    3,443
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Very interesting, thanks although I was aware of the priniples but not the specifics, did if you write it or get it from somewhere else?

    Depending on whether it's meant to be a layman's guide it might be worth rejigging/removing some of the more technical words though as some of the sentences I found hard to digest?

  4. #3

    Join Date
    10-02-2008
    Location
    Stevenston, Ayrshire
    Age
    23
    Posts
    4,950
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Thanks GTC

  5. #4

    Join Date
    13-12-2005
    Location
    Birmingham
    Age
    27
    Posts
    32,880
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I wrote it a while ago, but it got lost in the middle of a thread. There have been a few threads recently about Twinport and most end up in confusion between the advancements for the twinport engine and the actual twinport technology itself.

    If you highlight the problematic regions I can re-word them or add a glossary of some of the more technical terminology.

  6. #5

    Join Date
    01-01-2007
    Location
    Winchester
    Age
    32
    Posts
    3,443
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    Hiya gtc thanks for your post... I've just added a few rough comments, if they're not helpful as they are I can go into more detail... but I hope they come across ok at your end! But I should also point out I'm not bashing... all criticism is supposed to be constructive

    your post: (done outside a quote so italics work)
    Twinport

    This question comes up now and again answers are mixed and occasionally confused due to sources on the internet not making sense.

    Basically this thread will describe what Twinport is, that is to say, just the Twinport technology, nothing else that is included on the new Twinport engines such as the enhanced EGR system, this is just about the Twinport mechanism, how it works and why it's used.

    Background on emissions

    The first point to note is that the engine has been designed to conform to emissions regulations and to be efficient and driveable. To ensure low emissions you want to reduce the amount of un-burnt fuel that goes through the exhaust. To ensure the maximum amount of fuel gets burnt it must have enough time in the cylinder to mix with the air, and it must have the right amount of air in the cylinder ideally a bit lean and with a good mixture composition. The amount of time is determined by engine speed, which is low for the emissions regulation checks. The composition of the air and the amount of air is determined by volumetric efficiency, which is influenced heavily by inlet design.don't really get what this sentence is saying Now that you understand what is required to ensure low emissions you will have a better understanding of Twinport technology.

    What is it in simple terms?
    maybe mention something about 16 valveness here?
    Twinport technology simply put involves partially blocking off one of the two inlet ports for each cylinder at low engine speeds.

    How does it work ?

    Twinport works by a spring loaded valve contracting at high rpmshould that be 'an electronically actuated shutter closing at low rpm'. At rest and low RPM the valve is left out. This valve controls (by way of a plastic rail) the 4 metal plates in each of the inlet port pairs.the actuator controls the metal plates I think I'm having terminology issues lol



    My hand is controlling the spring loaded valve at this point, pushing it in moves the flaps up, letting it out let’s them fall to their default position.

    Default Closed position at low RPM < ≈ 3000




    The pressure difference between the cylinder and inlet tract is what causes the air to rush towards the cylinder. As the inlet valve opens there is a vacuum in the cylinder compared with the ambient pressure, this causes air to rush in, thus filling the cylinder. This is why the air tries to travel at a constant velocityI'd expect obstacles to make it travel faster, despite the obstacles. At this default closed position the inlet port surface area is greatly reduced. I was confused after this paragraph it was just a bit cumbersome not sure what it's telling me

    The air that is travelling, quite slowly (relatively) towards the cylinder travels down the port which is open. This air that would normally go slowly through the two ports has to speed up to keep the mass flow rate as near to constant as possible this improves low speed volumetric efficiency, however it also has other more important effects on the air flow.I got lost on the terminology again sorry!

    This increased velocity and subsequent induced turbulence caused by the blocked port and faster air speed enables the fuel and air to mix far more homogeneously. This basically means that as the air is excited by increased velocity and turbulence it is easier to mix with fuel particles. This results in more air and more fuel being mixed at the same time. The more turbulent tumble of the air fuel mixtureinside the cylinder also promotes a more turbulent flame front upon ignition which also improves the burn phase of the fuel. I'm with you now but I was thrown by the first sentence

    This reduces emissions as un-burnt fuel containing hydrocarbons is not being wasted. Fuel economy increases, emissions drop and you can get a possible torque increase at low RPM compared to Non-Twinport. In this writers opinion it is other changes made to the engine which directly alter the peak bhp value.this was the point I wondered who the writer was! Also isn't it the extra 75 or so cc that helps the peak power most?

    Midway



    This picture is just showing the path the block off plate will take. Note the holes in the plate are to ensure that the air does not get backed up into the inlet runners. If it were completely solid it may result in the airflow of the system being slower than is required. not sure what this means The transition between this phase and the next “open” phase happens almost instantaneously it is only to show the mechanism.


    Open – High RPM > ≈ 3000


    At this engine speed the airflow is high enough to sustain proper air-fuel mixing, and any blockage reduces volumetric efficiency. This is combined with the fact that the engine speed is out of emissions testing regulations so it’s not required to provide perfect air-fuel ratio.

  7. #6

    Join Date
    13-12-2005
    Location
    Birmingham
    Age
    27
    Posts
    32,880
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Twinport

    This question comes up now and again answers are mixed and occasionally confused due to sources on the internet not making sense.

    Basically this thread will describe what Twinport is, that is to say, just the Twinport technology, nothing else that is included on the new Twinport engines such as the enhanced EGR system, this is just about the Twinport mechanism, how it works and why it's used.

    Background on emissions

    The first point to note is that the engine has been designed to conform to emissions regulations and to be efficient and driveable. To ensure low emissions you want to reduce the amount of un-burnt fuel that goes through the exhaust. To ensure the maximum amount of fuel gets burnt it must have enough time in the cylinder to mix with the air, and it must have the right amount of air in the cylinder ideally a bit lean and with a good mixture composition. The amount of time is determined by engine speed, which is low for the emissions regulation checks. The volumetric efficiency of the air and the composition of the air-fuel mixture, is influenced heavily by inlet design. Now that you understand what is required to ensure low emissions you will have a better understanding of Twinport technology.

    What is it in simple terms?

    Twinport technology simply put involves partially blocking off one of the two inlet ports on each cylinder at low engine speeds. The 4 valve per cylinder engine design shows why there are two inlet ports.

    How does it work ?

    Twinport works by a spring loaded valve contracting at high rpm. At rest and low RPM the valve is left out. This valve controls (by way of a plastic rail) the 4 metal plates in each of the inlet port pairs.



    My hand is controlling the spring loaded valve at this point, pushing it in moves the flaps up, letting it out let’s them fall to their default position.

    Default Closed position at low RPM < ≈ 3000




    The pressure difference between the cylinder and inlet tract is what causes the air to rush towards the cylinder. As the inlet valve opens there is a vacuum in the cylinder compared with the ambient pressure, this causes air to rush in, thus filling the cylinder. This is why the air tries to travel with a constant mass flow rate. Mass flow rate is the product of air density, velocity and the area through which the matter is flowing. The area has clearly decreased through blocking off one port. Therefore to maintain a constant mass flow rate of air the velocity must increase.

    This faster moving air improves the low engine speed volumetric efficiency of the engine due to the increased inertia of the air (due to the increased velocity) resulting in greater amounts of air filling the cylinder after the piston has reached BDC. With the fixed cam timing on the engine after BDC as the piston rises air is forced out of the closing inlet valve. With increased air interia from the faster moving flow, air can continue to fill the cylinder or at least slow down the rejection of air from the cylinder, resulting in a greater amount of air in the cylinder during the compression phase.

    This faster moving air induces turbulence as it travels through the inlet pipework. Extra turbulence is caused by the blocked port. This excited turbulent air is easier to mix with fuel particles. This results in more air and more fuel being mixed at the same time (homogeneous mxiture). The more turbulent tumble of the air fuel mixture inside the cylinder also promotes a more turbulent flame front upon ignition which also improves the burn phase of the fuel and subsequently reduces emissions.

    This reduces emissions as un-burnt fuel containing hydrocarbons is not being wasted. Fuel economy increases, emissions drop and you can get a possible torque increase at low RPM compared to Non-Twinport. In this writers opinion it is other changes made to the newer engine through changed engine geometry, cam and head design which directly alter the peak bhp value.

    Midway



    This picture is just showing the path the block off plate will take. Note the holes in the plate are to ensure that the air does not get backed up . If it were completely solid it may result in the airflow of the system being slower than is required. The holes in the plates allow for excess which has gone down the blocked off channel to vent around it. A solid plate might stall the airflow and could slow the neighbouring airThe transition between this phase and the next “open” phase happens almost instantaneously it is only to show the mechanism.


    Open – High RPM > ≈ 3000


    At this engine speed the airflow is high enough to sustain proper air-fuel mixing, and any blockage reduces volumetric efficiency. This is combined with the fact that the engine speed is out of emissions testing regulations so it’s not required to provide perfect air-fuel ratio.


    Rev. 2

    Thanks for pointing things out, a lot of the points raised were needed as things i'd written were at best slightly confusing and at worst a complete mess. Put up anything else that looks out of order !

  8. #7

    Join Date
    13-12-2005
    Location
    Birmingham
    Age
    27
    Posts
    32,880
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Oh and i'm not sure about the acctuation of the rail. It's definatley spring loaded, i'm not sure if it works of pressure differentials or through an electric motor though

  9. #8

    Join Date
    01-01-2007
    Location
    Winchester
    Age
    32
    Posts
    3,443
    Mentioned
    1 Post(s)
    Tagged
    0 Thread(s)
    afaik it's an electric solenoid triggered by the ecu but I don't have a twinport myself to check! I'll have to read your revised version when I'm not asleep (almost) but thanks for taking my comments

  10. #9

    Join Date
    30-03-2010
    Age
    28
    Posts
    2
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    very interesting article, but the picture links are broken. Can you solve that problem? thanks

  11. #10

    Join Date
    29-05-2008
    Location
    Stirlingshire
    Age
    23
    Posts
    7,598
    Mentioned
    2 Post(s)
    Tagged
    0 Thread(s)
    Thread is over a year old, infraction ?

  12. #11

    Join Date
    30-03-2010
    Age
    28
    Posts
    2
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    ok the thread is one year old, but it contains some very useful information. If a new user enters the forum and is trying to find some information regarding twinport engines, it gets only text. Maybe those images are very important to explain some things.

  13. #12

    Join Date
    13-07-2007
    Location
    Portsmouth
    Age
    24
    Posts
    19,274
    Mentioned
    4 Post(s)
    Tagged
    1 Thread(s)
    Quote Originally Posted by aurelian17 View Post
    ok the thread is one year old, but it contains some very useful information. If a new user enters the forum and is trying to find some information regarding twinport engines, it gets only text. Maybe those images are very important to explain some things.
    But its still a year old.
    There is a rule about bumping old threads, hence why he infraction should happen.

  14. #13
    Koolaid_guy
    newbies again lol

  15. #14

    Join Date
    13-12-2005
    Location
    Birmingham
    Age
    27
    Posts
    32,880
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Hmmm I guess as my 'extra' membership ran out my CCUK gallery was deleted and so the links are dead. I'll try to upload them to photobucket when I get a chance, God knows if I still have the original pictures though.


    I know it's a year old but this should have been made a sticky a long time ago.

+ Reply to Thread

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

     

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts