A
Anonymous
Ehrmmm, cann't follow this theory, If reducing would increase power, then I would close them off completely. :shock:
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A
Anonymous
Ahhemm, ok, we go back to the basics 
Maximum airspeed is the soundbarrier. 300m/sec.
In the engine the minimum flowarea is just behind the valve, the throat. It is about 0.9 the valvediameter. This point should always be the smallest diameter in the airflow. The throat is just a bit smaller than the valve because it pushes just an extra bit of air into the cylinder just before the valve closes.
So let's start of from here:
1 cylinder equals 500cc
max rpm 7200= 60Hz = 30000cc/sec
300m/sec = 30000cm/sec
So optimal area 1cm2 + valvestemarea = 2cm2 = 16 mm
This works only in laminair airflow. Due to turbulence the actual startoff diameter should be 16/0.8= 20mm This is again a theoretical diameter and singlevalve intake.
More interesting is the airintake length with which an inductionforce caused by a pulsing airflow can push a little bit of extra air in the cylinder. this airflowpulse works just at a very small engine frequency. For optimal tuning this frequency should be chosen just above maximumtorque frequency.
This is all my personal view, as a fact I never decreased inlet diameters to increase power. always smoothed out and enlarged gradually. The bigger the valve the more power you get.
I could be wrong, please correct me.
Maximum airspeed is the soundbarrier. 300m/sec.
In the engine the minimum flowarea is just behind the valve, the throat. It is about 0.9 the valvediameter. This point should always be the smallest diameter in the airflow. The throat is just a bit smaller than the valve because it pushes just an extra bit of air into the cylinder just before the valve closes.
So let's start of from here:
1 cylinder equals 500cc
max rpm 7200= 60Hz = 30000cc/sec
300m/sec = 30000cm/sec
So optimal area 1cm2 + valvestemarea = 2cm2 = 16 mm
This works only in laminair airflow. Due to turbulence the actual startoff diameter should be 16/0.8= 20mm This is again a theoretical diameter and singlevalve intake.
More interesting is the airintake length with which an inductionforce caused by a pulsing airflow can push a little bit of extra air in the cylinder. this airflowpulse works just at a very small engine frequency. For optimal tuning this frequency should be chosen just above maximumtorque frequency.
This is all my personal view, as a fact I never decreased inlet diameters to increase power. always smoothed out and enlarged gradually. The bigger the valve the more power you get.
I could be wrong, please correct me.
Ask Ben!!!!
I just stick blowers on and cheat!!!
I know TWR experimented with the heads and I guess you can get the same volume of air at higher velocity as long as its less than maximum.
I guess this must also be linked modifications to the full inlet tract from a tuning perspective.
As to why a higher velocity is better at the same volume I have no idea - the simple science of more air plus more fuel = more power. Unless the air comes in so fast it compresses an increased number of molecules into the volume above the piston crown it's a mystery.
I'd have thought bigger to a point and polished was best - I'm sure Jainy would agree.
Mike
I just stick blowers on and cheat!!!
I know TWR experimented with the heads and I guess you can get the same volume of air at higher velocity as long as its less than maximum.
I guess this must also be linked modifications to the full inlet tract from a tuning perspective.
As to why a higher velocity is better at the same volume I have no idea - the simple science of more air plus more fuel = more power. Unless the air comes in so fast it compresses an increased number of molecules into the volume above the piston crown it's a mystery.
I'd have thought bigger to a point and polished was best - I'm sure Jainy would agree.
Mike
Ahhhhh.........the good old discussions of airflow theory.
Bigger is better went out in the 80's.........although some amatuers are still advocates.
The key behind velocity is to run as much as you can without choking flow. This is a tough task and takes a minds eye into the dynamics of flow. You either have it or you dont imo..........i've not seen any clueless people learn the trade after years of tuition.
The generic idea being that air carries a mass, and because its small the pulsing start-stop nature of the intake system requires the air flow to carry on moving even with the valve closed, generating localised areas of increased relative pressure. This then becomes beneficial upon the next valve event. When a valve opens on a high output engine, it opens whilst the piston is still on the tail end of the exhaust stroke. Common sense would make you think that a raising piston and exhaust gas pressure would have the intake charge turn around and head back up the port. So you have to work with local pressure relations and depressions, velocities of gasses moving towards and away from the chamber, pulse tuning (using harmonics) and have a port which is efficient in its own raw flow state.
However you get the case where people over simplify everything. ITs not just about pure CFM flow since thats all based on steady state testing and you can to an extent just keep enlarging a port until it flows like a drainpipe.......but then its just far too big and you will loose power despite what the flow graphs are telling you. The good head people will know where and how much to alter shapes, cross sectional areas, radii........where to add material not just remove it. The poor people will make a stock port look smooth and shiny, and thats it.
Whats eve more important nowadays is the accurate cutting and generation of complex valve seat geometry. The old 3 angle seat is in the toilet, and if you cut most modern performance heads with a generic 30-45-60 profile then you will loose flow since they come with more complex seat geometry from the factory. Just last week i was cutting a 5 angle, 3 radii and twin blend seat all in the space of 4mm height.
TWR sleeving like that is a nice looking solution, but isnt giving you the shape you want at all......its narrower so velocity at that part of the port is increased, but its not always where you want it........especially if the velocity then reaches an area of the port which cant turn the air with enough control.
The V6's ports are oversize, but necking them down using a sleeve method isnt the best idea. However the proper way to add material using A)epoxy isnt sexy
weld is highly expensive and traumatic on the parent ally casting and requires alot of work to get it back upto a servicable level after that much heat has been put into localised areas.
Either way your limited to a pretty crappy inlet manifold.
Bigger is better went out in the 80's.........although some amatuers are still advocates.
The key behind velocity is to run as much as you can without choking flow. This is a tough task and takes a minds eye into the dynamics of flow. You either have it or you dont imo..........i've not seen any clueless people learn the trade after years of tuition.
The generic idea being that air carries a mass, and because its small the pulsing start-stop nature of the intake system requires the air flow to carry on moving even with the valve closed, generating localised areas of increased relative pressure. This then becomes beneficial upon the next valve event. When a valve opens on a high output engine, it opens whilst the piston is still on the tail end of the exhaust stroke. Common sense would make you think that a raising piston and exhaust gas pressure would have the intake charge turn around and head back up the port. So you have to work with local pressure relations and depressions, velocities of gasses moving towards and away from the chamber, pulse tuning (using harmonics) and have a port which is efficient in its own raw flow state.
However you get the case where people over simplify everything. ITs not just about pure CFM flow since thats all based on steady state testing and you can to an extent just keep enlarging a port until it flows like a drainpipe.......but then its just far too big and you will loose power despite what the flow graphs are telling you. The good head people will know where and how much to alter shapes, cross sectional areas, radii........where to add material not just remove it. The poor people will make a stock port look smooth and shiny, and thats it.
Whats eve more important nowadays is the accurate cutting and generation of complex valve seat geometry. The old 3 angle seat is in the toilet, and if you cut most modern performance heads with a generic 30-45-60 profile then you will loose flow since they come with more complex seat geometry from the factory. Just last week i was cutting a 5 angle, 3 radii and twin blend seat all in the space of 4mm height.
TWR sleeving like that is a nice looking solution, but isnt giving you the shape you want at all......its narrower so velocity at that part of the port is increased, but its not always where you want it........especially if the velocity then reaches an area of the port which cant turn the air with enough control.
The V6's ports are oversize, but necking them down using a sleeve method isnt the best idea. However the proper way to add material using A)epoxy isnt sexy
weld is highly expensive and traumatic on the parent ally casting and requires alot of work to get it back upto a servicable level after that much heat has been put into localised areas. Either way your limited to a pretty crappy inlet manifold.
A
Anonymous
@BenR Ahaaa, as you might understand, Yes I'm from the 80's environment, (even before) also stopped with it halfway through the 80's.
Understand me right, I don't advocate to enlarge until you have a drainpipe, there is a relatioinship between valvesize, portsizes and airdisplacements.
And you don't want to know how much discussion I've had in the past with the shiny port people.
With the Vee I just pick up again on the NA tuning, with what I carry from the past.
Always want to know more so I'd like to discuss this matter more with you if you want. But I don't know if this thread is the place for it.
Since I have a spare engine to waste, I'd like to give it a go, as I understand you've got a workshop with the right tools?
I'd love to know more.
To put it in a nuttshell from what my knowledge is:
The valvethroat has the smallest area, from there on going outwards the opening angel of the port should be maximum 7 degrees, you would add material on flow areas where you exceed this, and enlarge radii on areas where you undermine it.
The valve seat design has always been delicate, but it is a bit cheap to say that the old way 30 45 60 wasn't the right way. It was just plain simple, we didn't have the equipment of today. It was al down to manual operated milling machines, which limited the possibilities.
And to you MikeT, this porting and stuff also relates to your turbo stuff if you want to get the max, so pay attention in the class :shock:
Understand me right, I don't advocate to enlarge until you have a drainpipe, there is a relatioinship between valvesize, portsizes and airdisplacements.
And you don't want to know how much discussion I've had in the past with the shiny port people.
With the Vee I just pick up again on the NA tuning, with what I carry from the past.
Always want to know more so I'd like to discuss this matter more with you if you want. But I don't know if this thread is the place for it.
Since I have a spare engine to waste, I'd like to give it a go, as I understand you've got a workshop with the right tools?
I'd love to know more.
To put it in a nuttshell from what my knowledge is:
The valvethroat has the smallest area, from there on going outwards the opening angel of the port should be maximum 7 degrees, you would add material on flow areas where you exceed this, and enlarge radii on areas where you undermine it.
The valve seat design has always been delicate, but it is a bit cheap to say that the old way 30 45 60 wasn't the right way. It was just plain simple, we didn't have the equipment of today. It was al down to manual operated milling machines, which limited the possibilities.
And to you MikeT, this porting and stuff also relates to your turbo stuff if you want to get the max, so pay attention in the class
:shock: Indeed mike! Less boost required, more efficient operation of chargers, lower charge temps, safer ignition control......less lag and more intentaneous torque.harry":19jpnbx5 said:@BenR Ahaaa, as you might understand, Yes I'm from the 80's environment, (even before) also stopped with it halfway through the 80's.
Understand me right, I don't advocate to enlarge until you have a drainpipe, there is a relatioinship between valvesize, portsizes and airdisplacements.
No problems Harry, i know you were not advocating this, i was merely pointing out the far too common trends of people that are not as specialised as they would like to think or advertise.
And you don't want to know how much discussion I've had in the past with the shiny port people.
Aswell have i...........its not such a problem anymore, its only really the Jap/chinese/thai/malaysian/some european/some american that still do it.........but nobody uses their heads anyway lol.
With the Vee I just pick up again on the NA tuning, with what I carry from the past.
Always want to know more so I'd like to discuss this matter more with you if you want. But I don't know if this thread is the place for it.
Were we not discussing this previously via email Mr.Bouma i presume?
Since I have a spare engine to waste, I'd like to give it a go, as I understand you've got a workshop with the right tools?
I'd love to know more.
Indeed, we have probably the most advanced cylinder head/valve seat/valve refacing equipment available to the public in the UK. As far as i was made aware, Williams F1 Engineering are the only other people with the same machine in the UK. You might also be interested in some V6 related developments we are pushing. Its a small market (read VERY small) so i havent at all put much effort into the engines.
To put it in a nuttshell from what my knowledge is:
The valvethroat has the smallest area, from there on going outwards the opening angel of the port should be maximum 7 degrees, you would add material on flow areas where you exceed this, and enlarge radii on areas where you undermine it.
Yes, the throat area just before the SSR has the smallest cross sectional area. The amount of degrees divergence all depends on how well you can control the seperation of flow using alternating total flow distances and velocity changes. The proprietry casting will have a great influence of the port, and extreem downdraught ports like the old BDG/YB style cosworths have been going out of fashion. A minds eye really helps, as mathmatical solutions each apply differently to different style ports, although there is probably one ultimate mathmatically perfect port if someone could fit it into an engine bay.
The valve seat design has always been delicate, but it is a bit cheap to say that the old way 30 45 60 wasn't the right way. It was just plain simple, we didn't have the equipment of today. It was al down to manual operated milling machines, which limited the possibilities.
Valve seat geometry along with valve head design has been the fastest moving area. Its all about accurate control, and manufacture of high quality concentric and well designed seat geometry. 30-45-60 seats were better than single angles (in a stock casting) but many were able to better that by hand manipulating the blend into the single 45 degree seat. And as we do now, we are able to control that blend with a sequence of radii, angles, concanve and convex. Manual operated mills replaced grinding stones, serdi type form tool carbide cutting replaced mills, and now like we have invested in, single point CNC countour cutting has replaced serdi type machines.........i say repalced, more like obliterated.
And to you MikeT, this porting and stuff also relates to your turbo stuff if you want to get the max, so pay attention in the class
BenR":2jg0ab48 said:
Really?
Blow out of your mouth with your lips tightened/puckered....
Now blow out with your mouth open...
The former gives colder air, and the later warm air therfore a large diameter decreasing to a small diameter intake speeds up the air (venturi effect) and makes it colder (1st year physics)...
Thats called the chill factor and its because your using high velocity air to evaporate moisture on your hands, which makes it feel cool.
Also the next thing you have to consider is that when you blow, your are moving air into a large volume of air itself. The nature of fluid dynamics will see you pickup ambient air to join the airflow you are generating. Air surrounding the column of air you are exhaling will not stay still. Blow out in cold weather and a perfect column of warm air does not stay straight nor does it carry on for more than a foot or two.
Plus you cannot replicate the velocities and pressure changes with your mouth, iirc its near impossible to generate even one PSI with your mouth.
Also the venturi effect isnt the act of velocity increasing with area decreasing, that is purely the law of conservation of energy. AS you decrease area and keep pressure constant, you will have a increase in velocity. The venturi effect explains the reduction in relative pressure across a reducing diameter restriction.
Also the next thing you have to consider is that when you blow, your are moving air into a large volume of air itself. The nature of fluid dynamics will see you pickup ambient air to join the airflow you are generating. Air surrounding the column of air you are exhaling will not stay still. Blow out in cold weather and a perfect column of warm air does not stay straight nor does it carry on for more than a foot or two.
Plus you cannot replicate the velocities and pressure changes with your mouth, iirc its near impossible to generate even one PSI with your mouth.
Also the venturi effect isnt the act of velocity increasing with area decreasing, that is purely the law of conservation of energy. AS you decrease area and keep pressure constant, you will have a increase in velocity. The venturi effect explains the reduction in relative pressure across a reducing diameter restriction.
A
Anonymous
Ok! BenR
The penny has dropped. Isn't this a small world?
So it limits my choise to one
I'm happy to get a confirmation about craftmenship the other way around.
Whell you know then where I come from. We will have some interesting discussion I presume.
Now I only need to find a bit of time to get the stuff out to you.
I'll try to work something out in the beginneng of the next year, since I also need to visit John Price.
The penny has dropped. Isn't this a small world?
So it limits my choise to one
I'm happy to get a confirmation about craftmenship the other way around.
Whell you know then where I come from. We will have some interesting discussion I presume.
Now I only need to find a bit of time to get the stuff out to you.
I'll try to work something out in the beginneng of the next year, since I also need to visit John Price.
Complex and interesting stuff (I used to study physics at postgrad level).
One of my freinds is midway through a PHd on the subject of mathematically modelling airflow (aeronautical applications).
It sounds like a VERY chaotic system in the inlet manifold. Does anybody (F1 etc) actually try to mathematically model it in its entirety, or even just in sections?
Peter
P.S. Good to hear some balanced thoughfull posts. With a Excellent lack of arguments.
One of my freinds is midway through a PHd on the subject of mathematically modelling airflow (aeronautical applications).
It sounds like a VERY chaotic system in the inlet manifold. Does anybody (F1 etc) actually try to mathematically model it in its entirety, or even just in sections?
Peter
P.S. Good to hear some balanced thoughfull posts. With a Excellent lack of arguments.
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