valve shrouding

[Matra et Alpine]

Being a bastard is not cool
Being a bastard does not serve the purpose of this website
Being a bastard does not protray a wise man of your years!

good enough?

knew SOMEONE would nibble on the hook

Pointing out good engineering doesn't equate to being a bastard

We went over the porting stuff before. See you still stick with it.

Shark skin is NOT a good idea as it provides traps for fuel to turbulate and buidl up on the edges. NOT a good idea with a pteroleum mix as it will build up. Flow of a pure gas and flow of an atomised mixture are different things. So excepot for in cylinder injection then it's not clever.

What he MAINLY gets on is that genrally older castings for heads were unable to provide reasonale flow paths ( modern casting is less susceptbile to this ) and so had corners here eddy currents coudl form and these restricted the flow by constriction. But these are standard problems addressed by "normal" flowing of an intake ( and exhaust ). Only "amateurs" considered flowing a head was about taking things AWAY For getting that message across it's worth it. BUT to then take THAT to mean restricting makes better flow is an illogical and wrong step. MANAGING flow is important and at shapr corners the fastes gas flow is not the shortest route. People have actually known that for centuries as we watch rivers in spate


so, for example ......

bigger ports lose power. He explains all the reason behind this statement and points out that not a single engine has proof that it is only the bigger ports working to make more power. NOT A SINGLE ONE!

A classic partial truth hiding a lie
Nobody adds bigger ports without altering the flow charactersitics -- its' impossible.
SO he "defends" his blank/white view by claimin that it is something else doign the improvement.
NO amount of flow management on a constrictued input for a high revving engine will get enough fule/air mix in for a significant increase in power.
There are reasons that their is a calulation on optimal valve opening size for piston stroke/power and power requirments.
The valve is by definition a RESTRICTIVE opening as for weight reasons they are still all penny design -- rahter than sleeve, rotating or cone. You can flow as much as you like but at the end of the day if the valve doesn't open far enough it offers a restrictino and a back pressure which negates ALL the smarts you do ahead of it.
You will ALWAYS get small mprovements by his technique -- because he's effectively fixing the problems that mass production introduces into the ports. But many engines don't actually HAVE those problems nowadays -- and some even back in the 60s didn't

Porting is worht investigating in every engine and worth doign properly in many. He's 100% right there.
But to ignore the equal importance of valve size, opening and lift is just silly.

[hightower99]

knew SOMEONE would nibble on the hook

Pointing out good engineering doesn't equate to being a bastard

We went over the porting stuff before. See you still stick with it.

Shark skin is NOT a good idea as it provides traps for fuel to turbulate and buidl up on the edges. NOT a good idea with a pteroleum mix as it will build up. Flow of a pure gas and flow of an atomised mixture are different things. So excepot for in cylinder injection then it's not clever.

What he MAINLY gets on is that genrally older castings for heads were unable to provide reasonale flow paths ( modern casting is less susceptbile to this ) and so had corners here eddy currents coudl form and these restricted the flow by constriction. But these are standard problems addressed by "normal" flowing of an intake ( and exhaust ). Only "amateurs" considered flowing a head was about taking things AWAY For getting that message across it's worth it. BUT to then take THAT to mean restricting makes better flow is an illogical and wrong step. MANAGING flow is important and at shapr corners the fastes gas flow is not the shortest route. People have actually known that for centuries as we watch rivers in spate


so, for example ......

A classic partial truth hiding a lie
Nobody adds bigger ports without altering the flow charactersitics -- its' impossible.
SO he "defends" his blank/white view by claimin that it is something else doign the improvement.
NO amount of flow management on a constrictued input for a high revving engine will get enough fule/air mix in for a significant increase in power.
There are reasons that their is a calulation on optimal valve opening size for piston stroke/power and power requirments.
The valve is by definition a RESTRICTIVE opening as for weight reasons they are still all penny design -- rahter than sleeve, rotating or cone. You can flow as much as you like but at the end of the day if the valve doesn't open far enough it offers a restrictino and a back pressure which negates ALL the smarts you do ahead of it.
You will ALWAYS get small mprovements by his technique -- because he's effectively fixing the problems that mass production introduces into the ports. But many engines don't actually HAVE those problems nowadays -- and some even back in the 60s didn't

Porting is worht investigating in every engine and worth doign properly in many. He's 100% right there.
But to ignore the equal importance of valve size, opening and lift is just silly.

actually a one-way tiled pattern is the absolute optimum for the surfaces of the ports because it assures that no slow moving boundary layer exists and therefore the fuel stays in the air. It also lowers resistance to the flow and gets rid of some pumping loss. On top of all that being one-way means that it is harder for the pressure waves in the gas to change direction and they will be pushing into the engine harder and longer than they push out!

By the way I have no idea where you got the whole "reasonable flow path" bit which you say is his point. (It is not his point at all) In fact he states several times that the way he does it doesn't change any angles in the flow path! it simply reduces the volume and adds highvelocity without lowering flow! He also has gone about this whole thing in a very logical and creditable process (I have no idea where you think he makes all these wrong conclusions because firstly he doesn't make the ones you say and second he certainly has a total conclusion as to why it works!)

as to the second part of your post: He says that bigger ports do infact increase flow as measured on a flow bench but he says that this doesn't matter! the flow bench and any increases shown on it are irrelavent (You point this out so well that I wont say it again) He doesn't ignore valve timing lift and size at all infact he mentions it several times to be an important part. Also you say that valves are defined as a restrictive system well then flow doesnt matter does it! (no increase in flow would matter because the valve makes sure that only so much can come through) Velocity makes alot of sense now doesn't it! (as in with higher velocity more air can get past the valve before it closes!)

think about it like this flow is volume X time for CFM (cubic feet a minute) and velocity is distance X time for ft/sec if you have the same flow at a higher velocity then there is more kinetic energy in the air. If there is more kinetic energy then it can use more to squeeze past the valve!

[Matra et Alpine]

actually a one-way tiled pattern is the absolute optimum for the surfaces of the ports because it assures that no slow moving boundary layer exists and therefore the fuel stays in the air. It also lowers resistance to the flow and gets rid of some pumping loss. On top of all that being one-way means that it is harder for the pressure waves in the gas to change direction and they will be pushing into the engine harder and longer than they push out!

erm youve' got boundary layer wrong. It MINIMISE the boundary layer. the PROBLEM is that at each of the micro turbulences that exist -- they are what prevent a large boundary layer forming -- then for an atomised mixture those micro eddies create deposit points for the heavier components. What you have said is correct for a GAS. but fuel/air mix is NOT a gas.
The petrochemical industry spends billions each year pumping and moving gasses around distillation columns. They dont use that for the same reason !!
Your comment about one-way is strange too as it ignores that it is pressure that builds up and backs up in flows it is NOT gasses moving in the opposite direction ( well slightly beyond the inlet valve but it is in TURBULENT flow then anyway so the shark fin thing doesn't apply.

By the way I have no idea where you got the whole "reasonable flow path" bit which you say is his point. (It is not his point at all) In fact he states several times that the way he does it doesn't change any angles in the flow path! it simply reduces the volume and adds high velocity without lowering flow! He also has gone about this whole thing in a very logical and creditable process (I have no idea where you think he makes all these wrong conclusions because firstly he doesn't make the ones you say and second he certainly has a total conclusion as to why it works!)

He concentrates his results at where changes in direction occur and so he narrows it on the entry to direct the flow and optimise it. THAT was why I provided the analogy with rivers.

as to the second part of your post: He says that bigger ports do in fact increase flow as measured on a flow bench but he says that this doesn't matter! the flow bench and any increases shown on it are irrelevant (You point this out so well that I wont say it again) He doesn't ignore valve timing lift and size at all infact he mentions it several times to be an important part.

See that's why I'm confused (again)>
Before you said it was only the flow ????

Also you say that valves are defined as a restrictive system well then flow doesnt matter does it! (no increase in flow would matter because the valve makes sure that only so much can come through) Velocity makes alot of sense now doesn't it! (as in with higher velocity more air can get past the valve before it closes!)

I dont' see how you turn a valve opening which introduces a restriction and then somehow ignore that it ALSO has a flow path ? Velocity matters for sure. BUT it's not the be all and end all. Valves as restrictive systems have an optimal flow rate. GOING faster can actually make it WORSE by inducing HUGE eddies. Your comment above is right if we ignore that effect. And yet that effect is the BIGGEST issue at a valve opening

think about it like this flow is volume X time for CFM (cubic feet a minute) and velocity is distance X time for ft/sec if you have the same flow at a higher velocity then there is more kinetic energy in the air. If there is more kinetic energy then it can use more to squeeze past the valve!

NO!!
You are assuming all of the kinetic energy is applied to the positive.
Flowing a head is ALL about maximising the application of the kinetic energy in the flow towards to cylinder.
A restriction may cause stalling in the flow further behind the restriction.
I repeat we are talking about an atomised fuel/air mixture. These operate DIFFERENTLY from gasses. In eddies - anywhere, any size - atomised fuel will clump and then NOT flow as effectively OR burn as effectively. So at the limit, if you restrict a flow and speed it up then during that process you increase the pressure THAT can cause the atomisation of the fuel to coalesce and you end up with WORSE combustion.
These are all reasons why I repeat that it's NOT just about speeding it up by restricting. This isn't a couple of simple effects. There are many more than we've touched on so far too.

[derekthetree]

omg, flashback to the wieght distribution thread.

quick someone put in some lighthearted quips

[LotusLocost]

omg, flashback to the wieght distribution thread.

quick someone put in some lighthearted quips

Make love, not war

[LotusLocost]

Actually I have to reply to HT..

I can see you are writing, but do not understand why!!!!

If I ever should have to try this out on any engien, either in my racecar or my daily drive, I would have to concider it as an experiment.. Becaus of lack of evidence from you ( I would have believed you if you had something to show you know?!!!) and the fact that motoman uses this on motorbikes engiens for racing...

In experiment I mean that I would have to dyno the engien, and tune it for the change of flow characteristics etc etc... I simply can`t just put some epoxy in my inlets and think by myselfe: "ohh.. now I got 50 hp more in my engien... because motoman say so...!!"

And think about you "victim" in this case.. Paul who started this thread..
You don`t know his knowledge aboute engiens and tuning! And I think it`s wrong to convince him to belive this will give the best results for him! The lack of proof of reliability and results stabb you in the back! Again!.. I can clearly see that I have no chance in following you two in the physics department So don`t go over that again...
It works on the paper YES!!!
But to convince a guy who want to tune his engien a bit, to start an experimentation progress noone ever has done before!! Thats hars!! With two exceptions in the world yes: you, and motoman...(and some roadracing guys on his pages)


cheers

[Matra et Alpine]

Paul, as Quiggs says the VW forusm are best. You'll find lots of REAL experience of the heads you're usign and best advice.

ht, attached is chart from David Vizards book on the Mini and comparing the stadnard, flowed and flowed and large valves. You can CLEARLY see large valves made an improvement The Mini large valve work was based on Swaymar's development on the A-series engines and based pn THOUSANDS of tests. Most racing MG's and Mini's in the 60s, 70s and till today run one of Vizards setups or one based on it Not "theory" or a few tests. This is EXTENSIVE testing each with different profiles and results to identify the optimal.

I've hand-ported and "big valved" more '295 heads than I care to remember.

[paul]

im an engineer but do not work on car's that is my hobby mainly do gearing and lsd gearbox's for kit cars

so my head flowing knowelage is pretty sparce at the moment but im resonably qued up on my phisics of metal properties and air resistance etc...

so do have my queries about this filler work in your intake ports idea...

and if im going to be spending a hell of a load of man hours machining and fettliling my second head im not going to go for a design that in my mind actually does not seem to add up...

i will have to have a propper look on the vw vortex forums for some some advice on my exact head setup and what exactly i need to to do...

but if i can't get suffecent info manta ill be thinking of ox bow lakes

[hightower99]

erm youve' got boundary layer wrong. It MINIMISE the boundary layer. the PROBLEM is that at each of the micro turbulences that exist -- they are what prevent a large boundary layer forming -- then for an atomised mixture those micro eddies create deposit points for the heavier components. What you have said is correct for a GAS. but fuel/air mix is NOT a gas.
The petrochemical industry spends billions each year pumping and moving gasses around distillation columns. They dont use that for the same reason !!
Your comment about one-way is strange too as it ignores that it is pressure that builds up and backs up in flows it is NOT gasses moving in the opposite direction ( well slightly beyond the inlet valve but it is in TURBULENT flow then anyway so the shark fin thing doesn't apply.

Yes having a tiled pattern will only minimise the boundary layer but it will do so down to such a small amount that it really is gone compared to a smooth pipe. A tiled surface when done right will create high pressure areas (very small on there own and by high pressure we are talking 1-3psi more) uniformly around the whole surface. Any eddies created would be so small that the net amount of fuel taken from the air will be less then if it was in a smooth pipe where the fuel drops out of the air in the large slowmoving boundary layer. I am aware that atomised/vaporised fuel suspended in air reacts differently then if it was a gas but the air certainly follows all the rules. The petrochemical industry doesn't used tiled pipes because they are expensive to make and because they don't need them! umm about the one-way thing Pressure building up can only happen if the mass of gas increases, this happens by slowing down the gasses and in some cases (when the pressure wave travels back out of the system) the gasses will be going backwards! the tiled surface would make it harder for the gas to slow down and harder for it to change direction.

I dont' see how you turn a valve opening which introduces a restriction and then somehow ignore that it ALSO has a flow path ? Velocity matters for sure. BUT it's not the be all and end all. Valves as restrictive systems have an optimal flow rate. GOING faster can actually make it WORSE by inducing HUGE eddies. Your comment above is right if we ignore that effect. And yet that effect is the BIGGEST issue at a valve opening

Velocity matters is the point he is trying to make!!! by making the ports bigger you decrease velocity and that is bad! The big thing is that you can't really go too fast. You can have too much flow but you can't travel too fast! Velocity is a seperate variable then the optimum flow rate of the valve system!

NO!!
You are assuming all of the kinetic energy is applied to the positive.
Flowing a head is ALL about maximising the application of the kinetic energy in the flow towards to cylinder.
A restriction may cause stalling in the flow further behind the restriction.
I repeat we are talking about an atomised fuel/air mixture. These operate DIFFERENTLY from gasses. In eddies - anywhere, any size - atomised fuel will clump and then NOT flow as effectively OR burn as effectively. So at the limit, if you restrict a flow and speed it up then during that process you increase the pressure THAT can cause the atomisation of the fuel to coalesce and you end up with WORSE combustion.
These are all reasons why I repeat that it's NOT just about speeding it up by restricting. This isn't a couple of simple effects. There are many more than we've touched on so far too.

Yes it works like I said and no I am not assuming all the kinetic energy is applied to the positive! the whole point is to keep the same flow and increase velocity! this maximises the kinetic energy in the flow into the engine! also the eddies are so small that they could not hold much gas, certainly less than what sticks to the walls in a smooth pipe. Another thing to see is that I am not talking about restricting the flow at all!!! this isn't just sticking a plate in the port and saying "there you go!" this is about getting rid of dead volume in the ports...

If I ever should have to try this out on any engien, either in my racecar or my daily drive, I would have to concider it as an experiment.. Becaus of lack of evidence from you ( I would have believed you if you had something to show you know?!!!) and the fact that motoman uses this on motorbikes engiens for racing...

Yes go ahead experiment but it doesn't have to be as hard or trying as porting the engine. all you have to do is put the epoxy in but the engine back together, put it on a dyno and see if there is an improvement. There is no need for major testing as noone here is going to try to sell there services by using this system! Paul only has to prove it to himself and the best way is to do it. his engine will not take any damage at all, it will not take long to get a result and if it doesn't work for Paul then he can go the normal rute of porting and polishing! I am sorry for my lack of evidance but that shouldn't put anyone off from trying such a simple task! Motoman uses this stuff on more normal motorcycles then racing motorcycles!!!

And think about you "victim" in this case.. Paul who started this thread..
You don`t know his knowledge aboute engiens and tuning! And I think it`s wrong to convince him to belive this will give the best results for him! The lack of proof of reliability and results stabb you in the back! Again!.. I can clearly see that I have no chance in following you two in the physics department So don`t go over that again...
It works on the paper YES!!!
But to convince a guy who want to tune his engien a bit, to start an experimentation progress noone ever has done before!! Thats hars!! With two exceptions in the world yes: you, and motoman...(and some roadracing guys on his pages)

Paul would not be a victim if he tried it out! He would have earned some time with the internals of his engine and probably have done something else usefull at the same time. I am trying to convince Paul that there is no harm in trying something that worked so well for others and I am trying to tell him that it may well work better and cost less! And by the way this isn't some black art that only a few know of! along with me and motoman there are thousands of others who have tried it and have got it to work! Not to mention the guy who told motoman about it, some norwegion guy.

ht, attached is chart from David Vizards book on the Mini and comparing the stadnard, flowed and flowed and large valves. You can CLEARLY see large valves made an improvement The Mini large valve work was based on Swaymar's development on the A-series engines and based pn THOUSANDS of tests. Most racing MG's and Mini's in the 60s, 70s and till today run one of Vizards setups or one based on it Not "theory" or a few tests. This is EXTENSIVE testing each with different profiles and results to identify the optimal.

I've hand-ported and "big valved" more '295 heads than I care to remember.

Well the charts show nothing about velocity but I would guess that you actually got an increase if you enlarged the valves along with a port. The flow chart for just the porting doesn't mean much at all anyways as it isn't directly related to output power! If those results where measured on a flow bench then they don't matter much for power!

And to Paul: I can't and wont prove this to you. You can do it yourself over a weekend (not too hard at all) Just try it and nothing can go wrong!

[Matra et Alpine]

Yes having a tiled pattern will only minimise the boundary layer but it will do so down to such a small amount that it really is gone compared to a smooth pipe. A tiled surface when done right will create high pressure areas (very small on there own and by high pressure we are talking 1-3psi more) uniformly around the whole surface. Any eddies created would be so small that the net amount of fuel taken from the air will be less then if it was in a smooth pipe where the fuel drops out of the air in the large slowmoving boundary layer.

I still think you are thinking GAS and not atomised fuel
A boundary layer can be advantageous as it will be air ( because the fuel will have been drawn out back into the atomised flow or down onto the pipe )
So once flowing it can be beneficial to the improved flow and retention of atomisation of the fuel/air mix.

I am aware that atomised/vaporised fuel suspended in air reacts differently then if it was a gas but the air certainly follows all the rules.

If 25% of an atomised fuel/air mix clumps and drops out of the flow or then fails to burn as quickly once ignited then YOU LOSE POWER.
I feel you are defending the physics of a gas flow and losing sight of the most important feature and that is to deliver as finely atomised consistent fuel/air mix INTO the cylinder for optimal combustion.

The petrochemical industry doesn't used tiled pipes because they are expensive to make and because they don't need them!

You think ?
Every 3 years the petro chemical industry has to take a cracker OUT OF PRODUCTION for about 3 months to repair and replace valves and pipes.
IF they could make it less often by preventing sludge build up and wear from flow then they would -- losing £5million PER DAY PROFIT is bad news. Equally if you can improve flow by 10% then crudely you can increase production by 10% and add another £0.5million PER DAY PROFIT.
( Made didn't turn up at the pub the other night, so it will need to wait for all the numbers and math from a professional till later )

umm about the one-way thing Pressure building up can only happen if the mass of gas increases, this happens by slowing down the gasses and in some cases (when the pressure wave travels back out of the system) the gasses will be going backwards!

Beyond the valve area can you please show me a diagram of how you think gas is "moving" ?? A pressure wave can move backwards along a pipe whilst ALL the gases are moving forward. Valve overlap Can cause vavle outflow as the valve opens at the end of the exhaust cycle but generally is not good ( the overlap is really timed to get the exhaust gas exit speed to "draw" the opening inlet )
Are you sure you've explained what you're thinking properly ?

the tiled surface would make it harder for the gas to slow down and harder for it to change direction.

Let's imagine for a moment that you DID have a gas moving backwards ( as opposed to stalling bu pressure ) THEN your shark fin theory crumbles. These only work in relatively smoothly and consistent moving flows. Have you evaluated HOW the shark fin idea works so well ?

Velocity matters is the point he is trying to make!!! by making the ports bigger you decrease velocity and that is bad!

GO look at the charts.
MORE POWER from larger valves. That was why I shared it. You were blindly repeating big valves bad -- I've shown big valves good and based on work from the GODS of motor tuning
You've clearly forgotten the basic REASON for delivering fuel/air mix
BY mismatching valve size he's right. There is NO point going beyond the calculation for valve opening ( by diameter and lift )

The big thing is that you can't really go too fast. You can have too much flow but you can't travel too fast! Velocity is a seperate variable then the optimum flow rate of the valve system!

You can't go any "faster" on delivery of fuel/air mix than the downstroke pressure of the piston creates ( excluding ram air and chargers )
The rest of it is about controlling flow.
Like all things there is a limit on how small you can get -- AGAIN especially with a non-gas. Higher pressure on an atomised mix causes it to clump out.
Fuel/air burns optimally in an ideal atomised mix. Once you lose it it's impossible to recreate it

Yes it works like I said and no I am not assuming all the kinetic energy is applied to the positive! the whole point is to keep the same flow and increase velocity! this maximises the kinetic energy in the flow into the engine!

erm, time to go study Physics.
Sorry man you CANNOT increase kinetic energy in a flow.
You are suggesting you can INCREASE the energy in something without the addition of an external energy source.
That's impossible.
Who said it increases kinetic energy ?
What unit were they measuring by ?

also the eddies are so small that they could not hold much gas, certainly less than what sticks to the walls in a smooth pipe.

Sperry man, you're STILL thinking gas.
It is not a gas that is being transported.
I'm fed up telling the obvious.
It's a fuel/air MIX.
Atomised mixes do NOT operate as gas because you have a partial liquid in suspension in a gas. Different rules apply.

Another thing to see is that I am not talking about restricting the flow at all!!! this isn't just sticking a plate in the port and saying "there you go!" this is about getting rid of dead volume in the ports...

Wait, you were going on about narrowing the ports at points to increase the flow ? make your mind up> I had already said that any decent head has already god rid of dead areas now that casting is more capable. Go look at a Lotus Twin Cam head from the 60s GOOD engines back then were doing it. I concur that crappy heads can be improved. BUT hat's not what you seem to have been defending as you have said it can work all the time.

I am sorry for my lack of evidance but that shouldn't put anyone off from trying such a simple task! Motoman uses this stuff on more normal motorcycles then racing motorcycles!!!

Caveat emptor to anyone wanting to "experiment".
Get the mix wrong or use the wrong epoxy mix and you risk some of it breaking away.
That getting in the valve as it CLOSES will risk punching the now stuck valve through a piston.
All for folks experimenting BUT suggesting anyone should try this without potentially knowing the risks of engine destruction is foolish.
DONT DO THIS GUYS unless you know your material science to get the right epoxy AND dont mind losing a complete engine if it goes wrong !!!
Oh and bike engines are a LOT different from car engines at the engineering and risk level

Paul would not be a victim if he tried it out! He would have earned some time with the internals of his engine and probably have done something else usefull at the same time. I am trying to convince Paul that there is no harm in trying something that worked so well for others and I am trying to tell him that it may well work better and cost less!

And for the reason given above. I'm giving the PRACTICAL warning that is COMPLETELY MISSING AND frankly rather sloppily ignored by you

Well the charts show nothing about velocity but I would guess that you actually got an increase if you enlarged the valves along with a port. The flow chart for just the porting doesn't mean much at all anyways as it isn't directly related to output power! If those results where measured on a flow bench then they don't matter much for power!

You DO know you can measure MORE FLOW on a bench and end up with less power because of stalling ?
IN a real engine the energy to make the fuel/air mix flow is from the piston intake cycle. So it's not as black and white as you think or demonstrate here.
BUT the ULTIMATE measure of the performance of a tuning input to an engine is it's power OUTPUT.
THAT's what I gave you.
Does it MATTER if the flow in the option 3 is faster or slower ? It generate MORE engine output than the 1000 other tests they tried on the '295 head.

And to Paul: I can't and wont prove this to you. You can do it yourself over a weekend (not too hard at all) Just try it and nothing can go wrong!

Will you pay Paul for any damage to his VW block and pistons if it goes "wrong" ?
There is a risk and you are stupidly ignoring it and constantly repeating this "nothing wrong" BS.
I've seen paddocks full of engines busted by incompetence -- I've had to strip and repair a few too. The most recent a Coventry CLimax with a carb washer ingested -- made pretty patterns in the piston and block

[hightower99]

First I would like to say that I can understand why someone could get confused when reading my last post (using the word gas for gasoline and gas(the state of matter))

I still think you are thinking GAS and not atomised fuel
A boundary layer can be advantageous as it will be air ( because the fuel will have been drawn out back into the atomised flow or down onto the pipe )
So once flowing it can be beneficial to the improved flow and retention of atomisation of the fuel/air mix.

I am not thinking of a pure gas(state of matter) flow, I know that atomised/vaporised gasoline/benzine react and follow seperate rules even though they are suspended in a gas(state of matter). Boundary layer(s) are never beneficial, they create increased pumping loads via higher fludic resistance. A boundary layer will be slower moving and higher pressure then the fast moving air. As soon as the atomised fuel hits the boundary layer it will suddenly clump and hit the wall!

If 25% of an atomised fuel/air mix clumps and drops out of the flow or then fails to burn as quickly once ignited then YOU LOSE POWER.
I feel you are defending the physics of a gas flow and losing sight of the most important feature and that is to deliver as finely atomised consistent fuel/air mix INTO the cylinder for optimal combustion.

the situation you talk about here is true but it would not happen if you used a one-way tiled surface. Did I mention that boundary layers subdue turbulance and you need turbulance to keep the heavier than air fuel suspended in the air!

Beyond the valve area can you please show me a diagram of how you think gas is "moving" ?? A pressure wave can move backwards along a pipe whilst ALL the gases are moving forward. Valve overlap Can cause vavle outflow as the valve opens at the end of the exhaust cycle but generally is not good ( the overlap is really timed to get the exhaust gas exit speed to "draw" the opening inlet )
Are you sure you've explained what you're thinking properly ?

by "moving" I meant that the point of highest average mass travels backwards (this is also the place where the highest pressure is) and that in most engines the air (having a certain mass) is still traveling forwards even as the valve closes, the flow of air will hit the valve and "bounce" backwards creating low pressure just behind the valve and a high pressure wave that will travel back until it is neutral again but now there is still the low pressure spot just behind the valve that pulls the air back towards it. Good valve timing will take advantage of this returning pressure wave. Lamborghini has a variable length intake system to help with this.

Let's imagine for a moment that you DID have a gas moving backwards ( as opposed to stalling bu pressure ) THEN your shark fin theory crumbles. These only work in relatively smoothly and consistent moving flows. Have you evaluated HOW the shark fin idea works so well ?

First it isn't shark fin it is shark skin (as in scales) a better description is one-way partially overlapping tiled surface... and second I don't quite understand what you mean... the tiles are one-way to hold any positive pressure behind the valve longer and to shorten the time of the negative (going away from the engine) pressure wave.

GO look at the charts.
MORE POWER from larger valves. That was why I shared it. You were blindly repeating big valves bad -- I've shown big valves good and based on work from the GODS of motor tuning
You've clearly forgotten the basic REASON for delivering fuel/air mix
BY mismatching valve size he's right. There is NO point going beyond the calculation for valve opening ( by diameter and lift )

I looked at the charts and there is no mention of output power anywhere. Those are charts of intake and exaust flow at different lift heights... no power!!! so my statement stands those charts do not nessarily mean more power. I said nothing about big valve being bad. I said large volume ports are bad! Big valves help increase the optimum flow... porting without changing valve size will lead to a decrease in power!

[Matra et Alpine]

First I would like to say that I can understand why someone could get confused when reading my last post (using the word gas for gasoline and gas(the state of matter))

Cheers, I wasn't thinking of the US v the world difference on gas
But ...

As soon as the atomised fuel hits the boundary layer it will suddenly clump and hit the wall!

Which actually in a continuous flow makes the boundary layer contain LESS atomised fuel, more air. BUT how long it stayds is up for (long) debate

the situation you talk about here is true but it would not happen if you used a one-way tiled surface. Did I mention that boundary layers subdue turbulance and you need turbulance to keep the heavier than air fuel suspended in the air!

Depends on injection point and air flow rates and a million other things.
Byt REDUCING the port size though it makes cl;umping more likely
Turbulence ONLY comes from speed at the boundary layers and NOT inside the flow. So I still contend the guys theories are riddled with holes in teh real world car engines of today.

by "moving" I meant that the point of highest average mass travels backwards

That's better.

Good valve timing will take advantage of this returning pressure wave. Lamborghini has a variable length intake system to help with this.

Correct and Yamaha EX-UP valve does the same on the exhaust side

First it isn't shark fin it is shark skin (as in scales)

Yeah that was a brain fart. Meant skin, swimming with them last week has had an effect on my main recognition factors

the tiles are one-way to hold any positive pressure behind the valve longer and to shorten the time of the negative (going away from the engine) pressure wave.

Confused again. Shark skin ONLY works as long as the air os movign in the right direction. You seem to WANT to clim advantage of reverse pressure ( which is really only a mean slowing of the moving fuel/air so perhaps you can explain how you think it works ) yet you make out like it affects the PRESSURE wave. It can't affect pressure, it can only affect flow. I thought you said above you realised it was NOT reverse flow of a fuel/air mix. You're confused. Please try again Who told you about this shark skin in pipes ? You got a link to a reference material and save confusing it further with yoru interpretation. It is probably best at this time I read the source to get the point. So far all I'm getting is confused an dcontradictory answers and it's not helping

I looked at the charts and there is no mention of output power anywhere. Those are charts of intake and exaust flow at different lift heights... no power!!!

MY bad.
Sorry, I scanned the wrong pages from the book
I meant to scan the power charts. I'#ll get them later -- need to get book BACK from person who has it borrowed and "borrow" it again. ( SOmetimes I think I shold keep my library locked -- and my tools )

so my statement stands those charts do not nessarily mean more power. I said nothing about big valve being bad. I said large volume ports are bad! Big valves help increase the optimum flow... porting without changing valve size will lead to a decrease in power!

Sorry my mistake, I took a comment earlier to mean large valves.
Let's not go back over that. Fine you meant large ports bad. So explain line 2 of the charts ? It increased the port cross section

[hightower99]

Which actually in a continuous flow makes the boundary layer contain LESS atomised fuel, more air. BUT how long it stayds is up for (long) debate

Umm the boundary layer makes fuel clump together and hit the port walls. So what if the boundary layer will contain les fuel than air, this is also bad because it leans out the air/fuel mix. The boundary layer will let the fuel drop and hit the wall it will then hold the fuel there as it is slower and higher pressure than the main flow it will act like a wall.

Depends on injection point and air flow rates and a million other things.
Byt REDUCING the port size though it makes cl;umping more likely
Turbulence ONLY comes from speed at the boundary layers and NOT inside the flow. So I still contend the guys theories are riddled with holes in teh real world car engines of today.

Yes it does depend on other things but one of them (an important one) is turbulance. Turbulance comes from the surface of the wall of the port, if it is smooth you get a large thick boundary layer (bad) if it has some sort of roughness it will have irregular turbulance and if it is tiled then you have organised micro turbulance that keeps eveything flowing. Reducing the volume of the port will not make clumping more likely at all (slightly lower pressure due to higher velocities, more turbulance to keep the fuel atomised) By the way turbulance also comes from pressure differances and from any restrictions before it gets to the ports. Motoman's theories are justified and proven to work.

Confused again. Shark skin ONLY works as long as the air os movign in the right direction. You seem to WANT to clim advantage of reverse pressure ( which is really only a mean slowing of the moving fuel/air so perhaps you can explain how you think it works ) yet you make out like it affects the PRESSURE wave. It can't affect pressure, it can only affect flow. I thought you said above you realised it was NOT reverse flow of a fuel/air mix. You're confused. Please try again

I am not confused at all you are the one who is confused. when the flow is in the right direction then the tiled surface will have less resistance then if it was a smooth pipe. When the mass bounces back it will meet lots of restriction. The tiles effect the mass of air and indirectly the pressure.

Fine you meant large ports bad. So explain line 2 of the charts ? It increased the port cross section

Line 2 on the charts shown shows an increase in flow as almost all porting does. However this flow is measured under the same situations that are in phase 2 of intake, Intake suction. This means that anyflow increase measured will not mean an increase of air in the cylinder. The more important phase is the one right after called the Intake Charging phase. This is where the piston is at the bottom of it's stroke and the air (if it has a high enough velocity) will continue to travel into the cylinder. As the piston comes up and the intake valve starts closing the air/fuel mix is still coming in and this is where velocity makes itself felt!

[hightower99]

Read this article here It explains in clear detail why porting heads is almost always bad and why increasing velocity is almost always good...

[Matra et Alpine]

When the mass bounces back it will meet lots of restriction.

I stopped reading and aren't even bpthered to write any more.

You did it again. You've got MASS MOVING BACKWARDS ?

You're all messed up either in teh telling or the basic understanding.
I've tried too many times to "help" explore it

Give me a link and I'll come back --maybe !!
[quote]The tiles effect the mass of air and indirectly the pressure.[/quote}No it does't
The "mass" is determined by the intake stroke of the piston.
Give me a link by an engineer please.
I'm struggling to keep a straight mind and face