If we are talking N/A, square runners allow you to increase Area where it is needed the most. Depending on the approach angle we have from the airflow to the port, this flow is mostly done through the roof of the port duct (long side radius), at high lift values, therefore a square port allows more flow Area on said roof by being wider than an a Circle or even an Oval. However OEM tend to make a rectangle.... a rectangle!... which has the drawback of increasing port Area where we might not want it like the port floor, that is if we are chasing mostly high lift flow of course. Thats where port filling comes in to place, removing those slow moving regions of air (or maybe no air at all) on the port floor. All I just typed only comes to happen if we are able to achieve sufficient speed in the column of Air, which makes it carry a lot of Inertia and therefore making it not being able to turn on the short side radius and "escape" into the cylinder through the long radius and port roof. If we have a slow moving column of air (even at high lift), a square duct might be detrimental because we are putting Area on the roof where it is not needed, in this instance an Oval might be ideal because air tends to flow more through the center of the duct. I do agree the 90º angles of the square runners create high pressure zones and consequently low speed areas, slowing down the adjacent faster air molecules, but has almost anything in life thats a tradeoff we might have to endure, however, it might be ideal to round of the sides as you stated in the video., IF air is actually through therefore, if not its probably better to leave them, or fill them. The top horsepower guys do oval/round ports because they are a super efficient flow through shape, but maybe most importantly because they only care for a very narrow set of requirements from the engine, which OEM cannot, and out-of-production vehicle has to attend to a varied set of driver's inputs and be able to output reasonably well in all of them. I hope you can make the time for a nice answer, as I'm just starting to learn, I haven't even done one engine prep, my don't be fooled by the logo I present, I still dont even have a company, it's sort of a "I'll go through with learning porting and tuning, I can make this my bread maker, 'logo' type of mentality"!
Cheers for the comment. Lots to breakdown here. Firstly, all engines are boosted, there's no difference between NA or boosted. Only the pressure differential changes. Yes square runners increase CSA. But they increase drag so create dead areas. They aren't efficient and you are robbing the port of energy. No the flow isn't mostly done by the roof. Probe the head. The nucleus is our most active. Flow area doesn't equal mass flow. Best not to confuse the two. These is why smaller oval and big radius ports out flow and out perform small radius rectangular ports EVERYWHERE. And no you don't want to roof wider. You actually what it narrow, especially at the turn or you will create separation on the short side. No most OEM aren't rectangular, most are oval, especially most twin cams, even all the early chev ford aftermarket have all gone to big radius to improve port velocity and mass flow. The lift high or low matters not. A optimal port is an optimal port and the best ports have the biggest radius period. Two converging boundary layers will kill mass flow. Remember this. Lift has nothing to do with it. If you're "removing" the "slow" regions. You're removing the corner and replacing with a radius 👌 The speed of oir primary induction length is set by our MSCA and our average CSA. 690fps being max velocity @ MCSA And no, it's not "escaping" it's filling a low pressure. Remember, a high pressure will always fill a low pressure, that's what it's doing. When transitioning through the the turn. We actually need less area on the roof and more area on the short side. And no, this is one place we done want an oval. We actually need a Trapezoid shape. This allows for a maximised radial flow around a bend. Remember we need to trun the pressure front and keep the pressure stable and perpendicular to the port CSA. This is how you "turn" air. And no, the top guys do big radius, oval, round because it's the most effective EVERYWHERE! A rectangular port will be far more RPM limiting, meaning a far narrow power band then an oval port. And again, lots of OEM are oval. All your Toyota's, honda, nissan, BMW, etc as well as supercars, hypercars, etc all big radius oval. 👌 Spend some time reading up mate and get the basic down first. You will get there slowly. Take your time and learn how air behaves. This will have you greatly. Thx for the comment and effort you put in. 👍
Yeah, wow. Thats old 👌😉 , still a little square but in their day. Did good. I like the brodix SR20 head. Nice oval port. Good SSR and will make 1100hp on pump fuel fairly easy. Easy to port. Easy to build a decent intake for, too. We do lots of them.
Square gutter down pipes rust way quicker than round down pipes as dust builds up in the corners as they don't flow as well. Physics is physics.
Thats it!
If we are talking N/A, square runners allow you to increase Area where it is needed the most. Depending on the approach angle we have from the airflow to the port, this flow is mostly done through the roof of the port duct (long side radius), at high lift values, therefore a square port allows more flow Area on said roof by being wider than an a Circle or even an Oval. However OEM tend to make a rectangle.... a rectangle!... which has the drawback of increasing port Area where we might not want it like the port floor, that is if we are chasing mostly high lift flow of course. Thats where port filling comes in to place, removing those slow moving regions of air (or maybe no air at all) on the port floor.
All I just typed only comes to happen if we are able to achieve sufficient speed in the column of Air, which makes it carry a lot of Inertia and therefore making it not being able to turn on the short side radius and "escape" into the cylinder through the long radius and port roof. If we have a slow moving column of air (even at high lift), a square duct might be detrimental because we are putting Area on the roof where it is not needed, in this instance an Oval might be ideal because air tends to flow more through the center of the duct.
I do agree the 90º angles of the square runners create high pressure zones and consequently low speed areas, slowing down the adjacent faster air molecules, but has almost anything in life thats a tradeoff we might have to endure, however, it might be ideal to round of the sides as you stated in the video., IF air is actually through therefore, if not its probably better to leave them, or fill them.
The top horsepower guys do oval/round ports because they are a super efficient flow through shape, but maybe most importantly because they only care for a very narrow set of requirements from the engine, which OEM cannot, and out-of-production vehicle has to attend to a varied set of driver's inputs and be able to output reasonably well in all of them.
I hope you can make the time for a nice answer, as I'm just starting to learn, I haven't even done one engine prep, my don't be fooled by the logo I present, I still dont even have a company, it's sort of a "I'll go through with learning porting and tuning, I can make this my bread maker, 'logo' type of mentality"!
Cheers for the comment. Lots to breakdown here.
Firstly, all engines are boosted, there's no difference between NA or boosted. Only the pressure differential changes.
Yes square runners increase CSA. But they increase drag so create dead areas. They aren't efficient and you are robbing the port of energy.
No the flow isn't mostly done by the roof. Probe the head. The nucleus is our most active.
Flow area doesn't equal mass flow. Best not to confuse the two. These is why smaller oval and big radius ports out flow and out perform small radius rectangular ports EVERYWHERE.
And no you don't want to roof wider. You actually what it narrow, especially at the turn or you will create separation on the short side.
No most OEM aren't rectangular, most are oval, especially most twin cams, even all the early chev ford aftermarket have all gone to big radius to improve port velocity and mass flow.
The lift high or low matters not. A optimal port is an optimal port and the best ports have the biggest radius period.
Two converging boundary layers will kill mass flow. Remember this. Lift has nothing to do with it.
If you're "removing" the "slow" regions. You're removing the corner and replacing with a radius 👌
The speed of oir primary induction length is set by our MSCA and our average CSA. 690fps being max velocity @ MCSA And no, it's not "escaping" it's filling a low pressure.
Remember, a high pressure will always fill a low pressure, that's what it's doing.
When transitioning through the the turn. We actually need less area on the roof and more area on the short side. And no, this is one place we done want an oval. We actually need a Trapezoid shape. This allows for a maximised radial flow around a bend.
Remember we need to trun the pressure front and keep the pressure stable and perpendicular to the port CSA. This is how you "turn" air.
And no, the top guys do big radius, oval, round because it's the most effective EVERYWHERE! A rectangular port will be far more RPM limiting, meaning a far narrow power band then an oval port.
And again, lots of OEM are oval. All your Toyota's, honda, nissan, BMW, etc as well as supercars, hypercars, etc all big radius oval. 👌
Spend some time reading up mate and get the basic down first. You will get there slowly. Take your time and learn how air behaves. This will have you greatly.
Thx for the comment and effort you put in. 👍
Crane fireballs
Yeah, wow. Thats old 👌😉 , still a little square but in their day. Did good.
I like the brodix SR20 head. Nice oval port. Good SSR and will make 1100hp on pump fuel fairly easy. Easy to port. Easy to build a decent intake for, too. We do lots of them.
Love ya work Jake
cheers mate