Lower Intake Design

XR7 Dave said:
Split port heads have horribly small exhaust ports and the walls on the intake ports are very thin which means they can't be ported much. By the time you consider the amount of work necessary to fit them to an M90, porting a set of SC heads nets more gains for less money. Well ported SC heads are every bit the equal of split port heads. Some would argue they are better for high performance, even after porting both.

There is no loss of lower end with a high lift cam, you've been mislead. ;) With any camshaft design, intended rpm range is definitely important though so point taken. Many cams are not designed right for the application and the results can be very disappointing.
Click to expand...

You're right on the size of the exhaust ports in the split port.....they are pretty small. Aren't SC exhaust ports a D shape? I seem to remember seeing them as that sort of shape.
 
Splitport have their place. If your looking to go turbo and want 600rwhp they are best bang for the buck because they will support that on moderate boost psi. Also I don't think the smaller exhaust port makes a big difference anyways because you have the piston forcing the exhaust gas out of the hole. That debate will go on forever.
 
JT's03 said:
Splitport have their place. If your looking to go turbo and want 600rwhp they are best bang for the buck because they will support that on moderate boost psi. Also I don't think the smaller exhaust port makes a big difference anyways because you have the piston forcing the exhaust gas out of the hole. That debate will go on forever.
Click to expand...

Another thing about the split port when I ported/ polished mine, is that the low end torque runner appears to be the weak spot. I don't know if it was intentional by Ford to have the low end torque runner snake through with a bend to build up torque, or whether it was a design limitation or not, but the high rpm runners have a straight through design that appears to be more effective.
 
I'd found this--a guy who had put an Eaton M90 on his 5.0 LTD LX and flow tested his setup......thought it would be a good addition to this thread. If someone really had the time, they could take a spare supercharger/ manifold/ intercooler/ tubing and then see what happens.

 
1FSTBRD said:
Another thing about the split port when I ported/ polished mine, is that the low end torque runner appears to be the weak spot. I don't know if it was intentional by Ford to have the low end torque runner snake through with a bend to build up torque, or whether it was a design limitation or not, but the high rpm runners have a straight through design that appears to be more effective.
Click to expand...

It snakes to make it longer. It's longer to lower the speed it works best at.

Longer runners == better low end performance due to tuning. Shorter runners == poorer low end, better high end. Split ports == an attempt at both worlds.

RwP
 
RalphP said:
It snakes to make it longer. It's longer to lower the speed it works best at.

Longer runners == better low end performance due to tuning. Shorter runners == poorer low end, better high end. Split ports == an attempt at both worlds.

RwP
Click to expand...

Actually long runners yield more low-end torque because there is more air in the runner to hold velocity. The more air you have in the runner, the more inertia you have working for you to move air in the cylinder. Also, the smaller the diameter the runner, the faster the air wants to move. As rpm's increase, your motor wants the same amount of air, but in increasingly less time. In other words, the cylinder needs to speed up the rate of airflow. As the amount of time per cycle (time per intake stroke) decreases, the inertia starts to work against the cylinder, hindering high rpm performance. The opposite is true for shorter runners, but this is an entirely different concept than ram tuning.

1fstbrd,

That's a great video. What a simple test!
 
Back to what I previously said about the m90. I really think its a waste to put this time and effort into the factory lower and. If by chance somehow you miraculously were able to get a more efficient designed intake neatly packaged without a pro mod hood scoop...Any power you may get will be negligible. The M90 is only an m90. The time and effort can be better spent elsewhere. I think that is what is being said here. Bigger IC, larger SC inlet, TB, MAF..More boost, meth...and or a blower upgrade is where you are going to have a good base to make power. You want to stick with an m90 and not blow the bank a late model s ported.

Im not trying to be a dream crusher but whenever I am to have something designed before even putting an ounce of resources into it I sit down with my team and think over its feasibility. Which in a way you can consider this post. And its really saying..Final resolution...Don't do it.
 
XxSlowpokexX said:
Back to what I previously said about the m90. I really think its a waste to put this time and effort into the factory lower and. If by chance somehow you miraculously were able to get a more efficient designed intake neatly packaged without a pro mod hood scoop...Any power you may get will be negligible. The M90 is only an m90. The time and effort can be better spent elsewhere. I think that is what is being said here. Bigger IC, larger SC inlet, TB, MAF..More boost, meth...and or a blower upgrade is where you are going to have a good base to make power. You want to stick with an m90 and not blow the bank a late model s ported.

Im not trying to be a dream crusher but whenever I am to have something designed before even putting an ounce of resources into it I sit down with my team and think over its feasibility. Which in a way you can consider this post. And its really saying..Final resolution...Don't do it.
Click to expand...

There is some wise words here. Unfortunately, heh heh, most of us aren't very wise (including myself). I think that there's always the idea that there's some sort of "super stock" setup that could yield some sort of decent gains. In reality, if one is doing that, they'll likely have to settle for "unique build" rather than power gains. As people have mentioned here, it's the air distribution and the relatively equal distribution that is desirable. A more perfect setup would involve much more space in the engine bay, where the return plenum isn't even crammed in between the supercharger and firewall.

The anemomer idea could be a good one, if one were to fabricate some sort of custom intake manifold......I like the idea where the guy spun the supercharger via a drill and measured the air output of each manifold port. When porting my 3.8 split port Mustang upper and lower, in the lower, I'd noticed that the oil/ gunk from the PCV was heavier in some cylinders, and after almost 200,000 kms, a couple of the runners were pretty much almost clean. The runners by the firewall were the cleanest (where the air would have the shortest route to go), and those ones were also closest to the PCV connection in the upper manifold. The runners closest to the front of the car--furthest from the throttle body opening, were the dirtiest with oil/ gunk/ PCV blowby. Any theories on this?
 
XxSlowpokexX said:
Back to what I previously said about the m90. I really think its a waste to put this time and effort into the factory lower and. If by chance somehow you miraculously were able to get a more efficient designed intake neatly packaged without a pro mod hood scoop...Any power you may get will be negligible. The M90 is only an m90. The time and effort can be better spent elsewhere. I think that is what is being said here. Bigger IC, larger SC inlet, TB, MAF..More boost, meth...and or a blower upgrade is where you are going to have a good base to make power. You want to stick with an m90 and not blow the bank a late model s ported.

Im not trying to be a dream crusher but whenever I am to have something designed before even putting an ounce of resources into it I sit down with my team and think over its feasibility. Which in a way you can consider this post. And its really saying..Final resolution...Don't do it.
Click to expand...

You summed it up very well. I already have most of the things on your list, and have almost finished my own inlet plenum. The thing that appeals most to me is the fun in building the manifold and the fact that nobody else would have another one. That's all. As near as I can figure the theory is sounds and the challenge is in the execution. Effort per unit performance gained it's about the last mod anyone should consider. I'm definitely convinced of that. There is something to be gained, but the reality is that there are so many factors to consider that the finished product will probably not function even as well as the stock manifold does, but that doesn't mean it's not possible. It's just a neat challenge is all.

1fstbrd,
I would guess that it has to do with the mass of the oil. The air coming out of the return plenum much more easily turns or bounces around and turns into the runners closest to the firewall than the far heavier oil does. It keeps going until it hits something, being the runners farthest from firewall. That would be my guess anyway.
 
1FSTBRD said:
There is some wise words here. Unfortunately, heh heh, most of us aren't very wise (including myself). I think that there's always the idea that there's some sort of "super stock" setup that could yield some sort of decent gains. In reality, if one is doing that, they'll likely have to settle for "unique build" rather than power gains. As people have mentioned here, it's the air distribution and the relatively equal distribution that is desirable. A more perfect setup would involve much more space in the engine bay, where the return plenum isn't even crammed in between the supercharger and firewall.

The anemomer idea could be a good one, if one were to fabricate some sort of custom intake manifold......I like the idea where the guy spun the supercharger via a drill and measured the air output of each manifold port. When porting my 3.8 split port Mustang upper and lower, in the lower, I'd noticed that the oil/ gunk from the PCV was heavier in some cylinders, and after almost 200,000 kms, a couple of the runners were pretty much almost clean. The runners by the firewall were the cleanest (where the air would have the shortest route to go), and those ones were also closest to the PCV connection in the upper manifold. The runners closest to the front of the car--furthest from the throttle body opening, were the dirtiest with oil/ gunk/ PCV blowby. Any theories on this?
Click to expand...

My theory would be the oil from the PCV system had enough velocity near the back cylinders that it went straight into the cylinders, but by the time it reached the front cylinders, if had lost momentum and fell out of suspension, and caked onto the intake runners.
 
A bit of a resurrection to this thread, but it's one of the newer ones--and some of the older intake manifold design query threads had some really great info and ideas. After taking a thorough look at mine, one design flaw really sticks out: the bottom/ port floor takes a somewhat sharper angle to enter the head port floor, which is the straightest, least turbulent path into the heads/ cylinders. I'm wondering if the arc of the airflow into the intake ports doesn't send more air than necessary up into the port roof, which already has a turbulent (and longer) path there from having to go past the injector area and then the valve guides. I'd ran a piece of string, with a vacuum connected to the intake bowl, and the flow was straightest along the port floor, very turbulent along the port roof, and fairly turbulent (and seemed to be a low flow area) on the port sides.

Has anyone straightened out the intake manifold port floor area (as much as can be straightened, that is) so that it's less of an angle for the air to enter into the intake ports? Or examined how much of a quality airflow is going out the port floor/ short side radius? Tomorrow, i'll hook a vacuum up to each port and see where the string goes and what path it takes on its exit.
 
Last edited:
You must log in or register to reply here.
Back
Top