The Effect of Intake Manifold Design on Engine Power and Efficiency

When it comes to optimizing engine performance, one often overlooked aspect is the intake manifold design. The intake manifold plays a crucial role in directing air-fuel mixture into the cylinders, which directly affects power output and efficiency. In this article, we will delve into the world of intake manifold design and explore its impact on engine performance.

The Supercharging Effect

One of the most significant benefits of optimizing intake manifold design is the supercharging effect. This occurs when a pressure wave hits the back of the plenum and then returns to the intake manifold, forcing in extra air. The timing of this event can be critical, as it requires precise control over the intake manifold's design to maximize power output.

To achieve this supercharging effect, engine builders often use specialized intake manifolds with narrow runners that allow for increased velocity of airflow. This results in a more turbulent air-fuel mixture, leading to improved combustion and increased power output. However, as RPM increases, the need for more airflow becomes apparent, and the design must adapt accordingly.

Low vs. High RPM Design

For low RPM engines (typically under 2,000-3,000 RPM), longer runners are often preferred. This allows for a greater distance between the plenum and the intake manifold, enabling the pressure wave to bounce back and forth multiple times before reaching the cylinders. This repeated compression creates a supercharging effect that can significantly boost power output.

In contrast, higher RPM engines (typically above 5,000-6,000 RPM) require shorter runners to maintain efficiency. With double the RPM, the pressure wave has less time to bounce back and forth, and therefore, longer runners would result in decreased performance. Instead, shorter runners allow for faster airflow, enabling the engine to produce more power across a broader RPM range.

Narrowing the Intake Manifold

Another approach to optimizing intake manifold design is to narrow it, particularly at lower RPMs. This creates higher air velocities and turbulence, leading to improved combustion and increased power output. However, as RPM increases, wider intakes are often preferred to accommodate the greater airflow demands.

For example, consider a low-RPM engine with a butterfly valve that closes off the lower portion of the intake manifold. At low RPMs, this valve creates a high-velocity air path, allowing for improved combustion and increased power output. However, at higher RPMs, the valve opens, and the air can flow directly into the cylinders, reducing restrictions and improving overall performance.

Variable Intake Manifold Design

One innovative approach to optimizing intake manifold design is to use variable components that adjust the airflow characteristics based on engine speed. This allows for a more precise control over power output and efficiency across different RPM ranges.

For instance, consider an intake manifold with a variable-length runner that adjusts its length at specific RPM points. At low RPMs, the longer runner creates a high-velocity air path, while at higher RPMs, it shortens to improve airflow and reduce restrictions.

In summary, optimizing intake manifold design is crucial for maximizing engine power and efficiency. By understanding the supercharging effect, low vs. high RPM design considerations, narrowing the intake manifold, and variable intake manifold designs, engine builders can create optimized intake manifolds that deliver improved performance across a broader RPM range. Whether it's through careful design or innovative materials, optimizing the intake manifold is an often overlooked yet critical aspect of engine tuning and development.

"WEBVTTKind: captionsLanguage: enhello everyone and welcome in this video we're going to be talking about variable intake manifolds as well as intake manifold tuning and the cool thing about this is even with naturally aspirated engines you can kind of have this supercharging effect uh depending on your intake manifold tuning and the way this works is as follows so you've got your intake here your air is going to come in it'll pass through the throttle body and then start to go down this intake runner right here now your engine of course is on the intake stroke for this cylinder so it's pulling in that air causing this air to move at High Velocity now right before that air gets into that cylinder your valve closes so as a result of that that air still has its velocity in this direction and it piles up and builds up in this lower section of the runner and it builds up in pressure so now that pressure wave is going to go back it's going to go all the way back up to the plenum hit that plenum and then start to come back down now of course the number of times that it does this it'll start to dissipate out and you'll no longer have this effect but you're going to have this pressure wave B bouncing back back and forth so it hits the back of the plenum starts to come back down and if you time your intake right and you have that open up right as that pressure wave is coming in you can force in a little extra air into that cylinder meaning you're going to make more power and so this effect is only going to be useful for a very narrow RPM because anytime that timing is off of course then it's not going to give that supercharging effect it's not going to push in that extra air so the reason why you would want to use a variable intake manifold is you can create another range at which this is going to be useful so you're just going to have this one Peak here we've got this little simplified uh plot to show the supercharging effect and where it's at its most effective point it would actually have some smaller peaks in there uh depending on how many times it's bounced back and forth but just a simplified version it's going to be most effective at 1 RPM now if you shorten the length of these Runners it's going to push that over into the higher RPM range because you're going to have less time for that uh to bounce back and forth that air to bounce back and forth so if you have both of these available you can see you've got these two peaks here and you have you know a better operating condition for your engine where you can maintain power across a broader RPM range okay so what you know what do you want to do with your intake manifold itself well at lower RPM it's better to have a longer Runner because you need more time for that pressure to go uh back to the plum and then come back down as you get into the higher RPM you know let's say or ,000 here 6,000 here you're going to have half the time because you've got double the RPM for that pressure wave to hit the back of the plum and come back down so have the time half the distance and that means you'll be able to get that same benefit so shorter is going to be better at higher RPM now narrow is also better for lower RPM because it means you're going to have air moving at a higher velocity moving at a higher velocity it'll become more turbulent mix with the fuel better better air fuel mixture and you'll have you know a better combustion with wider however at higher RPM you're going to want it to be wider and that's just because of flow you don't want it to restrict how much air can pass through wider means higher mass flow uh capacity and so you you don't restrict it at higher engine RPMs and you can create more power with more flow so how is this done with an intake manifold well I've got two different examples here uh different ways of going about it so here you can see a low RPM we're looking at Blue and you're going to have this little valve right here so here's our intake manifold and then higher RPM is going to be in red so at a low RPM with this particular intake manifold setup you're going to have this butterfly valve right here which is going to close off this lower portion so all the air is forced to go through this long narrow section so we can get a high velocity and you can make decent power at low RPM then once you get to high RPM this valve right here opens up and you can use all of this to bring in air uh so much more air and you know it's going to have a longer a shorter distance uh right here now this one doesn't change distance as much as some of the other methods so this for example right here you can have the air come in at low RPM it'll be closed off and has to travel back all the way around before it can get into the engine or at a high RPM it can just go this really short shot right here and get in so that'll give you that more effective uh High supercharging effect at a higher RPM versus something like this but this one you know you're going to change your flow characteristics so both of them going to give you a benefit of a wider Power Band um depending on you know how the air flow is and what RPM you're at and you know your throttle and things like that uh so both of them giving you a benefit and just two of the examples out there of course there's plenty of ways that you could derive a system like this to change uh both the width or uh the distance at which the air has to travel before it gets into your cylinder so thank you guys for watching if you have any questions or comments feel free to leave those belowhello everyone and welcome in this video we're going to be talking about variable intake manifolds as well as intake manifold tuning and the cool thing about this is even with naturally aspirated engines you can kind of have this supercharging effect uh depending on your intake manifold tuning and the way this works is as follows so you've got your intake here your air is going to come in it'll pass through the throttle body and then start to go down this intake runner right here now your engine of course is on the intake stroke for this cylinder so it's pulling in that air causing this air to move at High Velocity now right before that air gets into that cylinder your valve closes so as a result of that that air still has its velocity in this direction and it piles up and builds up in this lower section of the runner and it builds up in pressure so now that pressure wave is going to go back it's going to go all the way back up to the plenum hit that plenum and then start to come back down now of course the number of times that it does this it'll start to dissipate out and you'll no longer have this effect but you're going to have this pressure wave B bouncing back back and forth so it hits the back of the plenum starts to come back down and if you time your intake right and you have that open up right as that pressure wave is coming in you can force in a little extra air into that cylinder meaning you're going to make more power and so this effect is only going to be useful for a very narrow RPM because anytime that timing is off of course then it's not going to give that supercharging effect it's not going to push in that extra air so the reason why you would want to use a variable intake manifold is you can create another range at which this is going to be useful so you're just going to have this one Peak here we've got this little simplified uh plot to show the supercharging effect and where it's at its most effective point it would actually have some smaller peaks in there uh depending on how many times it's bounced back and forth but just a simplified version it's going to be most effective at 1 RPM now if you shorten the length of these Runners it's going to push that over into the higher RPM range because you're going to have less time for that uh to bounce back and forth that air to bounce back and forth so if you have both of these available you can see you've got these two peaks here and you have you know a better operating condition for your engine where you can maintain power across a broader RPM range okay so what you know what do you want to do with your intake manifold itself well at lower RPM it's better to have a longer Runner because you need more time for that pressure to go uh back to the plum and then come back down as you get into the higher RPM you know let's say or ,000 here 6,000 here you're going to have half the time because you've got double the RPM for that pressure wave to hit the back of the plum and come back down so have the time half the distance and that means you'll be able to get that same benefit so shorter is going to be better at higher RPM now narrow is also better for lower RPM because it means you're going to have air moving at a higher velocity moving at a higher velocity it'll become more turbulent mix with the fuel better better air fuel mixture and you'll have you know a better combustion with wider however at higher RPM you're going to want it to be wider and that's just because of flow you don't want it to restrict how much air can pass through wider means higher mass flow uh capacity and so you you don't restrict it at higher engine RPMs and you can create more power with more flow so how is this done with an intake manifold well I've got two different examples here uh different ways of going about it so here you can see a low RPM we're looking at Blue and you're going to have this little valve right here so here's our intake manifold and then higher RPM is going to be in red so at a low RPM with this particular intake manifold setup you're going to have this butterfly valve right here which is going to close off this lower portion so all the air is forced to go through this long narrow section so we can get a high velocity and you can make decent power at low RPM then once you get to high RPM this valve right here opens up and you can use all of this to bring in air uh so much more air and you know it's going to have a longer a shorter distance uh right here now this one doesn't change distance as much as some of the other methods so this for example right here you can have the air come in at low RPM it'll be closed off and has to travel back all the way around before it can get into the engine or at a high RPM it can just go this really short shot right here and get in so that'll give you that more effective uh High supercharging effect at a higher RPM versus something like this but this one you know you're going to change your flow characteristics so both of them going to give you a benefit of a wider Power Band um depending on you know how the air flow is and what RPM you're at and you know your throttle and things like that uh so both of them giving you a benefit and just two of the examples out there of course there's plenty of ways that you could derive a system like this to change uh both the width or uh the distance at which the air has to travel before it gets into your cylinder so thank you guys for watching if you have any questions or comments feel free to leave those below\n"