Why aren't intakes made like headers?

[Demon-Xanth]

I've been wondering this for a long time. Most intakes are made from either cast aluminum, iron, or composite. Why not make a tubular intake like headers?

 

[theeedude]

Unnecessary cost. Intake doesn't need to deal with all the heat and back pressure issues of exhausts, so why overbuild it?

 

[lsd]

For what effect? long runner intakes generally produce more TQ, short more HP. There's space constraints with V engines.

 

[angry hampster]

It would also require individual throttle bodies to be remotely efficient, wouldn't it?

 

[LTC8K6]

I thought intake manifolds like headers were common these days...

 

[Demon-Xanth]

My thinking was that people rag on exhaust manifolds for not flowing well, even though many are designed quite well. But intake manifolds built like the exhaust manifolds are ragged on. There have been improvements such as the runners, but rather than meeting in a collector they go to a plenum. But in the exhaust, they don't go to a plenum, they go to a collector. Just wondering about the physics reasons why they're different.

 

[jlee]

My Corolla had a tubular intake runners.

 

[RichUK]

Eh?

 

[Kadarin]

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

The current generation M3 has individual throttle bodies...

And yes, the individual throttle bodies allow the intake tubes to all be the same length.

 

[DivideBYZero]

Originally posted by: Kadarin

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

The current generation M3 has individual throttle bodies...

And yes, the individual throttle bodies allow the intake tubes to all be the same length.

The last 3 M3 engines have had individual throttle bodies.

 

[Cobalt]

Originally posted by: DivideBYZero

Originally posted by: Kadarin

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

The current generation M3 has individual throttle bodies...

And yes, the individual throttle bodies allow the intake tubes to all be the same length.

The last 3 M3 engines have had individual throttle bodies.

Lucky bastards, the US E36 didn't.

 

[exdeath]

Intakes are designed to stage and store and provide a steady flow of non turbulent air to the cylinders and to leverage Helmholtz resonance to "supercharge" the intake air by timing air flow momentum during intake valve events to minimize pumping losses and intake stroke drag.

Exhaust headers are designed to maximize pressure-vacuum pulses to generate a scavenging effect and have to deal with high levels of heat.

Two completely different things.

Very long tubes in the exhaust help to keep the suction at the exhaust port for as long as possible before the cylinders are coalesced together into a bigger tube and the effect diminishes. Runners of that length on an intake would provide very poor mid to high RPM performance and poor signal transfer (read: throttle response) from the plenum to the intake port.

Intakes are made of cast metals or molded plastic because they can be engineered into specific shapes and volumes for resonance while meeting the installation dimensions, and it can be done very cheap and fast.

 

[Demon-Xanth]

Originally posted by: exdeath
Intakes are designed to stage and store and provide a steady flow of non turbulent air to the cylinders and to leverage Helmholtz resonance to "supercharge" the intake air.

Exhaust headers are designed to maximize pressure-vacuum pulses to generate a scavenging effect and have to deal with high levels of heat.

Two completely different things.

Very long tubes in the exhaust help to keep the suction at the exhaust port for as long as possible before the cylinders are coalesced together into a bigger tube and the effect diminishes. Runners of that length on an intake would provide very poor mid to high RPM performance and poor signal transfer (read: throttle response) from the plenum to the intake port.

Intakes are made of cast metals or molded plastic because they can be engineered into specific shapes and volumes for resonance while meeting the installation dimensions, and it can be done very cheap and fast.

Thanks

 

[DivideBYZero]

Originally posted by: cobalt

Originally posted by: DivideBYZero

Originally posted by: Kadarin

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

The current generation M3 has individual throttle bodies...

And yes, the individual throttle bodies allow the intake tubes to all be the same length.

The last 3 M3 engines have had individual throttle bodies.

Lucky bastards, the US E36 didn't.

Yeah, I'm not really sure why that version you got even had the badge. The original E36 had a 286hp mill, while the Evo version released a little later had a 320hp unit. You got stiffed with a 240hp version.

 

[Ronstang]

Do you mean like THIS? I have had one of these for almost 15 years.

 

[Demon-Xanth]

Originally posted by: Ronstang
Do you mean like THIS? I have had one of these for almost 15 years.

Nope, that still goes to a plenum at the top. If it was like how I was asking about, the runners would point the other way and lead into a tapered collector that the throttlebody would be mounted to. GT-40 intake, right?

 

[Ronstang]

Originally posted by: Demon-Xanth

Originally posted by: Ronstang
Do you mean like THIS? I have had one of these for almost 15 years.

Nope, that still goes to a plenum at the top. If it was like how I was asking about, the runners would point the other way and lead into a tapered collector that the throttlebody would be mounted to. GT-40 intake, right?

Your idea of an intake does not exist because it would not work properly except at extremely high RPM and high intake velocity, if even then. The dynamics of airflow are different depending which way it is flowing. Headers work because of the scavenging affect and the difference in heat between the cylinder and the exhaust to help pull the exhaust out of the cylinder. Your idea of an intake would probably not even idle.

 

[sdifox]

Originally posted by: DivideBYZero

Originally posted by: cobalt

Originally posted by: DivideBYZero

Originally posted by: Kadarin

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

The current generation M3 has individual throttle bodies...

And yes, the individual throttle bodies allow the intake tubes to all be the same length.

The last 3 M3 engines have had individual throttle bodies.

Lucky bastards, the US E36 didn't.

Yeah, I'm not really sure why that version you got even had the badge. The original E36 had a 286hp mill, while the Evo version released a little later had a 320hp unit. You got stiffed with a 240hp version.

My guess is the dirty gas in NA. Same thing happens to the Diesels.

 

[alkemyst]

Originally posted by: Demon-Xanth
I've been wondering this for a long time. Most intakes are made from either cast aluminum, iron, or composite. Why not make a tubular intake like headers?

huh? There are tubular intakes as well.

 

[alkemyst]

Originally posted by: angry hampster
It would also require individual throttle bodies to be remotely efficient, wouldn't it?

can still do a plenium and single throttle body and be effective.

 

[exdeath]

Originally posted by: Demon-Xanth

Originally posted by: Ronstang
Do you mean like THIS? I have had one of these for almost 15 years.

Nope, that still goes to a plenum at the top. If it was like how I was asking about, the runners would point the other way and lead into a tapered collector that the throttlebody would be mounted to. GT-40 intake, right?

That wouldn't work, as the shaping of the merging of the pipes to the collector is designed to streamline flow from many-to-one without turbulence, and would work against the one-to-many flow in reverse.

The proper intake design for a one-to-many flow is a storage plenum of the smallest volume capable of feeding the runners at the desired max RPM without cavitation, with flared runners protruding into the plenum. If you look at any high performance NA intake, like the Cobra R intake or any custom sheet metal intake, you will see a two piece design where the runners are separate from the plenum material and are flared like horns; something that isn't done with common single piece cheap molded or cast intakes.

A plenum will always be required on any engine that uses a single one of *any* of: MAF meter, MAP sensor, air filter, throttle body, idle air valve, turbo/supercharger. Even engines like the S54 in the E46 M3 that uses ITBs must use plastic plenum that encloses the ITBs to provide a single point of entry for the MAF meter and air filter.

When you see pictures of cars without plenums and using open ITBs or individual horns, these are most usually either running single barrel carburetors or constant flow RPM based injection, with no air filters; eg: purpose built race cars or show cars that would not last long in any high mileage street driving.