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Old 11th March 2012, 14:38   #1
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Default Basics of Intake Length vs Torque-HP

Just sharing basics of what i have learnt about "Intake Length vs Torque & HP"

1) Here i would be talking about intake length as in the length of runners from throttel body to head.

2) But the same principal is applicable for length of intake pipe from throttel body to air filter body and intake duct.

3) You can also relate it to how the calculated headers give you gains in specific RPM range as per design.

So we all know long intake pipe means better low end torque-hp & short intake pipe means better torque-hp at high RPM's.

(Imagine the below in slow motion & refer to the pic for every point)

1) During the suction stroke of an cylinder the first place to generate vacuum is the runner because the air filled in the runner gets sucked inside the cylinder.

2) This releases a negative wave starting from inlet valve through the runners till the throttel body where air is available.

3) Then in the throttel body this negative air pressure wave is converted to a positive wave (because of the available air) & it travels back to the point where it originated from filling the vacuum in runners with air & cylinder too.This wave continues till the end of suction stroke.

Please excuse the Paint Job
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During suction stroke the first negative & positive pressure wave cycle should happen quickly, say when piston moves downward only 25%.This helps rest of the 75% downward movement to happen with ease because along with the piston sucking air inside cylinder the positive pressure wave also results in filling of the cylinder resulting increased volumetric efficiency which leads to better Toque & HP.

Now for this first negative & positive wave cycle to happen quickly your RPM ranges should be in synchro with the intake lengths.Hence the question by tuners which rpm range you want more power.

Same applies for exhausts too.When using calculated headers made to work for specific rpm band instead of only the piston pushing out the gases during exhaust stroke,the length helps in the gases pulling out each other resulting in better scavenging & filling of more fresh air during suction stroke.

My knowledge being limited about this i wont be able to answer all questions nor defend if someone crosses what i have posted

More inputs,advices,info sharing links welcomed
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Old 11th March 2012, 19:27   #2
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Default Re: Basics of Intake Length vs Torque-HP

Are you pointing to the principles of Helmholtz resonance? Is the explanation on this link (Define the effects of Helmholtz resonance within the intake manifold? - Yahoo! Answers) similar to what you are sharing? Would be interested to know more about this, especially related to regular everyday cars (as opposed to race cars), if someone can pitch in with more information.
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Old 11th March 2012, 19:47   #3
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Default Re: Basics of Intake Length vs Torque-HP

Is this the reason why my ikon has a resonator box , i always wondered what is the real reason behind that box? I will be glued to this thread now
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Old 11th March 2012, 21:16   #4
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Default Re: Basics of Intake Length vs Torque-HP

Hi,
Bread and butter for the tuners. Maybe moving it to the Modifications section would elicit more responses.

Quote:
Originally Posted by SS-Traveller View Post
Are you pointing to the principles of Helmholtz resonance? Is the explanation on this link (Define the effects of Helmholtz resonance within the intake manifold? - Yahoo! Answers) similar to what you are sharing? .
In a nutshell, correct. (except for reflection starting from throttle plate. Any discontinuity will generate a reflection. The reflection from the open end is likely to be stronger.) And better to start with the exhaust than inlet.

Thank God we are not getting into two strokes.

Plenty of books on the subject.

Regards
Sutripta
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Old 11th March 2012, 22:02   #5
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Default Re: Basics of Intake Length vs Torque-HP

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Originally Posted by Sutripta View Post
Thank God we are not getting into two strokes.
I was just about to get into two stroke expansion chamber business and how 2 strokes gain so much power through the back door using chambers. That said, i think i'd stick with the 4 strokes discussion
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Old 11th March 2012, 22:18   #6
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by SS-Traveller View Post
Are you pointing to the principles of Helmholtz resonance? Is the explanation on this link (Define the effects of Helmholtz resonance within the intake manifold? - Yahoo! Answers) similar to what you are sharing? Would be interested to know more about this, especially related to regular everyday cars (as opposed to race cars), if someone can pitch in with more information.
Yes its called resonating pipe effect. But nowhere in between you see a resonator box.With the helmholtz resonator box there are some more advantages.Will post it ones i find the link.

Imagine a bucket full of water,you insert a pipe in it and suck water through it.Ones the water starts to flow it keeps on flowing untill you stop it or the water in bucket finishes.

So when you start to suck water you create vaccume in the pipe which gererates a negative wave.This negative waves goes into the bucket turns positive & returns back to the point of origin & you have water flowing out of the pipe with no efforts required.

Quote:
Originally Posted by Catalyst_delhi View Post
Is this the reason why my ikon has a resonator box , i always wondered what is the real reason behind that box? I will be glued to this thread now
Which reason you are thinking of for your ikon to sport that box ? Even bikes have those resonance boxes.Even without that box (resonator box) your system will function like what explained in first post.Its just that with the resonator box you get more advantages.Let me find the link and i will post it.

Last edited by Neil.Bhujbal : 11th March 2012 at 22:24.
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Old 12th March 2012, 01:55   #7
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by Neil.Bhujbal View Post

Imagine a bucket full of water,you insert a pipe in it and suck water through it.Ones the water starts to flow it keeps on flowing untill you stop it or the water in bucket finishes.
My favorite topic but do not agree with you here , the water flows because of pressure differential , atmospheric pressure acts on the surface of the water , it acts at the end of the open pipe too but has to counter the weight of the water column in the pipe. That is why larger the vertical difference between the mouth of the pipe and the water surface, faster the flow of water.

Last edited by Born2Slow : 12th March 2012 at 01:58.
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Old 12th March 2012, 09:27   #8
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by Born2Slow View Post
My favorite topic but do not agree with you here , the water flows because of pressure differential , atmospheric pressure acts on the surface of the water , it acts at the end of the open pipe too but has to counter the weight of the water column in the pipe. That is why larger the vertical difference between the mouth of the pipe and the water surface, faster the flow of water.
My bad.

Here's something that tells the advantages of Helmholtz Resonator boxes -

The colored parts in the pic are resonator boxes -

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1) They work as an air reservoir, so when you wack the throttle wide open at low speeds, the engine has something to work with until you get going fast enough (which isn't very fast) to fill the air intake runners and the engine won't run out of breath.

2) Intake pulses can cause a harmonic wave that can amplify and inturupt clean airflow.
The resonator causes a counter-wave to stop harmonic amplification and ensure that the air box delivers smooth airflow into the throttle bodies.

Pressure from a ram-air system will also wash harmonic pulsation. The stock air-box does not have sufficient air-pressure from ram-air to settle harmonics.

The air intake needs either Ram-air intakes or the resonator.
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Old 12th March 2012, 11:34   #9
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by Catalyst_delhi View Post
Is this the reason why my ikon has a resonator box , i always wondered what is the real reason behind that box? I will be glued to this thread now
Quote:
Originally Posted by Neil.Bhujbal View Post
The air intake needs either Ram-air intakes or the resonator.
Hi,

My Ikon does not have a resonator box, but older IKON's have. The rest of the intake, including the manifold is exactly the same. There is not much power/response difference in lower or higher rpms. So, in an IKON, I guess its something to do with the sound. (My IKON, I guess ones from '06 are noticeably louder, and sportier). Not sure. Will dig into it.

-------------------------------


Also, Neil, can you relate this to VGIS in Optra?
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Old 12th March 2012, 23:07   #10
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by dhanushs View Post
Hi,

My Ikon does not have a resonator box, but older IKON's have. The rest of the intake, including the manifold is exactly the same. There is not much power/response difference in lower or higher rpms. So, in an IKON, I guess its something to do with the sound. (My IKON, I guess ones from '06 are noticeably louder, and sportier). Not sure. Will dig into it.
-------------------------------
Also, Neil, can you relate this to VGIS in Optra?
Resonator boxes also kill sound. Have read it somewhere but need to check.

VGIS - Variable Geometry Intake System (Chevy)
Variable Geometry Intake Manifold (Merc)

Variable Geometry Intake Systems/Manifolds wide spreads the Torque & HP band in a vehicle.

What i am talking about in the first post is exactly what happens in the VARIABLE INTAKE MANIFOLDS.

These manifolds have 2 or 3 paths inside them. The path (short,medium,long) followed by the air depends upon position of flaps or rotary valves inside which are actuated by vacuume on revival of signal from ECU.

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From 800 to 1000 RPM the air flows through shorter path.
From 1000 to 3600 RPM the air flows through longer path.
From 3600 to Redline the air flows through shorter path.

So all these long-short lengths at different RPM ranges comes down to same thing and that is - use of resonance to fill up cylinders (increase volumetric efficiency) which finally leads to better Toque & HP in a wide RPM band.

Last edited by Neil.Bhujbal : 12th March 2012 at 23:12.
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Old 12th March 2012, 23:16   #11
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by dhanushs View Post
Hi,

My Ikon does not have a resonator box, but older IKON's have. The rest of the intake, including the manifold is exactly the same. There is not much power/response difference in lower or higher rpms. So, in an IKON, I guess its something to do with the sound. (My IKON, I guess ones from '06 are noticeably louder, and sportier). Not sure. Will dig into it.

-------------------------------


Also, Neil, can you relate this to VGIS in Optra?
I was not aware of this , I wondered if i removed this resonator box , will there be damage to the MAF , I heard that the MAF could get damaged by the vibrations/resonance if the resonator is removed. I know this sounds far fetched but I am noobs when it comes to intake.
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Old 13th March 2012, 10:15   #12
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Default Re: Basics of Intake Length vs Torque-HP

how does this work with turbocharger/supercharger ?

Also, what kind of intake length do you need to get the effect at, let's say, 2400rpm and 6000rpm (40Hz and 100Hz respectively)? Can someone show the calculation?

Last edited by vina : 13th March 2012 at 10:17.
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Old 13th March 2012, 16:12   #13
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by Neil.Bhujbal View Post
The resonator causes a counter-wave to stop harmonic amplification and ensure that the air box delivers smooth airflow into the throttle bodies.

Pressure from a ram-air system will also wash harmonic pulsation. The stock air-box does not have sufficient air-pressure from ram-air to settle harmonics.

The air intake needs either Ram-air intakes or the resonator.
Both resonator and ram-air systems are new to me. Correct me if I am wrong here. So, from what I understood, is resonator made of nothing but varying length intake systems that produces a positive wave to a negative vacuum wave thereby reducing noise? Also can you elaborate on what is an air-box?

And beautiful explanation on the concept of VGIS. Once again correct me here, does VGIS perform the same function as resonator?

Why isn't VGIS as widely used as a turbocharger or any other power-enhancing unit? Is it due to any packaging problems or something?
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Old 13th March 2012, 21:33   #14
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Default Re: Basics of Intake Length vs Torque-HP

Quote:
Originally Posted by vina View Post
how does this work with turbocharger/supercharger ?

Also, what kind of intake length do you need to get the effect at, let's say, 2400rpm and 6000rpm (40Hz and 100Hz respectively)? Can someone show the calculation?
Variable Intake Manifolds are used only on Naturally aspirated engines.During the suction stroke you have air getting sucked IN & hence the resonance effect.

Turbocharging/supercharging are force induction methods.Here resonance and stuff doesn't matter because you force feed the engine with air.

No idea about your second question,its too theoretical for me.If i wanted my power to be between 4000 to 6000 rpm then i would dyno my car see the Torque & HP curves & increase-decrease the intake length accordingly. (trial and error method)But just intake wont give you that much of a difference you would need to do up your exhaust too.

Quote:
Originally Posted by vvijay View Post
Both resonator and ram-air systems are new to me. Correct me if I am wrong here. So, from what I understood, is resonator made of nothing but varying length intake systems that produces a positive wave to a negative vacuum wave thereby reducing noise? Also can you elaborate on what is an air-box?

And beautiful explanation on the concept of VGIS. Once again correct me here, does VGIS perform the same function as resonator?

Why isn't VGIS as widely used as a turbocharger or any other power-enhancing unit? Is it due to any packaging problems or something?
You have got it right but not completely.

1)Resonator boxes of different length,shape,size are put on intake systems of cars and bikes so that during suction stroke when air is being sucked inside the cylinder,it should not get disturbed by the pulse which is generated because of sucking. So this resonator box takes care of these pulses.

2) When you give sudden throttel the engine should not choke off air so in this situation the air from these resonator boxes is used for that moment untill the air flow is adjusted.

3) About resonator boxes silencing the intake sound,like i said earlier i am not sure i need to check.But i feel like i had read it somewhere.

NO VGIS does not perform like a resonator box.

Variable intake manifolds are costly and the difference they make are not as much as turbos & superchargers.They are mostly used in high end naturally aspirated cars merc,bmw,audi's.

Last edited by Neil.Bhujbal : 13th March 2012 at 21:37.
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Old 17th March 2012, 01:22   #15
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Default Re: Basics of Intake Length vs Torque-HP

Hey Neil! Looks like you are playing with the Variable geometry intake. Thanks for bringing up this thread. Will stay tuned. See if you can find out a way to play with these lengths.
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