[1self]

Actually Sankar, think big, say a megaphone kind of setup. I've done it. The suction surface area is 7 times larger than the throttle body area!

[Sankar]

Space is limited so may not be able to make it much wider at the opening. 76mm or 70mm is what i think will fit in there.

[1self]

You can always make it facing down, towards the ground. That way it will pick up colder air as well.

[groom]

This is one of the practical applications of Bernouli's Principle.
This is not resonance,

This is very simple way to achieve a throttling effect,
By inverse constriction, you are increasing the area of the tube while the air is traveling inside. When the area increases the pressure has to drop, pressure = force / area, but the total energy of the air before the constriction and after the constriction has to remain same due to law of conservation.

Hence, the drop in the static energy will get balanced by increase in the kinetic energy. So as soon as the air mass goes through this constriction, the velocity of the air increases.

Now the trade off between the velocity and pressure will decide the improvement in the overall efficiency.

Any method which uses improvement in MASS of air entering will have highest improvement in efficiency.


One advice, do not change the size or the length of this unless you have enough data to do it.

Refer this link from NASA for more details.
Bernoulli's Equation

[Sankar]

Originally Posted by groom

This is one of the practical applications of Bernouli's Principle.
This is not resonance,

Thanks for the simple and easy to understand explanation and for that link! I'm not permanently changing this setup, i'm only experimenting with the rubber thingy removed and with it and watching if there's any difference in fuel efficiency or performance. So far there is no noticeable increase in performance, but MID shows better FE average with it removed, i wonder why.

[groom]

FE measurements are very complex exercise if accuracy has to be maintained and if comparisons have to be made.

two usual traps which people fall during the FE measurement - driving style and temp. of the ambient air.

In petrol engine both make a significant difference to FE. If you have measured the FE during much cooler days after removal of that rubber bush, it is highly likely that mass of air entering is now higher. Simply because the density is higher. May have negated the effect of that device itself.

next, now the intake length is changed. So this has a significant effect on the resonance of the intake. If you get the better fuel efficiency with same intake length without the constriction, then one to one comparison can be made.

Another important factor is Psyche. There is a term i would like to coin " FE Anxiety", the moment people are conscious of FE , some how there is an improvement, due to conscious effort made in driving. Remember FE marathon which companies conduct, and some drivers can get zillion MPG.

Last important thing i would like to ask - How much improvement in FE did you get ? In percentage terms. greater than 5% ?

[Sankar]

Originally Posted by groom

If you have measured the FE during much cooler days after removal of that rubber bush, it is highly likely that mass of air entering is now higher. Simply because the density is higher. May have negated the effect of that device itself.

No the change was noticed the same day. Drove with the rubber tip on my way to office and then drove without the rubber tip 15 minutes after when i had to go to some place.

Again the change was noticed when i went to the workshop to get horn fitted with the rubber tip on and when i came back after an hour with the rubber tip off.

Originally Posted by groom

next, now the intake length is changed. So this has a significant effect on the resonance of the intake. If you get the better fuel efficiency with same intake length without the constriction, then one to one comparison can be made.

Not comparing intake lengths here. But can you tell me why is it showing better FE without the piece? So is the shorter length with it altered resonance better for my driving cycle?

Another important factor is Psyche. There is a term i would like to coin " FE Anxiety", the moment people are conscious of FE , some how there is an improvement, due to conscious effort made in driving. Remember FE marathon which companies conduct, and some drivers can get zillion MPG.

Not me. I only noticed it because the display was showing better figures all of a sudden. I took the rubber off to see if there is some increase in performance, but what i got was better FE readings.

Last important thing i would like to ask - How much improvement in FE did you get ? In percentage terms. greater than 5% ?

With rubber - 11.5 to 12.1
Without - 13.1 to 14
Inside city with AC on.

Today i drove with rubber tip on and the FE average shown is lower than yesterdays without the tip, and it was a nice cold rainy morning with denser air.

[VeyronSuperSprt]

Originally Posted by groom

This is one of the practical applications of Bernouli's Principle.

Bernoulli's principle is used in fluid dynamics such as the constrictions found in venturis of carburetors. It is not applied in air intake systems. In some models of Maruti the air box itself is called a resonator box. Maruti Suzuki in their environment reports have committed that they will be using resonators in their air intake systems to improve fuel efficiency. Apart from fuel efficiency improved NVH by attenuation is also achieved through the use of resonators.

Originally Posted by Sankar

Today i drove with rubber tip on and the FE average shown is lower than yesterdays without the tip, and it was a nice cold rainy morning with denser air.

The reason your fuel efficiency has increased is not on account of denser/cooler air or using a light foot. It has increased because the volume of air entering the combustion chamber has increased when you removed the constrictor thereby marginally reducing the quantum of fuel entering the combustion chamber (fuel being consumed). If you carefully observe, you will find that the engine also feels slightly lower powered at lower rpms.

[Sankar]

Originally Posted by VeyronSuperSprt

The reason your fuel efficiency has increased is not on account of denser/cooler air or using a light foot. It has increased because the volume of air entering the combustion chamber has increased when you removed the constrictor thereby marginally reducing the quantum of fuel entering the combustion chamber (fuel being consumed). If you carefully observe, you will find that the engine also feels slightly lower powered at lower rpms.

Did a highway round trip of 460kms yesterday and i tested the car with and without rubber thing. At speeds above 80 there was no real difference in the AVG FE shown with and without the rubber constrictor. But there was a lack of power felt when driving around at 80+ without the rubber, the car didn't respond to throttle inputs well.

But while inside the city and at speeds less than 60 to 70 the car without rubber thing shows much better FE AVG and no significant power loss is felt at low speeds.

[Mpower]

Does the K12 VVT have an actual MAF sensor or does it use just TPS+MAP input?

[VeyronSuperSprt]

Originally Posted by Sankar

But there was a lack of power felt when driving around at 80+ without the rubber, the car didn't respond to throttle inputs well.

As I thought. So please DO NOT drive with that constrictor removed as you will damage the engine. The engine will be straining itself and this will create other serious issues with the engine.

[groom]

Originally Posted by VeyronSuperSprt

Bernoulli's principle is used in fluid dynamics such as the constrictions found in venturis of carburetors.

Exactly Veyron, "Fluid Dynamics", Gas and Liquids both are fluids. What applies to Liquids applies to Gases as well, except for properties like compressibility. That's precisely the reason Pneumatics and Hydraulics are very very similar.

Originally Posted by VeyronSuperSprt

The reason your fuel efficiency has increased is not on account of denser/cooler air or using a light foot. It has increased beca
use the volume of air entering the combustion chamber has increased when you removed the constrictor thereby marginally reducing the quantum of fuel entering the combustion chamber (fuel being consumed). If you carefully observe, you will find that the engine also feels slightly lower powered at lower rpms.

Veyron, How will the volume increase? Swift is a 1.3L engine, and 1.3 L will remain same all the while. 1.3L is the volume and it will and will never change. Only thing that changes in MASS, we try always to pack more charge in the 1.3L, by turbo etc etc. how do we do it ? By increasing the pressure, or in other words increasing density.

[VeyronSuperSprt]

Originally Posted by Mpower

Does the K12 VVT have an actual MAF sensor or does it use just TPS+MAP input?

TPS+MAP.

Originally Posted by groom

Exactly Veyron, "Fluid Dynamics", Gas and Liquids both are fluids. What applies to Liquids applies to Gases as well, except for properties like compressibility. That's precisely the reason Pneumatics and Hydraulics are very very similar.

Sure groom. At a theoretical level. As you would know, this principle has very little application, if any, in pneumatics.

Originally Posted by groom

, Veyron,How will the volume increase? Swift is a 1.3L engine, and 1.3 L will remain same all the while. 1.3L is the volume and it will and will never change. Only thing that changes in MASS, we try always to pack more charge in the 1.3L, by turbo etc etc. how do we do it ? By increasing the pressure, or in other words increasing density.

groom, the proportion of air (volume of air) to fuel changes but the total volume remains the same.

[groom]

For even more clarity, i am posting this link.

Bernoulli's principle - Wikipedia, the free encyclopedia,


Sankar, seems like the torque curve is see-sawed around the peak torque point. Means, your higher end has dipped and equivalently the lower end has gone higher.

Which explains the reason, why you get more mileage at lower part throttles and get lower mileage at full or near full throttle.

Another point - Resonance always exists in the inlet and exhaust, with the Box its only possible to amplify either the inlet charge to fill more charge - eg: RX100 bike with resonaters in inlet side.

OR

On the other hand, the exhaust resonate will only amplify the exhaust gas exit, there by the entire cylinder is cleaned up before the fresh charge can be packed. Eg: Exhaust resonator in Bajaj Pulsar.

[groom]

Originally Posted by VeyronSuperSprt

TPS+MAP.



Sure groom. At a theoretical level. As you would know, this principle has very little application, if any, in pneumatics.

This principle has very high application, you see the exhaust of the Discovery Shuttle ? They are cone shaped, venturi like.

Have you see a Carburetor?, its also on this principle,

Seen the wind mill wings, also same. Very high application in automotive and aerodynamics.

Originally Posted by VeyronSuperSprt

groom, the proportion of air (volume of air) to fuel changes but the total volume remains the same.

Possible that mixture has gone leaner, explaining both higher mileage and loss of power. This is very bad for a petrol engine.