Swift 1.2 VVT Airbox Questions

[Sankar]

The new Swift 1.2 has a new airbox design with a small 45 degree rubber bend attached at the end of the airbox pipe. This rubber end section can be pulled out and re-fitted easily in less than a minute. I think the rubber section was put there by the manufacturer to make the opening of the pipe towards the front end of the engine from where it will get outside air through a slit on the top LHS of the grill.

But there is something else to this rubber piece. The inner diameter (ID) of the plastic pipe from the aribox is approximately 60mm. But the rubber end constricts that opening to around 40mm ID before opening with a bell mouth of around 57mm OD. Why is the ID restricted to 40mm by the rubber pipe from the original close to 60mm?

I have attached a pic of the engine bay with the rubber part marked inside red square.

[VeyronSuperSprt]

Originally Posted by Sankar

The inner diameter (ID) of the plastic pipe from the aribox is approximately 60mm. But the rubber end constricts that opening to around 40mm ID before opening with a bell mouth of around 57mm OD. Why is the ID restricted to 40mm by the rubber pipe from the original close to 60mm?

This is done to increase volumetric efficiency by using the principle of resonance. In essence, the body has to be larger than the neck to take advantage of this principle which helps increase volumetric efficiency.

[SunnyBoi]

Joule–Thomson effect?

Joule

[VeyronSuperSprt]

Originally Posted by SunnyBoi

Joule–Thomson effect?

No, the Joule - Thomson effect is not used to improve volumetric efficiency.

[SunnyBoi]

Originally Posted by VeyronSuperSprt

No, the Joule - Thomson effect is not used to improve volumetric efficiency.

I was replying for the rubber restrictor - perhaps it is used to reduce Intake Temperatures.

[VeyronSuperSprt]

Originally Posted by SunnyBoi

I was replying for the rubber restrictor - perhaps it is used to reduce Intake Temperatures.

The rubber restrictor is the neck I referred in my earlier post which has to be narrower than the body (the longer tube/pipe) that it is connected to for the resonance to work.

[Sankar]

Originally Posted by VeyronSuperSprt

The rubber restrictor is the neck I referred in my earlier post which has to be narrower than the body (the longer tube/pipe) that it is connected to for the resonance to work.

Never would have imagined! But are you sure its for increasing the VE? Can you tell me why and how it works? A link to the info would suffice if you can point me to one.

I removed the rubber and here are some better shots









I was thinking of replacing that restricted looking rubber inlet with a 45degree bend silicone inlet of the same size/slightly larger (70-60) funnel shaped reducer. How would it affect the performance?

[VeyronSuperSprt]

Originally Posted by Sankar

Can you tell me why and how it works? A link to the info would suffice if you can point me to one.

Check out the Helmholtz wave - there are many sites on this.

Here's one:

Volumetric Efficiency and Helmholtz Resonators in an Air Intake in an IC Engine

Originally Posted by Sankar

I was thinking of replacing that restricted looking rubber inlet with a 45degree bend silicone inlet of the same size/slightly larger (70-60) funnel shaped reducer. How would it affect the performance?

Your local mechanic might advise you to go ahead but it would be a bad move. These tubes involve complex calculations which is not limited to the Helmholtz wave but other parameters too.

[Catalyst_delhi]

Did you compare your car to another same model. Look to me like there might be a part missing like a air ram or intake

[Sankar]

Originally Posted by Catalyst_delhi

Did you compare your car to another same model. Look to me like there might be a part missing like a air ram or intake

Yes, i checked out the demo car when it was brought to me and also the vehicle parked inside the showroom when i went there. Both of them had intakes like this and there isn't any missing duct or ram air thingy in my car.

[1self]

The greater the surface area of the suction pipe opening, lesser the pumping losses & therefore more volumetric efficiency. I have gone to extremes on both my cars based on this physical law. Not put up pics yet.

[Sankar]

Originally Posted by 1self

The greater the surface area of the suction pipe opening, lesser the pumping losses & therefore more volumetric efficiency. I have gone to extremes on both my cars based on this physical law. Not put up pics yet.

So will a 70mm 60mm reducer which behaves like a funnel be better than the stock rubber pipe? It will have greater surface area compared to the present setup.

I have tried a funnel like reducer with a BMC CDA intake in my AStar with good results. Had tried various inlet options and finally settled on the funnel setup. So i'm thinking whether a similar setup would be effective with stock box.

[Sankar]

I have been driving with and without the rubber thingy since saturday and here is an observation.

The MID is showing better fuel economy while driving with the rubber thingy removed. With the rubber thingy the AVG displayed used to be between 10 to 12.1 inside city and with AC on always. With the rubber thingy removed the AVG displayed is 13 to 14 in the same driving cycle. During a drive on the Enchakal byepass upto Kazhakoottam (for those who's familiar with this road) on a saturday evening the AVG displayed went as high as 17! This road eventhough called a byepass is pretty crowded for a byepass.

Those with the Swift petrol can remove that rubber thingy and see for yourself if the fuel average displayed is changing or not.

Next thing i want to confirm is whether the IAT is increasing without the rubber thingy, since this new Swift is said to be OBD2 compliant i hope that the dongle works.

[Sridhar K]

Originally Posted by Sankar

I have been driving with and without the rubber thingy since saturday and here is an observation.

The MID is showing better fuel economy while driving with the rubber thingy removed.

How about emission and air filter cleaning interval/replacement? Just curios because per the new Swift manual, air filter cleaning/replacement frequency in 5k km for 1.2 VVT whilst it is 20k for 1.3 DDIS.

[Sankar]

Originally Posted by Sridhar K

How about emission and air filter cleaning interval/replacement? Just curios because per the new Swift manual, air filter cleaning/replacement frequency in 5k km for 1.2 VVT whilst it is 20k for 1.3 DDIS.

Will not affect the emissions since here is no change to the system.
Need to check the manual, i think replacement is at 10000 kilometres.