Secondary Intake Pt 1

I had the old type snorkel for more than a year now. It came out as standard fitting for Neo in 2006. It was replaced by a flexible corrugated type in the CPS model that came out circa 2010. That of the 1st Gen Neo is jokingly known around the Proton user fraternity as the Elephant’s Snorkel due to its larger size. It is still in use by Proton Motorsport in their race machines for the Malaysian Super Series. MSS has 5 rounds. Proton Motorsports currently is the champion in the Sports Touring class with one round to go in November.

This snorkel has a 50mm hole just before the main tract curves to the side of the air box. Originally this hole is connected to a short right angled tube. I assume it is either for a water trap or for attenuating sound. Whatever it was, it has been gone for a while. It has been a source of leak for hot engine air to enter the engine. I had initially put duct tape to plug it. After a few hours, the duct tape would puncture. This would indicate that a vacuum situation had developed during driving. This therefore indicates that the current snorkel is insufficient to take on all demands of the airflow requirement. A quick calculation, assuming that the engine has 90% Volume Efficiency with Max RPM at 7500rpm, it would require a flow of 190 CFM. Which translates to 5,380 litre/min. Now assuming air is still and we estimate that the air moves at 210km/h. This translates to having the air intake size at 44mm diameter. That should be the minimum size of the intake to the throttle body. The throttle body itself has a size of 70mm. If there is restriction, therefore it would create a vacuum. Vacuum is created in any pressure loss throughout the length of the intake tract.

Hose enters the snorkel from beneath and sealed with Electrical Tape.

The snorkel main cross sectional size is 115mm x 58mm with a wall thickness as 4mm on average.  Therefore the cross sectional area is approximately 107mm x 50mm which makes it 5350mm2.  A 70mm diameter should have an area of 3848mm2.  This would have us accept that the current snorkel has 39% more area than required.  Which would be true if we did not take into account losses and what is known as the hydraulic radius of a conduit.  Ideally the intake snorkel must have a hydraulic radius of 70mm after taking into account all the hydraulic losses due to bends and restrictions. Even though the Airbox is of significant volume, air flow remains the same. Its effect is only as a vessel to minimize effect of sudden flow demand such as during increased engine load and acceleration.

On Monday, 8 September 2012, before returning to home, I had decided that if I delayed doing something about the leak, its going to cost me valuable fuel money.  I stopped by a hardware shop, 5 min from my house and bought a flexible hose meant for the drainage of a typical washing machine. I installed it and planned to make observations to the fuel consumption using the onboard fuel computer.

My first recording of the series of test started after sending all my kids to school and proceeded to exit Putrajaya on an almost empty three lane road.  I maintained the speed of 80km/h for a few seconds before resetting the Average Consumption calculation.  It normally will start showing the record after a distance of 500m.  Immediately I saw the reading as 4.0 l/100km and it rises slightly to 4.3 at the end of approximately 20km of driving distance.  Beyond this distance, traffic made it difficult to maintain a constant speed.

Other than immediate consumption, I also wanted to find out whether it is going to improve my daily average of 6.3l/100km, which it did.  But this is also difficult to measure as traffic situation changes on a daily basis.  The most consumption is definitely when the car is not moving in a que for the Subang toll plaza.  But I just needed to know.

The second recording was on the return trip back home with an estimated distance of 40km.  This readout gave an average of 4.3l/100km.  So at least for the duration of the day, the consumption reading was good.

Enters the subframe

Intermediate length

Intermediate length

In preparation for tomorrow’s test, I have moved the location to close behind the front light cluster.  We’ll see how it goes.

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One thought on “Secondary Intake Pt 1

  1. Pingback: Real World Test | Neo R3 DIY

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