[silversteed]

Originally Posted by a4anurag

Just checked their website.

It says suspension is Full Air,

But the brakes - Disc with EBS 5 with a retarder - Hydraulic one.

The other chance could be that the suspension is trying to maintain its compose under braking by releasing air to compensate for the dip.

The EBS-5 is Volvo's nomenclature for its fifth generation Electronic Brake Distribution/Control system. A retarder has nothing to do with the service brakes, as it acts on the prop shaft unlike the brakes which act on the wheel directly. The retarder is hydraulic, but not necessarily the braking system.

The air suspension is adjusted using electronics, it must be trying to maintain the optimum pressure inside the air bellows according to the road conditions and the load. So, that could also be a reason for the hissing sound that you hear.

[a4anurag]

Raking up this old thread though an year old,

This doubt came into my mind as yesterday parts of Hyderabad was witnessing rainfall so while following a Volvo 9400 Multi-Axle the water was trickling down from the top via the sides.



In the picture above (just used as reference, thanks to Binai Sankar Sir) the four slats present on either sides (above the registration number on the sides) that are located just after the last windows contain the air filter if I am not wrong. So Eden it rains how is water movement controlled so as to not interfere or enter into the air filter?

The problem is more woke on move as water is forced inwards due to aerodynamics. Can someone clear my doubt here. Sorry for a noob doubt.

Anurag.

[tharian]

Originally Posted by a4anurag

Raking up this old thread though an year old,

This doubt came into my mind as yesterday parts of Hyderabad was witnessing rainfall so while following a Volvo 9400 Multi-Axle the water was trickling down from the top via the sides.



In the picture above (just used as reference, thanks to Binai Sankar Sir) the four slats present on either sides (above the registration number on the sides) that are located just after the last windows contain the air filter if I am not wrong. So Eden it rains how is water movement controlled so as to not interfere or enter into the air filter?

The problem is more woke on move as water is forced inwards due to aerodynamics. Can someone clear my doubt here. Sorry for a noob doubt.

Anurag.

The air filter is in the engine compartment. The slats you see are the intake. Just like in a car, you have an intake pipe to the air filter box and the filter sits in the box.
The intake pipe most probably will have a hole or some other way to let the collected water out.
We were discussing the same in the Figo thread that there is actually a hole before the air filter box to let water out.
Experts can correct me.

[audioholic]

I had the same doubt as Anurag. But I noticed that most CVs have their air intake set high up, and most of the times quite exposed. However, to the bottom of the intake pipe, there is a U bend, before it enters the engine area where the filter sits. Hence I think the water will get collected there instead of entering the air filter. Think it should be the same in the Volvo.

Regarding the hissing sound, there can be different sources. Having travelled regularly during my Pre University days in the Volvo city bus, I did dig deeper into the matter.

1. Under hard accelaratiom, the hiss comes from excess pressure being released from the turbocharger. If we notice the boost guage, it will go to the yellow mark as soon as which the pressure is released bringing it back to the green region.

2. Air can also be released from the braking system in case there is imbalance in the brake pressure or so. I think even the ABS mechanism works by releasing air pressure from the caliper.

3. The suspension also releases air once in a while and levels itself. Noticed this in signals after the bus stops. But this is louder.

[a4anurag]

Originally Posted by audioholic

I had the same doubt as Anurag. But I noticed that most CVs have their air intake set high up, and most of the times quite exposed. However, to the bottom of the intake pipe, there is a U bend, before it enters the engine area where the filter sits. Hence I think the water will get collected there instead of entering the air filter. Think it should be the same in the Volvo.

This is what Volvo website has to say about the Air intake in its buses:

Dual air intake: The Volvo 9400 6x2 has a dual air intake placed above the engine to avoid the suction of road dust and water into the air filter. This helps in keeping the engine cleaner and reducing operating cost.

Originally Posted by audioholic

1. Under hard acceleration, the hiss comes from excess pressure being released from the turbocharger. If we notice the boost gauge, it will go to the yellow mark as soon as which the pressure is released bringing it back to the green region.

I love that sound and die for it.


I want such a gauge installed in my Swift too! Any possibilities?

Originally Posted by audioholic

2. Air can also be released from the braking system in case there is imbalance in the brake pressure or so. I think even the ABS mechanism works by releasing air pressure from the calliper.

Braking is via the Hydraulic retarder with EBS 5. So the point of water entering the braking system is ruled out.

Originally Posted by audioholic

3. The suspension also releases air once in a while and levels itself. Noticed this in signals after the bus stops. But this is louder.

This keeps on happening while on the move too but frequent enough but yes as you said is louder and distinctive. Worst is under heavy braking.

Anurag.

[audioholic]

Originally Posted by a4anurag

Braking is via the Hydraulic retarder with EBS 5. So the point of water entering the braking system is ruled out.

You seem to be mistaken. Retarder is an additional brake along with the service brakes. The retarder runs on hydraulic friction whereas the service brakes are the usual air brakes. The EBS system blends these two together and depending upon the need, uses either or both together. There is no mention of water entering the braking system. The case is about water entering the air intake.

Originally Posted by a4anurag

This keeps on happening while on the move too but frequent enough but yes as you said is louder and distinctive. Worst is under heavy braking.

Anurag.

Under hard braking, it will be the ABS which will release air pressure from the brakes to prevent skidding. In case of a hydraulic brake like our cars, ABS controls the flow of oil into each brakes but in air brakes, since air is not a fixed consumable, it is just exhausted out.

The boost gauge info can be obtained through the OBD adapter itself. Apart from that there are aftermarket boost gauges.