550 exhaust performance, engineering question

[Mario149]

Just found this:

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EXHAUST

The Maranello’s insulated stainless steel exhaust system employs variable back pressure through bypass valves situated on the rear silencers. The bypass valves are electropneumatically actuated by the engine management system, based on engine speed and throttle opening. Varying back pressure makes it possible to optimize engine efficiency in various conditions. Greater back pressure allows higher torque under average load, while lower back pressure enhances full load engine efficiency.

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on here: http://www.topspeed.com/cars/ferrari/1996-2001-fer...

and it doesn't make sense to me. I always though you wanted as little back pressure as possible regardless of engine speed and that the valve was only there for noise regs??

[Mario149]

roygarth said:

Does this system still work if Tubi rear silencers are fitted?

On my previous 550 Tubis there was no valving, and QV confirmed that that was correct when they inspected the car

[Mario149]

FerrariV8 said:

Whether you need to intergrate both banks or run as two separate engines - jury is out, we've tried separate for the last two race seasons, this year were joining both banks, i'll report back after testing.

T.

Interesting, I had the x pipe removed on mine and replaced with 2 separate ones. Whatever it does to the power, it makes it sound better

[Mario149]

It's distorted due to iPhone and car park, but here: http://www.youtube.com/watch?v=uYxPw0B_Ab4

[Mario149]

FerrariV8 said:

Tubi's do not have valves but still have a degree of back pressure, with some 360's certain cheaper systems can put the engine light on - probably from a lack of back pressure?

T.

Out of interest, do you know what sort of %tage difference in torque we are talking (boom boom) about when comparing standard mufflers closed vs standard mufflers valves (wired) open at low revs?