Air Box, what's that all about?

[shimmy]

Why does the CSL air box make such a difference to noise and more importantly bhp?

All else being equal I have witnessed that if you flap is stuck shut the CSL looses 0-30 bhp between 5200-8000rpm levels compared to a normal working flap with sport on.

This proves surely that with sport button OFF you are loosing say 0-15/20 bhp between 3500-5200rpm when the flap is shut but that all kick back in when the flap opens.

BUT the question I am asking is why does the air box work and how does the ram effect work?

[glendog74]

Originally Posted by shimmy

Why does the CSL air box make such a difference to noise and more importantly bhp?

All else being equal I have witnessed that if you flap is stuck shut the CSL looses 0-30 bhp between 5200-8000rpm levels compared to a normal working flap with sport on.

This proves surely that with sport button OFF you are loosing say 0-15/20 bhp between 3500-5200rpm when the flap is shut but that all kick back in when the flap opens.

BUT the question I am asking is why does the air box work and how does the ram effect work?

Why not just PM The Gorilla? Save us the pain lol

[shimmy]

Originally Posted by glendog74

Why not just PM The Gorilla? Save us the pain lol

At a certain age you stop learning Rob. try to fight it or just curl up and slowly go bonkers

[glendog74]

Originally Posted by shimmy

At a certain age you stop learning Rob. try to fight it or just curl up and slowly go bonkers

Bless you - how is the whole bonkers thing going?

[DuncanR]

Not having read the manual yet, if you dont have a flap, is pressing the sport button pointless ?

[mattCSLnut]

Originally Posted by shimmy

At a certain age you stop learning Rob. try to fight it or just curl up and slowly go bonkers

Ahhh... that explains everything Shim

[alexk]

Hey shimmy, I love your threads

My contribution here :
1. Why does it make noise ?
Because it's made of carbon (the acoustics of carbon are different from plastic. There is less filtering of the induction noise (the velocity stacks) and more amplification of it) and because it's significantly bigger than the standard S54 intake. I am sure Gorilla will have the volumetric numbers in litres.

2. Why does it produce more hp.
The combination of alpha-n (pseudo as Gorilla says) with the extra air-supply makes the engine produce more hp... plus the ram air which is point 3.

3. How does the ram air works.
As the car picks up speed, air with higher velocity enters the ram air intake in the front bumper which is sent to the intake.
The air is colder and with speed (instead of the typical NA engine behavior having to suck air, you send air with pressure).
More air, colder air + Alpha-N = more HP.
I have some interesting measurements of the intake air temperature with same rpms with different speeds (from 60 up to 260 km/h).
You will be surprised. I will find my notes and post them.

4. Stuck flap = loss of ponnies
This is the opposite of point number 3.
Less air, not so cold air, no ram-air ... so less output.

And I have a question which is also the usual headache of bikes with ram-air.
How do you simulate in a dyno the air pressure in the ram air of the CSL at 250km/h ?
You don't... so the dyno shows 20-30 hp less
(bikes gain 8-15hp from the ram-air in speeds more than 180km/h in the 180hp scale).

[The Gorilla]

Hi,

As Alexk has posted, Ram Air is important.

The CSL Airbox [Plenum] has an
achilles heal though, in that the Air Filtre
is located to close to the Intake runners.

This acts almost like a second flap
that can not be opened.

The Ram Air [ velocity] is reduced when
passing through the filtre.

Filtre further away from the TB's mouth with
a good Intake path would give a better velocity
into the TB's.

The Intake Runner length and its form is also critcal to the engine.

Leave those shiny Chinese Carbon Airboxes well alone !!

On the E30 M3 DTM cars [S14 ENGINE] they had several Intake
runner lengths to their Carbon Airboxes pending
if they required more Power or Torque from the
Engine.

15cms intake runner was used on the more shorter
Sprint races for Torque and then they would fit the
longer 17cms + for the more endurance type
Races where they needed to improve power Gains.

This was on either 48mm TB's or 49.5mm Slides.

I have a set of E30 M3 BTCC Zytek slides here which
were fitted to an S14 in an E36 Compact.

The Intake runner lengths were increased by about 30/40mm
something you can do with the S14 in the E36 Shell,
and the engine Power increased by around 18/20 BHP..

So proper Carbon Airbox tuning is a real science not
just noisey bling.

Regards,

The Gorilla.

[mattCSLnut]

Originally Posted by The Gorilla

Hi,

As Alexk has posted, Ram Air is important.

The CSL Airbox [Plenum] has an
achilles heal though, in that the Air Filtre
is located to close to the Intake runners.

This acts almost like a second flap
that can not be opened.

The Ram Air [ velocity] is reduced when
passing through the filtre.

Filtre further away from the TB's mouth with
a good Intake path would give a better velocity
into the TB's.

The Intake Runner length and its form is also critcal to the engine.

Leave those shiny Chinese Carbon Airboxes well alone !!

On the E30 M3 DTM cars [S14 ENGINE] they had several Intake
runner lengths to their Carbon Airboxes pending
if they required more Power or Torque from the
Engine.

15cms intake runner was used on the more shorter
Sprint races for Torque and then they would fit the
longer 17cms + for the more endurance type
Races where they needed to improve power Gains.

This was on either 48mm TB's or 49.5mm Slides.

I have a set of E30 M3 BTCC Zytek slides here which
were fitted to an S14 in an E36 Compact.

The Intake runner lengths were increased by about 30/40mm
something you can do with the S14 in the E36 Shell,
and the engine Power increased by around 18/20 BHP..

So proper Carbon Airbox tuning is a real science not
just noisey bling.

Regards,

The Gorilla.

Reading the Primates posts with interest and learning something new every day

[alexk]

Gorilla you are spot on as usual.

The difference of the S14 carbon airbox is that the air funnels (aka velocity stacks) are embedded on the carbon intake (as on most racing intakes) while the CSL has them seperate inside.
You could play with the funnels in the CSL and as Gorilla said move the powerband (shorter for higher HP in high rpms and longer for more torque in the low-mid range).
I haven't seen anywhere funnel options for the CSL airbox... I guess Gorilla can confirm this.


PS1 : I have played with different funnel sizes in my previous bike... my current has a very cool system with servos on the funnels. So in the low rpms a 'second' funnel is making the length longer and on the high rpms the servos move higher the 'second' funnel and make the length shorter.


PS2 : I have driven R1 with the ram air tubes removed... the performance difference is shocking. What the manufacturers claim is true... so amplify this in a 3.2 high revving CSL engine.