Ferrari F2012

[Gridlock]

There's a defined aperture size, yes, but it's quoted as a combined figure for exit area across both exhausts and I can't be arced to look it up, it works out to about 12cm diameter from memory.

[bhall]

when driver releases the throttle does the gases from the collector have any speed to benefit downforce?
what makes the gases go out? negative pressure? vacuum?

Think of it as collected volume under pressure.

On-throttle exhaust gasses fills the chamber as they're being ejected from the exhaust pipes. Once the chamber is full, the exhaust gasses maintain pressure in the chamber. When the driver goes off-throttle, the collected volume is released due to the release of pressure within the exhaust. The release from the chamber provides added exhaust volume to off-throttle blowing.

The effect is not massive. It just helps to stabilize the transition.

EDIT:

There's a defined aperture size, yes, but it's quoted as a combined figure for exit area across both exhausts and I can't be arced to look it up, it works out to about 12cm diameter from memory.

Are teams forbidden from adjusting the diameter anywhere along the length of exhaust? A simple pinch somewhere is all that's needed to adjust back pressure.

[Gridlock]

when driver releases the throttle does the gases from the collector have any speed to benefit downforce?
what makes the gases go out? negative pressure? vacuum?

The pressure differential will pull it out, yes. In principle I don't think it's doing much useful mid-corner gas ejection, it's more to smooth the transition from on- to off-throttle rear df levels. IE it turns a near-cliff edge graph into a more graceful slope. Off the top of my head this would allow a more sudden throttle body closing map (ECU controlled don't forget) which will aid engine braking more than slowly closing it to keep gas flowing.

Between the engine and the last 10cm, as far as I can tell, do what you want as long as there's no openings. I'm fascinated by the variety in manifold shapes given the stability of engine regs for 5 years and the near-identical fairing shapes and exhaust exit locations.

[bhall]

I'm fascinated by the variety in manifold shapes given the stability of engine regs for 5 years and the near-identical fairing shapes and exhaust exit locations.

Better not repeat that, lest the powers-that-be narrow down those regulations, too.

[hardingfv32]

The exhaust branch is there to change the operating range of the tuned exhaust. I would say they are simply lengthening the exhaust system but without the packaging issues that would create.

Brian

[bhall]

No, it's definitely about stabilizing the abrupt loss of downforce when going off-throttle. I read about it here last year.

[PlatinumZealot]

Nope that is not why it is there. It is there to help the engine make more power at the designed RPM.

BMW used to do this in the E30 M3 back in the late 1980's. I don't remember what racing series though.

But anyway it is done for engine power characteristics. Whether it be low down power etc.

[bhall]

How does it help engine power characteristics?

[Owen.C93]

It will have a resonance which you can tune to help reduce resistance in the pipe at certain RPMs.

[bhall]

But how? I looked up Heimholtz resonance, which is what I assume we're talking about, and I don't see how tuning that phenomenon would reduce resistance. If anything, it adds resistance due to the fluctuations inherent to harnessing it.

Wouldn't it make more sense to just redesign the header for this purpose?

I don't mean to seem incredulous, I'm just not understanding the concept as it's been presented.

[PlatinumZealot]

Still trying to look for the header as I remember it years ago when i saw it on the internet, but this is closest I have come.

http://commons.wikimedia.org/wiki/File: ... 935%29.jpg

[hardingfv32]

Wouldn't it make more sense to just redesign the header for this purpose?

Absolutely, if you have the space. I assume that the exhaust outlet location has a desired fixed location. This would be a way to change the engine output curve without too much packaging drama.

This is not about creating less resistance. It is about changing the tuning wave form location or the wave form peaks. Heimholtz resonance is on point.

Brian

[mx_tifoso]

Please take exhaust discussion here from now on:
Helmholtz Exhaust - as seen on Ferrari F150/F2012

Whether any previous posts from here will be moved there is yet to be seen.


All posts after this one were talking about the car's performance in Monaco so they were moved there.

[Crucial_Xtreme]

Monaco Front Bulkhead Detail



Front Brake Ducts



RW- No V-Groove/ No straight louvers



Flo-Vis Monakey Seat

[Mazdaboy]

Flow vis on the Monaco-spec rear wing: