Helmholtz Exhaust 2012

[strad]

Could these chambers be used in formula 1 to prevent the exhaust from cracking due to resonance?

I'm not sure you're not onto something there. In the past many a race was ruined by a cracked exhaust.

[aussiegman]

So, what's the difference between placing a Helmholtz resonator on the exhaust header (manifold) and placing one further down the exhaust pipe (where Ferrari have placed their chamber)? At what point along the exhaust is the Kadenacy effect no longer applicable?

With reference to a Helmhotz Resonator, placing one on an individual exhaust runner would see it primarily affect that cylinder correctly and likely cause uneven reversions in the other runners. You could in theory have one per runner however it is possible to set up other strange harmonics and/or resonances.

Placing in the merged exhaust pipe as Ferrari has done is the the most efficient application and more evenly spreads the effect across the runners. Distance away for the exhaust valve would decrease the direct effect at that particular interface due to dispersion and interference, however it would be a case of crunching the numbers and testing to determine most efficient size and placement.

With regard to Kadency Effect, the practical application theory differs between proponents, however the primary source of the effect is a compilation of greatest change in diameter or merger of flow and the distance from where the originating source of the pressure wave.

Typically the first of either a diameter transition or flow merger is where the greatest effect is garnered. You can have complimentary transitions or mergers such is in the Ferrari exhaust shown.

In other application, longer primaries in 4-1 designs vs. 4-2-1 setups show differing application of the effect. However the extra complexity usually gains a reduction in any single benefit from my experience. Again, it would be a case of doing the maths and practical testing to find the best compromise in the solution.

[autogyro]

Brings back memories.
Four cylinder BMC A series and For Kent engines.

A series had three exhaust runners (siamesed middle exhaust port.)
3 into two into one gave a good exhaust scavenge at each join and resulted in a wide rpm increase in power.
3 into one collector gave a bit more at the top end for a loss of tractability.
72 inch open exhaust out the side worked best.

On both we used an exhaust manifold dowel pinned to the head for alignment using larger pipe than the port size, to leave a step at the head face so as to prevent pulses returning to the exhaust valves.

Balancing the pulses is better than trying to dump them in a collector.

[PlatinumZealot]

So, what's the difference between placing a Helmholtz resonator on the exhaust header (manifold) and placing one further down the exhaust pipe (where Ferrari have placed their chamber)? At what point along the exhaust is the Kadenacy effect no longer applicable?

With reference to a Helmhotz Resonator, placing one on an individual exhaust runner would see it primarily affect that cylinder correctly and likely cause uneven reversions in the other runners. You could in theory have one per runner however it is possible to set up other strange harmonics and/or resonances.

Placing in the merged exhaust pipe as Ferrari has done is the the most efficient application and more evenly spreads the effect across the runners. Distance away for the exhaust valve would decrease the direct effect at that particular interface due to dispersion and interference, however it would be a case of crunching the numbers and testing to determine most efficient size and placement.

With regard to Kadency Effect, the practical application theory differs between proponents, however the primary source of the effect is a compilation of greatest change in diameter or merger of flow and the distance from where the originating source of the pressure wave.

Typically the first of either a diameter transition or flow merger is where the greatest effect is garnered. You can have complimentary transitions or mergers such is in the Ferrari exhaust shown.

In other application, longer primaries in 4-1 designs vs. 4-2-1 setups show differing application of the effect. However the extra complexity usually gains a reduction in any single benefit from my experience. Again, it would be a case of doing the maths and practical testing to find the best compromise in the solution.

But in all of what you have said, you have not stated what you think it is used for.

[bill shoe]

Interesting that you mentioned Resonance. I know resonance can have damaging effects on a machine. So I am going to put another view out there:

Could these chambers be used in formula 1 to prevent the exhaust from cracking due to resonance? In other words to increase the life of the exhaust. Paddy Low said that a typical F1 exhaust only last about 1000km.

Durability is obviously difficult on F1 exhaust bundles, but I doubt durability explains any resonators. On production cars bad vibrations are typically dealt with by putting little rubber mass dampers on the pipe (for lower frequency problems), or just rigidly fixing little masses to the pipes in good locations (for higher freq problems). I think we saw some of the latter on 2011's blown exhaust outlets.

[mep]

We know that engine tuning is done by optimizing exhaust length in order to improve gas exchange with pressure waves travelling trough the exhaust and the intake. The more the exhaust is optimized for maximum power output the more it will be limited for that particular engine speed. At different engine speed the wave interactions can become counterproductive resulting in a engine with high peak power but very poor power at low rpm's or even a power drop at one particular speed. Adding a additional pipe into the exhaust which reflexes pressure waves can increase the possibilities for engine tuning and generate interactions which help for low rpm power. Where there is one major difference to the exhaust opening. A open pipe end reflexes a high pressure wave as low pressure wave whereas a closed pipe end reflexes a high pressure wave. However that should just influence the pipe length which is required. The position of the junction and the length of the additional pipe is important for the engine speed which should be tuned. In general the longer the exhaust the better the power at low engine speed. It could be possible that the exhaust pipes become too long, in order to reach the diffusor, to allow for efficient engine tuning. So the resonator could be the main tuning pipe. Maybe the low pressure in the diffusor is not helpful for engine tuning either so the closed pipe end of the resonator could help there.

[Tommy Cookers]

This sort of thing seems to have been around for 60 or more years (that is for performance benefits, not as a Helmholz acoustic device). It could be used before or after the merge, mainly to compensate for non-ideal lengths or layout otherwise present.

As the previous post suggests, here it could be compensating for a non-ideal pipe length after the merge.

Alternatively it can also improve the powerband (generating another low pressure event it can extend the duration of the overall low pressure period).
Was its use related to a particular circuit ?

I did not expect in 2012 to see a reference to Kadenacy, wasn't the impact of his work diluted by a basic lack of supporting results ? Has he been vindicated in later work by others ?

[aussiegman]

But in all of what you have said, you have not stated what you think it is used for.

I thought I had in my first post. No problem, my personal expectation is that the Helmhotz Resonator tube is likely being used to increase the efficiency of the "Kadenacy Effect" in a specific RPM range of the engine to maximise cylinder filling and efficiency.

Resonator tube lengths and exhaust runner lengths could in theory be altered to suit various tracks to account for requirements of the engine in relation to its expected operating envelope for maximum efficiency or to compensate for a specific gap in the torque profile of the engine. The increased torque could be used in concert with gear ratio selections, aero changes or other variable on the car.

So by altering the volume of the closed end tube as well as runner length, you effectively alter the tuning range (RPM) at which the resonance effects are either most synergistic and beneficial OR at which the resonance effect could work to cancel out a specific pressure wave which may be detrimental.

I do not believe the primary purpose is to alter the sound of the exhaust as there is no measurable benefit or need to do so under the regulations. Also I do not think it is to remove harmful resonances to avoid cracking of the manifold as there are better ways to achieve this without the weight penalty, packaging constraints or complexity of introducing unwanted resonance effects into the exhaust stream.

I have listed below the methods I would expect to be employed to achieve increased structural integrity over the use of a resonator tube when accounting for the extra packaging requirements, weight penalty and added complexity of a resonator tube in addition to the need to calculate and minimise possible negative effects.

1: Simply increasing material thickness and/or additional support structures on the external surface of the manifold. These would likely weigh less than the addition of a resonator tube if executed properly; or
2: The attachment of individual weights as mass tuned dampers to remove specific resonances on the runners by altering the effective resonance of the runner. Again much lower weight and minimal packaging penalties vs. using a Helmhotz Resonator tube.

Both of these methods do no introduce the possibility of adverse internal pressure waves and/or resonances within the runners that could interfere with the specific tuning length resonance of the exhaust runner.

[PhillipM]

Wow that's really thin! Almost paper thin!
0.065" wall stainless is pretty difficult to weld as it is. I wonder how they weld that?

Well, it used to be by one old bloke in his garden shed.

[Speng]

Could these chambers be used in formula 1 to prevent the exhaust from cracking due to resonance?

I'm not sure you're not onto something there. In the past many a race was ruined by a cracked exhaust.

They are used in gas turbine (and I think rocket engine) combustors for that purpose. In a combustor you can (often) have strong aeroacoustic resonances which can cause structural damage and Helmholtz resonators have been used to damp these vibrations. I would imagine they can be used to make your exhaust sound suitably rorty but these aren't M3 engines for wanker stockbrokers. I supposed they could have a scavenging effect as well. I doubt the accumulator idea for blown aero as i think the volume is probably too small. Then again it's all about aero nowadays isn't it.

[bhall]

Speaking of rocket engines, this is how NASA dealt with harmful acoustic energy during Space Shuttle launches.

Starting about seven seconds prior to liftoff, 350,000 gallons of water was released through six nozzles onto the surface of the launch platform. It took 41 seconds and reduced reflected acoustic energy by half.

(FYI: The SPL of a Shuttle launch was about 170 dB. Really, really loud.)





I'm not quite sure this technology will ever make its way to F1, though.

[Richard]

The Helmholtz Exhaust is popping up on more cars so I've updated the topic title to remove the Ferrari ref.

[Ferraripilot]

This technology is simply, yet perfectly exampled in pre-war Bentley's where many of them have specifically designed handles which further tighten or 'close' the exhaust to apply more back-pressure. On one Bentley of this vintage, I saw a plate which advised, "pull lever for more torque for going up hills" or something to that effect.

[cheapracer]

Just an exploratory discussion about using closed ended resonating chambers on the exhaust. It has been applied in F1 by Ferrari in 2011 as far as I can tell. I have seen these before Many Years ago on the internet but I cannot seem to find the picture. It was done on a BMW M3 with each exhaust header runner having it's own closed end cannister.

Been around since Noah was water skiing.

I just read the tech article by Tomba here http://www.f1technical.net/development/369 and got to say it's pretty bad with a sound lack of knowledge of what the blind chamber does. It is merely a volume device that has time to have some effect/function at slow speeds and is literally bypassed/ignored with kinetic energy at hi flows. It does NOT "accumulate exhaust gases when pressure is high in the exhaust pipe" in the context that has been put forward.

I added these as a teenager to my dirt bikes, Yamaha applied the same theory to their intake systems in the millions in the 80's as well as patents for similar and Honda released a number of motorcycles with the extra blind pipe as did Kawasaki although mostly Honda and Kawasaki's chamber had a valves that opened and closed giving access to the extra volume.

Anyone who wants to know how they work and the mathematics for it can be found in one of the most common and famous tuning books out there, circa 1971 ... a large chunk of a chapter is devoted to it from memory.

http://books.google.com.hk/books/about/ ... ZTAAAAMAAJ

The main reason for use is it's a ability to flatten out torque curve's a little due to the extra volume softening the return wave as well as making 'off cam' to 'on cam' transition a little smoother making an engine a little more driveable with fuel consumption most likely fractionally improved - I would think it's the fuel consumption improvement F1 is chasing.

[Greg Locock]

The easy way to think about a Helmholtz is that it is a little mass on a spring device. The mass is the plug of air in the neck of the sidebranch. The spring is the elasticity of the air in the chamber itself.

The interesting part is that the friction of the plug of air in the neck acts as damping.

So a Helmholtz is a tunable way of adding damping to a duct at a particular frequency, at a very small penalty in back pressure.

If you change the proportions so that it looks more like a quarter wave tuner, ie by increasing the neck diameter, then you get less friction damping and more cancellation. The tuned frequency also shifts, and you get effects at harmonics.