33 replies to this topic

[footprints]

I saw the close up photos of the R25 and heres a picture of their collector, its really nice especially the way it blends to the tubing at the end. Are these kind of collectors available in the market? What are the benefits? It is also a stepped manifold design.

[Greg Locock]

MAC True Fit Long Tube Headers on http://www.proficien...nce.com/mac.php

Yes, the smooth blend reduces the reflection back from the first change of area (a bit (not very much)) and will reduce back pressure a bit. Not night and day, but every little bit helps.

[Powersteer]

The smooth shape into the main exhaust is organic sexy. I wonder how do they time the step phase. That is the most drastic step phase I have ever seen.

[footprints]

Thanks greg, i've checked out the link you posted, but they do not show similar collectors on their website.

Yes, its real sexy. Those are inconel tubing i suppose? Its just so well constructed. They dont look like they are sections off a straight tubing, rather from a mandrel bent tubing but how it flows to the main outlet is just incredible. How did they build that by hand?

[hyperbolica]

First-class plumbing. Beautiful.

Another question: that "radius rod" behind the exhaust, connecting some suspension part to the chassis does exactly what?

[Powersteer]

Originally posted by hyperbolica
First-class plumbing. Beautiful.

Another question: that "radius rod" behind the exhaust, connecting some suspension part to the chassis does exactly what?

Its bracing for a full stress member engine. It relieves some tension away from the engine which is an integral part of the chassis. Now its possible to see this as the new V8 engine is much more compact allowing more useable space.

[hyperbolica]

Thanks a lot! Thought it was more than a brace.

[Engineguy]

Powersteer seems to be talking about the one running forward and upward to the back of the tub. The one rearward from the cylinder head is probably to prevent fore/aft deflection of an upper wishbone inner pivot point bracket that is cantilevered laterally outboard from the gearbox housing.

[Powersteer]

I guess both rods are "behind the exhaust" By the way, why is the central spring not set up the way Luke Pellerins designed it? That set up (on the pic), designed around the central rod connected to the tree, is the roll bar purely for roll and the central spring purely for vertical force or is there hidden torsion bars each for a wheel???

[desmo]

...and here's a look at a couple of F1 5 into 1 collectors from inside.

[cosworth bdg]

Originally posted by desmo




...and here's a look at a couple of F1 5 into 1 collectors from inside.

What you have shown above we were doing 40 years ago with [4 into 1 ] collectors and won 2 world F1 championships. in a row................................................................................................................................................... .......................................

[shaun979]

I've seen the 2003 Jordan engine by Cosworth and the collector interior looks just like that.. kind of rounded at the welds. Is there a reason they don't leave it sharp?

[Canuck]

Desmo do you have the corresponding exterior shots of that collector? In the first photo it appears as though there's more than one angle at play, almost like it's twisting rather than arcing. Can anyone shed light on whether that's by design or by packaging needs? If by design, to what end?

[hydra]

Hasn't anybody else found it odd how the header doesn't look to have any sort of ceramic coating on it - to reduce the thermal load on the cylinder head if not for anything else?

[12.9:1]

Burns Stainless

You'll find them here, not F1 but same style


F1 exhausts are fabricated from 1 to 1.5mm Inconel (approximately 60% Nickel and 22% Chromium + trace Molybdenum and Niobium) operating temp 1000C - work of art, good for one race

[McGuire]

Originally posted by hydra
Hasn't anybody else found it odd how the header doesn't look to have any sort of ceramic coating on it - to reduce the thermal load on the cylinder head if not for anything else?

A thermal-barrier coating or wrap would be very hard on the tubing in this application.

[McGuire]

Originally posted by Canuck
[b]Can anyone shed light on whether that's by design or by packaging needs? If by design, to what end?

I can't imagine it's any more than packaging.

[desmo]

Originally posted by Canuck
Desmo do you have the corresponding exterior shots of that collector? In the first photo it appears as though there's more than one angle at play, almost like it's twisting rather than arcing. Can anyone shed light on whether that's by design or by packaging needs? If by design, to what end?

Yeah, McGuire's got it right. The top one is from the F2000 I think and bottom one is the F2002GA. The apparently odd geometry of the top one is due to the arrangement of the header pipes leading into the collector. They'd got the header design more bilaterally symmetric leading into the collector for the F2002GA.

[Canuck]

Figured I'd better ask before I assumed anything one way or the other. There seems to be a complete lack of agreement on the precise design and construction of headers that I never know who's selling smoke and mirrors and who has it sorted. One source will say that a stepped-header is a crutch for inadequate length while the other says the small wave reflection generated at the step is of benefit. Another source says reverse-cone megaphones are a quaint style of the past while the others (notably Burn's Stainless at this point) say it's a necessary piece of the system (while noticeably absent on the F1 exhaust above).

[Halfwitt]

Originally posted by 12.9:1
Burns Stainless

You'll find them here, not F1 but same style


F1 exhausts are fabricated from 1 to 1.5mm Inconel (approximately 60% Nickel and 22% Chromium + trace Molybdenum and Niobium) operating temp 1000C - work of art, good for one race

Some people are running thinner material than 1mm for their exhausts these days.

I think if people in F1 had seen any benefit in performance simulation, then they would at least dyno test a megaphone system, and if it proved worthwhile, they would try hard to package it on the car.

[cosworth bdg]

Originally posted by Halfwitt


Some people are running thinner material than 1mm for their exhausts these days.

I think if people in F1 had seen any benefit in performance simulation, then they would at least dyno test a megaphone system, and if it proved worthwhile, they would try hard to package it on the car.

How very true ,in what you are saying...............................................

[cosworth bdg]

[QUOTE]Originally posted by Halfwitt
[B]

Some people are running thinner material than 1mm for their exhausts these days.

Weight is what it is all about with the thinner materials being used these days.....................................................

[wheelock]

There seems to be a lot of carbon fibre laminate in close proximity to those pipes, I guess they
must use suitable shielding [not shown?] or a very hi temp epoxy.


Mark

[Canuck]

Originally posted by Halfwitt

I think if people in F1 had seen any benefit in performance simulation, then they would at least dyno test a megaphone system, and if it proved worthwhile, they would try hard to package it on the car.

This is why I asked. To say that because it's not used in F1 therefore it must not be of value seems correct, but then the papers I have by Honda, and the only exhaust design book I've ever found, The Scientific Design of Exhaust and Intake Systems both say otherwise. I'd like to know why they're not of use.

[McGuire]

I believe the megaphone and reverse cone provide an incremental gain, but which is trumped by packaging in this case.

[Greg Locock]

From an acoustics point of view, fancy shapes, and logic based on water flows, don't really apply.

If a feature is smaller than about 1/10 of a wavelength, acoustically it doesn't have any shape, it is either a hole or a blockage.

So in an F1 engine at 18000 rpm, assuming we are looking at one bank, and they are equally spaced, and the temperature is say 600 K, the frequency of the fundamental is 18000/60/2*4, 600 Hz, so the wavelength is about 0.7 m

So, your megaphone actually just looks like a hole.

There is one refinement that does matter, that is the lead in angle on expansion features. If this is too great (7 degrees to 15 degrees sticks in my mind) you'll get separation on the way in, increasing the turbulence.

Now, the exhaust pressure is not just a fundamental, it will have both even and odd harmonics (mostly odd at a rough guess) and even some half orders, so the wavelengths of these will be a lot smaller, and fancy geometry on the scale of the diameter of an exhaust pipe will start to become important. However, the vast majority of the energy (say 75%) is at firing frequency, everything else is perhaps 25% of the energy.

Reflection at a tapered termination will occur at different distances for different wavelengths, this tends to break up each wavefront (composed of a whole stack of frequencies that are in phase).

[Canuck]

Originally posted by Greg Locock
From an acoustics point of view, fancy shapes, and logic based on water flows, don't really apply.

If a feature is smaller than about 1/10 of a wavelength, acoustically it doesn't have any shape, it is either a hole or a blockage.



So, your megaphone actually just looks like a hole.



Reflection at a tapered termination will occur at different distances for different wavelengths, this tends to break up each wavefront (composed of a whole stack of frequencies that are in phase).

To be fair, I'm not sure I've quite got my head around 100% of what you've said but I've drawn the following conclusions. All of the info I've read regarding exhaust has been about sound, not water so I believe we're on the same page.

What you've said in the first half of your post is that the combination of factors, but primarily the engine speed, reduce the possible effectiveness of a megaphone to nil, correct? In essence, the megaphone, to quote McGuire, may provide an incremental or subtle gain but not in this application.

Re the last couple of sentences in your post . The megaphone theory that I've read, and it's all rather short and vague, suggests it broadens the power under the curve. Your "reflection at different distances for different wavelengths" statement seems to fit hand in hand with that theory, as the rpm changes, so will the wavelength right?

[Greg Locock]

Not nil, just small.

"Re the last couple of sentences in your post . The megaphone theory that I've read, and it's all rather short and vague, suggests it broadens the power under the curve. Your "reflection at different distances for different wavelengths" statement seems to fit hand in hand with that theory, as the rpm changes, so will the wavelength right?"

Yes. The tradeoff being that at the peak the gain will be less than with a flat end. So you are accepting a lesser peak in exchange for a fatter one.

[Canuck]

Fantastic! That's so much better than "we don't use it 'cuz them boys over in F1 ain't usin' it neither". I'll be the first to say I'm after fatter, broader torque. It's also nice to know I'm not misunderstanding the research I have at hand. Accordingly, the research further suggests that stepped primary tubes perform a similar function with small rarefaction waves starting at each step, with the wave caused by the next step following close behind and so forth. It also suggests a similar trade-off - greater average in exchange for lower peak. This ties in nicely to my thread that started life as a valve-train speed question (which hasn't actually been confirmed or denied yet come to think of it).

[Calorus]

Originally posted by Canuck
Fantastic! That's so much better than "we don't use it 'cuz them boys over in F1 ain't usin' it neither". I'll be the first to say I'm after fatter, broader torque. It's also nice to know I'm not misunderstanding the research I have at hand. Accordingly, the research further suggests that stepped primary tubes perform a similar function with small rarefaction waves starting at each step, with the wave caused by the next step following close behind and so forth. It also suggests a similar trade-off - greater average in exchange for lower peak. This ties in nicely to my thread that started life as a valve-train speed question (which hasn't actually been confirmed or denied yet come to think of it).

Another point regarding the prevalence of a megaphone system in Drag Racing rather than in F1: Turbo chargers.

For a trubo charged engine, everything after the Turbo is an efficiency loss, as it increases Exhast pressure & temperature without providing work. A Mega phone system, with or without a refelector, may retain some of the wave reflection but reduces the back pressure which can (in appropriate circumstances and quantities) be benficial in a Normally Aspirated engine. My question would be "what do the IRL boys do?"

[shaun979]

Calorus, the current IRL exhausts are straight forward and are kind of a spec piece with only two approved suppliers IIRC. Have never seen a megaphone style exhaust on any of the current cars.

[Canuck]

Originally posted by Calorus


Another point regarding the prevalence of a megaphone system in Drag Racing rather than in F1: Turbo chargers.

For a trubo charged engine, everything after the Turbo is an efficiency loss, as it increases Exhast pressure & temperature without providing work. A Mega phone system, with or without a refelector, may retain some of the wave reflection but reduces the back pressure which can (in appropriate circumstances and quantities) be benficial in a Normally Aspirated engine. My question would be "what do the IRL boys do?"

Maybe I'm not quite understanding what you're saying but there's no turbo in F1 anymore, and perhaps only a handful of NHRA classes (none that I'm familiar with myself but I don't follow the Tuner stuff) that allow turbochargers. The drag exhaust in question was promoted by Burns Stainless.

[Greg Locock]

Calorus - "may retain some of the wave reflection" - this may not apply in a racing series, but for a road car the inertia of the rotor is matched to the aeroelasticity of the air, such that it forms a tuned system to absorb the pressure pulses from the exhaust. If you measure the speed of the rotor during one revolution of the engine it varies rhythmically by about 50% as each wavefront hits it.

This is done to absorb as much energy as possible.

Consequently there is very little acoustic energy left in the exhaust after the turbo, so we use high frequency absorption rather than expansion chambers.

So, a megaphone won't be much good, because there isn't much to reflect.

[Calorus]

Thanks, Shaun - unfortunately that doesn't take us much nearer, since we don't know if the system is an optimised for thermal and sonic resonance solution, or if it's a on size fits all good enough to do solution.

Sorry, Canuck - yeah, just a little misunderstanding, I know that the F1 engines are normally aspirated, the reason I was particularly interested in the IRL soultion, was that they are the only even vaguely comparable Turbocharged circuit engines, and even then they are designed around intentional restrictive flaws - but a comparison between two similar applications with different aspiration types may have yielded interesting results had not the IRL technology embargo been in force as Shaun pointed out.

Thanks Greg, in that case can you shed a little light on the possible reasons for the sharp angle contractions typically seen at the end megaphone style exhasts? I'd always assumed that they were a sonic device, but with that explanation, it would seem pointless.