20 replies to this topic

[FordFan]

Anyone care to explain to me what Peugeot's variable trumpets are all about. This may have been discussed before on this BB. I don't remember.

[Art]

Ford Fan.

The variable intake trumpets are a electronic mechanical means of varying the length of the intake trumpets as the throttle is opened. This should widen the power band of the engine. An ideal setup would also vary the length of the exhaust as well as the intake trumpets.

Art

[Ray Bell]

There, a helpful post.
The introduction of these has been forestalled by the retirement of Mercedes Benz from racing in 1955. I read in 'The Design and Behaviour of the Racing Car' (Moss & Pomeroy) that the 1956 W196 would have sported this development... and it would have quickly spread, no doubt - or been canned by all if it wasn't a winner. Then again, it could very well have come, gone and returned again as a fad thing, as some things do, like 4-valves per cyl have since 1912.

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Life and love are mixed with pain...

[desmo]

Intake harmonics can be used for a mild supercharging effect by changing the volume of the column of air in the intake port and trumpet. The effect is such that a given rpm corresponds to a given length or volume of the intake system. By matching intake volume to rpm and perhaps other variables as well a small gain in useful power can be achieved. A similar effect, as Art pointed out, may be possible to some extent on the exhaust side as well but that (for some arcane reason) is illegal in F1.

[This message has been edited by desmo (edited 04-29-2000).]

[Ray Bell]

There's an inherent fragility with exhaust systems without compounding the problem by adding moving bits.. exhaust pipes falling off and getting hit by following drivers or flying into the crowd (and being hard or dangerous to pick up without asbestos gloves to clear the circuit) might well be the FIA's reason.
Or it might not?

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Life and love are mixed with pain...

[desmo]

Ray, I'd like to think that modern F1 engineers are capable of producing a variable length/volume exhaust system that isn't going to leave a trail of debris in it's wake. If sliding seals are beyond the skill level of the engineers, I think a system that utilizes Helmholtz resonator(s) controlled by simple butterfly or slide valves might provide some benefit. If the reason you cited is indeed the rationale for the ban, it seems like awfully weak justification.

[This message has been edited by desmo (edited 04-29-2000).]

[Yelnats]

Two Strokes have made much greater use of resonance extraction on the exhaust side than 4 strokes though this has been a case of "necessity is the Mother of Invention". Considering the lack of positive displacement two strokes do an amazing job of clearing the exhaust from the combustion chamber.

I feel resonance induction/extraction is the next big are where power and tourque gains can be made. For F1 to bann developments in this are is short sighted and another step toward the day is when it will be another "Spec" series.

[desmo]

Obviously large volume expansion chamber type exhaust systems will never be practical in F1 for packaging if no other reason. Two-strokes can exceed 100% volumetric efficiency, albeit in a narrow rev range, using exhaust pulses reflected off the convergant cone segment of the expansion chamber to "stuff" intake charge lost through the exhaust ports back into the cylinders.

Someone is going to figure out how to utilize this "wasted" exhaust energy in a four stroke someday. I guess it likely won't be in F1 due to the unreasonably restrictive nature of the technical regulations. Pity, that.

[malbeare]

Originally posted by desmo:


Someone is going to figure out how to utilize this "wasted" exhaust energy in a four stroke someday. I guess it likely won't be in F1 due to the unreasonably restrictive nature of the technical regulations. Pity, that.[/B]

The Beare head design makes this very much feasable, as it is very similar to a two stroke in port area and design. http://www.sixstroke.com

[desmo]

Mal,

A couple of things that might make it difficult to utilise exhaust resonances to improve volumetric efficiency on your design: Firstly due to the fact that power strokes occur only every other crankshaft revolution means that to time the reflected pulses back to exhaust port in a four stroke, obviously the exhaust system will have to be approximately twice as long as it would in a two stroke, all else being more or less equal. Another thing is that I would imagine that the disc valve between the exhaust port and the pipe could complicate matters. The effective volume in the exhaust system is effectively changed as the disc valve opens and closes. Also if the valve isn't timed correctly to optimise it to take advantage of exhaust pulses, they would meet a barrier upon reaching the disc valve nullifying any potential benefit. I am not saying it wouldn't work. Frankly I don't understand your design well enough to make an informed guess. I'd like to hear your thoughts on the matter.

Regards,
Kurt

[Ray Bell]

I was talking to a guy the other week who is having discussions with Ford here and in the US about a device he has concocted to fit in the exhaust system. He has tried in on some open wheelers, claiming a 5% power improvement, while a courier van running on LPG (propane) on an identical run every day has suffered a reduction in fuel consumption of about 40%.
I've got to find out more about it, but he naturally isn't telling much about how it works. From a picture of it, it just looks like a fluted muffler... but who knows what's inside?
So perhaps there is some prospect of some gains there?

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Life and love are mixed with pain...

[desmo]

Ray,

40%? Sounds like the 200 mpg ultrasonic carb (mythological). Having said my skeptical bit, if someone had made the legitimate claims of what an expansion chamber is capable of in two strokes before I'd heard of it, I'd probably have dismissed that as well and been wrong. I sorely hope it's true. OPEC and the oil multinationals have us over a barrel (of crude?) at the moment and any advance that led to a significant reduction on the demand side would be all to the good. I wish the regulatory envirnment in F1 was such that the very bright people in the sport could bring their minds to bear on this sort of thing.

[malbeare]

Desmo,

Here is the theory
All the ports are fully open at TDC at the end of the exhaust stroke. Prolonged Exhaust extraction is used to fill the combustion chamber and the upper piston vollume, with intake mixture and spill some into the first few inches of the exhaust pipe. A late closing of the disk achieves this.While some of the intake stroke is occuring the exhaust pulse travels down the pipe and meets the reverse cone, travels back again and meets an open port with the upper piston half closing it, very similar to the normal two stroke. The disk has opened again. This means that the disk only closes the port during a narrow portion of the intake stroke.
I have experimented with this but it is still early days yet. The engine ran hapily and I was surprised at how low revs it would still run. At higher revs it sounded more like a two stroke than before more popping
It was loosing more of the intake out the exhaust than it was stuffing back in I guess
Apropriate exhaust pipe length is yet to be determined.
Regards
Mal http://www.sixstroke.com

[This message has been edited by malbeare (edited 04-30-2000).]

[Ray Bell]

It's now a few weeks since I spoke to the man. He talked of something too technical for me to understand... diffusing the wave or something like that (don't quote me, I may have it back to front)... I'll try to talk to him tomorrow and find out more.
He's also involved in discussions with CAMS about being able to use it in race cars... silly man! How frustrated can he become?
He has tried it in V8 touring cars at Lakeside and one was able to pass the other up the straight (just, he said) which it had not previously been able to do.

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Life and love are mixed with pain...

[PDA]

Desmo - one might think that F1 designers were capable of designing and making robust variable length exhaust systems, but take e.g. Jaguar at Imola, where JH lost out in qualifying (yet again) with a cracked exhaust (and that was a fixed length system).

[Ray Bell]

That's been the situation since time immemorial... hence I would see FIA reluctance to allow variable systems.
Regarding the device my acquaintance has designed, he tells me that some people from GM in Detroit are visiting him this afternoon to look over some of his stats.
He says it modifies the wave, and somehow excludes atmospheric pressure from the equation, talking of developing a kinetic wave... Beyond me, but interesting.

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Life and love are mixed with pain...

[desmo]

I cannot recall how many times over the years I've seen race cars retired or slowed by broken exhaust systems. Hundreds, at least. I've never or known anyone who has ever had the exhaust manifold or header on their road car or motorcycle fail other than through rust. Kart pipes used to fail regularly until we learned how to spring mount them to allow them to move around a little. I'm sure a race engineer would call the stock exhaust system on a road car or bike ridiculously overengineered. They might be wrong.

[desmo]

Ray,

Keep us abreast, if you can, on this exhaust "device" if you can call it that. I'd love to hear more.

[desmo]

I found a web site that claims Ferrari were using a variable-length exhaust system on a V-12 F1 engine prior to their being banned. I could not substantiate this however. Apparently the Ferrari 360 Modena uses a type of variable exhaust to circumvent EU noise regs as well.

[Ray Bell]

Shall do.... by the way, the Falcon 250 6-cyl engine is one that I'm fairly sure regularly breaks its cast iron exhaust manifold, at least here in Australia. Heat variations, no doubt. And I think the Valiants have a similar problem, not sure, but that would probably be the 245 & 265 'hemi' engines.
One of the funniest exhausts I ever saw was on the Datsun 1000 Sports Sedan built by Col Wear for David Seldon to drive. It had the 1850cc Waggott TC4V engine (Ford-based like the FVA, but a local design that was made in small numbers and eclipsed the power of the FVA and came also in a fully-manufactured 2-litre version for Tasman racing).
Col couldn't get everything he needed to rush it to its first outing at Oran Park, so he shortcut the exhaust, dumping the extractors into some household downpipe, the rectangular section 24g galvanised tin type of thing you get out of your gutters... the sonic vibrations killed it in a couple of laps!

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Life and love are mixed with pain...

[Nuvolari]

Ferrari were using variable length exhaust primaries till the early 90's. The technology got banned because it was too damned effective.... There's an interesting SAE paper on the Lamborghini/Chrysler F1 engine, and how they used it. I'll try to dig out the paper, and post the reference.