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Advantages of dual or triple exhaust on a bank of six cylinders?


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#1 V8 Fireworks

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Posted 10 February 2018 - 11:00

As above, just wondering what are the advantages of dual or triple exhausts (.e., a set of  3 or 2 cylinders having their own header which does not merge with the remaining cylinders) on a bank of six cylinders.  I presume the same would apply for a standalone inline six.

 

I can't imagine they would be willingly giving away scavenging performance, so I take it this arrangement performs better in these applications. Is it something to do with the high rpm and small displacement per cylinder of these applications?  

 

Matra, Triple exhaust per bank

maxresdefault.jpg

 

Ferrari, Dual exhaust per bank

9w3ZK9l.jpg


Edited by V8 Fireworks, 10 February 2018 - 11:07.


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#2 MatsNorway

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Posted 10 February 2018 - 11:36

Great question, i have been thinking about that before. Could it be because the pressure difference is higher with bigger periods of time pr. pulse?

 

Combine that with lack of serious flowbenches, too big pipes, lack of knowledge an lack of data simulations and you struggle to do it at higher rpms with multiple pulses. You end up with a finer/smaller tuning window.

 

i state big pipes because the speed of the pulse contains energy, so by maintaining that energy you can use the momentum to draw more exhaust gases out of the other pipes. At least that was what i got from one engine builder that was very focused on the flow over the entire pipe, he would go down in size further downstream to keep the exhaust gases flowing at the same speed.  That part i do not understand.


Edited by MatsNorway, 11 February 2018 - 17:01.


#3 Bloggsworth

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Posted 10 February 2018 - 14:12

In Matra's case, it was because they thought their engines too quiet... Seriously, in over 100 years, I don't think there is any agreement on the benefits of either, as a layman, I would think it about the difference between peak power and the spread of torque/power. BRM won the World Championship with 8 individual stacks - Cause or coincidence?



#4 MatsNorway

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Posted 10 February 2018 - 20:12

In BRMs case it probably was a blown engine or coincidence :lol: :lol:


Edited by MatsNorway, 10 February 2018 - 20:12.


#5 Charlieman

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Posted 11 February 2018 - 14:45

This was a question for which bikers once had an answer -- about twins, threes and fours. And for the V8 1.5 litre F1 cars of the 1960s, there was the question of crankshaft angle and ignition sequence.

 

For a 2018 V6 in F1, packaging of the engine and exhaust system is probably more important than 0.5% max power. 



#6 Charlieman

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Posted 11 February 2018 - 14:59

At least that was what i got from one engine builder that was very focused on the flow over the entire pipe, he would go down in size further downstream to keep a constant flow.  That part i do not understand.

Is it possible that something has been lost in comprehension and translation? Constant flow? Steady flow? Laminar?

 

Owing to heat loss through the walls of a pipe, you might reduce the internal diameter -- in an attempt to maintain energy flow. I'm just trying to apply Bernoulli principles.



#7 MatsNorway

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Posted 11 February 2018 - 17:01

Edited to: keep the exhaust gases flowing at the same speed.



#8 Greg Locock

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Posted 11 February 2018 - 19:02

As the exhaust gas cools the velocity drops, if the pipe area is constant.



#9 MatsNorway

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Posted 11 February 2018 - 19:52

Sure, but why is that a problem? high flow also means more resistance surely. Venting into a big pipe would be more like venting into the free air.



#10 Kelpiecross

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Posted 12 February 2018 - 03:15

In Matra's case, it was because they thought their engines too quiet... Seriously, in over 100 years, I don't think there is any agreement on the benefits of either, as a layman, I would think it about the difference between peak power and the spread of torque/power. BRM won the World Championship with 8 individual stacks - Cause or coincidence?


From memory - I don't think they ran the 8-stack exhaust in many races. Also from memory - the car was said to sound like lions roaring in the distance.

#11 Tim Murray

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Posted 12 February 2018 - 06:02

Yes indeed - BRM used the individual ‘stackpipe’ exhausts only in the early-season non-championship races and the first two championship GPs, but the stackpipes had a habit of breaking and dropping off. From the Belgian GP onward they used a low-level twin tailpipe system.

#12 john winfield

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Posted 12 February 2018 - 11:03

I'm not sure it answers the original question but there's an interesting piece by DSJ in the August 1979 Motor Sport. I used their archive search feature and there are some others over the years too. Here's the 1979 one:

 

https://www.motorspo...ne-trend-design



#13 Fat Boy

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Posted 15 February 2018 - 19:08

Considering the car the OP pictured had very little scientific work done with respect to any aspect, you can almost certainly conclude the exhaust configuration was chosen for aesthetic reasons. This could be visual or aural.



#14 fredeuce

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Posted 17 February 2018 - 23:18

Considering the car the OP pictured had very little scientific work done with respect to any aspect, you can almost certainly conclude the exhaust configuration was chosen for aesthetic reasons. This could be visual or aural.

It did read somewhere that the sound produced by this engine was a goal in the design brief. Little doubt they achieved this.

 



#15 Fat Boy

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Posted 20 February 2018 - 21:38

It did read somewhere that the sound produced by this engine was a goal in the design brief. Little doubt they achieved this.

 

It's a shame this is neglected presently. Who gives a **** if the Matra was fast. Here we are talking about it 50 years later!