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it will create a very strong resonance in the single secondary tube. The shallow secondary counter cone indicates a tuning over a rather small rpm range.
I would assume that the secondary resonance is tuned to sit within the power band defined by the primaries of the 4-1 system.

So in the end it could just amplify the low pressure amplitude at the 4-1 collector.
 

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Arouse the DAMPFHAMMER!
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So I was at Road America over the weekend and ran across this very interesting exhaust design. I would think the scavenging effect would be greatly increased. Thoughts?
Thanks for sharing your observations at Road America, looks very interesting :). My thoughts would be following:
  • engine seems to be a Toyota 4A-GE, which has the Genes of the Ford Cosworth BDA engine (belt drive A-type). Not much of Toyota's engines have a belt drive beside the BDA successor for mass market 4A-GE and some V-engines. According the exhaust pipe size of around 50 mm OD, I assume a bigger stroke or bore as the stock 81x77 concept. Normally 82.5 mm bore and 82 mm stroke are the upper limits, with the 7A block the block height increase to 205 mm, where almost 86 mm strokes cranks are available, so at max we talk about 1828 ccm displacement at max.
  • 4-1 header should have a optimal length for around 12,000 rpm and roughly 6000 rpm, which would speak for a 82,5x77 engine, but far not optimal for the application. I would have done a different header setup for an optimal scavenging from this part of the exhaust system
  • expansion chamber after the header, which is typically used on 2-stroke engines, has a tuned 1st order resonance of roughly 8200 rpm to support the scavenging by an under-pressure wave running back to the exhaust valve at this moment. When the main wave reaches the end of the expansion chamber very efficient reflection happens, just because of the design of it, which is reflected as over-pressure wave running up the exhaust, which will counteract the next exhaust stroke of the next cylinder and a wider range of engine speeds. I would need to extend my actual calculation model to extract the engine speed range where this a counter acting mechnism.
My verdict:
This exhaust setup is in many kind not what I would do, it is too peaky regarding usable torque, also without knowing the engine speed range and the IM design of it. Even if it matches the rev range from 8,000-12,000 rpm and the IM set a resonance at 10,000 rpm, that thingy is hard to bring into the working range as torque will be very peaky, especially if cams are accordingly and have a higher duration.
 

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It seems this is a 97 Bennetton car from their group 7 historic/modern formula.


Group 7: Historic/Modern Sports Racers. Classic Can Am, Center-seat Can Am, FIA Championship of Makes, 2.0L Sports Cars, Sports 2000. Examples: GT40, McLaren, Lola, Mirage, Porsche, Chevron, March, Swift, Tiga, Alfa Romeo, Ferrari, etc.




This likely makes this one a Ralt RT-41 P1 Toyota.
It has a 1600cc engine.

from wikipedia: "Originally equipped for Pro Atlantic racing with a highly tuned variant of the Toyota 4A-GE twin cam engine displacing 1.6 litres and developing approximately 250 bhp"

potential engine specs:
 

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Arouse the DAMPFHAMMER!
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variant of the Toyota 4A-GE twin cam engine displacing 1.6 litres and developing approximately 250 bhp"
It is definitely a 4A-GE engine. If 81x77 per class rules then I would assume the revving range is like I assumed from maybe 7000-11000 rpm. The 12000 rpm seems to me to high even for that very dynamic flat tappet system the BDA basis and the successor at Toyota has. So I assume the 1st order harmonic of the 4-1 system may be not reached.
 

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Arouse the DAMPFHAMMER!
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nice little engine revving 10k
Makes hungry for my DAMPFHAMMER HD, which will rev up to 11,000 rpm. At 02:33 you see the exhaust system, which is nicely bended. Seems to be also a 4-1 system, otherwise the primary runners would be way too long. That engine revvs nicely and continousely into the redline engine speed. Seems to be a healthy setup, except the intake air routing, which is completely missed.
 

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Arouse the DAMPFHAMMER!
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Dan Webster's 84mm stroke K20 Elise build is also not far from competition.
He does a 87x84 build? What would be the specification of the performance?
 

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Arouse the DAMPFHAMMER!
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Arouse the DAMPFHAMMER!
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Thanks for the responses, as usual the knowledge base here is off the charts.
To prove it I put it into my 1D-engine simulation and optimized an expansion chamber, put in on my header setup and on a similar setup the 4A-GE engine had. The result was quite astonishing, I was really surprised on one hand, on the other hand it proved my assumptions.

I did have a few other shots, no sense in keeping them to myself.
That Jorgensen Eagle rises my attention most, #48. It has a V8 with an very interesting ITB and induction system. Unfortunately can't see details.
 

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So I was at Road America over the weekend and ran across this very interesting exhaust design. I would think the scavenging effect would be greatly increased. Thoughts?
View attachment 109012
First of all, the exhaust pipe, which is a component used for the exhaust gas of the car. Then it must be resistant to high temperature, because the temperature of the exhaust gas emitted by the car is also very high in summer. At this time, if you choose those materials that are not resistant to high temperature, the exhaust pipe of the car will soften. At the same time, it will cause exhaust blockage, or even the phenomenon of poor exhaust, which is very dangerous for cars driving at high speeds.
 

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Arouse the DAMPFHAMMER!
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At this time, if you choose those materials that are not resistant to high temperature, the exhaust pipe of the car will soften. At the same time, it will cause exhaust blockage, or even the phenomenon of poor exhaust, which is very dangerous for cars driving at high speeds.
Are you a post bot, talking about general aspects of a few signal words you found? Here it is all about the question if scavenging would be increased by the chosen design. May you can explain the correlation of material and scavenging efficiency?
 
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