Exhaust Performance Question

[Kendo11]

Lots of rubbish spoken and written about N/A 4 stroke exhausts, here's some decent info from Jack Kane. I have the original but it's copyright, so I can't scan it.

 

 

http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm

 

 

https://motordyneengineering.com/exhaust-backpressure-and-scavenging/

 

Thanks Chris, some excellent information in there.

 

Not that one this one-

 

https://www.youtube.com/watch?v=bXQ-cXeri1Y

 

this is the follow up, more applicable to your power level. go against alot of what you read on forums. and im sure every engine is different but food for thought

 

Definitely food for thought, thanks mate.

 

The whole first doc relates to manifold design, bar the 6,000bhp funny car section saying they don't run a collector (where the individual manifold pipes meet, if you didn't know) because it would restrict the exhaust gas flow (this isn't applicable to any N/A engine below something like 1,000bhp, i.e. v8 f1 cars still had collectors at 700+bhp)

 

The second link is again talking a lot about manifolds to begin with, with some data about trying different diameters post the collector, but is also discussing 350z exhausts which are usually twin pipes and I didn't see that it specifies that or not, so I wouldn't take the diameters as a direct comparison.

 

The video Ripper Fear put up about mufflers is good, it compares two 2.5" pipe directly to two 3" pipe on a 600bhp V8 engine (300bhp per bank/pipe) with literally no change in bhp - that is the closest piece of info relating to your original question between the two exhausts.

 

The muffler comparison from the video shouldn't apply to your two exhausts, my old Powerflow was a perforated tube design muffler so I would imagine yours is too, the Motoria is also going to be this sort of muffler too. (The cheap muffler from the video, if it wasn't clear, has a thick 'brick' usually of fibrous material in the box blocking the exhaust gases, seriously restricting the exhaust gas flow and reducing performance, this is not the same as a 'packed' muffler where there is a perforated tube between the in and out holes of the box, and again usually the same fibrous material around the perf tube)

 

Good summary, second document was maybe more relevant to the puzzle.

 

More research required, even if it's just to answer the question now!