VFII V8 exhaust specs - PipeMax

[Not_An_Abba_Fan]

When pressure wave tuning, the collector plays a far more important role than the entry angle into the cats. Merge collectors are the best at pressure wave tuning over a longer RPM band, otherwise you will be restricted to a very narrow tuning band with traditional collectors with the only tuning being done by size and length of collector. This would be where the entry into the cat makes a difference, not so much the angle, but the distance from the end of the header pipes to the start of the cat, this is effectively the collector that the engine "sees". My opinion is the use of a merge collector, this negates the need to get the "collector" size perfect. Temperature will affect wave velocity as well, the hotter gas the fast it will travel, exhaust gas can drop by as much as 150 deg C in the length of the primary pipe so ideally, if you want to keep velocity constant, you have to taper the entire primary pipe, but, and it's a big but, (think Nikki Minaj), engine load will vary the temperature as well, so what works at 2500rpm under heavy acceleration will not work as effectively at 3500rpm with light acceleration. Variables, always variables. Optimum exhaust tuning on a street car? When you crack that walnut you will be a very rich man indeed. Since it's never been done in the history of internal combustion engines.

 

[monstar]

Thanks, yeah EGT is part of the equation according to fuel composition, lambda, combustion phasing and load.
Thing for me is not so much power at all rather how little fuel to get by smoothly 90% of the time at extremely low power, like 20-30 rwkw, then transition smoothly and quickly to long solid torque plateau without fuss, or huge waste of energy (fuel, friction, thermal).

 

[SnowDoggyDogg]

With heat being such a factor - where or how does header material composition (mild, stainless, ceramic coated, inconel, etc.) factor into these equations?

 

[monstar]

With heat being such a factor - where or how does header material composition (mild, stainless, ceramic coated, inconel, etc.) factor into these equations?

There is good information on materials (scroll down here) and discussion about EGT over distance (wade through here).
TL;DR I don't consider titanium or carbon fibre materials or a need to factor many of the externals mentioned in the tech notes to modify standard pipemax results, I assume thermally coated mild steel as an adequate practical reference material for pipe walls.
The impact of stainless for example is near immeasurable over the distance versus the impact of fuel composition, combustion phasing and EGT itself. i.e. EGT of ethanol at end of 4 second 600 RPM/Sec Dyno accel. test is hugely different (-100ºC) to using 91 unleaded under exact same conditions, whereas thermally coated sections retain heat longer, and both these factor into practical equations.

 

[Not_An_Abba_Fan]

Header material makes very little difference. The best way to ensure maximum flow is to get the pipes hot and keep them hot, the material they are made from matters not.

 

[426Cuda]

Just wrap them pipes in asbestos lagging!