We've been working on sumtin... manifold

[Mazdazilla6]

Originally Posted by Tomas Dude you are arguing against something that has been well known over many years. Your prof is wrong. Reversion is more likely in short tube headers compared to long tube headers. You need to look at tube header length from the perspective of a pressure vessel. The bigger the vessel the more volume it will be able to hold at the same pressure as a smaller vessel, or alternatively, the pressure in the vessel will be lower when the same volume of air is pumped into a bigger vessel than a smaller vessel. Most high RPM race engines, with some exceptions like Mercedes's PU106B power plant, have long tube headers. And if they don't, like in Mercedes's case, it is a compromise that is made due to space or other constrains. If you can post links to some of these high RPM short tube header engines you speak of I'd be interested in reading about them. Just search and look at all the NA and Turbo Formula 1 engines over the years (with the afor mentioned exception).

Don't know why I never saw this. I don't want to drag this out as this isn't the thread for it but, as for the engines you've listed, those are short header engines (that BMW is a bit iffy tho). Look at how close the collector is to the head. Those collectors are essentially the same thing as runners converging into a turbo. The best reason I can think of as to why they aren't even shorter is that they are trying to keep length consistent for pulse tuning.

You should not view an exhaust system as a pressure vessel because the biggest difference between them is that an exhaust has flow and a pressure vessel does not. It's for this same reason that engines being tested on dynos have more than one backpressure sensor, because backpressure is different in different areas (like the banks). Backpressure is also heavily reliant on engine displacement. X diameter tube will experience reversion sooner at Y RPM on a 500CI engine than it would on a 300CI engine at Y RPM.

If you'd like to discuss this more shoot me a PM. I'd rather not clutter up this thread and I love discussing engines and engine theory.