What pressure is there in the exhaust manifold? Theres gonna be 2000psi in the cylinder on the power stroke? Maybe a tenth of that when the exhaust valve opens? Thats still 200 psi. And weve seen gases blowing past a tiny hole in a faulty head/manifold gasket so isnt that believable? So 200psi is about 12 bar. As the exhaust gases move into a long and widening system the pressures will drop but it`s still gonna be “substantial” enough.
Above is just “back of a ■■■ packet” stuff except for lifting the 2000psi from here: fuel trials on a 14ltre ■■■■■■■■ Peak pressure is about -ish- 14Megapascals or 2000 psi.
pdfs.semanticscholar.org/203f/b … 6cf8fc.pdf
Table on page 19.
I am of course open to correction on any of that!