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Originally Posted by chenry
with valves open - I'm curious if you (Dinan) can share how much exhaust flow (in terms of percentage - guesstimate please) is bypassing the muffler
Love what you've done here seems like stock at times passing through the muffler and almost straight-piped muffler bypass at full song
Thanks - beautiful work / granted really just for sound - but that sound may just may be worth it to many
ps- our first modded bmw was back in 1987 when we had a dinan chip soldered into the ecu of our 1985 528e - we met Steve at the shop :-)
ps - yes i think we gained 3hp - bahaha - but it was all we had :-) and were thankful for Dinan
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Rough guess when valves open are open -- I don't believe more then 10% of the gasses go through the can. This formula (open valves essentially being straight pipe, closed valves going through the muffler for a deeper note but similar volume as stock) we have used to great success over a few of our more popular recent exhausts (F90 M5, F8x M3/M4, M2/M2C) so its a proven formula that most seem to be on board with. Given we change the internals of the cans for each of those systems to combat specific drone tendencies or to get our preferred deeper note but the general philosophy is the same. The big difference with the M340i is the addition of the second valve so it truly behaves like a "real" M exhaust typically would.
For power--- Additional power is technically there at high RPM's but I think everyone realizes at this point that an exhaust is a sound only modification as anything you get from an exhaust is immaterial in the grand scheme of things. Its a grat stat line filler though. =)
The old days of scraping an additional 5HP out of $3000 of hardware modifications were a different era. You had to really work for everything and the process was almost the more enjoyable part then the result. Those only familiar with the turbo era don't appreciate a lot of that which is a shame. Fancy computers and instant gratification. <old man voice> Back in my day if we wanted more power we had to drink some extra strong black coffee and run faster through the floor boards, Flinstones style. I digress... lol