Well here we go again with me disagreeing and thinking in a completely differnt tangent to you Nitro.
What you have shown with the 4 stroke plot is simply what has been documented in many SAE papers describing what is needed , and comparing TFX data to simulation data to prove it.
Perfect example is SAE 2001 01 1797/4218.
This showed real time data against Optimum Power Technolgy's 4 stroke sim package ( I can use that as its free to Uni engineering depts )
Testing a straight pipe Vs a pipe/diffuser combination.
4Ts exhausts are simpler in that there are two effects that can contribute to power , pulling as wide and as deep a depression around TDC overlap as possible , and secondly a strengthening leftward
depression during the EVO period to reduce exhaust stroke pumping losses.
Achieving both together can accentuate peak power , spreading the two effects out favours powerband ( torque ) width.
Saying that achieving that plot could not be done just using a sim package is narrow minded rubbish - again it comes back to interpreting the data , and intellectual accuity in coming up with innovative
solutions to generate the desired end result.
Its easy to see on that plot that achieving even greater depression , sooner , between - 150 and -30 would reduce pumping losses during EVO. I dont need real data to see that trend at all.
The result certainly isnt limited by the sims ability to represent vey accurately the real time data - the big differnce being the time and work involved is exponentially less the harder the task at hand is.
Sadly for 4T tuning the exhaust plays second fiddle big time to the gains achievable with inlet tuning , the complete reverse of a 2T.
Variable length Exhaust = big 2T power , variable length Inlet = big 4T power.
EDIT - I could not resist adding a reply to this quote " I know we aren't here to talk 4 strokes, but for reference sake, this is basically what an exhaust trace looks using a typical exhaust header design (on a 4 stroke)."
That pressure trace result is NOT from a typical exhaust header , its a completely wrong example , there is virtually no help with exhaust stroke pumping losses , and there is virtually no depression around TDC overlap
ie that pipe setup is NOT tuned correctly to the chosen rpm.
The super secret setup IS tuned correctly so will obviously produce superior pressure trace shape and power as a result.
Ive got a thing thats unique and new.To prove it I'll have the last laugh on you.Cause instead of one head I got two.And you know two heads are better than one.
Bookmarks