Air Flow / CFM's

[FMP]

ttt

[powerabout]

I would hate to see what the inside of that pipe looks like ....
Looking at the turn twords the center about mid clamp the pipe makes a big change in cross section area , goes back / forward / down all in one expanding sweep , then kinks back and down increasing to at least double the area at exit .
I know it's a prototype and they cleaned up the production model , but I can't help but wonder why they would go against the grain when it comes to drastic size and angle changes . It's still a practice they haven't let go of if you look at the 3.0L exhaust tract from port to exit ....

I do see steps taken to equalize the header ( primary ) pipe length . That's something they lost on current V-6's .
How did it come to be that OMC went with a 90* V with lots of room between the cylinder banks and a well thought out primary pipe arrangement , while Mercury seemed to go with making a tighter package forgoing having room to design a proper exhaust conduit , and a crankshaft that has natural balance issues ...?

The open trunk is better at high revs
Look at production 3cyl omc versus the race engines
The 31m looks like half a 300 drag merc exhaust
Thinking about that the 31m came first with milled down angle..

[Chaz]

Power , ya know , it was raining 3 cylinder powerheads the other day . Yup , both consumer and race models . I didn't get a chance to do a comparison between the two , so until it rain's again , I'll just have to take your word on that .

One question though , Is your fabrication and welding skills up to that of the "open trunk" posted above ...

[powerabout]

Looks like it done with a stick welder so yer thats about the limit of my skills.
I have a photo of 31m block so i will post tonight to see if my memory is as good as reality.

[powerabout]

here ya go OMC 80's technology

[powerabout]

KIVA software on an e-tec
https://www.youtube.com/watch?v=fSko...ature=youtu.be

[FMP]

KIVA software on an e-tec
https://www.youtube.com/watch?v=fSko...ature=youtu.be

10-12s , Great animation, you can see the leaving blowdown pulse formation through the crank degrees and pairing cylinders return about 35-20* prior to port close. Degree counter on the bottom of screen