Outboard Exhaust Tuning - Who Did It Best?

[Chaz]

IF we were to put a gasket on that Tunna.....could we mix some........looks

If it didn't work, I was gonna weld a floor in it and send it to ya .. so you can use it as as a ...... shot glass ..

[Chaz]

For the rest of us that didn't write the "laws of nature" but have to abide by them if we choose to accomplish anything in the realm of exhaust, be it 2 stroke or 4, the same rules apply.
Like the rest in this thread, we'll use my pictures .. taken in my shop ...
I think where some continue to be confused is in the word "returning".
A returning negative wave is nothing more than "the back catching up to the front".
Put a diverging ( gets bigger as it goes) cone on the back and you will get a stronger scavaging ( pulling ) signal.
This is true no matter if it's one pipe or ten tied together. Up to this point, there is no magic that will force this negative into a positive. The exhaust pulse will always be pulled to the path of least resistance.
The magic wand one must employ to send a positive (pressure) wave back up the pipe with enough force to either stop or turn around the negative wave is a converging (getting smaller) cone to "reflect" the pulse back to where it came from.
Very simple concept .. for most



If I were to run these's pipe ending as three singles, there would be a negative wave from each.
Running them through the collector would get them pulling the next one along (scavaging).



Add a bit of straight, and it will empty itself and the next in line a bit harder and for a longer duration.



Add an "open ended" meg ... and it's more of the same.



Add a reverse cone on the end of the meg , and for the first time .. you will have a positive returning wave ...

[FMP]

No, after the negative scavenging wave has played out, the rebound from

and

aggressive negative wave.

That makes absolutely no sense .. not even to you !

There is only one thing you have been correct on all along ....>

I build exhaust systems for two strokes and four strokes out of metal every day, they get flogged on the dyno and then taken out and have the **** out of em ..

Now let's see if I'm right ... you sit and dream
I notice you don't have too much to say about the magic U turn ?
When you .. no that won't happen. The rest of us notice how Mercs and OMC, exhausts, cylinder blocks, reed block stacking, etc etc all differ in appearance ... yet both companies offer 2 horse kickers to 300 horse motors

I think we're all caught up now ...

A little theme song, just for you .. >

If any readers would like to read more into this
Mr R Lanpheer of Mercury Marine has a paper on it with respect to the inline 6
https://patents.google.com/patent/US3808807A/en

[Chaz]

You still got nothin of your own to show ... ???

Ohh well ... back to the "American" patent office .. ehh ???

See what that patent did .. it stopped OMC and West Bend from building an inline 6 .. Nothing more ...

If it worked so good, then why did they have to do this to make any power .. ???

Chaz = thinkin, there's three more questions you'll avoid ..

[FMP]

The ant trail if anyone is interested
https://patents.google.com/patent/US...rd+A.+Lanpheer

[Dave S]

125 BP EVERY ON SHOULD HAVE ONE.....they make good door stops.......and ya can dry ya rags on the stacks.....

[powerabout]

If it worked so good, then why did they have to do this to make any power .. ???

Chaz = thinkin, there's three more questions you'll avoid ..

The exhaust design changes with rpm
Production engines need some water skiing torque at low revs
Check out the OMC F1v8 where they had a free hand....

[Chaz]

125 BP EVERY ON SHOULD HAVE ONE.....they make good door stops.......and ya can dry ya rags on the stacks.....

But, but, but ... what about "the invention" ...

The exhaust design changes with rpm
Production engines need some water skiing torque at low revs
Check out the OMC F1v8 where they had a free hand....

Exhaust design changed more .... over periods of time ...
Properly sized, stack exhaust will make plenty of torque, as well as sweep the top
Go east across the (old) Palm City Bridge into Stuart, First place you come to is Monty Racing, then the OMC test center, and Lars Strom lives here too. How much more OMC V-8 history does my little town need ...

[cali kid]

But, but, but ... what about "the invention" ...



[/FONT][/COLOR][/LEFT] Exhaust design changed more .... over periods of time ...
Properly sized, stack exhaust will make plenty of torque, as well as sweep the top
Go east across the (old) Palm City Bridge into Stuart, First place you come to is Monty Racing, then the OMC test center, and Lars Strom lives here too. How much more OMC V-8 history does my little town need ...

A set of Expansion chambers would certainly make more power and range throughout. Not practical due to the size it would have to be. We will have to do with the "stack exhaust" as Merc has made to work well enough. I don't know if it's Chaz's knowledge or his sense of humor that keeps me looking for his posts. But I'm still cracking up.

[powerabout]

expansion chambers have a broad power range, first I have heard of that

[cali kid]

expansion chambers have a broad power range, first I have heard of that

I race a KTM 300 XC two stroke. The FMF Fatty expansion chamber on it pulls from idle to over 8000 RPM, with a very flat torque curve. Other factors come into play but the pipe has a big effect.

[powerabout]

I race a KTM 300 XC two stroke. The FMF Fatty expansion chamber on it pulls from idle to over 8000 RPM, with a very flat torque curve. Other factors come into play but the pipe has a big effect.

very cool, on a carby?

[cali kid]

very cool, on a carby?

Yes. I have not tried the TPI yet, but the carb works so good I can't see spending the money or the extra weight and complication of efi.

[Chaz]

expansion chambers have a broad power range, first I have heard of that

You should get out more often ..

[powerabout]

You should get out more often ..

seems like it
how about 3 cylinders into common expansion chamber like a sled, could almost do that on a 20 or 25" mid?