where's the tune in tuner

[jay1]

and correct me if im wrong again .. but doesent high port heights cause poor bottom end .. not a tuned exhaust...

[Mark75H]

and correct me if im wrong again .. but doesent high port heights cause poor bottom end .. not a tuned exhaust...

Because you started talking about expansion chambers, the higher porting is part of the expansion chamber program ... just adding a pipe will not significantly add power unless the ports are already up.

Your ideas alternate wildly between a single change and dramatic results that are part of a more involved program; the two won't happen together.

In all out unrestricted outboard racing expansion chambers have been successfully used since a couple years after Kaaden started putting them on bikes (1960 on the Swedish Crescent 500cc V-4 and many others since). But on the slightly restricted gas/modified classes where you can do anything to the exhaust and intake but can't change porting ... a well prepared stock motor without an expansion chamber can run competitively with motors with expansion chambers.

Today, 500cc full racing outboard motors are pulling close to 200 hp, 400cc mod motors with expansion chambers are still only getting into the 40 hp range with the same guys tuning and building pipes for both.

[oldskier]

Another point regarding the 2 stroke tuning available to outboards that is limited by previously mentioned difference between bikes, snowmobiles and boats, (I.E. gearing) is that exhaust tuning only seems to move the power around in the RPM ranges. A bike with a long stinger made lots of power above 8 grand, but to get it moving in 1st gear might take 5 grand. A boat doesn't have that luxury.

I remember seeing the little hydros race in Charlotte Harbor back in the 60's and they had those long stingers. They would actually lift the stern out of the water to start the motor, then rev 'em and drop 'em in the water.

[T-REX]

...... even if it was the biggest dog outta the hole.. 100 hp would get that boat on plane with ease.. ill bet less than that...

Sorry, juss couldn't stand it no mo...

A 300 HP outboard prolly don't make 10HP under 1000rpm...U add a tune'd pipe, and it will even have more trouble gitt'in to that magik "on the pipe" spot...

Several yeers ago Lentskow had a set ov tuned pipes at jasper...The bote ran purdy good, but when The mota finally got "On the pipe", the other boat wuz already past the finish bouy.....

U want about the same performance gain az modify'in tha exhaust on a v-6, PAINT YA POWERHED ORANGE!!

[1BadAction]

Several yeers ago Lentskow had a set ov tuned pipes at jasper...The bote ran purdy good, but when The mota finally got "On the pipe", the other boat wuz already past the finish bouy.....

there was one with 6 pipes sticking 6' straight out the back in the early days of the 2.5 at the florida barge canal... i seem to remember it working exactly as you describe. sounded really cool tho.

all I know is, the more I learn about 2 strokes, the more I realize modifying them is better left to guys who know wtf they are doing. LOL.

[jphii]

there was one with 6 pipes sticking 6' straight out the back in the early days of the 2.5 at the florida barge canal... i seem to remember it working exactly as you describe. sounded really cool tho.

all I know is, the more I learn about 2 strokes, the more I realize modifying them is better left to guys who know wtf they are doing. LOL.

Not true grasshopper. Much more fun to hear one say "you can't do that" and then show them you can.

And on an OMC there is plenty of room for tuner mods to make much more power. The problem is the things that you can do won't work on a production motor for the masses. I don't know about them lil sissy Merc motos, but I'm with DaveS on this one.

I like the tunna, you talk to it nice, drill 3 holes in a special place and it just rips the boat outa the water.

[rock]

Several yeers ago Lentskow had a set ov tuned pipes at jasper...

Lentzkow Engineering built a set of expansion chambers for a V6 Merc and said it cost a bunch of money and had some effect but was probably not worth the investment. Gotta figure Merc has a few bucks invested building and designing these things and more than likely we are getting the best compromise possible. I think if someone could invent a variable length pipe that could change with throttle position, like some bikes, maybe you would have something. Keep in mind, I am a cabinet maker, not an engine designer.
Rock

[jphii]

That's what the little hydros like the 500cc run, sliders. Pretty neat system.

[Mark75H]

And PWC's vary the timing effect by changing the sound wave speed with direct water cooling

[jphii]

And PWC's vary the timing effect by changing the sound wave speed with direct water cooling

So do some outboards

[rock]

ROFLMAO jphii I have seen your avatar many times but I just really looked at it just now. Very good.
Rock

[jay1]

ok .. you guys are slowly killing any ideas ive had on this subject..i just thought there could be a huge hp gain by posibly extending the chest cover or maybe even angeling it to be thicker at the bottom and bolted to a extended adapter weather or not ya went back into the mid or exited it there i dont know.. was kinda hoping for some input as if it was a good start to a idea... believe me ill never bring it up again.....how come only the omc guys make the cool stuff??? yea i said it....and come to think of it i like orenge "T"...

[Mark75H]

What "cool stuff" are you referring to?

[Dave S]

We been keeping that one from ya SAM.

[DoktorC]

And PWC's vary the timing effect by changing the sound wave speed with direct water cooling

Funny you mention PWC's...They also us "power valves" to control port height. My GPR (1200cc) makes 155hp with a single exhaust or with tripple tuned pipes it makes 200+..then porting. I have also thought the same as Jay. There's alot more power left on the table in these (outboard) engines...it just may not be practicle extracting it.

It's interesting to note that my pwc has no gears and hole shots like a motha' even with 2 200+lb guys on it (that's about 1300lbs total)...now it only runs 73mph..but the tripple pipe guys are in the 90's now. I'd bet a tuned exhaust and exhaust valves would open up a new world of power....didn't someone mention BRP is bringing RAVE (their exhaust vavle system) to outboards??