where's the tune in tuner

[jay1]

Im New To The Outboard Thing.. Ive Been Trying To Make Power Out Of A Old Bridgeport Carbed...and The Whole Exhaust Thing ....just About Every 2 Stroke Bike Sled Or Quad Benifits From A Tuned Exhaust (expansion Chamber) Why Cant Somone Design A Mid To Do Just That...or Has It Been Done?? Also Has Anyone Ever Done Anything As Far As The Exhaust Plate And Devider..i Seem To Remember Omc V4's Gaining Somthing From The Bubble Back Setup..wouldent That Work On A Merc anyone ever make something like that , would that work??..instead Of Cutting The Chest???? AND AS FAR AS A TUNED OR TUNEABLE EXHAUST. ISENT THIS ACHEVED FROM THE STINGER LENGTH INTO THE OUTGOING SIDE OF THE EXPANTION AND NOT WHERE IT DUMPS IN ...THE WHOLE TUNER THING HAS ME BAFFELED...LITTERLY... THANKS ,,,JASON http://www.motorcycle.com/how-to/how...care-3423.html

[Hot Shot Merc]

I had a old bridgeport on a hydrostream and the tuner bolt nuts rusted and it broke off and fell in to the bottom of the mid and I didnt even know for a long time.It ran the same.They can be moded but only make gains in the high rpm range.Diamond Marine www.diamondmarine.com does a nice job on one and a lot of guys do whats called dry stacking.Ask Jay Smith JSRE.He knows more than I.

[jay1]

http://en.wikipedia.org/wiki/Expansion_chamber

[Mark75H]

Something like this?



or this?

Actually the reason tuned exhaust isn't seen on the V-6's is because it is hidden in the exhaust pulses and firing order. Each cylinder has a complimentary cylinder that slams over charge back into the cylinder much the same way an expansion chamber does. It is a feature of 120° firing 3 cylinder 2 strokes ... and multiples of 3.

Merc did their first exhaust plate/divider in 1949 with their first 4 cylinder and then ignored it until they made the first 100 hp inline 6 outboard for the 1962 model year. Ever since then they have had the internal exhaust pulse tuning on inline 6's and V-6's. One reason outboards can't come out of the factory with precise super tuning is that they will be applied to a very wide range of boats. Sled and bike engines will only be used on vehicles practically identical to the ones the engineers put it on; outboard engineers just aren't as lucky.

The "tuners" under the V-6's do little or nothing for power, so I'm starting to wonder if they are mis-named sound "attenuators"

[jay1]

that first pic "looks" like a genuine effort was put into "tuning" ... the second one seems like another feeble effort to clear the exhaust of any backpressure...

[Mark75H]

the second one seems like another feeble effort to clear the exhaust of any backpressure...

Oh, no ... much more to it than that ... and best of all, it worked. It would have been much easier to just "clear backpressure" than to add all that extra stuff. Power was boosted from around 135 to around 160 with that mess;
again, all based on the 120∘exhaust pulses.

[Mark75H]

All that info on Wikipedia about the expansion chamber and no mention of when, where, who invented them or what kind of vehicle they were first fitted to.
I give credit to Walter Kaaden at the DKW/MZ motorcycle plant in East Germany in the mid/late 1950's. The next application was the Crescent 500cc racing outboard of the early 1960's and then the Suzuki copies of the MZ racing motorcycles

[jay1]

This phenomenon was first discovered in the 1950s by Walter Kaaden, who was working at the East German company MZ. Kaaden understood that there was power in the sound waves coming from the exhaust system, and opened up a whole new field in two-stroke theory and tuning. .. i dont think it says anything about what it was first tested on...seems like alot of lost power when it comes to outboards........ how about the bubble back on a v4 omc ... thats not tuned is it.. it just lessins the restriction doesent it... and their v6 looks a tad larger back there as well,,, so im wondering why cutting the chest works so well ... kinda wonder what spaceing the divider would do on a merc .. whattta ya think..????? like a merc with a bubble back exhaust plate...and if you did do somthing like that... then how far could ya go with it ... maybe bolted down to a longer adapter that would give ya the ability to make the two exhaust ports as large as ya wanted. or even the ability to start the bugal.. by the time ya got to the actual mid the opening could be as large as the big end of a 2.4 bp tuner......this allowing the whole mid to be the expantion area... ..... yes ,,, no.... anyone wanna chime in... anyone done anything like this.....

[1BadAction]

slooooow down, and carefully read the below, one, more, time...

Actually the reason tuned exhaust isn't seen on the V-6's is because it is hidden in the exhaust pulses and firing order. Each cylinder has a complimentary cylinder that slams over charge back into the cylinder much the same way an expansion chamber does. It is a feature of 120° firing 3 cylinder 2 strokes ... and multiples of 3.

[Raceman]

Merc started racing the first V6 as we know it today somewhere in the range of 1973/1974 in prototype form. At the APBA nationals in 1975 in Miami there were several of em. Since that time there's been a little bit of everything tried on em. If extending the size of the exhaust divider was an effective mod it would've been done long before now. When it comes to two stroke exhaust tuning, bigger isn't necessarily better............ as a matter of fact, it's usually the opposite.

The picture that Sam (Mark75H) posted of the Twister on the blue boat is one of my engines. That side exhaust log is essentially a stretch of the exhaust chest with the runners coming way down into it.

As far as the tuners go, as Sam pointed out, most of the tuning goes on in the chest, and it's pretty well over by the time the pulses exit the bottom of the powerhead. Many people worship the exhaust tuner as holy grail, but in fact there's VERY LITTLE difference between the very best and the very worst. Others will state that the tuner that comes on a V6 150 is very long and therefore hurts performance. I always chuckle when I see those comments, thinking about the length of the log on the Twister/Twister 1, which is essentially putting a MUCH LONGER tuner on a powerhead than the production version came with, and also the fact that the T2X production tuner is roughly double (a little more than double actually) the length of the production inline 150 tuner. In any case, again, tuners make very little difference to the average lake boat. For a raceboat looking for every last hundreth of a second, they MAY BE worth playing with a little, but most people who go to the trouble to change em on a lake toy can't read any difference on the speedo.

The first production V6 Merc, sold to the public in 1976 had a very opened exhaust chest and much larger exhaust openings in the bottom of the powerhead. It was 122 cubic inches or 2 liters and remained unchanged for the '77 model year. In 1978 with the introduction of the 2.4 liter/142 cu in production engine that was rated at 200 Horsepower, the internal volume of the exhaust chest was cut down dramatically, and the holes in the bottom of the powerhead were also reduced substantially in size. We usta' cut the chest and bottom of these blocks to closely resemble the previous production 2.0/175's. While the tightening of the chest and exit did in fact enhance the bottom end of the 2.4's (that had been a common complaint on the previous 2 years 2.0 liters) it didn't SIGNIFICANTLY hurt the rest of the powerband, even with the larger displacement of the 2.4 on anything but a light fast boat that was being turned harder than the stock engines upper 5K peak operating range at full throttle.

One more comment: In the 70's the two factories (Merc & OMC) were dead at each other's throat with the factory race teams. Both had a full time staff of engineers pulling out all the stops to find the little things that would give em the advantage over the other. One thing that came from all this was a Merc exhaust on the factory Team boats that has a square box coming straight out the back of the powerhead, through the cowl, quickly making a downward turn and going into the exhaust snout above the gearcase. Apparently they weren't effective because they disappeared from the Team boats after a race or two, although they did make the cover of the Merc High Perf catalogue that year. The point in all this ramble is, 30+ years later you're not going to dream up a significant change in exhaust chest/tuner/exit design that SOMEBODY hasn't tried before. Rather than trying for a miracle it's probably better to try and determine what some of the more successful racers have found to work and use it.

[Dave S]

Race Man.... I think Merc changed from the T1 to T2 log as to save Weight, less stuff on the side of block. The T1 had more distance cly to cly on the log. T2 stacked 2- 3 cly cranks and put the exhaust stacking closer for stronger and better timed pulses. The long tub was just on one set, the other was in the block. Merc learned as they went, and used the long tunna in the L6 115= long and tube shaped. The funny thing is on the 90 L6 they used the old style short 150 tunna. They know what they were doing or......were just getting rid of old tunnas. The 3.4 had no tunna it had balls instead. Merc figgerd how to make more HP Bigger #s 2.0 2.4 2.5 3.0 New stuff with lots of stuff, hoses,pumps,belts,wires,black boxs,oil sumps,valves, cams, and blowers. I am sure I left some out. 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.

[Raceman]

I really doubt that the exhaust change was all about weight. Surely if the T1 style was more effective they wouldn't have ditched it to save a few lbs.

Incidentally, the Twister and Twister1 have a different party number log. Is it just about water discharge? I've been gonna compare em, but haven't gotten around to it.

[jay1]

i guess the biggest problem im having is ,i have a three cylinder snowmobile engine ..w/ a 65mm bore . that makes more hp then any stock 2.0l ..and this with 3 less cylinders...please dont get me wrong im not dissing the 30 + years of experience, what anyone else has done, or the amont of cash spent on enginering......maybe what im thinking is just plain dumb on my part.. for what its worth, i still think theres alot lost power in the "tuning" of an outboards exhaust...i absolutly understand why they use the benifits of one cylinder pushing the spent gas of another.(120 deg firing) .....maybe i should ditch the three individual chambers and put a exhaust manifold on my sled................................................................................................ ...........................................

[Mark75H]

Read this part again:

Sled and bike engines will only be used on vehicles practically identical to the ones the engineers put it on; outboard engineers just aren't as lucky.

(1)Outboards can not be has highly tuned as a sled or bike motor because the designers and makers have no control over how it will be used.

(2)Bikes have clutches and multi speed transmissions ... at least 5 or 6 selectable gear ratios; sleds have variable clutch drives. Boats have neither and the motor must have excellent low range torque to get the boat over plane that CANNOT be compromised for top end power.

[jay1]

(1)Outboards can not be has highly tuned as a sled or bike motor because the designers and makers have no control over how it will be used.
the boat is a old stv v bottom..pickle fork tunnul.. its use ...you will prolly never see me at a "race" and more than likely ill be the only one ever in it. the oppertunity to drive it depends on when and if i can break away from the family for a strong dose adrenalin..and i cant see myself cruzing it.. ////(2)Bikes have clutches and multi speed transmissions ... at least 5 or 6 selectable gear ratios; sleds have variable clutch drives. Boats have neither and the motor must have excellent low range torque to get the boat over plane that CANNOT be compromised for top end power. now correct me if im wrong on this one..do ya think im gunna have a problem getting the rrr's up ..light boat, over the hub exhaust, no hydrolic jack ,set high.. im not racing it...... 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...