Thanks Thanks:  0
Likes Likes:  0
Page 1 of 9 123456789 LastLast
Results 1 to 10 of 88

Thread: OMC 3 Cyl expansion Chambers

  1. #1
    Team Member
    Join Date
    Jan 2009
    Location
    NewZealand
    Posts
    48
    Post Thanks / Like

    Default OMC 3 Cyl expansion Chambers

    I am currently in the proccess of building a 3cyl 920cc omc to run pipes.

    Has anyone done this? I have had the side of the block milled and welded up to fit flanges. Obviously plugged where the exhaust used to exit so the cooling water doesnt escape down there.

    What is everyones comments on expansion chambers over pure megaphones?

    I will build a set of megaphones purely to run it at night and get some footage of her thrown flames out!

    Everything else has been done to it. 19s fron half. Finger ported, head work etc etc. The never ending quest for more speed has brought me to exhaust work.

  2. #2
    Team Member Detroit Whitey's Avatar
    Join Date
    Oct 2006
    Location
    lake Erie
    Posts
    112
    Post Thanks / Like

    Default

    You need to talk to Tim Kurcz

  3. #3
    Team Member
    Join Date
    Jan 2009
    Location
    NewZealand
    Posts
    48
    Post Thanks / Like

    Default

    Ill try get in touch with him, cheers.

  4. #4
    Sam Cullis Mark75H's Avatar
    Join Date
    Nov 2004
    Location
    Annapolis, MD USA
    Posts
    1,795
    Post Thanks / Like

    Default

    Steve Benson built some with expansion chambers too. Years ago his were among the fastest.

    Both guys are members here on BRF and have posted recently.

    Expansion chambers will make 30 to 50% power increase, megaphones 15-18% max.
    Since 1925, about 150 different racing outboards have been made.


  5. #5
    Team MSR
    Join Date
    Dec 2004
    Location
    Durham, Ct.
    Posts
    67
    Post Thanks / Like

    Default Yep....

    E mail me at teammsr@comcast.net or call me at 860-349-9310 and we can talk.

    Michael D-1

  6. #6
    Team Member BRIAN HENDRICK's Avatar
    Join Date
    Nov 2004
    Location
    Merrickville, ON,& Sebring,FL
    Posts
    84
    Post Thanks / Like

    Default

    This is a 497 set up as a FEH with very nicely engineered triple expansion chambers. It ran quite well in Reg-2 about ten years ago. However with the advent of the Runne 'pulse' tuned system, it was no longer (as?) competitive. I suspect that as the motor was designed to be 'pulse' tuned, that simply bolting on a set of pipes will not be effective, unless you were to re-engineer the porting. But nothing ventured, nothing gained.
    Attached Images Attached Images   

  7. #7
    Team Member
    Join Date
    May 2005
    Location
    Battle Creek, MI
    Posts
    296
    Post Thanks / Like

    Default Benson Built Pipes

    Quote Originally Posted by BRIAN HENDRICK View Post
    This is a 497 set up as a FEH with very nicely engineered triple expansion chambers. It ran quite well in Reg-2 about ten years ago. However with the advent of the Runne 'pulse' tuned system, it was no longer (as?) competitive. I suspect that as the motor was designed to be 'pulse' tuned, that simply bolting on a set of pipes will not be effective, unless you were to re-engineer the porting. But nothing ventured, nothing gained.
    Brian,

    If that is the rig that Fitzgerald ran, it was Mike Lopez rig that Benson built. Benson had some fast chambers in the time. I have no doubt the chambers, when combined with the right porting and other modifications within work very well.

    There is no bolt on chamber that would give you the best a chamber can deliver. At least not one I have found, or heard of. Maybe someone has hit on something ?

  8. #8
    John (Taylor) Gabrowski
    Guest

    Default Look to todays 3 Holer racing sleds for technology leads.

    These days you see faster changes in technology in the 2 stroke racing snowmobile arena in North America then anywhere else.

    You do see many 3 Holers with 3 pipes (but they are fully supported in sled bodies and platforms) but you also see many sled 3 Holers with a single pulse tunned manifold coupled to a single expansion chamber as the system used. Their horsepower is very bizarre.

    Such a single pulse tuned 3 cylinder coupling exhaust manifold coupled to its design expansion chamber would be a practical route for a OMC 3 Holer to increase horseower yet instead of the pulse tunned manifold and dump pipe you see commonly now or the Lopez unit of a decade ago. Too many pipes you have breakage too boot where a single design expansion chamber and pulse tune manifold is a happy medium between that and pulse tune manifold with dump pipe. What will racers do? Study snowmo racing information sites and think about it.

    Thing is you add more horsepower and another prop what do you do with the raceboat technology to handle significan increases in horsepower?

  9. #9
    Team Member
    Join Date
    Jan 2009
    Location
    NewZealand
    Posts
    48
    Post Thanks / Like

    Default

    [QUOTE=

    Thing is you add more horsepower and another prop what do you do with the raceboat technology to handle significan increases in horsepower?[/QUOTE]

    At the moment the bout is doing about 90MPH

    I have heard of this exact hull doing over 100 easily with a 31M engine on it.

    I am quite confident that if I can get the boat to do 100-110MPH it will handle it nicely. I don't want to buy a 31m and bolt it on purely because I want to get the boat going that fast, not just buying somebody elses motor to get me to that speed...... Kind of got a point to prove to a few people.

  10. #10
    Team Member
    Join Date
    May 2005
    Location
    Battle Creek, MI
    Posts
    296
    Post Thanks / Like

    Default Snowmobile vs OMC

    The technology is not as simple as adapting from the sled to our outboards. The engines in a sled are radically different than our outboards from OMC. They will get you in the ballpark, and are a good starting platform, but you will be dissapointed if you simply bolt on a set from the same CC engine.

    Put three chambers on a sled that has only a 3 into 1 configuration and see what happens.

    Johnsonracer, where are you from ?

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. merc 25xs mod expansion chambers any info ??
    By bobvdinghyracer in forum Technical Discussion
    Replies: 1
    Last Post: 12-07-2007, 03:15 PM
  2. Loopers with expansion chambers
    By Heliarc in forum Outboard Racing History
    Replies: 4
    Last Post: 02-10-2007, 11:34 AM

Tags for this Thread

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •