Thanks Thanks:  0
Likes Likes:  0
Page 1 of 4 1234 LastLast
Results 1 to 10 of 32

Thread: Max timing advance

  1. #1
    Team Member
    Join Date
    Apr 2007
    Location
    Country Victoria Australia
    Posts
    55
    Post Thanks / Like

    Default Max timing advance

    It seems i can't find my workshop manual............could someone please let me know what the max timing advance at WOT is for a 1988 3cyl 2str Yamaha.
    Powerhead is standard, no work....................................yet

  2. #2
    Team Member
    Join Date
    Nov 2008
    Posts
    20
    Post Thanks / Like

    Post Powerhead?

    What HP is it???

  3. #3
    Team Member
    Join Date
    Apr 2007
    Location
    Country Victoria Australia
    Posts
    55
    Post Thanks / Like

    Default

    OOPS
    90hp.

  4. #4
    Team Member mercmack's Avatar
    Join Date
    Dec 2004
    Location
    cedar city,Ut
    Posts
    475
    Post Thanks / Like

    Talking Factory Service Manuals

    Why Dont You Try E-bay..just Put Down Yamaha Service Manual.
    Its Worth The Effort..a Lot Of Those Eng Have A Per Fixed Setting
    The Computor Or Cd Box Does It..

  5. #5
    FFX-61
    Join Date
    Aug 2005
    Location
    Stellwagan Ledges
    Posts
    2,095
    Post Thanks / Like

    Default

    stock = 22deg +/-1

  6. #6
    Team Member
    Join Date
    Apr 2007
    Location
    Country Victoria Australia
    Posts
    55
    Post Thanks / Like

    Default

    Thanks fred.....

  7. #7
    FFX-61
    Join Date
    Aug 2005
    Location
    Stellwagan Ledges
    Posts
    2,095
    Post Thanks / Like

    Default

    stock timin is for stock revs (5800-6000), as rpms go up (7000-8000) timin Must go down. drag boat guys run more timin, but do not hold the moda at rpm,
    as soon as it peaks it's shutoff

  8. #8
    Team Member
    Join Date
    Mar 2009
    Location
    Bloomington, MN
    Posts
    29
    Post Thanks / Like

    Default

    Quote Originally Posted by Fast Fred View Post
    stock timin is for stock revs (5800-6000), as rpms go up (7000-8000) timin Must go down. drag boat guys run more timin, but do not hold the moda at rpm,
    as soon as it peaks it's shutoff
    That seems so counterproductive Fred. Back in the days of distributors and vacuum advances, they would give it max advance when the engine wasn't pulling and could handle it. The flame pattern is at the same speed whether it's at 1,000RPM or 8,000RPM (I would think) so at the higher RPM you need more lead time to get maximum expansion at or slightly after TDC. Could it be you're getting too lean a mixture at higher RPM which would cause detonation? I would think the retarded timing would hurt the low to mid-range. The oil in the fuel is already slowing the flame pattern down. What's the thought behind it?

  9. #9
    FFX-61
    Join Date
    Aug 2005
    Location
    Stellwagan Ledges
    Posts
    2,095
    Post Thanks / Like

    Default

    true, 2stroke timmin, the more timmin it has the harder it pulls,to a point.
    at 22deg max that 90hp will pull nice to 6000 and stay there, make a pull to 8000 at 22deg and try to hold it thare it's guna melt the pistons out of it.

    Part one of "Secrets of the OMC Mod 50" : http://www.boatracingfacts.com/forums/showthread.php?t=2052

  10. #10
    Team Member zul8tr's Avatar
    Join Date
    Oct 2008
    Location
    Orlando, Fla
    Posts
    708
    Post Thanks / Like

    Smile Timing

    Quote Originally Posted by 50sFlash View Post
    That seems so counterproductive Fred. Back in the days of distributors and vacuum advances, they would give it max advance when the engine wasn't pulling and could handle it. The flame pattern is at the same speed whether it's at 1,000RPM or 8,000RPM (I would think) so at the higher RPM you need more lead time to get maximum expansion at or slightly after TDC. Could it be you're getting too lean a mixture at higher RPM which would cause detonation? I would think the retarded timing would hurt the low to mid-range. The oil in the fuel is already slowing the flame pattern down. What's the thought behind it?
    --------------------------------
    I agree with you on more lead time as rpm goes up and would be supprised if contrare to this. Not sure I agree (although you hedged your thought) if the flame front spreads at the same rate at different rpms. I have never seen test results on this but I tend to think that the flame travel would be different (suspect slower) since as the rpm increases volumetric efficiency decreases in a normal aspirated engine due to reduced fuel/air charge transfer time (and other engine deficiencies) thus less fuel/air charge per intake cycle at the higher rpms.

    Maybe a ME can chime in here with engine design and test specifics?

Thread Information

Users Browsing this Thread

There are currently 3 users browsing this thread. (0 members and 3 guests)

Similar Threads

  1. CDI 2 IGNITION With TIMING CURVE
    By OUTBOARDER in forum Technical Discussion
    Replies: 4
    Last Post: 11-04-2008, 07:10 PM
  2. "Swing" mag or fixed timing
    By Mark75H in forum Technical Discussion
    Replies: 26
    Last Post: 06-26-2007, 02:54 PM
  3. timing for johnson
    By john/rude in forum Technical Discussion
    Replies: 7
    Last Post: 12-19-2006, 02:53 PM
  4. Mag timing light and tweeter
    By bill boyes in forum Open Discussion
    Replies: 0
    Last Post: 05-03-2005, 08:52 AM
  5. Help!!! Kilo timing equipment needed!!
    By Mark75H in forum Open Discussion
    Replies: 5
    Last Post: 02-22-2005, 10:05 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
  •