11-13-2009, 08:39 PM #1
Tuning on the trailer for max RPM ???
Now that I think I'm on
top off the impeller issue I need to check max rpm. To balance the carbs for low speed and idle I did it one cylinder at a time. i.e. putting the H.T leads of the other two cylinders on dummy plugs earthed out so it was only running on one cylinder at a time then adjusted the low mixture for max rpm once they were all a the highest RPM I then set the linkages to get the same RPM on all cylinders.
My question here is to get max RPM once I have done this would it be advisable to use the above method a WOT while holding the ski on a trailer. As I see two problems.
1. Will the nose of the ski with stand the pressure of thrust or will it crush (with one or even three cylinders running)
2. Will the crank handle the pressure of only one cylinder running? Obviously the Pto will be fine and to a lesser degree the Cent but if I was to run just the Mag this way will the load on the crank be way to much down its length and pull it out of phase.
I thought using the above method would be the best way to tune the carbs for Max rpm and then do a check on piston wash after some running as this method would be like loading it up on a dyno but have never heard of anyone doing it so are very cautious at this stage. Otherwise I'm thinking of fitting oxygen sensors in the first half of the pipes and tuning it on a wide band.
11-13-2009, 11:20 PM #2
- Join Date
- Jul 2007
- near Toronto, Canada
I don't think you can tune the carbs that way. The engine will not achieve full RPM under load without all three cylinders firing, so the air flow through each carb will only be a fraction of what it would normally be at WOT.
Have you seen the Tuning tips for girls posts, originally written by Watcon Randy?
11-14-2009, 05:12 PM #3
So to use that method I'd need to fashion up a "test" impeller that would allow it to rev higher.
What about using o2 sensors and a system such as "innovate lm1" I haven't seen thoose metioned here much either.
I read Randy's tuning tips and used thoose when I first dialed it in and got it pretty good but it's not perfect. I'm very new to multi carburetor setups and are finding it very hard to adjust 9 things (and yes there is 9 things to adjust) and get it running great for the conditions on the day. Hence why I'm looking for a method that give me "real time" results without hours on the water.
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