I wanted to get a discussion going on this topic among the smart people here such as Brad, DP, Speeddog, Howie etc. As you may know my 900ss engine has been heavily modified, I've had no modifications done to the timing; however my Ignitech is set up with the rev limiter function at 9500 RPM and the ignition advance maximum is 33 deg. I plan on running high octane gas exclusively but I'm still concerned about pinging and I'd like this engine to be trouble free for many years to come, especially because I don't plan on babying it. For what it's worth, the powder coating on my heads is pretty darn thick so that may contribute to a hotter running engine as well.
At what point do we determine a colder plug is a good idea or a bad idea? The only "bad" I can see is the potential for wasted spark/possibly fuel economy/power loss (which would be counter intuitive after the $$ I've spent on mods) There really doesn't seem to be much in the technical archives of any of the boards on this topic. What formula/method is applied to even determine when a different heat range should be used?
http://www.ngk.com.au/spark-plugs/technical-information/heat-range-explanation (http://www.ngk.com.au/spark-plugs/technical-information/heat-range-explanation)
no idea. if they're too cold they'll foul a lot. you could try a 9 if you wanted to. I don't think I've ever gone down based on comp alone. it's more running temp and how much heat they'll generally have around them as i understand it. the water cooled bikes always ran 9, and the 4v are now at 10, possibly due to the higher temps they generally run with the higher idle speeds, etc.
if it was a race bike it'd be heat critical, but i can't see a road bike being loaded anything like that. although having powder coated heads may influence it more than anything else.
This is going to be an interesting thread [popcorn] I think other people's experience will be your starting point. I would also suggest a dyno run. Lean increases the possibility of ping.
Refresh my memory. Heads stock other than a bit of clean up and porting? If the heads are stock, why such a high rev limit?
I'm with Brad. A colder plug on that motor with the intended use will most likely foul.
Pinging will most likely be fuel/compression related and not plug related.
Quote from: howie on March 25, 2015, 05:21:56 AM
This is going to be an interesting thread [popcorn] I think other people's experience will be your starting point. I would also suggest a dyno run. Lean increases the possibility of ping.
Refresh my memory. Heads stock other than a bit of clean up and porting? If the heads are stock, why such a high rev limit?
If he's running FCR's with short manifolds he can squeeze more out of the 900.
Quote from: howie on March 25, 2015, 05:21:56 AM
This is going to be an interesting thread [popcorn] I think other people's experience will be your starting point. I would also suggest a dyno run. Lean increases the possibility of ping.
Refresh my memory. Heads stock other than a bit of clean up and porting? If the heads are stock, why such a high rev limit?
Porting and larger valves. I guess that is kinda high...I'll change it after I get to know this motor a little better, the indicated red line on this motor is 10k I believe and I have no idea yet where the power is going to taper off on this thing after the mods.
I do expect this thing to run hot, the powder coating is everywhere heads/barrels/cases and I expect to be in the higher revs often, but maybe a bigger oil cooler would be a better idea. I'm also moving out of OH and further south after this year where I can ride 12 months.
I wonder if the Corse/race spec versions of Ducati's motors typically run colder plugs.
FWIW, my ~race tuned 750/800/839 11:1 is specified with stock plugs by builder Kämna. Had something different for the first couple thousand miles running in.
You're running stock conrods and stock length manifolds for a street bike? If that's the case I would limit rpm to 9K.
Manage pinging with your ignition, jetting and fuel Octane. I can send you a base map I have used on two 944s and my 904, all with high comp. Adjusting from there is easy to get the balance between smoothness, eliminate pinging and response in the low and midrange with street testing.
All those bikes I mentioned run stock plugs or iridium equivalents, Ignitechs and big coils with no issues once the ignition map is sorted.
Thanks T [thumbsup]
are the Exacfit coils considered high voltage/HD coils? along the lines of the Dynas?
They pack a punch for their size and must be up there. Maybe they use a thinner wire to get the winding because the Dynas are hand grenades. I don't know how they do it, but someone expert in electrickery will know.