If he was lean and pre igniting why would his plug look good and not pitted?


Ron, at that elevation the burn is slowed WAY down as you should know. The burn is then forced to be faster with the nos and the way the cams work thats when i would think things went wrong. At the low temps and high altitude less oxygen is getting in the chamber would make the carbs extra lean with the noss. JMO I may be way off here...


You would have to have your timing about 48 degrees advanced and 13:1 on 92 octane to burn up at sea level id guess. With the slower burn up there and barely any advance I dont see how it would have gone that lean. Unless his headers were glowin on all motor. My son and I recently grenaded a very high comp 2 stroke motor with too little octane and nitro reving tooo high for too long but the rings were fine.

 

I just read the post above.


What cdi were you running? Maybe the advance on the higher rpm's on that particular cdi ramps up so violently that it burns it up in the higher rpms. Its probably fine till the curve goes up.

 

Ronny Woods.

 

I sprayed with the woods and high comp and only burnt tips when I went lean... BUT I had alot more pistin wall clearance than a stock jug. So I cant narrow it down to that... If you knew the engine temps it would tell alot.





I think I happen to have a woods cdi with no advance.



So what do you think happened? I think with the noss you went way lean in the cold.

 

I wasen't speaking to anyone's specific problem. I was simply responding to Marky's question.........as I understood it.

What you are saying sounds right to me. I know you need less octane at high elevations. That would indicate a slower burn right inherent in the fuel.

 

I do think this is partly backwards though. I need straight 110 at sea level on my 13:1 with 30 degrees advance. I am not sure you could get by with 0 deg advance burning 92 at 13:1 at sea level after the motor is fully warmed up. You might get by with 92 at 12:1 if you don't run more than about 25 degrees advance but that would seem like it is on the ragged edge........at sea level anyway.

 

I need to order me up a temp guage, thats for sure. I'll do it tomorrow.

I am almost 90 percent sure I was lean on motor. My machine had been shut off and turned back on and raced on all motor before it started blowing smoke. So that could have heat soaked it alittle right there. So if she was hot, at 45 degrees outside temp, I have another entirely different problem,lol. Heck it might not have even been that warm!

I think I had too little octane and too much advance for the amount of nitrous and power I am putting out. I am close to the century mark on nitrous, and think things are getting a little more stringent up there. I was running a mix of 110 and pump 91 at the time. And prior to this in warmer temps was running straight 110. I really dont think I was lean, as I would have to clean up the motor from fuel after every race. It hard cuz on nitrous I am sure I was rich, but on motor I think I was lean.

 

Ron, how did you get all that timing advance?

Do you actually plan on spraying 30 degrees?

 

Based on everything that has been said here, that is where my thinking is at to.

 

I think we are misunderstanding eachother. The stock timing curve is set at a maximum of 25 degrees advance. I have my MSD programmed to increase that by an additional 5 degrees from 2500 rpm up to 9000. That gives me a total of 30 degrees of advance.[img]i/expressions/face-icon-small-smile.gif[/img] Instead of my plugs firing at 25 degrees before TDC at 7000 rpm, my setup is firing at 30 degrees before TDC.

I have 2 degree retard option that comes into play if i enable it in the last 1000 rpm I believe. I don't know yet where I intend to set my advance for NOS. I am only running a 15 shot but it is something i still have to research.[img]i/expressions/face-icon-small-smile.gif[/img]