There is no way a drop in temps could cause that on a stock motor. I have seen them jetted lean so they can run at 10,000 ft, and run at 4000 ft just fine. The drop in temps by midnight could have only been thirty degrees at most. It sounds like a defect to me.

Justin if he wants to put it back to completely stock, I have three stock pistons, your welcome to one. Sorry to hear is wasnt something easy.

 

Just to update everyone. The ring end gap was good. So that leaves lean or Deto. There is no sign of being lean, and I am pretty sure I was still rich on nitrous, so by process of eliminations, it must of been Detonation. Thanks to all who helped with my issues. She will be alive and well in the near future.

 

Do you mind me asking what the ring gap was and where in the cylinder you checked it?[img]i/expressions/face-icon-small-smile.gif[/img]

 

I didnt. And I know there is variations in cylinders. I talked with Eric today about my brothers machine, and he said not to worry, he had them gapped for us.

 

That's good enough for me[img]i/expressions/face-icon-small-wink.gif[/img]

 

Jed,

Help me out here on the logic path to figuring out this problem. Isnt a lean condition a path towards detonation? I suppose there are other things that can cause detonation, including advanced timing. But if fuel is correct (or lean conditions at bay) then detonation is also put at bay. Help me out here man!

Marky

 

Here's my thoughts. First most people think preignition and detonation are the same, while they are not. One is a derivative of too advanced timing and the other is of internal combustion before the time had come to do so. Both can show the same signs, but are different. I am sure someone has a better explanation than I.

Second, lean is a condition of too little fuel. It melts stuff.
Actually being to rich can cause detonation as well. It usually will attack the side of the piston as its not igniting in the exhaust side.


When looking at my situtation, it was a little fuzzy to me. What I thought looks to be true, but I was unsure. When I looked at my plugs, they looked perfect except for the oil. Its to bad I couldnt see them before the oil, then I could tell if there was deto. Like someone explained, deto is like a hammer. The charge is igniting before the piston reaches top dead center if you will. So it starts the ignition process to soon and multiplys the force being driven on the piston while it still is coming up, trying to make it go down. Normal signs are pitting on the edges of the piston, speckles on plugs, and evidently folded over ring lands,lol.
If you were lean, it can cause it to detonate also. So its a fuzzy line.

Last year when I melted my plugs ends off. I new I was good with the octane, as I had been running it for a while. But I wanted to find the fine line with fuel mixture. So I started leaning her back down, till she had no plugs left. Thats a good sign you are too lean,lol.

But here's another one. Jeremey's and Matts quads both. They both run a procomm box. When they tried to run the 25 shot, even with straight 110, it would burn the plugs off and detonate. You could hear them both. I think the detonation on them was building the heat to burn the plugs off. When they both went down to a 20 shot, they both ran fine. Matt runs pump 91 with his 20 shot still to this day. We ran mix in Jeremeys just for insurance.

Now this is still fuzzy stuff to me as well, so if anyone can chime in there thoughts, that would be great.

I sure hope I confused you some more, I know I confused myself,lol.

 

I think a lean condition can be the straw that breaks the camels back as far as pre-ignition is concerned. Pre-ignition is caused by enough cylinder heat to ignite the vapors before the spark plug fires. Compression energy transfers to heat. That is why diesels don't have plugs. They simply use the heat created by their extremely high compression to ignite the mix.

If you raise the compression on a motor, it creates more heat earlier in the compression stroke so if the spark timing remains unchanged, you will likely need a slower burning fuel to keep the motor from igniting prematurely. Higher octane is one way to accomplish this. Another way is the designer fuels like U4. There is a percentage of Nitromethane mixed in with the roughly 100 octane racefuel. Nitromethane burns very violently but very slowely so it allows you to run 100 octane when you should be running straight 110.

The other thing that happens is from ignition advance. You can have detonation too early for your setup by having too much spark timing advance. This will also require a slower burning fuel to make sure you are getting combustion at the optimal time and all at once.

Pre-ignition is usually made up of hundreds of little explosions happening in the hotest spots of the combustion chamber prior to ignition.

If I understand correctly, detonation due to excessive spark timing advance is just one big explosion that happens when the piston is in the wrong place. Basically ignition is out of time with flywheel and cam timing.

If I am off base on any of this, please tell me. I want to make sure i understand it right.[img]i/expressions/face-icon-small-wink.gif[/img]

 

I always thought it was the other way around.......?

 

Hard to tell. I don't know if pre-ignition means ignition prior to spark or spark firing too early.[img]i/expressions/face-icon-small-smile.gif[/img]

I don't mind switching it around[img]i/expressions/face-icon-small-happy.gif[/img]