Diesel pre detonation?

[Dozerboy]

So over the last few months 3 when I stepped on it my truck pops and bangs for second. The first 2 where when I was on the hwy and went WOT. The 3rd I was going 40mph went I just rolled into it a little hard. The engine was cold that time. It almost sounds like 2 step or anti lag on a gasser. Lots of black smoke when it happens. My truck is lambda limited to only haze other then a small puff below 1300rpms. I get on my truck pretty often, so it it's not like it happens on a regular/consistent basis. The only thing I can think of is that I increased the timing a little in that time frame from 11*/12* to 12*/~13*. The only thing I can think of is when the star's lineup perfectly I get some pre detonation. I run quite a bit of timing down low for mileage 12* maybe even 13* at 45mm3.

S&S 100s, Exergy 12mm, Danville 3794 Stg2.

Thoughts other then bumping the timing back down?

 

[2004LB7]

I would be more inclined to think it was a wiring issue. Maybe a rub through or loose connection that only shows when the engine is torquing over during acceleration.

 

[Dozerboy]

I would be more inclined to think it was a wiring issue. Maybe a rub through or loose connection that only shows when the engine is torquing over during acceleration.

Definitely not impossible, but I pretty much have reloomed and looked over my entire engine wiring when I did HGs.

 

[2004LB7]

What about valve lash? Or rocker issues?

 

[Chevy1925]

Pull back the timing and see if it stops. You might be hitting the truck with too much when cold and the multipliers kicking in.

Mine had a hard time with knock when cold and that intermediate area between decent load, no boost and 1700-1900rpm. Even had some buck. I cut main timing in that area way down to 6-7* and adjusted the pilot timing with the calculator based on my injection uS and current timing table. Made a nice difference in smoke output and noise but I still have some I’m playing with (very minor amount). Adjusting the pilot timing tables to all the same made no difference so I’m going to play with the multipliers for when it’s cold.

My oval pistons make this a bit harder than normal ones as they are inherently noisier but your description sounds very similar.

 

[Fingers]

Sounds like not enough air for the fuel load. Knocks like hell when that happens. Basically, your putting the fire out in the cylinder.

 

[Dozerboy]

What about valve lash? Or rocker issues?

I wouldn't think so. I only put on 10,000 miles or so since I did the head gaskets. No other noises or anything. I would think it would be more consistent if it was a problem like that.

 

[Dozerboy]

Pull back the timing and see if it stops. You might be hitting the truck with too much when cold and the multipliers kicking in.

Mine had a hard time with knock when cold and that intermediate area between decent load, no boost and 1700-1900rpm. Even had some buck. I cut main timing in that area way down to 6-7* and adjusted the pilot timing with the calculator based on my injection uS and current timing table. Made a nice difference in smoke output and noise but I still have some I’m playing with (very minor amount). Adjusting the pilot timing tables to all the same made no difference so I’m going to play with the multipliers for when it’s cold.

My oval pistons make this a bit harder than normal ones as they are inherently noisier but your description sounds very similar.

I didn't even think about the Timing Multipliers. That would make sense as to why so far it has only happen once per drive and it is the first time I get on it.

Sounds like not enough air for the fuel load. Knocks like hell when that happens. Basically, your putting the fire out in the cylinder.

That aswell could be a contributing factor. While I limit fuel pretty substantially most of the time. I almost don't limit it 1400rpms and below. Potentially if I was below 1500rpms I could be commanding all the fuel it can very briefly.