timing knock?

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getblown5.9

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ok for those who run fairly high timing, the pronounced knock you get from the higher timing when the truck is idling, what is actually causing the noise? is it piston slap? if it does this at idle is letting the truck idle a bad thing then? i just dont wanna do permanent damage by driving my truck at too low of an rpm or letting it idle when i can hear it making the sound.
 
I believe it is a fuel knock! but not sure how to decribe it! P-pumped 24v's seem to all have it!
 
Timing being advanced to the point it causes a knock is created by combustion happening while the piston is still in the compression stroke. It is hard on the rotating assembly.
 
Damn so in a sense it's just like pre-ignition in a gas motor or more like just detonation (yes they are different). Pre-ignition tends to ruin things super quick in gas motors, detonation not as bad but isn't good either. Anyone else have any input on this?
 
It's the sound of the ignition of diesel fuel too early and the explosive force of the fuel trying to force the piston back down before it gets to TDC...

I'm sure it's hard on the rotating assembly, how long will it take to do damage? Don't know. I suppose bearings will wear sooner.

It's the nature of the beast...

My thinking is that 15 second bursts of 4500 rpm full load, max EGTs, dragging a 50,000 lb sled down a dirt track will have alittle more effect on the rotating assembly...$.02
 
I have a different theory on the timing-induced rattle subject. . . .the more advanced timing is, the less cylinder pressure present at the beginning of the injection event, which results in a larger quantity of fuel in the cylinder before it ignites, resulting in a bigger bang. Fuel doesn't ignite the moment fuel is injected, there is a latency period, and more timing advance creates greater latency IMO.
 
VMacKenzie said:
I have a different theory on the timing-induced rattle subject. . . .the more advanced timing is, the less cylinder pressure present at the beginning of the injection event, which results in a larger quantity of fuel in the cylinder before it ignites, resulting in a bigger bang. Fuel doesn't ignite the moment fuel is injected, there is a latency period, and more timing advance creates greater latency IMO.
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That is a good theory, anybody have a way to back that up?

I would be more concerned if you injectors and timing are washing the cylinders down than with the noise.
 
roachie said:
That is a good theory, anybody have a way to back that up?

I would be more concerned if you injectors and timing are washing the cylinders down than with the noise.
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agreed! I don't think that normal driving and idleing less than 5mins will hurt anything, unless there is an oiling issue! I would wind it out or keep the revs up and try not to lug it so much
 
I often wondered what caused it and if it would hurt anything also. My timing is @ 23deg.
 
U shoud b ok lee mines @ 28+ and its a litttle to much after pulling the head off this week , its going back down a little, I had both spray out of the bowl just a little it was hitting the edge some and my cylinders had some scuffing either from washing or what not lets just say my rings are shot . New ones back in
 
Rods said:
U shoud b ok lee mines @ 28+ and its a litttle to much after pulling the head off this week , its going back down a little, I had both spray out of the bowl just a little it was hitting the edge some and my cylinders had some scuffing either from washing or what not lets just say my rings are shot . New ones back in
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What spray angle of injectors were you running?
 
3 deg narrower that stock , I'm going to talk to the injector guy and tell whats going on . I'v been wanting to try the 6 hole tip so I''l se what he can do on angles for them
 
I would say advanced injection timing might be alright at idle seeing as how there is less cylinder pessure, but when you introduce boost then the diesel has the tendency to "preignite"....in theory, lol
 
you got me scared now, running 26* on off the shelf DDP vp44 injectors. im changing the oil tomorrow i will check it for fuel contamination and any sings of motor wear.
 
Quad told me the Adrenaline will advance timing to 26* when all the conditions are right as far as boost, iat, and load. Apparently 26* is not washing down cylinders.
 
getblown5.9 said:
you got me scared now, running 26* on off the shelf DDP vp44 injectors. im changing the oil tomorrow i will check it for fuel contamination and any sings of motor wear.
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any engine wear that your going to see is just the cam breaking in, if you see anything from that, it hasnt been running long enough to see anything else yet.


I would think that the higher the rpm the worse the spray angle would get, from the boost distorting the spray pattern. this all goes back to a bigger less hole injector would help cure the issue since the spray is more dense and less likely to be comprimised, along with common rail pistons that have the taper around the bowl area that will help contain the excessive fuel. how many holes are yours rods and tj?
 
Big Blue24 said:
Quad told me the Adrenaline will advance timing to 26* when all the conditions are right as far as boost, iat, and load. Apparently 26* is not washing down cylinders.
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well as new as the box is, and the likeliness of anyone who has hit that kind of timing for a long enough amount of time to do damage is slight to none, much less someone tearing one down to see what it does. im sure my pistons are burnt and my cylinder walls could use some attention after i saw what my egts are the last time i pulled, i had the comp1 tune in and right around 100ft my temps were 1950 something, i had a few people pm and say that they saw fire in the smoke. the adr is by far a awesome box for competition.
 
getblown5.9 said:
you got me scared now, running 26* on off the shelf DDP vp44 injectors. im changing the oil tomorrow i will check it for fuel contamination and any sings of motor wear.
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After yr checks I would dyno it and see if the timing really needs to b that Hi say start around 16 then 20 then 25 I know its time consumming but would b worth it in the long run
 
I agree. I'd be interested to hear what effect it has. That's where the adjustable pump gear would come in handy.
 
You are going to need some decent timing to maintain the higher rpms...

I also remember reading from the guy that hacked into his own ECM that the stock timing parameters ranged from say 6 degrees to 26 degrees (going from memory, its been a while). You have to remember though, it would only be at 26 degrees when all the conditions were met for a very small time period, unlike a p-pump where it would stay at 26 degrees all the time.
 
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