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Can you hear detonation, pre-ignition, in these motors?

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Can you hear detonation, pre-ignition, in these motors?

 
  #1  
Old 02-19-2010, 11:40 AM
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Can you hear detonation, pre-ignition, in these motors?

Can you hear detonation on these motors like you can in a gas engine?
 
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Old 02-19-2010, 12:01 PM
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I could be wrong, but isn't that whats happening when you're lugging on the engine at low rpms and it knocks pretty loud. Any other time, I'd say no because a diesel basically runs on detonation.
 
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Old 02-19-2010, 12:06 PM
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Compression ignition (pre-ignition in a gas engine) is how our engines run all the time.
 
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Old 02-19-2010, 12:06 PM
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The knock you hear, is the detonation knock. From what I have read, and observed as diesel motors progress, is the way the knock get to be less audible, is by creating more injection events per time to make each "explosion" less audible. For example, mech injected dodges, and OBS DI 7.3s, have the most audible knock. While 03-04 dodges, (similar to common rail), 05+ dodges (common rail), duramax motors (common rail), and 08+ 6.4's (once again common rail) are significantly quieter. I think some of the dodges have upto 7 injection events, per fueling at every compression stroke. Split shots for our trucks, are slightly less audible, then the single shots that came in OBS trucks. Atleast this is what I have gathered. Our injectors are also louder then CR injectors.
EDIT: Looks like I got beat.
 
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Old 02-19-2010, 02:31 PM
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I get that it's compression ignition, but can we have detonation? Or maybe I should ask, can we hear what would sound like a gasser "spark knock" if ignition occurs too early in the compression stroke?
 
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Old 02-19-2010, 02:44 PM
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On a direct injected engine, it's all timing. You can't have detonation until the fuel is injected. Of course, with advanced timing, you do get more of a knock.
Think about how quiet the IDI engines are compared to a tuned powerstroke.
 
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Old 02-19-2010, 02:51 PM
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Originally Posted by spdmpo View Post
I get that it's compression ignition, but can we have detonation? Or maybe I should ask, can we hear what would sound like a gasser "spark knock" if ignition occurs too early in the compression stroke?
If I understand your question, I believe the answer is yes... you hear it all the time, BUT the pitch will change/frequency is different. When you first start your truck and pull out on a cold day, you have one sound... pulling out from that same place after the truck is up to OP temp, and it's warm outside yeilds a different sound. Since I have two chips from different tuners, I can change them out quickly (have a hole in my PCM mount) and there is a distinct difference in the sound. I attribute that difference to the difference in the timing stratagies. I happen to know the one tuner is "aggresive" while the other is "conservative" as it relates to timing. Just my wag.
 
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Old 02-19-2010, 02:55 PM
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Originally Posted by spdmpo View Post
Can you hear detonation on these motors like you can in a gas engine?
In a way... yes.

If you retard the timing in a diesel, it will quiet the engine down a bit. But if you retard it too far, it gets really quiet, but becomes a laggy smokey pig.

Advance the timing too far, and it rattles similar to a cold engine.
 
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Old 02-19-2010, 03:08 PM
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By definition, the noise you hear anytime the engine is running is knocking.

The answer is no, there is no preignition on a diesel. There is no fuel to ignite until it gets injected.
 
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Old 02-19-2010, 06:54 PM
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Reason I ask is because this morning I drove away cold and was in the 60E tune. Normally I always drive away in the factory setting until I get warmed up but I forgot to switch the tuner. Just driving easy out of my 'hood and I was thinking this thing is really talking to me a lot louder than normal this morning. Yes I have conversations with my truck, I have some kind of issue that hasn't been identified apparently. Lots of the normal 7.3 clanging and clanking just more pronounced (went quiet when not under load). When I'm all warmed up in 60E the engine is nowhere near that loud. Put it in to the stock tune and it was so much quieter. I always noticed the engine was a lot louder when cold, just wondering why.
 
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Old 02-19-2010, 07:06 PM
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That'ed be advanced timing.................................. you know, the block killer.
 
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Old 02-19-2010, 07:20 PM
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Ya, I guess so. I didn't want to start another thread about the "T" word. But I'm not sure how I feel about what I heard this morning. It was pretty obvious. I'm confused as to why the hell it's like that only when cold.
 
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Old 02-19-2010, 07:28 PM
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Because the PCM also advances timing when the EOT is low. That coupled with tuning results in even more advanced timing, and the hammering you heard.
 
 
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