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Old 01-22-2014, 12:26 PM
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Join Date: Sep 2008
Location: Michigan
Posts: 767
Originally Posted by winmutt View Post
While this is normally true, I was seeing high EGT from advanced timing. I adjusted it this weekend and retarded it and saw 200* drop!

Fwiw I saw 1650 on more than one occasion.
With prechambers, timing is limited to the burn hole size (total area). Because of the throttling effect of the holes, the pressure temperature in the Prechamber, reaches ignition temperature at a later time than the cylinder does, because the cylinder pressure is higher than the PC pressure due to the restriction of the burn holes. There for, max injection timing is limited to how soon the weakest cylinder's PC temperature reaches ignition temperature, injection any earlier that that results in a build up of dense fuel in the PC.

Given the above, once the PC air temperature reaches ignition temp, the fuel starts to burn, nail, and smolder, not good combustion, so the PC pressures after injection are not what they should be, and residual fuel in the PC will continue to flow out of the PC well after TDC, which is not as bad to retarded injection timing, but has the very similar results in EGTs and Smoke..

I had my timing as far as I could go, and sometimes it would be a bit cranky to get started. After I increased the Burn Hole area, I was able to max out the timing slots and it started with out hesitation. It also ran quieter, and had a lot more torque with lower EGTs for the same fueling curve.

With the larger burn hole area, my PCs were able to fill faster, there for reaching ignition temperature sooner, allowing the injection to happen sooner. Then after ignition, the larger holes allowed the pressure to leave the PC into the cylinder at a grater rate, so the cylinder pressure would be higher sooner, making more power.

Timing is directly limited to the PC’s ability to breath.

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Old 01-27-2014, 08:37 AM
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Join Date: May 2006
Location: Boston
Posts: 1,410
EGTs with advanced timing:

Well I can say that from my perspective the advance of 2 degrees (14 to 12deg on the IP tang with RIV lock tool) has the effect that temperature at 60 mph dropped from 700 to 600F. Of course this needs more testing and attention and the 700F I measured in a hot desert climate in the Middle East and now I am measuring 600 in a brutal Boston winter... so I need to wait until driving conditions are more comparable and then report back. But so far I can see lower EGTs.
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Old 05-05-2014, 07:06 PM
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Join Date: May 2006
Location: Boston
Posts: 1,410

With my 12degrees ATDC (RIV) I am experiencing much better EGTs compared tp the 14 degrees ATDC

at 60 mph 500-550F
at 75mph 650-700 F

And my gas mileage is much better.
Also the sound of the engine feels better.

So I am happy with the 2 degrees earlier timing.
Thanks everyone contributing

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Old 05-13-2023, 03:48 AM
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Join Date: May 2023
Posts: 1
Originally Posted by tjts1 View Post
I've accumulated a a few shots so here we go. All these were filmed at 240fps and played back at 24fps so you're seeing 1/10th speed.
The DN0SD265 stock nozzle that came out of my car. I cleaned and rebuilt it 15K miles prior.
dn0sd265 15k - YouTube

DN0SD265 from the JY, unknown age and mileage.
Pop testing old DN0SD265 - YouTube

Brand new DN0SD193 Bosch India nozzle made for VW set to 2100 psi. This nozzle has less lift than the stock MB nozzle with a simple non flat cut pintle. It also has less lift than the stock MB nozzles. I ran these for about 1000 miles before switching them out. I notced they are louder on cold start but quieter once warmed up than the stock nozzles. After a while they started to smoke at idle and high RPM WOT which I didn't like. The fuel coming out of these nozzles seems to hit with a lot more force than any other nozzle. I figured that would be good but I guess not.
DN0SD193 India brand new - YouTube

The last video is what I'm running right now. Bosch France DN12SD290. have a 12 degree spray angle. They were originally used on early 90s Fiat and Alfa diesels. Yes, they are very different from stock MB nozzles and quite the opposite of what MB considers a GOOD spray pattern. The video doesn't really tell you enough about the spray pattern. As seen from the top on small strokes it makes a triangular pattern, sort of looks like the MB star. On large strokes it makes a perfect cone spray pattern.
Driving these nozzles I notices a few things. Once warmed up the engine is extremely quiet. I can hear my sticky valve lifter quite clearly. There is ZERO smoke at idle and low throttle angle, a little bit of smoke at high. Theres a lot more torque at low RPM before the turbo builds any boost. Works well with the manual transmission.
DN12SD290 - YouTube

I wasn't able to capture a good screen shot of the DN12SD290 nozzle but the pintle looks like the picture on the right.

The DN0SD193 nozzle looks like drawing "1". The stock OM603 DN0SD265 nozzle looks like the picture "2b" with its flat cut.

Here's what MB has to say about nozzle spray pattern. Clearly the DN0SD193 nozzle is most like the picture so naturally I assumed this would work well in the OM603. It didn't.

Even compared to the stock OM603 nozzle, the 12 degree Fiat/Alfa nozzle has more low end torque. The plan right now is to put a few miles on these nozzles and see how they do in the long run. I have a couple of other nozzles I want to test out if these don't do well.

The 12 degree nozzles are popular on the German language SVO/WVO/biodiesel forums, mostly in swirl chamber engines, not MB prechambers. The theory is that the 12 degree nozzles can push fuel onto the walls of the prechamber without hitting the inpingement ball in the center of the chamber thats supposed to atomize the fuel. My experience is that the 12 degree nozzles work very well in the MB prechamber but its something to keep in mind.
Hi tjts1, I'm mesmerized by your posting of using the DN12SD290 nozzles and comparison, but none of the YouTube Video links are active. They all come up as "private video"

Is it possible to see the videos of the spray patterns please.

And I know this is an old post, but now, years later, your conclusion of the DN12SD290 nozzles?

Thank you and holding my breath for a reply...
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Old 05-21-2023, 05:15 PM
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Join Date: May 2023
Posts: 10
If you don't know you better find out. I mean is it science or not?
Its been like this for at least the last 50k. If somebody knows how many degrees of movement are in the IP flange I would love to hear it.

No matter how much you play around with the timing, chances are you're not going to hurt the engine.

Sent from my iPhone using Tapatalk

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