Injector/Prechamber Question - PeachParts Mercedes-Benz Forum

i-osprey · #1 11-12-2009, 08:46 PM

I am curious to know exactly what happens when an injector "pops" until ignition.

I have looked for diagrams, etc but I can't get what I am looking for.

My understanding is that a fine mist leaves the injector and enters the "prechamber."

What is the purpose of the prechamber?

It's my understanding that the prechamber only has a few holes through which the diesel enters into the cylinder.

How does that allow the diesel to stay "atomized?"

How much improvement can a new injector/nozzle give you?

I ask this because I will be installing my new Monark injectors tomorrow.

It's all a bit fuzzy to me now exactly how this works(not the installation, the actual functioning of the parts).

compress ignite · #2 11-12-2009, 10:06 PM

AND QUIET!

New Monarks (Nozzles alone) will make you think you've died and gone to Heaven.

IF, the Injectors are Pop Tested and Balanced...Otherwise you're wasting
a lot of the New Nozzles capabilities.

i-osprey · #3 11-12-2009, 11:12 PM

I bought complete new Monarks from C. Sean Watts.

He told me that they are in spec from the factory.

I'll find out tomorrow.

compress ignite · #4 11-13-2009, 12:02 AM

They're "Balanced" against each other and in the Bosch Specification for
opening pressure.

Enjoy!

#5 11-13-2009, 12:42 AM

I just replaced my injectors, two were pretty well shot (really bad spray patterns) so I just did them all. There was a notable improvement in power, nailing, and cold starting. The most obvious difference is improved low end power, especially with a cold engine.

79Mercy · #6 11-13-2009, 08:31 AM

Im also about to install new nozzles i'll use my friend pop tester to make surethey're balanced. I hope I see as big a difference as ya'll do.

C Sean Watts · #7 11-13-2009, 09:24 AM

Quote:

Originally Posted by i-osprey

I bought complete new Monarks from C. Sean Watts.

He told me that they are in spec from the factory.

I'll find out tomorrow.

I've never seen any come from the factory that were more than a few needle (on the gauge) widths from each other. BUT, for the ones labeled "135 bar" for 61X and 60X Mercedes w/ turbo, the range is actually 135-145 bar (min and max) provided the whole set is within three bar. Almost all I've seen have been 140, still within factory spec. but with plenty of margin for when the needles begin to settle into the seats. IF you have a complete new injector and find one NOT 140 + or - a couple bar, send it back to me. I WILL honor the factory warranty, the "source" will not, since - in their words, "We don't because we don't know what people are using for fuel."

I started importing them about 5 years ago, for VW and Volvo. In that time, I've had TWO nozzles and ZERO new complete injectors returned. SOMETIMES with old, serviced injectors we can try and try but not seal a leak but in that case we can almost always reuse the new nozzle.

NOT TO IGNORE YOUR O/P..
I'll second what CI said. The flame actually begins in the prechamber.
Ideal Engine: Fuel comes out in a cone pattern mostly atomizing on its own (with a good nozzle.) Ignition (from heat/pressure) begins a mm or so from the injector. Not every spray event is identical so the atomizer ball is there to break up what streams might be there into sprays. The only way for the fire to go as it expands is out the small holes. If we could see inside, the holes would look like tiny, little rocket engines or flame throwers.
Test Bench: A few mm from the injector you can still see a very tight cone pattern clustered together, almost like a stream. An inch or so you see a defined cone pattern like an aerosol can spray. After six inches or so, it's a fuel fog. Since we don't have six inches in the engine AND since the fire is already lit, the fuel fog burns before it ever has the chance to condense.

If I missed something - everyone feel free to edit me.

Oldwolf · #8 11-13-2009, 10:14 AM

C Sean Watts, I see you live in Raleigh too. Do you run a shop or the like for diesels?

C Sean Watts · #9 11-13-2009, 12:08 PM

Quote:

Originally Posted by Oldwolf

C Sean Watts, I see you live in Raleigh too. Do you run a shop or the like for diesels?

I do live in Raleigh. I have a cousin with the shop in Winston Salem - BUT I don't work there every day. I will be there the week of 16th to the 20th. I can work here if the need arises.

Oldwolf · #10 11-13-2009, 12:15 PM

Does your cousin balance the injectors or do you do it in Raleigh? Do you rebuild them or do you recommend new ones only?

C Sean Watts · #11 11-13-2009, 01:42 PM

Quote:

Originally Posted by Oldwolf

Does your cousin balance the injectors or do you do it in Raleigh? Do you rebuild them or do you recommend new ones only?

I do the diesel work, mostly there but I can do it in Ral. The good thing about new ones is you can not go wrong. The vast majority of old injectors I've worked on have been good but some tend to leak, especially if they have already been opened a few times. If you plan on keeping the car for a good while, new injectors are the way to go. If you might sell in a year or two, nozzles only will save you some $.

i-osprey · #12 11-13-2009, 03:17 PM

Well, the deed is done.

They're installed and everything seems to be working properly.

I can definitely tell there is more power now and the engine sounds different.

It still seems to have a bit of a miss occasionally at idle but I won't know for sure how much of an improvement the injectors are for about 200 miles or so.

It usually takes me that long for the injection system to sort itself out on this car after I have fiddled with it.

Now, I really question the value of the plastic collars around the base of the injectors.

The ones on mine were COMPLETELY degraded to the point of serving only to provide debris to fall into the prechamber.

The front three managed to contain all the sand, dirt and oil from a life on a cattle ranch provided by the previous owner in very close proximity to the prechamber opening.

I literally had to break them up as best I could and position a vacuum cleaner at the base of the injector as I removed them.

They were only a hazard for contamination of the engine as far as I can tell.

The back two were already broken off except for the part that was lower on the injector.

One of my heat shields on the back was even showing a little RUST.

Since these plastic collars were in this condition would any of you think it's reasonable to assume these are the original injectors?

I haven't tested the old ones for functionality yet.

compress ignite · #13 11-13-2009, 04:18 PM

The factory eliminated the plastic "Dirt Containment" shields years ago.

i-osprey · #14 11-13-2009, 04:54 PM

Well, they were working well enough to give me 32 MPG yesterday in about 270 miles of mostly highway. That was half with a 25 mph head wind and half with a 25 mph tail wind.

If they're original they had 233K miles on them.

i-osprey · #15 11-13-2009, 08:04 PM

OK, while the injectors are clearly much better than the ones I removed they weren't my only problem.

Here's the problem I continue to have that suggests to me that I have a timing issue.

On a cold start I still get white smoke at regular intervals.

On the old injectors the white smoke came in less definite intervals.

Now with the new injectors it comes in more dense white puffs at regular intervals.

By cold start I mean the engine has been sitting for about 1:15 on a 65F day.

I also have the rough idle once it warms up but no white smoke.

I guess I will have to check the timing chain again(I did it 25K miles ago) and delve into the mystery of IP timing.

If my timing is off enough to result in obviously incomplete combustion how am I getting the best MPG I've ever gotten since I've had the car(33K miles)?