Took the Bosio Plunge - Page 4 - PeachParts Mercedes-Benz Forum

gsxr · #46 06-28-2008, 10:14 AM

Quote:

Originally Posted by DieselAddict

But this is just not true. Have you ever seen injector lines?? You are talking about the metal pipes that go from the IP to the injectors, correct? Each one is definitely of different length.

Optical illusion. Use a string or tape measure to check each one. They're all identical length.

gsxr · #47 06-28-2008, 10:20 AM

Quote:

Originally Posted by sixto

That's an interesting point. When I took my injectors to Gus to be pop tested, I don't recall telling him nor him noting what car they belonged to. 603.97 injector bodies are unique among US MB Diesels but I wonder if there's a difference between .970 and .971 pop pressures. I also wonder if there should be a pop pressure adjustment when feeding a 3.0 with .97 injectors.

Sixto,

All USA 602/603 turbo engines with angled/inclined injection (i.e., 90-95) use the same injector body, although the nozzle changed from DN0SD265 to DN0SD314 somewhere around late 1992 or early 1993. And they all had the same spec of 135-145 bar new, min spec 130 bar for used (click here for factory PDF). If you poke around the Euro EPC a bit, you'll find the late 3.0 and 3.5 use identical injectors & nozzles. Only the pump is different, it meters a different amount of fuel.

gsxr · #48 06-28-2008, 10:23 AM

Quote:

Originally Posted by aklim

5 out of 6 ain't bad. I'm going to have to send #6 back for a check up. It is leaking. I tried taking it apart and resealing it after cleaning it but no luck

Make sure you use a new heat shield when removing & installing an injector, even if the heat shield was only installed for a short time. They are single-use items. See image below, straight from the Bosch literature.

Speaking of Bosch literature, if you have not read through the Bosch Pre-Tech course on injector reconditioning, which also shows how to properly clean, pop-test, and re-assemble injectors... click here to download the 12MB PDF file.

gsxr · #49 06-28-2008, 10:28 AM

Quote:

Originally Posted by DieselAddict

Actually now that I've thought about it some more, I believe the pop pressure affects the fuel injection rate more than anything else. The IP has no way of knowing how much fuel it's actually pumping. All it knows is how much pressure to apply at a given time and the pressure differential between the IP and the injector is what controls the flow rate. I don't think injection timing would be affected by the injectors' pop pressures in any significant way as liquid fuel is incompressible.

Another thought is that spending a lot of time balancing a set of injectors with new nozzles might be a waste of time because the pop pressures might change as the new nozzles break in. The most important thing is to get a set of good, consistent quality nozzles. That way if the pop pressures change during break-in at least they will all change by approximately the same amount.

This is not quite true. The IP knows exactly how much fuel it is pumping. The IP is what meters the fuel, not the injector. The injector simply atomizes the fuel charge delivered by the IP. Injection timing will be affected slightly by pop pressure changes, but I'm on the fence as to how much exactly... my guess is, the relative timing change is negligible if you're staying within the ~10-15 bar factory range between used and new.

Also, you are correct about pressures changing after break in. The set should be at least roughly balanced before installing, but optimally, they should be re-checked after they have broken in and seated. Fine adjustment would be done at that time. They may not all change by the same amount. Bosch recommends adjusting toward the higher end of new spec, since the pressure will drift down over time.

Diesel911 · #50 06-28-2008, 11:10 AM

Quote:

Originally Posted by DieselAddict

I still believe that's false logic. Say we were running our cars on air instead of liquid fuel. Are you saying pop pressures would make a smaller difference to injection timing? That makes no sense. Keep in mind that with air it takes much longer to go from 0 to 135 bar than with a liquid where it's almost instantaneous. Changing an instant by a small percentage is still an instant. The same isn't true when dealing with a significant amount of time.

What babymog said about the Hard Line expanding and contracting is true. In fact they actually get work hardened and stiffer over the years form expansion and contraction. So if the liquid fuel is not compressable the hard lines are expandable.
The injection at idle speed is not as instantaneous as at higher engine speeds as the plungers inside of th IP are moving slower.

TMAllison · #51 06-28-2008, 11:27 AM

Quote:

Originally Posted by DieselAddict

I still believe that's false logic. Say we were running our cars on air instead of liquid fuel. Are you saying pop pressures would make a smaller difference to injection timing?

Yours is circular logic. I'm suggesting the difference would be greater.

Its because liquid doesnt compress so easily that the moment of delivery can be relied upon so exactly.

The precise metering/delivery stystem wouldn't work using air because air's density changes so dramatically with temp, in addition to compression.

DieselAddict · #52 06-28-2008, 01:12 PM

Quote:

Originally Posted by gsxr

Optical illusion. Use a string or tape measure to check each one. They're all identical length.

Hmm, I'll have to try that the next time I have the crossover intake pipe and injector cover off. Interesting illusion.

Quote:

Originally Posted by gsxr

This is not quite true. The IP knows exactly how much fuel it is pumping. The IP is what meters the fuel, not the injector. The injector simply atomizes the fuel charge delivered by the IP.

Are you sure about that? I remember a few years ago when I was experimenting with the 240/ nozzles in my OM603 you or someone else told me that that will change my flow rate. Also this website, even though it's for TDI's, talks about how pop pressures affect metering (3rd paragraph).
http://www.myturbodiesel.com/1000q_how_to/multi/TDInozzleFAQ.htm

DieselAddict · #53 06-28-2008, 01:14 PM

Quote:

Originally Posted by TMAllison

I'm suggesting the difference would be greater.

You mean the effect of pop pressures would be even greater on the timing if we were running on a gaseous fuel, correct? If so I agree.

Quote:

Originally Posted by TMAllison

Its because liquid doesnt compress so easily that the moment of delivery can be relied upon so exactly.

The precise metering/delivery stystem wouldn't work using air because air's density changes so dramatically with temp, in addition to compression.

I agree with that.

DieselAddict · #54 06-28-2008, 01:30 PM

Quote:

Originally Posted by aklim

5 out of 6 ain't bad. I'm going to have to send #6 back for a check up. It is leaking. I tried taking it apart and resealing it after cleaning it but no luck

Be sure where it's leaking from. With my injectors I've had a lot of trouble with leaks from the intake lines (the metal pipes) at the injectors. Always inspect them while the engine is running before putting the cover back.

aklim · #55 06-28-2008, 01:44 PM

Quote:

Originally Posted by DieselAddict

Be sure where it's leaking from. With my injectors I've had a lot of trouble with leaks from the intake lines (the metal pipes) at the injectors. Always inspect them while the engine is running before putting the cover back.

I took it for a 5 mile hike and found that the rearmost injector had fuel in the hole. Cleaned it out with brake cleaner and air blasted it with a rag on top. Made sure the hole was dry and clean. Took injector out and cleaned it off with brake cleaner and made sure that the injector was torqued right. It was. Reinstalled it and ran it. Saw the part where the lower end screwed onto the upper end and it was wet with fuel. The top was bone dry.

Diesel911 · #56 06-30-2008, 02:28 PM

Quote:

Originally Posted by aklim

I took it for a 5 mile hike and found that the rearmost injector had fuel in the hole. Cleaned it out with brake cleaner and air blasted it with a rag on top. Made sure the hole was dry and clean. Took injector out and cleaned it off with brake cleaner and made sure that the injector was torqued right. It was. Reinstalled it and ran it. Saw the part where the lower end screwed onto the upper end and it was wet with fuel. The top was bone dry.

Looks like you have a leak between the injector nut and the upper body.

aklim · #57 06-30-2008, 02:31 PM

Quote:

Originally Posted by Diesel911

Looks like you have a leak between the injector nut and the upper body.

After a long drive, it seems I have 6. Will have to take it back to the shop for further investigation. Might be my fault. We shall see. I tried torquing the nut and upper body a little tighter but there is still some dampness around where the nut meets with the body.

An observation is that with the SpeedtuningUSA chip, I have a turbo whine. When it is cold and getting up to temps, I seem to have developed a 2nd lower pitched whine. It goes away when hot. I will be driving it for the next couple of days to see where it goes after it gets broken in.

Diesel911 · #58 06-30-2008, 02:40 PM

Quote:

Originally Posted by aklim

After a long drive, it seems I have 6. Will have to take it back to the shop for further investigation. Might be my fault. We shall see. I tried torquing the nut and upper body a little tighter but there is still some dampness around where the nut meets with the body.

An observation is that with the SpeedtuningUSA chip, I have a turbo whine. When it is cold and getting up to temps, I seem to have developed a 2nd lower pitched whine. It goes away when hot. I will be driving it for the next couple of days to see where it goes after it gets broken in.

When injectors are rebuilt all of the precisision surfaces inside of the injector are lapped flat. The precision fit is what seals the interior parts. If a person only changes the nozzles and dose not lap the interior parts there is a good chance of leaks between the top Injector Body and the Injector Nut. Not to mention if a particle of dirt or other foregin object gets between the surfaces (this happens sometimes even if you lap the surfaces and even if you are extremely careful).
Try this experiment sometime: Dip a clean flat piece of (preferably dark colored) steel in diesel fuel and let it drain. Lay it out uncovered in an area that you consider to be an area you would work on your injectors in. Come back in 1 hour and look at all the lint and ect. that you find sticking too it.

aklim · #59 06-30-2008, 02:53 PM

Quote:

Originally Posted by Diesel911

When injectors are rebuilt all of the precisision surfaces inside of the injector are lapped flat. The precision fit is what seals the interior parts. If a person only changes the nozzles and dose not lap the interior parts there is a good chance of leaks between the top Injector Body and the Injector Nut.

Not to mention if a particle of dirt or other foregin object gets between the surfaces (this happens sometimes even if you lap the surfaces and even if you are extremely careful).

Maybe that is what I need to do. Maybe that is something the shop can do for me.

I did the injectors one at a time. Blasted them off with brake cleaner and put them back. Contamination should be minimal.

DieselAddict · #60 06-30-2008, 03:00 PM

Quote:

Originally Posted by Diesel911

When injectors are rebuilt all of the precisision surfaces inside of the injector are lapped flat. The precision fit is what seals the interior parts. If a person only changes the nozzles and dose not lap the interior parts there is a good chance of leaks between the top Injector Body and the Injector Nut.

What do you mean by the injector nut? The nut that secures the metal line to the injector? That's the only place where I had some trouble with leaks.