IP Timing: differences between slow-drop and fast-drop?
 

I got down the procedure for setting the IP timing via the drip tube method and I feel
now confident enough about it to do it as my next project in the very near future.

There is something I haven't been able to understand yet though...

What is the difference in procedure for doing the 1 drop/sec and the 1 drop/20 secs? With my engine (240D, 616), I will be setting it at BTDC 24 degrees. I have learned the procedure from a tutorial that suggests setting the IP at 1 drop every 20 seconds. What I want to know is, how does the basic procedure vary from what I'll be doing when setting it using 1 drop per second?

The factory service manual states to use 1 drop/sec.

IP Timing
 

You will not be able to tell any difference between the two....You can vary the drip count by changing the pressure of hand pumping or even the temperature of the fuel can vary the count...both are so close that either will do..... Lots of information and heated debate on this topic...I could not tell the difference from 22 btdc up to about 27 btdc (performance wise)....on my 240D and 300D......But like the very experienced previous post said....If you set it by the book.... you can say that it is set to spec and be comfortable with that fact....
Mine seemed to get the most power at about 26 btdc....and that is what it peaked out at using the millivolt glowplug method...
Mine would start and run anywhere from 18 degrees all the way up to 28 degrees...the sweet spot seemed at about 26....both cars...

26 is what I set mine to. Runs better now than it ever has in my ownership.

IP timing
 

Wish I had EGT sensors in each cylinder output port and a way of measuring the exhaust HC content...would be nice to peak it up for best burn....Also would like to know how well the IP advance mechanism is keeping up with the increase in RPM's..those advance springs must age some over time....

Hi Yellit, I did drop an email to metric motors asking if they replaced the springs with each total engine rebuild. Or if they just checked them or the fuctional overall advance of the timing wheel units. They did not respond back. I too felt the springs might age as well to some extent.
Since I have not critically examined a timing wheel I am unable to say if that senario would bring on the advance earlier or later if the springs where weak. We should perhaps have a better understanding of the aging charactaristics if any as the units are getting quite old now.

you do have EGT sensors in each cylinder... sort of.
the Glow plugs will give you an indication of temp by varying millivolt readings. the higher the reading, the hotter the temp.
to get similar results accross the block, all GP's would have to be new.
have fun@!
John

I still don't understand... You are saying that the procedure used for both drip counts is precisely the same and that you just vary the drip count by changing the pressure of hand pumping? I thought that one needed to be very meticulous, operating careful adjustments by rotating the IP, in order to arrive at a precise drip count...
How is it possible that, following exactly the same procedure for both, the two drip counts are interchangeable without varying anything else? I don't get it... Can someone help me understand this concept, please?

The reality is that the flow goes from "all to nothing" very quickly as the IP is adjusted (rotated.) From a practical standpoint, the timing will be very close to correct if the IP is dripping (ie: forming droplets) at any rate.

It will make a lot more sense when see it for yourself.

If what you are saying were true, then what's the point about rotating the IP by small increases until getting exactly to a given precise count, which is very much an important step in all the tutorials on IP timing I've read so far? One would just set the degree number on the balancer (with cams in the proper position) and move the IP until getting ANY count... However, there are very distinct rates for doing this: 1 drop/sec, 1 drop every 20 secs, etc. I doubt that your answer is it...
Will someone with some solid technical (as opposed to practical) background step in and clarify this for all of us, please...

Drips
 

What you are seeing is the #1 IP plunger closing the fill port of the injector barrel....the drips are indication of the very threshhold of beginning of pressurization in the fuel element .....The drips are an indication that the fill port is almost completely sealed by the upward travel of the plunger...As the fill port is blocked by the upward moving plunger...no more drips...
In actual operation the only escape for the now pressurized tiny column of fuel is out of the IP fuel line to the injector...
One forum member uses a bucket suspended above the engine full of diesel to maintain a constant pressure to the IP fuel chamber to get the drip count the same every time.....that is how I am going to do it from now on...
Hand pumping is too variable for a constant pressure....
If you have studied this stuff like it looks like you have...you are going to be extremely close to what spec calls for....once you do it it will make more sense....

I appreciate all the stuff you have written, but it still does not address my specific question. For instance...

Let's suppose that, using your strategy, we use a bucket suspended above the engine full of diesel to maintain a constant pressure to the IP fuel chamber to get the drip count the same every time... (thereby eliminating the variability inherent in hand pumping which makes it an unreliable procedure): are at this point the two drip rates (1 drop/sec and 1 drop every 20 seconds) still interchangeable?!? How is it possible that they be so? It doesn't make any sense at all...

Drips
 

I got this information from an authorized Bosch IP service shop owner with about 30 years of experience....there may be some more qualified people for this topic... but I have been ok with the info from Bosch Injection service professionals...
I think the procedure may be over emphasized in shop manuals just to get as close to port threshold closure as possible since this is mostly a field procedure with simple tools...The original procedure was the high pressure test method which involves a lot of expensive Bosch test equipment...
If you want to be dead on timing specs. then an electronic timing device can be used to check dynamic timing with engine running...I also like to be as close as possible to spec. so I understand the need for good info....
You may be surprised when the drip count is where it is supposed to be.. but when put on a dynamic timing device it shows to be off a bit...In these cases I would go with the dynamic test results...

Drips
 

The flange IP setting for 1 drip every 20 secs or 1 drip every sec is probably so close to actual IP adjustment.... that whenyou tighten down the IP it may vary that much anyway....
Try both drip counts if you want to see if it does much...
You could call several Bosch shops and see what they say....
I thought I was the only one that worries about this stuff and cannot sleep for thinking about it....but that is a good thing when it comes to our oil motors...

Don't get me wrong... As I said in my first post, I got the procedure down and feel confident about going ahead and doing it...
My question is a conceptual one... It's not at all about getting as precise as possible in the timing... It's just about understanding how it is possible that, using exactly the same procedure, two different drip rates of measurement are interchangeable within that same procedure... Understand what I am saying?
I would like to comprehend how utilizing the 1 drop/sec method is interchangeable to using the 1 drop/20 secs method, because it seems absolutely illogical to me... I think maybe something is escaping me, and would like to understand what that is...