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  #16  
Old 04-13-2008, 02:18 AM
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Quote:
Originally Posted by dawsonj3 View Post
Tip for finding correct thickness of shims needed (with less trial and error):

Take the existing shim(s) out of the injector, re assemble, and then pop test the injector. Record the reading ( it will vary by injector). This allows you to know the baseline pop pressure created by the spring itself. Then, you can simply do the math to determine the correct thickness to get you desired pop pressure. My 2 cents.
I do some what of the same but I keep all the original parts together. This usually gets you in the Ball Park. Unfortunately each injector has separate base line from the others. A size X shim that will raise one injector 100psi will raise another only 50psi.
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  #17  
Old 04-13-2008, 11:19 AM
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I am presently using (this is the name of the product) Shim In A Can, 6'x100"x.002" thick. Made by Shop-Aid Inc.
When ever possible you should use Tempered or (Don' laugh) Full Hard shim.
Before I bought this shim stock I had been using .002" stainless steel tool wrap that is used to wrap tools during heat treating. This material is softer than the shim stock I bought. When I rebuilt my injectors I removed the tool wrap shims and replaced them with the new shim stock. The tool wrap shims looked OK even after 1years use.
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  #18  
Old 04-14-2008, 09:51 AM
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Quote:
Originally Posted by C Sean Watts View Post
going on a year now. $0.89 each and I've always varied the set number according to what you need.
I ran across your name during my searches but could not tell if you were still selling the springs/shims/nozzles. Now I and others know

Another question. How often does the spring in the injector break?

Richard
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  #19  
Old 04-14-2008, 10:25 AM
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Not too often

Quote:
Originally Posted by BlueTank View Post
I ran across your name during my searches but could not tell if you were still selling the springs/shims/nozzles. Now I and others know

Another question. How often does the spring in the injector break?

Richard

It seems they tend to fatigue and not return to full unloaded length. Some I've seen were pitted and/or rusty (from water, etc.) In those cases, I don't even bother measuring, I just replace them. I know some who 'know better than engineers' will say that's a waste of $5.00, with tongue firmly in cheek, I'm sticking with the engineers on this one.
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  #20  
Old 09-26-2011, 05:57 PM
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The ratio of shim thickness to change in release pressure is governed by the K value of the spring so it is independent of the ground state pressure of the injector without shims.

The spring K value (ratio of change of spring force : change of spring compression distance) will only change very slightly with age (unless corroded or severely overheated) so the ratio will stay essentially constant, provided springs look OK on inspection.
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  #21  
Old 09-26-2011, 07:49 PM
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Quote:
Originally Posted by paddo View Post
The ratio of shim thickness to change in release pressure is governed by the K value of the spring so it is independent of the ground state pressure of the injector without shims.

The spring K value (ratio of change of spring force : change of spring compression distance) will only change very slightly with age (unless corroded or severely overheated) so the ratio will stay essentially constant, provided springs look OK on inspection.

I am not sure what is going on in the above paragraphs.
Even if the length of the Spring does not change over time the strength of the individual springs decreases and the strength varies from Spring to Spring even if they are compressed to the same length they will all have different pressures.

That happens even with new Springs but the difference will not be as much from new Spring to new Spring.

This means that after the cleaning and lapping and clearing again of the parts you assemble the Injectors. You Pop Test them and you write down the pop/opening pressures of them.

Pick an Injector and decide what pop/opening pressure you want to achieve and use the formula in the Manual to estimate the change in Shim thickness you want.

Take the Injector apart and replace the shim/s with the size you estimated.

You assemble an Injector with that Shim (write down how much of a Shim Thickness you changed). You Pop Test it again.
If it came out OK you are done. But, most often it is still going to be off.
But, now you can take the original pop pressure and your new pop pressure and the amount of Shim Thickness you changed and a make yourself a formula as to how much pressure change you got per thickness of shim change.

You rummage through your selection of Shims and try to find one with the thickness you calculated.

You take the Injector apart again and change the Shim/s thickness and repeat the process until you get the pop pressure you want or you give up and decide that will have to be close enough.
Then you move on to the next Injector and repeat.
It seams like there is always one Injector that you will not have the exact sized shim you want.

In a Fuel Injection Shop they will charge you at least 1/2 hour of their labor rate per Injector.
I person who is used to doing the job and has all the tools and equipment he needs and is doing a whole set of Injectors can do the completed rebuild 10-15 minutes per Injector.
(And they will try to balance them as close as they can without spending too much time on the set.)
Also if you have a lot of Injectors you can cut the time even more because it is easier to find a balanced set from a large selection of Injectors and the cleaning and lapping process moves faster per Injector.

It takes less time then that to do direct Injection Injectors that do not adjust the pressure with shims because there is an adjusting screw for that.
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  #22  
Old 09-26-2011, 07:58 PM
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Quote:
Originally Posted by paddo View Post
The ratio of shim thickness to change in release pressure is governed by the K value of the spring so it is independent of the ground state pressure of the injector without shims.
That's a good thing, because the "ground state pressure" without a shim is usually zero.

What a relief!!!
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  #23  
Old 09-27-2011, 11:44 AM
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Can shims be stacked

Or can only single shims be used? I'm coming from the 'single shim' camp, but with a limited supply of shims, I've wondered about the ability to stack 2 to get a closer balance.
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  #24  
Old 09-27-2011, 01:46 PM
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Quote:
Originally Posted by wildest View Post
Or can only single shims be used? I'm coming from the 'single shim' camp, but with a limited supply of shims, I've wondered about the ability to stack 2 to get a closer balance.
It does not matter if one or more Shims are used; with the exception that the Shim that goes against the Spring should be the thickest one and made of steel.

When I worked in a Fuel Injection Shop I would sometimes get Injectors that someone had installed Brass Shims made from generic Shim Stock (they also had 1 or more Steel Shims in the stack).

There was no problem apparent from using them as long as they are not directly against the Spring.

Also for the Mercedes Injector application the Shims do not have to have the hole in the Center. You can put shims with no hole against the upper Injector Body.

What was nice while they lasted is my Boss got in a Box of Thin Diesel Kiki Injector Shims for a special job we did. The thin shims made it easy to bump up the opening/pop pressure. After that box was finished He never ordered any more.
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  #25  
Old 09-27-2011, 05:14 PM
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I have a pop tester and have done 3 sets of injectors so far (1 Mercedes and 2 VW's) . I always pop the injectors with the old nozzles first. All 3 sets were closely matched in pop pressures (within each set) and they all have only one shim in each injector. The new nozzles that were put in the 3 sets of injectors did not require any additional shims- they were all within spec with the original shim. Maybe I was just lucky that the nozzles I got were closely matched? Two sets were Monarks and one set was Bosch.
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  #26  
Old 09-25-2012, 09:19 PM
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How come the shims don't need a hole in the middle? I am looking at the FSM diagram and it looks like the fuel goes directly through the middle until it reaches the nozzle insert/spacer (the last thing before the nozzle).

I have a second set of injectors laying around to get shims from. Could I also experiment with swapping the springs as well? Perhaps doing a baseline test of the springs by themselves (from a set of 10) - and then pick the 5 that are closest together?

In fact I have 15, as I have two running cars and a parts car - so I could just rearrange to match in sets of 5, I'm assuming - or is there a problem with mixing injector manufacturers (as long as the internal parts are not swapped)?

Are the OEM shims (from original injectors) different in size, or are they all the standard thickness? (ie does it make a difference to swap with other OEM injector shims)

As per manufacturing my own shims, if the shims don't need holes, wouldn't material from a feeler gauge work as well (if cut to size/shape, but left a solid shape, ie NO drill hole through the middle)?

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  #27  
Old 09-25-2012, 09:40 PM
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Quote:
Originally Posted by tomas_maly View Post
How come the shims don't need a hole in the middle? I am looking at the FSM diagram and it looks like the fuel goes directly through the middle until it reaches the nozzle insert/spacer (the last thing before the nozzle).
The fuel is routed through a bore in the wall of the upper injector half. The FSM drawing is potentially misleading in that regard. Return fuel is the only fuel that sees the center cavity.

Quote:
Originally Posted by tomas_maly View Post
Are the OEM shims (from original injectors) different in size, or are they all the standard thickness?
There is no "standard" shim thickness. They are fitted "as required" to attain the desired pop pressure.
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  #28  
Old 09-26-2012, 10:06 AM
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For what its worth, The shims in chevy 6.2 diesels use bosch nozzles and the shims are the same as used in mb's (& vee dub diesels also I think) -corne-
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  #29  
Old 09-26-2012, 10:55 AM
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Quote:
Originally Posted by tomas_maly View Post
How come the shims don't need a hole in the middle? I am looking at the FSM diagram and it looks like the fuel goes directly through the middle until it reaches the nozzle insert/spacer (the last thing before the nozzle).

I have a second set of injectors laying around to get shims from. Could I also experiment with swapping the springs as well? Perhaps doing a baseline test of the springs by themselves (from a set of 10) - and then pick the 5 that are closest together?

In fact I have 15, as I have two running cars and a parts car - so I could just rearrange to match in sets of 5, I'm assuming - or is there a problem with mixing injector manufacturers (as long as the internal parts are not swapped)?

Are the OEM shims (from original injectors) different in size, or are they all the standard thickness? (ie does it make a difference to swap with other OEM injector shims)

As per manufacturing my own shims, if the shims don't need holes, wouldn't material from a feeler gauge work as well (if cut to size/shape, but left a solid shape, ie NO drill hole through the middle)?

The other Member covered that the actual pressure goes through holes coming down the side of the Injector.
I wanted to say that these same Shims are used on other Bosch Injectors that use Shims; on some of those Injectors the have to have the Hole in them because the return Fuel goes through the center of the Shims.

Swapping any of these items in the Pic 3, 4, 6 ,7 ,8 ,10 and the Nozzle itself can all alter the Pop Pressure.

However, when swapping parts make sure all of you Injectors have the same Bodies and Nut. There is 2 types of Injector bodies out there and the parts are not supposed to be inerchanged between the 2 types.

The Shims come in about 5 stock sizes.

I have seen Injectors come into the Shop I used to work in with cut up Feeler Gauge pieces and also Brass Shim Stock. As I menioned before you don't want the Spring up against anthing but a hardened Steel Shim.
However, I think Brass Shim stock is the softest material I would use.
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  #30  
Old 09-26-2012, 11:33 AM
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Quote:
Originally Posted by Diesel911 View Post
The Shims come in about 5 stock sizes.
I haven't counted, but there are way more sizes than that.
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