[Vwdiesel] More Quantum Questions?

[mark shepherd]

Hi Bill.
What year is your Bentley? If it is later than 1985, then I might need your 
help with a couple of a/c pages!

Back to your issue...
1) You don't need to lap the injectors as a matter of course, in fact it may 
lead to more issues than you had.

2) Only lap the body , if you find the injector leaking after initial 
reassembly.

3) The aim of the game is to match 4 injectors as best as possible.
Matching  means similar break pressure. Spec is 5bar, but connaseours like 
to get closer. The reason for this is that differing break pressure changes 
injection timing for that cylinder leading to lumpiness.
Compare this to a worn spark distributer shaft.]

4) Matching, also means similar leak off quantities [original Bosch nozzles 
made in Germany of France have virtually no leak off and are the best if 
still in good operational condition.]

5) Higher break pressures lead to finer atomisation. Read up on 'Harry 
Ricardo' the main designer/researcher into IDI engines in the early 1900's 
to understand that too fine a spray can be counter productive. { Energy 
wasted in higher compressions and lack of momentum of droplets}.

6) A good spray pattern with no squirting is desired, unless of course the 
nozzle has a presquirt facility.
Fast pumping of the tester is best to simulate engine/pump speed. Sustained 
pressure holding with no drips is another essential test to prevent burning 
fuel at other times other than the power stroke, creating a smoky exhaust.

7) Contrary to public oppinion, the shims to adjust the break pressures do 
not have to be the holed special washers. Additional thin shims can be added 
by using pieces of cheap tape measure spring.
These pieces give about 5 bar increase.
Heating and hammering can naturally give you further shim sizes. If anyone 
doubts this line of thought then look up my mini thesis on one of the diesel 
fora.

8) Lapping the body to increase the bars, can create leakages you didn't 
have before.

9) Do not over tighten the injector body as this can cause warping of the 
nozzle body, and binding of the needle.

10) Regrinding of the nozzle can be done, but you either need to do hardly 
any flesh removal, or, for best results, grind nozzle, and needle seats to a 
slightly differing angle.

Regards
Mark


----- Original Message ----- 
From: "William J Toensing" <toensing at wildblue.net>
To: <vwdiesel at vwfans.com>
Sent: Tuesday, July 06, 2010 6:13 AM
Subject: [Vwdiesel] More Quantum Questions?


>
> I want to thank Loren Baird for the referral to www.vincewaldon.com how to 
> do it. The video was especially helpful as it showed the injectors popping 
> off & the proper spray pattern. I found that the #1 injector had to be 
> taken apart & the "spacer of intermediate disk" needed lapping , 
> especially the side that had two groves, like the picture showed. My 
> question, do they have to be lapped until none of the groves show? I had 
> to use #400 to get the groves out . On the number 2 injector I did not get 
> the groves totally out but both # 1& # 2 are popping off at 2200 psi with 
> numbers 3 & 4 popping off at 2000 psi. On page 23.14 of the Bentley 
> Quantum manual indicates 155 bar to 163 bar or 2204 to 2308 psi is 
> acceptable plus a wear limit down to 140 bar or 1991 psi is acceptable, so 
> I guess my injectors are with in the low & high limits. Would like to have 
> comments re this before installing the rebuild IP.
> One little tip that might be useful. If you have an extra Bentley as I did 
> which was rolled up, were stained, & almost un usable. I cut each page 
> from the binding & inserted each page into a plastic holder, which you can 
> get at Staples or some other office supply house. Now, instead of taking 
> the manual out to the garage & getting it all greasy, I just make a copy 
> of it with my computer printer & take it out to the garage.
> Bill Toensing, Nevada City, CA
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