LDA Springs

[Baxter]

Okay.
I have a AAZ in a T3, it's running 1.5bar of boost at the moment.
The pump is at the moment stock other than a Rover boost pin.
Now, as I understand it boost pressure acts on ther LDA diaphragm, more boost = more deflection on the diaphragm as it's working against a spring.
In a GTD pump, it's failry simple to in effect alter the spring rate as thats what the star wheel adjustment does right?!
but, the AAZ pump does not have this facility.
So, I have a stock pump thats set up to accept whatever a stock AAZ boost pressure is, and probably a bit more, for arguments sake say .75 bar.
So, I should imagine that Bosch have set this pumps LDA to work through it's full stock between 0 boost and .75 bar.
With me?
0 boost = zero enrichment, full boost = full enrichment.
So, if I either shim the LDA spring, or replace the spring with a heavier one that will reduce the amount of deflection on the diaphragm and allow boost to give enrichment over a bigger boost window but I'm only getting the same amount of enrichment as I was before.
So, question is, does anyone know if I can swap my LDA spring for another spring that will give me 0 enrichment at 0 boost and full enrichment at about 1.5 bar, but then also alter the rate of enrichment to get more enrichment at the top end.
Or, is it a case of once I get the LDA to operate in the full range that I then up the fuelling as now the LDA isn't maxxed out at .75 bar and it will accept more fuel without smoking.
I darent go with anymore fuel at the moment, engine isn't trusted yet and at 65mph I'm told I have a "Haze" though EGT sits at around 700°f.

Or was that just a lot of words together that didn't make sense?!
 :lol:

[rallydiesel]

I don't know why vw changed so many things for the worse when they designed the AAZ pump. I think you will have to get a bunch of shims and trial and error it until it's the way you want.

Another thing you will want to take a look at is the decreased pin travel compared to a 1.6TD pump. Personally, I would either increase the depth on the pin recess (careful not to drill right through!) and/or grind the bottom of the pin a bit (or probably a safer way would be to take the diaphragm off and grind from the top).

With a longer pin stroke, you would have a better graduation in fuel increase with boost increase.

[blackdogvan]

My experience with the "joke" pin pump has shown the spring to be very soft in comparison with the 1.6TD or other versions with a "real" pin.  The starwheel doesn't adjust the rate of the motion of the pin, but rather just the start pressure.  It's the pre-load on the pin and so adjusts when the pin starts moving.  The spring rate itself adjust the rate of motion of the pin.  That's why I've always been on the soapbox that if someone wants to add a different pin then they should also install the spring to match it.  That way, getting the spring rate to match the angle of the pin in that nice area of efficiency and power is possible.  FWIW, the starwheel spring and rover pin can all be swapped over to the AAZ pump.  Do you still have access to the rover pump?

Andrew

Andrew, have you ever found a McMaster Carr spring that fits the bill? Say for 15-20psi?

[Baxter]

I did a pump swap on a customers van today, he had the Joke pump fitted, the one with a pretend LDA, anway, I swapped him for the ideal pump with no nonesence on it, no KSB, it has a LDA, it doesn;t have the electronic timing control and it has a cold start cable...
Anyway, we also chucked a rover boost pin in there.
While I had it in pieces I compared the wear mark on the old pin to the new pin, seems that there is a lot of travel on the pin to use, but in the wrong direction.
On the AAZ LDA there is no top adjusting screw to set the basic position of the pin, So, I'm thinking if I swap the LDA top for say a GTD one with the adjustment I can then back the screw off to allow the spring to push the pin further out, giving me more travel on the pin.
I then need to do some sums as I'm aware that there is a few different lengths of the small pin that rides on the LDA pin.
So, I need a shorter little pin to correspond to amount of extra lift on the LDA pin.
Am I boring you yet?!
Then sort a spring.
I may just dick about with a spare pump top and see if I can get a tool meade for the DTI, similar to that, that you use to set the timing so I can read the LDA pin position, then use an air line and regulator to try different pressures on it.
I wish we had a Giles in the UK where sending a pump wasn't so damned expensive.
I can now see why when you go and ask for something out of the ordinary at a Bosch Diesel shop they look at you funny and they have that blank, glazed expression as at the end of the day they just do what the test data tells them to do and nothing more!
Ask them about something a little different then start twitching...
 :lol:

[nokivasara]

Slightly off topic:
Have you ever compared a Rover pin with a Peugeot pin?
I have a Expert Van with the 1.9TD and it has a pretty steep slope on the most aggressive side of the pin. The spring is probably harder too since it has 1.0Bar of boost stock and it doesn't bottom out the pin at that level.
It also has the adjustment in the top cover of the LDA.

IŽd imagine a Pug is easier to find at the scrapper than a  diesel Rover?

[Baxter]

The reason why i like the rover pin is because I sell them, and to fit them to a AAZ there is no complex instructions needed, the pin is reasonably aggressive and it is machined totally central, so I can sell them knowing that no one has to bother messing about setting them up, it makes the whole process simpler.
The 1 bar boost sounds interesting and the spring that goes with it more so.

[bert]

my mk1 golf aaz has the rover 220TD pin fitted,im using the standard spring and its a real quick motor,112bhp and 159lb/ft torque,it will show a mk1 gti up  :wink:  and there is hardly any smoke,people who follow me comment theres no smoke for a diesel,im running a T3 garrett at 11 psi max
Bert

[allsierra123]

so you guys are installing the rover pin into the aaz pump without swapping pump tops and everything?

[bert]

yes,i just removed the crap aaz pin and put the rover pin in and instant power  :wink:
Bert

[allsierra123]

looks as if I need to get my hands on one of those.