1.6N/A compatable with LDA pump?

[bryanbryan89x]

Well I just acquired a pump and it has a lda on it.  Can I put this into my n/a? What are the side effects.  I did a search, and I could only find people doing it the other way around.

[fspGTD]

I would not slap any old pump that has an LDA onto your VW.

What is the LDA pump from, a VW 1.6lTD?  You got an application or part number?

A stock 1.6lTD pump will run on a 1.6lNA motor, but will not give optimal performance.  The TD pump comes with a lower revv limit and also a slightly lower peak fueling output when there is no pressure applied to the LDA compared to a 1.6lNA pump.

You can adjust the fueling pretty easily by screwing in a fraction of a turn (counter clockwise) the full load screw, but I'd recommend keeping notes on what adjustments are made so you can revert to stock specs if you ever find the need to.

I would time the pump using whatever specs were called for it on the model it came from (for example, '83-'84 1.6lTD is 1.00mm advance.)

[bryanbryan89x]

Sorry for not being very specific I bought this pump...
http://vwdiesel.net/phpBB/viewtopic.php?t=2988

I wanted to do the governor mod, and have a good pump to back me up.

[hillfolk'r]

it should probably be fine,,itll run ok,,,throw 'er on there+git 'er done :shock:

[fspGTD]

Bryanbryan89x: your VW atmospheric compensator pump relies on some additional gizmo in the engine compartment to get low-altitude enrichment.  This gizmo is originally mounted to the fuel filter mounting bracket and it's purpose is to control a vacuum signal that gets to the bottom of your pump's diaphgram.  Here is a related thread that unfortunately no longer has a valid picture:
http://www.vwdiesel.net/phpBB/viewtopic.php?t=1421

Edit - found on rackley's site a valid picture of the atmospheric controller gizmo:


Also, you might be able to convert your pump to a boost pressure activated LDA by swapping the atmospheric vent fitting from the top chamber of the diaphgram onto the bottom chamber, and by then applying boost pressure to the top.  By 14-15 psi boost pressure on the top, I would expect the pump would be completely "fooled" into thinking it was operating under maximum possible density atmospheric pressure conditions.  With no pressure differential across the diaphgram, I believe the pump would be in a "least fuel for thinnest air / highest altitude" mode.  Hope this info helps!

[bryanbryan89x]

Thanks Jake!!!

I'll see what i can do and report my results

[bryanbryan89x]

So what do you suggest?? use a little c3h8 for that 14-psi??  I really want to use the atmospheric compensator pump because on the govener assembly I could fit 3 washers to take up the intermediate spring travel.  Where as on my non-lda pump it was only 2 washers.  Also the lda pump has 150 000 less miles on it.  I think the propane fumigation would work good in this case?

[fspGTD]

Converting the pump to boost-pressure fuel enrichment may be useful in your case I was thinking if you later wanted to upgrade to a turbo.

For NA use, you could just run it as is without atmospheric compensation.  It would be in high altitude fuel restrictive mode though.  It could be adjusted to think it was in a lower altitude (to give it more fueling) by either by screwing the travel stop screw at the top of the "LDA" down (maybe replacing it with a longer bolt if more travel is needed), or by applying vacuum underneath the diaphgram (and you could vary the amount of vacuum to control the amount of fuel enrichment.)

There is always the smoke screw adjustment if you should need yet another way of getting more fueling, although you'll have to adjust your idle screw afterwards.  Whatever method yo use of tuning it, for a street application I would recommend setting it so it runs just on the verge of smoking.  And keeping track of how to revert the pump setting back to OEM specs (write it down somewhere) is always a good thing.

As yet another option, you could try and get the OEM atmospheric compensation back up and working, but you'd need to track down one of those gizmos.