Hey guys guess what! I was fumbling around in the shop and I found my machined timing cover!
Someone put it where I didn't expect it, I guess I never dropped it off at the aluminum anodizers after all!
OK - time to revive this thread yet again! I made some more progress assessing the viability of the machined timing advance cover, and things are looking good.
Before installing the '84 1.6lTD injection pump on dad's Rabbit 1.6lD, I took the opportunity to remove its timing advance cover and cold-start advance lever covers, and I took some piston travel measurements. Pushing on the back side of the piston to see how far out it would go, I found that by the time something inside the pump stopped it moving out, it reached a protrusion beyond the face of the cover of about 5mm! This means that the piston of the '84 1.6lTD pump in my Rabbit GTD autocrosser should be able to move freely out at high RPMs up to the full 3mm depth I had machined into the cover, with no internal pump modifications necessary to achieve the additional timing piston travel.
I also verified that the depth of the spring perch of the machined cover I have (which actually came from a mitsubishi pickup truck) matches the cover out of the '84 1.6lTD, and the spring perch looked functionally equivalent. So I should be able to bolt this thing right on and expect it to not mess up the enitre dynamic timing curve (at least not a whole lot.)
By the way, going from memory here, IIRC the full travel of the stock timing piston was about 7mm. And also IIRC, moiving the cold start advance lever moves the piston out by about 2mm. (All figures are accurate to only about .5mm, due to crappy inaccurate plastic measuring calipers I badly need to replace! :? ) This basically confirms that a 3mm increase in the travel of the timing advance piston is a significant amount - an increase of about 43%!
Also can take away from this, that if pulling the timing out is good for a 2000RPM change in dynamic timing, at 2mm change in timing piston, that would mean adding 3mm to the end if its travel would add an additional 3000RPM to revv before the mechanism reaches it's limit.
I know a lot of you guys have been anxiously awaiting to hear the results. So now, if I just could get the GTD motor starting reliably (and finish up other projects like dad's Rabbit turbo conversion :?), so I could move on to testing this.
My 1.9pump started to leak on the ingoing shaft for the throttle mechanism I started to get my GTD pump project going..
The idling spring was m,issing when I first opened the pump so I canibalised my 1.6NA pump for the little spring, then I noticed that the both springs are thicker and stiffer than the one on the GTD pump:
Upper one is the stock 1.6 GTD
I swapped the partload spring and added a washer:
Total increased length is about 2.5mm.
ps. I just noticed that the fullload spring is stiffer too.. gonna swap that one too I think
does anyone know if the governor weights are different from pump model to pump model? It would seem that a lighter governor weights would increase the powerband of the pump
interresting photo:
on the right peugeot and vw gtd 80cv on the left.....
This is what I did to the governor on my car when I had it apart:
It now revs past 5000 rpm although it is past it's torque peak by then. Between this and the 10mm pump head (for now) There was quite a difference.
those are some great pics...are there any boost problems with the removed intermediate spring...as far as binding with the aneroid pushing down once the turbo is on boost? I have a fiat 11mm pump and it definitely needs the governor modded...power starts to cut out at approx 3500rpm
Everything has been just fine since I got the pump adjusted properly. This took me several test drives and a little fine tuning over a couple of days of driving. I haven't played with the timing anymore, but it is at 1.2mm as that is what it took to get it to run properly with the 10mm pump head. I think this is an area where 'more is better' will probably be detremental. The springs do more than just determine where fuel becomes limited. They also smooth the operation of the engine and the transition between on and off throttle. The short of it is that you should probably only shim to get the cut-off to where you want it. Anything more will likely compromise some driveability.
As for the LDA - I had to readjust that because it would smoke really bad off boost. I can't say I've run into any issues with it binding. There is still plenty of travel in the governor assembly though
The first time i took it for a drive I turned out onto a main road and stood on it because there was a Cadillac coming. I looked in my rear view mirror to see a black cloud covering the lane behind me and drifting off toward the right lane and the median. The Cadillac quickly changed lanes.
This was also partly due to the timing. Smoke diminished a bit when I advanced the timing. .