Have a good read of -
http://www.lcool.org/technical/80_series/1hdft_pump_adj.html
I carried out these mods a couple of months ago. I followed the order
laid out in the article. I found that the most significant factor in
alteration of performance was definitely the boost compensator
profile,ie the "load" you put on the diaphragm.
I have to confess that I made a mistake when doing the mods - after
removing the four allen screws from the top of the compensator housing I
eased it upwards, at this point I should have stopped, and I removed it
from the pump. I heard a metallic click and thought - oh fffffffffff
!!!!!!!!!!! However, every cloud has a silver lining as it enabled me to
see how the boost compensator pin is profiled and thus enabled me to
orientate it for the optimum setting. In my case - '97 24 valve model -
with TPS , the pin has an offset profile ground approx half way along
its length. Rotating the pin moves the position of the profile with
respect to the spring and it is this which affects the pre load and
hence the tension discussed in the article. In my case I moved mine a
quarter turn. With the cover, diaphragm and pin removed you can see the
toothed wheel and detent spring, I turned the pin by three clicks.
With regard to the off boost adjustment I had an advantage with the pin
etc removed as I could see that the range of adjustment was in fact over
a range of half a turn. What affects this is a wedge like profile that
the adjustment screw ( the one with the yellow paint ) abuts on. The
more the screw goes in the further the pin goes in the more the fuel
etc. Now if you look at the upper surface of the wedge you will see a
witness mark where the screw contacts it. Back off the screw and rotate
the pin so the wedge presents its highest point to contact the screw.
Now you wind the screw in and road test so that you are happy , I found
that I could wind in the screw in steps of half a turn then road test
each time.
Leave plenty of time to do the mods , do one at a time, and road /
smoke test after each adjustment. Follow the steps in the article, dont
despair if the pin comes out - with a bit wiggling it went back in again
!! I had also thought about the "washer" mod to add further pre load -
thats next along with,
fitting my Walbro pump and gauges .
If you want a very cheap mod that allows the turbo to spool up faster -
remove the central silencer and replace with a plain pipe. It won't be
any noisier, and the reduced backpressure allows the engine to rev
better- trust me, I've done it. Next step 3 inch exhaust.
Sorry about the length of post !!
Regards Gareth Jones '97 1-HDFT S.Wales.
