Eccentric grind on GTD boost pin - normal?

[Tintin]

I forgot to mention, the majority of the boost pin spring are fully compressed at 5-8PSI, if you plan to run at 20psi of boost, that need a very strong spring, I bought mine in a store which sells hydraulics parts.

[Vincent Waldon]

nice response mate.

Binning the nylon shim is reversible, but in my mind would be more about tuning for economy, since you are effectively lifting the plunger into an ever leaner part of the fuel map.

Not so, surely? binning the nylon shim will allow the pin to travel further thus increasing the amount of fuel?  

We are probably talking about different things... I was assuming you meant "shim" as the plastic nylon washer the cone  is sometimes mounted on, but in looking at the picture again it looks like you have a nylon spacer that wraps around the cone... which is probably what you mean by "shim".

If so then yes... if that nylon spacer is in fact a hard stop for the pin  removing it will certainly let the plunger depress further... yielding more fuel.  And, to Tintin's comments, the more travel the better so that you can map the fuel to boost in a more granular fashion.

[Tintin]

Caution if you remove completely the nylon spacer, the pin will strike the feeler finger.

Unscrew the diaphragm and insert the pin in the hole, apllies full throttle and you will see the maximum of depth which the pin can go, and put the proper spacer.

If the pin goes down deeper than the edge of the metal pieces where the star wheel is screwed, these piece It's adjustable in depth, but that need to completely dissasemble the top of the pump.

[jtanguay]

this is why i let the pro's deal with my pump...   :wink:  lots of trial and error trying to get everything rigged up.

a test bench would quickly get this setup properly with the right amount of fueling per boost.

[Slave2School]

I concur!   :lol:

[regcheeseman]

I stripped my other GTD down and it also has factory 'correct settings'

the boost pin is this time rotated to minimum but the starwheel has about 4.5 mm less preload.

and I got my calipers out on the nylon spacer depth stop thingy and would you believe it, it is set right on the limit of travel. Any material removed would see the boost pin rammed into the fuel pin.

However, you could make a custom pin with a longer taper.......... :wink: or as suggested fit a heavier spring. However, this would require a different angle of taper.

I'm of for a test spin in a bit, neighbours wouldn't have appreciated taking it for a spin when I finished the work at 1am this morning.

[hillfolk'r]

heres my custom pin
i got a few laying around if i wanna go stock
heres the "stock" setting

heres "lots o fuel setting"

 be sure to polish the section you ground down so it travels smooth
thats about the thinnest i wanna go without breaking it

[regcheeseman]

There ain't much meat left on that - which was I was thinking of a custom pin.

You could grind a radical taper on one side and keep plenty of meat for strength - no reason to have a conical shape.

[hillfolk'r]

that is a taper,,its not rounded at all where it rides in the max fuel position
i just ground across it flat with a dremel cut off wheel on the stock max fuel side and added more ramp to it ,then polished it up
i kept the "lean fuel" setting stock on the other side,so i could do a quick roadside adjustment if need be
rabbittrees fuel pin is so thin,you could probably break it with your hands :shock:

[regcheeseman]

rabbittrees fuel pin is so thin,you could probably break it with your hands

that bit worries me! if you had a custom pin and wanted a get you home lean setting - just pull the LDA hose off or stay off the loud pedal.

My fiddling last night now mean the EGT works, before it wasn't even registering - scale starts at 600F

gone is my off boost hiccup and it's spinning the wheels up everywhere.

[regcheeseman]

I see what you are saying, surely the boost pin is dependent on boost whereas the max fuel screw is relative to throttle position.