Wastegate mods

[QSHIPQ@aol.com]

Jay, Phil and RDH:

I'm with RDH on this idea.  Jay, a couple of things to consider.  If you are
using a Mac -02 box, this is probably an ok mod, though a stiffer WG spring
could do the same thing for simpler dollars.  Mac 11> boxes, this isn't the
best of mods.  Why?  Well, if you run a regulator in place of the freq valve,
you really take out some of the safety features of the freq valve itself.  The
freq valve adds boost in the same manner as your "mod", however, since it is
computer controlled based on sensor input, the FV will not add boost if the
water temp is too high for example (or knock or charge air temp).  Regardless,
unless you ground the FPR you will only get the maximum boost that the
computer allows.  On a MAC-11 that would be 1.4 bar (computer dash read) and
you will get a massive shutdown at 1.5bar.  For that small gain in boost, a
stiffer effective WG spring (spring or shim the stocker) is just as good, or
better mod.  If you did ground out the FPR you have no overboost protection at
all.  What does that mean?  Well, what happens if your lower wg feed hose
goes?  Or, your WG diaphram blows out?  Unlimited boost, until boom.  Bummer.

If all you are doing is playing within the parameters of the computer boost
(1.5bar - MAC 11) this mod is fine, though you could shim the WG cheaper.  If
you are playing with the overboost cutoff, I'd procede with extreme caution.  

Bottom line, watch those mods carefully.  This list has cracked the MAC codes
(thanks mostly to the efforts started by RDH himself), and many have figured
out how to raise the internal overboost safely, and using the stock FV to add
boost.  A 2 bar pressure transducer can regulate boost to 2 bar (and for a
stock k26 this is all you need), and 2.5 and 3.0 bar PT's are available.  For
the early cars the valve gives in car adjustability, and is probably as good
as the WG spring mod.  For the FV cars, you are taking a step back in
protection, there are better ways to skin that cat.

My .02

Scott Justusson