MAC11B CHIP ONLY BOOST UPGRADE!

[orin@netcom.com (Orin Eman)]

I just got back from testing the latest modification to the MAC11B EPROM.
This time it appears that I have achieved around 1.8bar with the original
wastegate spring and no zener or resistor modifications to the computer!

This is using the existing solenoid to control the wastegate and it
retains all the existing safety features (except from a higher overboost
fuel pump cutoff of course :-)) ie. it only operates at WOT, doesn't
operate if the engine is too hot or there are sensor errors.

So the car is now nice and tame at freeway speeds... until you hit
the WOT switch (which is around 2/3 throttle)...

I have been relatively conservative with my programming - 1.8 bar maximum
manifold pressure with the overboost cutoff set to 1.95 bar to allow for
the wastegate control overshooting a little... I also tailed the boost
down to 1.6 bar at 6000 RPM.  The original code allows 1.41 bar from
2800 RPM upwards.

So what's the catch... I had to unsolder the EPROM.  Not my idea of fun.
If I did it again, I would clip the pins of the EPROM so I could
unsolder a pin at a time... of course this renders the original chip
useless, but they are only a few $ each.

This modification will also give a slower throttle response than using
a stiffer wastegate spring or pressure regulator on the upper chamber
of the wastegate, but for me, It's fine.

NOW, just thinking out loud here... if you do the voltage divider
modification modification to the computer to fool it into thinking that the
manifold pressure is less than it really is, then that 1.41 bar max would be
increased accordingly as the computer would try to control
the wastegate to get what IT thinks is 1.41 bar...  Something else
to try!

Thanks to Robert Houk for providing the disassembler and MAC02 disassembly
and to Scott Mockry for his insights into the ROM code.

Orin.