Basic TPI Mods: by DEBBIES87
There are a few basic mods that should be done to any
TPI car, I call these "entry-level" modifications.
Cut the air box open without letting air in the engine
without going through the air filter & remove the
additional plastic piece below the air box to get more
air into the engine.
Modify the mass air sensor; remove the screens, &
and if your brave cut down the fins.
Port the plenum (upper intake). There are two small
ridges sticking up in the entry-behind the throttle
body, remove these. The throttle body openings are already
52mm, so don't go crazy when porting.
While the plenum is off for porting, it is now a good
time to get a adjustable fuel pressure regulator &
a MAT sensor relocater kit. The Adj. FPR will aid in
tuning, and the new MAT sensor will improve throttle
response as well. The new LT1 style MAT sensor is placed
in the air box instead of the plenum, this allows it
to read cooler air and advance the timing accordingly.
Advance the base timing to 12-13 degrees. Note: the
harmonic balancers on these cars tend to drift with
age, adjust timing to where the car still starts good
and doesn't detonate.
If legal in your area, gut the catalytic converter and
remove the smog pump belt (85-87), or run a shorter
serpentine belt to bypass the pump (88-92); you will
need to remove the smog pump on the 88-92's to reroute
the belt properly. Check local smog laws first.
On automatic cars, adjust T.V. cable (throttle valve
cable), so that the car shifts out between 4200-4500
RPM under wide open throttle. TPI motor power drops
off drastically after 4500-4700 RPM, they peak at about
4200-4400 RPM. No need to over-rev these motors.
Bypass fan relay to make fans come on manually, or install
aftermarket relay to turn on fans sooner.
together these mods should make the car perform like
it should have from the factory, gains should be between
.6-.9 tenths of a second from these modifications.