The Russian pages say it's from the 7A-FE (4A got them too). So try 93-97 Corolla or 93-99 Celica.
I'm still searching but found this:
http://carprogrammer.com/Z28/PCM/SAE/2000-01-0932.pdfNeat highlites:
The SPB pressure sensor operates in a structural load path that is
very linear and well behaved. Cylinder pressure acting on
the combustion chamber creates a force that is elastically
transferred through the cylinder head structure to the
head bolts. A portion of this total force is transferred in
compression through the spark plug boss and has a
magnitude of about 2200 N at maximum cylinder
pressure (6.8 MPa). This provides a reasonable but not
excessive force for sensing. To detect the force, a
shoulder is machined on the inner diameter of the spark
plug boss and the sensor is preloaded onto the shoulder
using fastening threads. To accommodate the sensor, the
cast outer diameter of the upper spark plug boss is
increased about 6 mm. Because the sensor is located
high within the spark plug boss, the sensor has no
detrimental effect on spark plug cooling. The sensor is
responsive to compressive forces applied through the
sensor bottom face (see Figure 3).
A detailed thermal-structural analysis for the sensor and
cylinder head was performed to confirm load path
sensitivity to cylinder pressure and insensitivity to
extraneous loads (Figure 4). Various extraneous loads
are known (valve train dynamics, thermal loads, etc),
however, since loads caused by cylinder pressure are
large, tests show that error signals could be effectively
isolated and minimized (see section on signal validation).
Frequency response of the installed sensor is about 20
kHz, which is adequate for detection of cylinder pressure
including combustion knock.
The advantages of this overall sensing concept are:
1. Direct access to the combustion chamber is not
required
2. Due to abundance of cooling water surrounding the
spark plug boss, sensor operating temperatures and
hot soak temperatures are relatively low (140 C
maximum).
3. Due to mounting outside of the combustion chamber,
the sensor is insensitive to several common types of
thermal errors including intracycle flame arrival
effects and signal drift during engine load transients.
