PROJECT: 1998 Nissan 240SX SE Jim Wolfe Technology ECU
The 1995-1998 240SX's get a pretty lame rev limiter (6500 RPM), and a
good bit of throttle lag. To help improve this, especially with a possible
cam upgrade, I ordered a Jim Wolfe Technology POP ECU upgrade through
Andreas Miko (there's more to his last name, but I can't spell it). The later
S14's (1997 and 1998) have an OBDII ECU v2 that JWT can't upgrade. Instead, a
OBDII v1 ECU from a 1996 is used (or a 1995, with a simple additional
modification). That's OK with me, in case I want to go back to the original
for some reason. Andreas procured a 1996 ECU for me and I received it in
good time from JWT (they are a little backed up with ECU programming from
what I've heard).
Impressions are that throttle response is much better. I have a 1992 240SX
that I drive daily, so I can do a back-to-back comparison (the 1992 is stock).
Mid range is greatly improved, and that pesky 6500 RPM rev limiter is gone
(whee-ha!) I had my car dyno'd before the ECU - I'll have to get another
dyno run now that it's installed.
Here's what I had to do to install it.
Back side by side.
Labels side by side.
Original 1998 label.
JWT POP 1996 label.
Here's the comparison of the 2 ECU's. They look pretty much the same.
Note the labels. The 1998 is a non-california car. The replacement ECU was
from a 1996 California car, I believe. It's fine, however, as the CA car
for 1996, the only difference was a exhaust temperature sensor. In the 1998
car, even the non-california ECU has the exhaust gas temp sensor.
Pull up here (pin locker) first.
Then lift and pull the pin out.
Some wiring modifications are needed. JWT provides the rewiring chart in
PDF form (view it HERE). It's pretty easy, and
you can see the additional single wire change to make for a 1995 ECU.
Getting the pins out is a little tricky. The first pic shows the pin locker
that needs to be pulled up before trying to pop the pins out. Pop it up a
little, then (as the next pic shows), go in from the front. Pull up on the
small white tab holding the pin, as you pull on the wire from behind. No
problem, and the rewiring should take only several minutes.
O2 comparison. Larger is 1998.
Here's the O2 adapter and the original piece.
Another pic of adapter and original piece.
In addition to the wiring changes, the later S14s use a different O2 sensor.
The 1998 O2 sensor is a 4 wire sensor and is 18mm wide at the threads. The
1996 sensor is a 3 wire that is 12mm at the threads. Note the size difference
in the first pic. Also note the pins pulled out of the 3 wire sensor. Just
lift and slide the pins out (lift from the pin side, pull on the wire), and
pull all the pins out of both connectors and swap them as is shown in the JWT
documentation (HERE). You should not have to
solder or cut anything. Great for going back to original in a bind.
In order to make up for the difference, a 18mm-12mm adapter is needed. By
JWT's recommendation, I picked up a spark plug anti-fouler (it's in the HELP
area at just about any parts store). Drill out the center of the piece with a
bit just big enough so that the 1996 sensor can fit through it. Then tap it
with a 12mm x 1.25 tap. You only need the bottom piece, so cut where the 18mm
threads end. I also dremmeled out two small lines (shown in the right pic),
so that there's a way to get the adapter out!!! (with a driver and hammer).
Screw the O2 sensor into the adapter, apply some anti-sieze to the 18mm
threads ONLY, and screw it in. No problem!
