As it seems with anything, someone will come up with an idea and for sure, someone will give it a try.  Installing the Japanese version of the Mazda 2.5L plant in the Probe/MX-6/626 is no different.  Someone had the idea, some people found sources for the motors, and now people are actually having them installed.

What makes the KL-ZE so much better than the US-standard KL-03?  For starters, how about 200HP .vs our 164?  Larger VRIS ducts, higher compression ratio (10.0:1), better cams, and better flowing intake manifolds are some more.  There seems to be some debate as to whether or not the pistons and rods are stronger than the US counterparts so I can't say for sure.  It was originally thought that they both were stronger, then just pistons were stronger and the rods were the same, now they may both be identical to ours.  Since no one has actually taken one apart and checked it out, we can't tell for sure.

What we do know is this:

1) The motor makes substantially more power (see dyno charts).  At least 35HP more than a KL-03.
2) It is essentially a direct drop-in replacement (motor mounts and tranny all bolt up).   Some have reported problems such as not having a cruise control vacuum line, but this is easily remedied.
3) There is no EGR connection (this is a big no-no in smog controlled areas).  This is why the motors are sold for "Off-Road Use Only".  OBD-II cars (96-97), I probably wouldn't try this swap.
4) The US-Spec ECU will run it, but even higher gains are expected with the correct programming for it.  It's clear from the dyno charts that the ECU is using the incorrect VRIS points for the J-Spec motor.  Fueling/timing may also need to be adjusted.  A little tuning here could go a long way in increasing the performance of this motor.
5) It is not cheap, but the cost of bolt-ons that afford this same power increase could cost you just as much.  Motor: $1200 for 30+HP at the wheels.  GReddy, HS headers, HS intake: $1000 for 20-25HP at the wheels.
6) This motor will get you to the 14s without mods.
7) This motor will get you to the low 14s, maybe 13s with mods (naturally aspirated).
8) With NOS?  There maybe some concern with any forced induction or nitrous use on this motor due to it high compression ratio.  However, I wouldn't rule this out as reasonable amounts shouldn't necessarily exceed the engine's mechanical abilities.  A 50 shot of NOS=low 13s/high 12s?

Where can you get one of these?  Try Corksport or SOKO America. SOKO sells the motor for $1200 without the ECU.  Corksport can NOT obtain the ECUs separately, so don't call them and ask!   There are people currently on the lists trying to locate a J-Spec ECUs so the code can be flashed onto US boards.  Check with the lists for questions regarding the ECUs.

Take a look at dyno charts of the KL-ZE compared to the KL-03 (KL-ZE dyno runs courtesy of Michel Fortier).
ZE .vs 03 Chart of Michel's '95 PGT with the OEM motor (modded) and then his KL-ZE.
ZE .vs '93 .vs '97  Recall that William's '93 PGT had a substantially different curve than any of the '94-'97s that we've dyno'd.  His HP curve continues to go up in a similar fashion to the ZE's.  This is a comparison of the ZE, William's '93 PGT, and my '97 PGT.
ZE .vs Stock  Michel's '95 ZE-equipped PGT compared to Felipe's '95 stock KL-03 PGT.

These are photos of the KL-ZE (J-Spec 2.5L) motor in Darwin's '93 MX-6.  See photos of Michel's motor at his Super Probe Page.

                          KL-ZE (200HP)                                                KL-03 (164HP w/o intake :-)

You can see in the above photos that the intake manifold is the easiest way to tell the different motors apart.  The KL-ZE has intake runners that are wider and flatter, giving them a somewhat rectangular port.  The KL-03 has thinner, taller runners with more round ports.  Also, the #1 VRIS plate on the ZE is in the middle of the manifold, where the 03 has is directly after the throttle body. 

Above left, you can see that the intake runners appear flat.  Above right, notice how the intake manifold has a long, thin "neck" after the throttle body (increase velocity?).

Above left is a close-up of the low speed tube connecting the two intake runners.   Notice how it is long and sweeping compared to the KL-03's that makes a tight U-turn between chambers.  The hump behind the spark plugs is the VRIS chamber.   Above right is a photo from the driver's side of the motor.  Again, note the VRIS housing and the neck after the throttle body.

And this is the car that it is in!

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