The B6T Engine Swap

    In my quest for a more powerful 323 I soon realized the limits of the stock B6 engine (SOHC 1.6L).  Or may be I just reach the limits of my knowledge about engines.  Changing an ECU I can handle, but changing camshafts or porting cylinder heads is something I don't want to mess with.

    I had heard of some people swapping the B6 with a B6T engine (DOHC 1.6L turbo) and that it was a relatively easy swap, only a change with one motor mount was needed to make the engine fit.  One problem would that I would still need a turbo ECU and a wiring loom, and possibly some other stuff.  But the seed was planted, I wanted that B6T!

The B6T

    The cast-iron block on the B6Tis basically the same as that of the standard B6 engine, but it's been modified to work efficiently with the turbocharger.  Two more valves per cylinder, 16 in all, improve engine breathing and center-mounted spark plugs optimize combustion.  Two camshafts instead of one operate the valves through hydraulic lash adjusters and computer controlled fuel injection provides the precise amount of fuel.  Packing the cylinders with air is an intercooled turbocharger.  By cooling the air after it leaves the turbocharger, the intercooler increases its relative density.  And more air supports more fuel for greater combustion, which equals greater power.  There's 50 hp more than the B6 and 44 lb.-ft. more torque.

Cutouts of the engine and turbo:

The B6T in the U.S.

    The B6T was offered in the States for the  1988 and 1989 Mazda 323 GT (fwd sedan) and Mazda 323 GTX (4wd hatchback) and the 1991-1994 Mercury Capri XR2 (ugly fwd convertible coupe).  The B6T had a horsepower rating of 132 versus the B6's 82 hp.

    To say that this engine is rare in the U.S. would be an understatement.  Mazda only offered it in minimum numbers to qualify for the fabled Group A class in the World Rally Championship.  The last stop the WRC ever had in the U.S. was in 1988, in my home state of Washington, entitled the Olympus Rally.  It was there that Rod Millen's 4wd 323 captured the Group A title.

Rod Millen's 323:

Corksport

    At least in the U.S., finding a low mileage B6T is next to impossible.  A good alternative is to buy an imported J-Spec B6T from Japan where these engines are more common.  The nearest shop to me that sold these engines was Corksport in Portland, Oregon.  Derrick and the guys there know their Mazdas, had performed the B6T swap before, and are less than a 3 hour drive away, making them the obvious choice to buy the engine from and perform the installation.  Arrangements were made and on November 12th, I drove down to Portland, dropped my car off, and took the Greyhound bus back home.  My car was there for three weeks, a week longer than expected because the Thanksgiving weekend holiday hindered the availability of parts.  Being the "can't function without a car" American that I am, being without my 323 for three weeks was really tough, somehow I survived.

Here's what Corksport installed:

    J-Spec B6T Engine, used (50,000 miles)

    B6T ECU, E.L. Prototypes, used (8 or 9 p.s.i. of boost)

    VJ-14 Turbocharger, used (80,000) miles    

    B6T wiring loom, used

    Ford Probe/ MX6 Intercooler, used

    HKS 90 degree rubber elbow

    HKS air flow meter adapter

    HKS 70mm connector    

    A.C.T. Stage II 1.6L SOHC clutch

    NGK spark plugs

    NGK 8mm spark plug wires

    B6T air flow meter, used

    RX7 Turbo II fuel pump, used

    Car Sound high flow catalytic converter

    Exhaust flex joint

    Passenger side motor mount frame bracket, used a 323 GT mount

    Mandrel 2.5" exhaust pipe bends, flanges, and gaskets

    Upper radiator hose

    Wix oil filter

    Thermostat gasket

    323 GT front bumper silver, used (Thanks Brett)

    Custom bracket to hold up air filter    

    Hose clamps

    Oil

    Coolant, gallon

Pictures

    Unfortunately Corksport doesn't allow photos to be taken inside there garage.  So there won't be any of the step by step pictures I was hoping for.  If you want some before shots, just take a look at my Pictures section.  Here's some after shots.

The engine, custom intercooler pipping, intercooler:

Air filter bracket, high flow cat, exhaust piping, ECU:

Exterior shots:

Driving Impressions

    The first thing I noticed, even before I started the car, was how hard the clutch was to depress.  At least compared to the old one.  (It's been a week now and I'm almost used to it.)  It reminded me a lot of my Mom's old '87 VW Jetta, the car I learned how to drive stick on.  The second thing I noticed was the note of the exhaust when I started the car.  It's a little louder, definitely a lower tone and it's more noticeable on the inside now.  I think the high flow cat is the culprit for the loudness.

    When I pulled onto the street I was half expecting to peel out because it was pouring down rain, but below 3000 rpms the engine is quite civilized.  I kept the revs low and shifted into 2nd.  It was time for my car to shine so I floored the accelerator.  The speed climbed at a pretty good clip until I hit that magical 3000 rpm mark.  WHOOSH!  It felt like I had been kicked in the back as my 323 surged forward with authority.  I then started to get that stupid grin on my face.  You know the one that only appears when you're really accelerating really fast.  Yeehaw!  I shift into 3rd and the car still continues to pull pretty hard.  Derrick, owner of Corksport and riding shotgun, comments that I shifted way to early.  The new redline is 7500 rpms!  I was used to the old of 5500 rpms.  I glance at the speedo, 75 mph in 3rd gear, not bad.  I pop it into neutral, slow down to the posted speed limit of 35 mph and head back to the shop.

Other Stuff

    The B6T that I received had a well documented 50,000 miles on it.  The mileage was a little higher than I was hoping but it's still way better that anything i could find stateside.  The turbo that came with the Japanese B6T is the VJ-13.  This is a smaller version of the turbo that comes with the U.S. spec B6T, the VJ-14.  So Corksport found a VJ-14 at a junkyard with 80,000 miles on it and installed that.

The Drive Home

    The drive home gave me a chance to stretch the car's legs with 3 hours of high speed driving.  It was a little stressful on the highway because it was dark and raining.  But it was still fun.  There were some new sounds I wasn't used to.  The whooshing of the turbo when It's spooling up for instance.  The weirdest one was when the turbo would by pass the extra pressure.  If you've ever seen South Park: The Movie, there's this one scene where one of the kid says, "If you get into trouble, make a sound like a dying giraffe, wooaahh."  The blow off sounds exactly like that, or maybe like a whale, like a really sick whale.  Sometimes it's really slow and drawn out, and other times it really quick depending on what I'm doing to the accelerator.

    Now the need to downshift in order to pass is gone, unless I really need to fly by someone.  If your cruising along at 65 mph in 5th and you want to step it up to 80, just floor it and you'll be there in a couple of seconds.  If you really want to pass someone, go ahead and drop it into 4th, it's okay because it's good until about 107 mph, then you might want to shift to 5th.  A couple of days later I did manage to hit 120 mph in 5th with rpms to spare but the car aerodynamically did not want to go any faster.  The problem with going that fast was that the air pressure on the outside of the windows starts to pull them and the door outwards from the frame so you can actually see a little daylight.  At that point it gets super noisy with all the wind so I decided to slow down.

Performance Numbers

    I managed to do a couple 1/4 mile runs with my trusty (but who knows how accurate?) G-Tech Pro. Let's see how I did:

Pre engine swap (88 323 SE with B6) 1/4 mile:
17.3 sec @ 80.3 mph with 10 sec 0-60

Post engine swap with other goodies 1/4 mile:
15.6 sec @ 96.1 mph with 7.2 sec 0-60

It was tough to get a good launch in 1st gear.  The car would either burnout or get bogged down.  With a little practice hopefully I can dip into the 6 second 0-60 zone.

What's Next?

    A small oil leak that needs to be fixed.

    Paint the bumpers red.

    A boost gauge so I can be certain of what boost I'm running.

    Maybe an electronic boost controller to raise the boost to 16 psi if I want to, just short of the destruction point of the turbo.

My Thoughts 2 Months Later

    If you're ever going to replace your engine, replace every gasket in the new engine as a little preventative medicine.  I've had two oil leaks that cost $1000 to fix.  It would have been real easy to replace these when the engine was out instead of having to pull things like the transmission after the fact.

    A limited slip differential (LSD) would be nice.  Anytime one of the front wheels start to slip, all the power goes to that wheel, resulting in one legged burnouts.  The only time this is cool is when I'm going around a quick corner in second gear around 3000 rpms.  The inside wheel can't get traction and quickly disappears into blue smoke and nice peel out mark is left on the concrete.  It's not cool when trying to get a good launch when drag racing.

   Gas mileage went from around 25 mpg to 18 mpg.  And that's only when I'm not being a lead foot, which is almost never.  It can get expensive when my baby only wants to drink that premium 92 octane designer gas.

   Nobody wants to race me because my car's a sleeper. :(

The End

    Hopefully this helps anyone who was curious or maybe thinking about getting a swap done.  As usual, if you have any questions, feel free to email me.