Project bB: Completing The Conversion

If you cast your minds back to my last Project bB update (I’m sorry, it’s been a while), you’ll remember that my 1NZ-FE engine was in the shop getting all the prep work for its boost injection.

Despite my lack of stories, in the time since quite a bit of progress has been made, so today it’s time for a long overdue catch-up post. Or at least the first one.


For those of you who don’t know what my project is all about or have forgotten about it, the short story is this: I’m taking a 2005 Toyota bB (the Japanese domestic market version of the first-gen Scion xB), turbocharging its 1.5-litre four-cylinder engine, and setting it up as a fun street car.

The emphasis is on fun; if I was even half serious about actual performance I definitely wouldn’t have chosen the automotive equivalent of a toaster as a base. So here we are…

Right from the get-go I knew the car needed a manual gearbox. If I lived in North America I could have just bought an xB with a 5-speed on the floor, but the JDM variant which I imported to New Zealand was never offered in such a spec.

There was only one transmission option, and that was a column-shifted 4-speed automatic. As desirable as that may sound, it had no place in Project bB.


At the time we originally removed the engine from the car at JTune Automotive, I made sure to test fit the Toyota C56 manual gearbox I had pulled out of a wrecked NCP13 Toyota Vitz RS. Although I wasn’t 100% sure it would bolt in, I was quietly confident, and indeed the two mounts lined right up. But what about the rest of the manual conversion?


Looking at the firewall gave my buddy Kevin and I the first hint, and it was a promising one. The hole that the bB’s automatic transmission shifter cables entered the engine bay through was perfectly placed and perfectly configured to mount the Vitz’s clutch master cylinder. In the left-hand drive manual Scion xB this is of course on the other side of the firewall, but the right-hand drive bB firewall has a provision nonetheless. I guess it might be that the firewall was used across the whole range of Toyota NCP models in era, both automatic and manual variants.

In the manual Vitz the clutch master cylinder shares fluid from the brake master cylinder reservoir, and while I could have picked up a line to do this, I’ve ended up with a different solution. When I grabbed my manual conversion parts from the local wrecking yard, I also purchased a dedicated clutch reservoir from a Celica ST202, which fits the Vitz clutch master cylinder perfectly.


Moving inside the car, I removed all the seats and the carpet to fully expose the floor pan. Perhaps not surprisingly, the provision for a manual shifter was all there and the Vitz RS unit bolted straight in.

The only thing there wasn’t a provision for was the new C56 gearbox shifter cables, but cutting out the blanking plate quickly took care of that.


Another difference between the xB and the bB is the park brake. In the bB it’s a foot-operated pedal under the dash, while in the xB it’s a hand-operated lever between the front seats. Because there was no room for four pedals under the dash, I knew I’d be changing to a handbrake, but that then meant I couldn’t use the bB front seats, which despite being two separate units actually resemble a single bench. I’m fine with that though, as I have other plans for seating anyway.

Before ripping the interior out I wasn’t sure how the foot park brake connected up to the cables which run out to the rear drums, but right away with everything out of the way it was obvious I could simply bolt in a Vitz handbrake and connect everything up. At this point I was pretty happy, and even more so when the Vitz center console clipped in place, too.


Of course, there had to be one aspect of the conversion that wasn’t completely straight forward, and that turned out to be the brake pedal. While the clutch pedal hung off the mount for the car’s original foot park brake, the Vitz’s brake pedal had a different mount. Cutting the bB’s large rectangular brake pedal down would have been an easy solution, but being positioned a bit too far over to the left where the clutch was going to be, it wasn’t the best option. To see the job through properly we cut off the correct mount and Kevin welded it on the Vitz pedal assembly.


In order to bolt up the clutch pedal I needed to remove the instrument cluster so we could go in through the top of the dash, and while I had that out I took the opportunity to replace its original filament bulbs with LEDs. Previously, the white-faced speedometer/tacho glowed a dull warm white colour, but to give it a fresher look I’ve gone with daylight-white LEDs which ran me just a couple of dollars.

At this point I also removed the factory 2DIN head unit, and as that involved removal of the console fascia I upgraded the two bulbs that illuminate the A/C and blower fan controls at the same time.


These four LED bulbs were a cheap and easy modification, and I’ll be sure to give you a comparison between the old and new a bit further down the track.


Aside from the clutch line, the only other thing I needed to check off for the conversion was the ECU. Yahoo! Auctions Japan came to the rescue here, and running the kouki NCP13 Vitz RS manual transmission ECU will ensure the engine’s VVTi system works as it was intended to. The ECU plugs straight into the bB’s factory wiring loom, but there’ll soon be an aftermarket harness sitting in between the two connections to accomodate a fully programmable engine management system.

Although I’ll need to wait until the engine is refitted before my Vitz gearbox goes into the bB, there was another job to tick off the list while it was out of the car.


Around 15 years ago I picked up an AE111 Toyota Levin straight from Okayama, Japan. It was a street-registered car but saw track time, hence a number of modifications. I’ve had the car tucked away in the back of my garage for a long time, but while recently preparing it for sale I removed a few of its parts, one of them being perfect for use in my bB.

Like the NCP13 Vitz RS, the AE111 Levin/Trueno came with a C56 gearbox, albeit with a slightly different casing. Internally they look largely the same though, which meant a differential swap was in order. Good bye open unit, hello Cusco Type-RS limited slip diff.


While Kevin had the gearboxes apart, we ensured that everything else looked good, which it does.

The Cusco diff is a 1-way unit, which means it only locks on acceleration, so it’s perfect for street use, which the bB will be seeing 99% of the time. As I picked up a complete replacement C56 gearbox for my Levin, I’ve now got a spare set of gears from the original gearbox should anything in the Vitz RS C56 require replacing down the road.


The only other thing I now need for the conversion is a quality performance clutch, and as I write this there’s one on the way down to me from the USA. Hopefully it will be with me in the next couple of weeks, and therefore can be included in my next update.


For the final aspect of this update we delve back under the car for another Toyota parts bin modification, and one I’ve been looking forward to completing since the very start.

Like the first-gen Scion xB, the first-gen Toyota bB featured drum brakes on the rear end. They work adequately of course, but discs look better behind wheels and for that reason alone a swap had to be done.


Both the JDM NCP10/13 Toyota Vitz RS and NCP61 Toyota iST (Scion xA) feature rear disc brakes, and as those cars are a dime a dozen at wrecker yards here in New Zealand, finding one was easy. Thanks to the guys at NZ Car Parts Auckland for sorting me out with what I needed.


My initial idea was to simply drop out the compete drum-to-drum bB beam and replace it with the iST disc unit, but when we got them together on the ground and took a few measurements, they actually turned out to be slightly different.


Because the disc brake unit (which incorporates an internal drum for the parking brake) is thicker overall than the drum unit, an adjustment to the mounting points on each beam was made to ensure they were both the same width when fully assembled. This got us thinking…

If we had just put the disc-equipped beam in as-is, the bB’s overall rear wheel track would have remained the same, but if we mounted the iST hub and disc brake assembly on the bB beam, I’d be able to gain some extra width at the rear – around half an inch at each side. As any first-gen xB or bB owner will know, in stock configuration the rear wheels sit further in under the bodywork than the fronts do, so spacers or wider/lower offset wheels out back are a common thing. By using the discs on the bB beam, I’d peg back some of this track width deficit.


To do this, we needed to cut one brake line bracket off each side of the iST beam and weld them in place on the bB beam.


Refitting the beam and getting everything buttoned up was straightforward, with one exception – the hand brake cable was too short. It bolted up perfectly, but just wasn’t long enough to reach the connection point. The fix was easy: swap the bB cable into the iST brakes. Job done.


With the conversion work done and dusted we’re now moving on to some more exciting parts of the build – starting with this stack of AEM Performance Electronics goodies – and I’ll be delving into the first of those in my next update.

Brad Lord
Instagram: speedhunters_brad



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Didnt know Cuisinart had any performance upgrades for its toasters...interesting


I've always called this thing the XBox myself...

Jackson Gardner

Your comment is the best thing I've seen in all my life....LMAO!!


I absolutely love when people decide to take Mundane cars and make them more fun, and in a variety of Levels of Fun/Headache, but reading your tales of progression is quite nice. Keep up the great work and I hope all your shipments arrive on time.


Thanks FredMiro, I'm looking forward to sharing more soon!


YES!!! I love reading about speedhunters project cars, especially this one. It's going to be such a fun little car.


Hopefully it will surprise a few people, or at least burn some front tyres trying! Should be fun either way.

Charlie Markham

It made my day to see this pop up on my feed! I've loved this project since the beginning and its great to see how its going, keep it up! There are never enough boxy hot hatches.


I agree! Thanks for the comment Charlie.


The magnitude of work done to a car this mundane is in itself enough to make this project exciting! Keep up the good work!


Thanks Mayank, I have to say it's a lot of fun!


the cool thing is both my yaris and your BB use the same literal engine, it will be fun to see the turbocharger write up.


1NZ power!


yeah i managed to hit 10 mph on the highway yesterday in mexico,

compared to the BB at 1400 kg (3086 lbs) before the driver, with full tank and fluids

the yaris i have weighs in at 1059.138 (2335) before the driver, with a full tank and fluids.

there stout roubust engines, ive raced it, beat on it and it still fires up and smooth like a mercedes.

all 106 hps of fury.


10mph or 100mph? Haha!

Does the bB weigh that much? Surely not..


10 (1̶0̶0̶ )

the BB weighs 1,050 kg (2,315 lb) apparently its fatter in america somehow.

if you think driving a giant top heavy toaster at triple is scary , try doing it in a car that was designed for the city and was never supposed to go over 80 on 5.5" wide rims and stock suspension.


1400kg might have been for the second-gen xB? That one was much bigger and heavier than the first gen xB/bB.

Actually, the bB doesn't have much weight up top, but you definitely notice a strong side wind!


yeah thread since i cant link it is:

DIY: 1zz-fe throttle body swap



i think this might apply to the 1nz in the bb, the 1zz 1.8L throttle body fits , i think and so do the 1zz(2zz?) injectors. I know its documented on yarisworld, but if you do the 1zz tb swap if gives you a bigger bore and a faster, throttle butterfly valve response?


I do have a 1ZZ throttle body, but might see how we get on with the factory 1NZ setup first. If I go to a bigger throttle body, I think it will most likely be a 2ZZ TB on an aftermarket intake manifold. Yes, the 1ZZ/2ZZ injectors fit, but I'll probably go with something bigger.


As a 2 time xb owner I'm looking forward to this, these cars are extremely fun to drive. Especially when lowered,sway bars,under/strut bars. I outhandle some fancy cars....Driver mod tho


I'm just looking forward to driving this thing with a manual gearbox! Definitely need to look into some more suspension upgrades over the basic stuff I've already got to go in.


I think this car is a perfect example of how a boxy body can be hotter than one w/ curves...


Amen to that, and here's more proof.


I like how these cars are like massive piece of Lego, everything just like plug & play.


It's definitely made the conversion work a lot easier so far!


So happy to see this project again, its one of my favorites!

Matthew Everingham

It's so refreshing to see work being done instead of just the finished project all the time.
Please tell me T0A5TR is an available number plate option?


It is, but I'm not sure I could spend almost the same amount of money as the whole car cost in the first place on a couple of pieces of tin. I need that money for front tyres!


Please, kind sir. Continue.


you put the Project into Project cars.


Boring cars made to be fun.. I guess thats what speedhunting is all about?


I'm definitely hunting for speed with this thing!


I'm following this build. Can I have all the Vitz RS badges please?


A fair amount of work has been done, full speed ahead, its coming together nicely!