Project Japanarat

I'm really not much for naming things but this one just popped in my head one day. My AW11 really embodies my love for small Japanese sports cars and classic rat rods which were stripped of all components that didn't make them faster.

This is the story of my AW11.

I got the 1989 supercharged MR2 when I lived in Portland. It had three burned valves and a broken timing pointer suggesting the previous owner had put a bigger supercharger pulley on it increasing the boost without addressing the low end leanout issue the stock ECU is notorious for. Apparently they put the stock pulley back on to sell the car.

I replaced the valves and did a light rebuild on the head and put the car back together. It had some other problems that I started to find such as a stripped axle nut, high idle, worn suspension and a number of other issues. I managed to catch some fresh threads with a second nut on the axle but due to these issues I didn't put many miles on the car for the first couple years. Around 2004 I moved back to Colorado and slowly started putting time and money into the car. I fixed the axle and replaced the wheel bearing that had completely grenaded one row of bearings long before I got the car.

 

 

It was also around this time it got spray painted satin black. Metalic blue might be a nice color on some things but not on my car.

I upgraded the suspension to Ground Control Coilovers, Tokiko HP struts, Poly bushings and Twosrus rear tie rods.

Now that the car was getting closer to healthy and more reliable I started driving it more. It was around this time that the supercharger let go. I had never been fond of the supercharger, how much room it took up and the convoluted piping in the engine bay so I decided to ditch it and put a turbo on.

At this point the car was my daily driver and I needed time to plan out the turbo build so I picked up an NA intake manifold and installed that and a couple other pieces to run naturally aspirated while I planned the build. I also made a spacer to move the water pump out to the outer pulley since it could no longer be run on the supercharger pulley.

As one might guess at 1.6 liters and 8:1 compression the car was a dog but it did get me to work for a few months while I ordered parts and planned the build. I also installed my first wideband. It was an NGK AFX and opened my eyes to a whole new world of monitoring and tuning. I started learning the behavior of the GZE ECU and it's strengths and weaknesses. I will make another article that goes into more detail on my findings and experiences tuning on the 4A-GZE ECU.

Once I got all my parts together and had a game plan I pulled the car into the shop and 26 hours later pulled it out making boost. I drove this setup for about a year and probably 5000 miles before the engine let go

After some thought I decided I would much rather go a little more modern and efficient instead of rebuild the 16 valve. My first choice was a 2ZZ turbo but at that point it was very cost prohibative just due to the cost of the motor and trans at that point in time.

After a lot of research I came to the conclusion that I should be able to run a Blacktop motor on the GZE ECU and electronics. I even found one other member on the boards who had done something similar with some degree of success. Being able to start with just the engine swap and not have to worry about the engine management or serious wiring swayed me to the build.

The next question was how much boost can a stock Blacktop take on GZE electronics and 11:1 compression? I decided to build the intake and exhaust manifold as I wanted it and start tuning with the turbo in place but with the wastegate disconnected in the beginning so I could start getting a feel for things before I blew it up.

I always hated how hard the turbo was to get to in front of the motor. On my new build I could have made it a little better but I like things that are extremely easy to access and work on. I also knew I wanted something that stood out from the crowd. This made it easy to decide to put the turbo above the motor. I also knew I didn't want long plumbing to an intercooler nor did I want an intercooler cluttering up the engine bay. After a lot of thought I decided to integrate a small water to air intercooler into the intake manifold. The original design was a lot smaller in my head but I decided to stretch it out considerably to try to get more laminar airflow and even flow to all cylinders. Some day I would like to do a similar but much more compact design. Maybe even one that fit under a stock engine lid.

 

 

There were a few small hurdles.

The 20 valve injectors would never work with the GZE ECU. The 20v uses side feed so I couldn't use the stock GZE injectors. I knew that the ECU didn't like 440s very well but I figured I could tune something to work that was up to about 15% bigger than stock. After lot's of research I stumbled across 1JZ 380cc injectors. I figured these would be about perfect.

I had to do a little rewiring including wiring the BT injector clips, distributor clip, coil/ignitor, TPS and a few other things. While I was sitting in the trunk leaning over the firewall I decided once again that ease and access was most important so I cut out the rear firewall. This made wiring a breeze.

My main sources for figuring out wiring were the 1989 BGB and wiring diagrams, the Blacktop factory service manual and wiring diagrams and some of the wiring information found on padandwheels.com.

 

 

 

Most everything else was pretty plug and play. I got two sections of steel braided radiator hose to run to the tubing that runs up the tunnel. I used regular steel braided line to run the heater lines and I teed the turbo cooling and coolant fill into the heater lines. Filling is a little slow but works great and gets rid of the engine bay bleed points.

For the turbo oil feed I tapped an NPT to -AN fitting into my remote mount oil filter housing nearly identical to the Moroso I sell in the store. Since the turbo sat above the motor I decided to drain it into the valve cover. Since I made that decision after ceramic coating the valve cover I just tapped an NPT to -AN 90 into the valve cover.

I have never liked conventional wastegate intersections and the way they put a big hole in the tubing.

I also wanted a nice flare from the turbine outlet diameter to the 3” tubing the rest of the system was made out of. I decided to try a new design that used spaces in the flare as the wastegate ports. This created a smooth transition and should maintain very smooth flow characteristics with the wasegate open or closed.

 

 

 

 

I was not 100% sure this design would flow enough but the hope was the shape would create a low pressure zone helping to suck the wastegate charge out. So far I have experienced no boost creep.
 

 

My motor mounts were pretty worn so I filled them with polyurathane.

 

I ceramic coated the entire engine as well as engine mounts, pulleys and any other components I could. The ceramic coating I use is extremely hard and extremely slippery. Grease, oil, dirt and road grime pretty much just falls off with a light wash.

I also reinforced the front engine mount which has been known to get pulled out. The plate is TIG welded to the chassis.

You have to be careful here as there is a fuel tank, fuel lines and a few other lines right around here.

I scored a great deal on a clutch set. It was a 200mm light weight flywheel, ACT pressure plate and a custom ACT 200mm disk splined for the E51. I was a little concerned with running a 200mm clutch but so far it has held up great and launches very well.

 

I also removed my cracked, faded and heavy tail lights and replaced them with Yamaha YZF LED tail lights.

 

It took some fiddling getting everything to work. I think there were some issues with the coil wiring and a couple other little things. Finally I got the car to idle. In the beginning it had a very bad tip in stumble. This is when you quickly give it gas off idle. My theory is that with the GZEs feet of intake piping and a supercharger between the head and the throttle body is that any throttle input will take a while to get to the head. Running the ITBs this will happen much sooner. I believe the ECU does not expect air to hit the head so fast when given throttle input. This behavior is the worst when it is cold. I managed to tune it out to the point of being acceptable when cold and unnoticeable when warm. This was accomplished through setting the TPS as tight as possible while still triggering the idle circuit and by getting the AFRs optimized by tweaks to the AFM. I spent the next few months dialing everything in, playing with different settings and getting familiar with the motor. Naturally aspirated the motor felt slower in the lower to mid RPM but faster than the 16v running 10 PSI in the upper RPM. Seat of the pants I'd say it felt overall about as fast as the 16v on 10 PSI. I was so happy with the power, balance and overall feel that I was in no hurry to run boost. I was still a little concerned about blowing up the motor the first time out on positive pressure and so I had to get some miles on the motor so I could justify the cost and time of a blown motor. During this time I started fabbing up the intercooler system. Once again going for something different and really wanting the shortest routing and overkill cooling I decided to do a heat exchanger on either side of the engine bay. This used two dual pass heat exchangers and a very large water pump. The design uses seperate -16 AN lines running to each system and is designed to easily add a second pump creating a redundant system.

I also hooked up a knock light and pyrometer so I could monitor all important aspects of the motor.

 

 

Finally I decided it was time to start pushing it. I cut the stock wastegate open and made a clamping system so I could swap out springs and close it back up. I then did some math and choose a spring that would hit about 3 PSI. My math was close but a little conservative. Never the less I was running a couple PSI boost and the motor seemed to be very happy about it. I started adding stiffer springs until I got up to about 6-7 PSI. At this point I decided I would rather have a motor making 7PSI reliably than risk blowing up the motor.

The next step will be putting it on the engine dyno where I plan on pushing it to it's limits using an array of monitoring devices including a J&S safeguard, detcan, and datalogging all big sensors including EGT, knock, AFR and more. Once fully set up it will be possible to monitor knock, EGT and AFRs on each individual cylinder. At that point we will see what a stock blacktop can take. Once I blow it up I will repair anything that fails and throw in some forged pistons. I will likely keep the compression ratio about where it is now and just see how far I can push it.

courtesy of webmatter.de