To go with the new workshop, most of the race car type stuff will be on a new website:

SX Developments

This site will be updated when I’m doing jobs or projects that are less racing oriented.

After the excellent result at WTAC I think most of the work will be racing related for a while

It’s a tubular steel frame chassis running a motorcycle engine (Hayabusa), with fibreglass / carbon fibre bodywork.

This one had a few electrical and mechanical issues, and needed a few upgrades to be competitive with the newer cars it’ll be racing with.

First step was to fix some of the wiring problems, with some parts connected up wrong, and a few damaged and melted connectors:

The next step was adding a mounting frame for a rear wing. This also supports the rear half of the body, replacing the original frame which wasn’t strong enough to support a wing.

A proper front undertray / splitter can really help generate downforce at the front of the car, and smooth out the air flow under the floor. This one is a foam core composite and I attached it with some aluminium angles underneath to spread the load and provide some rub strips.

The rear wing mount also provides a mounting point for a rear diffuser, which is the final ingredient in the aero setup. It keeps the air flow clean from the floor to the rear of the car and allows the air to gradually increase in pressure to keep the low pressure zone under the floor for downforce.

The bolt in the middle is a jacking point, as well as a handy place to attach a safety chain for towing.

After changing the springs to handle the extra downforce, moving the data logger / dash unit to be more visible, messing with a few sensors, and tidying up most of the loose ends it was time to take the car to the track for a shakedown:

We found a few more issues to fix up before racing (some more lingering wiring issues, and failing oil pressure sensors) but the car went well while it ran, and is looking good for the racing season!

I built a trolley using an old pallet jack with an engine hoist was able to lift the prop into a vertical position, roll the trolley under it, and bolt the “axle” through to keep it in place.

The prop is 1.75m in diameter and weighs 420kg, so it’s not the easiest thing to move around!

Rather than finding another S13 engine in good condition, which is getting harder, it’s becoming more common to install an S14 or S15 engine.

This car had an SR20DE (non turbo), and was replaced with another SR20DE, just the later version.

The mechanical part of the conversion is fairly straight forward, but where people get stuck is the wiring.

Unfortunately there are no proper diagrams available for the SR20DEs, but by comparing to the various versions of DET (turbo) diagrams it’s possible to work it out.

The main difference is that the S14 and 15 run the power supplies for the ECU and sensors through the dash wiring loom rather than the chassis loom at the front of the car like the S13, so a large section needs to be added, and the dash loom connection changed to work with the S13.

The coolant temp sensor is also different, but swapping in the S13 one from the old engine means the temp gauge on the dash will still work properly.

It’s a bit of a slow process, but once it’s done you can have a later model engine working in the earlier car.

The Camry V6’s Y-pipe actually sits in a similar position to the MR2’s exhaust section that passes under the engine.

I cut the pipe just after the flexible section (which allows for engine movement) and then made a new pipe from there to the cat using 2.5″ mandrel bends.

The Camry Y-pipe is a bit restrictive so eventually it will be upgraded to a nice set of extractors.

The factory cat was replaced with a high flow stainless steel one, and I welded some extra pipe and flanges onto it in the same positions as the original so they can easily be swapped if necessary.

Generally there’s a pump in the fuel tank feeding the surge tank, then a second pump picks up from the surge tank to supply the engine.

If the fuel moves away from the pickup in the fuel tank during cornering there’s a backup supply in the surge tank, which can run the engine until the main fuel feed comes back.

Usually surge tanks are mounted in the boot, which means bringing a bunch of fuel lines inside the car, which is not ideal for safety reasons, and always results in fuel smell in the cabin.

For this one the idea was to mount it under the car, which meant it had to sit close to horizontal. It’s best if a surge tank can be vertical, to reduce the fuel sloshing around away from the pickup at the bottom.

I mounted the tank with as much angle as possible in the available space, and added a baffle inside it to minimise sloshing.

The fuel pump mounts beside the tank, and has its own power supply directly from the battery - via a relay triggered by the original fuel pump power.

Just an upgrade from an older depth sounder / fish finder to a new one with GPS mapping and more advanced features.

It’s just a matter of mounting brackets and connecting up wiring, but because I was replacing an older system I had to use a larger than necessary hole that was already in the transom.

After getting most of the wiring done for the V6 it was time to remove the original 3S-GE engine.

Even removing the engine is a bit of work on the MR2, with cramped access and a ridiculous amount of hoses and wiring! The gearbox also has to come out, along with the crossmember and rear hub assemblies.

While the engine bay was empty I mounted the oil cooler between the engine bay cooling fan and its mounting plate. This will eventually be controlled by the ECU depending on oil temperature.

The next step was to get the gearbox lined up with the engine and modify some of the mounting holes to allow it to bolt up properly.

Once it’s in the engine bay it looks like it’s meant to be there! (and really Toyota should have done this!)

Looking at the available materials I figured a trike was the best idea - starting with the front forks from a Kawasaki GPX250. First step was removing the headstock from the frame:

Then welding it to some 4″ tube which I can only assume was scrap truck exhaust:

A borrowed boat trailer axle provided the rear wheel setup:

after being welded to the frame tube with a nice thick steel plate in between:

With the addition of an old race seat and a foot peg, the trike was complete:

I was going to keep it “rust core”, but decided that it didn’t match the sections of blue painted steel, so it really needed a proper coat of paint:

The event itself was awesome, and the 700m long track with 100m fall was suitably fast and scary!

We had round robin heats for the first half of the day, and a full grid race for the final at the end.

I was lined up on P2, and got a bit of a slow start due to the trike’s weight. The wide rear axle makes overtaking difficult so I was a bit stuck until the leading kart snapped a wheel off and spun out and I managed to take the win!

Here’s my wrap-up video of the event:

Full helmet cam video from the final race:

Next year I’m going to have to build something lighter and narrower

I originally bought it as a rolling shell:

I ended up stripping it down to repair rust, mainly in the floorpan.

I since found that the wheels had broken spokes and various other parts needed replacement, so I ended up doing completely new suspension. I couldn’t find wheels wide enough for the wide body rear guards on the car though, so after much deliberation (6 years or so!) decided to remove them:

Underneath there are various areas with rust, but it’s not too bad. The panels have been “massaged” a bit for the widebody install, but I think it will tidy up ok:

At least it’ll save some weight

The next step was to cut out the old spare wheel well, which will be replaced by a piece of aluminium sheet with a racing fuel cell mounted underneath.

Holes for the tank filler and vent lines:

A pair of steel straps will hold the fuel cell in place:

Currently the fuel pump is mounted in the engine bay, but it might end up moving to the back for better fuel pickup:

Once the fuel setup is working the next step is the exhaust, then some body work and fitting out the interior - including a roll cage, harness, etc.

The aim is to have the car set up as a very minimalist race car, keeping the weight down, and not needing massive power to be reasonably fast - and most importantly, fun!