Clubman rally car build in <2 months

If you’ve been following us for a while you would know a few months ago we started a journey with a Clubman rally car build and a girl. Well those plans have changed. After a couple of false starts we began moving in the right direction in late March. By then it was just under a month to the start of the 2021 WA rally season.

The weapon of choice for a clubman rally car build

The vehicle of choice for our Clubman rally car is a Subaru WRX. It’s a 94’ Australian body shell however it had version 6 running gear installed from a JDM STI. The reason we eventually settled on this is because it was already a rally car. That saved a bunch of time with roll cage, suspension, seats etc.

We would have liked to have kept it as a WRX however to be able to run in the Clubman Cup we need to run two-wheel drive cars only. You’re not allowed to have turbo charging if they weren’t turbocharged as a two-wheel drive car so the path was clear. Convert a 4WD Turbo WRX into a 2WD non turbo Impreza.

Starting a Clubman rally car build by changing from 4WD turbo to 2WD non-turbo sounds like a bit of a backwards step. We’re going to do this in such a fashion that later on this car can be converted back to 4WD turbo as the driver steps up.

No compression!

Initially we had an engine and gearbox lined up. It turned out after doing some testing that the compressions on a couple of cylinders were rubbish (less than 80 PSI). We had to throw that motor in the bin and find another solution. Luckily one of our family members had a spare 2L single overhead cam engine sitting there.

We just didn’t have time to build a motor from scratch so it will have to do for the time being. A new cam belt had been fitted at some point however moisture had got into the pulleys. Throw away engine or not, we weren’t willing to risk it. In went a new cam belt, pulleys and water pump.

Getting the power to the road

For this Clubman rally car build we decided to use a WRX gearbox. You might think “hang on a minute, a WRX gearbox is four-wheel drive”. Well yeah that’s correct however there is a company in Australia that engineers a solution that changes the four-wheel drive transmission to two-wheel drive. Effectively, you remove the center differential and the rear part of the gearbox, fit a small insert in there and re-assemble.

Without quad cams and a turbo to provide power and torque we need to get what power we have to the road. The WRX gearbox has better ratios, a 4.44 final drive and a LSD. All that will give the Impreza better acceleration and traction. Also being a WRX body shell it’s got a hydraulic clutch in it whereas the standard two wheel drive gearbox is a cable clutch. Avoiding a pedal box conversion saved a bunch more time.

Holding the engine down

Whilst apart we replaced the engine mounts. The standard factory rubber engine mounts are pretty soft and it’s quite common for these things to split. The easiest fix is to fit Group N or STI engine mounts. They’re made of a firmer rubber and they’ve got a much stronger bonding. Basically you put a set of these in and they’re set and forget. You can buy Group N transmission mounts as well.

Removing the WRX engine and gearbox

The next step was to drop the WRX engine and gearbox out the bottom as a complete assembly leaving as much attached as possible. We found a few other problems that needed to be dealt with during the disassembly of the clubman rally car. The front brake pads were completely shot and the rears were not much better. We also found the right ball joint was ready to fall out and the right tie rod end was not very good either.

WRX clutch is f$#ked!

Once we got everything onto a pallet then it was time to separate the engine and gearbox and have a look at the clutch. Sadly the clutch was shot. The drive plate was actually cracked all the way round. It was lucky it hadn’t failed. These are the kind of unforseen things that quickly add up. It may be a tight budget for this clubman rally car build, however there are some things you can’t skimp on.

4WD to 2WD not that easy

With a new clutch fitted it was time to finish the gearbox and get the whole lot back in the car. We then encountered another drama. The two-wheel drive conversion kit proved to be troublesome. It started out straightforward as there’s really only two parts to the kit. Unfortunately the instructions are not very clear and missing a few steps. Also the plate that goes on the back of the gearbox turned out to be wrongly drilled. There was another problem with the retaining bolts too.

Sadly the problems didn’t end there. The shift mechanism itself connects up to the box fine when it’s all back in the car. The stabiliser support for the shifter is a different story. There’s a gap of 100mm or so created by the shortened gearbox housing so no way to bolt up the stay. That means having to fabricate up a plate or a bracket to sort it out. It’s  something that should be in the kit as far as we’re concerned.

Potentially deadly

During the clubman rally car build we discovered another item to rectify. This car has a bolt in cage. There’s no problem with using bolt in roll cage cages however putting the bolts through from the interior to the outside is an absolute no-no! What happens is if you have the threads sticking down toward the road, anything that comes under the car can catch the bolts. That can potentially shear them off and also causes lots of corrosion. The last thing you want to do is have the bolts snap or sheer off on your roll cage! The fix was to replace all the bolts with new hi-tensile units and turn them around so the threads and nuts are inside the car.

Roll cage bolts installed incorrectly- deadly dangerous!

One other item that we sorted was to remove the rear diff. We also dismantled the rear drive shafts because the outer CV’s are still needed to hold the rear hubs and bearings together. We retained the WRX rear cradle, cross member, hubs and rear brakes. This allowed us to keep everything WRX for ease of servicing and parts.

Over Easter we spent a couple of days sorting some bits and pieces on our clubman rally car build. Minor seam welding, stripping residual tar, seat position adjustment and fitting a new radiator were crossed off the list. The time however was now very tight and we still didn’t know if the engine even ran.

Which ECU is best for a clubman rally car?

The next priority was to get the engine wiring sorted. Initially I had planned to adapt the Impreza engine loom to the WRX body loom and go from there. That plan was thrown out the window due to cost and time. Instead the plan changed to building a semi-custom engine loom. That may sound more time consuming, trust me it wasn’t.

The first thing we did was un-plug and remove the WRX ECU as it wasn’t needed. From a donor car we had a SOHC engine loom so we tested each individual wire. We worked out what colour wire went where and labeled them all. This work is called “pinning out”. Often this is done to identify pins at wiring plugs like the ECU. The idea was to splice the SOHC engine loom to a stand-alone ECU.

At 11:00am on Monday morning, with 5 days to go to the rally, we finally had the ECU. This clubman rally car build was going right down to the wire (pardon the pun!) Over the years we’ve mostly done plug and play ECU’s like Link G4 and Autronic. I’ve done a few wire in ECU’s however it was to be our first Haltech.

Haltech Elite 550

I did a lot of research to try and find the best ECU for the Impreza. To sort it out properly I decided on a Haltech Elite 550. The ECU is the entry level unit that can drive up to 8 cylinder or two rotor engines. It can handle turbo charging as well. The 550 doesn’t have all the bells and whistles (VCT control, anti-lag etc) however it will do everything we want. It was the perfect fit for the nturally aspirated clubman rally car. Using the Haltech meant we could also do away with the factory air flow meter, knock sensor and O2 sensor.

As we’re now a Haltech dealer, I wanted to do a full wire in ECU as our first. We ordered the Elite 550 with a universal wiring loom. I opted for the 2.5m Haltech loom rather than plugs and pins. This was because the SOHC engine loom was not long enough to reach inside the car. With everything already pinned out we just had to splice all the wires and then power it up.

After a few sensor calibrations it was time to try and fire it up. When the engine sprang into life on the 2nd crank we were stoked! Who knows when it previously ran… With no exhaust and the thermo fans to be sorted we didn’t run it for long. Great validation that the Haltech had been a good choice.

Haltech Elite 550 running the Impreza rally car's engine

Getting the gas out

Wednesday and the car went for a new exhaust. We’d ordered some new extractors for the SOHC engine and found that the WRX front cross member had clearance issues. As we couldn’t use the WRX exhaust our exhaust guys sorted the extractors and built a complete 2″ system.

After another late night the car was on the trailer Thursday and off to the dyno for a final tune. A car should never be driven far or raced with a base map in the ECU. The ECU needs to be tuned properly by someone who knows what they are doing. Thursday afternoon and the clubman rally car was back in our workshop with the gearbox out.

Clutch is f$#ked again!

Eight o’clock Friday morning and the rally is Saturday. We should have been loading everything up and getting ready to go.  Instead we were dealing with a clutch drama. The hydraulics and  everything all seemed to be working fine however the clutch just wouldn’t disengage. We were lucky our dyno tuners were very patient. They tuned it by starting the car in gear and doing what needed to be done.

With the box out we discovered a faulty clutch plate that was jamming on the splines. The pressure plate was releasing, however the drive plate was just plain stuck. Our clutch supplier was good and replaced the plate. We double checked the plate and splines slid smooth as silk before putting it all back together. Testing was literally to run the Impreza in every gear on the hoist then drive it onto the trailer. No testing, no shakedown and not even a proper test drive. This was definitely not the way we like to do things!

Round 1 of the RallyWA Clubman Cup

Saturday morning and we arrived at the rally and set up. Round 1 of the RallyWA 2021 rally championship had dawned. The girl on this journey is Tiana. Literally her first drive was to take the clubman rally car up and down the road at about 30 km/h. Luckily it drove in all gears and nothing fell off!

Tiana and Graham about to head out to the first stage of the Winvale rally

Tiana and co-driver Graham had their work cut out; first rally for the 19 year old, tight, dusty stages and no familiarization with the new car. Given everything that transpired during the clubman rally car build they did a fantastic job. The duo were hovering between 2nd and 3rd position by the first service.

First time out, podium finish – or was it?

By the penultimate stage of the rally they were in second place with a comfortable margin. There was one stage to go and it was a bit of a nail biter. The whole team crossed their fingers hoping for a great result. Just one kilometer from the end of the rally the Impreza lost all drive at a hairpin. Unfortunately Tiana and Graham had to retire and that was the end of that.

Tiana and Graham secure in second place in their clubman rally car on the Winvale stages rally.

 Initially we thought it was to do with the transmission however it ended up being a broken drive shaft. We found that the shaft had broken at the outer cv on the right side. It’s a bit of an unusual one however that as they say is rallying.

Taking the positives of our clubman rally car build, nothing major went wrong. Our list is mostly improvements to the car. Unfortunately with the Forest rally so close, we don’t have time to do the panel and paint work. That will have to wait until mid season. Other changes include removing the ABS, fitting a hydraulic handbrake and minor under body protection mods.

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