After a loooong interruption without pulling, on the weekend of September 4th and 5th we got the possibility to set our tractor in front of a sled for the first time. Having confirmed our presence at the pull already mid of July, there was plenty of time to get everything ready … well, no.
After the trouble with the driveline, we were pretty confident that we could complete all the small tasks left in no time. But as usual everythink takes longer then one expects. Having planned to fire the tractor up, for the first time in nearly two years, in the beginning of August we were only able to do this on friday, August 27th, one week before we were supposed to load the tractor. Up to that point we had still a lot of parts to do or complete. Two major challenges were the rectifying of our exhaust header flanges and the construction of the turbocharger protections following the ETPC rulebook.
For the rectifying of our exhaust header flanges, we thought to just bring them to a specialized engine building shop … well, no, they didn’t feel comfortable to complete that task. So it was again time for a homebrewn solution and finally time to build the flycutter I had in my mind for a long time 😎
Building the turbocharger protections was one of those tasks we kept on pushing ahead of us, because we had an idea of the amount of time we would have to invest. With some homemade and improvised tools, we were able to realize some neat sheet metal protections.
Around 40 screws for every side and we were just missing the inlet protections, which should keep any compressor parts from exiting the turbochargers in case of a turbocharger failure. Only two weeks before the first pull, there was no time for ordering laser cut parts. Time to teach our old one-armed friend CNC plasma cutting.
The results were very satisfying for a firts try, weld everything together with a steel grid of the right size, to fullfill the ETPC rules, some paint for everything and it looks pretty good.
To get everything working, some care had to be taken about our electrical system and the safety circuits needed implementation. Machining an emergency shut down switch for the rear of the tractor, some control buttons and lights as well as the reverse lights on the back of the tractor and next to the driver. The rulebook asks for a bright white light, I think we got that sorted out … poor sled operator. On top of the engine we installed two alarm lights, which have a freely programmable trigger from the datalogger for any channel.
Furthermore we build a catch tank for the engine breather, a new oil tank with integrated check valves for the hydraulic steering and a locking mechanism to lock the forward gear in the gearbox to avoid any trouble when the gearbox would jump out of gear.
The final engine test approached fast, which meant we had to clean and reassemble our homebuild oil filter.
Only one week to go, we had a lot of problems to restart our engine. We didn’t change anything on the ignition or fuel system since the engine ran in September 2019, so these problems came somewhat unexpected.
The engine was running with a lot of vibrations and the noise already suggested that some cylinders were not running properly. A quick look on the exhaust gas temperatures showed 4 cold cylinders, so the engine was just running on half the pots. It smelled like we had fuel on all cylinders an the spark plugs fired on all 8 cylinders. We concluded that there must be some strange issues with the ECU, which, due to limited ressources, was running the engine only in wasted spark mode. This means that the ECU thinks it is running a 4 cylinder engine, but we are always injecting fuel and igniting on two cylinders at the same time. Since one of those cylinders is in the compression stroke an the other one in the exhaust stroke while igniting, this is a pretty common thing to do on inline engines.
Never really happy with the wasted spark solution and having an ECU upgrade on the desk since some weeks, to control every cylinder independently in a full sequential mode, the decision was made to go for the ECU upgrade instead of working through possible errors on the old ECU. The new ECU ist running an STM32F4 microcontroller with rusEFI firmware.
On monday before the pull, only 4 days before we should load the tractor, everything was in place, all trigger setups made and settings from the old ECU system tranferred to the new one. The first starting attempts only resulted in really noisy “plops” and “poffs” and we had no real clue about the major problem. After a reversed polarity on the main trigger sensor was detected and changed, the “plops” and “poffs” suggested that the engine wanted to start, but something was missing.
In the meantime (on late Tuesday), the word spread from other teams (thank you Sascha) about stuck fuel injectors. First thing on Wednesday morning, get all injectors out for testing and disaster struck again … 12 out of 16 injectors death and no way to get them unstuck. Wait, only 4 good injectors in the engine, magically all on 4 different cylinders … this explains the rough running engine on 4 cylinders on friday night.
The 4 good injectors left were directly vitalized in an ultrasonic bath with Diesel fuel and while cycling them in that bath, a lot of black soth came out of them. We had a reserve of 4 injectors, so we basically had one good injector for every cylinder. On Wednesday evening we put 8 good an 8 bad injectors on the engine, adapted the settings in the ECU on only half the fuel flow and the engine fired right up.
We used the Thursday to complete our drivetrain and install a clutch pedal. On Thursday evening we wanted to bleed our steering and brakes. It was impossible to bleed the brakes and they were without any noticable function. Disassembly of the master brake cylinders reveiled that the used hydraulic fluid (we didn’t see the need to use proper braking fluid) had dissolved the seals. With a Friday morning on the phone, we were able to order two new master cylinders for friday afternoon. So there was some chance that we could load up the tractor on friday evening … but wait, we want to run a limited class and therefore air restrictors are needed. The aluminum to machine these was already ordered three weeks ago, but got never delivered 🤬 … time for another phone call, and by 3PM the machining of the air restrictors was going on.
By 6PM everything was ready for a final test. The tractor was never fired up with the complete drivetrain in place, nobody knew if the gearbox and clutch would work … fingers crossed. It seemed that the first time in a week we were lucky, everything worked perfectly, we made some meters back and forth out of the workshop and the tractor was ready to load for our first pull.
You can read about the adventures to and on our first pull in the next episode … stay tuned.