February 2021

Calendar change

The Great Western Sprint has been moved, from March to October 23rd, so it will be the last round of the championship, if the championship runs. So the first round should be at Blyton in May, and Longton has said that they will be opening the entries system up in the next 7 to 10 days, so that'll be a mad scramble for places. I'll keep an eye on their events page to make sure I'm in with a chance of bagging an entry. There is likely to be some testing at Blyton before hand, but I've nothing to test this year. The car hasnt changed mechanically from the EcoBat sprint at Castle Combe last year, so for Blyton I can just turn up and drive.

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Alternator tested

I thought that the alternator would work under ECU control; it would, just not in the way that I'd wired it. I'd used the 12V signal from the Cartek Isolator as a pull-up, using a 3k3Ω resistor, with the X10 used to pull the line low when the alternator was to be turned off. But it just wouldn't work. It looked like the alternator needed a higher current on the IG pin than the 4mA that the 3k3Ω resistor was supplying.

So on Sunday I removed the resistor, and wired in a solid state relay, which connects the IG pin directly to the 12V wire from the Cartek isolator, and it started working properly. With the engine started the alternator is turned off until the engine has been running for 10 seconds (I can change that interval), and if the engine rpm drops below 750rpm, the alternator is again turned off, which acts as a helper to prevent the engine from stalling. If the battery voltage then drops below a set value, the ECU uses Recovery Mode, which forces the alternator back on until the voltage has risen above another threshold. Sounds complicated, but its going to be worth the effort of connecting it all up if I can free up a few horsepower.

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Alternator now under ECU Control

I wired the IG input on the alternator to one of the X10 outputs on Saturday, and rewired the knock warning LED on to a different output, though I didnt manage to test it to see if it still glowed. There's no rush. The alternator control section in the ECU is quite comprehensive. Lots of options to play with.



I also picked up a new crimp tool, this time for the battery crimp terminals. I'd bought one of those hydraulic ones previously, but they tend to muller the crimps, they put so much hydraulic force through them. This tool seems to work well with the test crimps I made on Sunday; I've a few long heavy duty cables to remove and replace with shorter ones, to remove more weight from the car.



Speaking of removing weight, I've dropped 3kg in the past three weeks, through exercise and diets. I've been on the exercise bike daily, racking up 25+ miles a day, and its paying dividends at the moment. My target for the first event, is to be at 80Kg. Only 7kg to go :D

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Knock warning LED

I tested the 12V knock warning LED by assigning it as an output when the up paddle is pulled, and the LED illuminates when the up paddle is pulled, as you'd expect. But when the X10 turns off the output to the LED, the LED still glows. I've wired it across the 12V supply, so the X10 turns the LED on by switching the output low. But when the X10 output goes high, or in other words, open circuit, there is current flowing between the 12V rail through the LED, which is why it is glowing. I've rewired the knock LED to use a different output, and I'll test it again tomorrow, just in case the output I chose (which I'd not used previously) is faulty.

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New X10 loom fitted

Over the weekend, I removed my original X10 loom, and connected the new one up. The first task was to swap the CAN bus cable that runs from the ECU, and then connect the power leads to the chassis supply. With those connections made, I plugged the loom in to the X10, turned the power on, and checked that the laptop could see the X10, and it could. Then it was a case of connecting the pneumatic solenoids, and checking the paddles still operated them with the clutch switch closed, and they did. The front wheel speed sensors were then connected, and the IO assignment changed to use the SLAVE inputs. This flagged up an error, since I had filtering enabled on the front speed sensors, and the X10 didnt support filtering, so I turned that off. I then connected the front and rear damper potentiometers up, and noticed that when I fully extended the potentiometers, a Voltage Limit and Voltage Failure error occured. I had the input type set to 5V, and changing it to Thermistor and changing the Default Voltage High to 5.0V (it was 4.995V), sorted the errors out.

Damper Inputs error messages


With the error resolved, these are the damper inputs all working


So I can now linearise the Damper inputs, setting the mm per mV, and I'll do that soon. I've wired in the 3 way Deutsch plugs to the rear speed sensors, and they're connected. The gear change warning buzzer is plugged in, as is the knock warning lamp. So I'm pretty much done. All thats left is to connect the alternator to the X10, via a 3k3Ω pull up resistor, and I can then run the engine and test that everything is OK.



I've also changed the gearbox oil breather outlet, from a banjo fitting and braided hose, to a 6mm plastic pipe, which looks much tidier. It needed an M10x1.25 to 1/8 NPT adaptor, which then allows the G1/8 fitting to screw in to the top.

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Date changes

Its looking more and more unlikely that the Great Western sprint is going to run in March, and due to the Pandemic, Longton has wisely moved the Anglesey date in April to the end of May. So it now looks like the first two rounds will be the Blyton double header in May, which would be a great way to start the season, straight in to a weekend event. And one of my favourite circuits too.

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