Update on EFI Project
You all thought this was over………no, it is still ongoing.
The system has been in operation now for a few years and overall has performed well. About 6 months ago I decided to tidy up my wiring loom a little. Ever since then, I had some irritating tach signal problems that caused my ignition advance to wander. The engine still ran OK but was not as sharp as it should have been.
About 8 weeks ago I decided that I would find the problem and fix it. Well, to cut a long story short, I elected to update the set up to go wasted spark and semi sequential injection. This entailed fitting a toothed wheel and sensor to the crank, some internal mods to the ECU, fitting new coils, removing the distributor, and some wiring changes.
I had some issues with the fan control on the ECU so I sent it off to a contact in the USA to fix and modify. The mods were not major but as it was there, I got him to do it and this also gave me ready access to good advice on the project. I had a spare ECU so I could still use the car.
Next I had to find a suitable timing wheel. With EFI, you have to tell the ECU what is going on with the engine. To calculate the engine speed, it reads the timing pulses, measures the time splits and calculates the RPM. From this it calculates the next ignition event based on the last event. When you use a distributor to provide the pules, the ECU only gets this information every 180 deg of crankshaft rotation. So when you are accelerating, the timing information is 180 deg old by the time the ignition occurs. As the engine speed has increased, the ignition will be a little later than the optimal. With a distributor based ignition system as is normal on a TR, this is not a problem as it is connected to the crank and always knows what speed it is doing but with EFI it is an issue.
Now with the mighty TR fitted with EFI, this problem is not great as it does not change its RPM that quick but it still exist. After much searching through Pick’n Pay wreckers, I decided on the wheel from a mid 90s Daewoo Lagansa. It is a 60-2 wheel. This means that it has nominally 60 teeth but with 2 missing. With 60 teeth, the ECU will get the speed and position information ever 6 deg of crank rotation, much better than every 180 deg. The two missing teeth provide the ECU with a marker on crankshaft position. This meant that I no longer required a distributor….more on that later.
The wheel on the Daewoo is part of the harmonic balancer/pulley. I was able to cut the wheel off the balancer and machine it to fit the Holden balancer I use on my engine. As you can see by the picture, it fits very well and looks like it was meant for the job. Three screws through the puller holes on the balancer are used to retain the new wheel to the inner element of the balancer. Due to the mass of the wheel, I was concerned that these three screws would not hold against the torsional vibrations of the crank. To handle these torsionals, I fitted six pins to prevent any relative movement between the balancer and the wheel. Once this was done I mounted the assembly in the lathe and gave the outer rim a light skim to ensure it ran true.
Much to my relief, this modified balancer fitted perfectly and required no modifications to the timing cover area of the engine. Next I fabricated an aluminium bracket to mount the VR sensor, also from the Daewoo. All this of course required the front apron and radiator to be removed. Once the new wheel and sensor was fitted, I refitted the radiator so I could run the engine. It was still set up as before and nothing I had done prevented it from running. All I had done was to fit the timing wheel and sensor.
With the engine running I was able to check the output of the sensor with an oscilloscope. As you can see by the picture, it was very good. You can see the regular pulses of the teeth and the major pulse as the two missing teeth passes. By this time my ECU had returned from the USA and I had hoped to have it ready for the National meet in Toowoomba. I refitted the front apron as all the remaining work was nowunder the bonnet.
The next step was to set up the wasted spark ignition. Most cars these days run either wasted spark or coil on plug ignition systems. With coil on plug, there is one coil for each plug and the ECU can control the ignition for each cylinder independently of each other. With wasted spark, there is one coil for each pair of cylinders, both controlled by the ECU. That means on a TR there is one coil for number 1 and 4 and one coil for number 2 and 3. So when number 1 fires, number 4 also fires. This is not a problem with number 4 as it is at the end of exhaust stroke and the spark is only ‘wasted’, hence the name ‘wasted spark’. The same applies to the other cylinders.
It can be seen therefore that as the ECU controls which and when each coil fires there, there is no longer any need for a distributor. Unfortunately, sourcing suitable coils took more time than I had so I reprogrammed my original ECU ( I have two) to run my old set up but use the new timing wheel to provide the timing pulses With this set up the distributor is still required. It improved the cars running and that is how I ran it to Toowoomba.
On returning I started back into the coil problem. I elected to run two Holden Commodore V6 coils (they run wasted spark). Next, I required two trigger modules. The ECU can not fire the coils directly and require a trigger to do this. These are available new for around $80.00 each and as the full Holden coil pack only cost $40.00, I returned to Pick’n Pay and found suitable triggers on a Nisan Pulsar. These were only $10.00 for the pair.
With the Holden coil pack, it contains electronics required in the GM system and has three coils. I was able to modify it by removing the third coil, the electronics, and one third of the mounting plate. The new coil pack and triggers were then fitted to the LHD steering cover plate on the fire wall behind the wiper motor. See the pictures of the fitted system.
Next I removed the loom and modified it to add two ignition outputs, wire each injector separately and include the new VR sensor for the timing wheel. With all this in place I downloaded the new software required to run the system and programmed the modified ECU to run wasted spark and to go semi sequential injection. Semi injection means that the injectors are fired in pairs just as the coils are and they can also be timed.
First crank and away it went……surprise .. surprise.
Before, I had to idle it at around 1000RPM but now it idles at near 700 RPM. The low RPM performance is much better and the engine runs much crisper. I am off to WakefieldPark next Wednesday so it will be interesting to see how it performs.
Update….WakefieldPark. The trip down went well and the car sounded and felt good. For the practice session, I set up my lap top to log the engine parameters so that I could check the engines performance. The air fuel ratio was my main concern. During the session, the engine would not rev out past about 4000RPM. Back in the pits I checked out the data log and it showed that the engine was running so rich at high power settings, that it was putting the fire out. I changed the fuel map by pulling a lot of fuel out of the high end of the fuel map.
For the first event, I set up the programme in the lap top to automatically change the fuel map to achieve the air fuel ratios I had nominated. On the first lap the engine still was not happy at the high end but was much better than the practice session. As the event progressed, the engine went better and better until at the end, it was great. Over the course of the event. the automatic programme pulled more fuel out until it gave the mixture I had nominated. During that session, I put in my personal best for that circuit.
For the remaining two events I just let the engine do its thing without any input from me or the lap top. All in all the car ran well and after some more tuning at home, I now consider that the system is completed.