ECU and Electronics

Engine Management.

The cars engine management is centred around the new TECgt ECU. This replaced my previous TEC3r which had previously replaced my old FM Link ECU. The move to Electromotives line up of engine management was due to my desire for additional timing accuracy and the high energy coils offered by the TEC3r and TECgt, also the mapable outputs to allow the addition of water injection and, in the future, maped nitrous were appealing.

For tuning the car I use DataLogLab or DLL for short. It is capable of repeatable torque and power graphs that make it as useful for tuning a car as a rolling road and if the required input data is accurate it produces accurate power and torque curves - in my experience to within +/-5bhp of a good dyno.

I'll be putting up some tuning tips and such things as fuel, ignition, WI maps etc as soon as I get the time.

Crank trigger wheel and sensor mounting setup. Setup is the same for all MX5 motors except the early 1.6L. The oil pumps on the early 1.6Ls were different, but as far as I know the later oil pumps can be retrofitted. Now replaced with ATI Superdamper setup.

Note the silicone pipe protecting the sensor cable, this has been done after the engine threw an accessory belt and damaged the the magnetic sensor cable in the process. The sensor has since been replaced, but after that incident it seemed sensible to offer the cable a bit of protection. The silicone pipe is a bit make shift and I'll get round to doing something more permanent soon.

I often get asked what injectors can be used in an MX5 install. Here is a shot of two low impedance fuel injectors. On the left hand side is an RC Engineering injector, rated at 550cc per min, this one fits the MX5 fuel rail. On the right hand side is a Seimens, Bosch style, low impedance injector, this one does not fit the MX5 fuel rail.

Low impedance injectors are preferred to high impedance injectors as they respond faster to ECU signals, in other words the time taken to open the injector is shorter and this has an impact on the minimum on time of the injector. High impedance injectors have a minimum on time around 1.2 to 1.3ms, vs the low impedance injectors MOT of about 0.9 to 1.0ms. Shorter on times lead to poor injector control. Important for achieving a stoich, emissions friendly, idle with big injectors.

Aquamist Water Injection.

I have never liked having to run rich fuel mixtures to slow the burn down and prevent pre-ignition, so in the quest to run more sensible air fuel ratios on boost I installed an Aquamist 2C water injection system. The system 2c is designed for use with third party Engine Management Systems, such as the TECgt that I am running. The kit provides all the necessary hardware to interface with one of the TECgts PWM output signals, enabling full 3D mapping of the water injection. I am running a 25/75 ratio of methanol to water. Further benefits of the water injection is additional intercooling of the intake charge and in cylinder cooling, both of which allow timing to be advanced closer to or to MBT (Minimum (spark adance for) Best Torque)).

Aquamist water jet/atomiser. This is a 0.6mm jet, good for about 250cc per min at 7bar water pressure and 100% duty cycle. The TECgt has made it easy for me to carry out a number of flow tests on the nozzles at different duty cycles, I'll put them up soon as well.

Fuel Pump Modifications.

With the aim of getting 400bhp from the new 2 Litre stroker engine I decided to carry out a Fuel Pump rewire to get as much from the stock pump as possible. The stock pump can happily supply enough fuel to make 300bhp at stock fuel pressure, possibly more, but to maximise it the fuel pump rewire is designed to reduce voltage drops in the wiring caused by the rather skinny stock wires and, hence, minimise the voltage drop at the pump. The higher the voltage that the pump sees, the more the pump will flow. The pictures below show the modifications made to the wiring.

The install requires the use of a relay - this is triggered on the low ampere side by the stock fuel pump +12v supply. On the high current side of the relay you install a fresh ground and power supply to the fuel pump, with thicker gauge wires that are as short as possible. Don't forget to use a fuse.

One point to note is that no soldered joints are used - these attract corrosion, and where the stiff soldered part of the wire ends can lead to fatigue failure. OEM manufactureres do not use soldered connections for these reasons - good crimps are much more reliable.

If you MUST use solder, cover the connection with heat shrink insulation, this will help to support the connection and move the main stress/flex points away from the soldered joint to a part of the wire that is still covered by the original wire insulation.

The results of the modifications were as follows (figures for a standard setup are in brackets):

Voltage at battery - 14.36V (14.40V)

Voltage at fuel pump - 14.27V (13.73V)

Additionally, when the fuel pump is at full flow the voltage drop is likey to be larger than the values above (which were taken at idle), so even more of an improvement will be apparent. Cliff Knight from the Miata forum has provided the following current draw estimates: "The stock FP draws just a tad over 11A at 13.8V and deadheaded, 8A to 9A at normal volatges and loads. It does have an inrush that's difficult to measure but I'd guesstimate it averaging 18A or so for the first 250 mS or so."

Terminal for the weather proof connectors - using a proper crimp connector is good practice for reliability. Do NOT use solder, solder will tend to attract corrosion and will, in time, lead to fatigue faliure of the connection. This will happen as the section of wire with solder soaked into it will be rigid, whilst at the termination of the solder the wire will still be flexible, it's at the join between the rigid and flexible parts fo the wire that fatigue faliure will occur. If you don't beleive me, have a look at your OEM wiring loom, you will not find one soldered connection and the reason for this is reliability. OEM may like to save money, but not at the expense of reputation damaging poor reliability.

ATI Super Damper install.

I've been planning on installing an ATI Super Damper for a good while now, just needed to find time to do it as, on my engine, the install is complicated by the need to mount an Electromotive trigger wheel to the back of the damper and fabricating a mount to install the magnetic sensor. There are a number of benefits to installing an uprated damper on my engine, increased crank bearing life, less timing scatter due to reduced crank twist, more power etc, but the most important to me was insurance against oil pump gear failure when turning the boost and/or rev limit up. The install went as expected, IOW it took about an order of magnitude longer than expected. Some comments on the install:

• Machining the EM crank trigger wheel was difficult. The material was tough and the wheel wanted to flex as the inner radius was machined down to the thickness of the stock Mk2 wheel. This was overcome by placing a spare EM wheel behind the one we were working on to support it.
• The bolts (allen head recessed type - see image in install album) were too short once the trigger wheel was sandwiched between the damper and the cambelt guide. You will need to obtain longer ones. They are imperial, so tough (impossible??) to find over here. I was lucky, Ferdi (known as ftjandra on miataforum), kindly sourced some 3/8" long and sent them over. Perfect - just needed 1mm taken off the ends to get them the correct length.
• The cambelt guide is pushed back by the depth of the stock trigger wheel (about 1.8mm IIRC). This means that the gap between the front belt guide and the back belt guide is too narrow by approx 0.8mm and the belt guide needed to be relieved by 1mm. Makes me think that I was sent the wrong damper, despite being assured that the Mk1 and Mk2 ATIs are identical.
• The FM 2L stroker crank has a radius machined in it where it steps from crank nose (the bit the pulley is pressed onto) to the crank shaft proper. The stock crank does NOT and this required a similar radius to be machined into the rear mount of the ATI belt guide.
• Once mounted the ATI is very difficult to remove. It calls for 1 thou' of interference on installation, but the 2L crank offered 2 thou'. One would need the puller that ATI supply to remove it.
• Unfortunately once the ATI was pressed on (no going back!) we discovered that the point where we wanted to mount the magnetic sensor just fouled the alternator belt. This required moving the sensor mount slightly from where we planned it and the sensor now aligned with the 8th tooth at TDC No. 1 rather than the 11th. i.e. the timing would be approx 18 deg retarded (turns out it was 16). This needed correcting in the software.
• Lastly you need to be aware that ATI Super Damper has identical diameter belt guides (139.7mm) where as the stock dampers alternator guide is 145mm in diameter and the power steering belt guide is 129.8mm in diameter. The stock belts do just fit (alternator too long and the power steering a little short), but ideally you'll need to get shorter and longer belts respectively.
• Note also that I replaced the cambelt and pulleys while in there. I changed the cambelt to a Gates racing belt - it's claimed to be 300% stronger etc and will hopefully last longer (see I already don't want to pull that damper off...).

Here are some pictures of the install. I'll add more later.

Note that I also replaced the campulley bolts with titanium versions, partly because they are shinier and lighter than stock but also the washers are concentric and don't make the campulleys look like they are wobbling when the engine is running... The bolts are M10x1.25 and 35mm long (measured from under the head). The washer is 30mm OD and 3.25mm thick. I initially ordered these bolts, but when I came to install them they didn't fit due to the unthreaded section (the grip) being too large diameter for the threaded camshaft. The actual OEM bolts used are just that; threaded bolts. In the end I bought these, 5mm too short, but the washer used is only 1.6mm deep, so really I have just lost 3.4mm, just under 3 threads. I'll be keeping an eye on them but don't expect problems. BTW if you are wondering about that washer - I had the centre drilled out to 10mm...

Impressions....

Well so far very good, the engine is definitely smoother (although still a 4 pot!), to the extent where I can feel additional road information through the steering wheel (I have Mazda Competition engine mounts) due to the loss of the engine vibration. On blipping the throttle I do not get the vibration in the PS belt as I used to (a bit like a guitar string being plucked) and the engine does not feel so harsh when held at high rpm and low load. I have not had opportunity to play with timing yet - I doubt I'll see the improvement that others have as the 60-2 tooth EM trigger wheel is mounted directly to the crank and about as good as you can get. Still I'm hoping for a little bit of additional timing here.