With the alternator installed and charging, the turbo and intercooling system in place, and the exhaust bolted on – it was time for a very gentle road test with the standard engine management.
The purpose of this test was not to assess performance, but to ensure that nothing was fouling (eg the exhaust banging on the bodywork) and that the car actually drove OK. I also wanted to get a feel for when turbo boost was developed, and I was curious as to how loud the car would be with the exhaust butterfly in a fixed, fully-open position.
I placed the MoTeC PLM probe up the exhaust so that a readout of actual air/fuel ratio was available in the cabin and then gingerly drove down the road.
It was soon apparent that the standard engine management was rev-limiting the car to around 3500 rpm. (Later I found that it was a problem with one of the cam sensors.) The air/fuel ratios were also very lean, even when still in vacuum.
However, the test showed that boost was able to be developed early – the number one requirement of turbocharging this car. In fact, in upper gears (and because of the lean air/fuel ratios, keeping the test very quick), a tiny amount of positive manifold pressure could be achieved just off idle – at say 1500 rpm!
Given that the Honda is geared very high (60 km/h in fifth is about 1400 rpm), having early boost will be critical to achieving high engine efficiency and so good fuel economy.
With the exhaust butterfly in its fully-open position, the exhaust was clearly much louder than standard – probably too loud for a car that I want to appear unmodified. However, that’s as loud as it will ever get – the butterfly would be expected to be mostly closed at these low loads.
However, this short road testing revealed that a problem earlier identified had not gone away - the accessory drive belt was again slipping at revs over about 3000. This was a major concern – hopefully, it was occurring only because the belt was a bit greasy.
So the initial test was largely positive – but there was no point in continuing driving the car with incorrect fuelling. Back to the shed and up on jack-stands… time to start wiring-up the MoTeC M400 engine management – well, that was my intention, but something stopped that in its tracks...
The next morning
The next morning was cold – minus 4 degrees C in fact.
To ensure that the alternator belt tracked nicely even when the belt was stiff, I started the car. But the engine ran for only a few seconds before a horrible noise came from under the bonnet.
I stopped the engine, lifted the bonnet and found that the alternator belt had shredded a rib.
No, the belt did not track well when cold….
Alternator mount problems
So despite the alternator mount having already taken me many, many hours of work, and despite it being powder-coated and bolted to the car, it needed to come off and be heavily revised.
Two problems existed with the design.
The first is that the alignment of the alternator pulley was not sufficiently accurate with the crank pulley. This seems very basic – and it is – but in the case of the Honda, it was very difficult to get right. The difficulty comes from the tight access and the closeness of the pulleys to each other – there is not sufficient distance between pulleys for the belt to cater for any misalignments.
The second problem – and responsible for the belt slip – is that the original design did not have sufficient belt wrap around the crank pulley. By adding a third idler, belt wrap could be improved. (However, note that the absolute degree of belt wrap around the crank pulley still remains smaller than on many cars.)
And, while the bracket was being heavily modified, three other changes could be made.
Getting the alternator bracket right
So the approach that I had taken when originally building the bracket had not been sufficiently accurate. When making the first iteration, I’d used a long straight edge to line things up. This time, I made a specific ‘stepped’ timber gauge that catered for the differing pulley designs of the crank and alternator (there are different thickness of pulley material outboard of the grooved parts in the two pulleys).
I also discovered a simple technique that showed even tiny misalignments. The technique was to have the belt quite loose and then push on the belt (rather than pull it) to move it around the pulleys. Any lateral misalignment of the alternator (even 1mm) would cause the belt to slightly ride up one side of the pulley or the other. The same approach was also effective for the flat idler pulleys - if they were not exactly square to the belt, the belt would move from the centre to one side or other of the idler. Note that the behaviour of the belt changed, depending on the direction of movement!
The main alternator mount was revised to better improve the alternator pulley alignment – embarrassingly, it was out by 4-5mm. This revision involved the modification of the spacers that set the lateral position of the alternator. In addition, the lower part of the mount (that originally bolted to a sump bolt) was removed – this bolt would now help locate the new bracket for the third idler.
To give better clearance to the oil drain from the turbo, the alternator mount in this area was completely revised.
A triangular-shaped member (arrowed) was constructed that doubles in duty as a stiff exhaust brace. Two parts of this brace bolt into place, allowing the brace to be fitted around the oil drain hose without the hose having to be first removed.
A completely new bracket was made to mount the third idler – the one that improves crank pulley belt wrap.
There was insufficient clearance between the belt and the sump to mount the bracket behind the belt, so it mounts on the outside of the belt. Initially I was concerned that this placement would mean that the bracket and idler would need to come off whenever a belt was fitted, but by contouring the bracket to match the shape of the crank and air con pulleys, a belt can still be fitted (or removed) with the bracket and extra idler in place.
This bracket is located by two air conditioning compressor bolts and a single sump bolt – all are 8mm in diameter.
Despite the addition of the new idler, the belt (5PK1375) used in the previous iteration can be retained – the factory belt adjustment idler is simply moved in its slot a shorter distance to tension the belt.
So with the alternator bracket finally finished, it was time to again turn attention to the engine management.
New engine management
Despite having done a lot of electronic car modification over the last three decades, I’ve never wired-in a programmable management system. Given this, I certainly didn’t think the installation of the MoTeC M400 was going to be a doddle.
However, looking carefully at the MoTeC literature (the company provides excellent resource material – scour their website), it appeared that the following input sensors would be straightforward to connect and configure:
Each of these was supplied by MoTeC and can be relatively easily configured in the ECU Manager software, with predetermined templates existing for each of these sensors.
The factory Honda throttle position sensor also looked straightforward to connect and configure.
However, the crankshaft ref and camshaft sync signals looked much more complex – especially in configuring the ECU to understand them.
On the output side, the injectors, boost control valve and EGR valve looked straightforward.
Again, though, there were some outputs that appeared more difficult – powering the factory ignition modules and factory idle speed control valve, for example.
So I decided that for me, step #1 would be to wire in the following:
Each of these could be connected, the ECU Manager software used to configure the input, and then the sensor tested before going any further.
The wiring approach
When wiring-in programmable management, two different approaches can be taken.
I chose to do the latter, primarily because that meant that new plugs didn’t need to be sourced for all the factory inputs and outputs that were being retained. (The new loom could have been spliced to the old near each plug, but that puts wiring weaknesses in the areas of high vibration, ie the engine bay.)
To make the correct connections, I used this information:
To ensure that (a) I had a record of the wiring configuration and (b) it was less likely that I made mistakes, I used the following type of table that I marked-up as I went along.
The installation of the intake air temp, engine coolant temp and throttle position sensors went fine.
The MAP sensor (a MoTeC-supplied 3 Bar GM sensor) caused me a minor issue - I stuffed-up the crimping of the terminals in the plug. Rather than buy another new replacement, I sourced the MAP sensor plug from an old Holden Commodore and modified it (adding a few little slots) so that it would connect to the 3 Bar sensor.
All this went well so, full of confidence, I started on the injector and ignition wiring - only to almost immediately kill an ignition coil…. Aaagh.
Next: installing a new ignition system, and developing a new electronic interface module for the cam sync sensors