PI tuning

My initial elation at getting the GT6 running on Pi was dampened somewhat when I realised that the rough running was accompanied by the exhaust from number two cylinder was glowing red. Something was obviously not right, so I gave the supplier of the exhaust manifold and metering unit (Gareth Thomas) a call and described the symptoms to him. He reckoned the timing was out and offered to pop over as he was in the area and check it out.
Later GT turned up and after much checking and re-checking of the camshaft, we had proved that the camshaft was approximately 10deg. too advanced. With the timing cover off, the marks on the cam wheel lined up correctly, but the cam opening were not correct. The cam wheel was a second hand duplex version, bought from eBay some months ago, which I had no reason to think was machined incorrectly, but it turned out that it has never been right when we compared it to another cam wheel I had found.



Eventually, after much checking, the cam wheel was re-fitted rotated round from where it was, along with a second hand chain to give the most accurate timing possible.

So a few hours after starting on the car we had it running something more like properly. No.1 injector needed bleeding, but was soon done and then it was on to the finer settings, once a throttle return spring had been fitted it was much easier to set the idle and then on to balancing the manifolds. A quick run out that evening showed a massive increase in torque and power, with some beautiful sounds coming from the exhaust and a wonderful howl when working hard.

The next day the air box log was fitted, it was much to my surprise that it fitted at all as I had not modified the bulkhead with that in mind. Then it was onto the ignition map, which we made surprising short work of, modified quickly in the shed before going out for a run. The new map cured the un-even idle, a stutter around 2000rpm and having increased the highest rev range, it no longer failed to go over 5500rpm. Out on the run the map was changed while in the petrol station, amid strange looks from other people, further refining it.



I then took to the passenger seat to let GT have a feel of the car, really worthwhile as I had been having some issues with how the car felt, but my lack of experience made it harder to define what the problem is.
One problem, which I knew of, is down to the lack of negative camber on the front, something which I would like to remedy with a pair of top arms from GT6Mike, but for now I shall see if I can get a few more shims in. Another suggestion is to increase the rear track width to make it more stable under braking, as at the moment the front does feel a bit too light and fidgety under heavy breaking.

All of this now gives me a further list of jobs to do, get some more camber on the front, fit a cold air feed to the inlet and seal up the gearbox tunnel.

Oh, and these a the plugs after a good run out.

On with the GT6 PI install

It took a bit longer than I had hoped but I soon got the inlet and exhaust manifolds on. It took longer as I needed to try different fixings for the manifold to enable me to both get the bolt in and tighten it up, so there is both nuts and cap head bolts holding it to the head

Next it was on to bracket for the throttle cable, temporary at first to check the movement before welding it together.



With the manifolds all on I could connect up all the hoses, but no fuel was getting through to the injectors and the battery soon ran down, so that had to go on charge. I was not sure if the injectors needed to be bled, the PRV was set too low or just that the battery is too low.





After a quick call I soon found out that the fuel system needed to be bled through the injectors by turning over the engine with the spark plugs out, excess fuel on full and the injectors out of the manifolds, which all makes good sense really, so to reduce the load on the starter. Such are the problems of trying to undertake a job such as this on your own with no previous experience on the Lucas PI system.

With the system properly bled through I did manage to get the engine to run on the Lucas PI system, albeit somewhat roughly as the throttle bodies had not been balanced and the tick over not set, but at least it ran, so I was happy enough for that days work.