Project Gemini Update

Ok, so since I have this week off, I’m working on the Gemini since it’s such a priority to get it on the road at the moment. Today Bob and I went to a wrecker and found a nice bosch throttle position sensor - three wire, good mounting and D-shaft actuation - the one that Repco had for ~$100 or so. That didn’t come with the plug and wires, nor any idea of how things worked with each other. So, that was free - all I paid for was a bunch of sweat and an energy drink after wandering around in the wreckers for half an hour or so - damn it was hot today.

I did a bit of work on the fuel rail, and the injectors sit nicely in it now, once we have the right o-rings it’ll be sweet. I drilled out the injector bosses to 12.5mm with my handy-dandy drill press, so all is good on that front. I had to sand the plastic on the top part of the injectors (where they sit in the fuel rail) so they would fit, but that was better than taking more metal out of the injector bosses as they are down to about 2mm thick now.

The coolant temperature sensor I’d gotten for the first manifold I was going to use was still in the old manifold, and I hadn’t actually found anywhere to screw it into the new manifold. Luckily enough for me, there’s a threaded hole on one side of the coolant run through the manifold that fits the sensor perfectly - doesn’t even need the adaptor I had gotten to fit the sensor originally. Bonus for me!

Once that was done, we worked out how many of the “Bosch Style” plugs we needed, and hooray, I hadn’t lost enough to mean we were short - one for each injector, one for coolant temp, and one for the Bosch Idle Air Controller, which I may hook up later.

So the fuelling’s going to be all good soon (hopefully) and the ECU will know how things are going, so where next did we go? Big Dad’s Pies for some snackage. Hey, we needed food! All that work had left us hungry 🙂

After scoffing some pies and being thoroughly happy with that, we were back into it - I got the bolts in for the starter motor, and I think we’ve got all the right bolts in the right spots for the gearbox now, nothing more to do on that front.

So, that was the end of the day - by that point it was about 1600 hours, and time to go home to beat the traffic (we didn’t).

So the next step is to get the injection manifold bolted on - that’s going to be interesting, since bolts won’t work because of how close the head is to the brake booster, and for the same reason longer threaded studs won’t either. I think what we are going to have to do is use LONG studs, square off the ends of them and have them sitting in the manifold so that some bolts can be put into the bottom, then the studs worked into the head, then nuts over the ends of them to tighten the manifold to the head.

Once that’s done, I’ll make a little plate to hold the throttle position sensor in the right spot, since the holes on the throttle body don’t match the ones in the sensor - that should be just a case of a few well-placed screws and washers, and a 3mm thick plate of aluminium.

After that, making the engine bay loom for the wiring - I want to keep it relatively nice. Two circuits for the injectors, a run for coolant and throttle position sensors, a signal wire for RPM, I’ll have to work out how the air box is going to work, then the wiring should basically be done for the engine bay. Things like the dual fuel pump relays - two pumps, a relay for each - and the priming setup for the low-pressure system will be done as soon as I gt the wiring in order for them too. Then it’ll be time to work out how the Gem’s wiring works as far as things go with power for the ECU and re-wiring the ignition setup.

I guess I should explain the priming system on the low-pressure side. When you turn on the MegaSquirt, it gives a ~2 second pulse to the fuel pump and stops if it’s not seeing sufficient RPM by then. If it does, then it’ll continue to supply power to the pump relay - if not, it’ll shut off. This is fine to prime the high-pressure system, and prime the injectors ready to go and have proper pressure for starting.

Since I’m running a low pressure pump to a surge tank, then a high pressure system only in the engine bay, there may be a condition where the surge tank has drained itself sufficiently (say if I leave it for a week or so without running it) that the high pressure system won’t be able to fill itself and have full pressure by the time you go from off to on to start. What I’m going to do to stop this sort of thing happening is to have a button - either in the engine bay or in the cabin - that will allow me to manually activate the low pressure fuel pump only. This will mean that it’ll prime itself, then push fuel through to the surge tank to fill it, thus pushing any and all air out of the lines - at least on the low pressure side. Hopefully this will allow the high pressure system to only have fuel to pull through, and no issues with cold starting will happen. Hooray!

Anyway, nothing to do, too much time to do it in, or something - I’m off for now!