Work on the car has continued. Since covid hit we’ve been busier than ever at Goodwin Racing (a good problem to have) and that’s meant that with the little spare time I have it often comes down to whether I want to use that time to build the car, or write about it… and I’m determined to finish this thing up and get back to the track, so it’s been head down and getting after it for the past year.
There’s a lot of updates to make, so to keep things digestible I’ll break it up into smaller chunks and do those updates over a little time here.
First, the fuel system. The plan is to get rid of the factory GM ECU since that’s proved to be a limitation in tuning the supercharger. But most aftermarket ECUs can’t run direct injection. And the DI system has been a source of headaches in trying to get enough fuel for the supercharger anyways… so I made the decision to go the hard route and completely eliminate the DI by converting the engine to a more traditional port injection format.
Thanks to a discovery made by one of the other LFX swapped guys over on Miataturbo.net, we figured out there was one piece to this puzzle already available from GM; a lower intake manifold that already had injector ports in it. I got my hands on one of these, but that’s where the easy stuff ended. Fuel rails are needed.
First mock-up of that manifold on the LFX, and in the picture I’m already starting to plan out rail placement:
With this new setup, I’ll be running 6 x Injector Dynamics ID 1300x:
Had a little back and forth with the guys at ID to sort out the exact combination of top and bottom o-ring sizes plus a small spacer to get its placement in the manifold just right.
Due to the port placement, the rail has to be a few inches away from the injector, and at a different angle. This means the rail needs “fingers” that extend to the injector. The fingers need to be precision sized at both ends, bent at an angle, rigid, and also need to seal to the rail. This lead me down a whole spiral of researching the mechanics of o-rings and seals so I could design this to seal properly, and then figuring out how to make the necessary multi-piece design.
Some progress shots:
Pressure testing:
Polished and anodized:
And that’s a finished set of one-off fuel rails test fit on the spare motor:
This can now be fed by a normal fuel supply system at normal fuel pressure. FPR will be mounted on the back of the motor near the rail and then split to both rails. And this will now be a return system with return line exiting the rails and going back to the tank.
I just need to make a couple lines and the fuel injector wiring sub harness and then this will be installed on the main engine in the car.
Oh, and the DI ports in the head were drilled/tapped and plugged, and the port on the back of the motor for the high pressure mechanical fuel pump was capped:
