Neil, DI does not allow more time to inject fuel. Actually the opposite because the fuel should be injected only between the end of the exhaust stroke and a little before the top of the compression stroke. Whereas, with port injection, you can inject continuously throughout the full 4 strokes. As you know, with CIS, fuel is injected continuously into the ports, even at low throttle. With EFI, the injectors open and close: at low throttle, they are closed more of the cycle than they are open, but at full throttle, they approach open 100% of the cycle, so it's like CIS at WOT.

Some manufacturers have recently employed both port injection and DI together to get the advantages of both systems, particularly for engines with variable turbo vanes and multiple turbos. That level of complexity scares the crap outta me. :eek:

Complexity does not scare me as its a opportunity to learn. It should never be
taken for granter though.

I'm looking at port injection as a start. It makes it a little more simple to build. I have no idea how it will work as I have found no other application of just high pressure port injection. I do lose the opportunity to inject into the chamber when the Inlet Valve is closed where as DI can continue.

My hope if this is successful is to raise the CR number and lower the knock level.

We have conducted some tests over the years and found that even with current EFI, the mixtures are not a very homogeneous mixture. Low pressure and the turn that the air has to make in these engines works against a good mix. This is why we see a lot of residue fuel droplets on the runner walls that become part of the fuel entering the chamber but not part of the programmed injected amounts. Common issue with most engines not just Porsche. However the Porsche "turn" is one of the worse.

If the higher pressure helps lower this effect, it should result is some level of performance gain. If I can raise the CR number this hopefully will allow these older engines to survive and make more power.

A lot to do still. The list grows every day. Starting to assemble the parts required and the more we accumulate the more we find we do not know.

I don't mean literally that complexity "scares" me, but it does cause me a lot of concern for more crap to go wrong, harder to figure out problems, and opportunities for Murphy to get involved. One of the reasons I drive an olde air-cooled 911 is that it is dirt simple, and I can fix anything on the car, or even make new parts if I have to. Not that I have to, because virtually every part is available from OE suppliers or aftermarket.

DI does offer the possibility of higher CR's. My wife's former 2009 Cayenne S had the DI V8 engine. It also had the alusil block cylinder failure. In troubleshooting why I was burning oil in two cylinders, I found that the compression test was so high that I had to use my diesel compression tester. The test numbers were in the range of 285psi! That works out to a static CR of almost 20:1. I later found out that the dynamic CR is much lower, and it's managed by changing the valve timing through the cam timing phaser.

Also for DI, the injector location, angles, combustion chamber/piston shapes have been developed through lots of R&D by Bosch and the vehicle manufacturers. If you decide to use DI, try to copy what has already been developed by the manufacturers. Plagiarize shamelessly!

The first application will be port injection with the Injector placed like the new ITB runner shows. I will see what challenges that gives me. One step at a time.

A wise approach.