Step 1: Pick your engine well.
Probably the biggest factor is simply whether or not there's spacer for the injector bung under the intake port. If your target head doesn't have that, you're done; pick a different engine. Also, 4V chambers have better geometry for DI than 5V chambers, as OEM's building 5V engines (Audi, Ferrari) went back to 4V chambers for DI. Of course GM's new DI V8's use 2 valve chambers and seem to be pretty impressive at making power.
mk e wrote:
apalrd wrote:
.....and the only DI advantage to that is in-cylinder cooling for improved knock.
There's more to it than that for production cars. being able ti time the fuel to start after the exhaust valve closes allows them more freedom on cam timing and lobe design and that translated to about a 10% hp bump for them. and then they get to run higher compression and that improves mileage. So there are benefits....bit it still seems to be down on hp compared to what can be done with port injection I thing due to better charge cooling with well designed port systems.
I don't know what the limitation is. If timing the injection right guarantees that no raw fuel goes out the exhaust port, then there shouldn't be an emissions limit to how high a state of tune a manufacturer can build, unlike with port injection. DI + throttle per cylinder should allow some pretty impressive states of tune without emissions compromises. Of course all the OEM's were in such a hurry to add turbos to tiny DI engines to meet fuel economy requirements that naturally aspirated DI engines remain relatively rare and we haven't seen much serious development of them.
I can tell from experience that the 2014 Corvette is a BEAST.
The racing application is a little different.
I haven't heard of injector swaps or aftermarket controllers which can run DI. I'd like to learn more about that.