I would like to know if anyone has tested this. it seems that efi usually comes in about .05% less power than a properly tuned carb, and my hypothesis is that the 43.5 psi that we all use is not enough to atomize the fuel sufficiently.

I wonder what fuel pressure of 70-100 would do, assuming the fuel pump and injectors are able to run at that high of a fuel pressure

I have never tested it, but I'm going to think the answer is probably no. My engine runs at 65 psi fuel pressure and I'm making lots less power than most of you probably are. I think that it would be an interesting test though. I have always wondered though, why do efi setups typically make a little less power?

I think EFI is capable of the same power output as Carburetion. Most EFI tuning is geared toward economy and lower emissions. To produce maximum power some compromises in economy and emissions are necessary. I don't doubt that some form of variable fuel pressure could improve the combustion process. EFI is still in its early stages. The computer controlled internal combustion engine has a ton of potential that has not been utilized.
Do lawn mowers and chain saws still have carburetors?
Squido

I think EFI is capable of the same power output as Carburetion. Most EFI tuning is geared toward economy and lower emissions. To produce maximum power some compromises in economy and emissions are necessary. I don't doubt that some form of variable fuel pressure could improve the combustion process. EFI is still in its early stages. The computer controlled internal combustion engine has a ton of potential that has not been utilized.
Do lawn mowers and chain saws still have carburetors?
Squido

Haha!! Imagine a loan mower with a PCM.

A lawn mower with a PCM is not that far fetched. There are already regulations to control emissions of power equipment, if not in place they are in the pipeline. There are already PCM-equipped motorcycles and no doubt on some larger stationary power equipment. I would way it is just a matter of time before it hits.

As to the original power question... EFI is every bit as capable and perhaps more capable to produce power as a carb. Even distribution of fuel in particular is much easier with EFI. Most OEM designs are optimized around typical driving requirements which emphasize torque over horsepower and slower speed engine operation. Of course emissions plays into this as well with OEM designs running biased towards clean operation over maximum power. But don't fool yourself that OEMs don't try to optimize power too: it is still a competitive market and drivers are still a power hungry lot. So the OEM design will try and give everything it can within it's limitations.

There is unlikely to be more HP resulting from an increase in fuel pressure. With atomization being a very critical parameter for emissions it is likely that OEMs would use higher pressure if there was a benefit there. Actually for power there is such a thing as too much atomization so it may even be the opposite relationship: reducing pressure might increase power.

But this is really getting into the small hairs of the situation. There is so much more air (by volume) involved in the process that it dominates the power equation. Intake runner design is where the most significant power gains or losses will be found. Second to that is optimization of ignition timing to make the most of what gets in there. Here a computer mapped and dyno optimized map can put more area under the curve than the old fashioned "distributor".