The projector is rated at 700 lumens(280W Metal Halide Lamp)
That Metal Halide bulb is probably pushing
well over 20000 Lumens total! LCD projectors are extremely inefficient, as you can see. (and on top of all that, it takes over a hundred watts of forced-air cooling fans to keep the thing from cooking itself)
I was afraid of that! I think I'll try and rig up a 250W mr-16 style bulb in there(I have a few obselete projector bulbs from my school to play with)
A 250W halogen bulb is going to probably produce only about a quarter of the lumens of the metal halide, and its color temperature will a lot more yellow (around 3000K), which will make the projection look a lot dimmer and uglier as the projector is calibrated around the cool white color temp of the MH (probably 4200K or 5000K) -- the blues just will not show up well with a halogen.
2nd: The light source needs to be as close to a point source as possible. The MH lamp will have a very small emitter area of only a few mm. 80 LEDs as you can imagine will have a very large emitter area! Clustered light sources can be used with projectors, but require a completely different optical design, would be easier to build a new projector from scratch if you wanted to go in this direction.
The way to make a more efficient small LED projector would be to go back to the older style of using separate Red Green and Blue projectors. There could be a separate high inensity red, green, and blue LED in each, with a black/white LCD filter. With a white light source, most of the light is getting filtered out whenever a pixel is switched to a particular color. Also, colored LCD screens inherently have lower transmssion than black/white as well because there are more traces/opaque regions on the LCD itself for the wires leading to the separate R/G/B pixels than a simple grayscale LCD. The problem with those kinds of projectors is that it can be very difficult to align the image properly so as not to cause "fringing" -- which coudl be especially severe on a high resolution projector. It would really only work for fixed applications where the power consumption of the HID bulb won't be as much of an issue anyway.
