So, I decided to do a little experiment in the Type RA. I normally switch between driving in S or S#. I rarely drive in I because of the reduced HP "feel" I drove entirely in I for an entire tank of gas. I did not alter anything, any way, amount of city vs highway driving. I was a little disappointed with the results. 14.4 MPG. My average is 17.2 MPG with the best being 20.4 MPG. My gut feeling tells me that limiting the engine to 6PSI boost would increase gas mileage not make it worse? Am I wrong in assuming that? Anyways, thought I would throw this out there to see if others had done anything similar and what their results were?
I've only ever treated my I mode as a "don't accidentally get in trouble" mode for long trips. I found that I'd subconscious roll into the throttle and be past the posted limits in S. That being said, I mode only remaps accelerator peddle (requested torque map, and not the throttle plate itself) and shuts off the boost controller so it's open waste gate. The throttle plate angle, incoming air (g/s), timing, and fuel injector duty cycle are not directly affected by si modes. The ecus goal is to hit the target afr no matter what the condition is. I've found its really hard to intentionally lean the afr out on subaru without opening pandoras box for the front o2 scale. I also highly doubt subaru would lean an engine out front factory that was historically known to crack ringlands. Regardless, I think you would only see a difference in mpg if you regularly drive in boost above waste gate. ymmv (literally). Edit: there are a lot of other factors to consider as well, like ecu tunes and vehicle speed.
I suppose that is right, I just thought with using less boost I may see an increase in MPG, kind of like the newer turbo cars of today. But with SI drive only affecting the throttle I should have kind of expected this result.
