turbo 2 open exhaust
 

Does one see any improvement in highway gas mileage with an open exhaust? (assuming you can drive it sensibly)

You can see just fine, but your hearing will suffer lol

If you want to improve fuel economy get a wideband and an SAFC or something. Pull fuel intelligently and you'll not only see better mileage you should see power gains. I'm not exactly sure what you mean by open exhaust though. Do you mean ending the exhaust after the downpipe, no cats, or just straight pipes and no mufflers to the back?? In any case though you'll probably be happier having it tuned and still have a not-insanely-loud exhaust.

I do speak from experience with only running a downpipe. It is painfully loud. That is no exaggeration.

Keep in mind a more open exhaust will increase the boost level over stock, which will cause a dangerous lean condition iff measures aren't taken to increase fuel delivery at higher boost levels.

Your ears will also ring for several hours after you drive your car.

Well, what I mean is an exhaust from the turbo back. I would never run just a downpipe. That would be insane. I am putting together a car and I'm just trying to get everything budgeted!

can u also do this with an Rtek chip?

I highly, highly doubt you'll see an improvement in gas mileage while driving it 'sensibly'. It may make the engine more efficient at WOT, but that will more than likely take away from it's efficiency at cruising speeds. Why do you think most fuel efficient economy cars have tiny motors and tiny exhausts/intakes? When I pop the hood on my 82 hp tercel, I see drinking straw sized intake runners for a reason! If you want more reliable info on the subject check out a website where people are really working on improving their mpg, like www.ecomodder.com.

The only reason I asked was because guys with Supras were getting high 20 (like 27-29mpg) with fully upgraded engines, just wondering if the rotary was the same

Gas mileage has very little to do with exhaust and everything to do with tuning.

ah, guess i need a haltec then