Boosted cars correctly tuned and built can raise fuel economy actually. Its been proven.

It does NOT raise the displacement, nor does it STUFF more air in there. Are you serious, its physicaly impossible.

There are plently of newer cars tuned to run boost at 87 octane. All in your tune. And making 250+ HP on 2.0L's.

lol. proven? where? i want to see where a turbo will raise fuel economy...poor tune, professional tune, base tune makes no difference. more engine load= more boost= more fuel. simple as that. the only way the engine will not use a lot of fuel is during cruising speeds where there is very little engine load. this is going on a truck engine where he wants the boost to come in at low rpm. the engine is going to see boost most of the time so there is not going to be any fuel savings here.

yes. boosting an engine acts the same way as increasing the displacement.
example: a 2000cc engine running naturally aspirated can only suck in 80-90% of its displacement (also known as volumentric efficiency). when an engine is boosted, more air is being pushed into the cylinder (psi) instead of being sucked in the cylinder(in.hg or vacuum) causing the cylinder to fill with a larger air volume than the cylinder itself. volumetric efficiency can go well over 100% under boost. in this case the 2000cc engine under boost is acting like its a 2200cc or 2400cc or 2800cc engine. this all depends on how much boost. this is the whole point of boost but you say its not possible? its simple physics. air is compressable.

newer cars are different. they can get away with it because most newer cars are now direct injection with low boost. most newer factory boosted cars are grossly de-tuned for reliability. auto manufacturers spend millions of dollars in dyno tuning time to make there tunes safe and reliable. running 87 octane on conventional boosted engine is a good way to go boom!!!!!!! ive been in the business for decades and ive never seen a turbo'd engine running 87 octane while being tuned. it maybe possible but your not going to be able to run any reasonable amount of boost pressure especially on a n/a engine converted to boost as the compression ratio is too high.

^ I was like "what?" for a second, then I remembered what site I was on and I "lol'd".

17psi running 87 octane is not really low, on any engine. And your tune has everything to do with MPG and power, I suggest reading some actuall race and tunning shops for true info, not just internet forums. You may learn something.

But Ill digress and leave this forum, I see its not for my kind.

Ive seen people run 8psi up to 16psi on normally n/a engine with high compression, again if you understand how to tune your engine correctly you can do alot.

sleepy is right... turbos increase fuel economy. just not when in boost. thats why all long haul trucks are turbo'd... if you dont believe me than you have alot to learn about engine efficiency...

yes you can SAFELY run 87 octane in a completely stock: mazda 323GT 1.6T, doge colt 1.6T, mercury capri 1.6T, vw1.8t and 2.0T, plymouth caravell 2.2T, chevy sprint turbo 1.0T, 4g63 eclipse/talon/laser 2.0T, mitsu starion/conquest 2.4T.

im running a 9:1 n/a motor on 91 octane making an estimated 275-300whp on 14psi and i still get around 30 combined city/freeway with moderate/spirited driving.

it all comes down to efficiency. a turbocharger, done right, uses the wasted output of the engine (heat) to create a source of "free" power. ask any race engine builder...higher cylinder pressures are more efficient, and on the most basic level, thats what you get from a turbocharged engine. an n/a engine cant achieve the cylinder fill, scavenge, combustion pressure/temps, or fast burn times of a boosted engine. and at the very least, there is much less surface area in the cylinder of a small engine to absorb heat compared to a larger n/a engine of equal output
also, if 2 engines of the same size and hp are compared, one boosted, and one na, the turbo engine will always get much better efficiency, just because of the mild cam and lower rpm needed. a 400 horse 350 is easy to build either way, but the turbo engine will idle at 650 with 19"vac, cruise like a cadyy, and get 22+mpg on the highway...the cammed up thumper will idle at 950 with barely enough vac to run the booster, and get 10mpg, probably pulling the secondaries open down the interstate :)