posted on Jun, 1 2008 @ 08:18 PM
you know, I'm not suprised at all. I worked in the automotive repair biz for over 4 years, and rumors of detuning of production vehicles were common.
I personally knew a couple people who could tune a car to get about 10% better fuel efficiency... that was a stock vehicle. I also can tune a vehicle
for better mileage, as well as performance, but it's all by ear and I don't get the results that these guys have. Sometimes the fine tuning by ear
is called "Demon Tweaking". The engines talk to you through vibrations, basically.
One of the things they do in concept cars that helps in both performance and efficiency is total internal balance of the components. This can't be
done on an assembly line. As well, they don't want an engine to last too long, or a vehicle to last forever... that is exactly what put International
out of business. Nobody needed parts, because the things didn't break down like the other vehicles manufactured at the time. This is part of how car
manufacturers make their money... selling overpriced "Genuine (manufacturer) Parts", or OEM parts, and screwing you out of your warranty for using
non-OEM parts to give you incentive to pay for the more costly parts. If you want proof of this, just compare prices of aftermarket performance parts
compared to OEM parts. The prices are substantially different in alot of cases, until you get to the BIG NAME performance parts.
BTW, as a rule of good engine tuning, you do not sacrifice efficiency for performance, but rather increase efficiency to GAIN performance. One guy I
talked to (did dual exhaust on his 69 camaro), told me he moved away from California because they made him DETUNE his car because it was not within
the specified range for emissions. He even took it to a couple other places, and ended up filing with a court, which pretty much told him detune or he
would be unable to license his camaro for street use. This had nothing to do with the power, as he was only pushing 350HP. It was because they expect
you to fall within a range of emissions for a carbeurated vehicle. The laws are so strict (for some unknown reason) that you can't fall outside that
range, even (apparently) exceeding expectations. I also believe he told me that he was getting around 35-40 mpg on average out of a 327... better than
a honda! This was in 1998, btw.
TIP: Even if you get a brand new vehicle, immediatly replace the craptastic paper air filter with a K&N gauze & oil reusable filter. It takes out the
first major restriction point in your air intake. Secondly, upgrade your exhaust. There are alot of header and exhaust applications out there that are
50-state legal, and in some cases the system isn't any louder than the stock systems. Your major areas of restriction are 1) manifolds, 2) catalytic
converter(s), 3) muffler. Another thing that is easier to do (voids warranties) is to look through your system. You will see certain restrictive pinch
points, most where the header pipe connects to the manifold, where the pipe goes into the 'cat', as well as where it exits, as well as right before
the muffler. Large tailpipes just look kewl and deepen the tone, lowering the pitch to something a little more tolerable. (a high-pitched wavelength
converted to a low pitch wavelength contains the same amount of energy, but it is kind of spread out. It takes more energy to make a deep sound than
it does to make a high pitched sound). You still want a small amount of restriction somewhere in the system. It should be as far back as possible,
i.e. at the muffler placed as far back as possible.
Here's an example: my ex had a '98 Cavalier with the baby 2.2L engine. The manifold didn't have a whole lot of flashing inside, and was relatively
smooth all the way to the 2" exit, however the exhaust pipe at the flange was necked down to 1 3/4 in. The pipe connectiong from the manifold to the
'cat' was only 1 7/8", so I replaced the entire pipe with a 2". At the muffler, I used a 2 1/4" glasspack with the flared baffles (not the
round-hole perforation) facing to scoop the exhaust, then used a flat tip to further disrupt the sound. That, along with the K&N made the car AS FAST
as the 2.4L cavaliers with aftermarket headers and exhaust... raced alot of them, as did she. The exhaust was really mellow until you got into the
throttle full bore. Also, it increased gas mileage by about 3-4MPG. Why this worked is because I made a nice smooth flow all the way to the end, then
used the glasspack to create a non-restrictive back pressure so the computer wouldn't need to be tweaked. I also took out a small baffle on the
intake that was restricting airflow (it was a sound dampener... supposed to keep pulses coming from colliding with pulses coming out making a low
gurgle under the hood... never noticed any difference in sound, but gained a whole lotta performance!)
I could go on alot more about tuning intake and exhaust tuning, but that is really only a small part of the whole thing. I believe if you know how to
do proper exhaust and intake, and take a brand new engine, balance it internally, put in a proper camshaft, and recalibrate the computer, you could
easily get close to the mileage you were told.