Freeing up the intake/exhaust will get you some HP and MPG, but be careful -
you need to match the inflow/outflow to the rpm range where you want power.
If you never go over 3000rpm, then you'll want smaller-diameter pipes with
as few restrictions (kinks and bends in the pipe or intake manifold) as
possible. For higher rpm power, you want larger-diameter pipes, again with
as few restrictions as possible. Although it is based on science, there are
enough variables involved to make it an art =)
Other things you can do are
1) lower the truck - this reduces airflow underneath the truck and greatly
improves aerodynamics and handling - IMHO, the best way to lower is with
smaller tires, lowered spindles and shackles as this will maintain most of
your payload and suspension travel - you can also had an air dam and body
side moldings to reduce airflow under the truck; however you are increasing
the frontal area of the truck, not good for aero, but better than nothing.
Also, block any unnecessary holes in the front of the truck, such as
foglight cutouts.
2) add a cap or, better, a tonneau cover - removing the tailgate or leaving
it down will NOT get you better MPG. At least on my Dak, under a
carefully-controlled experiment, tailgate UP got 0.4mpg better than tailgate
DOWN - if you don't believe me, you can get more info here:
http://cartalk.cars.com/Columns/CC/CC7237TXT.html
3) If your truck's computer doesn't advance timing with higher-octane
gasoline (via knock sensor), then run lower-octane as it lights off easier
and you will have more complete combustion (assuming your engine doesn't
suffer pre-ignition). If you run your engine and transmission both a
half-quart to one-quart low, you can increase MPG but may damage said
components if you run them hard - that is mostly a trick for winning MPG
contests.
4) Narrow tires with low rolling resistance (usu. low-profile) -
disadvantage is giving up some traction on dry pavement (read: poorer
handling and braking). You can also add skirts to your rear tires, but it
may look silly (ala Honda Insight).
5) Changing spark plugs won't get you better mileage, unless they are 1) due
for a change, or 2) you widen the gap on the plugs to take advantage of an
aftermarket ignition - even then, the mpg improvement may not be noticeable.
You can also try indexing the plugs - that is, take a marker and mark on the
plug tip (where the plug wire attaches) the side of the plug that has the
electrode. You then install the plug with various washers (specially-made)
until you can get the plug gap (opposite the electrode) aimed toward the
intake valve (or injector) when tightened. This starts the explosion at the
top of the cylinder and helps to push the piston down - again, it may be
insignificant, but some drag racers swear by it.
There're probably a few other things I can't think of right now. Basically,
you want to make the truck as small as possible (like lowering and switching
to smaller mirrors) and keep the powertrain in top running condition.
Also keep in mind that the expense incurred in making some of these
modifications can pay for a LOT of gas. ;-)
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:50:38 EDT