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I've improved my MPG from 53 to 65+

6313 Views 21 Replies 9 Participants Last post by  cakley
For the last 37000 miles I've have only been able to get an average of 53MPG. So I have tried to improve the engines ability to breath and exhale or intake and exhaust flow.

I was going to replace the factory muffler after inspecting the inside to find out how restrictive it is with a free flowing muffler. Problem is there are no lightweight small mufflers on the markets. Stock muffler is 8lbs. So I decided to keep the stock muffler and just modify it. On the backside of the muffler and above the outlet pipe I drilled a large hole. One more hole was drilled into the outlet pipe. I shaped and welded a 1 7/8" 90 degree elbow from the muffler to the outlet pipe. This allows the exhaust flow to bypass the most restrictive part of the muffler. Sound was hardly increased. Can't tell anything from inside the car. Total cost was 1.99 plus my time welding. Only one test drive showed little improvement in MPG. However the RPM's raised quicker and a slight power increase was felt. An alternative to the elbow and easy to do is just remove the muffler and run a straight pipe.

Next mod was on the intake side. If you look at the air intake you'll notice that its right behind the radiator and after the engine warms up the intake pipe warms up a lot. There is a resonator located in the drivers side fender with a pipe running from it to the intake pipe. I placed tape over the inlet and just disconnected the pipe from the resonator. It’s held in place with a squeeze clamp and requires no tools to remove. I just let the hose hang. Perhaps the better set up would be to extend the length of hose to get cooler air. I wanted to keep it so I can return to factory setup in minutes. Basicly a cheap CAI cold air intake!

After I performed this mod I drove 8 miles across town and got 70.5mpg!!!. I took a longer way home to look at some houses total miles was 21 and final MPG was 65.5 The car felt like didn't loose power up hills. MPG was increased on flat roads. The car increased speed quicker and with less pedal. I'm real impressed and pissed at the same time. I wish I had done this 37,000 miles ago :!: :idea:

I'm going to DYNO test the car before I get my Volk rims installed then once more after the rims so that I can have solid proof that I have improved the car.
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Dumb questions

When I was looking at doing this mod, I realized that the entire intake could be disconnected at the airbox. Wouldn't this be more efficient at getting fresh air in than through the front heated air and the disconnected pipe that used to go down to the resonator?

Then it would basically have about 2 inches of pipe, go through the air filter (I have a K&N installed), then about 18" through the mass airflow sensor and into the intake manifold.

Granted that the cavitation from the rough pipe going down to the resonator could potentially do good things for the intake, though I think it is too far 'upwind' to do much good. Another use for the long intake is to keep water and other similar stuff out of the engine, but if the water gets that high in the car it is pretty much ready to be converted to beer cans.

Alternatively, would it be useful to run a hose that would be the same size as the intake to the airbox, and have it go down to the front of the car with some sheet metal formed ram air scoop? I'm guessing that this would be serious overkill of effort for minimal gain.

Also, with the muffler mod, would it be better just to open the muffler, cut out the baffling, button it up, and reinstall it? That way cops can't harrass you for having a straight pipe, but can still have a monster garage style "muffler". Even with straight pipes it couldn't be any louder than a 350 engine with a flowmaster setup, and I suspect it would be a lot quieter. Plus straight pipes or a "muffler" would have to sound better than one of those coffee can exhausts. Granted it may weigh an extra couple pounds, but I wouldn't think that would matter much.
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