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I've improved my MPG from 53 to 65+

6315 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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The Insight pre heats the intake air via the coolant lines that goes through the "throttle plate" body. This is done to decrease emissions and for economy. The black box you refer to is a "baffle box", (resonator) for the intake air to lessen the sound of the intake air being "sucked" into the engine. If you measured the area of the standard intake pipe opening versus the opening of the "hanging hose" you would see that the "hanging hose" is much larger. This allowes the engine to "pull" a higher volumn of air giving more power. You are also possibly getting warmer intake air as the area where you are receiving fresh air for the intake is one of the hotest spots in the engine bay. That's why I have my air cleaner for the turbo mounted where it is as that was the "coolest" area in the engine bay. You should be able to cruise at high speed with a lower percentage of throttle opening, and your acceleration should be "brisker". Better mileage could be contributed to the fact that you get to cruising speed quicker. (Fast acceleration vs slow acceleration)(That has been debated many times).........My opinion.
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