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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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hey cakley,

Decent suggestions you have there. I'm going to attempt the intake MOD as soon as the temperature here in PA increases a little. It is a bit colder then usual around here. Since I am no welder by any stretch of the imagination, I'm going to either have a straight pipe installed as you suggest or perhaps describe your muffler MOD and have some one with more skill in that area make the MOD. I just bought my'03 insight about a month ago. Life time MPG thus far is 58.6. I would like to see a means of increasing the threshold at which the IMA kicks in, I was also thinking of some sort of manual means of engaging the assist. Of course, all that requires some sort of technical/engineering prowess that I simply do not have when it comes to cars. Just a thought.

SOooo, your idea seems to work well in theory, in the sense that it can help to decrease the amount of "pedal pressure" required to accelerate and maintain cruising speed. What troubles do you (or anyone else here) foresee if I were to do the intake MOD now given the cold climate? Temperature this morning was near freezing. Ya know, that seemingly slight "oomph" you get when you first drive a car on a cold morning? Is that something like what you are seeing with the MODs you made? I would love to reproduce that little extra "oomph" on a regular basis if possible. I notice that my insight accelerates much easier/quicker with less pressure to the pedal on a cold morning then it does on a mild or hot day. So what are the pros and cons of allowing cold air to intake to the engine at all times, even during near freezing temps? Thanks for all your ideas and posts:)
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megaoptimus said:
Might be too cold up north for the air intake mod during the winter months.. It will be great in the summer time. So far in georgia I've noticed that it takes my car slightly longer to warm up in the morning. Thus my MPG is about the same as before just slightly higher. Vice the drive home in the afternoon I can tell and see the difference.
If you have a heated garage or take long trips then save the intake mod till summer time.

For the exhaust. My MOD was long way to go about. Any muffler shop can cut the muffler off and weld up a straight pipe for less than 40.00

If you want better MPG. Get lighter weight rims ie VOLK ce28n 14x5.5. Keep a close track on the tire air pressure.
Agreed. I hope we have one more warmer day up here before it gets too cold. I will try it then and see if I notice any difference. Other then that, I will have to wait until temps are warm again as I do not have a heated garage. Thanks for the info about the rims as well. I might look into that. I keep tire pressure at 46 all around. I figure that is a nice "hard" number while keeping a slight margin of saftey. I try to check it at least once a week. One of these I'll take it to 50 and see what 8) happens :shock:
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