Hello everyone, I'm new to the forum, but not new to custom work.
I have been working on my 2003 5at sedan to achieve better mpg first, and hp second.
I'm making this post for some of you that have asked several times about improved gas mileage and have been told that some mods will yield no gains, well there are gains to be had, and if you can keep form playing with the gas pedal too often these mods do indeed make a big difference.

I have started with a used Megan 3" mid pipe, used Topspeed y-pipe, used Motordyn 1/2" spacer, my own SS 3" Z tube, a K&N drop in filter, and I am running Royal purple full synthetic engine oil.

I modified the y-pipe with a Magnaflow 2 into 1 muffler to mate up to the mid pipe, and used the same muffler for the back of the car with the stock tips put into place for appearance's. I did this muffler modification to anticipate future exhaust mods, ( headers and HFC's ) I also have a second 3" resonator on standby for when the headers and HFC's go on.

The sound is fantastic right now

As of these mods so far, I have seen an increase of MPG from an average of 17-18 before to 23-24 after.
my driving has been an estimated 75% city 25% hwy. I have not had a chance for a long freeway stint yet.
I do moderate my driving habits to achieve better MPG, as most are doing now I try and not play with the pedal too often, but on occasion I do
As for power I have lost some low end torque at this point, but have gained Hp up top ( 3,000rpm's -up )

I was able to get on our next door neighbors Dyno-jet for a quick run today and saw 221.7 RWHP with AFR at 12.7. I was unable to get torque due to being at the end of the day and having this done for free, I wasn't going to push it.
I would have preferred to have numbers before the mods, but the dyno was not fully operational at the time, ( they just bought it )
So far I am on my goals of getting better MPG while having the extra power when I want it.

My next mod will be headers and HFC's, and that should do it for me other then a tune if I'm seeing leaner conditions that would warrant it.

Hopefully this gives some insight to modifications that can help with improved MPG.
I will post again when the headers and HFC's go on in a couple of weeks.

 

The dyno reads torque then mathematically converts the torque numbers to horsepower.

If you can improve MPG by just a real 1.0 MPG [under EPA test regime] and still comply with emissions and meet durability and noise standards - Nissan has a 100k + job for you...............In fact every car company in World will be bidding for your services.

 

Changing driving habits go a long way in improving MPG's. If I'm nice to the car I will get around 22-23 combined. If I use the right foot too much then yes, it will drop to 16 or 17 combined. Highways and ~65MPH are your friend...if you can stand being passed by everyone (which I can't).

Yes, more efficiency is nice but really, you are dealing with a ~300 hp RWD car. If you want to be economical go get a Yaris.

 

The main reason I am posting is to show that the most common mods people do, can give you better MPG.

I have read on here several post by others that say that you will not see any MPG gains, not true, that's all.

A factory built car is not the most efficient in overall design, but more set towards a streamline production that has compromises in several area's that meets the production cost and still gives a moderate output in power and milage set within the production cost outlook.

The aftermarket improves on the area's where the factory left off.
Most of these, if not all, were done for improved power first from an aftermarkets standpoint, by allowing the motor to be more efficient.
None of these mods actually "add" power, but just allow the motor to operate closer to it's full potential ( more efficiently )

I am not trying to achieve Yaris equivalent MPG, just better then what most see, and since this is my families daily driver ( car pool ) I still want to have an enjoyable driving experience with this car when I feel like pushing it, and have better then normal MPG at the end of the day.

If people on the forum would rather not see this type of testing, I'll stop here, I was only trying to help those that I thought would find this helpful in making a decision on aftermarket modifications.

 

3" exhaust? you planning on FI at some point?

 

Possibly down the road. Just depends on the time-line and money. The wife and I are doing some house remodeling right now, so the mod money is not there

 

How can I find more information on the EPA test regime?

I really need to research deeply into this subject.

 

No, it's good you do this but in reality your MPG's will differ each day. By adding a part here and there and comparing on different days you have not only introduced your 1 new variable (new part) but numerous new variables while driving. Temperature, barometric pressure, traffic flow, and many other things will directly affect your MPG's. I have no doubt that by adding CERTAIN aftermarket parts that the engine will be more efficient, thus increasing MPG's. Some aftermarket parts weren't developed with the research that others do, I think most of us know who puts serious R&D into their products and those that don't.

Another thing people do, and I do to, is once we get our fancy new mod we want to make sure we are getting what we paid for. We put it on (or pay someone to) and we start to give our right foot a good workout.

Keep posting by all means. It's just we get questions daily about "How many more MPG's will I get with a Z-tube?". Drives me nuts

 

I totally agree with your input on variables. One can only control so much.
I, have also enjoyed the car more just after what I have done and seen less then desirable MPG, but that should be expected for those that enjoy these car's on a more frequent spirited drives

I'm just looking to offer what is possible with what I have added and will add in the near future that covers the majority of the basic mods.
I will only post an "average", as I can not expect everyone to expect what I might see for increased MPG, as others may see more than I do, depending on your said variables.

I just hope more will realize that certain mods will increase their MPG if they can keep it under control, verses staying totally stock, thinking that this is the best way to achieve better MPG.

I also have no desire to break down every part verses MPG, or power increase. I think that has been covered at least power wise already.

 

The owner of the dyno stated that he did not hook something up to get the torque value, I have no expert knowledge in dyno's, so I have no answer other then that
As for the EPA test regime, The noise level is the most complicated to achieve ( intake & and exhaust ) and still get better performance + MPG. Emissions and durability is the easy part

 

IMO, I beleive that installing the Stillen CAI or Drop-IN K&N filter and MD 5/16 ISO Thermal spacer did help a little with fuel economy, if you can keep you foot out of the gas pedal..LOL. Love that sound

The spacer allows more air to rear the front two cylinders. Also noticed that my car idles a little quieter because the engine is getting more air.