42mpg and STILL looking to improve it.

Here’s the setup thus far. And here is really what I have been achieving and the story behind it.

So as most of you know, I got introduced to the ZX2 a long time ago, it was my first seriously nice car that I loved. I kept it stock, found this site and started modding it soon after. I wanted nothing but performance no matter what it took. Only 2 years after that I was introduced to the world of sport bikes.

As soon as I got into sport bikes I ended up modifying my bike more, spending more on the bikes I have and stopped modding the ZX2, it turned into my daily once again after I had started modding it.

Now I look back and realize I still love my ZX2 but now that my driving habits have calmed down (after 4 tickets, somehow getting off on all but 1 of them which was a “unlawful use of studded tires in july”) i realized something. THESE CARS GET INSANE MILEAGE!

I had only modified the intake at first with a K&N filter. I picked up MAYBE 1 or 2 mpg… i was averaging about 36mpg, somewhere around that from my calculations. Soon after I did the resonator mod but instead of using the PVC pipe I used actual muffler tubing which was a bit lighter, sounded better and was easier to get installed, works great, improved more and now I have a bit more engine room in the whole hood department.

Then I stripped the trunk, however, added stereo equipment. Because I knew I would want less weight and that there is no point in removing weight only to add it I made the box setup small, light and not a permanent setup, with 2 wires and a bit of oomph the box comes out and the stereo will play the same without it except for the bass. So in this case if I don’t need it, don’t want it or don’t feel like it, the box along with the sub in it can be removed for extra weight along with the trunk being empty as well so less weight. Also done was a UDP to replace the stock pulley, weight reduction there as well as well as some more hp.

Currently with the intake, some weight reduction and the UDP and driving it nicely I have managed a MAXIMUM of 42mpg. This does not include removing the old mesh I had put on it as well as the a/c removal I am going to do soon.

So basically I’m looking into mods for this car still but ONLY if they fit the following criteria:

Rule 1: Must improve gas mileage
Rule 2: Should remove some weight if possible, only if it is not necessary to operate the car
Rule 3: Must not hinder the operability of the car, nor the convenience of driving the car
Rule 4: Must improve longevity of the car, whether it be maintenance, engine, or reliability related.

If it hinders any of those or improves power but hinders mileage, I won’t be doing it. So I’m basically turning it into a well performing car in some areas as long as it helps mileage, power, the longterm operation of the car and helps maintenance.

So some of the things I am looking into are:

  • More weight reduction (a/c removal, lighter stereo deck because the stock one is heavy, uneccessary brackets, metal pieces, etc… cross drilled rotors should provide SOME weight reduction, wheels, etc and possibly a fuel cell as they are generally lighter and some can hold just as much gas)
  • More power (would like to get a tuning ONLY if it does not cause the vehicle to be required to pump higher octane, perhaps header and exhaust only if it does not decrease low end torque and mid range torque as those are the main areas that are crucial for mileage)
  • More efficient aerodynamics! The ZX2 is somewhere between a .33 and a .35 on the scale I believe. I did hinder that with my mesh, which will be removed. And I will be looking into different things that may improve this and decrease any sort of drag… mirrors, facia, under the car (that is a project under the works and in progress…)

So… basically… unlike some who want max power, I just want max MILEAGE, reliability and longevity. So as the car progresses I’ll let you all know how it goes.

Now here are some interesting things to ponder…

What is the co-efficient of drag DIFFERENCE on the stock facia, and the 03 facia? Would the co-efficient of drag decrease much if at all if the mirrors were replaced with more aerodynamic mirrors? Lamborghini has aerodynamic cars from the body, to the facia, to the spoiler and UNDER the car, thats right, the underside of the car is nearly perfectly smooth… HOW can WE improve this on OUR cars in mimicking this?

I cannot answer your last question as they never made an 04… lol. It looks like you have your projects well planned out.

and idea for weight reduction in the trunk ( and Im not sure about this)… what about a fiberglass enclosure, wouldn’t that be a weight savings? it seemed to me that the box I made was lighter then the wood box I had.

sorry, was that oddball change 02 or 03, you can tell I know my years eh?

(edit) Thanks to RoushZX2 for correcting me on the year being 03!

I am fairly certain that replacing the stock 1.75" exhaust with 2.25" would be the next best way to improve milage. If you are looking to save weight I would check into the weight difference between aluminized steel and stainless. The stock exhaust is aluminized. That and weight savings from a CF hood.

Are your rims lightweight?

Intake/UDP/knocker mod/Full length header(OBX, KAMI, Hotshot)/ Weight Reduction(Including weight of RIM) and Tires are the only real thing are gonna boost mileage other then the drive itself. The diameter of the exhaust isn’t really going to affect things because 1.75" isn’t restrictive when your just crusing around. I would actually think this exhaust size is appropiate for getting good mileage because the small diameter helps keep the velocity of the gas fast. SCT isn’t really going to help mileage because SCT only modifies things in open loop(mashing the gas pedal). When your in closed loop your car reads off your front o2 sensor and maintains 14.64 AFR(optimal for best mileage). The only thing benefical I see from SCT is that it turns off the knock sensor, which the car stills reads from in closed loop mode if i recall, but one can turn off the knock sensor by simply unpluging it. This gives you rough 6* of spark timing which should also help mileage a bit. Other then that man just keep your throttle consisent, don’t mash the pedal, use control like no other(if you have it) and shift around 3k and thats pretty much it. Without spending more money that what its worth to save on gas.

OHOH!!! I had an Idea! Get a Tornado! LOL!!!

They are not. However, I did get a quote on some, so I may in the future.

WW Kit. It will improve your aero, plus I would think that the mesh would help, even if it is a li’l bit…(you’re talking about across the opening where the foglights would be if so equipped.)

  • Darron

Racer tape would also improve air flow.

if you really want to get seriously into the mpg thing, here’s a few thoughts over and above what has been suggested:

  1. destroke the motor using a 80’s 1.6 CVH escort crank and rods. This will decrease the displacement to 1.7 liters. I know it can be done, esslinger built a motor like this for a lotus 7 owner (he needed to keep displacement under 1.8 liters for his race class).

  2. use a 3rd gen sedan tranny and the .696 5th gear i sell. 70mph would be spinning the motor at 2630 rpm, given a set of 195-60-15 tires. Stock 185-60-15 tires would see 2680 rpm at 70mph.

  3. aerodynamic aids. lower the car, trim the lower lip off the rear bumper (it scoops air in stock form). smoothing out the underside with additional farings etc will help.

  4. space the tires out as close to the wheelwells as possible. wheel gap = aerodynamic drag. wheel spacers might not be a bad idea, and maybe some aluminum moon discs too.

  5. keep the oil weights light. 0w30 mobil one is a good alternative.

  6. hard compound tires. avoid performance rubber and go the all season route. the higher the treadwear numbers the better. Or, if you can find a set of takeoff tires from a Civic hybrid, Insight, or Prius…

  7. vacuum gauge. trying to keep the needle as far away from zero as possible will improve your driving habits and keep the motor as lightly loaded as possible.

I bet 50+ mpg could be attained with those mods and keeping the curb weight down. I’d LOVE to do something like that to a ZX2.


Like the Wings West Kit?

yes, and no.

the front and side skirts might benefit some, but the rear skirt would parachute the undercar airflow into the rear bumper worse than the stocker. Now if you cut the rear skirt and used only the side parts of it it would be beneficial.

and as far as the grille mesh… that’s a benefit not a hinderance.
the less air that can be trapped in front of the radiator, the better. A nascar style grille cover with a smaller mesh opening would be ideal.


Rob that is a well thought out and intelligent reponse, I applaud you for that. Thank you very much for those suggestions :slight_smile:

lol, wonder how that would look. Darn, I was liking the look of the side skirts and rear part. Any other ideas how to mold the rear to at least retain some of the look?

yes, and no.

the front and side skirts might benefit some, but the rear skirt would parachute the undercar airflow into the rear bumper worse than the stocker. Now if you cut the rear skirt and used only the side parts of it it would be beneficial.

You could put a diffuser from the Spare tire to the rear of the bodykit. That should allow better air flow under the car. Of course that would be a custom job.

Heh, Jayco? You there?