Calculating your actual gas mileage

One of the more common questions people ask when doing an engine swap or upgrading your turbo is “What kind of gas mileage do you get?”

Well, this answer is going to depending on a few things:

  1. How is the engine tuned? If you’re running pig rich then you’re going to get terrible gas mileage.
  2. How do you drive? If you’re constantly mashing the gas pedal and generating a lot of boost then you’re going to get terrible gas mileage.
  3. Are the fundamentals of your car set up properly (i.e. are your tires inflated to the correct psi?).

All of these things will contribute to your gas mileage. My recommendation is to do a controlled test that incorporates your typical driving habits so you can get a real, true answer as to how much gas mileage you’re getting.

This test is so ridiculously easy!

  1. On your next fill-up at the pump, reset your trip counter to zero. This test assumes that your trip counter is in working condition.
  2. Put a full tank of gas in the car.
  3. Drive your car as you normally would until you’re ready to fill up again.
  4. At your next fill-up, write down (or take a picture) of your trip counter and the number of gallons of gas you put into the car.
  5. Divide the trip counter by the gallons (use decimal points for accuracy).

The result is your actual miles per gallon.

Trip Counter
Gas Pump

Using my example above, I would take 230.1 / 13.699 = 16.796 miles per gallon.

My driving habits included a lot of rapid accelerating, some downtown driving, some highway driving. My AFR is typically 15 at cruising speeds to help. This low mpg is likely due to my own driving habits. When the weather is nice I drive the 240sx for fun, not for gas mileage.

Do this test yourself and see what kind of mileage you’re actually getting. You might be surprised.

*** EDIT ***

I did a more thorough test without hammering down and here are the results for casual driving: 17.9 mpg City and 22.1 mpg Highway. It’s not bad as long as you aren’t getting into the boost a lot.



New Additions to the Car

After many months off, the 240sx has been updated again. I installed new KW V3 coilovers, new Hawk HP+ brake pads, Tein Camber plates, and a GReddy front tower bar. It was all relatively easy to do and let me break in my new garage a bit. I had the car professionally aligned at the Winning Formula in Louisville, KY. The car has never handled so amazing. I can actually power through corners without oversteer. The car is almost ready for the track season. Next up on my list of upgrades are SPL front and rear LCA (when they are available), and a set of Nitto NT01 tires. Should be a fun year!

How to Tighten Nut on Camber Plates

When I was installing the KW V3 coilovers on the S14 240sx, I ran into a couple of minor roadblocks. The purpose of this post is to help other DIY folks out there avoid this problem.

  1. The KW V3 coilovers do not come with camber plates. They assume you will either provide your own or use the factory mounts. My factory mounts were long gone since I already had coilovers.
  2. Not all camber plates for an S14 are going to be the same. The inner diameter of the coilover shaft is different from a KW V3 when compared to a K-Sport, for example.
  3. Removing and installing camber plate nuts is not an easy task if you don’t know how it’s properly done.

So I removed the K-Sport coilovers (that was pretty easy because I had this handy write-up showing me step-by-step instructions), but then I realized I had no mounts or camber plates for the KW V3. Tangent – This was a nice time to do a brake pad swap, so I installed a new set of Hawk HP+ pads while the wheels were off. Ok, so the logical thing to do was try the K-Sport camber plates. Unfortunately, the front did not match up but the rear mounts did. Not all are created equal, remember? I came across a set of used front mounts that did the trick, but they had no camber adjustment. So I bought a set of DC camber plates that were supposed to be for factory struts, but those did not fit either. Grrrr….

Tein to the rescue. The Tein camber plates and mounting plates for the rear ARE designed to work with factory equipment. They look great, are easy to install, and are relatively affordable. If you are spending the money on a set of KW V3, you might as well get a proper camber adjustment.

That leads me to the tricky part – removing and installing the camber plate nuts that hold them to the coilovers.

DO NOT USE AN IMPACT WRENCH. You stand a good chance of spinning the piston in the damper, and this will potentially ruin the internals of your suspension. If you want a quick way to test, you can try to compress and expand your damper with the adjustments (compression and rebound) full open or closed. If you feel the difference (i.e. it’s harder to expand or compress when you make that adjustment), then the coilover is probably still ok. This is not a scientific approach, but it’s better to make sure you didn’t ruin them before you put them back on the car if you did use an impact wrench.

The proper way to do this is using a hex key and a box wrench for some setups. Other setups require like an 8mm socket and a box wrench. The Tein were a little different, but the same general concept worked.

This picture below illustrates how the hex key is used to stabilize the shaft while you use the box wrench to tighten the nut. If you don’t stabilize the shaft then it will spin freely (not good). Some people have used a strap wrench to hold the shaft. This did not work well for me because it slipped. I tried a strap wrench with a vice grip over the strap for protection and that had some success. The trick is to not damage, scar, or scratch the piston shaft of the coilover. If you have to grab it for whatever reason, do it at the top. Never grab it with anything towards the bottom or you will ruin your coilover.

Notice how the hex key we use in this scenario is different than the smaller hex key K-Sport provides to change the compression. The hole is larger in diameter for the larger key to hold the shaft, but it doesn’t extend deep enough into the internals. You don’t want to use that or you’ll damage your compression adjustment capabilities.

Now the KW V3 coilovers are different. You don’t have the hex key ability. You have to use a box wrench and an 8mm socket on the outside of the top. The tricky part is that some of the mounting brackets and/or camber plates are recessed, meaning that you can’t easily get a box wrench down in there to adjust the nut once you have it installed. I didn’t have a tool that would allow me to do this so I used a trick. I took a deep socket and I pushed an extension for the small 8mm socket through it. I grabbed the deep socket for the larger nut with some vice grips really tight. I then was able to tighten it down pretty easily.

Check your instructions for torque settings on this nut. It varies from manufacturer, but the KW were around 26lbs of torque (i.e. not very much). You don’t want them rattling loose, but you don’t tighten these like you do the rest of your suspension.

I hope this helps. The whole process is fairly easy. It took me a little bit longer my first time, but swapping the suspension on an S14 240sx is at most a 2hr job for me now (without a lift).

p.s. Once you do a suspension adjustment like this, you’ll want to make sure that you get a proper alignment. Anytime you change the ride height it’s a good idea to do that.