Some of you have seen the "new little gadget" from my Miata. A very few have seen the data it spits out. I thought I'd do a quick review (and christen the "reviews" section of the website).

All of us in the Metroplex with '97+ vehicles are aware of OBD-II. Even if we've never encountered a MIL (Malfunction Indicator Lamp/Check Engine Light), we know they plug a computer in to our cars to find out if we "pass" the emissions test. Come inspection time, some of the folks with earlier cars may wish they had it as they watch some kid hook their car up to the dyno for emissions testing. Ever wondered what you can do with that "magic" port under your dash? Surely it's good for something beside deciphering the mysterious codes behind the MIL and ratting us out come inspection time.

Sample Data

So what can it tell you? Let's look at some sample data. Names have been removed to protect the innocent, but I suspect this data must not have been collected on public roads.

Next, let's look at some graphical data. The first graph shows the speed of a vehicle on a simulated highway trip.

The next graph shows coolant temperatures for the same "trip."

 The following graph shows intake temperatures for the same "trip."

Compare the intake temperature plot above from a turbo-diesel to an intake temperature plot from a Miata during an autocross run. Note how the temperature quickly decreases when the car starts the run (blue line).

You can also see the temperatures start to rise again when the car is parked after completing the run.

So, what about the MIL? Isn't that what the OBD-II port is for? When the CarChip logs an MIL event, it captures information about the current engine operating parameters and logs it to a file that you can view using the PC software. Here's a sample MIL trouble log created when running SeaFoam through my car.

Once I downloaded the data, I set the CarChip to "reset" the MIL the next time it was connected to a vehicle. It did so just fine.

On the more mundane side, the software presents information about every trip taken in the car in several forms. A Trip Log is shown below. The red highlights are determined by parameters that you set in the software.

Summary information is also generated for each trip. In the following screen, you can see time above/below thresholds that you define.

How long does it record?

By my estimation, based on a couple of 30% memory used reads from the device to my PC, it will store 40 hours of driving data before filling up. The manufacturer rates it at 300 hours, but that must be at a >5 second recording interval.

How do I get one?

Remember - the device only works on OBD-II compliant vehicles. There is a short list of otherwise compliant vehicles that don't work with the CarChip at the Davis website.

The best pricing I've seen is from ProVantage.com. They're currently selling for about $125. Several other vendors sell them for as high as $200 including shipping. Shop carefully.

My opinion

The CarChip is a great toy. I got mine from Ebay for a great price, but now I'd love to find one to keep in every car I own all the time. But, I'm a data junkie. I'd definitely buy it again, and I'd like more of them. Currently, I swap it between whichever of "my" cars I'm driving - the Miata or Jetta TDI Wagon.

If you have a car that seems to constantly trip MILs, adding a CarChip to your toolbox might be a big help in diagnosing problems. If you have kids (or speedy spouses?) this is a great way to keep tabs on them. In most cars, they'll have no idea the device is there. In the Miata, you have to remove the panel over the fuses to install the device. On my '02, the cover won't close with the device in place.