You've seen it before-they did it in Japan and they did it in the US. But those were one-off cars. Who else but HASport would competently engineer the first readily available K-series engine swap for the new GD or Fit chassis?
Though it's been in Asia for some time as either the Jazz or the Fit, America just got the Fit for the 2007 model year as an attempt to compete with Scion and position beneath the ever-bloating Civic. While you might wish that the Fit weighs as little as it looks (so this would truly be a big engine in a small car), today's emissions and safety regs mean it's just not the case. The Fit weighs about 2450 pounds, right in the ballpark of the old EK chassis.
But it's new, has all that safety tech, looks like a trendy micro-car and, given the power levels tuners are achieving with the K-series engines, could really haul some ass with this swap.
This is our dirty little Fit. The stock L15 engine features VTEC, but with only one cam. That combo manages to belt out a massive 109bhp. We're here to do better.
Picking The Chassis
Not a whole lot to choose from here, the Fit is the Fit. There's a Sport model, but it's really a mild cosmetic and suspension change. You'll be starting with a fairly new car with lots of fancy sensors and electronics to sort through. You don't want to try this with a Fit that has the CVT (continuously variable transmission), since you'll need a proper shifter on the floor. Plus, it's cheaper-list price for a basic Fit is $13,850 at the time of writing.
Picking The Engine
The choices are endless since Honda has so many versions of the new K-series engine. For this particular swap, HASport used a K20Z3-the engine from the new 2006 Civic Si. It also used its six-speed tranny with its excellent ratios and factory limited-slip differential, something absolutely necessary for something with this much power and oddball weight distribution. But any 2.4-liter K-series from the Accord or TSX can be used-they'll all fit under the Fit's tall hood.
Keep in mind the good K-series engines are from the RSX-S, TSX and the 2006-up Si. Unfortunately, the other K-series don't have real iVTEC and make considerably less power. They are a good deal cheaper, though, and with new cams from companies like Brian Crower or Skunk2, it's possible to make credible power with these engines. You decide: budget or baller.
In this case, trying to remove and install engines without a lift would be like eating rice without your hands. You'll eventually get it done, but it won't be fun.
The transmission is a little more trouble, but one from the previous generation 2002 to 2005 EP3 Civic Si or 2002 to 2006 Acura RSX or RSX-S is cool. Right now, the TSX and all other K24 transmissions have a different housing so they aren't compatible with the bolt-in HASport kit. The 2006-up Si will also work, but, like the '05-up RSX, it uses a different speed sensor. The earlier one is easy to work with, the newer one is different and gives most gauges trouble.
Engine Removal
First, getting the shop manual from www.helminc.com is highly recommended and it's usually cheaper than from the dealer. Start by removing the bumper fascia, radiator, condenser and fans. Then, remove the lower subframe. Disconnect the lower suspension arms, then the front lower transmission mount, then the rear mount at the back of the subframe. There's no reason to remove the Electric Power Steering (EPS) from the car. Just unbolt the rack from the subframe so it stays on the chassis. Drop out the subframe and then remove the axles.
Next, discharge the A/C system, since at least one of the hard lines will need to come off. Do it the right way and evacuate it with the proper equipment. According to the Fit manual, you can use a hoist to support the engine from the top, but you can also support it from the bottom on a 10-inch or taller cart. Then instead of lowering the engine to the floor, the car can be raised off the engine. Test fitting is much easier this way and is how the swap is illustrated.
The K20 (right) looks taller, but it's not, that's just how it sits on the 2006 Si subframe. They're close in height, but the K20 and transmission are a good bit wider.
Wiring: The Fork In The Road
As with most modern engine swaps, electronics and wiring present the main problem. The Fit engine has uses a drive-by-wire (DBW) electronic throttle body and an SOHC VTEC system, not the DOHC iVTEC found on K-series engines. So modifying the stock ECU to run the new engine isn't even an option. Problem two, the Fit's dash, like most new Hondas, is controlled by CAN-bus communication via the ECU. But since each car has its own CAN protocol, a K-series ECU cannot just be plugged in and expected to run the Fit gauge cluster. The level of integration is so high that there's really no way of getting the Fit dash to work without the original ECU.
This is the fork in the road for the swap. Use a Hondata K-Pro ECU and run the engine, but have no gauges, or use the Fit's ECU and lose the iVTEC. The only way to have your cake and eat it is to do both. As a prototype for this swap only, Hondata and HASport have worked together to piggyback a K-Pro ECU onto the Fit's ECU. The K-Pro controls the engine in terms of fuel, ignition, closed loop operation and cams, while the Fit's ECU talks to the gauges, go pedal, e-throttle and the rest of the car. It requires a custom jumper harness, which the two companies are looking into selling, that lets the two computers coexist in relative harmony. Unfortunately, at this point there is no plan for Hondata to offer the wiring harness as a kit, since it's far from a plug-and-play affair, but customer demand might just change that.
To keep it simple, a K-Pro, an E plug to add some inputs and outputs that aren't in the stock engine harness plugs, and a rack of gauges is all that's required, just as we've seen in previous K24 swaps. You will need a speedo, engine temp, check engine indicator, tach and fuel level, at a minimum. For about $750, Racepak's 250-DS-UDXSR street dash has all the above, plus oil temp and pressure, high beam, odometer, brake and turn signals.
Remove the bracket from the left side mount. The HASport kit uses the stock mount, but will have a different bracket to attach to the mount.
Going this route means a lot of re-wiring. Hondata has K-Series swap wiring listed on www.hondata.com/images/k20awiring.gif. The Fit factory service manual is needed to build a subharness that integrates with the cabin harness. The harness needs a starter signal, then power for the main relay, fuel pump relay, O2 sensor relay and ECU. With a dash like the Racepak, a lot of the connections are available from the ECU. Just add the missing sensors. Lots to do, but possible.
Which way you go determines what you will use as an engine harness. The Hondata way uses the original engine harness. Add another cam sensor and wiring, wires for the VTC cam actuator and stretching it here and there is all that needs to be done. If you're going K-Pro only, use the K20's engine harness. Slight modifications and the cabin subharness are needed as mentioned above.
On the right or passenger side, remove the entire bracket and mount.
It's also rare to find a K20 engine with the starter and alternator harness. For some reason, these are on a separate harness that also connects to the battery. If you have it, great, modify it to, um, fit. If not, strip the four alternator wires, starter wire and charging wire from the stock harness and integrate them to the engine harness you have. Don't forget the K-series uses a wideband primary O2 sensor. If you didn't get it with your swap, you'll need to buy one.
If all this sounds too complicated, HASport is working on the solution. It will offer a complete harness made from the K20 and L15 engine harnesses along with all that's needed to connect to the Fit's cabin harness, including the O2 sensor connection (but not the sensor).
Here's problem one, just behind the right side mount. The brake lines are in the way. They'll need repositioning. Disconnect those A/C lines at the same time. If you want A/C, you'll need a couple custom lines. | 
The next problem is right next to the first. The ABS modulator wants to ride the idler pulley. | 
Repositioned brake lines. |