So the time has come for me to write about a regular Mase Engineering stable mate. It’s a 2007 Lotus Exige S owned by Dr. Christopher Prusinski. While ultimately its normal duties were to serve as a steady, reliable, and fun track car, it also is still registered for street use. We left the Lotus fairly unmolested at the beginning of its life. Before the engine conversion, it normally rocked the carbon fiber aero additions, stock 2zz Toyota engine and transmission, AP Racing front brakes, and Lotus Track Pack. We developed a liquid to air intercooler several years ago that did a very nice job keeping the intake temps cool compared to the inefficient stock air to air intercooler. Other than that, the only other performance additions besides the ECU tune was the exhaust we fabbed up. Last year during NSXPO, when we sheared off a gear in Dr. Prusinski’s 500+ whp Turbo NSX (another beast of a track car), we turned to the lotus as the backup track car. Unluck unfolded, after 12,000 miles, the factory Toyota engine decided to puke after a few laps. The OEM piston failed and ripped completely clean off the wrist pin, destroying just about everything within the engine.
We all had a big decision. The lotus had been very reliable up to that point, (minus a broken axle at Watkins Glen) but with the desire to always want more power. Rebuilding the 2zz would yield a stronger engine, but not really much more power. So by the time money was spent on building a forged internal engine as well as upgrading the factory supercharger, it would be dumping a lot of money into the setup.
Along came the idea of swapping a K-series engine into the mix. I’ve worked with many high horsepower Honda K-series engines, and configured a naturally aspirated build that would be reliable, powerful, lighter, more fuel efficient, and run cooler, this is a huge plus given the high heat and humidity down here in Florida. Dr. Prusinski gave the green light. Doing research I found innovative motorsports, who when talking to them, said they have everything we would need for the swap. Little did I know it would actually take 11 months later after I ‘placed’ the order would I receive the final parts.
Owning a motorsport company I’ve been accustomed to hardships of all sorts. I hate to ever speak bad about another company, so I will leave out many of the frustrating problems I had and focus on the end result. Luckily for me, I was able to source a lot of the items we needed to fulfill the empty promises from Innovative didn’t come through with on time. At the end, we used the innovative mounts, throttle pedal and throttle cable. Everything else didn’t show up/fit/or not up to par.
The engine setup I designed was to be very straight forward. The motor consists of a Honda K24 bottom end. I chose the 2.4L out of a 2008 Acura TSX due to the revisions they made to the block for the 2006-2008. The cylinder head, we went with a k20 cylinder head off an Acura RSX Type S. We modified a new Type S Oil pump to flow better, and added a bafflle inside the oil pan. High compression forged pistons, light weight rods, balanced, and assembled by me. Full valvetrain, SS valves, and a set of aftermarket Cams. I used the same intake manifold we use in our Grand-Am race cars at RSR Motorsports. I chose a Hybrid-Racing throttle body due to the solid construction, and the fact it bolts up to the intake manifold without an adapter. I designed the header to be a 4-1 collector with a good merge angle and runner diameters. Thanks to Dwight at Stage 6 motorsports for the fab work on the header and exhaust, as well as the brackets for the oil cooler in the side vent.
I chose a 2007 Civic Si Transmission due to the fact it was newer, and comes with a limited slip differential. It had very low miles so I didnt want to break it open. 6th gear is quite long in it, but being that it is still able to be driven on the street, another reason to keep the stock gearing. Using this transmission meant I had to modify some circuitry so that the Hondata PRB Ecu could read the correct VSS Signal. In the future, I’d love to get a sequential gearbox in the car.
Way back at the end of 2011 I started on the engine harness. I wanted to make the swap as clean as possible, I sourced some of the Lotus ECU Connectors, and tied a brand new oem honda engine harness that literally plugs into the factory harness. Hondata makes a CAN adapter that will drive the factory Lotus gauge cluster, it works pretty well, except we noticed it cutting out every once in awhile on track.
If I had to do it all over again, I would certainly recommend someone to buy a complete swap. Luckily Jacksonville’s fastest Honda drag car owner, Cesar Olin, has a stock pile of miscellaneous parts, and was a big help to me when building the engine.
The result: 295 whp and 212 ft/lbs of torque on my very low reading dyno dynamics dynamometer. In the near future I will roll the lotus on the scales and see how much weight we’ve been able to shave off due to the lack of heavy supercharger/intercooler, the removal of other oem components such as the two factory oil coolers and lines that run all the way to the front and back. The car is a totally different beast. The car is making another 80 horsepower over what it had with the supercharged 2zz engine. The power and torque makes this car very quick around the track.
Here is an in car video of the first time the car was tracked with the new setup at Daytona Speedway:
Honda Powered Lotus Exige S at Daytona Speedway - YouTube
More info will be later posted on our facebook: http://www.facebook.com/MaseEngineering