If you’re looking for:
Part 1: The Rebuild, go here.
Part 2: The Wrap, go here.
Part 3: More Goodies, go here.
Part 4: Aero, go here.
Part 5: Cooling, go here.
Part 6: Fuel & Oil Control, go here.
Part 7: Clutch, Trans, Misc., go here.
Part 8: Roll Cage, go here.
Part 9: Brakes, go here.
Part 10: K24 Swap 1, go here.
Part 10: K24 Swap 2, go here.
Part 10: K24 Swap 3, go here.
Part 11: K24 Head Work, go here.
Part 12: K24 Swap Rewire, go here.
GTA Super Lap Battle
A few months ago, we decided to register for this year’s 2021 Global Time Attack and Super Lap Battle Finals at Buttonwillow. The Exige wasn’t built for time attack, but we thought it would be a fun place to compete and see how capable the Lotus with a K-series really is; even if it is heavily outgunned in its class (because of the rule set, the car falls into Limited, a class that normally sees cars with forced induction engine setups making well over 600whp). We decided to set our own goal of a sub 1:50 lap, which may be the first naturally aspirated Elige to do so. The best time this car had done previously at Buttonwillow 13CW was a 1:51.7 on Falken RT660s.
More Power
We figured that this would be a good time to experiment with the K24 and see what the engine can do with some relatively basic mods.
4 Piston Racing TSX CNC ported head, their RR3 road race cams w/ Supertech Performance valve springs/retainers and Ferrea valves.
RBC (06+ Civic Si) intake manifold with an Acura ZDX throttle body. The RBC manifold is one of the better flowing ones compared to all of the other OEM options and the ZDX throttle body is the largest OEM drive-by-wire throttle body available. An adapter is needed to mate these two together and some port matching to smooth out the air flow.
We also installed OEM Acura RDX injectors that are 410cc to support the additional power. An OEM headgasket with ARP head studs is what we used to put the head back on the block.
With all of the track miles this motor has seen, the inside was clean! You can see remnants of carbon build up from the engines past life (this was a junkyard motor). We threw the cam caps and rockers in ultrasonic cleaner to get them nice and shiny.
Putting the head back on was straight forward. There weren’t any surprises that you might find with other engine swaps and replacing the head on the K24 was the same amount of work that a 2ZZ would have been. The RBC manifold has much longer runners than the stock RBB manifold, so it sits close to the firewall, but there’s still enough clearance for the engine to move around.
Once it was all back together, we took the car to Jei at Blacktrax to re-tune the car. With the better flowing head, the gains really started to show above 6k RPM where it made nearly 50HP over the stock configuration last year. I was really happy with the results and excited to try it out on track.
Stock K24 vs K24 with head work
Stock supercharged 2ZZ vs K24 with head work
Global Time Attack
GTA finals is held at Buttonwillow Raceway every year and this would be my first time participating. Victoria, our 1.5yo daughter, Harley, and I arrived to the track on a Thursday evening where a 5th wheel RV was waiting for us. It made sense to rent one and camp at the track since we would be there for the entire weekend.
Shortly after unpacking and setting up, Tom and Marc arrived. There wasn’t much to do to the car, so we had a pretty relaxing night.
A few weeks prior to this event, we were at Thunderhill when a storm passed through and our canopy didn’t survive. Luckily, Martin at Supertech Performance lent us his nice 10x20 canopy. Thanks, Martin!
Practice
Friday was a practice day. The track was open for the competitors to test, tune, and practice for the competition. For our Exige, this would be the first time driving it on the Yokohama A052 street tires, so we really needed the day to get familiar with them and with the additional power of the new built head.
As suspected, the most noticeable difference with the car was how much top end it now had. Instead of running out of breath round 6k RPM, the engine now pulls all the way to redline. This meant making minor changes to the shift points that we were used to.
The A052s worked very well, but like on other cars, there is a very small window on when they have the most grip. We found that after warming up on the out lap, we could only get 1-2 hot laps before having to cool them down again.
After a few sessions, we decided to make some adjustments to the shocks, and change the wing angle. The day went smoothly and with consideration that we had two more days ahead of us, I was able to turn a 1:53.1 lap and Tom a 1:51.2, already besting the car’s precious PB at this track. Promising!
When we were done driving for the day, we took the car through GTA’s safety tech inspection.
After passing tech and going through registration, we were given some event sponsor decals. We spent some time putting them on the car and did a mini photoshoot with Tom’s iPhone.
Competition Day One
On Saturday morning, we woke up to a very foggy track and were delayed until 11am.
Competitors are grouped and gridded by their times from the practice day and the grid positions update after each session. This minimizes the amount of passing that has to go on during each session. Because of the delay in the morning, some of our sessions were only about 10 minutes. This meant that we did our warm up lap, and hoped to get two hot laps in without anyone going off in front of us, caution flags, or cars dumping fluid on the track. By the end of the day, I was able to manage a personal best time of 1:52.0. Tom was a few tenths faster with a 1:51.8.
Jon’s 1:52.0
Photo Credit: Khai Doan
Photo Credit: Khai Doan
Competition Day 2
On Sunday, we had heavy fog again and even some misting throughout the morning. We didn’t get to start our session until after 12pm. Despite the warmer ambient temps and only running one session, Tom was able to do a 1:51.4 lap putting us in P7 out of 19 cars in limited class and 17th overall out of 57 cars.
Tom’s 1:51.4
Sub 1:50 Lap
Between Tom and I, we didn’t get a chance to get into the 1:49s like we hoped, but we still had a blast and considered it a successful weekend. However, our friend Graham surprised us on Saturday by coming down to support and to hang out. We threw him into the car at the end of the day on Saturday for an unofficial run and he did a 1:49.5 lap! We had been struggling with shifting into 5th gear all weekend and later found two issues. One, the shifter bearings in our shifter started to seize up from moisture, causing it to bind, and two, one of the motor mounts was starting to come loose. We believe that the car is capable of a 1:48 with some more set up development on the A052s, some more shock tuning of the JRZ dampers, and no misshifts. I’m really amazed by how incredibly capable this car is with only 250whp, and can’t wait to continue developing it in the year ahead.