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24th of April. Winter has no plans to release its cold claws...

The LS6 shouldn't be covered by cheap plastics, so I removed the valve covers. This only revealed a new layer of connectors and sheet metal brackets, so this is clearly not an engine designed to be put on display. I replaced the sheet metal brackets with ICT billet ignition coil brackets, which helped somewhat. In hindsight, valve covers with integrated coil posts would have looked more tidy.

Winter is coming The C5Z is in hibernation until spring time. I don't have a heated garage, so working on the car in freezing temperatures is not an option. At least I can start to make a plan for the next season. The car in front is an MB R350 with a stretched cam chain, lots of work to get that fixed on an OM642 engine. Drivetrain maintenance I returned from the last trackday with a load humming from the rear end of the C5Z, which is probably a differential failure. I'm hoping for a simple fix like broken belleville springs, draining the oil will give a telltale. There are already other issues that requires attention, so I guess the time has come to have it all sorted: Broken rear differential Engine rear oil seal leaks (which requires removing the torque tube anyhow) Worn slave cylinder ("clutch pedal stuck to the floor") Clutch and flywheel replacement Torque tube couplings and bearings

The Innovate wideband O2 install wasn't a success. I installed the probe  after  the catalytic converter, which throws off the O2 readings. It measures AFR ~14.7 most of the time. That is not true, as I can see the ECM switching out of closed loop on high load. I was hoping that I could recalibrate the MAF to zero out the fuel trim values, but I'll remove the wideband for now and get back to it when/if I remove the manifold or install long tubes. The voltage cut-off  for the electric power steering also seemed like a good idea in my head, but it is annoying to wait 10 seconds for power steering assistance after starting the engine. First there is a delay for the battery voltage to raise above the threshold, then for the power steering pump to wind up. I'll replace the voltage cut-off with a switch!

Don't drive with your nannies on! With active handling in competitive driving mode, yaw control is still active and using the rear brakes to correct excessive yaw on corner entry/exit. This causes the rear brakes to run hot, and in my case one of the rotors cracked as the car cooled down in the pit. I even heard the *PING* as it happened. 305 to 330 mm brake rotor After some research online, I found that the C6 with the Z51 option code uses a larger 330 mm brake rotor, but still share the same caliper and parking brake dimensions.  Plus Increased thermal capacity. The EBC Z51 rotors are ventilated on both sides, have a higher mass and increase the swept diameter of the brake pad Better looks, the brakes fill the 18" wheel and looks more in balance with the front big brake kit. Reuse of stock brake calipers and parking brakes Minus Change of brake brake bias. The increased rotor diameter causes a braking torque increase of ~ 10%, which could affect the front to rear brake bias.

Finally time for a new trackday, Vålerbanen again. Now with a larger 30 row oil cooler and a Trackspec hood vent installed, but to my frustration the oil temperature still exceeded 130 deg C after a few laps. So there will be a "Never ending oil temperature story - part 4" Except for the oil temperature, the car ran great. Engine, clutch, gearbox, brakes, tires - not a single hick-up. [Edit: Incorrect. A rear brake rotor cracked and the differential failed] I did set a new personal best time, and judged by the video, reducing the lap time further should be possible. Less braking, more precise lines, higher cornering speed. The Hoosier tires provide amazing grip, which I still have to learn to use. Corners can be taken at a much higher speed than my brain thinks, which is evident as I didn't have a single mid corner incident (like carrying too much speed) the whole day. My focus was on driving, so I didn't notice the broken audio cable or that I mismatched the on/off

High up in the mountains in Norway, close to freezing temperatures, the driver side window regulator broke down. Perfect timing. Fortunately, I managed to pull the window up by assisting the motor. A broken piece of plastic was all it took I had to twist my brain to get the parts back in the correct orientation. Notice that as pictured, it will not work. The wire coming from left (door B pillar) needs to pass below the right wire, otherwise it will conflict with the window. Mounted incorrectly here: I also noticed that the regulator power cable and the door latch switch cables interfered with the mechanism as it moved up and down. so I used some high strength duct tape to move them out of the way. New window regulator in place. I ran the window all the way down so that there wasn't any tension on the mechanism before tightening the bottom nuts. I followed Chris Askew's guide to replace the regulator:  https://www.chrisaskew.net/blog/2020/12/8/how-to-replace-window-regulator-200

Heat management is still an issue on track days, so I decided to add a Trackspec hood vent. Trackspec T1 description Optimized louver design to maximize extraction flow velocities within a vehicle in motion Reduces under hood pressure delta to reduce front end lift and increase net vehicle downforce. Significantly reduces under hood temperatures by extracting heat and allowing fresh cold air to enter the engine bay. Maximize life of engine accessories by reducing overall operating temperature. Increases dense, cold air flow through radiator to promote lower coolant temperatures. -exactly what my C5Z needs! I managed to source a used T1 hood vent in good condition. For the install, I decided to use countersunk hex screws rather than pop rivets, as I don't like the look of pop rivets (it is not a kit car, after all). To countersunk a screw, you need enough material thickness for the screw head. I looked up some tables and concluded that M3 (3 mm) screws would work. An Ø6.3 mm 90 deg

My first drive on a drag strip. Not really a drag strip, but a 2000 m long runway in the mountains in Dagali, Norway. We had the opportunity to use 1000 m, with ~500 m for braking. I failed completely on the first attempts. Too much adrenaline and wish to go fast, so the tires didn't hook before 3rd gear. I learned had to drop the launch RPM down to almost idle and feather the throttle to maintain traction. I guess it didn't help with 6 year old Kinforest 280 UTQC rear tires and an air temperature of only 5-6 degC. The HP Tuners log reported a speed of 239 km/h at ~ 1000 m. Not too bad with too bad launches. NOTE: I'm driving the black C5Z, which takes......forever......to appear on the right. The attempt to heat the tires was not a success.

A small rear spoiler corrects the "missing link” on the rear end of the C5 FRC/Z06. After adding the spoiler there was a noticeable increase in wind noise, so it might also add some downforce.

Engine oil temperature, the never ending story part #3 The 16 row oil cooler did help to lower the oil temperature, but not enough. I was advised that the absolute minimum was 25 rows, so I sourced a new 30 row oil cooler. I have to admit that I'm using a "Made in China" product, but the cost of a Setrab or Mocal was too high at this time. The G-PLUS brand does feature a stacked setup, but it might be that a Setrab or Mocal have a higher cooling capacity (BTU). I'll now when I get rich and buy a Setrab... 90 degree AN-fittings can cause flow restrictions, so I chose to bend the hoses when mounting the 16 row cooler. With the larger oil cooler, this was no longer possible as the bends would get too tight. To my luck, AN10 90 deg fittings still have a large cross section so the engine oil pressure didn't drop.

The LC-2 should only be powered when the engine is running. I've also installed an electric power steering pump (EPS) which draws a high current, so if the ignition is left on the battery is quickly drained. LC-2 manual: Do not pre-warm the sensor before starting the engine, simply start the engine as normal. Allowing the sensor to pre-warm before starting the engine will increase the possibility of damaging the sensor from shock-cooling. I came up with the idea of using a voltage monitor, so that the LC-2 and the EPS only receives power when the battery is charging, indicating that the engine is running. The voltage monitor has two configurable set-points, a start voltage and a cut-off voltage. The voltage monitor controls a relay supplying the LC-2 (and the EPS) directly from the starter battery. . I mounted the hardware on a plate that I fixed to the back wall of the glove box. This provides easy access, as well as hiding the clutter away from view. A flyback diode is added to t

Trackday on Vålerbanen, 8 august 2021 My first trackday on sticky Hoosier tires. They provide magical grips levels, to an extent which requires pushing braking zones and cornering speeds far out of my comfort zone. Hope I'll be able to push harder next time. The throttle blip on braking is now managed by the Auto-Blip unit. It only took a few laps to calibrate it correctly, to get the delay and throttle blip to suit my driving style. The throttle-blip really helped to offload my brain on corner entry, where I've spent too much time coordinating all the steps. The engine is still running too hot when pushed above 5500 rpm, further cooling upgrades needed. Thanks to "Trackday Innlandet" for arranging the event.

It was time for a wheel alignment after installing poly suspension bushings. I also wanted to a more aggressive geometry better suited to circuit racing. I asked for zero toe front and rear, which in my experience evens out the wear caused by the negative camber. I also like the handling with zero toe.

My CPU appears to have limited processing power, spending too much time to complete a successful rev-matched down-shift while braking at the same time. The end result is that I brake too much and too late, burning off too much speed. As my CPU is a one-off special edition that can't be easily upgraded, I decided to help it with a co-processor - the Auto-Blip Intelligent downshifter. After a quick test drive after installation, I conclude that two brains works better than one. I can now focus on driving the car, while the Auto-blip handles the rev-matching. The ever so difficult downshift to 2. gear is now a breeze. Designed to fit in that spot? The Auto-Blip kicks into action when you brake and clutch simultaneously, blipping the throttle at a configurable delay. The amount of throttle blip (how much the revs increase) is also configurable. I did have some issues getting the unit to work in my C5Z. The manual states to only connect two off the APP sensors (throttle position sensors

The stock brakes hold up surprisingly well on track days, but rotors and brake pads burn off at an alarming rate. 2 track days on the rotors, 1-2 track days on the brake pads. I put a request on corvetteforum.com to purchase a second hand big brake kit. I got hold of an Wilwood Aero 6 kit, complete with spare parts and an additional set of new rotors.

Based on experience with tyre wear from the previous season, I knew that a set of Hoosier A6s wouldn't last long with the stock setup. With sticky tires, the rubber bushings deform too much, throwing off the alignment. Time for an upgrade. I was lucky to source a front and rear Energy Suspension poly bushing kit that someone had purchased, but not installed. Removing and reinstalling the upper and lower suspension arms was easy, although quite a bit of work on the rear, as the driveshafts have to be removed. The real challenge was to remove the rubber bushings. I tried with basic hand tools and a bench vise, but quickly gave up on the first bushing. Time to expand the toolset in the garage. A hydraulic bench press would be nice, but would take too much time - and money - to source. I found a nice toolkit for removing and installing bushing in the local hardware shop, which made the work surprisingly easy. With this toolset, you only need hand power to remove the bushings. The tools

With the original staggered setup, the wheels can't be rotated to even out tire wear. This is a big minus when doing circuit racing, as the front and rear tires wear quite differently. This problem is solved by mounting the same rim and tire dimensions front and rear - a square setup. The wider front tires improves the front end grip, and as a consequence changes the chassis balance from mild understeer to mild oversteer. I managed to source a set of C5 Z06 18x10.5" replica wheels with 315/35-R18 Hoosier A6 tires. It will be interesting to see how the A6s perform on circuit racing, as they are designed for short autocross sessions generating less heat. Sticky tires like these will not work with the stock suspension rubber bushings. Even if you adjust maximum negative camber, the rubber will deflect too much under load and screw up the alignment. End result is that the sticky tires can wear out in short time, especially the outer shoulder. To give the tires a chance to survive

With a large oil cooler in front of the radiator, I noticed that the water temperature exceeded 115 °C. At such temperatures, the ECU starts to pull timing to reduce engine power output. I resealed the radiator shroud, cleaned out debris, installed a 160  thermostat (71 °C) and lowered the fan settings with HP tuners, but this was still an issue. The stock radiator had developed a hairline crack in the plastic end tank, which I discovered by luck when running the engine without the radiator and the fan shroud removed. A DeWitts or Ron Davis radiator was my preferred solution, but after adding shipment costs and import taxes the total was above $1000, so I decided to go for the less expensive Engineering Cooling Products (ECP) radiator for the C5. The ECP radiator arrived without any visible damage, which is always a risk when having fragile parts transported long distance. I bought it with a consumable electrode, to replace the flimsy petcock supplied.  The radiator installed nicely an

While stationary in the pit lane on a track day, I observed the intake air (IAT) temperature exceed 70°C. It took almost a full lap at speed to cool down the intake air again. High intake temperature sets of a series of events which reduces engine power and response The ECU retards ignition timing above 30°C IAT. Increased risk of detonation. If the knock sensors detect detonation, the ignition timing will be further retarded by the ECU Time to do some improvements! By inverting the airbox and cutting the radiator shroud, cold air is drawn from the outside. I also decided to add thermal insulation to the airbox and shroud. It will be interesting to compare IAT readings in the HP Tuners log file before and after this modification.