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End of 2022 season

Winter is coming. The C5Z is in hibernation until spring time. I don't have an insulated garage, and doing any kind of work 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 repair I returned from the last trackday with a groaning noise from the rear end of the C5Z, which is probably a differential failure. It might only be broken belleville springs, worse damaged bearings and/or bearing carriers, worst case broken pinion and ring gear - or a combination of all.  No matter what, the differential has to come out. This sets of a train of repairs, as the car already have some other issues that requires attention sooner or later. The drivetrain repair train, which started rolling back in 2003 and now reaching its destination 20 years and 106300 miles later. Engine rear oil seal leaks Worn slave cylinder (&q

C6 Z51 330 mm rear brakes

Don't drive with your nannies on! With active handling in "competition mode", yaw control is still active. The rear brakes are used to correct slides/excessive yaw on corner entry and exit. This cause the brake rotors to run hot, and in my case one of the rotors cracked as it cooled down in the pit (I even heard the *PING* as it happened). 295 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 share the same caliper and parking brake dimensions. The Z51 rotors are ventilated on both sides, have a higher mass and increase the swept diameter of the brake pad. This should increase the thermal capacity compared to the 295 mm C5 rotors. The increased rotor diameter causes a braking torque increase of ~ 10%, which could affect the front to rear brake bias. The C6 Z51 caliper has a smaller diameter piston to compensate, but I'm expecting the marginal brake torque increase to be within the capab

Trackday report

Finally time for a new trackday, Vålerbanen again. This time with a larger 25 row oil cooler and a Trackspec hood vent, in an effort to lower engine temperatures further. To my frustration, the oil temperature still climbs too high when the engine is ran above 5500 rpm. I can maintain max attack for 1-2 additional laps compared to before. So there will be a "Never ending oil temperature story - part 4" Except for the temperature issue, the car ran great. Engine, clutch, gearbox, brakes, tires - not a single hick-up. I set a new personal best time, and judged by the video, cutting the lap time a further 1 second 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. Sorry, the video is without audio - wh

Window regulator replacement

High up in the mountains in Norway, close to freezing temperatures, the driver side window regulator broke down. Perfect timing. 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 regulator in place. Tip: Before tightening the bottom nuts, I ran the window all the way down so that there wouldn't be any tension on the mechanism, making the regulator work harder than necessary. I followed Chris Askew's guide to replace the regulator:  https://www.chrisaskew.net/blog/2020/12/8/how-to-replace-window-regulator-2003-c5-corvette

Trackspec T1 hood vent

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

1000m runway drag

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.

Rear spoiler - SpoilerKing 284P

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.

Upgrade from 16 row to 30 row oil cooler

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 G-Plus 30 row oiler.  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. I have to admit that I'm using a "Made in China" 30 row oil cooler. The G-PLUS brand do feature a stacked setup, but it might be that a quality oil cooler from Setrab or Mocal will perform much better.

Electric power steering and wideband voltage cutoff

The electric power steering pump (EPS) draws high currents, so if the ignition is left on the battery is quickly drained. I've also installed an LC-2 wideband controller, which should not powered/heated without the engine running 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 shockcooling.  I came up with the idea of using a voltage monitor, so that the LC-2 and the EPS only receives power when the starter 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, as recommended by Innovate. . I mounted all the hardware on an acrylic plate that I fixed to the back wall of the glove box. This provides easy access, as we

Trackday with throttle Auto-Blip

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.

4 wheel alignment for trackdays

It was time for a wheel alignment after installing poly suspension bushings. I also wanted to adjust more aggressive geometry due to track day duty.

Auto-Blip, down-shift rev-matching

My CPU (brain, that is) 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

Wilwood Aero 6, 14" big brake kit

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.

Energy Suspension poly bushings install

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

Hoosier A6 tires on square setup (4xC5Z 18x10.5")

With the original staggered setup, it is not possible to rotate the tires to even out wear. A square setup solves this, as well as improving front end grip, changing the car balance from mild understeer to mild oversteer, which I prefer. I managed to source a second hand set of 315/35-R18 Hoosier A6 mounted on replica C5 Z06 18x10.5" rear rims. It will be interesting to see how the A6s perform on circuit racing, as they are designed for shorter autocross sessions generating less heat. To give the tires a chance to survive, I'm installing poly bushings and tuning in more aggressive suspension geometry settings (camber/caster/toe).

Engineering Cooling Products (ECP) radiator

After installing an engine oil cooler, I could start shifting at higher RPMs on trackdays without worrying about engine oil temperature. Only to discover next issue, the water cooling capacity is also insufficient for hard trackday work.  I had resealed the radiator shroud, cleaned out debris, installed a 160  thermostat (71 °C) and lowered the fan settings with HP tuners, but still water temperature exceeded 115 °C. At such temperatures, the ECU starts to pull timing to reduce engine power. 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. 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 pa

Flipped airbox to reduce air intake temperature

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.

Track day - VACN Solør

 A new track day, where I could have fun on the track without worrying about the health of the car. A new engine oil cooler kept the oil temperatures down while a vacuum bleed and fluid change of the clutch slave- and master cylinder solved gear change issues on high RPMs. View from Nissan R32

Bleeding clutch master and slave using vacuum

On the first track day with the Z06, the clutch pedal stuck to the floor and had to be pulled up. This only became worse with time, and the clutch pedal would get stuck as soon as I tried shifting at high RPMs. I tried the "ranger method" numerous times, but it didn't help. Gearshifts were also harsh, so I though that the synchronizers were bad as well.  I was about to start pulling down the exhaust etc to access the bleed screw, and purchase a Tick Master Cylinder, but then I found this thread: Clutch bleeding from the mc I figured I should give it a try: I filled the reservoir with new fluid and used a fitting delivered with the MityVac. As you can see, a lot of air pockets and old fluid was released! While at it, I also performed the following: Removed clutch pedal assist springs Refilled with high temp brake fluid (Castrol React Performance DOT 4) Added heat insulation to the clutch line, which is passing right below the exhaust manifold (I released the line from the

Adding an 16 row engine oil cooler

During the previous trackday at Vålerbanen in July 2020 , the car was running too hot, and I had to limit the RPMs to keep the temperature down. With the engine oil temperature exceeding 140 °C, I decided that this had to be solved before the next track day coming up, to avoid an engine failure. The stock temperature sensor is M12x1.5 while the oil cooler block is 1/8 NPT. I decided to drill and tap the correct M12x1.5 thread, which worked out nicely. I thoroughly cleaned out debris using brake cleaner and compressed air.  Oil cooler brackets being made Finished brackets (I wish a drill press for Christmas, working free hand doesn't quite provide the accuracy and finish I wan)t. New oil cooler block installed.  The part of the hoses passing by the exhaust manifold are protected by additional heat insulation. This block  has no thermostat, as I simply cover the oil cooler with a sheet metal plate when not doing track days.  Oil cooler installed. I decided it had to be installed in f