z06vette.no

Heat management is still an issue on track days, so I decided to add a Trackspec hood vent. Trackspec T1 hood vent 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 second hand 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

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 I had to drop the launch RPM down to almost idle and modulate 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. Flyby at 1000 m

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.

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

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 I'm installing poly bushings and changing to  more aggressive suspension geometry  settings.

With the original staggered setup, the wheels can't be rotated to even out tire wear. This is a big minus as the front and rear tires wear quite differently. This can be solved by using the same rim and tire dimensions front and rear - a square setup. The wider front tires also improves the front end grip and shift the chassis balance rearward, which I prefer. The 14" Wilwood Aero 6 brake kit requires 18" inch wheels, and are known to fit behind the C5Z rear rims. I was fortunate to get two OEM rear Speedline C5Z rims from House of Wheels at a good price, in the same finish as on my car (there are variations in color).  They even survived the long distance travel from the USA to Norway without any dents. I have to issues with this configuration, no wheel arch or liner rubbing. This is how GM should have configured the C5Z.

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 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. Increased risk of engine ignition knock / detonation The engine ECU retards ignition timing above 30°C IAT If the ECU detects ignition knock, the ignition timing will be further retarded by the ECU Time to do some improvements! By cutting the radiator shroud and inverting the airbox, colder air is drawn from the outside the engine bay. The most noticeable improvement afterwards is the IAT drops quickly after leaving the pit lane on track days, which was my main goal.

 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

On the first track day with the Z06, the clutch pedal stuck to the floor as I shifted at high RPM. Imagine my surprise and disappointment. I could pull the clutch pedal up and continue, but it would repeat itself at intervals. I tried the "ranger method" numerous times to bleed the slave cylinder, but it didn't help.  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 drained and cleaned the reservoir and refilled it with new high temp brake fluid (Castrol React Performance DOT 4). I then applied vacuum to the master cylinder port using a Mityvac. As can be seen, a lot of air pockets and old fluid was released. The vacuum makes the slave cylinder collapse, which squeeze out more of the old fluid than when using the ranger method. New fluid is sucked in by the reminding vacuum when the MityVac hose is removed. I repeat

During the previous track day at  Vålerbanen in July 2020 , I had to run the engine at maximum of  5500-6000 rpm to keep the oil temperature below 140 °C if the session lasted more than 10 minutes. The C5 Z06 does not come from the factory with an oil cooler, but it is clearly required to avoid overheating the engine.  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 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. A thermostat also restricts the oil flow, by the nature of its design. Oil cooler installed. I decided it had to be installed in front of the radiators

I put the car on a weighing cell, measurement 1380 kg / 3042 lbs. The specified curb weight is 1440 kg / 3175 lbs. Ideally I should have weighed the car before I started to "add lightness". The weighing cell is calibrated annually, as it is used by the road authorities to verify compliance to regulations (e.g. total weight with a trailer).

“Adding power makes you faster on the straights; subtracting weight makes you faster everywhere" - Design philosphy of Colin Chapman, Lotus Cars. Why not apply it to the Z06? Adding power is expensive, removing weight is free. The air pump is not needed, the stock stereo is a disaster and the rear trunk looks almost as nice without the carpet. Trunk carpet removed Stock seats removed, the driver's side is replaced with a Sparco seat I put all the small parts in a bag to get the total weight Stock head unit, CD changer and speakers Secondary air injection pump and piping Power steering pump Fuel rail covers Air filter cover Rear trunk plastic covers Rear trunk lamps Tire puncture kit Weight of parts in bag 20 kg / 48 lbs Rear trunk carpet 6 kg / 13.2 lbs Rear trunk lid 2 kg / 4.4 lbs Floor mats 2 kg / 4.4 lbs Hood liner 1 kg / 2.2 lbs Passenger seat 14 kg / 31 lbs Driver seat 16 kg - Sparco Evo 12 kg = 4 kg / 8.8 lbs Total weight saving: 20 + 29 kg = 49 kg / 108 lbs  😎

The GM engineers allocated space for a starter battery in the trunk, but it remained in the engine bay until the release of the C6 Z06. I decided to replicate the setup as it improves the corner weight balance by shifting weight to the rear right wheel, which is the lightest corner of a stock C5. For the power cable, I used a heavy gauge 50 mm2/1 AWG multi stranded copper cable cable and press fit terminals. The heavy gauge is necessary to reduce the voltage drop caused by the long stretch and the high current required by the starter motor.  The ground cable is connected to the chassis, which is available in short distance from the battery inside the right wheel well. I installed a 350A automatic fuse next to the battery. The power cable is then routed forward above the right wheel well and then follows the existing wiring in the door sill to the front. With a battery in the passenger cabin it important to use a battery which does not emit harmful gases, so I used a sealed SMF battery.

The boot lid clicks open with a button, but annoyingly enough it does not raise high enough to slide a in a hand. Eventually, the paint wears away as you grab one of the corners to raise it. I installed a spring from an old welding cable, which helps to push the lid further up when opened. Problem solved! Cost $0.

The GM key fob has no tactile feedback, it reacts slowly and the rubber caps wear out. Fortunately, someone has reprogrammed VW key fobs to work with GM cars - and the Corvette C5. You have to cut the stock key in half. Make sure that you don't cut too far down, otherwise the key will not fully enter the ignition lock - making it impossible to turn the key (BTDT). More information and links to e-bay on the  Corvette Forums

Clutch pedal throw on the C5/Z06 is far too long. On track days, I can literally watch other cars gaining distance during a gear change. Trying to speed up the pedal movement only results in bad timing and loss of traction. Inspired by the thread at Team ZR1, I made a clutch pedal stop to reduce the throw length.  In most cars, the last part of the pedal travel is a waste, as the clutch is fully released with less movement of the slave cylinder.

Analog audio broadcast is history in Norway and replaced by DAB (Digital Audio Broadcasting), and with a CD changer trying to play Johnny Cash and Mark Knopfler simultaneously, I was left with a useless head unit. No radio, no CDs. I didn't want to spend too much money on an expensive and heavy 2 DIN unit and speakers, so the head unit is now replaced by an old Windows tablet and a single board 2x50W amplifier with bluetooth. The Bose door speaker units are replaced by two 6.5" speakers and new speaker cable wiring (the existing speaker wires can't be reused, as they are wired for a differential configuration). Total cost less than $150, with a "head unit" with much more capabilities than a traditional 2 DIN unit. I can install my own software and configure it completely to my liking, and even use it with HP Tuners to display engine management data. As the head unit was replaced by a single board amplifier, I blocked off the location using plexiglass. When you pa

Oily bottom end With an oil pan soaked in oil, it was time for repairs.  I had planned to replace the harmonic balancer with an ATI underdrive unit, but it was simply too expensive after adding shipping costs and 25% VAT. I decided on an OEM PB1117N Dayco balancer. Ouch, what a mess I found non-factory sealant between the front cover edge and the oil pan, so someone has previously serviced the engine. They obviously didn't care about centering the front cover and seal, which resulted in uneven wear of the seal, which again wore down the sealing surfaces of the harmonic balancer. To avoid a revisit later on, I decided to change all other parts that could be causing an oil or water leak in this area. Front cover gasket, water pump gaskets, front end seal. The lower oil pan gasket was changed last year. Removing and reinstalling harmonic balancer The first attempt at removing the balancer failed. I retried with a stronger puller with a sharp end tip, which would secure itself securely