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Wayland's McLaren 720s Misfire

Updated: Jan 22

When our customer called us with a misfire above 100mph, like many McLaren experts our mind went to spark plugs or a failed coil. These are both somewhat common issues on the 720s. It would've been easy to sell the spark plugs and replace the coils on the cylinders that were experiencing the problem. Many shops without the proper tools may have had to resort to this.

Thankfully we are equipped with dealer-level diagnostic tools, advanced data logging equipment, a chassis dyno and most importantly the knowledge and experience to use them. Being able to log the factory McLaren engine computer and then analyze what was happening, we found the aftermarket ECU calibration was making the car run so rich at higher RPM, it was causing the car to sputter and misfire. This 720 in particular didn't need any new parts at all, just to have the ECU re-calibrated.


Prior to the visit to Cannonball, the car had come in with an off-the-shelf tune simply loaded in and was then sent out the door. Without any dyno testing or logging of the car after the tune was loaded in, the problem went unnoticed. Doing engine tuning this way is not only leaving horsepower on the table, it can be damaging to your engine.

After discussing our findings with the customer, we removed the cars engine computer and sent it out to our partner M-Engineering. There they unlocked the ECU and install their proprietary M-Tuner Suite.

The customer chose to go with the optional switchable calibration maps and the rolling anti-lag features. The M-tuner allows the factory McLaren computer to have features not found with any of the other tunes available for these cars. Normally features like this are only found on very expensive aftermarket stand alone engine management systems.

Switchable Maps - The ability to switch between calibrations for 91, 93 & 100 octane using the cruise control stalk. In addition, a valet function to reduce power when your car is in the hands of others.

Rolling Antilag - A launch feature for racing while already moving such as roll racing. It builds boost pressure while maintaining a constant speed. Let go of the switch and the car catapults forward like it was launched from a dead stop eliminating dreaded turbo lag and winning you the race!

With the engine computer back with the M-Tuner Suite and calibration installed we set out to carefully data log the car in order to optimize the tuning with M-Engineering. With every 720 being a little bit different, each calibration has room to be tweaked for maximum power, reliability and above all safety. With all of the right equipment in-house, it makes this process seamless giving the customer peace of mind.

Through proper diagnosis we were able to quickly resolve the problem effectively and accurately. No extra time or money was spent trying to resolve the issue. The icing on the cake is the car left properly tuned and making more power and safely to boot.

Cannonball Garage is your Chicago area McLaren, Audi, Mercedes-Benz, Lamborghini & GT-R specialists. We offer maintenance, service, repair, performance and dyno tuning and are an AMS Performance Authorized Installer.



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