The invisible challenge of rallying in Mexico

Air, or lack of it, will give cars a hard time next month

Suninen M-Sport Mexico

There’s not too long to go until rally cars get started on Rally of Nations Guanajuato, but while it will be fun and exciting to see them tackle some of Mexico’s iconic stages, it won’t be without its challenges.

Next month’s Rally of Nations stages will take place in the mountains in the same region as Rally México has done in the World Rally Championship, and at times cars will be sent to over 2000 meters above sea level.

It’s hell, especially for the engines and the turbos. The altitude means there’s less oxygen in the air, and if there’s one thing modern rally cars need, it’s oxygen.

The engine requires oxygen in order to burn the fuel, but if that oxygen doesn’t exist, the explosions needed to generate the power don’t happen. If there’s only a small amount of oxygen, then the injectors can only supply a small amount of fuel, meaning the explosions will also be small.


It works in the same way to your body.

Think about it from this perspective. You’re a runner. In order to be able to run you need oxygen and as much as possible so it can get into your bloodstream, providing you with the necessary energy to move your legs at speed.

A fit runner will have bigger lungs, catering for higher levels of oxygen, which can then be transferred to the bloodstream in bigger doses. An unfit runner will have smaller lungs, resulting in less oxygen being transferred and they therefore won’t be able to run at the same speed as their fitter counterpart.

The unfit runner will also run out of speed earlier since they will be working harder to try and keep at the same pace.

To continue the analogy in rallying terms, the fit runner is the car in other parts of the world and the unfit runner is the car in Mexico.

The thinner air means that not only can the car not produce as much power as it otherwise would, but it will also undergo more stress in the process, while also raising the likelihood of a reliability failure.

Teams can try and counteract some of the strain by making adjustments to the turbos. They can limit the turbine speed ensuring that the turbos themselves don’t undergo any excessive stress loads, but it doesn’t help the top speed. No matter what, the cars will be slower in Mexico than they would elsewhere.

Speed isn’t the only issue. Cooling can also pose a problem in the thin air, especially in a country like Mexico where the ambient temperatures are rarely sub 20°C.


The thinner air density means the air can’t cool the car to the same extent as it would if being run closer to sea level. Yes, radiators are there to keep engine temperatures stable, but they’ll have to work harder, since for every revolution they will move less air.

It’s the same with the brakes. Less air will flow through the ducts, meaning it will be harder to keep the braking temperatures under control.

Quite simply, if you put monstrous rally cars on top of mountains and push them to their limit, they are going to find life tough. But isn’t that what it’s about?

It might mean some cars end up failing to make it to the finish. It could mean your favored driver ends up leaving early, but it also creates a sense of trepidation, intrigue and excitement, and makes it all the more rewarding for the eventual victor.