THE RAINY SEASON has officially begun. Torrential rain presents unique challenges to drivers that can catch them off-guard, including reduced visibility, slippery surfaces, unseen obstacles and flash floods.
With high stance, traction control and stability systems, the Chevrolet Trailblazer midsize SUV and Chevrolet Colorado pickup offer a distinct advantage over smaller cars because they can wade through water as deep as 800mm. Other functions such as auto rain sensors and automatic headlights also allow the driver to focus on driving and pay attention to surrounding situations.
Before the premium SUV and iconic American pickup truck contended with actual monsoon conditions, validation engineers at General Motors subjected the vehicles to extreme water intrusion tests using dunk tanks, water spray booths and flooded trenches.
“Truck and SUV customers around the world expect to get to their destination no matter what’s happening outside the vehicle — be it a flooded road, river crossing or storm,” said Chatchawan Chantaket, general director of Product Engineering, GM Southeast Asia. “When you think of all the sensitive equipment on vehicles these days it is critical to ensure that Colorado and Trailblazer customers will never have to worry about how their vehicle will perform in extreme conditions.”
GM’s dunk tank simulates static water fording, like when customers are idling in deep water during flood conditions like those that frequently occur during Thailand’s rainy season. Water floods into the dunk tank up to the truck’s rocker panel, allowing engineers to examine the effect on underbody and chassis components, such as electrical wires and venting systems. The dunk tank test was inspired in part by the kind of severe flooding that occurs in Southeast Asia every year, impacting millions of motorists.
GM’s universal water test booth helps determine long-term reliability by using 330 nozzles to spray 3,123 liters per minute for eight minutes from the bottom, sides and top. This tests the robustness of a vehicle’s door and window seals to ensure no water leaks into the cabin during a severe rainstorm or other wet conditions. The test also helps ensure that water doesn’t interfere with powertrain venting systems and other underbody components.
The universal water test booth also enables a test that simulates the kind of misty conditions found in places like the northern Thailand. A fine mist can creep into areas of a vehicle that larger drops of water do not, potentially creating a leak by having water wick through weather strips.
GM’s 15-meter outdoor deep fording trough is designed for slow treks through water, like a stream crossing during a camping trip when water intrusion can compromise transmission fluids and powertrain components like the rear exhaust.
GM engineers also use high-pressure sprayers to test charge ports, powertrain vent and fuel system vent systems as well as vehicle air induction systems behind grille openings to ensure that consumers who do the same won’t damage components.
“Hopefully, most of our truck customers will never have to deal with extreme water conditions, but in case they do they can take solace in the fact that we’ve designed our vehicle components to handle it,” Chatchawan said.
DRIVING THROUGH FLOODED ROADS
When driving through flooded roads, there are four things that a driver should always remember:
• Check depth
• Proceed cautiously
• Go slow
• Avoid stalling
Chevrolet recommends never driving through anything you cannot see or walk through, or is deeper than the center of your wheels. Large SUVs and trucks can operate in deeper water, but find out what is the fording depth specific to your vehicle.
Floodwater hides what is underneath. So, if you have to drive through a flooded stretch, make sure the road is still underneath the water and not washed away. Also be wary of unfamiliar roads that may have dips too deep for fording. Alternatively, stop and observe if others can drive through it safely.
If you have to go through a flooded road, aim for the “crown” of the road, or near it, as the water is at its shallowest here. Use high revs and a low gear — first or “L” depending on the type of transmission. Keep a constant speed. Do not take your foot off the accelerator. A decelerating engine may induct water through the exhaust pipe and damage the catalytic converter. You also do not want the air filter in front to ingest water into the engine so drive very slowly. In both cases, damage will be severe and repairs costly.
Ease into the water at no more than 3 km/h, and increase to 6 km/h in the water. This will create a bow wave in front of the vehicle and a depression in water level around the engine bay, reducing the chance of water induction via the air filter and also damage to electrical and electronic components. Speeds higher than this will just push water into the engine bay through the front grille.
Proceed one vehicle at a time so you will not be forced to stop in the middle if the vehicle in front stalls. Also ensure no vehicles are coming the other way, as the wake it creates may drown your vehicle, especially if it is moving at unreasonable speeds.
Once out of the water, apply the brakes gently to dry them. “Ride” the brake with your left foot if you are familiar with this technique. Release when you feel the brake starts to “bite.” Also stop to inspect and ensure nothing such as plastic bags or other debris is stuck in the grille or radiator fins behind it.
Keep this in mind the next time you drive in the wet — 15cm of water will reach the bottom of some passenger cars; most passenger cars will start to float in 30cm of water; 60cm of flowing water can sweep most vehicles — even SUVs — away. It is not the speed of the flow, but the force and volume, so do not take risks.