Page 101 - Car South Africa (February 2020)

tech

jet. This must be checked and and asked us to collect the car
cleaned. There are adjustment the next day. We refused as the
TECH
screws on the carburettor but root cause of the fault was not ADVISER’s
you need to know what you are determined and we are not CHOICE
doing before adjusting these. We comfortable driving the vehicle
would revert all the adjustments unless this was found.
to the factory setting as a start if Before taking the car in, I
they have been tinkered with. spoke to other mechanics who ROLL CAGES FOR ROAD CARS?
One trick the mechanic can try mentioned the problem may be Please explain the following to me. Rally cars have
when the car is about to cut out dur- the master cylinder and I told reinforced roll cages to protect the driver and naviga-
ing idle is to squirt a little bit of fuel this to the dealership. I’ve since tor. Formula One racing cars have special bodywork

down the carburettor. If this helps, been noti ed there is a recall to protect the driver. In 99% of cases after a crash, the
the engine is starved of fuel. He can (bulletin in Opel speak) of this F1 driver runs back to the paddock and jumps into
also try and “choke” the engine by model and the master cylinder another car to continue racing. Normal road cars just
putting a rag on the carburettor’s will be replaced under warranty. crumple and occupants frequently end up in hospital
air intake during idle to see if it Could the problem be resolved or worse. Why not make cars as strong and safe so
improves. If it does, there may be an by changing the master cylinder everyone comes out alive?
air leak causing too much available only and not the slave cylinder? JIM JOHNSON
air during the idle condition. DAYALIN NAIDOO Via CARmag.co.za
Also, check the air-fuel ratio just Via email
above idle where the engine runs Interesting observation, Jim, that reminds us of an
with a gas analyser in the exhaust. Regarding the clutch pedal falling anecdote about the black box of an aeroplane. If the box
This will show if the engine is to the oor, it is plausible there is a is indestructible, why not construct the whole plane of the

running lean (too much air) or too problem with the master cylinder. same material?
rich (too much fuel). Slightly rich is Remember, a hydraulic clutch has As background, crash-test engineering is focused on dis-
ideal for a stable idle. a master cylinder connected to the sipating the crash energy in the longest timeframe possible
clutch pedal which builds pressure before it reaches the occupants. Stopping in a short distance
in the hydraulic line running to the from speed would result in high peak deceleration which
slave cylinder operating the clutch. can cause severe internal injuries, even if the occupants’
CLUTCH PEDAL Both units consist of hydraulic bodies do not impact any part of the vehicle.
ON THE GROUND pistons. The pressure created in the Rally cars are not practical for everyday use as the roll

My wife drives a 2016 Opel Astra uid by the master cylinder results cage restricts them to a two-seater with little or no boot

1,6T Sport with 28 000 km on in a force on the piston of the slave
the odo. The car has an inter- cylinder that, in turn, moves to op-
mittent problem that has oc- erate the clutch. If there is a leak in Stopping in a short distance
curred only twice, three weeks this system, pressure cannot build

apart. In the rst incident, the and the clutch pedal can drop to the from speed can cause

clutch pedal spontaneously oor. If there is no actual leak, with severe internal injuries
moved to the oor and became uid on the ground, the seals on

stuck. She could not engage a either the master or slave cylinder
gear and had to pull over, restart may not be functioning. It is more space. The driver and navigator are strapped in so tightly to
and all seemed ne again. plausible that the uid leaks their racing seats with a four-point harness they can barely

The second incident occurred back past the seals on the master breathe so it’s not very comfortable. There is no need for
when I drove the car. Both clutch cylinder side and is the reason for airbags in a rally car as there is little chance of an impact
and brake pedals slowly dropped the recall. with the dashboard, as the helmet’s Hans device limits the
to the oor and got stuck. I We are more concerned about occupant’s head movement. Although the safety cell of the

could not brake or change down. the brake pedal falling to the oor rally car is very rigid, the other areas are soft so it’s able to

Luckily, I was travelling slowly. I as this is a high safety risk. To deform, break off and dissipate energy as mentioned.
pulled over, restarted the car and our knowledge, there is no link The same argument goes for Formula One cars but you
everything worked, but I was a between the clutch and brake can add massive cost. Although the chrome-moly roll cage
bit shaken and drove straight systems so this problem needs a of a rally car is expensive, it does not come close to the
home and parked the vehicle. separate investigation and must carbon- bre structures employed in F1.

The vehicle was towed to the include the brake master cylinder, In short, we think occupant safety in road cars has come
local dealership. They checked brake booster and even the ABS a long way but, as you mentioned, maybe manufacturers

the brake uid level and drove pump. Start with a diagnostic can learn more from motorsport and see if additional safety
the car but found nothing amiss check to eliminate sensor issues. technology can be transferred to road cars.

CARmag.co.za CAR FEBRUARY 2020 99