The power pole fell into the hedge and sparks from the live wires started the fire, he said.
"The fire in the hedge was quite intense."
It took firefighters an hour and a half to free the man from the wreckage of his car.
Te Puke Constable Kurt Waugh said it appeared the car's brakes locked up causing it to leave the road. The front driver's side of the car collided with the power pole trapping the driver by the legs, he said.
Rally organisers stopped the race after the crash.
Pukehina fire chief Errol Watts said the car had come over the hill at about 180kmh but was slowing down when the crash occurred.
"There was some braking when he hit the pole but he absolutely demolished the pole and the frame on the car was extremely strong and it just bowed in. He must have been doing a fair rate of knots when he hit it," he said.
Mr Watts praised the actions of the rescuers.
"He started to have some light blistering. Much longer and he would've been [in trouble]," he said. "He was extensively trapped. It was a rally car so all the extra reinforcing made it harder to get him out."
Once freed, Mr West - who was conscious throughout the ordeal - was treated, driven to the BayTrust Rescue Helicopter that was parked in a nearby field and flown to Rotorua Hospital with fractured legs.
It was also a close call for two spectators who were sitting about 2m away from the power pole, Mr Watts said. The charred remains of their chairs could be seen beside the blackened bush.
Nearby residents Warrick and Melissa Mortensen knew there had been a crash when the power went out as they were having lunch at home.
They came out to see what was going on and found the crash had taken place exactly where they and their young baby had been watching from earlier in the day.
"There was fire in the sky and everything," Mr Mortensen said.
Motorsport New Zealand general manager Brian Budd said the driver was still in hospital with broken bones but his injuries were not believed to be life threatening.
He expected to receive a full report from the club that organised the event tomorrow.
"It is motor racing and it does happen," he said.