When technology isn't ready no amount of wishful thinking will make it so.

MTA hasn't purchased a hybrid bus in three years - and new diesel engines could make a return

The MTA’s electric revolution is grinding to a halt.

The agency hasn’t purchased an electric-diesel hybrid bus in three years, and as many as 389 — 23 percent of all its hybrids — could be retrofitted with new diesel engines soon, MTA officials revealed to The Post.

Union officials warned that the switch will come with a great cost — to the public’s health.

“It’s a slap in the face if they start going back to diesel again,” said a skeptical transit-union source. “It’s not good for people’s lungs.”

But the city may not have a choice, since hybrids haven’t worked very well, an insider says. Maintenance workers “constantly” have to repair hybrid engines.

Helayne Seidman

ROLLING TO A STOP: MTA is pulling out some broken hybrid engines and replacing them with all-diesels.

“The electric-traction motors are burning out,” the source said. “They’re so expensive to replace that it’ll be cheaper to stick a diesel engine in there.”

A July 2012 contract between the MTA and Indiana-based engine manufacturer Cummins Inc. confirms that the MTA is evaluating how to convert hybrid buses to a “diesel-engine-only application.”

The switch comes at a time when both President Obama and Mayor Bloomberg are calling on government to reduce emissions by using cleaner fuel sources and adopting more efficient fuel standards.

But the MTA argued that new diesel engines are actually cleaner than hybrids, which conform to 2004 Environmental Protection Agency emission standards, according to Henry Sullivan, the MTA’s chief maintenance officer for buses. The new diesel engines conform to stricter 2007 standards.

“When we first went with the hybrid in 2004 that was the way to go,” he said. The diesel is “better than the hybrid now.”

The new diesels “approach or exceed the emissions profile of a hybrid electric,” added spokesman Charles Seaton. “In high-speed operation, they work better.”

According to Seaton, 1,677 out of 5,719 city buses are hybrids.

The ones operating in Manhattan will not be phased out because they stop more frequently, and the electric components of hybrid engines function better with more stops.

Hybrid engines that would be replaced are in buses that roll in the outer boroughs, where high-speed transit and less frequent stops are more common, Seaton said.

“The power plant on a hybrid engine is a diesel engine,” he emphasized.

But the TWU source argued that better fuel efficiency is not the primary reason for the phase-out — it’s the cost of fixing and replacing the hybrids’ traction motor, which is supposed to last as long as the bus itself.

A five-year warranty on 100 hybrid buses is set to expire, which means repairs to the buses’ engines will no longer be covered by the manufacturer, the source said — meaning the MTA would now have to pay for fixing them.

The MTA began phasing out all-diesel bus engines in favor of electric-diesel hybrids about 15 years ago. The first 10 hybrids, which cost $1 million each, began running in 1998. Ten years later, the authority introduced the roll-out of 850 hybrids, billing them as “sleek, modernistic and efficient.”

When the MTA last ordered hybrids about three years ago, it paid between $700,000 and $800,000 apiece for them, Seaton said. Since 2010,the agency has purchased $500,000 diesel buses because they’ve become more fuel-efficient.

Back then, each hybrid saved the authority about 50,000 gallons of diesel fuel. The batteries were also more efficient than their diesel engine forebears and weigh 800 lbs. less than the 4,000 lb. lead-acid batteries in those diesel buses.

But the hybrids have come with their share of problems too.

Two burst into flames in 2009. And last year, The Post revealed that scofflaws were using a switch located on the outside of the buses to shut them down while in service.