That is the claim of Marco Canseco, the correspondent for the Spanish sports daily Marca.
McLaren-Honda debuted its novel, ultra-compact 'size zero' concept last year, where the tight packaging of the rear was possible because the turbo is located actually inside the 'vee' of the engine.
According to Britain's Motor Sport Magazine, the Honda turbo is bigger for 2016, with Yasuhisa Arai confirming that it will be "around the same size" as the Mercedes unit.
The 'size zero' concept, however, is staying.
Writing in Marca, Censeco said Honda test-bench runs since the first full 2016 chassis was put together confirm the turbo V6 is now more powerful but "the new turbo repeatedly breaks".
And "apparently there are still overheating problems, even though the new (turbo) now works at lower rpm of about 100,000 compared to the 120,000 of last year", Canseco added.
Marca said that after Sunday's online launch of the MP4-31, it is believed Fernando Alonso will be at the wheel on the opening day of Barcelona testing.
|Honda rumored to have found 200 HP but the engines keep blowing up|
01/29/16 (GMM) For McLaren-Honda, the rumors are running as thick and fast as the expectations of a much better campaign for the famous Anglo-Japanese collaboration.
2015 was a horror reunion for the old partners, but recent speculation suggested Honda has found a staggering 200 horse power over the winter.
Another rumor, however, is that the step forward has come at a cost.
Auto Hebdo, a specialist French outlet, claims Honda's 2016 power unit has proved unreliable on the test benches so far.
"According to our information, Honda is already preparing a fleet of replacement engines, as four per driver will not be enough," it said.
Marca, a Spanish sports newspaper that closely follows the career of Fernando Alonso, revealed that McLaren's 2016 car will be launched online at about midday on February 21.
The following day, it will hit the track at Barcelona.
Hopes will be high, but team boss Eric Boullier is confident the exactly two years he has spent at McLaren is now ready to show its results.
"It (the racing team) was oversized and difficult to manage," the Frenchman is quoted as saying by Marca.
Also difficult to manage, Boullier admits, are Alonso and fellow champion teammate Jenson Button.
"They, like all other champions, think only about winning," he said. "Until they have what they want they will not stop pressuring the team.
"But if you know how to manage expectations and calmly explain how things are moving, then you earn their trust," said Boullier.
He said although the results in 2015 were bad, he is happy that the new McLaren structure is at least now working efficiently.
"Momentum leads to success," said Boullier.
"You have to remember that when Red Bull bought Jaguar, it took five years to structure everything and become efficient.
"We are also in an ultra-competitive environment, fighting with Mercedes and Ferrari, and their level and quality is very high," the Frenchman said.