Honda cannot reproduce on the race track the performance and reliability its power unit is getting on the dyno.
The Japanese manufacturer had scheduled a significant engine upgrade for Montreal, but ultimately held back on the update to extend development and testing.
Honda F1 boss Yusuke Hasegawa reported that engineers are struggling to validate on the race track the numbers they are seeing on the dyno.
"We can’t create good conditions on the dyno," Hasegawa told Motorsport.com.
"We need to create the same conditions from the track on the dyno. The operational conditions are different so we need to understand why that makes a difference to the reliability.
"Last year, we could prove engine reliability on the dyno so we need to understand why now there is some difference from dyno to the circuit running - it’s not easy.
"We need to improve the accuracy."
In addition to being deprived of the upgrade, McLaren suffered power unit component failures on each of its driver's cars.
Fernando Alonso was forced to retire from Sunday's race just two laps from the checkered flag when his engine expired while Stoffel Vandoorne was hit with an MGU-H failure in FP2.
“We have the countermeasure part but we didn’t introduce it in Canada because we would get a penalty,” said Hasegawa.
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