Hi!

I bought recently used Mazda 6 Kombi 2.0 Advance, manual, year 2010. Few days ago I noticed strange behavior which I would like to ask your opinion about.

I was driving on a highway and there was a long and very steep road climb. I was driving 120 km/h on 6th gear (I have manual transmission). I noticed that car didn`t have enough power to continue the same speed however much I pressed gas pedal. It slowed down to 110-100 km/h and I couldn`t make it go faster. It made me a bit concerned - I would expect this car has enough power to just run over even steep climbs on 120 km/h when unloaded.

That same day I had to go the same road climb again. I was driving same 120 km/h but this time with cruise control (turned on on 6th gear). I paid close attention to how car behaved and observed that it was going 120 km/h with no problems at all on that same climb. I even didn`t notice any changes in the way engine sounded. So I was at least relieved that car has that power to make such climbs.

The question is - how cruise control did it and where I failed to do it manually? If I enable cruise control on 120 km/h while I have 6th gear enabled, I would expect cruise control cannot shift on a lower gear by itself if it feels that more power is needed to climb? If so, why pressing gas pedal to maximum in manual didn`t produce the same result as cruise control?

 

Maybe I'm missing something, but I strongly doubt there is any difference in available power between Cruise Control mode and normal driving mode. That said, if 120 km/hr is near the limit of your engine to pull the car up the grade, and there was a head-wind on the first trip and no wind, or better a tail-wind, then a 10 km/hr difference is easily understandable.

 

Thanks for reply. Probably it was wind, that would be an explanation.

 

I was thinking about this thread while out for a run on Friday; the OAT was up in the high 90s and it was really humid and two other possible factors came to mind; heat and A/C. If the trip up that hill was done on a really warm day with the A/C cranked, your engine would feel down on power for two reasons:

1. Engine power is reduced the warmer and the more humid the air is, and
2. I've heard the A/C system can draw as much as 8 hp from an engine; a pretty fair amount given the specs of small(ish) 2.0 liter motors.