GS450h acceleration flat spot at 65mph

[Alexw]

A steady acceleration using 60% throttle from 55-70mph is smooth however if using 100% throttle from 55-70mph when reaching 65mph it is as if the throttle has been backed off to 50% but just after 67mph it is back to 100% & continues to accelerate as pre 65mph. Any thoughts? Faulty mass airflow sensor perhaps? 

[Anevb]

3 hours ago, Alexw said:

A steady acceleration using 60% throttle from 55-70mph is smooth however if using 100% throttle from 55-70mph when reaching 65mph it is as if the throttle has been backed off to 50% but just after 67mph it is back to 100% & continues to accelerate as pre 65mph. Any thoughts? Faulty mass airflow sensor perhaps? 

It's the way it works. Mine is the same. To me it feels something like a gear shift in a car with conventional gearbox. I've watched videos where the same happened (before I even bought my car) so I wasn't worried when I experienced it. 

[Mihanicos]

During hard acceleration MG2 draws current from the traction Battery to assist acceleartion. Given that the traction Battery is limited 6.5 ah, when the traction Battery capacity is used up, there is a drop in acceleration. The MG2  power is about 148 Kw, if my memory serves right, about half the engine power.

When going down mountain roads and you engage 5th, 4th or 3rd gear, for as long as the traction Battery is being charged, you have significant breaking to maintain the car in the desired speed.

When the traction Battery is fully charged, you will notice the car suddenly goes down the hill as if you shifted out the lower gear to neutral.

Chris

[Alexw]

Thanks for your replies. Interesting that others have experienced the same sudden loss of power blip under full throttle which instantly recovers. 

It happens even if the traction Battery is at 70% but the hard acceleration recovers after 68mph or more so I am thinking more of a software design fault if other have the same issue. 

Compared with a 2021 Toyota Prius with much lower power, the Prius has smooth acceration at 100% throttle from 0 to 70mph + without any sudden loss of power like my 2007 GS450h does

[bigglesfllesundone]

GS450h has a cvt and also a two speed automatic, this changes up at 55mph usually, but can change up at higher speeds under high acceleration.This may be what is giving the sensation of throttle backing off at 65mph.

A sluggish change of this gear may be a sign of the auxiliary transmission pump being on the way out. See the thread ‘GS450h loss of power’ on the general GS board, particularly the posts by Hayne in that thread from 26/12/14.

[Alexw]

Thanks for the heads up. I didn't realise there was cvt multi changer that is actived by transmission fliud Pump between 55-70mph. I have just looked up the 'loss of gs450 power' post from Haynes in 2014 & that sumarises all the symptoms I am experiencing. So possibly a failing pump. 

Saddly I don't have the DIY skills to attempt a repair myself but a least I now know what to ask a garage to quote for. 

Many Thanks for your advice

[Anevb]

What I am experiencing is exactly as on the video. Go to 0:33. Is your car "shifting" slower @Alexw?

 

 

[Alexw]

Yes that's exactly it. In the video the auto gear change is a very slick change compared to my older 2007 model which is slower to change, but now that I have learned that there is an extra automatic gearbox in addition to the cvt it makes perfect sense. I will now be able to understand what is going on when accerating from 55mph upwards & alter the throttle demand accordingly to allow the auto gear change to take place more smoothly. 

Thanks for all the information