gs450h Surge during heavy acceleration

[cpk]

Hi All,

Had my GS450H about 6 weeks now and I've noticed a surge/change/stutter (can't quite put my finger on it) during heavy acceleration around the 70mph speed.

Is this variable valve timing changing as revs rise?  Completely normal?

Apart from that I think the drivetrain is sound, regularly get 37-38mpg (I do long journeys) and no unusual noises etc.

Any help, advice would be appreciated.

Chris

[mkbean]

It does "change gear" around that speed, that may be it.

[Z28DUNC]

As Daniel says, I believe that is a kind of gear change as such. I think you would notice it under hard acceleration but necessarily if you drove steadily past 70/80. 

[cpk]

Thanks for the replies. That is reassuring. 

I don't notice it at driving steadily, only pressing on.

 

What is exactly happening during the hesitation? I thought the cvt would be smooth all the way and the 'gears' artificial for manual mode?

[KayCee]

i too noticed this and after research this is what i found out

from 0 to 80 is first phase then goes into second phase over 80

it then stops in this phase all the time unless you drop below 35 if you do it drops back to first phase and the cycle is repeated in essence nothing to worry about perfectly normal as designed by Lexus

so what i have read if you on motorway and go over 80 then as long as you dont drop below 35 you will be in the second phase of gearing which should [ give better fuel economy] or so i am LED to belieive i hardly notice mine much as i dont go over 80 very often

[cpk]

Interesting, thanks for taking the time to reply.  I suppose it goes into longer gearing? 

If that's the case then it might be worthwhile going over 80 at the start of your motorway/a-road drive!?

[Hangie]

From official Lexus materials:

 

Two-stage motor speed reduction gear

Unique to the GS 450h, the new hybrid transmission

incorporates a two-stage motor speed reduction gear,

coupled directly to the electric motor. A hydraulic control

unit, similar to a very compact automatic gearbox,

automatically switches the gearing between low (3.900) and

high (1.900) motor reduction ratio settings. In normal

conditions, during acceleration, the reduction system will

perform an imperceptible gear change at around 90 km/h

(56 mph). Hence, the twin stage gearing generates

maximum low-gear wheel torque for significantly enhanced

acceleration.

In short it is a small auto gearbox in a CVT gearbox :)

 

Short lack of power during hard acceleration is due to the fact that to change the "gears" you can have so much torque in the system.

When you are driving moderately torque doesn't needs to be limited for the change period and you wont feel it then. In general Lexus/Toyota got a problem with standard E-CVT gearbox like in Prius as GS got way more torque and this is theirs solution for that. As a curiosity is it still present in current GS generation ?

[KayCee]

well that shot me down in flames

i read this on US site andthought it sounded feasable

20 hours ago, KayCee said:

i too noticed this and after research this is what i found out

from 0 to 80 is first phase then goes into second phase over 80

it then stops in this phase all the time unless you drop below 35 if you do it drops back to first phase and the cycle is repeated in essence nothing to worry about perfectly normal as designed by Lexus

so what i have read if you on motorway and go over 80 then as long as you dont drop below 35 you will be in the second phase of gearing which should [ give better fuel economy] or so i am led to belieive i hardly notice mine much as i dont go over 80 very often

robert