A second's silence when accelerating

[Harald]

Hi,

after the first 2000 km, I wonder about a delayed reaction when accelerating with a kickdown for overtaking.
The time between kickdown and real start of the 100% acceleration is perhaps 0,5 second...

Does anybody have an idea if this behaviour might be changed?

Best regards, Harald

 

[anko]

A delay of 0.5 seconds delay sounds not bad at all, so I assume you are referring to situations where the engine is already running? If not, the delay is probably more than 0.5 seconds and you may be able to shorten it by selecting Charge mode before overtaking.

 

[maby]

There are a few circumstances under which it can be a bit laggy even with the engine running. I tend to drive with the speed limiter engaged if the speed limit is less than 70mph and usually have the accelerator well depressed while cruising. When I turn off the speed limiter, there is a noticeable lag before the car begins to accelerate - even if the petrol engine has been running already.

 

[Harald]

Yes, I am referring to situations where the ICE is already in operation.

Such delay prolongs the needed space for overtaking on a small road in a way that has to be considered. Would be really nice, if it could be done better.

I do not expect that MMC will change its approach but could imagine that third party solutions for the motor managment react differently?

Harald

 

[anko]

Yes, I am referring to situations where the ICE is already in operation.

At speeds above 40 MPH then? My guess is it is not poor motor management. In order to allow for full power, the car must switch from parallel mode to serial mode. This involves opening the clutch between ICE and front axle. I assume this requires temporarily cutting power to prevent the ICE from spinning out of control. Although we are only talking about opening and not closing it, probably better for the clutch also.

Maybe we should compare it to a kick down in a car with a conventional automatic gear box.

It might be worth while trying to engage 4WD mode a second or so before slamming the throttle and see what happens :idea:

 

[Harald]

Hi Anko,

I think it was below 40 MPH but you might be right that a conventional automatic gear box is not better.
I just drove such cars so rarely, that I can't remember these details so well.
(But I still remember very clearly, that the Tesla I borrowed for a day did not delay acceleration .)

Anyway, the Outlander is for sure not bad and I can get used to this behaviour, if needed.
I will also try switching to 4WD and check if this can be a workaround for such cases.

Best regards, Harald

 

[anko]

Please do let us know your findings. Another thing to try might be selecting normal mode instead of ECO mode (in case you had that selected) as this remaps the throttle.

 

[greendwarf]

Can't say I've ever noted a lag in actual acceleration and have assumed that the initial power demand is met by the battery, whilst the ICE gets its act together.

 

[anko]

Can't say I've ever noted a lag in actual acceleration and have assumed that the initial power demand is met by the battery, whilst the ICE gets its act together.

Max output of the battery is 60 kW. At max torque, this much power is consumed by the E-motors at 18 MPH. When you go any faster, torque will be reduced or assistance of the ICE / generator is required.

At double the speed combined output of the battery and ICE / generator (the full 120 kW) can be consumed. Increasing speed above that will automatically result in reduced torque, at constant power output. Until you go over 75 and a bit MPH and parallel mode kicks in again. Than the combined power of the ICE driving the wheels directly and the battery exceeds 120 kW.

All of this ignores losses.

 

[Harald]

I am sure a part of this topic has a technical background, another part will be human perception and expectations.

As the ICE needs to bring up the RPM to 4500 for delivering max. power to the generator, a part of the delay must be caused by this need:

a)
When kicking down the pedal, the ICE could start to deliver some power to the generator immediately. But if it would do so, this would be on low RPM and delivered power would be relatively low.

b)
On the other hand, if the ICE tries to bring up RPMs for being able to deliver max. power asap, it cannot deliver power to the generator for a short moment.
How long does it take to accelerate a 89 kW engine from 1500 RPM to 4500?

I guess this might already be the biggest part of the answer?
Following this argument, there is probably no big chance for amelioration as this aspect is bound to bare physics.

 

[greendwarf]

Can't say I've ever noted a lag in actual acceleration and have assumed that the initial power demand is met by the battery, whilst the ICE gets its act together.

Max output of the battery is 60 kW. At max torque, this much power is consumed by the E-motors at 18 MPH. When you go any faster, torque will be reduced or assistance of the ICE / generator is required.

But surely "torque" and "speed" are not the same. When cruising, even above 18mph, you will not be using the max output nor when waiting at the lights, so that initial demand for extra power can be met from battery e.g. pulling out to overtake. Of course, if you are already accelerating, say up hill and then "floor it" the battery probably won't be able to help - but what about if you are already using the ICE and still have battery available?

 

[anko]

The discussion start to be about "delay in power build-up when overtaking", so I guess one would be going faster than 18 MPH.

But still, when going 18 MPH or above, you need more than the 60 kW available from the battery to get the full acceleration the E-motors can provide. You will have a stronger acceleration after the ICE has kicked in.

Wrt torque versus speed:

The E-motors have maximum torque rating as well as a maximum power rating. The battery has a maximum power rating. At 18 MPH the maximum power rating of the battery is reach, provided you ask for maximum torque. At 36 MPH, the maximum power rating of the E-motors has been reached, again provided you ask for maximum torque and the ICE is playing along. Above 36 MPH torque must go down, because otherwise max power rating of the E-motors would be exceeded.

When you are already using the ICE, first power output of the ICE will be increased to 100%. When that is not enough to meet demand, the battery will step in. When that is still not enough, the ICE will switch to serial mode. When you really kick it down, I believe the ICE will go directly to serial mode.

 

[anko]

Following this argument, there is probably no big chance for amelioration as this aspect is bound to bare physics.

I think you are right.

Being pedantic again , in serial mode the ICE will operate at max 4100 RPM, not 4500. 4100 RPM at full load will produce 70 kW, the max input for the generator. From this input, 60 kW E-output results. The other 10 kW is lost in the generator.

 

[Harald]

Hi Anko,
thank's for your input incl. the "pedantic" correction.

Hi All,
why making things so difficult in looking on kW power at a certain speed?
I think the max. current from the battery is limited. Limit should be in a range of 200 A?
This gives max. available torque via 1 or 2 motor(s).
If higher torque is needed, more current has to come from the generator.

Best regards, Harald

 

[anko]

I think the max. current from the battery is limited. Limit should be in a range of 200 A?

True.

This gives max. available torque via 1 or 2 motor(s).
If higher torque is needed, more current has to come from the generator.

Not exactly true, IMHO. As it does depend on speed.

Max output of the battery is in A. Given that the electricity coming out of the battery has a certain (slightly fluctuating) voltage, it also means max output can be expressed in kW. Consequently, max output from the E-motors in EV mode is also expressed in kW. Torque only comes to play, when speed (or E-motor RPM) is considered.