Acceleration time (2 seconds less?)

[Pancake]

Hi all,

As a registered reader, I am new to this forum. However, I have been reading quite some topics since I ordered an Outlander Phev "Instyle" recently in the Netherlands. It is expected to arrive in the beginning of December. Also I heard that it is being shipped right now. Let's hope the ship doesn't sink (again!). :lol:

The specs of the car claim it will do 0 - 100 (km/hr) / 0 - 60 (mph) in 11 seconds. People claim it "feels" faster and there are also YouTube clips in which acceleration to 100 / 60 takes about 10 seconds. Now, Mitsubishi claims to have improved acceleration to 25 mph with 2 (!) seconds. If so, would it not be logical that acceleration to 60 mph is also improved? Is it?

 

[jaapv]

I'm not quite sure that the acceleration has improved that much, as AFAIK the power of the electric motors and the reduction gear is still the same. However, previous specs were very conservative, maybe Marketing prevailed.

 

[anko]

Could be marketing indeed. Shaving of 2 seconds from the first 0 - 25 MPH would be HUGE.

 

[ian4x4]

The Autocar Road Test of the Outlander PHEV in April 2014 gave the following figures.

0-30 4.0 secs
0-40 5.4 secs
0-50 7.4 secs
0-60 10.0 secs
0-70 13.5 secs
0-80 18.0 secs
0-90 23.7 secs
0-100 30.5 secs

Compared with 'say' a LR Freelander SD4, it was a couple of seconds slower to 60, but made up the loss by 100mph.

Which led me to believe that its in-gear acceleration was more than adequate, even if it was slow off the mark.

Surely all that is needed to make it quicker off the mark is to allow more current initially into the motors by beefing up the wiring and the motors a bit. I doubt if it ever gave full power at zero mph, let alone maximum current.

 

[Ozukus]

This was from one of my previous posts, it sort of applies to this thread, so thought I'd share again.

"Slightly off topic here as it actually relates to a Tesla, and not a PHEV, however is relative to speed, and thought a few would be interested in the information.
Was in Brighton on the weekend only to find the Brighton Speed Trials were running and there was a Tesla entered.
For the non-professional drivers class the Tesla came 31st achieving 106.5mph in 12.15 seconds over the quarter mile.
The key thing though was that there was a timing for 64 feet, assume it's the distance to achieve maximum tranction.
The Tesla did this in 1.92 seconds, and was only beaten by a worked Ford Sierra Cosworth XR 4x4 at 1.89. Even the fastest car on the day could only achieve this distance in 2.0 seconds.
Just shows the torque advantage of an electric engine."

 

[anko]

Compared with 'say' a LR Freelander SD4, it was a couple of seconds slower to 60, but made up the loss by 100mph.

The Outlander was slower at lower speeds and faster at higher speeds? That does not sound very logical.

The Tesla did this in 1.92 seconds, and was only beaten by a worked Ford Sierra Cosworth XR 4x4 at 1.89. Even the fastest car on the day could only achieve this distance in 2.0 seconds.
Just shows the torque advantage of an electric engine."

That sounds way more logical.

BTW: The E-motors of my PHEV seems to give maximum torque directly at 0 km/h.

 

[ian4x4]

Anko wrote
The Outlander was slower at lower speeds and faster at higher speeds? That does not sound very logical.

I can only find Autocar's SD4 Evoque figures at the moment (same engine 190bhp, about same weight)

0-60 8.4 secs
0-100 30.8 secs

True if not logical.

Don't forget that all cars performance figures are heavily modified by the software of the 'drive by wire' control system.
This is to give better reliance of components, mpg, etc. Car makers offer guarantees and try not to pay out on failing components.

If you don't believe me, ask VW how much you need to control the engines performance.

Also as an extra to this subject, I am beginning to worry that some second-hand PHEV (and indeed many other second hand cars could be carrying illegally modified software, or software not correctly patched to latest version)

 

[ian4x4]

Autocar acceleration in kickdown for Outlander PHEV April 2014

20 - 40 mph 2.8 secs
30 - 50 mph 3.5 secs
40 - 60 mph 4.6 secs
50 - 70 mph 6.2 secs
60 - 80 mph 8.1 secs
70 - 90 mph 10.2 secs
80 - 100 mph 12.4 secs

Which look uniform and quite respectable to me for a large SUV.

 

[simonrh]

Using my fully calibrated arse dynamometer, mine is acceptably brisk at low speeds but really does get surprisingly quick once you get to 60+MPH which backs up those stats.
On close roads it is comic the way it runs into its speed limiter too as it is still pulling well when it happens.

 

[ian4x4]

Using my fully calibrated arse dynamometer, mine is acceptably brisk at low speeds but really does get surprisingly quick once you get to 60+MPH which backs up those stats.
On close roads it is comic the way it runs into its speed limiter too as it is still pulling well when it happens.

You are quite right about the top speed limiter (at 106mph). A similarly powered/sized Freelander runs on to about 118mph.

 

[Fragge]

The "old" Outlander PHEV is a bit slow if the line due to the fact that the power is limited by the software. My guess is that this has been done to spare the drivetrain.

On the 2016 model the software has been changed so that the PHEV is faster off the line with more power available. This is due to many complaints about slow start of the earlier generation.

So that's why they claim faster acceleration on the 2016 model.

 

[anko]

Where does this info come from? I mean, if they did it to spare the drive train, then would they really change their mind because of a few complaints? Further more, if I am not mistaken, it is torque that hurts a drive train, not power.

Outgoing power (kW) for a motor is defined as torque (Nm) * RPM / 9548.8. That means at speed = 0, outgoing power of both motors is 0. All you have is lots of torque. I have monitored max torque generated by both motors at 0 km/h with bot the gas and the brake pedal floored and it was equal to the max torque of the E-motors, as specified by Mitsubishi.

I would think they cannot crank up the low speed power of he E-motors without cranking up max torque of the E-motors and the specs of the motors are the same over the different MYs.

Ian's table by Autocar shows 4.0 seconds for 0 - 30. That means 0 - 25 was at least 1/6 th less than 4 seconds, so somewhere between 3 and 3.5 seconds. How are you EVER gonna take off two seconds from that? That would make it more than twice as fast. I have a very hard time believing that.

 

[jaapv]

I think the explanation is in the way the acceleration is measured. If you floor the accelerator with the ICE running the car is fast off the mark. However, if the ICE is off, it will have to start up to deliver full power, making the car feel sluggish. I think they just changed the method.

 

[ian4x4]

I agree with Anko, I cannot understand the quote of 2 secs off 0 - 25mph, but 0 - 60 remains the same as before. (where did all that extra speed/time go)

If I had the job, as I said before, I would beef up the wiring and components a bit, then tinker with the software and feel of the controls so it was a bit faster -- but felt a lot faster.

Perception is everything, and we mere mortals are easily fooled.

Do we have a Professional Race Engineer on the forum, they perhaps could tell us a trick or two used to get their driver to go faster, by juggling the Driver/Car interface.

 

[Neverfuel]

As Anko says, the motors and engine are the same as are the tyre sizes.

But it might be possible if the primary and secondary reduction gears have been altered in the new model. This would give a faster acceleration and / or a higher top end speed.

In the old model we know certain facts:

1. The maximum RPM of the engine is 4,840.
2. The maximum RPM of the front motor is 14,000
3. The maximum RPM of the rear motor is 10,000
4. The maximum RPM of the generator is 14,000
5. The final reduction gearing for the front motor is 9.663 (2.55 X 3.789)
6. The final reduction gearing for the rear motor is 7.065 (1.956 X 3.611)
7. The final reduction gearing between engine and front transaxle is 3.425 (0.903 X 3.789)
8. The final reduction gearing between the engine and generator is 2.736
9. The speed is limited to 106mph
10. The tyre size is 225/55/R18

If we work out the diameter of the tyre we can work out its circumference. This will tell us the RPM of the transaxles:

(Diameter of the rim 225mm X Aspect ratio 0.55) X 2) = 247.5mm (Convert to inches / 25.4) = 9.74 inches add the radius of the tyre +18 = 27.74 inches diameter.

Convert this to a circumference:

27.74 inches diameter X PI (3.142) = 87.17 inches / 12 (convert to feet) = 7.26 feet.

So the car travels 7.26 feet for every revolution of the wheel.

As the car is limited to 106mph we can now work out the maximum RPM of the wheels and therefore of both transaxles:

106 (MPH) X 5280 (Feet per mile) / 60 (seconds in a minute) = 9328 feet travelled.

If we divide the feet per minute by the distance travelled in 1 revolution of the wheel we get the maximum RPM of the wheels (transaxles):

9328 / 7.26 = 1285 RPM (at the wheels).

Therefore:

Front motor RPM at max speed = 1285 X 7.065 (rear motor reduction gear) = 9071 RPM, 928 RPM below its limit of 10,000 RPM.

Rear motor RPM at max speed = 1285 X 9.663 (front motor reduction gear) = 12,417 RPM, 1583 RPM below its limit of 14,000 RPM.

Engine RPM at max speed = 1285 X 3.425 (Engine to differential reduction gear) = 4,401 RPM, 439 RPM below its limit of 4,840 RPM.

Generator RPM at engine RPM of 4,401 = 4401 X 2.736 (engine to generator reduction gear) = 12,041, 1,958 RPM below its limit of 14,000.

If we now used the upper limits of the engine, front & rear motors, and the generator, what would be possible?

Front motor RPM limit 14000 / 9.663 (front motor reduction gear) = 1448.83 RPM at the wheels. 1448.83 X 7.26 (distance travelled in one revolution) = 10,518 feet travelled. 10,518 feet X 60 (seconds in a minute) / 5280 (feet in a mile) = 119.52 MPH. So, to operate the front motor at its limit of 14,000 RPM the car would have to travel at 119.52 MPH.

Rear motor RPM limit 10000 / 7.065 (rear motor reduction gear) = 1415.42 RPM at the wheels. 1415.42 X 7.26 (distance travelled in one revolution) = 10,276 feet travelled. 10,276 feet X 60 (seconds in a minute) / 5280 (feet in a mile) = 116.77 MPH. So, to operate the rear motor at its limit of 10,000 RPM the car would have to travel at 116.77 MPH.

Engine RPM limit 4840 / 3.425 (engine to differential reduction gear) = 1413.14 RPM at the wheels. 1413.14 X 7.26 (distance travelled in one revolution) = 10,259 feet travelled. 10,259 feet X 60 (seconds in a minute) / 5280 (feet in a mile) = 116.57 MPH. So, to operate the engine at its limit of 4,840 RPM the car would have to travel at 116.57 MPH.

As the car is always driven by its engine at top speed, we can conclude that the front and rear motors will always be operating within their limits even if the car were to operate at the maximum engine RPM of 4,840. The generator would be disconnected anyway, but what if it wasn’t?

At 4,840 RPM of the engine the car would be running 2.736 times faster due to the engine to generator reduction gear. 4840 X 2.736 = 13,242 RPM, 758 RPM below its limit of 14,000.

Okay, what did that prove?

Well, if the new car has got different primary or secondary reduction gears, from the ones we have, the balance of acceleration, top end speed or both could be changed quite significantly - without having to make changes in the specs of the engine, front or rear motors or the generator. As all we have to go on at the moment are the published specs of the new model, but have got more detailed information on our model - we can only wait and see.

Maths lesson over, I’m off for a cuppa.

 

[anko]

Ah, you mean 2 seconds less compared to the Autocar number + 2 seconds?

 

[anko]

Nice Neverfuel, been there, done that ....

https://www.dropbox.com/s/g7izvwx8nhfoneg/PHEV%20Max%20torque%20at%20speed.xls?dl=0

 

[Ozukus]

You need to adjust your calcs as a 225/55/R18 tyre has a circumference of very slightly over 7.6 feet.

Cheers

 

[Grigou]

But it might be possible if the primary and secondary reduction gears have been altered in the new model. This would give a faster acceleration and / or a higher top end speed.

No they don't. Same specs

 

[ian4x4]

I am extremely impressed by the calculations, it takes me back to my schooldays.
Unfortunately it gets even more complicated these days, as these basic figures are modified by the control programming/electronics
which did not exist in those analogue days. I just had to learn the maths which controlled all the allowable parameters (including the maximum rates of change)

The brochure says the power and 0-60 stays the same, most commentators say the step-off improvement is system led.

I am determined to keep things simple, so please can someone answer the question below, or

I agree with Anko, I cannot understand the quote of 2 secs off 0 - 25mph, but 0 - 60 remains the same as before. (where did all that extra speed/time go?)