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      08-09-2020, 06:09 AM   #1
MolarBear
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When exactly does the electric motor work?

In comfort mode, the ICE activates above 55mph i.e. at motorway speeds.

When the ICE is on, does the electric motor still actually work if just cruising?

I've read the comprehensive technical document on it, which is great, and it says you get electric assist with 1) low rev range/torque fill and 2) e-boost/kickdown.

But if you've got a full charge, going at 70mph, and the ICE is chugging along on cruise control so a steady load at medium rev range, will the front electric motor actually still contribute to a % of that 70mph, or is it entirely ICE in that situation? What is the power distribution?
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      08-09-2020, 12:16 PM   #2
Mr Squarekins
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In comfort, at 70 it's nice only I think. Why not bring up the energy flow view on the idrive monitor to watch what happens.

I only recently released how the car 'plans' recharging opportunities when the sat nav is on. It actually says 'planned' when you are heading towards a steep decline.
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      08-09-2020, 03:44 PM   #3
Leto1701
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This is a complex topic. It is different for the old and new models, every driving mode, specific configuration of minimum charge, etc. You can put the pictogram that shows you exactly which motor works in which role to the split screen permanently.

A hefty throttle input will engage the ICE in all but the pure EV modes and sports where it is always engaged. Your dash shows the transition power limits for ICE engagement. In sports if you manually lock a gear and floor it, the eBoost gives you everything but a 1,5l 3 cyl. feeling, even at 1800 rpm in 6th gear. My favorite Autobahn cruise mode at 160 kph. Charges the battery to 75% in a couple minutes too.

ICE engines are very inefficient at partial load, around 10%. The i8 will use more power from the ICE than required to maintain current speed to charge the battery if you tell it to, or simply disengage the electric motor in other setups. Sounds complicated but is transparent to the user. Some drive train strategies require the user to provoke them, like Sports 6th gear cruising with eBoost, because in automatic mode, Sports only shifts up to 5th.
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      08-11-2020, 02:41 AM   #4
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Quote:
Originally Posted by Leto1701 View Post
This is a complex topic. It is different for the old and new models, every driving mode, specific configuration of minimum charge, etc. You can put the pictogram that shows you exactly which motor works in which role to the split screen permanently.

A hefty throttle input will engage the ICE in all but the pure EV modes and sports where it is always engaged. Your dash shows the transition power limits for ICE engagement. In sports if you manually lock a gear and floor it, the eBoost gives you everything but a 1,5l 3 cyl. feeling, even at 1800 rpm in 6th gear. My favorite Autobahn cruise mode at 160 kph. Charges the battery to 75% in a couple minutes too.

ICE engines are very inefficient at partial load, around 10%. The i8 will use more power from the ICE than required to maintain current speed to charge the battery if you tell it to, or simply disengage the electric motor in other setups. Sounds complicated but is transparent to the user. Some drive train strategies require the user to provoke them, like Sports 6th gear cruising with eBoost, because in automatic mode, Sports only shifts up to 5th.
Interesting that it will not take 6th in sports. I manually change up but then you have to go from sports to comfort to get back to automatic mode. Quirky to say the least.
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      08-11-2020, 04:01 PM   #5
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Quote:
Originally Posted by Pheath217 View Post
Interesting that it will not take 6th in sports. I manually change up but then you have to go from sports to comfort to get back to automatic mode. Quirky to say the least.
Just hold down the right paddle for about 2 seconds and it'll revert.
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      08-11-2020, 04:07 PM   #6
MolarBear
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So I've been doing a lot of watching of the energy distribution screen during motorway journeys and have come to the following conclusions:
1. That at a constant speed of 70mph (British motorway speed) only the ICE will work and gives about 40mpg.
2. If you pop it into sport, charging at the same time gives about 22mph so roughly half.
3. Electric operates until 55mph when the ICE kicks in, then after this a lot of the time accelerating will have an electrical assist even if just accelerating slowly - it doesn't need to be in kickdown to get e-boost. I suspect that the electric motor just helps keep the ICE at a constant RPM and it just helps the economy that way but doing a lot of the acceleration - this is shown in the energy transfer screen as electric assist or something to that effect. However once it is cruising it appears to be strictly ICE. The battery does not get used.
4. The electrical range seems to only indicate range until 10% charge - perhaps it keeps this for e-boost performance as a minimum? If you're near home then you can add about 3 miles to the range remaining (for LCI at least) if you're going to charge it when you get back and don't need the boost for a later drive.
5. Just a quick guess here, and I need to monitor more extensively but:
At 30 mph it takes about 2-3% per mile on the power.
50 mph its about 3-4% a mile
70mph it will chew through at 5-6% per mile.
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      08-11-2020, 04:49 PM   #7
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Quote:
Originally Posted by MolarBear View Post
So I've been doing a lot of watching of the energy distribution screen during motorway journeys and have come to the following conclusions:
1. That at a constant speed of 70mph (British motorway speed) only the ICE will work and gives about 40mpg.
2. If you pop it into sport, charging at the same time gives about 22mph so roughly half.
3. Electric operates until 55mph when the ICE kicks in, then after this a lot of the time accelerating will have an electrical assist even if just accelerating slowly - it doesn't need to be in kickdown to get e-boost. I suspect that the electric motor just helps keep the ICE at a constant RPM and it just helps the economy that way but doing a lot of the acceleration - this is shown in the energy transfer screen as electric assist or something to that effect. However once it is cruising it appears to be strictly ICE. The battery does not get used.
4. The electrical range seems to only indicate range until 10% charge - perhaps it keeps this for e-boost performance as a minimum? If you're near home then you can add about 3 miles to the range remaining (for LCI at least) if you're going to charge it when you get back and don't need the boost for a later drive.
5. Just a quick guess here, and I need to monitor more extensively but:
At 30 mph it takes about 2-3% per mile on the power.
50 mph its about 3-4% a mile
70mph it will chew through at 5-6% per mile.
You should add that's the old, small battery i8, correct?
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      08-12-2020, 02:23 AM   #8
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Quote:
Originally Posted by Leto1701 View Post
You should add that's the old, small battery i8, correct?
No, it's the larger battery/LCI - 9.3kw usable.
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      08-12-2020, 02:30 PM   #9
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Quote:
Originally Posted by MolarBear View Post
No, it's the larger battery/LCI - 9.3kw usable.
Odd. 5% at 112kph per mile would mean 20 miles only at that speed or less at 6%. So in real units that's 32km of range or less. I go 3x a week 45km at 120kph on a charge with some to spare. That's why I thought you referred to the old one. EV mode, EcoPro, roof down, aircon obviously off.

There are a lot of parameters required to get to comparable numbers here...

Last edited by Leto1701; 08-13-2020 at 02:16 AM..
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      08-13-2020, 09:21 AM   #10
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In a lci i8 yesterday on a 46ml 50/50 mixed motorway and A road journey it gave me 31mls in full electric mode and 35mls in comfort mode with the ice fired up. After the Journey I noticed the app was showing a combined consumption mpg of 128.4mpg what’s does this mean, is this good and how is this mpg calculated ?

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      08-14-2020, 01:04 AM   #11
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Quote:
Originally Posted by Leto1701 View Post
Odd. 5% at 112kph per mile would mean 20 miles only at that speed or less at 6%. So in real units that's 32km of range or less. I go 3x a week 45km at 120kph on a charge with some to spare. That's why I thought you referred to the old one. EV mode, EcoPro, roof down, aircon obviously off.

There are a lot of parameters required to get to comparable numbers here...
Fully charged it will show up as a 35 mile range with gentle driving, and I'm pretty confident I could get that fully on 50mph roads or less. The 70mph motorway driving sucks the battery from what I can see. If you monitor the battery % on the e-drive page it would be great to see how over 10 miles or so of e-drive what your starting and finishing % is at 70 mph?
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      08-14-2020, 02:17 AM   #12
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Quote:
Originally Posted by MolarBear View Post
Fully charged it will show up as a 35 mile range with gentle driving, and I'm pretty confident I could get that fully on 50mph roads or less. The 70mph motorway driving sucks the battery from what I can see. If you monitor the battery % on the e-drive page it would be great to see how over 10 miles or so of e-drive what your starting and finishing % is at 70 mph?
Not just that. Make the experiment. Get into the fully charged car. Put it in EV only, comfort. Look at the range. Then put it in EcoPro. The range should increase. This is driven by a changed power pedal response (I like it better) and reduced aircon/heating. Now turn the aircon off. Now the range will significantly increase. I drive like that whenever I can put the roof down (hey, it's a convertible) and get around 54km indicated range. Vmax is 120kph in pure electric modes on the new i8. That's my speed on the Autobahn in EV mode. I get to about 45km like that because wind resistance increases with speed square.

So everything you try needs to be while taking down at least:

OAT
Wind speed and direction
Drive mode
Roof position
Aircon setting
Wheel dimensions

The above numbers are for 215/245 stock wheels. In winter I drive 215/215 stock turbine wheels and they have an even better range on a warm day with aircon off and roof down... and so on.

B.t.w., the App only indicates the EV comfort range because it doesn't know which mode you choose. If you just press the eDrive button that's the mode you will be in, comfort mode with full aircon/heating.

Last edited by Leto1701; 08-14-2020 at 02:22 AM..
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      08-15-2020, 11:26 AM   #13
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A few more observations which I found interesting on how it appears the drive modes work (I have a long motorway commute at 70mph so it gave me something to play with whilst on cruise control):

Sport - battery < 71.5% - Engine powers both the car and charges the battery - manual change to 6th gear. Consumption - 20mpg. Charges at the rate of 1% every 0.5 miles so 2% a minute at 70mph.

Sport - battery stops charging at 71.5%. Consumption goes to 39-40mpg. Clearly the small starter motor has stopped the dyno / charging which appears to take 20mpg off the consumption just to charge.

Comfort - cruise control. Consumption goes to 48-49mpg. Power distribution shows petrol engine only and does not show any battery / electric motor contribution. Despite the display showing no electrical motor use, the battery still depletes at a rate of around 1% every 3-4 miles (I think). Clearly in comfort mode there is a little electrical contribution (perhaps it just helps with any loads to help the petrol engine maintain the speed). However these small amount of battery power seems to stretch consumption by another 8-9mpg. I'm not sure what the difference is between sport mode in 6th gear and comfort mode (which presumably also sticks in 6th gear) apart from a minimal battery charge (which seems to only be consuming 0.25% a mile or so). Clearly something is eating up 9mpg in the modes and surely it can't just be the minimal amount to maintain the battery?

None of this is relevant at all for when doing anything fun or spirited of course, just interesting for me to see as a new owner what exactly is going on underneath the hood and how the drive train works !
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      08-15-2020, 03:32 PM   #14
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Interesting. I get 39mpg in odd units (6L/100k) WHILE charging in Sports 6th gear at 160kph (100 mph in odd units) over a distance. I assume the instant fuel consumption is higher but double and more? Need to do some experiments where the sweet spot is but in any case it is impressive to be able to go at 100mph whenever possible from Frankfurt Munich and only use about 3/4 of the fuel. My Model S at that speed needed two charging stops...
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      08-20-2020, 03:05 AM   #15
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Quote:
Originally Posted by MolarBear View Post
Just hold down the right paddle for about 2 seconds and it'll revert.
Ah great info, thank you
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