04-03-2018, 05:13 PM | #1 |
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Vehicle hesitation on acceleration
I think I've seen something on here before about i8 momentary hesitation on acceleration from a stop. I've experienced it a couple of times and know another coworker that had it with his i8 also.
Anyone know and service bulletins or action taken by dealers? I had a forward update a while back that they said would address it. It didn't. Just having it serviced right know and they're doing/done another update today. I'm in SoCal... anyone else had this issue ? |
04-04-2018, 08:34 AM | #2 |
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Are you in sport mode when this happens? If so, you’re probably just experiencing turbo lag. EV modes should never hesitate on acceleration and don’t from my experience.
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04-04-2018, 10:41 AM | #3 |
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@vance My car does the opposite. When I'm in electric or efficient mode, once in a while it will hestitate, it barely crawls for a couple seconds, then takes off. If I keep it in sport i don't have this problem. I'm usually in sport mode so it's not a big deal for me.
Last edited by emmfive; 04-04-2018 at 05:17 PM.. |
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04-04-2018, 01:54 PM | #4 | |
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I'm talking about pulling out into traffic from a stop and the car dying for half a second before accelerating away. I know 2 other friends with an i8 who have experienced this also. |
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04-04-2018, 02:00 PM | #5 |
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It's just about the car engaging gear, trying to understand What you want it to do, pretty common in automatic cars, I've had it on others too. Don't get it in sport mode to be fair, the car knows what you want when you accelerate!
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04-04-2018, 02:07 PM | #6 |
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I started driving around using launch control. No lag but jeez my gas mileage is pretty bad
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04-04-2018, 07:50 PM | #7 | |
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Turbolag is nonexistent in that engine, BTW.
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04-05-2018, 03:01 AM | #8 | |
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In Comfort it can happen as car might move off in E, but then realise you are demanding "high" throttle, and it has to engage the ICE. It's perfectly normal. Doesn't happen in e-Drive either. |
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04-05-2018, 08:11 AM | #9 | ||
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04-05-2018, 08:12 AM | #10 |
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Never had this in any of my cars except i8
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04-05-2018, 07:35 PM | #11 | |
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04-08-2018, 04:31 AM | #12 |
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When the ICE is still cold and you have electrocomforted yourself up to the junction there is a moment of deep thought, on whether you (really want to) jerk (the poor engine)... . Unfortunately, comfort mode will only electroboost if you slowly press the pedal or go all the way to kickdown, otherwise it will just spool up the noisy initially somewhat lumpy ICE in the back.
Flipping it over to sport will start the ICE and mobilize much more electroboost. If running a short errand with a full battery, e mode is always an option, as it downshifts the front e motor into first gear, essentially doubling torque. ICE will stay hibernating happy and long-term healthy that way. On a wet pavement, not all of that will translate into motion, though... . |
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04-08-2018, 09:27 AM | #13 | |
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a) you experience no lag when in Sport mode i.e. ie using ICE too b) the small electric motor in the rear, fills in the torque gap otherwise caused by turbo lag. It clearly works when in Sport mode. |
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04-11-2018, 09:42 AM | #17 |
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It's a consequence of the drive-train.
Reading the technical manual combined with experience what you experience is not unusual (I'm not saying it's desirable though). When you start in comfort mode, the gas engine is off and initial propulsion is via the electric motor - pulling out of junctions etc... The electric motor has a two-speed gearbox attached to it - a low gear and a high gear. When in comfort mode, the high gear is engaged so when you start off, the motor is pushing through the high gear (imagine starting off in a normal car in 3rd gear). For gentle starts and rolling in traffic, you don't notice but for a quick getaway it is obvious and the car feels like it's bogged down until the gas engine kicks in and helps push you along. When in sport mode, the gas engine is always running so you have all the shove at your disposal to start with - simples. When in full e-drive, the low gear is selected for the e-motor which means speedy take-offs even without the gas engine, everything feels fine - up to a specific speed. Why does the e-motor select 'high' gear when in comfort? Simply so that the e-motor can assist propulsion across a wider range of speeds without changing gear. The 'low' gear is restricted to a low speed range and means the e-motor would stop assisting you at (I think) 60mph. I believe the car would feel much better if comfort mode selected the 'low' gear when at low speeds and swapped to the high gear when you're travelling faster. What I'd like to know is why it doesn't do this? I suspect the box may become a reliability problem if it swaps cogs too often when on the move or it simply can't swap gears very quickly - maybe a design compromise of some sorts that only the boffins at BMW can explain. To find out how long it takes to change gears on the e-motor, find a quiet road and stop in comfort mode, gas engine off. Press the button to engage e-drive (this will ask the motor to swap from high to low gear) at the same time, press the throttle (don't kick down though). You will go nowhere until the e-motor gear has changed and then you'll move off quite nicely - it feels like several seconds to me.
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04-11-2018, 10:57 AM | #18 | |
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04-11-2018, 03:20 PM | #20 |
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Thanks Vance, couldn't remember if it was 60 or 80, just been out in mine and it looks around 80 on the dial 77 it is!
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04-12-2018, 08:48 PM | #21 |
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there is deff a little lag. Its only a split second and much less than my previous f80 but there is some hesitation. Once you get used to the car this actually becomes quite predictable. For example, if i really want some power i will tap the throttle lightly to bring the rpm's up and then floor it, then its instant. The response is not instant from 0 rpms.
the only time i feel a true delay, which is what i think the OP is referring to, is when the ICE kicks on |
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04-15-2018, 02:32 AM | #22 |
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I agree with the assessment of why it does this in comfort. I've noticed it when I got it so now I put it in Sport when I think I might need instant acceleration soon. I don't have a problem with this.
On a highly related note: When in eDrive mode and you punch it hard off the line does anyone else's initially pull off hard but then (assuming there is traction) seems to cut power after a 1.5 seconds or so for 500ms? It's almost like a safety cutoff , very harsh and abrupt. Could anyone else test this? |
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