[OrmondBMW]

I noticed when we go into reverse, the gas engine shuts off and we run electric only. Does that mean BMW removed reverse rations from the gear or it's simply locked out? In other words, does the gas engine ever move the car in reverse?

I can't help thinking of random crap like this!

[rastaman777]

Originally Posted by OrmondBMW

I noticed when we go into reverse, the gas engine shuts off and we run electric only. Does that mean BMW removed reverse rations from the gear or it's simply locked out? In other words, does the gas engine ever move the car in reverse?

I can't help thinking of random crap like this!

I've never heard the gas engine on when in reverse.

[Maxxsirrah]

Yep, I've had it

[rastaman777]

Originally Posted by Maxxsirrah

Yep, I've had it

Makes sense that it should use the engine in some situations, when there's no juice left at all in the battery.

Make me want to go for a short cruise - in reverse - to test it out!

[Coastali8]

When I get in the car after it has been sitting for a couple of weeks the ICE fires up immediately when I press the drive readiness button. I then back the car out of the garage with the ICE running. But I don’t believe the ICE is moving the car but instead just supplying electric power to the electric motor. The rest of the time when I put the car in reverse the ICE shuts down. So by deduction I assume that the electric motor is the only drive with a reverse gear. Probably the electric motor just runs in reverse. That would be the simplest solution and there really is no reverse “gear” in the car.

[OrmondBMW]

Originally Posted by Coastal i8

When I get in the car after it has been sitting for a couple of weeks the ICE fires up immediately when I press the drive readiness button. I then back the car out of the garage with the ICE running. But I don’t believe the ICE is moving the car but instead just supplying electric power to the electric motor. The rest of the time when I put the car in reverse the ICE shuts down. So by deduction I assume that the electric motor is the only drive with a reverse gear. Probably the electric motor just runs in reverse. That would be the simplest solution and there really is no reverse “gear” in the car.

This makes perfect sense.

So makes me wonder, are they using a stock BMW gearbox for our cars or one specifically built for them?

[Jo-Sta07]

There is no reverse gear. Reverse is all electric.

[Coastali8]

Originally Posted by OrmondBMW

This makes perfect sense.

So makes me wonder, are they using a stock BMW gearbox for our cars or one specifically built for them?

Well...a stock gearbox would have a reverse gear. So “ no “ would probably be the answer.

[Aye-eight]

When I first read OP’s question, my first reaction was “duh!”. But thinking about it, it makes perfect sense from a weight reduction perspective to do away with reverse on the ICE gearbox. If it makes as much sense from a development cost perspective, I don’t know.

I’d think it’s easy to test: Get into your car in your garage, windows down, put it into “D”, switch to Sport mode (as that’s supposed to guarantee action on the rear axle), shift into “R”. If you hear a clonk from the gearbox, chances are there is a reverse gear. The e-motor wouldn’t need a “clonk”, as it would just spin the other way. No “clonk”, no reverse. Just a thought ...

[NGR]

No reverse on the ICE transmission - either a weight saving or a space-related issue.

The only time you'll hear the ICE running when in reverse is if you've just started for the first time in a while and possibly if you've been thrashing it and the engine wants to keep circulating coolant - I haven't seen that happen but expect it would. Time for a drive to test it out!

[stressdoc]

So it might be difficult to get traction in snow in reverse?

[OrmondBMW]

Originally Posted by stressdoc

So it might be difficult to get traction in snow in reverse?

Wow, that’s an equally obscrure and awesome thought :-)

Didn’t think of it living in FL.

[Maxxsirrah]

Originally Posted by NGR

No reverse on the ICE transmission - either a weight saving or a space-related issue.

The only time you'll hear the ICE running when in reverse is if you've just started for the first time in a while and possibly if you've been thrashing it and the engine wants to keep circulating coolant - I haven't seen that happen but expect it would. Time for a drive to test it out!

I've definitely had the ICE running on occasion when in reverse, whether its doing anything or not I couldn't say. Usually happens when I get home and the battery is flat and the ICE has come on as I start to reverse into the garage.

[NGR]

Originally Posted by Maxxsirrah

I've definitely had the ICE running on occasion when in reverse, whether its doing anything or not I couldn't say. Usually happens when I get home and the battery is flat and the ICE has come on as I start to reverse into the garage.

In this case, I suspect the ICE is running to keep the battery topped-up and not actually moving the car. Similar to when you're in sport mode and stationary, the engine is acting like range extender to charge the battery.

Having said that, I checked the i8 technician overview document and it says that the Aisin 6 speed auto has got a reverse gear!

[Coastali8]

Originally Posted by NGR

In this case, I suspect the ICE is running to keep the battery topped-up and not actually moving the car. Similar to when you're in sport mode and stationary, the engine is acting like range extender to charge the battery.

Having said that, I checked the i8 technician overview document and it says that the Aisin 6 speed auto has got a reverse gear!

So...
Having said that, as you say.
How do you get the ICE to run while your in reverse except when the car senses “on its own” it needs electrical power? It can’t be done with any driver selected mode. The ICE always shuts down when the high voltage battery is charged and you place the shift selector in reverse.

[NGR]

Originally Posted by Coastal i8

So...
Having said that, as you say.
How do you get the ICE to run while your in reverse except when the car senses “on its own” it needs electrical power? It can’t be done with any driver selected mode. The ICE always shuts down when the high voltage battery is charged and you place the shift selector in reverse.

I don't think you do. I'm sure the technicians can plug something in to fire up the ICE at will but not the driver.
There's no need for the ICE to be running in reverse unless it's keeping itself cool/charging the battery/warming up after being parked for a prolonged period.

[Coastali8]

Originally Posted by NGR

I don't think you do. I'm sure the technicians can plug something in to fire up the ICE at will but not the driver.
There's no need for the ICE to be running in reverse unless it's keeping itself cool/charging the battery/warming up after being parked for a prolonged period.

That is what I’m trying to say.
I’m disputing the claim that the ICE transmission has a reverse gear.

[NGR]

Originally Posted by Coastal i8

That is what I’m trying to say.
I’m disputing the claim that the ICE transmission has a reverse gear.

I hear you, and I don't believe it has a reverse either or at least it isn't used. However, the BMW technical training manual for the I12 states:

"In
the
I12
the
GA6F21AW
automatic
transmission
is
used
for
the
first
time
in
a
BMW
vehicle.
This
automatic
transmission
transmits
up
to
320*Nm
/
258
lb
ft
and
was
especially
adapted
for
use
in
t he
I12.
It
has
six
forward
gears
and
a
reverse
gear."

It even gives the ratios (including reverse):

"3.3.
Ratios
GA6F21AW
1st
gear 4.459
2nd
gear 2.508
3rd
gear 1.556
4th
gear 1.142
5th
gear 0.851
6th
gear 0.672
Reverse
gear 3.185
Final
drive
ratio 3.683"


Download a copy here - very interesting read if you like nerdy stuff

http://www.rotory.com/bmw/I8.pdf

[Coastali8]

Wow,
That is some great information. THANK YOU!
I have never been able to find much info on the systems of the i8. The pdf you gave me answers a lot of my questions. It’s great reading for any i8 owner.

I agree with you about the info stating that the transmission coupled to the ICE has a reverse gear. They even list the ratio. Do I understand it? No. Do I believe it? Really hard. How can the car move in reverse when the ICE is shut down??? If the only reverse is in the 6 speed gearbox connected to the ICE and not in the 2 speed gear box connected to the electric motor??? There is no physical connection between the two drive systems. Now I’m really confused.
Maybe it’s hamsters on a rotating wheel and I better figure out how to feed them or I’ll never be able to back out of my garage again!

Also after reading through the pdf. I’m even more scared of all the electronics in the car. The complexity is nearly overwhelming!

[NGR]

Originally Posted by Coastal i8

Wow,
That is some great information. THANK YOU!
I have never been able to find much info on the systems of the i8. The pdf you gave me answers a lot of my questions. It’s great reading for any i8 owner.

I agree with you about the info stating that the transmission coupled to the ICE has a reverse gear. They even list the ratio. Do I understand it? No. Do I believe it? Really hard. How can the car move in reverse when the ICE is shut down??? If the only reverse is in the 6 speed gearbox connected to the ICE and not in the 2 speed gear box connected to the electric motor??? There is no physical connection between the two drive systems. Now I’m really confused.
Maybe it’s hamsters on a rotating wheel and I better figure out how to feed them or I’ll never be able to back out of my garage again!

Also after reading through the pdf. I’m even more scared of all the electronics in the car. The complexity is nearly overwhelming!

yep - it's a complicated beast, all sorts of things needed that you don't have in a normal car such as an electric trans fluid pump, auxiliary coolant for the turbo and engine bay etc...

re the reverse gear, I would expect it to be the front eMotor doing the work, simply reversed polarity - I assume that would be simplest way of achieving reverse.
However, is it possible that the auto trans does have a reverse gear and the small eMotor attached to the ICE actually powers the car backwards that way? No idea, need someone to get an i8 onto some ice and find out!

[JasH]

Originally Posted by NGR

need someone to get an i8 onto some ice and find out!

Done it. (Me doing a J Turn on ice.)

It does have a reverse gear, and it is used

[NGR]

Originally Posted by JasH

Done it. (Me doing a J Turn on ice.)

It does have a reverse gear, and it is used

Nice turn

Was your ICE running at the time?