[baron95]

Originally Posted by M2siast

Why is more weight in the rear better than equal weight across?

Not to derail the thread, but ...

You will see all RWD motorsports series from F1, to Lemans, to club racing, designers and racing teams trying to get as much weight shifted back as possible.

That is also why mid-rear engine (e.g. Cayman, C8 Corvette, Ferrari, McLaren, etc) and rear engine (e.g. 911, Exige, etc) are such good sports cars.

When you accelerate (straight line or out of turns) there is more weight in the rear for traction.

When you brake (straight line or into turns trailbraking) there is more weight in the rear wheels, so the rear brakes can help a bit more vs having nearly all the braking capability shouldered by the front brakes/tires. That sharing of weight/braking makes tires run cooler, tires and brakes last longer, etc.

There is also less weight in the front (steering) wheels. So steering needs less assist, tires can be narrower up front, all that translate into more pleasant, precise, natural steering.

So drive a Cayman GTS an M2 and an RS3 - alll three cars have similar HP Cayman has ~60% on the rear, M2 ~52%, RS3 about 40%.

Porsche has the best steering by far and can get by with skinny front tires. M2 in the middle. RS3 is annoying to drive has wider front tires than rear tires, is twitchy under braking, etc. Brakes and tires on the Cayman will last way longer than M2 on track, because the load is more balanced. The car is much more lively, fun and easier to rotate into turns.





Bringing it back to battery.....that is why BMW put the battery in the back - they are DESPERATELY trying to more as much weight back as they possibly can. But lower weight at the margins still trumps tiny variations in weight distribution - so taking 38lbs out of the car (1%) will still help a bit on track even if it marginally changes weight distribution in the wrong direction by 0.1% or so.



Hope that helped and wasn't too boring. (prob was )

[baron95]

Originally Posted by M2siast

You are making a lot of claims here...
Would you be able to back any of them? I am definitely curious...
Already asked one question, here is another: where do you take Li-Ion is better than AGM in the cold?

Fair point. I do live in New England, and even with global warming it still gets cold here

But as I said - I'm still doing my research on the M2. Don't want to overstate what I can back up. [have edited post as such]

Knowing what I know today - an Antigravity will go in the back of my M2 the second it comes back from the dealer break-in service.

Given how slow my order is progressing that will probably be December - so, I'll be able to provide a cold weather report then

[M2siast]

Originally Posted by baron95

Not to derail the thread, but ...

You will see all RWD motorsports series from F1, to Lemans, to club racing, designers and racing teams trying to get as much weight shifted back as possible.

That is also why mid-rear engine (e.g. Cayman, C8 Corvette, Ferrari, McLaren, etc) and rear engine (e.g. 911, Exige, etc) are such good sports cars.

When you accelerate (straight line or out of turns) there is more weight in the rear for traction.

When you brake (straight line or into turns trailbraking) there is more weight in the rear wheels, so the rear brakes can help a bit more vs having nearly all the braking capability shouldered by the front brakes/tires. That sharing of weight/braking makes tires run cooler, tires and brakes last longer, etc.

There is also less weight in the front (steering) wheels. So steering needs less assist, tires can be narrower up front, all that translate into more pleasant, precise, natural steering.

So drive a Cayman GTS an M2 and an RS3 - alll three cars have similar HP Cayman has ~60% on the rear, M2 ~52%, RS3 about 40%.

Porsche has the best steering by far and can get by with skinny front tires. M2 in the middle. RS3 is annoying to drive has wider front tires than rear tires, is twitchy under braking, etc. Brakes and tires on the Cayman will last way longer than M2 on track, because the load is more balanced. The car is much more lively, fun and easier to rotate into turns.





Bringing it back to battery.....that is why BMW put the battery in the back - they are DESPERATELY trying to more as much weight back as they possibly can. But lower weight at the margins still trumps tiny variations in weight distribution - so taking 38lbs out of the car (1%) will still help a bit on track even if it marginally changes weight distribution in the wrong direction by 0.1% or so.



Hope that helped and wasn't too boring. (prob was )

Originally Posted by baron95

Fair point. I do live in New England, and even with global warming it still gets cold here

But as I said - I'm still doing my research on the M2. Don't want to overstate what I can back up.

Knowing what I know today - an Antigravity will go in the back of my M2 the second it comes back from the dealer break-in service.

Given how slow my order is progressing that will probably be December - so, I'll be able to provide a cold weather report then

Definitely NOT boring and I appreciate the details and thoughts. all make sense… thanks for putting those down for us to have an educated conversation.

About the battery, I thought li-ion was known for suffering more in the cold. Wondering how the stock battery in the F80 and G80 make out in the dead of winter. And how the antigravity compares. (My bias tells me aftermarket is never as good as OE, maybe it is)

I know many people park these cars during winter, but the OE battery was designed to work in the winter, or so I hope.

[GregW / Oregon]

Originally Posted by baron95

My understanding (and I am still doing my research) is that the Antigravity batteries have their own built in battery management system, and they are drop-in on any vehicle with an AGM battery.

They are designed to take charging and hold voltages in-line with AGM batteries.

So, as Jackie Ding did on his G87, drop it in, no coding, save 38lbs.

So why is EAS, a reputable dealer that obviously would like to sell the things, unable to confirm if it is viable?

[baron95]

Originally Posted by GregW / Oregon

So why is EAS, a reputable dealer that obviously would like to sell the things, unable to confirm if it is viable?

I'm assuming because they haven't had a chance to get an M2, put an Antigravity on it and test it yet.

And neither have I - but I have seen enough Antigravity batteries replacing AGM batteries with no change, that having Jackie Ding confirm it works on the G87 with no coding is good enough for me.

Besides, I don't even have my car yet

[baron95]

Originally Posted by M2siast

Definitely NOT boring and I appreciate the details and thoughts. all make sense… thanks for putting those down for us to have an educated conversation.

About the battery, I thought li-ion was known for suffering more in the cold. Wondering how the stock battery in the F80 and G80 make out in the dead of winter. And how the antigravity compares. (My bias tells me aftermarket is never as good as OE, maybe it is)

I know many people park these cars during winter, but the OE battery was designed to work in the winter, or so I hope.

The Antigravity RS series has an operating temperature range of -5°C to 60°C (23°F to 140°F). You have to determine if that is an acceptable range for you. (I did not look up the range for the BMW Li-Ion battery on the G8x, but I am sure it can operate in lower temperatures).

[M2siast]

Originally Posted by baron95

The Antigravity RS series has an operating temperature range of -5°C to 60°C (23°F to 140°F). You have to determine if that is an acceptable range for you. (I did not look up the range for the BMW Li-Ion battery on the G8x, but I am sure it can operate in lower temperatures).

-5 is not enough for Winter in the midwest or Canada...

[baron95]

Originally Posted by M2siast

-5 is not enough for Winter in the midwest or Canada...

Then you run the Antigravity during track season, and OEM AGM during winter.

Or

Once someone confirms it works, you can try to run the G80/82 Li-ION OEM battery.

Or

Just stick with AGM year round.

Cool thing is that we have options to bring the M2's weight substantially lower than the M4's.

[M2PDX]

I have an Antigravity battery, and it was ..... wait for it ..... thirty eight lbs lighter than stock.

My shop coded it, and it's been bulletproof.

Biggest and most cost effective weight savings.

A new one will be installed in my G87, which arrives next week ... saving ... thirty eight lbs. Well worth the investment.

[aerobod]

Originally Posted by M2siast

-5 is not enough for Winter in the midwest or Canada...

Yes, definitely not. If you leave the car outside, pretty well any day of the year could have -5C weather overnight here in Calgary!

AGM battery performance in -40C weather is proven, so may be a good idea not to have a Li-Ion battery fitted for use in colder winter weather if it can't operate down to that temperature.

[ToneM2]

I think an antigravity battery with a swap to lighter forged wheels you can save around 75-80lbs. Pretty significant even on a 3800-3900lb vehicle. That’s my plan at least. I know the G87 hasn’t been out too long but the M3/M4 have been out for a couple years already with a strong aftermarket which is why I said I’m surprised no one has tried this yet. Me living in the northeast and my car stays outside for most of the day I would probably swap in the oem battery during the cold winter months. Seems like an easy swap.

[Squidget]

Battery warmers are also an option.

[baron95]

By the way, if anyone is curious as to what is actually inside the box of the G80/G82 Li-Ion battery, here are some pictures - there is a lot of circuitry....

[aerobod]

Originally Posted by Squidget

Battery warmers are also an option.

Normally a last resort when the temperature is below -40C, as not all public parking spots have electrical plug-ins and if they do they are often on a timer to only give about 50% duty cycle. A good lead acid battery should be fine down to -40C without a warmer.

[tom @ eas]

Just wrapped up our Antigravity DIY here:

Antigravity Drop-in LiFePO4 Lithium Batteries for BMW (Save 40lbs!) - DIY
https://g87.bimmerpost.com/forums/sh...php?p=30499277