Why do they feel slow?
Discussion
TheDeuce said:
This has been an interesting conversation, but I'm still left feeling the same overall. With a reasonable but not big range, it should be possible to package an MX5, keep the driving position (maybe an a tiny bit higher - who cares, it's an EV, it's not going to roll much anyway) and position the cellpack to give great Wright distribution and essentially have it out of the cabin space. The car would be a fun rocket off the line and corner like it's on rails.
MX5 has limited headroom already with my head being uncomfortably close to the hardtop.GT9 said:
RobbyJ said:
The Rimac battery is pretty much T Shaped. Yes a different price level but these things tend to flow down eventually.
Most of that battery is behind the seats.If you've ever been to Japan you'll know how narrow the streets there can be.
The Nevera is 2 metres wide, an MX5 needs to be 1.7 metres wide, it is not going to have a spine battery, I can virtually guarantee it.
If it were a 40kwh pack, within the width and length of the cabin space, how deep would it actually need to be?
GT9 said:
If you've ever been to Japan you'll know how narrow the streets there can be.
The Nevera is 2 metres wide, an MX5 needs to be 1.7 metres wide, it is not going to have a spine battery, I can virtually guarantee it.
Loads of room for additional battery packaging inside the tunnel.The Nevera is 2 metres wide, an MX5 needs to be 1.7 metres wide, it is not going to have a spine battery, I can virtually guarantee it.
bigothunter said:
TheDeuce said:
This has been an interesting conversation, but I'm still left feeling the same overall. With a reasonable but not big range, it should be possible to package an MX5, keep the driving position (maybe an a tiny bit higher - who cares, it's an EV, it's not going to roll much anyway) and position the cellpack to give great Wright distribution and essentially have it out of the cabin space. The car would be a fun rocket off the line and corner like it's on rails.
MX5 has limited headroom already with my head being uncomfortably close to the hardtop.bigothunter said:
GT9 said:
If you've ever been to Japan you'll know how narrow the streets there can be.
The Nevera is 2 metres wide, an MX5 needs to be 1.7 metres wide, it is not going to have a spine battery, I can virtually guarantee it.
Loads of room for additional battery packaging inside the tunnel.The Nevera is 2 metres wide, an MX5 needs to be 1.7 metres wide, it is not going to have a spine battery, I can virtually guarantee it.
TheDeuce said:
One assumes that if the driver was sat a little higher out of necessity, they might consider the roof height too. This is all about compromise and smart engineering - an EV variant probably will change in size/shape a little here and there. If the car ends up 2 inches higher that's not a catastrophy if the CoG drops by several inches is it?
A 2" taller MX5 may not be particularly aesthetic or appealing...bigothunter said:
TheDeuce said:
One assumes that if the driver was sat a little higher out of necessity, they might consider the roof height too. This is all about compromise and smart engineering - an EV variant probably will change in size/shape a little here and there. If the car ends up 2 inches higher that's not a catastrophy if the CoG drops by several inches is it?
A 2" taller MX5 may not be particularly aesthetic or appealing...GT9 said:
Michelin designed something called active wheel a decade ago. Maybe, just maybe, something like that would create the space needed between the rear wheels for a solid state battery behind the seats. On the other hand, what a ridiculous idea.
But then you still have the weight in the wrong place.. Surely inverter up front, pack in the middle - as far forwards as possible, motor at the back.
I'd love to know how shallow a 40kwh pack could actually be. If it was, say, 4 inches I would imagine the Japanese could redesign the seat bases to be at least two inches shallower and use some high-tech foam to make them comfortable still. They could probably split the difference of the remaining two inches by reworking the platform to have a typical EV flat floor an a lower overall floor, and a roofline one inch taller.
Surely getting the weight in the right place has to be king in a sportscar, even if doing so leads to little extra effort and compromise along the way.
TheDeuce said:
Surely getting the weight in the right place has to be king in a sportscar, even if doing so leads to little extra effort and compromise along the way.
Polar moment of inertia is more important because it affects yaw response.Low mass centre is always beneficial but returns diminish. Weight transfer in roll and pitch changes. Providing mass centre is not higher than conventional ICE MX5, all will be fine
bigothunter said:
Polar moment of inertia is more important because it affects yaw response.
Low mass centre is always beneficial but returns diminish. Weight transfer in roll and pitch changes. Providing mass centre is not higher than conventional ICE MX5, all will be fine
Tbh there's a lot to be said to getting the CoG as close to the axle as possible. Under braking, it makes massive difference. Under acceleration it also matters but less so in something relatively "slow" and RWD like the MX5. There's a reason the Model S outbraking the AMG GT 4, BMW M5, Porsche Panamera Turbo S despite being so heavy (well, they all are, but...). The very low CoG is, afaik, the main reason for that. And none of them are pick up trucks.Low mass centre is always beneficial but returns diminish. Weight transfer in roll and pitch changes. Providing mass centre is not higher than conventional ICE MX5, all will be fine
bigothunter said:
Polar moment of inertia is more important because it affects yaw response.
Which is why I'm skeptical about a front-mounted battery, especially when you consider that the axis of yaw rotation is usually closer to the rear axle than the front. I suppose adding a bit of rear wheel steering can help.Whilst I can understand why you want the battery between the passenger and driver, I just don't think there's enough room there to keep the car narrow enough and offer enough range. If you look at the centre console of the petrol cars it's wider where the bell housing is then tapers as you move backwards.
ZesPak said:
Tbh there's a lot to be said to getting the CoG as close to the axle as possible. Under braking, it makes massive difference.
There's a reason the Model S outbraking the AMG GT 4, BMW M5, Porsche Panamera Turbo S despite being so heavy (well, they all are, but...). The very low CoG is, afaik, the main reason for that.
Your technical explanation of how lower mass centre than AMG GT 4, BMW M5, Porsche Panamera Turbo S improves stopping distance, would be appreciated...There's a reason the Model S outbraking the AMG GT 4, BMW M5, Porsche Panamera Turbo S despite being so heavy (well, they all are, but...). The very low CoG is, afaik, the main reason for that.
GT9 said:
Which is why I'm skeptical about a front-mounted battery, especially when you consider that the axis of yaw rotation is usually closer to the rear axle than the front. I suppose adding a bit of rear wheel steering can help.
Whilst I can understand why you want the battery between the passenger and driver, I just don't think there's enough room there to keep the car narrow enough and offer enough range. If you look at the centre console of the petrol cars it's wider where the bell housing is then tapers as you move backwards.
They could always build a car that doesn't cater for fat people?Whilst I can understand why you want the battery between the passenger and driver, I just don't think there's enough room there to keep the car narrow enough and offer enough range. If you look at the centre console of the petrol cars it's wider where the bell housing is then tapers as you move backwards.
Alfa seem to build cars which are only suitable for people shorter than me.
Whatever battery sports car they might build, it won't be an MX-5 as such will it?
OutInTheShed said:
GT9 said:
Which is why I'm skeptical about a front-mounted battery, especially when you consider that the axis of yaw rotation is usually closer to the rear axle than the front. I suppose adding a bit of rear wheel steering can help.
Whilst I can understand why you want the battery between the passenger and driver, I just don't think there's enough room there to keep the car narrow enough and offer enough range. If you look at the centre console of the petrol cars it's wider where the bell housing is then tapers as you move backwards.
They could always build a car that doesn't cater for fat people?Whilst I can understand why you want the battery between the passenger and driver, I just don't think there's enough room there to keep the car narrow enough and offer enough range. If you look at the centre console of the petrol cars it's wider where the bell housing is then tapers as you move backwards.
Alfa seem to build cars which are only suitable for people shorter than me.
Whatever battery sports car they might build, it won't be an MX-5 as such will it?
If they sort the weight and packaging, it could be remarkably similar to the current MX5, simply a different powertrain. The MX5 has changed here and there, sometimes quite significantly from generation to generation anyway, all cars have to as regulation and buyer preferences evolve.
TheDeuce said:
GT9 said:
TheDeuce said:
But then you still have the weight in the wrong place.
You mean like the 911 does Porsche have ultimately made it work that way, but it's taken many decades of dragging 911's out of ditches and hedgerows
And 911 engine sound is legendary
ts and giggles.bigothunter said:
Your technical explanation of how lower mass centre than AMG GT 4, BMW M5, Porsche Panamera Turbo S improves stopping distance, would be appreciated...
Overly simplified:Once you brake, the "weight shifts forward". Basically your front axle becomes the fulcrum for the inertia wanting to go over the car, lifting the rear wheels. In general, under hard braking, the rear wheels do less than 25% of the work.
If you have your CoG higher, it'll have a greater lever to pull the rear wheels from the ground.
If you have it lower, rear wheels work harder giving much better braking results.
For acceleration at that (Tesla) level, it also means the front wheels experience less lift thus can put more power down.
I made a quick and dirty sketch that isn't scientific at all but should explain the idea.
An extreme example would be motorcycles. Braking hard, you want your weight (rider) to be very low. If you don't, you get a "stoppie", which basically means that instead of 10% of the braking on the rear wheel, you get 0%.
Edited by ZesPak on Thursday 23 June 11:43
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