Team-BHP - Weight reduction - Acceleration & Braking

I am fan of lightweighting philosophy when it comes to car design. Recently came across an interesting video by ChrisFix, where he goes on to reduce the weight of an E46 to prepare it for track use. Of course track cars are stripped off to bare essentials before making them race ready. This is one such interesting video, where it presents an opportunity to understand how much the individual parts in a car weigh and to make some informed choices, when ticking the variants/options boxes, when we buy a car:

https://www.youtube.com/watch?v=MCiNGmwopx4

Some of the observations and takeaways in general :

1. Being someone who DIY maintained an E90 myself, I cannot stop wondering how every generation of BMW is engineered with maintenance in mind. Tabs that wont break, torx screws for plastic parts, easily accessable fasteners but hidden to plain sight.

2. Sound deadening only at places which makes sense.

3. Heavy padding and carpets inside cabin, which is one of the reasons to own a luxury car and why people like them. The one other brand which obsesses with sound proofing is Lexus. See what they do with their entry level model.
https://www.youtube.com/watch?v=Di_hgK1Ne7I

Now one can imagine what they would have done with their flagship :)

4. Accelerates faster, corners nimble (fun) and stops sooner (safety) and uses less brakepad, when a car sheds it's weight. Also helps in downsizing of several other components, which in turn improves fuel economy. However in this case, the weight reduction is done for a different purpose.

5. Motorised seats are super heavy and complex things. Most of the times people adjust the seat once in a blue moon and the amount of spare parts gone into making an electrically adjustable seat is way too much compared to a mechanically adjustable one. Unless there is a need, keeping lesser complexity in the cars is easier for time and wallet.

6. 196 kgs reduced in total. I will not reveal the other numbers, as it spoils the viewing experience.

With improvements in materials and new simple (less complex) drivetrains the whole car's weight can be reduced to make them fun and safe. Hope we will see such car designs in future. Feel free to add your observations to make it an interesting and informative thread.

Weight reduction is definitely what has been going around in the car industry for quite some time right now. From adoption of materials like aluminum, carbon fiber etc. manufacturers in the recent years have found way to make cars that are more efficient not just in terms of mileage, but also safety and handling.

While all that is good, added features in newer cars might also increase weight. For instance panoramic sunroofs not only weigh heavier, but also affect mileage due to increased AC consumption. Music systems are going from more than 4 speakers, while motorized seats add weight to the car.

Then there is also the case of undesired weight reductions in the form of missing spare tyres ! :Frustrati

It is true, as per physics laws, acceleration and braking would be more effective as weight reduces. But we should be aware that Manufacturers are already at their beyond optimal levels in designing the cars with light weight. Ex: Engines are made from aluminium instead of iron, monocoque designs instead of on frame body(except few cars), sheet metal used have less gauge, etc.

And the negative side of reducing weight is, the stability the car offers reduces drastically. At high speed, you will never get comfortable if the car is light weight. So, if you want to have some benefits, you have to compromise on something else.

Hence, the best solution to this problem is, to keep the car stock and trust the manufacturer has optimised the car for performance and stability by design. Also purchase car from a trusted manufacturer.

I align with OP points about requirement of few accessories like motorized seats, panoramic view. In my view, They are not needed for a car. But not from the point of view of reducing weight. As rightly said, to change the seat position once in a blue moon, I can not afford to spend more than 10-15k as dead capital. And to see the nature that is freely available for entire universe outside of the car, why should I pay a lakh or more to the car manufacturer? And then, create multiple posts in social media to crib about the leakages and other related issues?

A Caveat: Your mileage may vary :
I did my own bit of experimentation in shedding extra weight and observing the mileage in my car. I dumped the spare wheel (about 30 kg) and the Woofer (about 12 kg) and the toolkit (about 5kg) when driving inside city. I had shed some 40-50 kg in all and when checked the mileage was all the same. The car didn't care about the reduction in weight. It is all about the overall weight. In a 2 ton car, mere reduction of 50 kg means nothing.

The easiest thing to do is not to add any additional weight. Massive subwoofers, multiple amps, several litres of cleaning liquids, vacuum cleaner, air compressor, car cover , some weirdly named duster, all the parts replaced that are still in the boot like a trophy etc etc.

Those who upgrade tires should check the weight of the replacement set too for good measure, I'm looking at you Jeepers :)

Weight reduction is not as easy as one would think, you could strip the car down to bare essentials but then you would have upset the balance of the vehicle, it may travel fast in a straight line but not necessarily handle better. The position of the heaviest bits in a production car is designed with the weight of all those sound proofing and convenience features in mind.

Quote:

Originally Posted by gkveda (Post 5080123)

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And the negative side of reducing weight is, the stability the car offers reduces drastically. At high speed, you will never get comfortable if the car is light weight. So, if you want to have some benefits, you have to compromise on something else.

Not really. High speed stability is about suspension and aerodynamics. Compare driving a Jaguar x308, weighing in at 1800kg to a Lotus Elise, 750 kg, at 200 km/h and you will experience a remarkable difference.

Jeroen

Quote:

Originally Posted by gkveda (Post 5080123)

And the negative side of reducing weight is, the stability the car offers reduces drastically. At high speed, you will never get comfortable if the car is light weight. So, if you want to have some benefits, you have to compromise on something else.

Quote:

Originally Posted by Jeroen (Post 5080684)

100% agree with Jeroen here. Aerodynamics and "downforce" are more crucial for high speed stability than dead weight. It is the downforce that keeps the car planted at high speed. One can get into a lot of technical details on this topic, but to keep it simple we can say this: Dead weight is bad. Downforce is good. The reason is that dead weight adds to the mass, which slows down acceleration, for the same engine power (F = mass x acceleration). However, downforce gives stability without adding to the mass, and thus can give all the benefits at high speed without reducing the acceleration. Downforce is really the magic!

Quote:

Originally Posted by GTO (Post 5080658)

Great for track use & drag racers :thumbs up, but absolutely pointless for on-the-public-road usage. I'd rather have 100 more kilos and enjoy the amenities 99% of the time than have the benefits of weight reduction 1% of the time.

Very true. And certainly true for our typical family cars in India. For example, if I take 3 family members with me (each weighing about 65kg on average), I have about 200kg extra weight in the car and all discussion about weight reduction is moot. rl: