The Diesel is dead, long live the ....errr... hybrid

 Diesel has been the drug of all nations (perhaps except for the US, Venezuela and UAE countries).

It's been so for all the wrong and all the good reasons. 

Diesel has always been a child for the industry. 

The fact that Diesel was a by-product of OIL refining, composed mainly from grease, meant it was a cheap fuel. 

Also, the type of slow burning combustion, made the engine design long in stroke, and the injection cycle successive instead of a sudden violent explosion like the gas powered engine. This means it's got torque because of the long stroke design, but also because of the constant explosion happening all the way down stroke, one after the other. 

In order for this to work, the engines quickly evolved from the pre-chamber indirect injection design, into the Direct Injection phase of design where you could control the injection much better. 

Since the Diesel engine inputs just air and then squeezes the diesel fuel into the chamber by injection, it reaches very high compressions...20:1 for instance. The air will not detonate on it's own and the higher the compression, the higher the temperature, resulting on an easier combustion of diesel as it gets into the chamber (or pre-chamber on old ones).

The slow explosion and constant supply of grease down stroke also meant that the output generated less heat, but more emissions, as there is only so much residual oxygen left to burn as the explosions succeed each other, and fuel coola down the chamber... you see those tuner diesels generating clouds of black smoke, some are bad tuningz wome are on purpose to avoid hmthe piston to melt...depends on how extreme it is tuned.

This means one thing: Diesel was a perfect fit for the TURBO charger. It can input air at huge pressures without detonating, compress it further and then, the extra air, means extra oxygen to burn, and less emissions (this, of course, until the hillbilly tuner comes along and ups the injection map, creating some disastrous cuttlefish on wheels).

Emissions aren't really a problem on the industrial diesel. The exhaust temperatures can be sustained high and the burn process completed at the catalytic converter, while the filter grabs most of the carbon dust. 

The problem becomes when you miniaturize the Diesel and put into your car! The catalytic converter can't run at the same temperature or have the same length, the filters need to be able to endure between maintenance cycles and we end up adding urine to the thing and call it ADBlue... yes AdBlue is just pee! expensive pee. 

Das AUTO

Back in 1993, Mr. Ferdinand Piech (grandson of the great Ferdinand Porsche), was onboard to VW (in ruins) and picked it up from the ground floor, up. 

His great ace: the TDI. The diesel that has both the power, the torque and the size for a small car. 

Sure you had small diesel engines in cars, but they where... well bad! They were used in cars that needed to transport heavy loads and at a low consumption form a cheap fuel.

VW TDI spawned the new Diesel with the lively feeling that all other cars didn't have.

Sure pollution standards where a problem because the diesel car doesn't have industrial sized catalytic and filter to make it clean. 

This lead to the now so well known Diesel-gate. Why? simple... it's not industrial, it's not clean. In order to be clean it would have to have much less output for the non industrial catalytic converter and particle filter to run efficiently. This meant burning less, inputting less, so less diesel and less air = less power and no one likes the TDI as the old diesel it's been marketed to replace!

And BOOM goes the scandal.

Scandal was out, VW was cheating the certification tests making the car run really lean, and nothing to do with what you'd find out to be the performance (and resulting emissions) on the road.

Surprise surprise, all other brands, that managed to follow the TDI trend with more "interesting" diesels, where cheating too. 

And the reasons are not hard to understand: If you comply with emissions, you create an engine that is just as un-interesting as any normal turbo-diesel where before them.

But the problem was:

That the scandal generated news pieces and documentaries, so all the sudden, the sheep population had the knowledge that: Diesel engines produce NOx, NOx reacts with Ozone in upper atmosphere and generates smog and anyone coming into a metropolis can see the smog dome form the distance. OOOPS the sheep had awaken a tiny little bit.

VW had been selling the CLEAN Diesel Idea and it was just a lie. Go figure... a big company and their marketing department lying to public... tststs.

Now? Diesels are bad! Simple

guess what they've always been!

But people like their SUV's and Minivans, and trucks... so, if you're pulling 2 tonnes of metal around, you're gas engine will not be good to use unless it it huge. If it is huge, it takes up more space, needs more cooling, drinks more gas, needs bigger catalytic... the scaling becomes a problem. 

AND THAT IS WHY small engines with big turbos are a trend. Manufacturers look to use the Turbo as a replacement for displacement and make the engines smaller, to pull the necessary weight us monkeys have gotten used to go around in!

But this doesn't have the low end torque that every one got hooked on with the TDI.

So what's to happen to the world now?

There is a new kid on the block.

The Electric car! A bad idea made public, much like VW's clean diesel. The electric car is not really the problem. The marketing is!

musk has been selling his teslas as a green solution! however the lithium in it's batteries is a real problem for ground contamination, the electricity it runs on is not clean at most countries and the battery suffers from memory degradation, meaning you'll be changing batteries every 2 to 4 years, and it will need to be discarded and new ones need to be placed in. That means more lithium and cobalt mining and pollution.

However the Electric motor has a very high torque and it's instantly available. That is why trains use them.

Electrics are then the new Diesel: torque as hell and bad for the environment.

And this is without considering the safety hazard. Lithium batteries tent to explode and burn for weeks, and by doing so, not only they cook people inside the cars, they also exhaust VERY HARMFUL GASES that can harm anyone breathing them.... from fire fighters to people living nearby the fire. 

Fires in lithium battery factories are well known (recurring fires actually), fires with crashed electric cars are common and normally they are left to burn for a week inside a warehouse with vents and filters, as is next to impossible to put out a fire on a battery that generates it's combustible components.

There is also an important thing to consider - The electrical grid!

If everyone starts using electric cars (and if you ignore the suicide rate increase due to the non masculin experience of driving them) then it means that people get turn on the lights, the oven, the computer, the tv, the music amplifier and the car charger. So when people need more electricity will be when everyone will be overloading the grid while charging inefficient lithium batteries. Not smart. Would make more sense during the day as they are away at their work places. But if they start doing this at the workplace, the grid will suffer the hit of all those cars, computers, office lights, elevators, coffee machines... The works!

The solution: aside form carbon batteries, is using battery packs, that you leave home to charge during the day and then exchange when you get back home at evening. It's everyone's dream, to get back home and perform dangerous car maintenance while shifting a heavy, high energy packed with a direct voltage discharge hazard, power unit on your car... so no... not really a solution.

But there is a difference!

You see, the Diesel engine produces torque and pollution, but with electrics, the engine does not produce pollution, it's the battery that produces pollution and potentially, the generation of energy to store in the battery that produces the pollution. 

And this does open the space for a solution!

Welcome to sodium-carbon and solid-state capacitor-battery:

Some brands that do not have a private ownership of South-African lithium mines, diverted from the lithium-ion battery. As such, you now have BYD, Honda and Toyota working battery solutions that do not contaminate soils forever... of course this goes against musk agenda of contaminating the world with lithium using the Clean car message! seen this before? I'm eagerly expecting the muskgate scandal... got popcorn and all.

This means there are several solutions out there to fix the pollution problem and allow people that love torque to enjoy the electrics. 

Solid state batteries live way longer than lithium ones and can charge in 20 minutes.

Sodium Carbon ones will be even more efficient and never need replacing... and then, then there is Toyota and Honda with Hydrogen fuel cells that can both be used to produce electricity and be burnt in combustion with a bang far more explosive than gasoline.

Meanwhile, in Porsche land

Porsche, as usual, is the last brand that keeps pushing boundaries instead of trowing in the towel. 

Porsche has devices a carbon neutral fuel. It's synthetic gasoline used carbon pulled form the air, meaning that it will produce exactly the same that was pulled form the atmosphere... and hence neutral.

This will allow for the Gasoline engine to live longer as a viable option. 

So, diesel (at least in the small car), seams is dead.

So, diesel (at least in the small car), seams is dead. Makes sense that it is. I've explained this over the years to several people and it was a matter of time until it became clear. 

SO IF diesel is dead and electrics blow up and contaminate worse then diesel...

I believe the future is hybrid and Toyota and Honda are on the right track. 

By having a fuel cartige of hydrogen, you can use it to light a fuel cell that produces electricity for a electric engine for all the torque needing functions, and then shift to internal combustion for high revs and hydrogen explodes even more violently and faster then gasoline. 

There is also the fact that, if your car produces water as a result of either fuel cell or internal combustion, you can recicle them into a sodium rich deposit inside the car, and then use the ceiling of the car with solar panels to generate hydrogen and oxygen through electrolysis and either recharge that hydrogen cell or just plainly charge a carbon nanotube battery pack. 

Carbon nanotubes are able to store 3x more energy under the same density as lithium oxide ions... and they are lighter, and being carbon, they can be also part of the car's structure... This means that your battery can be the same carbon monochoque that supports your car and saves your like if you crash.

The Diesel is dead, so is the electric lithium polymer battery, long live the hydrogen hybrid. 

In the engine is the Heart of a car, the chassis is its soul... and there are several types of soul.

It's common to hear that the engine is the heart of the car. 

The electronics are the brain and then there is, to my view, one of the most important things in a car > the chassis.  What are we to call it? My atheist brain points to Character... but for the sake of generic compatibility, lat's call it: soul.

Souls seams important enough to consider and mention.

Several cars have very different chassis, and it's really hard to categorize them, but let's try to explain and have this split into sections.

And that means a series of POSTS as the data is quite a lot to process, but I'm really having very little tine to dedicate to this, so... all in one, read it in sections... you'll be fine. 

The build type:

    This relates to the design on the main structure of the chassis. The basis of the design, per say. It will have different results depending of the different suspension design applied to it, but you can split the chassis design base into 4 main designs:

    - Tubular:

        Tubular chassis are common in fully race built cars. Nascar cars are tubular designs that have a "body" looking like the model they are supposed to reflect for marketing purposes. It's a design that brings in the best torsional rigidity with the lightest design. The main problem with this design is that, if damaged, it's very difficult to repair, the time and skill to build it is quite high and as such, race driven design.

        Dragsters are tubular designs... and one of my favorite cars of all time, the original Gull-wing Mercedes, is , as a race bread animal, tubular framed too.

    - Ladder frame:

        Ladder design is very common on old cars or contemporary Heavy load vehicles such as pickups, trucks and military vehicles. This is a easy to build design, but it is a heavy solution ( the chassis will then get married to the body and both will be heavier). It's a strong design but tends to suffer from poor torsional rigidity, and as such only really usable on cars that aren't made to corner as speed, both because the flexing will be bad and the weight too.

    - Backbone:

        The backbone centers the concept of the ladder design in a sort of an X and reduces the parallel sections with a central beam. It's a concept suited for offroading due to the clearance the chassis provides to the moving parts of the axles and suspension. By tightening the design, there are instant improvements over the ladder design. It is however a costly design, both to build and to maintain the car. 

    Due to robustness it was applied to military vehicles that have to endure offroad ability while supporting massive loads.

        But there are exceptions here. Build the backbone with metal sheet profiles welded together wit proper welding, and you may end up with an excellent and light chassis base... but don't crash it!

This is the chassis of the first Lotus Elan. The body of the Elan was made from fibre glass, the chassis had to bear all the strength, so, as you can imagine, this Back Bone design opening with the shape of an X, sure was strong.

    - Xframe:

        The x frame is step forward from the back bone design by making it almost like if a giant had squeezed the ladder design right in the middle. Torsional rigidity is a problem but it is much lighter than the backbone. This meant that, as long as the body was string enough, it could result in a decent amount of torsional rigidity, at a lower weight.

        In order to fix this, lateral ladder structures where added to the xframe, making it less dependent on the body rigidity. 

    - Monocoque / Unibody :

        It's a design that was adapted from ship building, airplane manufacturing, and evidently, being string and light, it quickly found it's way into cars. It's the most used method today, and even the variations of today's chassis are to a point, monocoque + some other design hybrid. It offers a design easy to repair, strong and light, but also (if with a roof design) with an excellent torsional rigidity. 

 

        Sub-type -The Xbone-Frame design:

            This is an innovative design form Honda, that fuses concepts, in order to address the main problem of a monocoque design on a topless car: no roof! It's a simple concept to understand. Grab a shoe-box and, with the lid on try to torsion it... it will not flex... even being made from cardboard and being light. Now remove the lid  (roof) and try the same.. it flexes all over the place.

            Honda, while building the Honda S2000, had specific needs for the chassis, as the car was purposely built as a high performance sports car with impeccable handling. If couldn't be heavy the having a monocoque without a roof and added reinforcements (as they normally do with topless cars) is out to the question. So Honda turned to the BackBone design, the xframe design and the ladder design and adapted them to the monocoque, creating the x-bone frame design. 

            In essence, they use the standard floor pan on a monocoque design, but then they move what would be the roof of the design into the high part of the transmission tunnel of the car (much like the back bone design), Squeezed it together making a sort of an X out of a Ladder design, much like the Xframe, and then the ladder design surrounded this and bound it to the monocoque. Brilliant!

It looks like a Ladder design and an X frame all together

But then The X is elevated like the Backbone as if it was a top that was lowered...

...to the mid section of the car, right on top of the transmission tunnel like the back bone.

But then integrated with the monocoque profiles.

and reinforced with stronger profiles like the reinforcements on a Carbon monocoque design.

  It's the ultimate hybrid to have on steel.

        Sub-type - Carbon Monocoque:

            If price is not a problem, ans lightness is the word, then nothing beats the carbon monocoque for torsional rigidity, lightness and expensive price. It's the unicorn of chassis designs and it's reserved for super and hyper-car production due to the price, lack of massification of the process and the requirements of tools to be able to produce them.

BUT the chassis is not only the frame:

    Sure the main thing about a chassis is the frame as it makes the car what it can become from design, but then there are options regarding the accessory elements on a chassis that will either enhance its design, or show it's flaws or limitations.

    Because of the Myriad of options, unless the chassis incorporates the suspension type in it's design, there is a common SUBframe that supports the suspension and attaches to the frame. There are 2 reasons for this, the support for several options over the same chassis design, and the maintenance/repair options that having a subframe separate from the main frame allows for.

    1st - Suspension design:

        - Types and implementations

Why? well because:

            - Independent

            The concept of the independent suspension is simple! Each wheel is independent form the other and free to move. This allows for adjustments to the way each wheel maintain the camber and toe angles while cornering or digesting road imperfections.

                - Trailing Arm:

                    Probably the most simple design in a suspension. If you like lego like I did, you can build one with 4 pieces! As such, as one can imagine it is the base of all suspension designs and all the changes done depart form this. Either by shifting the position by 90% and stabilizing like the wishbone, or Mcpherson, or maintaining the angle and adding rigidity, as the twist-beam. Even the simplest solid axle is supported by the trailing arm design, so... this is the father of them all. 

                    - Citroen's ingenious Pull-rod trailing arm:

                        If there is a way to explain Citroen is their ingenious suspension designs. It all started with the 2CV that had to be both tremendously good at digesting country side and war destroyed roads, and also be very simple do produce, maintain and at a low cost... I mean.... the list of demands is the size of texas. What they've come up with was the trailing arm design, coupled with wnat today we use in F1 as the push-rod, but in this case, inverted as PULL-rod. They then mass the rod over a tube along the chassis that has both springs of both front and read suspension systems, minimizing space usage, allowing for a more generous cabin. It's just brilliant and simple... take a good look:

                - Double Wishbone:

                    Double wishbone is a perfect way to control the car wheel movement, and as such it is used on 90% of sports cars. It is an expensive design and consumes space, being less frequent in axles where there is little space to use. Front engine'd cars with transversal engines would be an excellent example of how space does not allow for double wishbone.

                    - Double Wishbone with push rod:

                        This is the pinnacle of suspension design. All the strengths of the double wishbone, in terms of independent wheel movement and maintaining road contact, while reducing the sprung weight by moving the coil-on-damper assembly to a fixed location inside the chassis. Why don't we see this in all cars? COST! But F1 cars extensively use this. 

The problem then becomes:

Where are we going to place the engine?

...or the golf clubs for that matter.

                - Macpherson

                This desing is an atempt to simplify cost and space on the doubel wishbone. It essencially uses a very robust damper to use it structuraly as both damper and the top wishbone.

                - Multi-link

                Multilink tries to address several problems all at once. Cost savings by making it usable on several models with simple adjustments, space for potential differentials (manly on AWD applications), cabin space. It essentially brakes-down the wishbone into several links that anchor to different point in the chassis, maximizing space usage. Since it is more compact, it's often seen with the shock absorver separate from the spring.

                        - Volvo-s Delta-link

                        Citroen may be excellent at suspension design, but Volvo is not bad at all. In a way to improve the multi-link with a passive rear steering system, Volvo designed the delta link. 

                        Much like the Multi link breaks the wishbone in several independent links to the chassis, Volvo decides to stretch the wishbone across the chassis and try a hybrid between the wishbone,  multilink and the torsion beam. And it worked beautifully. 

                        Why was it only used on the P80 chassis and then abandoned? Well Volvo customers aren't really the racing type, and the feel of the chassis having to bend the bushings before turning in, scared a lot of customers and then... it was no more. I still have one and it is very fun to drive... but you do have to know what is happening before panicking. I admit, first impressions, unless you are very sharp and spirited with the steering wheel, it will feel like the car is under steering, until the suspension load overcomes the bushings strength and then it will graciously start to turn in, allowing for a faster corner exit. The stronger the bushing rubber, the worse this feeling is...but you need to understand that this is a passive system, and as such it will require physics to happen. Turn in like a pilot, though, and you're right in the zone the system was built to excel in... and there lies the paradox: you buy a family saloon, fill it with the kids, wife, dog, luggage for the weekend, and then steer into corners like if your in a time attack... hummm not! I mean, sure, I do that, but my wife has the same sort of madness i have, and the kids are a genetic milkshake of the 2 of us, so naturally they love the tires screaming thought the corners :s! BUT the majority of people our there don't really do this.

            - Dependent

                This is an old design but it is still used today on cars that work on extreme torque levels or terrains. But guess what: it is still supported by the good old trailing arm... it just tights the trailing arms to a rigid structure and then makes the wheels dependent on each other. 

            - Semi-independent

            This design focus on 2 principles. The first is cost reduction, the second is space saving, allowing for more boot size. However there are advantages to the design, under some circumstances and that may be the cause of some decisions that, at first look may seem dumb. But we'll get to the point soon enough. The semi-independent suspension design is a rigid structure much like the solid axle form the dependent suspension, however the hay it connects to the chassis and some structural flexibility will annoy it to, under some circumstances behave with wheel independence... and that is what it's semi independent, the semi relies on bushings strength and torsional rigidity of the assembly. 

                - Torsion beam (twistbeam) : try evolving the Trailing arm, and adding a ladder design to it, with a rigid main beam nest to the bushings, and a less sturdy on half way through... and you get a torsion beam design. Is it better? is it worse? depends who you talk to, but IMO it will depend on the usage or purpose. 

However think that for some reason, Ford Motorsports changed the normal torsion beam on the MK1puma to a independent trailing arm for the S1400 and S1600 chassis.

They changed from this... 

...to this.

                So if you think about this for a while it should clear notions in your head pretty easy, but we'll get back to this latter on the article. 

                    - ScottRussell

                        The ScottRussell is a type of trailing arm suspension, but the coupling of the trailing arm is not done at the top oh the H structure, but rather half way through the beam it self using the coupling method called ScottRussel. The movement is then limited to up and down, over a possible angle on the axis, but there is no change in the wheel position on the chassis towards the ground, unlike the trailing arm that describes 2 angles. to the chassis. This means less movement, and as such less more control on the physics.

        - Damping implementations:

        So now that we've covered the majority of designs for the linkages of the moving parts to the chassis, and chassis types, the works. It's time to look at how the energy from the movement is dissipated and controlled. 

            - Coil and damper

            Typically used on multi links, trailing arms and torsion beam designs.

                - Coil over damper

                This design is used on double wishbone, McPherson and push-rod designs. Some are adjustable (racing ones) but the majority is manufacturer fixed.

            - Leaf springs

            Used on simple (cheap) designs, or on extreme load designs where handling in not an important factor. Military vehicles and trucks normally use this design.

One might argue that the loads are what determines the leaf spring instead of the coil... and that a coil to handle all that load would be huge, but then:

so if it's good for trains, it's good  for trucks, and the only excuse left is the cheap one!

            Well this is, old technology. No really... it is!

 see?

And yet, Corvettes till the C7, use this still!!

You see, they claim that they needed to lower the car for aerodynamic purpose and that a coil would take too much space... sounds interesting...err delusional. That's maybe what they should replace push-rod with, in F1!

That's probably why in the C8 they decided to change that with coil springs... or maybe because it was designed by an European team, the cornering abilities where part of the equation :s

I'd ask for my money back, but then again, I'd never buy a vette.

            - Pneumatic

            Pneumatic suspension have long been used on trucks and also luxury cars. They allow for adjusting of ride height and stiffness. Particularly interesting in the truck world, where you may have uneven cargo and as such the suspension may increase pressure to compensate the heavier side and not as much on less heavier one. 

On luxury cars it is used to enable quick changes between ride height and softness, but also, because luxury cars are heavier than they should be, help to control body roll. 

 

It would make sense on sports cars, but the weight of the compressor and tank, plus the piping, plus the space used normally loses to active systems that can improve the spring on damper tremendously and make the advantage of the pneumatic, null.

In order to be effective as a active suspension at the speeds a track car needs to, it would have to have extremely high pressures and a tank to match.  

            - Hidro pneumatic

            Hidro pneumatic tends to solve the fully pneumatic usage issue for fast response. By combining oil and gas, Gas allows for the damping part of the equation while oil takes care of the height and reaction time (being oil a non compressible fluid, unlike air).

            Some of today's shock absorvers use this principle, and although the article focus on the entire string /damper assembly, the principle is still valid. 

                - Hydragas

                Hydragas is a concept that uses the exact same principle the amount or gas and the pressure is used to support the spring effect.

Some hydragas applications cross link the oil deposits so that the car right tryes to maintain the same height going through bumps.

                - Citroen Hidractive

                As expected, Citroen innovated on this concept and created their own system. Their Hydro pneumatic suspension debuted in the Citroen DS was remarkable and used compressed air to generate the spring effect, but the pre-loading of the compressed air deposit was controlled over with oil. There was then a valve to connect that secondary compression chamber with the direct oil chamber on the damper. 

                This system allowed for control on both ride height and also stiffness of the damping, by managing the oil going into the primary chamber and the pressure regulator that allowed oil into the secondary chamber, next to the air precharged balloon. 

The way that the dampers interconnect to each other and the extra dampers placed in the middle of the system, then allowed for a very intelligent and comfortable suspension system.

This system was so brilliant, that the DS could run on 3 wheels! Literally!

This then evolved and pinnacled with electronic adaptive control over the pressurization of the dampers and resulted in the Xantia Activa. This baby was able to use lateral acceleration and ground level distance to then send oil to the dampers on that side of the car and maintain a perfect ground clearance, maximizing grip like it was on rails. Just brilliant engineering.

Yes, it is THAT brilliant. Check the video:

        - Hydroelastic    

        This is one of those hybrids that really didn't work all that good. But the concept is simple: grab  an hydragas, dump the air pressure balloon as use a rubber expandable one filled with fluid, and make the elastic expanding force your "spring".                                                                                                                                                                                                                                                                               

    2nd - Drive train design:

    The drive train design has a tremendous impact on the chassis soul. Not only regarding how the power get's delivered to the ground, and the reactions the car has as a result, but, their connection is a bit deeper than that. If you are smart enough to by your car from a brand that fine tunes the chassis for fun, you may end up discovering that, under grip driving the chassis may seem unbalanced and under-steering, but when you unleash it's full potential under a controlled drift, you get the why as to that specific chassis tuning setting.... I'll expand on this later. 

        - Types

            - FWD

            Stands for Forward Wheel Drive. Also known as called FF, standing for Front Engined Front wheel drive. The front wheels are the ones passing the engine power to the ground. 

            This simple fact means several immediate considerations. First of all, the front wheels will be overloaded with the burden of steering the car and delivering power to the ground. This is minimized by the fact that the engine and gear box will be sitting in the front of the car, helping the car squeeze the wheels to the ground and maximize traction. 

            HOWEVER, it generates 2 problems: If you accelerate, the weight shifts to the back of the car and the nose of the car lifts, making the power delivery more difficult. The chassis suspension tuning can help by softening the back and slightly elevating it, but  does not fix the issue. The second problem is the fact that, being front heavy, the car has a tendency to maintain it's inertia of movement and changing direction is hard by definition. 

            These factors normally translate to, inf ignoring electronics, you do not want more than 250bhp on a FF car, nor to you want more than 300nm of torque. Electronics and active differentials have allowed these numbers to be pushed forward but always at the expense of tire thread and with a lot of help form active rear axles to cope with the understeer feature of this chassis type. 

            This does not mean that it is bad. It just has it's limitations and there is a reason why hyper-cars and super-cars are either AWD or RWD. There is just a limit to what you can load the front wheels with.

            The FWD chassis, mainly if you have a high torque engine, is better enjoined with LFB, that stand for Left Foot Braking. You can use Left Foot Braking in two ways, one to control the weight distribution, the other to tame down engine delivery and minimize wheel-spin... this is the case with the FWD chassis, is you are flooring it our of the corner and the burst of power makes the inner wheel spin... you can lift, tame, or use the left foot to try to tame the power and force it to the wheel with better traction. Some electronic differentials apply this principle.

            - RWD

            The front wheels are the ones steering the car, and the rear wheels responsible for passing the engine power to the ground. This simple fact means that, as physics are concerned, the system is much more stable. 

            Driving a car however means that you have to have a profound knowledge of physics, and the RWD platform, although more efficient, demands much more understanding of physics and it's conception than the FWD. It is... less forgiving, and as such, paradoxically, seen as less stable. 

            The problems are mainly 2. 

            1 - While cornering under acceleration, the front weight over the front wheels may unsettle the rear that, under torque from the engine, may brake-away more abruptly. 

            Not a friend of the rain, particularly with big engines and load shifts. Say, you are going around a bend and then you need to break... as you lift of the gas, load shifts to the front and unload the rear, as you then start to brake, the load shifts further, but the engine, (not decelerating) with it's compression may act as a handbrake and totally unsettle the chassis. This is why you should use the gear box ans heel and toe as you decelerate on a RWD machine. It may feel strange... using the gearbox to shift down may generate even more unsettling load on the rear wheels as the drive is lower and torque more influential... sure, but as you wheel and toe, you'll rev-match the gear to the engine rotation and that avoids the unsettling of the rear by matching rotation of the engine with rotation of the wheels. 

            2 - While accelerating, the rear end is the one transmitting the torque to the road, and as such will try to overtake the front of the car. Wheel spin requires precise steering input to be controlled. 

            Again, in this case for a different purpose, the left foot breaking may help brake into the corner and not allow the rear wheels to induce spin buy minimizing lift from the weight transfer, and the torque difference bu not decelerating abruptly.

                - FR

                Stands for Front Engined Rear Wheel Drive. 

            These cars, normally have a very comfortable steering feel as it's not too light,  like MR and RR models due to the engine weight over the front axle, but there is no torque steer, you have a much better feel. 

             The balance is more difficult to obtain as, having the heavy engine at one end of the car, the polar moment of inertia will be harder to control.

                - Front MR

                  Stands for Front mounted Mid Engined Rear Wheel Drive. 

                    Quite a pearl of a chassis. It is Rear Wheel drive, but the polar moment of inertia is handled by placing the engine in the front part of the car, but behind the front axle, making it as easy to control as is comes. 

                    This sort of chassis, generated a rotational tendency on the car. It means that it can rotate without generating difficult to control polar moment of inertia. It is very fun, but the fact that the car can turn easily means it can also do so while you don't expect it to so... requires much more experience to be driven... much more experience as in borderline racing experience. 

                - Rear MR

                Stands for Rear mounted Mid Engined Rear Wheel Drive

                    Another pearl of a chassis. Similar in feel and reactions as the Front MR, it's a VERY demanding chassis.

                - RR

                Stands for Rear mounted Rear Wheel Drive

                Only 2 cars I can remember are like this, and they are based out of the same design. The VW beetle platform and the Porsche 911. 

                It's a ginormous paradox! The engine in top of the rear drive-train means HUGE grip, and the steering is light as a feather... but overcome the grip limits, and the rear heavy thing will try to overtake AGGRESSIVELY.

                This nature has been solved over te years with TREMENDOUS amount of investment fro Porsche in electronics and vehicle control systems. Today's 911 is a masterpiece, not only because of it's rewarding drive experience but mainly because, the engine was in the worse possible position for managing polar moment of inertia, and they've managed to tame it. It is also 4wd and not just RWD, but you can get the Carrera 2 versions.

                But remove the electronics and you get a car with 60% of its weight at the back, a lot of engine and power... and a gasoline tank at the front that started to get lighter and lighter as you drive along, offloading the bias even more to the rear. That's why it was called, the widow maker.

                Not a car for my engineering brain, for sure, but place a true excellent driver at the wheel and you get some spectacular drifts at brutal speeds:

            - 4wd

            Stands for 4 Wheel Drive. 

    

            Regularly confused with AWD, the 4wd system is a mechanical linkage between the front and rear axles that it always coupled. There will be 2 differentials (3 on more sophisticated systems), depending on the sophistication of the system, but the coupling is mechanical and the torque is divided depending on the type of differential used. 

            A lot of the implementations of 4WD systems implement the torsen torque sensing differential, that will lock if it senses on of it's splits is slipping.

            - AWD

            Stands for All Wheel Drive and it is not a necessarily a 4WD system.

            What do I mean by this? Well the electronics and differentials make the difference. 

            On an AWD machine, the differentials are not torsen. They are Electronically controlled Limited Slip Differentials that can choose the drive-train to send power to, and then the wheel to send power to. The All Wheel drive stands for, any one of the wheels is able to get torque in different levels. 

            So why "not necessarily a 4wd" system. If you look at Xdrive from BMW, it will have a minimum 70% rear and 30% front bias setting, meaning that there will always be power to the 2 axles and then they split between them, meaning that, bare minimum you get 35% torque to each rear wheel plus 15% to each front wheel. This means that it is 4WD. But if you look at a Volvo Haldex, the front train will have the full torque and the rear will only get coupled if the front loses grip, meaning that it is a AWD system but not a 4WD as there are times where there is no torque being sent to the rear wheels.

            The world of AWD is spectacular as, the electronics, can be made clever enough to perform the so called toque biasing features and help the car corner better (say like the focus RS) or drift perfectly (say like the Mitsubushi Lancer Evolution and the Focus RS).

        - Implementations

        As you would expect by now, the type is not were it ends. There are ways to implement the drive train design and these go into 2 categories.

            - Rigid Axles

            Rigid Axles are the oldest design. 

            Rear axles are a cheap way to build and require less maintenance. They also are preferred if you are talking about big power numbers. So cheap and big numbers, meant that 90% of american muscle cars will have Rigid axles and 99% of offroaders too. 

            The problem with rigid axles is that they generate a dependent suspension design, that at the very best can be twisted into a semi-dependent design. 

            - Independent semi-Axles

            The best design IMO and allow you to have an independent suspension. 

                Noticeably more complex than the solid axle, but do understand that most of the complexity comes form the freedom to design a better suspension.

The "feel":

Finally we get to the point where all things combine into what you actually feel behind the wheel.

Let's try to categorize the chassis as an experience.

The Comfortable Chassis

Gonna say it right out :  NOT my thing! In my book, the comfort is in your living room sofa and not around a bend on a twisty road, so whenever I see people drooling about some Mercedes that weights 2 tonnes because it has electric motors to massage your back while driving I just make a tremendously caustic comment in my mind, and move away in hopes that it doesn't surge out of my mouth while I'm making my run out of audible range.

The comfortable chassis is normally a BAD dynamic chassis. Why? well normally it is part of the design of a luxury or family car, and this means that it will have items that, dynamically speaking are pointless. You do not need luggage space to drive fast, you do not need the heated seats, infotainment systems for the kids or any of those things to drive fast... they's just weight! 

So being biased towards those, it is heavy by design, being heavy also add inertia to the movement and if it is bad while cornering, it is not really that bad while going over a lump in the pavement, as the weight of the inertia works towards comfort and works the suspension harder than in a light car.

It's like flying on a airbus 320 and a 380... go over an down draft on the 320 and your stomach glues to t your lungs... but in the enormously heavy 380, you just feel light for a bit and than that's it!

This is the grounds of most Marcedes, Volvos, Audis and top lines from other brands. I left BMW out and Volvo in for one reason. Volvo no longer builds sporty models and BMW never stopped trying to have the driver happy about driving their cars.

These sort of chassis will make you feel relaxed in your driving. If powerful, normally the electronics are tweaked to produce a smooth power delivery. First because no one buys a limousine to escape from the police, except maybe Robert DeNiro and Jean Renault... but still they are exceptions. Second because it will not be a trust building moment, as you feel all that weight jumping around the soft suspension.

Of course, independently of how competent they tune the handling, you will feel it negotiating the tremendous inertia during corners, something that should be VERY noticeable on a weight transference on an S curve. 

The comfort will mean that, not only there is weight and filters, all round those will go all the way to the commands. Turn the wheel slightly and there is little to no reaction... add 1mm of throttle and ... no reaction... everything is totally filtered out and this makes the driving experience disconnected. 

If you want a perfect example of this, drive a P80 based V70 mk1 Volvo ... comfy but not too much. Then drive the P2 based mk2 V70... it will feel like you steer and then the orders are communicated to the chassis by voice and then someone steers the drive train. Comfort was pushed too far IMO. Then drive the P3 based V60 and you'll find a less comfortable but much more dynamic car... since the P3 platform is based on the Ford Mondeo platform.

The Bad chassis

Ever driven a car that is not competent, not comfortable... just plain cheap? Dull? Frustratingly stupid?

Those are the bad ones. 

One of the worse I've had was the Audi A3... yes the same crap that audi TT's where made from... and people payed good money for it.

I hated the thing. Steering was filtered, it under-steered like mad, and if you left'foot brake it will safemode the engine and remove ALL POWER till it decides it's ok to bring it back. Mental! You you really provoked it with ESP off, using the hand brake, it would bring the ESP back on.. I mean not only it's not good, it thinks it knows more than your!

The only good thing was that it was based out of the Golf chassis and the Seat Leon chassis, so if you request it to be setup as a Leon, and then over fill the rear tires, the under-steering is ALMOST gone. But man... worse spent money in cars I've ever had.

Ever tried a Mercedes SLK? Don't! Get a Megane Mk2 SW and it will go around corners better than that thing, and with more confidence and feedback... for pennies compared to it!

Oh and the Chrysler crossfire, manages to be worse. Same chassis as the SLK, but with heavier engine, heavier interior... hopeless.

The Welcoming Chassis

This is the sort of chassis that, right up front, will tell you how things are, and make you feel welcome driving it. 

Typically a chassis that will feel solid, transmit orders from the pavement and to the wheels with a good feel, without entering the discomfort zone. 

Get into a Megane, or a Focus, or an Civic EP3 or EP4, a Fiesta, and you will immediately feel that the chassis is firm but not uncomfortable, competent and informant of the limits ahead, giving you quite the confidence to explore the limits.

You will feel right integrated to the car and while it feels sporty, you do not have to wrestle it to go fast. You can go for a drive on a Broad, and feel right relaxed while having fun. One of those chassis that can make you smile without the occasional "oh shit" that compresses your sphincter.

The Sports Chassis

Things here start diverting. There are lots of sporty chassis around. But you can't really classify them in the same sub categories... so let's branch.

    The Fun Teacher

    Remember those teachers that where really cool and loved to teach, but then when things got real, would sit besides you and guide you through the problem out into the solution? That guy... That is the sort of chassis you'll find on an ST fiesta or a Ford Puma (MK1.... forget about the suv nonsense).

    It's firm, it's light, it's fast and then it will give you loads of confidence to abuse... however, there will come a time where you really go sideways and all seams lost.. and then, the chassis will maintain neutrality, allow you to counter-steer ad step on the gas full throttle... drift out of it and get back to line without countering the inertial or going side to side while dissipating the damping force.

    That lightness together with excellent balance will get you through.

    You will learn, and you may not crash while doing so, as long as you don't go trying tricks in the middle of town whee you have no where to go if things go wrong.

    The MILF Teacher 

    I don't know if all students had a MILF teacher, but I've had my happy young times. You know that teacher that is way older than you, but she is sexy, and the knows it, she dresses like she knows it and loves to tease their students. You know you shouldn't, as much as you know you want to.

    Welcome to the MX5, the GT86, the Lexus ls200, Front Engined Rear Wheel drive cars... 

    ...with rear wheel drive but rear tires as thin as the front ones, you know it's going to get sideways and it will happen on the first date!

    The problem with the MILF teacher? Any one of these chassis will know more than you and expand your concepts of driving over the limit with confidence and trust... but the MILF has a husband, and he had a shotgun. Overcook the driving and the linearity that would let you go sideways while maintaining the trajectory will turn into a no grip spin.... Get it in too hot and the husband will find out and shoot back. 

    The Karate Teacher

    The picture of efficiency. The razor sharp, non compromise, perfectly efficient chassis. 

    Get into a Megane RS on a racetrack. You'll get into a Karate teacher. It will expand your limits like you've never thought possible, while making the life of a "Ferari" 355 miserable.

    It will allow you to enter the corner way to fast, and mess up the exit but still on the track, and then went you get it right it will put a smile on your face.  That car has one problem and one alone... the engine. A chassis like that deserved an NA screamer. Put a K24 on ethanol pushing 400 NA HP at 11.000 rpm on that chassis and no one will be able to get you on the track. Some people may say there are 2 problems with that car... the engine and the rear suspension.

    You see, Renault Sport changed the front suspension design unto quite a masterpiece, but then the rear... well the rear is this:

Yup that's a torsion beam. 

    Why? I don't think they where trying to save cost. I believe they just focused on the road handling to the road to handle on, and built a trackday car.

    Evidently, if you take an MRS over a road like this:

You'll be begging for a EP3 civic, or a FordFocus with:

Independent rear suspension! CLEAR!

    But I disagree from the 2 issues on that car... You see you need to think of it like the Karate Teacher... it was built for the track. For smooth tarmac. Not the bumpy B road. Don't expect the Karate teacher to also Ballet!!!!

    And this get's us back to the PUMA. Remember back when explaining chassis designs when I talked that while transforming the PUMA, Ford did not change the rear suspension on the upgrade of the Puma to the Racing Puma, but they did so in the Rally S1400 and S1600 versions. So let's think about this for a minute or two. The BODY of the Ford Racing Puma is the same as the S1400 and S1600, it would be logic to just separate the production into consumer / racing and use the racing line to product the FRP. 

    But if you think of this for a bit, the FRP was sold in England alone, and it's a 500 units limited edition. It will run on English roads. So they created it with parts from the standard model, lowering maintenance and production cost, and just tweaked the body for better road holding and stance.

    But the S1400 and S1600 would have to go an all sorts of terrain, so the result was a much more expensive but crucially independent rear suspension system.

    So why doesn't the Karate teacher also do Ballet? Well... This, really:

 the torsion beam axle

the torsion beam going over a bump on the left wheel

the torsion beam compressed position in comparison

    You may say... so what? seams like the torsion part on the torsion beam worked and the wheel did move independent form the other!!! Sure-thing but then look at it from the back:

    As one wheel goes up, the torsion beam changes the camber on the other wheel, disturbing the road holding capacity from the bump and the changes in camber on the only holding wheel.

    And the you say: So why not increasing the torsional rigidity on the bar... 

well both wheels would jump when compressed and the car would hoop... not good mid bend!.. just not!

    The Stilgar

    Ever seen the Dune Movies? the new ones... brilliant and highly recommended, but still, Stilgar is the Fremen warrior trying to train Paul Atreides on the ways of the Fremen warriors. Part of that training is to master riding the Shack-Hulud (the ginormous worms that destroy everything). And Stilgar says: "Well noe you must ride Shack-Hulus and he will determine if you are ready.... or you die!"

    Well come the the Toyota MR2, the NSX and the Honda S2000. The Silgars!

    There is an enormous set of skills for you to learn from them and your driving limits will expand to universes you didn't comprehend until experimented... but it's a Stilgar sort of thing... you will learn or you will die. Simple!

    In the case of the S2000 chassis, it tweaked to become full racing, this is even more clear. The need to control every aspect of the car dynamics is crucial to avoid it running wild on the worse possible moment. These where cars tuned by professionals and expect professional inputs on both throttle and steering. Take a look at Senna driving the NSX or GanSan or Keiichi Tsuchiya driving the S2000 and it will become clear.

   

    And that is the ways of the Stilgar. 

Hope you enjoyed this. See you soon