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2016 Mitsubishi Lancer Evolution Final Edition – technical analysis

24 Dec 2015

Robert Pepper 4

The 2016 Mitsubishi Lancer Evolution Final Edition is not just a fast car, it’s a quick car. Here’s our technical analysis of how it all works.

THE GARDEN VARIETY Mitsubishi Lancer will cost you $24,000, or so, plus onroads.  The Lancer Evolution is more than double the price with an ask of $53,000 plus onroads.  To the casual observer, that seems ludicrous for a few extra cosmetic touches such as a wing, sports seats and flashy brakes, especially as the interior, styling and comfort features are not exactly market leading.

But to think like that is to entirely miss the point of the Evo, which is one of the few cars today that epitomises function over form, and that is why it has gathered a loyal fanbase over the last 23 years since its introduction in 1992. The powerful engine makes the car fast in a straight line, but there’s a raft of technology which makes it quick around the corners, too.

The secret to the Evo’s success is its drivetrain – all the gears and systems used to deliver power to the wheels.  It has always had one of the most technically sophisticated drivetrains on the market at any price range, never mind at its price point.  Not just sophisticated, but useful sophistication because there’s nothing on the Evo that doesn’t serve a purpose, and that purpose is speed with control. 

It’s a shame that Mitsubishi never really properly explained how all this wonderful tech works or used it to highlight their considerable engineering prowess, in contrast to lesser manufacturers who make much more noise about much less.  Even Mitsubishi’s names for the various systems are often confusing and uninspiring, but that doesn’t mean to say ineffective.  While the Evo will now die, Mitsubishi told us that the technology will live on in future vehicles, probably a sporting SUV.  We hope so.

The driver need not know very much about the systems, but as with any performance driving you’ll do better if you truly understand how the car works so you can drive with the systems, not against them.  If that’s what you want, then read on.

Read our roadtest of the 2016 Final Edition Lancer Evolution.

S-AWC – Super All Wheel Control

S-AWC is an umbrella term for a variety of systems that make up an all-wheel-drive driveline. The components are:

• Active Centre Differential (ACD)
• Active Yaw Control (AYC)
• Active Stability Control (ASC)
• Sports ABS (anti-lock braking system)

and each are explained below.

ACD – Active Centre Differential

When any car turns a corner the front axle travels faster than the rear, because the front describes a greater radius.  This causes a problem for an all-wheel-drive (AWD) vehicle which drives all four wheels, because then the front axle has to be driven at a different speed to the rear.

The solution is a centre differential, a mechanical device which allows two driveshafts to be driven at different speeds, in this case the front axle and rear axle.  Differentials are also used on (as opposed to between) the front and rear axles and there they allow the left and right wheels on that axle to turn at different speeds around a corner, yet still be driven.

So far so good, but differentials have a big problem, and to illustrate it we’ll use this photo from our review of the 2015 Triton:

The right front wheel is spinning, and the left front is not rotating.  That’s because differentials are ‘lazy’ – they send drive to the wheel that’s easiest to turn, and that’s true whether the differential is between two wheels on an axle (as per the Triton above) or between front and rear axles.

This is no good for 4X4s, and it’s no good for performance cars either.  Let’s say you have an all-wheel-drive car and you’re going to launch hard off the line – you’ll get a weight transfer to the rear, the front wheels will become light which means a reduction in grip, so they’ll become easier to turn and you might end up spinning the fronts while the rears don’t do very much at all.

So the Evo’s centre differential has a set of clutch packs which can let the differential be completely open, where it drives both front and rear axles equally, and the car is easy to turn but is prone to spinning up one axle in favour of the other.  Or the differential can fully lock where it forces the front and rear axle to turn at the same speed which means you won’t get excessive wheelspin on both front tyres or both rears, but you then can’t really turn a corner because you need the front and rear axles to rotate at different speeds.

The centre differential’s clutch packs are computer-controlled and can go anywhere from fully open to fully locked, depending on what needs to happen.  The computers decide how much to lock by processing a vast stream of data from a variety of sensors – the speed of each wheel, the yaw of the vehicle (rotation around an imaginary pole stuck in the centre), speed, throttle position, steering wheel angle, gear selection, brake position and so on.   For example, if the vehicle is accelerating hard the ACD will start to lock up.  If on the other hand you’re performing a tight turn in a carpark (well, the Evo doesn’t do tight turns but tight by its standards) then the differential will be fully open.

The diagram below shows the ACD display:

The centre rectangle shows the amount of lock.  One bar as shown is unlocked, and the more bars you have the more it locks.  The circular sub-displays to the side of the rectangle are for the AYC (explained below), showing how much torque is going to the left or right wheels.  Below is an image from an older version of S-AWC showing the ACD mostly locked, and the AYC helping the car turn right by sending extra torque to the left wheel and less to the right:

The clutch lock mechanism on the ACD is, according to Mitsubishi, capable of generating three times the force of an older viscous coupling system.  That means the front and rear axles are pretty much completely locked, therefore able to deliver more traction when needed.

Some other points about the ACD:

• the torque split is a nominal 50/50 front/rear, which means that’s the default.  That will change depending on how the differential locks up.
• This is NOT an on-demand all-wheel-drive system such as you find in the Outlander and other softroaders where the front wheels are driven and the rears then come in as and when the computers decide.   Those systems have their place, but in my opinion are completely wrong in a performance vehicle. 
• The tarmac/snow/gravel mode is explained below, and that doesn’t vary the nominal torque split, just the propensity to lock up.
• If you pull the parkbrake on the ACD unlocks to become an open differential.  This is because the Evo’s parkbrake operates on the rear wheels – as it should – and if you stop the rear wheels rotating with the ACD locked then in effect you stop all four wheels rotating.  That would not be great for parkbrake turns and will damage the drivetrain.
• The ACD can and will lock under braking to help stability – the reason for this is engine braking and ability to rotate the car under brakes.  It is said that all-wheel-drive is of no help when slowing down…not true if you engine brake, and it also helps with brakeforce distribution.
• The ACD was first used on the Japanese-market Evolution VII model.

Helical front limited slip differential

At the front we have another differential between the two front wheels.  This suffers from the same problem – laziness.  For example, corner hard and there’s not much weight on the inside wheels, so you might spin one up.  Not good for traction and therefore speed.

This is why the Evo has an LSD, or limited slip differential in the front.  There are various types of LSD but here we’re talking about a helical unit, which is a entirely mechanical device operating on gears, so no computer control at all.   No clutch pack either.

With this LSD, the more torque (turning force) that goes through the front diff, then the more it locks up.  So it’s not unlike the ACD, except it works on the front axle only between the front wheels, and it’s not computer controlled. 

LSDs can promote understeer because when you’re driving around a corner you do want the inside wheel to rotate slower than the outside wheel, but the helical unit doesn’t because as it locks up it directs torque to the outside wheel, helping the car turn.  In addition to that there’s cleverness happening on the back axle which also helps turn the car which we’ll get to next.

AYC – Active Yaw Control and Yaw control function

First we need to define yaw, which is the rotation of the car in a horizontal plane around an imaginary pole stuck in the middle.  Like this:

The other related concepts are pitch, which is fore/aft movement, and roll which is side-to-side. However AYC deals with yaw.

Now we get to the third and final differential, which is between the rear wheels.  Again we have the same problem; both wheels need to be driven at different speeds around a corner, but the differential will send drive to the one that is easier to turn.

So what we have here is a torque vectoring differential which Mitsubishi call Active Yaw Control.  This is extremely clever, because what it does is send more turning force (torque) to the wheel that needs it in order to turn the car (vectoring).   So let’s say you’re turning left…the right rear wheel will get more torque which has the effect of helping turn the car.  An extreme version of this is skid steer in tracked vehicles where the outside track is powered and the inside one is not, rotating the vehicle.

The AYC works in two ways – by having another set of clutches which vary the torque left and right across the axle, and also by individually braking each rear wheel.  Again, the decision about how much torque to send to which axle is made by the computers using the information relayed by all the sensors across the vehicle.

Here’s a diagram from Mitsubishi that helps explain the ACD and AYC:

It is important to understand that the AYC is much more effective than pure brake-based traction control or torque vectoring systems which apply individual brakes to wheels, slowing a wheel rather than driving it.

The brake-based part of AYC can be disabled (explained below).

AYC was first introduced in the 1996 Evo IV.  The current system differs from the earlier ones by use of the additional braking mode and control via a computer which makes decisions based on the sensor input described above, especially yaw rate.

Left-right differential limiting function (brake traction control)

Mitsubishi sure know how to come up with names that are catchy and descriptive.  As the saying goes, they’d probably call sushi “Cold Dead Fish”.   Anyway, this is just brake traction control.  We have a complete explanation of traction control vs stability control, but briefly – if a wheel on an axle spins up, this system notices the wheelspin and applies the brakes individually to just that spinning wheel, which has the effect of providing more drive to the wheel on the opposite axle.  If that sounds like another solution to the differential problem then you would be correct, it is.  You might also be wondering how or why you need brake traction control when you have AYC and a helical front LSD, and the answer is that the need for brake traction control to work is much reduced, but still necessary on occasion when you have 226kW of power, particularly on loose surfaces.  This traction control feature does not chop the throttle, it just brakes spinning wheels.  

ASC – active Stability control

Now we come to ASC, which is better known simply as electronic stability control.  This is a safety system that keeps the vehicle pointing where you want it to go, primarily taking that direction from the steering wheel angle.

The ASC computers take data from all the usual sensors described above, and detect whether the car is understeering (running wide, driver turns the steering wheel and the car ploughs on ahead) or oversteering, which is where the back end steps out and the turn over-tightens.  Here are photos of oversteer and understeer:

If either understeer or oversteer is detected then the ASC computers apply brakes to individual wheels to bring the car back into line.  For example, when turning left and understeering then the left (inside) brakes may be applied.  ASC does not permit oversteer or understeer.

ASC can also reduce the throttle if it decides there’s just too much power for the grip available, whether this is in a corner or a straight line.  This particular feature is also known as engine traction control, although that’s not a term Mitsubishi seem to use (too simple for them I expect).

Now you may be wondering about the difference between ASC (Active Stability Control) and Active Yaw Control. 

ASC is all about preventing the car from wheelspinning, slipping or skidding, keeping it on the path the driver intends, mostly directed by the steering wheel angle.

AYC is just about helping get power down to the ground as effectively as possible, and if that means wheelspin or sliding then so be it, and who cares where the steering wheel is pointed.

You can think of ASC as your mother, and AYC as your best mate who helps you do stupid things.

The diagram below is taken from our Pajero Sport technical analysis, and shows ASC and what Mitsubishi call on the Pajero Sport “Active Traction Control”, which is the same thing as Left-Right Differential Limiting Function on the Evo, the generic name for which is brake traction control.  Did I mention their naming convention needs some work?

ASC Button

The Evo has this button:

The button has two functions:

• One quick press – disables ASC (stability control) including engine traction control.  This is your mode for fast laptimes.  The brake control function of AYC remains active.
• Three-second press – as above, but also disables the brake-based part of AYC, leaving just the clutch-based torque vectoring part of it in operation. Or in other words, turns the electronic aids off with the exception of ABS and related braking systems such as EBD (see below).  This is your mode for drifting, as you want lots of wheelspin here. Active Yaw Control is still active because all that’s doing is helping you put power to the ground and it doesn’t care whether the car is driving straight or in a 90 degree drift under full throttle.  This is also your mode for track work.

The S-AWC modes

The Evo also has this button marked AWC:

which lets you select one of three modes:

• Tarmac
• Gravel
• Snow

This button controls how fast and how much the ACD locks up, particularly in response to steering input.  The order is as above, so Tarmac least lockup and quickest release when turning, Snow the most.  You can see the difference easily enough – accelerate hard from a standstill then brake hard in Tarmac and then Snow.  You will see that in Snow the ACD locks up much more than in Tarmac, and Gravel is somewhere in between.

The button does not modify the electronic programmes (ASC and related systems such as traction control).

Water spray switch

See the other switch next to the AWC button?  The AUTO MAN switch does this if you press the MAN:

This one sprays the intercooler with water.  An intercooler is a simple device somewhat like a radiator that cools air coming into the engine.  The cooler the air the more dense it is, and the denser it is the more you can stuff into a cylinder, and given a constant fuel/air ratio you can use more fuel.  More fuel means a bigger bang inside the cylinder which means…more power!  So intercoolers are Good Things.  However they get hot particularly with heat-soak in traffic, which is why there’s this switch which sprays water from the washer bottle to cool the intercooler.   You can spray it manually or set it to automatic.  We have a video on our Facebook page if you want to see it in action.

Brakes, calipers, Tyres and sports abs

The Evo runs asymmetric tyres with disc brakes and sports ABS.

Tyres

Asymmetric tyres are tyres that have a tread different on the inside of the tyre to the outside.  In the case of the Evo the tyres 245/40/18 Dunlop Sport SP600 – all that jargon is explained on our page about choosing a tyre.   The theory behind asymmetric tyres is that the outer edge of the tyre has a different load during cornering than the inside edge, hence different tread designs.  Often this difference is used to design a tyre for better wet performance on the inside part than the outside part.

Brakes

The brakes are disc brakes by Brembo, one of the best known and most respected names in brakes.  The brakes are much larger than those fitted to a standard Lancer because they have more work to do as the Evo is much quicker and is also heavier than a standard Lancer.

As you may recall, energy cannot be destroyed, only converted.  The Evo has a lot of energy when moving because it is a fast car, and if it needs to slow down that’s a lot of energy to convert to something else.  The job of the brakes is simple – convert kinetic energy (forward motion of the car) into heat.  That’s why the front discs are 350mm diameter and the rears 330mm, because the larger the disc, the more heat it can absorb and radiate, and for a performance car driven hard, brakes are everything, much more important than power.

These brakes are four piston at the front and two at the rear. Pistons push the brake pad onto the brake disc.  Large pads require more pistons, but the number of pistons is often incorrectly viewed as some sort of measure of quality.  It’s not, you can put the same force through four pistons as eight.

The front discs are cast iron solid, no holes, no slots, no dimples.  It is commonly believed that such features improve braking due to making the disc lighter or helping get rid of heat. To some extent both are true, but the tradeoff is a reduction in the ability of the disc to act as a heatsink so the gains, if any, are minimal.  Also, drilled holes when done poorly certainly reduce the strength of the disc.

The Evo’s front brake discs are two-piece which means there’s two discs with an air gap between, and cross-members to join the two discs.  This is done to help ventilate the disc.

ABS

Forged wheels

Lightness is good for cars because it’s like free performance – you accelerate quicker, stop faster, corner quicker.  Lightness is particularly good for wheels, because those rotate and rotating mass takes energy to rotate.  Also, wheels are what’s known as unsprung mass – part of the car that isn’t controlled by the suspension.

So, this is good:

See that little word “forged”?  It means the wheels are forged, ie. there’s a solid block of metal (usually some sort of aluminum alloy) and your wheel is carved out of it.

The alternative is cast, where molten metal is poured into a mould, allowed to cool and then you have your wheel.  There are a few different methods of casting such as gravity and pressure.

Forged wheels are stronger and lighter than cast wheels.  Which for a performance car is very good news. The Evo has forged wheels, because Mitsubishi decided to spend money on performance not on the interior.

Everybody who loves performance cars should now take a moment to say “we love you, Mitsubishi”.

This is very Evo by the way, all sorts of features which to the non-enthusiast mean nothing but are really very useful.

The Wing

Now this is pointless.  Either the wing is there to provide downforce, in which case understeer will ensue as there is no equivalent front wing, and even worse, the wing will create extra drag as it is not adjustable. There is no downforce without additional drag, specifically induced drag. 

Or maybe the wing is a spoiler to reduce lift, which is unlikely given the design and ineffective given the Evo is a 1570kg car that does its best work at relatively slow speeds on twisty tarmac so the few kilos of upforce it saves would translate to about a millisecond’s worth of laptime – every time a manufacturer makes some claim about a wing’s value I challenge them to prove it with laptimes or a graph of lateral G with/without, and get no response.  At least Mitsubishi make no such claim.  Anyway, you’d be better off saving the weight which is all in the wrong place, high up and a long way from the centre of gravity.

S-AWC Summary

Quite a lot of tech to understand on the Evo, so here’s a handy diagram to pull it all together, originally from a Mitsubishi technical document but modified a bit to make it up to date:

And here is a diagram that shows how it works around a corner.

This is a schema of how it all hangs together.  Yes, the ACD is at the front, but that doesn’t make it an on-demand AWD system.

Or you could just not worry about such things and drive the car.

We also have a technical review of the Evo’s primary competitor, the Subaru WRX STi.