Back to the 80's

Posted by Quinn Howling on

It's been a while since I wrote a post, so if you don't know, for the last year I've been operating as a full time performance driving instructor at a performance driving circuit. Although it's my job to teach others how to proficiently operate a car at a high pace, I too am constantly learning. I find most of my lessons are in understanding people and how to teach better. Some lessons are in how new cars are terrible, but today's lesson would be filed in the category of better understanding for my own driving. This is something I like. 
It was a slow day at the circuit, so on days like this, it's time to try things that scare me, or confuse me or challenge some common knowledge. Left foot braking is something I admit is not natural to me. A few of my co-instructors come from karting backgrounds. Karting requires you to use your left foot for braking, as the karts are structured for your left foot to actuate the brake pedal. Karts with transmissions are similar to motorcycle, or racing style, sequential transmissions that only require a clutch for starting from a stop and not for shifting. In these karts the pedals are the same as other carts, but with a hand clutch for starting the kart from a stop. This gives them a distinct advantage when learning left foot braking in a car. 
My hypothesis before starting, left foot braking allowed a better 'exchange of traction'. I was to test this with my introduction to it. If you're not familiar with 'traction exchange', it's a pretty simply concept in performance (grip) driving. If you're using 100% available traction for braking, then 0% is available for turning. By releasing the brake pedal, you open the opportunity to use traction for, cornering or acceleration. The transition between these uses of traction is the 'exchange of traction'. This is most applicable in Trail braking. Where you ride the brake pedal into the corner, as you begin to use traction for turning the car, you release the brake pedal equally: 25% turning traction, means 75% is left for braking. 90% turning traction is obvious 10% braking, etc. As you trail off the pressure of the brake, you can use more and more traction for turning. Thus trail braking. 
The problem with right foot braking, is you need to let off the brake entirely, before transitioning to the throttle. Resulting in a gap, or a moment where the car isn't accelerating. This creates a more jerky exchange of traction. So, the left foot is introduced. Most cars now, especially at my work, are automatic, or dual clutch, or even sequential, removing the need to use the left foot for the clutch pedal. This frees it up for left foot braking! 
By using the left foot for braking, you can lightly apply throttle as you release the brake. An ultimate exchange of traction. Trail braking into the apex, rolling onto the throttle lightly as you release the brake, results in an ultra smooth traction exchange. This is much easier said than done, and it took a good hour of laps for my left foot to really start to understand it. Consistency wasn't high, but eventually more often than not, I was able to exchange between the braking and accelerating state smoothly, sometimes without feeling the brake pedal release moment, which was nice, but also spooky. 
So why the title of the article? A big complaint of mine is that the general automotive public don't seem to notice that manufacturers are struggling at an extreme rate to deliver vehicles with better fuel mileage ratings. The efficiency of internal combustion gasoline engines, almost peaked decades ago. There are ways to get more complete, more efficient burn of the fuel, but consumers either can't afford the materials that would construct a motor that way, or they won't put up with the different feelings or interactions of these motors. The balance between the consumers expectations of interaction, their budgets, and the requirements of governing bodies, has led us to some creative solutions. There's two that I interacted with directly today. 
The first was pedal delay. A severe majority of vehicles now use electronic throttle pedals. Gone is the cable connection and now we're left with a pedal that communicates to an electric motor to open the throttle plate. This is a bit of a horse / cowboy problem, as it's something electronic controlling something mechanical, through the input of something organic. There's a lot of translation happening. This translation has a side affect: Delay. There is a delay from when the pedal is put down, to when the throttle plate opens. It's roughly the same delay time as it took you to read this sentence. What's interesting, is that this delay time is on purpose. Manufacturers realized, after years of trying to subtly suggest the customer improve their own efficiency of operation, they realized that to sell a car, they must promise brutal acceleration and great fuel economy. To deliver on both of these, they put in the gas pedal delay. It's an non-conscious question to the drivers foot "Do you actually wish to accelerate, or are you just being lazy, adjusting your foot, tapping to the beat of the music, or have an itchy toe?" This delay, smooths out the drivers inputs, and double checks that they wish to use the fuel to move the car. 
Your eco mode button isn't the computer moving into a more efficient tune. Rather, it's an increase in the delay of the pedal. Through testing at work, we found no significant difference in 3 different models of performance vehicles between race mode and comfort mode when doing lap times around our circuit. The performance of your foot to the floor was delivered the same by the engine. Rather, the annoyance of operating the car was increased in in comfort mode. The car was purely less responsive. It's the consumers fault they consume a lot of fuel, but you can't tell them. 
It can be surprising to think the motor doesn't change, but it would be less logical from the manufacturers perspective to deliver an inefficient mode that's selectable, and have CAFE standards tax them on it, or even worse, have consumers complain about poor economy. So the motors are set to the best economy and performance permanently, it's just some other things that change. The pedal delay, but most noticeably, the engine noise. Funny enough, this measured outside the car isn't noticeably louder, rather inside the car, they play the vehicles engine noise over the speakers to the occupants to inspire a higher performance feel. Giving you what you want, and DOT, CAFE and NHTSA, etc, what they want. 
The second way they deliver on these contrasting promises of performance and efficiency, is the turbo charger. Turbo's do not improve the fuel efficiency of an engine, but they do make you, as a driver, operate the car differently. Most turbo performance manufacturers and tuners have been working harder and harder since the 1980's to reduce turbo lag more and more. Turbo lag is a moment in the RPM range where a turbo isn't delivering extra power, rather it's briefly slowing the engine down until it can create enough pressure to improve the engines performance. This lag creates a motor that has a two part power band feeling. Before boost, you have a slow, stock feeling engine power, and once the lag is over, you have a sudden, new feeling of great power. 
There's some physics problems. Mostly to do with the metals the motor is made of, and the heat they can take. Consumers can't afford better quality, higher heat materials in their engines, so a certain amount of fuel must be mixed with a certain amount of air, to keep the temperatures inside the cylinder down. The more fuel mixed in with air, the cooler the engine burns. What this means is, when the turbo starts functioning, it's pushing more air in than the engine would draw on it's own. This greater amount of air, requires a greater amount of fuel. So the efficiency of operation is null at this point. More power means more air, and more air means more fuel. The mixture of the two is always balanced. 
If the turbo isn't making the engine more efficient, then why are manufacturers saying it does? 
When turbos became popular in the late 70's, early 80's, their understanding, humans grasp of making them work efficiently wasn't great. It was a new technology, and so these early turbo setups, although making great power, were extremely laggy. Huge moments of waiting until boost was delivered to the engine, this lag, from a performance driving perspective was fucking annoying. You'd wait, and often be surprised by a sudden power jump, often challenging your traction at that moment of surprise. Tuners and turbo manufacturers worked hard to try to adjust and improve this lag problem. Eventually automobile manufacturers returned to non-turbo models, and the rise of the V6 engine came in the late 80s, early 90s. Mechanical simplicity returned. 
Recently we went back to many cars using turbos. You'll even find big gasoline trucks using turbos again. There have been big improvements in turbos, intercoolers and injector systems, but nothing that is dramatically better on fuel. So why have they gone back to turbos, and their mechanical complexity? It's quite simple, to match their promises to the customers, to deliver big performance, with low fuel consumption. 
It's pretty crafty! Engineers have purposely added laggy turbo systems in order to fulfill their promise to the consumers. By adding a small engine than expectation, with a laggy turbo, not only can the manufacturer advertise a high power rating, and acceleration numbers, but they can also shut the turbo down during regular driving, and use far less air and fuel to move the car around normally. This results in lower fuel consumption numbers, and cheap CAFE taxes to the manufacturers. 
So what's this got to do with left foot braking and the 1980's? In the first age of the turbo, the late 70's and early 80's, performance cars relied heavily on big laggy turbos to produce huge power. However, in some scenarios the lag of the turbo, the engine being operated outside of boost, actually slowed the car down. The engine would be so slowed down by the turbo not operating in it's peak range, that the performance of the car suffered any moment the turbo wasn't spooled and in boost. This was a problem for drivers. They were expected and wanted to drive faster, so they too had to adapt. The best solution to this turbo lag for drivers, was to never let the motor drop out of boost. Keep the RPMs up! But slowing down for corners meant the engine needed to slow down too. To fix this, drivers would leave their foot on the gas pedal at all times, and slow the car down with their left foot on the brake. By left foot braking they were more likely to keep the engine in boost, and were able to accelerate with more available power, sooner, out of the corners. 
It was quite apparent, but an unexpected reminder of this, while practicing on our F80 generation M3. Operating it purposely in efficiency mode increase both the pedal and turbo delay, meaning I was able to practice overlapping the throttle and brake mid corner during an exchange of traction. It was neat to find that by giving the engine that extra half second, it was ready, and in boost to bring us out of the corners. It was nice to notice and learn something new today. Now if only I could get the chance to work on left foot steering..... 


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