INSIGHTS

  • THE POWER OF STREET CIRCUITS

Report

15 September 2018

When drivers are training for a new Formula 1 season, the Singapore Grand Prix is at the forefront of their mind. The fitness level required to complete the night race is the highest of the year, so if you’re fit enough to race here for two hours solid, you're fit enough to race anywhere.

But it’s not just the drivers who are greeted with a unique challenge in Singapore, because the Marina Bay Street Circuit provides a number of specific tests of a power unit.

01

After Friday’s practice sessions were complete, power unit engineer Chris Wright explained just what he has to focus on to extract maximum performance around the city streets.

“The hardest aspect is from a temperature point of view,” Wright says. “The straights are not particularly long. From an energy point of view it’s actually quite good here and quite easy to deal with in terms of pure energy management.

“But what’s not easy to deal with is when you’ve got such a complicated strategy that we’ve got in the ECU, so many switch options, the drivers have only got little short straights to get it done, so we try not to overload them with too many switch changes here.

“So part of my job in the background is to work out what we’re going to need and try to combine switches so that we can just make one change which does everything we need. If we ask the driver to make many changes there is a chance he can mess up his lap, or won’t be in the right position with traffic, because he’s been concentrating on the steering wheel… It has a big effect here.

“That’s actually one of my highest priorities for this circuit, to make the operation of our PU as simple as possible for the driver.”

02

Even when the sun sets for FP2, qualifying and the race, air temperature rarely dips below the high-20s Celsius, with humidity levels remaining high. It is those conditions that affect the power unit in a number of different ways, pushing specific aspects to the limit.

“The ambient conditions that we’re talking about - which is relative humidity, air temperature and ambient pressure - all affect how hard the compressor has to work to meet the boost target.

“Also the higher temperatures here mean that we end up running higher plenum temperatures, so then the boost target gets higher to get the right amount of air into the engine, just because it’s less dense. So you have to do more work with the compressor to get the right amount of air into the engine.

“So it affects the compressor, and it affects us in terms of knock as well - irregular timing of the combustion - and how much ignition you can put into the engine, so we’re constantly monitoring that. That’s the same as any circuit, it’s just that here, because it’s so hot and sticky the plenum temperatures are quite high, so it’s noticeable that we’re spinning the compressor a bit faster.

“The power unit is designed for it but we’re on the top limit, basically. But if you’re not on the top limit in Singapore then you’ve maybe got it wrong!”

The obvious way of dealing with high temperatures is to open up the bodywork in order to increase cooling, and at a circuit where the car is run in a high downforce specification - with already high drag - you might imagine that’s an easy solution. But as Wright points out, when already running high levels of cooling, the impact is greater with further increases.

“It’s just partly down to the circuit layout and the ambient temperatures that cooling is a challenge here. We could easily open up the bodywork and get the car cool enough, but the drag penalty is actually high here. So you get a lot of pressure from the team to run it as tight as possible because there’s quite a bit of lap time in it. Whereas at some circuits you can open up and it doesn’t really hurt you on lap time.

03

“It’s just where you are on the cooling specification. The bigger the change, the more the lap time penalty is. So if you just do a little, tiny opening or a tiny change to the cooling, chances are you can reduce your temperatures and actually not have a massive impact on lap times. But when you're at hotter ambients you’re on your bigger bodywork and then the next step is even bigger, so the lap time penalty is larger.

“So circuits like this where it’s hot - Malaysia used to be the same - you get a lot more pressure to be right on the top limits on the PU temperatures just because the next step on bodywork is a bit of a penalty. It’s not linear.”

There are even further considerations to take into account when it comes to how smooth - or otherwise - the track surface is. A street circuit is traditionally more bumpy than a permanent track, which can result in moments when the rear wheels are not in contact with the asphalt, and that shows up in telemetry.

“We get a bit more limiter activity here. That could be a reliability issue but it’s not really for us as our limiter is working quite well. Whenever you’re on the limiter you’re not going forwards so it’s not ideal. There are a couple of bumps around here that are causing that kind of thing.

“If you just see something odd in the data and you haven’t noticed that there’s been a bump in the track then it’s something to look out for. Sometimes you end up chasing yourself looking at the data thinking ‘What’s happened here? Why has there been a torque cut?’ and actually it has come from the limiter because you’ve just gone over a bump.

“I’ve seen one or two bumps today in the data, so compared to a normal circuit it’s definitely bumpier.”

04

The Marina Bay Street Circuit features the highest number of corners of any venue on the F1 calendar, which makes drivability crucial as there are a number of occasions the car is exiting a low-speed corner. If drivability isn’t good then it can also impact on rear tyre life, increasing the impact on lap time. But Singapore is not all bad news for a power unit engineer…

“The power unit has to detect where it is on circuit and that detection is based on where the driver lifts off into a corner. Luckily most of the corners here are full lifts, so it’s easy to detect the changes. But at other circuits where in qualifying a corner might go from being a lift in practice to flat in qualifying then you face the risk of the detection not working properly. Here it’s not a risk because it’s such a stop-start type of track it’s really easy to detect where we are on circuit.

“So that’s not too bad here but there are a lot of corners and it means the energy management is slightly more complicated just because there are more areas on the circuit you can use energy. There are more what we call segments - more straights basically - so energy you decide you want to deploy on one straight you can take from one of many others.

“Normally you might do that juggling of your deployment between just three different straights at one circuit, for example, as they are the only places you would spend energy. But here there are so many straights you can take a little bit from a couple and deploy it on a specific one if it’s driver preference. But we tend to do mostly simulation-based work, find the optimal lap time deployment strategy and then apply that. Our drivers normally seem quite happy with that.”

05

At least that’s one less thing for a driver to worry about at the toughest race of the year. Singapore gives nobody an easy ride.

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