Spool party: How F1's drivers will fight against turbo lag in Monaco

When you consider how hard a turbocharger works, it's amazing how reliable they are given the sheer rotational speeds and the pressure of compression. 

A quick crash course for those not entirely au fait with the workings of a turbocharger: you have a turbine and a compressor, connected by a shaft. The turbine is spun around by the transit of exhaust gases out of the car, which spins the compressor's impeller. Since the compressor is part of the intake system, it pressurises the airflow to increase the mass flow rate of air entering the intake system. 

By compressing the air, the turbo delivers more oxygen into the cylinders of the engine during the intake phase, allowing the fuel to burn more efficiently; thus, the engine delivers more mechanical work, increasing torque at low revs and power at the upper end.

But here's the thing: if the exhaust gases aren't flowing, then the turbine isn't spinning. If a driver is off-throttle through a corner, then the turbocharger slows down to decrease the boost pressure within the system. When the throttle is applied once again, it takes a couple of seconds - depending on the mass and, by association, inertia of the turbine - for everything to spin up to the maximum rotational speed once more. 

In that circumstance, the car lacks the torque it would otherwise have for acceleration, reducing the exit speeds of the car.

In the 1980s, turbo lag was a significant issue to overcome around Monaco in particular given the plethora of slow corners. It could still offer something of an advantage on the run to Massenet and, later, out of the tunnel, but didn't yield the dividends elsewhere on the circuit thanks to the spool-up time required.

Drivers had to fight turbo lag and manual gearboxes around Monaco in the 1980s

Photo by: Getty Images

This is where the naturally aspirated cars, especially those with small-bore, long-stroke pistons, could benefit as they were able to attain the peak torque sooner on the exit, particularly those running with flat-12s or V12s. Turning the turbo down, or running with a smaller unit, could offer some degree of performance here to turn the tide against the atmospheric machines.

Ferrari reconfigured its engine for the 1981 race to grasp more torque at lower revs, knowing that its turbo was particularly prone to lag, and Gilles Villeneuve demonstrated the efficacy of those changes by putting his car second on the grid with a lap just under a tenth shy of pole-sitter Nelson Piquet. Piquet's retirement, then the fuel vaporisation issues faced by Williams' Alan Jones, ensured Villeneuve could go on to triumph.

During this era, teams explored a multitude of ways to maintain torque on corner exits to mitigate the effect of turbo lag. Renault, for example, played with electronic fuel injection to get more mechanical work out of the internal combustion engine out of corners. 

As electronics became more ubiquitous over the generation of cars, the throttle response could be improved incrementally; the turbos still took a long time to fire up to full speed, but the gap in power delivery had long since been smoothed over. Opting for two smaller turbos proved to be the best way to overcome the limitations of forced induction in Monaco.

When turbos were reintroduced in 2014, lag was no problem; the MGU-H could get the turbocharger up to full revs, and so the driver could expect the full boost almost instantly under acceleration. 

Now without the MGU-H, deleted from the current regs for being too much of an expensive and expendable luxury, the drivers will have to face the challenge of turbo lag once again in Monaco. 

Ferrari's smaller turbo is expected to be of some help here, but the drivers will also have to do their part in maintaining the turbo speeds through the lap. This, rather than energy management, is expected to be one of the main focus points for the drivers through the grand prix weekend.

The previous turbo-hybrid cars had no such issues with turbo lag, thanks to the MGU-H

Photo by: Glenn Dunbar / Motorsport Images

"In terms of the power unit, I don't think it should be particularly complicated," Oscar Piastri explained. "At certain points, you're still going to struggle with the turbo and boost pressure, and gear usage is still going to be an important thing, most likely, for everybody, but it shouldn't be more than that, really. We should have full power everywhere.

"We all know these turbos take an incredible amount of time to spool up, some quicker than others, essentially sometimes if you're at full electrical power, when you lose boost pressure, you don't have the power from the combustion engine, so you lose a lot of power from there, which is definitely one of Ferrari's strengths. 

"They don't have to be as critical on managing that, because they lose less power if they lose boost pressure in the turbo, so that's still going to be a thing to manage around here, which shouldn't be too difficult. You might see first gear a lot, but I don't think it will be a huge departure from what it's been previously."

Drivers experimented with dropping into first gear during the Bahrain tests in pre-season, particularly into the first corner and Turn 10 (the tight, off-camber left hander), to keep engine speeds up. The mass flow rate of air out of the exhaust system is contingent on the engine speeds; if the crankshaft is turning slower, then the exhaust phase of the combustion cycle does not happen as often.

In recent years, drivers have only used first gear through the Fairmont Hairpin, and have stayed in second through the Nouvelle Chicane and the Rascasse. Expect these corners to be taken in first gear this year to keep the turbo spooled, and second-gear use for Mirabeau and the second half of La Piscine for a similar effect. 

At least they don't have to worry about H-pattern gearboxes this time, which made Monaco particularly spectacular in the 1980s...