RenaultSport: Technical Feature on Engine Mapping/Tyre Management

Spanish Grand Prix Technical Feature

I rarely post press releases in their entirety.  This feature from RenaultSport was so interesting I though it worth sharing with you all.

They’ve been the talking point of the season so far: Pirelli’s P Zero tyres. As the sole point of contact to the track, and thus the point through which an engine delivers its power to the circuit, tyre wear is of vital importance to Renault Sport F1’s engineers too.

And, as Renault Sport F1 Williams’ track engineer David Lamb divulges, its importance is something of which engine engineers are only too aware.

“For the first couple of races tyre wear really wasn’t so high, but in Shanghai and Bahrain the tyre wear was a lot more noticeable and became one of the key performance differentiators. The rears are generally the first to go because of the stress they are subjected to under braking and accelerating, so we immediately knew we could help in preserving the tyres.

“When a driver lifts off the throttle, the rears are unloaded, but when the power is reapplied, the forces going through the tyre are accentuated. This constant on-off pressure really increases the wear rate and if you lock the tyres under braking it doesn’t just cost lap time, it also heats the tyres up, which accelerates wear.

“The first thing you can do to reduce locking and improve the wear rate is to keep some torque from the engine when the driver lifts his foot off the pedal, so even when you’ve got zero percent input from the pedal you can still ask for some torque from the engine. This will be done in the way you map the engine. It squares up the rear of the car, stops it from locking and reduces the tyre wear as a result. It is actually still a negative torque because it is illegal to ask for a positive torque from the engine if the pedal is at zero percent. The driver will have probably three or four options available to him, dependant on in-race scenarios.”

The concept thus seems simple enough, but it will come as little surprise to learn that the benefits of utilising such a technique must be measured against its shortcomings.

“The big downside to this is that fuel consumption will, of course, go up: it increases incrementally depending on how much of a push you use. The fuel consumption increase can be as high as one or two percent per lap, so you’re looking at maybe an extra three kilos of fuel at the start of the race. The weight leads to slower lap times, to the tune of a few hundredths per lap. It’s an irony that you can use the push to help tyre wear but carrying the extra weight of the fuel to facilitate this push may have a negative impact on tyre wear!

A further disadvantage is that operating temperatures can increase: “As you are using the engine on overrun and therefore using it for longer over the lap, you are also looking at a slight increase in operating temperatures. Generally it shouldn’t be a problem in Barcelona, but in Bahrain where ambient temperatures were a lot higher we were on the edge.”

Firing on overrun is not the only tool available to Renault Sport F1’s engineers however. As David explains, throttle mapping has never been more crucial.

“The other factor in terms of tyre wear that is important to factor in is the use of pedal maps; that is, the percentage of pedal application in relation to percentage of torque being used.

“A crude example could be if a driver says, ‘OK, when the throttle is at 30 percent, I want 15 percent of the engine torque.’ A soft pedal map is when a driver has quite a bit of modulation initially, but correspondingly he will always have less progression at the higher throttle positions because 0% and 100% throttle position have to correspond to minimum and maximum engine torque (again as per the rules) – i.e. anything you take at the start to increase progression will be paid for with a loss of resolution at somepoint later on.

“This, of course, has a huge effect on the manner in which the tyres are used as we have to be very specific for each driver, from track to track and even corner to corner to ensure as little wheelspin as possible. As engineers, it is in this mapping that one of the more enjoyable challenges lies.

“There are, of course, limitations that have been placed upon pedal maps so that a version of traction control doesn’t edge its way back into the sport and the FIA is quite strict on how we use pedal maps, especially on launch procedure. But Fridays now see us working incredibly hard to make sure that we hone our pedal maps for each corner and for each driver to make sure that they are happy with throttle application and power output.”

Renault Sport F1 certainly seems to have got on top of the challenges presented by the new competitive face of Formula 1 in 2012, with the running order at the last race a clear sign of the progress made over the opening rounds of the championship.

“The Bahrain result was fabulous for everyone at Renault. To have the top four powered by Renault was a great result. It gave everyone a boost going into the Mugello test and now this race in Spain.”

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