Balance of Performance (BoP) changes in GT3 and GTE racing have become a topic for discussion almost every week, with series organisers across the globe constantly monitoring and altering the performance levels of GT cars to encourage parity and fairness.

BoP though is a cyclical game of give and take, which when done well results in excellent racing between a wide variety of cars. When it isn’t so good, however, it can lead to dominant displays by certain teams or machines on a given weekend.

At its core, BoP is a process that can never be perfect, simply because there is an endless number of variables affecting each car in question. Things like driver ability, circuit, weather, air pressure, temperature, they all factor in.

Despite all that though, organisations like the ACO, SRO and IMSA all remain committed to calculating the changes needed to ensure that competition is as fair as possible and exciting for those involved and watching throughout each season.

But what exactly do these constant changes actually mean? What effects do the alterations to the cars have? And what can those of us who are not as well versed in the engineering side of GT racing as the people actually driving and preparing the cars take from each change?

We all know BoP is important, but not many know exactly how it works and how the changes affect the cars. There are things we say with confidence, that when we actually think about, we know rather less than we would be comfortable to admit to ourselves.

In the era of GT3, with big grids and huge variety, Balance of Performance is absolutely key. This feature is not designed to address the moral questions inherent in the process, nor to judge between the varied systems in use, but merely to provide some form of data-led factual basis for our understanding of the net effects of the measures imposed in the process, and for our future conclusions.

We’re disappointed we didn’t do it earlier, others might be disappointed they didn’t do it first!

With that in mind, DSC’s deputy editor visited Base Performance Simulators for a day with pro drivers, Seb Morris and Craig Dolby, to run a series of tests on its GT simulator.

A methodical approach

During the afternoon, both drivers completed multiple five-lap runs around the full Silverstone circuit, with two cars: one front-engined GT3 car, and one mid-engined GT3 car, both white-label.

Both Morris and Dolby drove each car with no adjustments, then with 30kg of ballast added, and then with a reduction of 30bhp to simulate an alteration to the restrictor or turbo.

By doing this, we were able to get a feel for how two different types of car handled the changes, how it affected the raw lap times, as well as how two drivers of different levels of experience adapted to them.

The results were incredibly enlightening to this writer, who after sitting down with both Morris and Dolby, as well as Base Performance’s knowledgeable staff, felt far more in tune with just how much of an effect, or how little, the changes can make to certain cars.

We can say with confidence now that there’s far more to BoP than “just add 50kg to slow the car down by a second a lap”.

Times they are a changin’

The fact that the times differed when the cars were tampered with wasn’t such a surprise, but how and why they did was.

After plenty of running on the cars in their standard form, both Morris and Craig were within seven tenths of each other in the front-engined car, and under two tenths from each other in the mid-engined car before looking at the data and starting their next runs. The key is driving style, but we’ll come to that later.

When Dolby did his run in Car A (front-engined) with ballast, his lap time was increased from a 2:01.619 by just over four tenths to 2:02.056. And with 30bhp less, the time was a 2:02.254, a difference of six tenths.

Car A (front-engined) Craig Dolby Seb Morris No adjustment 2:01.619 2:00.947 +30kg 2:02.056 2:01.512 -30bhp 2:02.254 2:02.722

“You can definitely feel the difference weight-wise. It felt so sluggish, you end up over-driving the car and use the brakes more,” Dolby said after his run with the ballast.

“Yeah and you have to adapt quickly,” Morris added. “When you put a lot of ballast in a front-engined car it’s like being in slow motion.”

When it’s got no weight, it’s like driving a qualifying lap with low fuel Craig Dolby

“At Maggots and Becketts, you have to leave that bit of extra time for the car to arrive and move around. When it’s got no weight, it’s like driving a qualifying lap with low fuel,” replied Dolby. “It would affect a GTE car more than a GT3, too, because you’d have to do it without ABS to slow the car down easier. A lot of us don’t need the ABS, we rarely use it if you look at the data. It’s there if you really need it, it’s a get-out-of-jail card.”

And then with the reduction in power, Dolby explained that the car felt better through the corners, but was tough to manipulate on the exit of corners and down straights.

Morris’ results turned out slightly different. His best lap with no changes in Car A was a 2:00.947, with 30kg added was a 2:02.751 and with 30 less horsepower was a 2:02.722. It shows that the difference between the times aren’t solely based on the BoP changes, but on the way that drivers react to them. This year Morris has driven a front-engined car predominantly, and therefore has a lot of experience with varying BoP.

Car B, which was mid-engined, saw Dolby set a 2:01.400 with no alterations, 2:01.521 with ballast and a 2:02.575 with fewer ponies. Morris, meanwhile, set a 2:01.259 in standard trim, a 2:01.813 with weight added and a 2:02.233 with a reduction in power.

Car B (mid-engined) Craig Dolby Seb Morris No adjustment 2:01.400 2:01.259 +30kg 2:01.521 2:01.813 -30bhp 2:02.575 2:02.233

“I thought that the weight in the mid-engined car didn’t make too much difference,” admitted Morris. “It felt a tiny bit more lethargic, with a bit more understeer, but I could put the power down earlier on the exit. Then with the power difference, it didn’t feel as big of a difference as it was in the front-engined car. You could tell it was there, but because the traction was so good, you could go full power straight away out of the corners.”

I too noticed that the weight in the mid-engined car didn’t affect the balance. If anything, it helped having weight on the front. Craig Dolby

“I too noticed that the weight in the mid-engined car didn’t affect the balance,” Dolby reiterated. “If anything, it helped having weight on the front. It was easier to drive than the front-engined with weight, and over a long run would therefore look after its tyres better.”

The big takeaway? The mid-engined GT3 car suffered more with less power than the front-engined in terms of lap time, but the car seemed easier to drive. It shows just how much a BoP change can differ from car to car.

In an overall sense, there can be a real difference in how certain cars react to similar weight/turbo restrictor changes, which can make for a big difference in performance and lap times.

More variety, more problems…

“The main issue is when they bring out a new car,” said Morris. “They’re never on top of it. They end up blowing everyone’s doors off for a year before they get pushed back. It’s not an opinion, it’s a trend, new cars always win. But the organisers have to catch up, and that’s understandable.”

It’s another big issue for BoP ‘scientists’, you need to know the cars inside-out to accurately balance them with the other cars in the field.

Ever wondered why new cars can come out and dominate? That’s your answer: in order to truly place a fair BoP on a car, you need to understand how the car will be affected, and organisers therefore have to work against engineers who know their cars inside-out. It takes time.

The most interesting point from the day, though, was the fact that placing a huge slab of ballast in a car doesn’t make a huge difference in most cases and instead is used for fine-tuning. Unless you’re going to place an enormous amount like 70kg or more in the car (effectively adding a passenger), you’re not going to slow it down as much as a small tamper with the turbo or restrictor.

“If you tweak a car’s restrictor by 1mm, then add 40kg of ballast, the 40kg sounds worse to the general public, whereas in theory the weight isn’t as bad as a change to the restrictor,” Dolby explained.

40kg sounds worse to the general public, whereas in theory the weight isn’t as bad as a change to the restrictor Craig Dolby

“Some cars react weirdly to ballast. It depends how you tune the horsepower down, too, whether it’s on turbo or restrictor, because one car may get hit a lot harder on the restrictor, and one might actually react a lot more to a change in turbo. I’ve been in cars where you take the turbo boost away a little and you’re miles off the pace.”

“I agree,” commented Morris. “A 1mm restrictor change can be the difference between pole and 12th. If you went to Paul Ricard, it could potentially be a disaster to be down on power, but at Brands Hatch Indy, for instance, it wouldn’t make much difference at all. There are some tracks where if you’re down on power you can go quicker, because out of corners you can get the power down easier. It hurts you once you get to fourth, fifth and sixth gear. At Spa, too, it would kill you, because all the straights are up hill.”

“Being down 5bhp at Spa would be bad; 30bhp, you’d be ruined,” said Dolby.

If someone came to me and said ‘we’re taking 20 millibars out of your turbo’ I’d want to go home. If they slapped 15kg on, I wouldn’t really care. Seb Morris

“Yeah,” Morris reacted. “And that’s the thing, when I go to a race meeting, I have a look at the turbo straight away. They put the weight in a big red marker, but I’m frantically seeing if they’ve changed the turbo. If someone came to me and said ‘we’re taking 20 millibars out of your turbo’ I’d want to go home. If they slapped 15kg on, I wouldn’t really care.”

The human aspect

Another discovery was just how much of an effect the changes have to amateur drivers as opposed to professionals, and how different the drivers have to tackle a circuit. Sometimes, on short notice, drivers must change the way they drive, which can at times have as big of an effect to lap times as the BoP tweaks, especially if the car feels drastically different through corners. Being able to adapt quickly can be the difference between a good and a bad weekend.

“When you have a big BoP change, for a pro it may take five laps to get used to it, but for an am, having a load of power taken off, your braking points have to change and so do your lines,” said Dolby. “It can take all weekend to get used to it. Every reference point changes.

“Mostly ams will do what you tell them to, but because not everything comes naturally to them, they will feel the effects of a big BoP change. It’s like when it rains during a race, a pro will just power through it and change his style, whereas an am may back off massively. Its the same when the they get in the car in first practice after a big BoP change.

Ams will do what you tell them to, but because not everything comes naturally to them, they will feel the effects of a big BoP change. Craig Dolby

“With the weight it’s not so bad because you’re hitting the same speeds, there’s only a one or two-metre difference, but when you’re down on power, you’re going 10kph slower.

“When I had the reduction in power, it changed the gearing,” Dolby continued. “In places where you would shift to sixth, I was staying in fifth: you have to compromising your driving, get the exits right. You need to get the car in a position to get on the power a bit earlier, especially somewhere like Silverstone with the long straights. You have to be more precise on the driving.”

When you were down on power, you weren’t even close to sixth. With the ballast, I was able to get sixth gear though Seb Morris

“I agree,” said Morris. “I wasn’t able to get to sixth anywhere, but with full power I was in sixth for a good three or four seconds down the Hangar Straight. When you were down on power, you weren’t even close to sixth. With the ballast, I was able to get sixth gear though.

“I think if you see a second-and-a-half difference somewhere, pro to pro in a stint, you know they’ve been affected badly by BoP.”

It was astounding just how much discussion there was between both Dolby and Morris after the different runs, especially details about braking points and gear selection. It was similar to how it would have been on a race weekend if they were team-mates and brought home just how much there is to BoP changes that you don’t see or think about.

Staying consistent

A world without BoP would make GT3 and GTE an arms race on an industrial scale. For GT3, a primarily customer-based formula, it would drive people away, and for GTE, the already sky-high costs would only increase as the big factory teams scrambled to make their cars as quick as the rule-book allowed. Because of that, BoP is here to stay, at least for the foreseeable future.

As a driver, to win a title requires you to stay consistent, and more so than just keeping the car on the tarmac, because you need to play the BoP ‘game’ to ensure that you’re there or thereabouts every weekend.

“It takes the pressure off for drivers,” concluded Dolby. “You know sometimes that you can’t push the car anymore to gain time, because that time isn’t there. Sometimes you have to take it on the chin and try again next week. As long as you’re in the fight, it’s okay, and that’s why most of the time the rule-makers do so well, because in GT3 you have 12 or so manufacturers, all with a chance of good results throughout the year.

You know sometimes that you can’t push the car anymore to gain time, because that time isn’t there. Sometimes you have to take it on the chin and try again next week. Craig Dolby

“BoP isn’t easy, but it is a force for good. Sometimes it ruins your weekend, but most of the time it doesn’t. You can beat yourself up about qualifying 16th, then they make a tiny adjustment before the race and you’re setting fastest laps.

“When that happens, and it’s that close, it shows you they’re doing it right.”