The 18' Porsche 911 gt2 rs is a lot faster than the 918 Spyder IRL but has much lower PI in the game

So in real life the 2018 Porsche 911 gt2 rs did 6:47 on the Nordschleife, which is 10 seconds faster than the 918. I was able to do 6:56 in the 918 (stock) in FM7 (rolling start), which corresponds to it’s real life performance. With the 911 however I struggle to go any faster than 7:07. I’m not the best driver of course but I doubt anyone can drive the 911 faster than the 918 in this game. And that’s because It has a PI of “only” 800 while the 918 has 857 if I remember correctly. Which doesn’t really make sense since the 911 IRL mops the floor with the 918 (on the Nordschleife at least).

So either the 911 in the game has much lower PI than it should have. Or the one set the lap record IRL was heavily tuned/modified. What do you think?

According to Porsche, the 911 GT2 RS that set the record was completely stock. (Both were, as they ran two cars that day.)
They also say they used N-Spec Michelin Pilot Sport Cup 2S tires, which come on the car.

That would be a good question for Porsche in real life, since the 918 has better power-to-weight ratio and higher top speed.

Hmm, idk. maybe the massive amount of aero on the car?

Nordschleife times don’t really count because the conditions differ across the track… you don’t know if the GT2RS ran on a better day of run than the 918… and then there’s the fact of several years of tire development make a impact… and they’re set by different drivers.

The tire model in Forza is the same on everything given selections of street, sport, race, etc… so maybe numbers stat simulation wise give the 918 the better car?

5 Likes

I know the conditions vary and can have a significant impact on the lap time, but still 10 seconds faster than the already very fast 918 is simply mind boggling. I think the only explanation is T10 must have acquired the car’s performance data directly from Porsche, before the 911 set the record, and Porsche just didn’t expect their car would go that fast so the data they gave T10 were much lower than they should’ve been, which resulted in a “low” PI in the game.

Trying to replicate exact car performance on real tracks with in-game performance is not really possible, there are too many variables that Forza doesnt try to simulate and there is way too much variance with regards to player skill around a track.

1 Like

You didn’t run them as “stock” with the PI numbers you quote! You have to remove the homologation parts to race as “stock”.

I certainly did. In free play and I turned the option to allow upgrades off. The 2018 911 gt2 (S 800) rs has 8.1 speed, 6.0 handling, 9.2 acceleration and 6.1 braking, while the 918 (R 858, yes I know I wrote 857 but that was just bad memory) has 7.9, 6.2, 9.4 and 6.3 respectively.

1 Like

OK, I guess it isn’t homologated then? S 800 is the same as the one on the buyer’s garage screen?

Downforce is not simulated very well in this game for example the p1 gtr is around 2 secs a lap slower than a gt3 car (a guy on youtube who owns the p1 gtr and a mclaren Gt3 said this) but in game the p1 gtr is in p class and the bently gt3 car is R834 - basically downforce and grip and calculated very well in this game.

Well first of all I think it’s a pretty huge leap to assume Porsche might have used ringer cars to set lap times and put their entire reputation at stake based on simplistic performance models of cars in a video game.
Where do we even begin? As far as I understand it, the Forza PI number is a result of an equation that combines a bunch of on-paper specs, such as power to weight, grip, top speed, etc, and also factors in how fast a lap an AI driver can get out of the given car on a track, which track I’m not sure, if that info is even available.
What I do know for sure is what PI doesn’t take into account, as other people have brought up, there is 4 years of tire development between these two lap times, different brands, let alone models of tires are not modeled in the game anymore, so that’s a big variable out the window. As far as the game is concerned both cars are running the same tires in whichever category of tire performance you choose. The wide range of traction control systems, settings, electronic differentials, various different awd systems that work in different ways aren’t modeled either. Which brings me to another point, the real 918 is a Hybrid car with electric motors driving the wheels and a big battery pack that can be drained in use. Pretty sure that in the game it is effectively modeled as an AWD car with conventional differentials that gets its power from one source, as is every other awd car in the game. I don’t know this for certain, but it has come up as a factor when other hybrid cars have run the ring, such as the P1 and i8. when going flat out with full drain on the battery, there’s definitely a chance that the car will run out of maximum output before the end of the lap, while it still might be enough to set a faster lap than most production cars, a car with similar performance to start with in the 911 GT2 RS doesn’t have this issue and will be just as powerful at the end of one lap or 20 laps. The game the 918’s hybrid characteristics aren’t modeled and it’s maximum performance is always available.

Beyond that, the game just isn’t complex enough to take into account all the slight variables in traction, diff setup, electronic aids, track conditions, aero setup, suspension setup, etc that might just make the 911 GT2 RS work especially well on the Ring, 4 years of additional testing on one track. Then of course there’s one of the biggest variables of all, the driver. What will be interesting is seeing how lap times compare on other tracks after some more independent testing is done. You really just need to take the whole PI system with a grain of salt, I remember, I believe it was in Forza 3, making a car AWD massively reduced it’s PI number due to how heavily the system weighed power to weight, allowing people to make massively overpowered AWD cars that would slaughter a RWD car with the same PI. If the system was really an accurate measure of how a car will perform vs another car, leaderboard cars wouldn’t exist either.

1 Like

I think in real life it’s faster than the 918 because it’s lighter, has better tires and can use it’s full 690 bhp all the time while the 918 is stuck with 608 bhp when the electric motors are recharging.

There could be many reasons why it’s slower in game, Forza isn’t the most realistic game around and most likely doesn’t simulate enough things.

1 Like

I think he’s on to something. Forza is definitely not simulating the electric motor issue. Forza is simulating the 918 at its max ability.

Yup, brought this up in my post as well, not simulating how electric motors work and how batteries would drain in any cars for that matter. As far as the game model is concerned, it’s a car that gets all its power from one source and always has the same amount available.

If you put the N spec tires that the 911 GT2 comes with on the 918 you would likely see a very different outcome. Tire compound is how Lamborghini beat the 918, and how the 911 beat the Huracan and 918.

Main thing is the tires… Forza only has 4 compunds (for racing). Stock, Street, Sport, Race… It’s not enough imo.

Yup. Since the Pilot Sport Cup has been out, for years now, the game needs to add a new tire compound - between sport and race.

Well guess I just can’t take the PI numbers in this game too seriously then. You’ve given me very useful information thanks guys.

1 Like

Needs more than that. If we take in a lot of different compounds, there’s street, sport, touring, racing, drag, drift, race, ect. Heck, we should have to buy rain tires for the car just to compete in the rain idealistically, but we don’t, they just give them to us. Not to mention different speed limits on tires. They want to call this a simulation racing experience with less on actual simulation and more on 60 fps and HD graphics. They lost touch.