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Ranking The Gpl Mods By Physics Accuracy


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#1 prize

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Posted Sep 26 2020 - 11:17 AM

How would you rank the following mods according to the accuracy of the physics:
1955, 1965, 1966, 1966 can am, 1967, 1967x, 1967 F2, 1967 sportscars, 1967 Formula Libre, 1968, 1969x, 1971 can am?

Also, how does the rFactor 2 Brabham BT20 compare in accuracy to the GPL mods?

Thanks!

#2 Alan Davies

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Posted Sep 26 2020 - 11:36 AM

Nobody knows as I doubt anyone here has driven any of the cars from any of those periods (I would like to hear from anyone who has because that would be a great reference). However, 1965, 1967 F2 and 1969x feel like driving as I know it.

#3 Saiph

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Posted Sep 26 2020 - 12:18 PM

:yeahthat:

#4 Jim Pearson

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Posted Sep 26 2020 - 05:36 PM

The ONLY way to do that would be to ask a very fast GPL driver to test all the mods, and all the cars within mods, then compare them with what is known about how all the individual REAL cars actually behaved on track, historically.

One caveat though; he would have to know exactly how these cars were set up and use those historically accurate setups without variation / modification.

Using any other setups would invalidate any assessments, which, as has been noted already, are still subjective at best.

So if our knowledge of the actual handling characteristics of individual cars and how they were typically set up is limited, there is no way to accurately answer the question, because each car set is a series of reasonable best guesses for physics.

IMHO.

#5 prize

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Posted Sep 26 2020 - 06:27 PM

Aren't rFactor and iRacing calibrated against real cars?  If so, then the iRacing 67 lotus and the Brabham BT20 are gold standards.  To check how accurate the GPL mods are, one could just compare vs the gold standards for equivalent real-world setups.  If the GPL cars deviate from the gold standards, they could be recalibrated to match the gold standards as closely as possible.

Has anyone compared, say, the 67x lotus vs the iRacing lotus 67?  The iRacing car should be pretty accurate, at least its tire model has been calibrated vs real-world data.

Another question - which mods include brake fade besides the 55 mod?  Without brake fade, you can approximate antilock braking with combined acceleration and braking in the brake zone (this is unrealistic).  If the 55 mod is the only one with brake fade, perhaps it is the most accurate.

#6 mcmirande

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Posted Sep 26 2020 - 06:39 PM

1967 formula libre?? Did I miss something??

Marcos

#7 Michkov

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Posted Sep 26 2020 - 08:16 PM

View Postprize, on Sep 26 2020 - 06:27 PM, said:

Aren't rFactor and iRacing calibrated against real cars?  If so, then the iRacing 67 lotus and the Brabham BT20 are gold standards.  To check how accurate the GPL mods are, one could just compare vs the gold standards for equivalent real-world setups.  If the GPL cars deviate from the gold standards, they could be recalibrated to match the gold standards as closely as possible.

The thing with "real" cars is that they are modern cars, restored, brought up to modern safety standards and all that jazz. They are not necessarily period accurate, even that term is a tricky one since F1 cars by their nature are prototypes that undergo modifications from race to race.

#8 jgf

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Posted Sep 26 2020 - 09:04 PM

Given how much input we get from driving any car in real life - the feel of the car's mass, the chassis flex, vibrations from the suspension, G forces;  all of which we process subconsciously as we drive - and the lack of all this input in even the best sims, I think the best we can state for the accuracy of any representation is that it performs reasonably.  Barring gross errors (your TR-4 can go 200mph) it is doubtful anyone can make any "expert" assessment of the realism of physics in any sim, even if you have experience driving the real car;  and if you've no experience in the real car, it's opinion and expectation.

Consider whatever car you drive every day.  If given an "accurate" representation of that car in your favorite sim, how accurately do you think you could gauge the realism of its physics?  Now, how accurately could you gauge a car you have never driven?  

This is not a castigation of anyone's modding efforts in any sim, only my opinion that we are all discussing opinions.  (FWIW, I raced from 1970 to 2007, anything in which i could get seat time, and even in sim cars with which I can claim familiarity in RL the best I can say is it performs as I expect/remember.)

#9 prize

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Posted Sep 26 2020 - 10:32 PM

A Formula Libre car uses a non-standard 67 chassis-engine combination.  To create one, select "67 FL" from the CARSET dropdown in GEM, then select a new engine from the dropdown menu directly to the right of "Standard Chassis" on the right side of GEM.

#10 prize

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Posted Sep 26 2020 - 10:37 PM

I think it is possible to model modern racecars with excellent accuracy.  iracing.com contains quite a few testimonials from professional drivers describing how true-to-life the iRacing cars are.  When official NASCAR races were held virtually on iracing during the early part of the pandemic, dozens of professional drivers new to sim racing were impressed with iracing's accuracy.  Even more impressive - one driver said setup adjustments he makes in his real life car have the same effect as in the virtual iracing version of his car.  I conclude that iracing really is accurate, at least for the cars described in the testimonials.  This might also be true of the iracing lotus 67, but I didn't see any information about how that iracing model was validated.

#11 PTRACER

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Posted Sep 27 2020 - 01:17 AM

A few points:-

1. iRacing's tyre model is awful and always has been. One of the real life Indycar drivers who raced the virtual Indycar series this year said it was nothing like the real thing, since the iRacing version would just unexpectedly lose control approaching the limit and be unsaveable. The real car is much more compliant at and over the limit. Here is real racing driver Nicki Thiim also describing it as "f***ing sh*t" for the same reasons:
https://www.youtube....h?v=PI28NeVFKtc

2. Very few people who have driven the GPL cars in real life have driven it at the limit. A car can feel like any other car at low speeds, you have to push it to understand it. Alexander Rossi is the only one who has done that in a Lotus 49 at COTA a few years ago, but I heard no description from him of its handling characteristics and he looks out of his depth driving it anyway.

3. 20 years ago, people reviewing cars would tell you exactly how it handles at low speed and high speed, over bumps, power delivery, etc. The only comments drivers give these days is "Woohoo!" and "Yeehaaa! This is fun!" which is of zero interest to anyone. I have never seen anyone else describe how these cars feel to drive in real life. I hope I at least did better when I wrote about my Ferrari F430 track experience 2 years ago: http://www.the-fastl...430-track-test/

Edited by PTRACER, Sep 27 2020 - 01:17 AM.


#12 mcmirande

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Posted Sep 27 2020 - 07:29 AM

"2. Very few people who have driven the GPL cars in real life have driven it at the limit. A car can feel like any other car at low speeds, you have to push it to understand it. Alexander Rossi is the only one who has done that in a Lotus 49 at COTA a few years ago, but I heard no description from him of its handling characteristics and he looks out of his depth driving it anyway."

That point is essential. I really think it would be more accurate the opinion of some guy that raced at the limit a Formula Ford than that of a guy that did just 2 laps with the real Lotus

#13 gliebzeit

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Posted Sep 27 2020 - 07:44 AM

Marco, I find your comment a 'Royale' truth.


:)

#14 DuncanS

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Posted Sep 27 2020 - 07:48 AM

https://www.youtube....h?v=daUJc70CjhA

Nimble, light, has a desire to spin (power of the DFV), very drivable, tracktable engine, what a lovely sound from the engine, nice little gearbox, you have to use it sequentially, brakes feel a little bit dead, slides across the road (corners) but it is in balance (controllable), it is unison.

A purity, a nimbleness...


WELL IT'S CERTAINLY BEEN A PLEASURE!


More

https://www.youtube....h?v=-crz3jYqogo


I think it's possible to make a reasonable and fair assessment of gpl (and it's various mods') physics

...to the real life (without having to know all the exact numbers and data), or dust on the circuit, wind direction, ambient circuit temp and on and so forth.....

#15 jgf

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Posted Sep 27 2020 - 09:54 AM

View Postprize, on Sep 26 2020 - 10:37 PM, said:

I think it is possible to model modern racecars with excellent accuracy.  iracing.com contains quite a few testimonials from professional drivers describing how true-to-life the iRacing cars are.  When official NASCAR races were held virtually on iracing during the early part of the pandemic, dozens of professional drivers new to sim racing were impressed with iracing's accuracy.  Even more impressive - one driver said setup adjustments he makes in his real life car have the same effect as in the virtual iracing version of his car.  I conclude that iracing really is accurate, at least for the cars described in the testimonials.  This might also be true of the iracing lotus 67, but I didn't see any information about how that iracing model was validated.

But again that assessment is based on the very limited input from a sim.  Personally I liken this to listening to a full symphony orchestra in person as compared to hearing it on a small radio;  the music is the same but....

#16 jgf

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Posted Sep 27 2020 - 10:07 AM

For anyone interested, here is the article with Rossi, a road test comparison of a Lotus 49 and a ZR-1

https://www.roadandt...e-64-8-roa0513/

The comments of  the mechanic accompanying the Lotus are more interesting:

"... the period tires are :crap: and the suspension doesn't work with modern rubber; it's prone to fuel starvation; the sequential, H-pattern ZF five-speed is fiddly and never seems happy. "

This underscores an ongoing debate in vintage and historic racing series - do you upgrade tires, suspension, brakes, ignition, etc., for performance and safety, or do you keep the car completely original.

#17 jgf

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Posted Sep 27 2020 - 10:58 AM

View PostPTRACER, on Sep 27 2020 - 01:17 AM, said:

... Very few people who have driven the GPL cars in real life have driven it at the limit. A car can feel like any other car at low speeds, you have to push it to understand it. ...

Not exactly accurate.  In high performance cars, particularly race cars, everything is optimized for high speed performance.  Why do you think you rarely see people driving their Ferraris, Lamborghinis, etc. around town;  not because of their value or insurance rates, but because at street speeds these cars are miserable to drive.  Large tires mean the steering is slow and heavy below around 50mph,  brakes are prone to grab, engines have little low end torque so you're driving in first or second gear all the time, and you sit so low you'd like a periscope in traffic.  The reverse is true of street cars, optimized primarily for driving 30-60mph, they may be capable of 130 on the highway but you will not be comfortable.

As for the real cars of GPL, like most F1 cars very few were made of each, they were quickly outclassed by the early seventies, and ended up in club racing or museums.  For example, only seven Lotus 49s were made;  all still exist, four in museums, rarely if ever driven, two in private hands in Europe, occasionally raced (I believe one is owned by Adrian Newey), and one in the US, restored in 2010 to original 1967 configuration and frequently appears in vintage races (its owner/driver, Chris MacAllister, would be the person with whom to discuss handling).

And, ftr, people in vintage racing do push the cars to the limit.  I was skeptical of  this until becoming involved myself, and admit my performance was occasionally affected by the knowledge I was driving something worth three times as much as my house.

#18 Royale

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Posted Sep 27 2020 - 11:12 AM

View Postmcmirande, on Sep 27 2020 - 07:29 AM, said:

"2. Very few people who have driven the GPL cars in real life have driven it at the limit. A car can feel like any other car at low speeds, you have to push it to understand it. Alexander Rossi is the only one who has done that in a Lotus 49 at COTA a few years ago, but I heard no description from him of its handling characteristics and he looks out of his depth driving it anyway."

That point is essential. I really think it would be more accurate the opinion of some guy that raced at the limit a Formula Ford than that of a guy that did just 2 laps with the real Lotus

And then there is over the limit   :wave:

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#19 Iestyn16

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Posted Sep 27 2020 - 12:01 PM

Here's what each physics set encapsulates in my mind:


1955 - brake fade, lift and coast

1965 - smoothness

1966 - low engine rev fuel starvation, 2L vs 3L

1966 CA - low/high speed grip balance fixed, Chap 2F clutch moveable wing

1967 SC - heavy cars

1967/FL - trail-braking, low drag environment i.e. 'permanent slipstream'

1967x - you have to 'muscle' the cars, full season carset with fixed physics = 'GPL2'

1967 F2 - light cars, large slip angle highlights the aggressive driving style exhibited by Rindt in F2

1968 - wings vs non-wings, follow on from 1967x with a split season carset

1969x - downforce setups, grip starts to overwhelm engine power, i.e. U corners as opposed to V corners

1971 CA - high speed grip, 'pogo' of the suspension at speed, you start to see features that later came in with the ground effect era, such as 'porpoising'


In GPL, my favourites, aside from the original carset, are the Chap 2F & 67x, while I really enjoy racing the 66 & 67 F2, but haven't driven 68 much yet. 55, 65, 69x are further away from the 'classic GPL67' driving style, although this does show the progression of this era well, along with the beefier SC/CA/TC cars. Rally too.

PS. Who is in the flying car? That roll bar looks dangerously low! I also like the sound of Greg's cryptic comments! ;)

Edited by Iestyn16, Sep 27 2020 - 12:24 PM.


#20 Lee200

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Posted Sep 27 2020 - 12:05 PM

View PostRoyale, on Sep 27 2020 - 11:12 AM, said:

And then there is over the limit   :wave:

:bigclap:




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