Posted by: drracing | January 22, 2016

Racing Drivers and/or Simracers – New cars in Portfolio

Hi everybody and happy new year 2016!

Again long time since last i published something here.

And actually, also this one will not be a lengthy post.
I just found this article floating around the web and found it very interesting. It talks about another guy, basically with only simracing experience, who had a chance to step into a professional career (or at least try it), this time with the financial support of Mazda in the US.

This shows, once again, how driving simulation could not only help to develop driving skills and train a driver between races and tests, but also how it could be an effective school for young guns wanting to learn basics (but not only basics) before to jump in a real race car and without spending hundred thousands of euros in a real race car program.
Money will always be the biggest problem, of course. But cases like the one i am linking here seem to give some hope also to people not having a very rich dad.

There are of course things that no simulation can prepare to, see for example the physical effort that drivers need to sustain, above all when driving cars with proper downforce. And this is of course something that cannot be underestimate.
Nonetheless, simulations are getting so good to be really able to help a driver to improve himself/herself and to let a “trainer” to shape his/her skills, style and knowledge.


On a different note, the list of the cars i modeled in rFactor basing on real data is getting longer and longer.

Beside the already established LMP2 and LMP3 projects, during the last months i built the physics of other cars, including an LMP1 based on Perrinn data (and about which i hope i can write soon here), a new F3 model, based on Dallara F312 in F3 Euroseries spec, a mid engined GT3 car and a new LMP3 vehicle, based on real data of a lately released french race car.
This later model is actually part of the collaboration with the LMP3 team i already worked with in 2015 and that i will go on supporting also in 2016.
The results are really interesting: i cannot show too much here yet, unfortunately, but matching (thanks also to more accurate data coming from the team compared to what they had about the previous car they used) is already very very good.
About this (and somehow taking up again a topic i discussed in some previous posts), it is also interesting to see how lap times also matches with reality when working with detailed circuit models.
Because of one of my projects, i had a chance to access some laser scanned track models and test my vehicle models there. The results of using detailed vehicle models built in rFactor with such track models is above possible explanations (above all when using appropriate hardware). Beside the feedback on the steering wheel, it is also extremely interesting to analyse suspension movements with data logging and, in general, to analyze how vehicle behavior changes in comparison to a “normal” track model.
Moreover, thanks to the collaboration with a very talented guy and track modeler, i now also have access everyday to track models with an accuracy and quality comparable to that of laser scanned tracks (at least for all what concern track layout, kerbs, elevations, etc and missing only the detailed modeling of every bump which belong to laser scanning too). He developed a new method to define tracks layout, elevations, camber, etc basing on very detailed data and the results are really amazing.
This, together with some important updates to my hardware (among other things, my driving rig now has a Direct Drive Steering system and load cell pedals in place), allows realism to go another step forward, making even more interesting to evaluate car reactions not only through data analysis but also through subjective feedback.
Beside the driving feedback, it is extremely useful to have the chance to rely on accurate track models, because it allows to validate the model against real logged data without having to worry about how precisely the track is built inside the simulation.

It would be extremely interesting to have a chance to let some real drivers (beside the ones involved with the projects themselves) to test these new babies and hear their feedbacks.
Logged data matching, as i had some chances to show, is really intriguing so i am pretty confident in saying that it could be good fun, for somebody with race car driving experience, to have a try!

Next up, Renault RS01!



  1. Laser scan data is expensive to obtain and not handed out for free. Can you explain how you’ve got access to this data, legally? iRacing do their own scanning, and AFAIK, Kunos (Assetto Corsa) have some contractual arrangement which certainly wouldn’t involve giving it away.

    On another point. Can you explain how sim developers use moments of inertia? What I mean is this: consider a vehicle in an oversteer situation i.e. the rear is ‘swinging around’ and the driver countersteering appropriately. As I understand it, to calculate what’s going on, you’d need to know the axis of rotation (visibly, it would seem to be near the front of the vehicle), the resultant torque about this axis, and then using the moment of inertia (2nd moment of mass) about the axis of rotation, calculate the angular acceleration. But how does the sim know the correct moment of inertia for the precise axis of rotation at the point in time? One hears devs talking about summing torques and forces about the centre of gravity. Which frightens me a bit 😉 – because most of the time the vehicle isn’t actually rotating about the centre of gravity in real life. But it often looks that way in most sims/games with the exception of LFS. Could you enlighten me?

  2. hi Pete,

    thanks for your comment.

    Regarding the tracks, i cannot say too much (secret), but you can be sure the there are people out there able to gather required data or founding to access laser scanning!
    Not me personally, unfortunately, but i had a chance to test some of my models on these track models with the results i shortly described.

    In any case, i think some news have floated around the internet some time ago about somebody who converted a laser scanned track coming from one of the above mentioned software to use it inside another one, only for private purposes. This guy even published a video on Youtube to show his work.
    I am not sure about this, since i am no legal expert, but i guess that as long as you don’t try to sell it or to share it with anyone else, such a thing is not forbidden. But, as i said, i am no legal expert, so i may well be wrong.

    Regarding the moments of inertia, well, i cannot say for sure how the rFactor’s code works, since i don’t have access to it.
    As far as i know, the moments of inertia are meant to be about the CG, mainly because it is an easier point to define, i guess.

    This is what i assume to be true when building my vehicle models. Since measured moments of inertia of a certain vehicle are practically impossible to find (at least, i never found a team who have measured them or who had any data about this), i developed a very easy excel tool to estimate them based on the main car masses (Unsprung masses, Engine, gearbox, chassis parts, etc) and their position.
    I basically calculate the moment of inertia of each subsystem (assuming simplified shapes, like cylinders or parallelepipeds) and then “transport” it to the CG using Huygens-Steiner theorem ( There is a small “mistake” in how the code threat the unsprung masses MoI, but it is something known and i normally take it into account too, correcting appropriately the values i calculate to input into rFactor what i need to obtain what i want.

    Although, as i said, i cannot be totally sure about this, i guess that this is also what the software does/assumes, transporting the overall vehicle moment of inertia, defined with respect to the CG, to the effective rotation center in space applying the parallel axis theorem.
    The vehicle rotational center is probably defined basing on tire forces: assuming, for sake of simplicity, that the tires only exchanges plane forces with the ground, each tire will produce a force (combination of an x and y component) that can be described by a vector. The four tires forces/vectors (or, the resultant vectors for front and rear axle tire forces) will intersect in a certain point in space…
    At the beginning of a cornering maneuver, there will be mainly a contribution coming from the front tires, also producing a yaw acceleration. Little by little the rear tires will “catch up” and produce also lateral and longitudinal forces and a yaw moment contribution.

    You can find some very interesting discussions about this here:

    Again, i have no access to rFactor’s (or whatever other simulation software) code, so i cannot say nothing for sure about it, but what i tested and learnt myself or talking to other people.
    What i have seen is that, both basing on driver feedback and logged data comparison (as you may read in other post in this blog), using this approach the virtual car seems to behave in a very similar manner to the real one.

  3. Thanks for reply

    I think iRacing would not be happy about that. And anyway, I believe both sims mentioned have more complex laser scan data that the physics engine uses to what’s visible. Certainly is the case in iRacing that it’s a simplified version that’s seen.

    Parallel Axis theorem, i.e. compute MOI’s about centre of gravity and then ‘transport’ to axis of rotation was the only thing I could think of too. 🙂 Would be interesting to know for sure though.

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