Making a mod: how to build a FunCup car in Assetto Corsa

Those who have visited The PaddlUp Rooms and put one of our Blade simulators through its paces will know that the cars available in the virtual world are nigh-indistinguishable from their real-world counterparts.

But have you ever stopped to consider the process of building a like-for-like virtual vehicle from the ground up? Luckily, PaddlUp's resident simulator expert, Riley Philips has done just that with his FunCup car (that he races on real-life circuits across the UK) and shared his Assetto Corsa mod-making experience with us in extensive detail.

The mod itself is available for download on RaceDepartment.

An interview with Riley Phillips

The main idea came from wanting to use a training tool to get an advantage against other people I was racing against. I didn't have the money to drive on tracks all the time so I decided the best way to go about it would be to use my simulator and basically practice every day in the build-up to a race. It helped a lot because I roughly knew my braking points, lines, etc. before I'd even been to a track.

I started by using an MX-5 cup car and it was OK, it was a similar pace to the FunCup but that was about it, it also came with a manual gearbox which wasn't ideal so I thought 'I can do better than this' so I modified it a little bit giving it a sequential gearbox and that improved things but I quickly realised if I wanted to make a big difference I was going to have to build it myself.

Fortunately, I knew someone who did 3D modelling and I asked him if I take some photos of my racing car, can you make it for me and he said yes. That took a couple of months and eventually I had a model which was put into the game, once you have the 3D model, simply put, you upload the file into the programme and it tells Assetto Corsa what material the body or the tyres and everything else is made from.

The data

Then you have to deal with the physics for it like the handling and the engine. I'd been racing in cars for about a year at this point so I had some real data to look at but I didn't have any way to compare it just yet so I looked at the times and speeds around the corners and when I was changing gear and I got that pretty close to real life without having to look for gear ratios or power outputs, I didn't have any of that information. That was one of the main problems to be honest, I asked the manufacturer of the FunCup car and it was actually a Belgian series before it came to the UK and the UK and European series are now split and aren't run by the same people. Long story short, I wasn't able to get any blueprints, that would've made things a lot easier!

It took about nine months to learn everything to do with the data files. In all honesty, it was a lot of experimenting and trial and error of changing the values and seeing what it did to the car. I made my own notes inside the files so I remembered what I was doing. There are so many different parts to the suspension for example and you have to plot lots of different parts of it in 3D space and then obviously that affects the handling.

I had a few small bits of data that I could input but that was mainly like the strength of the springs, obviously, then you need to calculate everything else to do with that spring so it gets pretty complicated and technical, quite quickly. You can't just say it's got 100bhp and be done with it, you have to make sure the aero and the tyres can handle it.

One of the things I did to test this car was I ran a private series for it with a few of the FunCup drivers who were on the grid. Julian Thomas was racing in FunCup at the time, he's Managing Director of RACELOGIC and he requested his own livery so then everyone ended up with their real-life car. During the series, there was a mix of abilities from people who know how sims work that those that didn't.

When things got underway Julian said to me that he thought the handling wasn't right for the car, he'd done some calculations and found out it wasn't the same. The easiest way to describe this is that the G forces were adding together when going around a corner, so one G backwards and one G sideways was adding up to be two when it should even out across them to equal one. I have to give Julian a lot of credit for the end result as he ended up giving me the VBOX software to help develop the car. So eventually we found out that the tyre file was missing one line of code which was absolutely vital.

A virtual FunCup championship

We had around 20 cars racing and it just ended up being like a normal FunCup weekend, everyone was having loads of fun with it. We live-streamed it on twitch and we had the actual series commentators on board as well.

I didn't really do any advertising for it, I just walked down the paddock and talked to people about it but then it spread to Europe through the Facebook streams. In the end, I got a call from the European organisers and they asked me to run a similar online series for them which resulted in a European series with a few of the guys from the UK in there as well, the first race was the busiest with 35 cars on the grid!

Both the UK and European series were really competitive. We had one guy who was a mechanic but he was really quick as well as someone who now does Formula Renault who was really fast too. Luckily I won both of them, I think if I did poorly in a car that I'd created that wouldn't look very good on me!

There were a few close calls with copyright issues as the European series is associated with VW so I couldn't really get too involved with that.

After all of those series, I gathered a lot of data from different drivers which I could then compare to the real thing through VBOX. So it's getting really close to the real thing now but I think I'll always be chasing that last bit of handling or last tweaks because I don't know everything there is to know about modding, I've just done this through trial and error.

From start to finish, the project took place from late 2019 to February 2020, which was then very convenient timing when we went into lockdown and everybody was asking me about what I'd made.

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