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Topic Review

 posted on 13-8-2018 at 00:27
Note: This is a re-post of a topic originally posted in 2016 on Slotforum international

As Disca published the first DiSCA digital GT3 Open event and regulations on May 15th, the expected questions about the how and why of certain choices were posted.

DiSCA GT3 Open, looking for a digital set up
Some of the test for the new DiSCA GT3 Open rules we done on the 32m Suzuka shaped Ninco track of the SRC Eindhoven in Best, NL.
Besides testing the Scaleauto Baby Sprinter motor for O2 compatibility we also tested the several tyre and wheel combinations we considered for the hand outs.

Below you'll find two tables, one with data on the magnetic pull of the different motors we tested and the influence of their ride height has on the magnetic pull.
The second table list the best laptimes we did with some of the motors with the different tyres and different ride heights.
Although the 2nd table lists the best lap times these were not the goal of our tests, they were just a reference tool.
The goal was to look for a set-up for the GT3 cars that would have "... a sharp level performance and drivability".

Preparation time of the hand out tyres/wheels
The first test we needed to do was to see how much time it would take to prepare the handout tyres from hand out into RTR wheels. Tested were :

NSR ultimate grip 20 x 11 (black 5230)
NSR WEC 20 x 11 (grey 5230)
Slot.it N22 20 x 11,3 (PT1171N22)
Slot.it F22 19,5 x 10 (PT27)
Scaleauto Procomp 3 20,5 x 9 (SC-2018)

As the time for tyre preparation will be limited at the GT3 events, I had set myself a target time of max 15- 20 minutes per set (requiring 30-40 minutes for two sets). Of the "rubber" tires the Slot.it F22 required the least time (slips right on the wheel but benefits from slight trueing), the N22 and NSR tyres required the most (as they needed to be glued and trued). Interesting was that while both the N22 and NSR tyres are listed as ø20,5mm, when mounted on a ø17,3mm wheel they're actually above the 21mmø to begin with. Within the target time I managed to true the N22 and NSR tyres down to 20,8 and 21,0 respectively.
Additionally I needed to true at least one side of the tyres to a width of 10mm to avoid pinion clearance issues @ the max axle width of 62mm.
The Scaleauto Procomp3 sponge wheels required no preparation at all.

Motors and their Magnetic downforce in relation to their ride height (a.k.a Ground Clearance)
As all of the current O2 ready tracks that can host larger events have metal(lic)rails, the magnetic "down" force of the motors would be part of the equation in their suitability for the GT3 formula. Here we measured two values, the magnetic pull translated in grams on a Magnet Marshal and the ground clearance under the centre of the motor measured in mm. Why? Well first of all beacuse not everybody has a Magnet Marshal at their disposal and even if you do, calibrating them would be an issue. Secondly because, as you can see in the table below, the magnetic pull of a motor and its distance to the track rails are directly related to each other....and that relation is exponential.
Obviously the lower you get the harder it starts to pull, but if you look at the far right column (NSR Baby King) you'll see that the first decrease of GC by 0,5mm in increases the magnetic pull by 5gr, the second decrease with just 0,4mm increases the downforce by 10gr huh.gif

What we were looking for was a motor that would have a similar level of downforce as a DiSCA LMP1, at a ground clearence that would keep the motor far away from the undulations of the Ninco track rails (≠1,6 mm) with a margin for the expected tyre wear. (hence 1,8mm)

image courtesy of www.slot32.de

Track test 1, May 14th
After all the measurements had been done it was time to put the different specs through some track testing, you know.... the proof of the pudding and all that....
Base reference times were set with the NSR C6R in DiSCA LM spec (Flat6 closed side down with 14x28 gearing), starting with the F22's that were still on the car since Henley (refurbished by trueing @ 19,5mmø) The track was a bit green so it took about 20 minutes before I reached a stable grip level.
After 30 minutes I had managed a best time of 9,72 on the F22's with average lap times in the high 9,80 sec. An other 15 min session with the Scaleauto Procomp3 noted a 9,46 sec best and mid 9,5's average. These times were about 3/10ths above what I'd done with both compounds in the run up to the Le Mans race, but the narrower spread between best and average laptimes on sponge was the same.

First steps of the Baby (Sprinter).
With the base line now set it was time to swap the Flat-six for the Scaleauto Baby Sprinter. I must say that from the very first steps this "Baby" made on the track its was immidiately clear that it had the legs to match the Flat-6. Which in all honesty isn't a fair match to make, considering that in order to "Flatten" the "six" slot.it had to shave quite a bit off the top and bottom of the motor magnets. `
The extra torque of the Baby Sprinter gives it better acceleration, and to my ears it sounded like it revved just as high as the Flat-6 on the Suzuka main straight. After dailing in the SCP2 controller to cope with the increased powerband I noticed that I had bettered my best laptime on F22's by 0,2 sec but my average laptimes had not. Unless you nailed your corner entry speed perfectly and got your brake and accelleration points exactly right the F22's struggled somewhat in handling the extra load of the Baby Sprinter's torque.

Looking for a bit more grip.
So off came the F22's and on went wheels with the NSR ultimate grips, a tyre reputedly well capable of handling a bit of torque.
Well to be honest...I was a bit disapointed, yes the compound felt softer, more grip on acceleration but not as smooth, a bit more grip on corner entry but not really constant trough the whole corner. Best laptime was higher than the F22's but the difference between best and average was smaller. Swapped the NSR's for the Slot.it equivalent and behold, the N22 performance was in many ways the same as the NSR rubber.

To be honest again, due to the time limit I'd set to prep the tyres, the large diameter resulted in a higher ride height and thus less magnet downforce. There were also some slight rubb marks in the wheelarches. Now I'm sure there's a lot more performance to be had from both compounds by spending more time on their preparation, but this is exactly what you wont have at the GT3 events.

For statistics sake I did a last test with a set of trued and glued NSR GT3 (grey) tires that had been worn down to ø 20mm.
With the smaller diameter rubbing issues were solved and the lower rideheight gave a bit more downforce.
The C6R now had a more stable handling trough the whole corner which gives you so much more confidence in attacking them.
As a result I managed to improve on the best time set on the F22's and with a much smaller difference between the best and average lap times.

Sharp level of performance... and drivebility
Time to test the Scaleauto Procomp3 sponge with the Baby sprinter and whoa, first lap a 9,38 and within 5 minutes (dailing in the SCP2) a best time of 9,25 with the ability to run comfortably in low 9,3's average. I guess had I pushed on for an other 15 minutes those times would have dropped further, so the "Sharp level of performance" was there, but that was not all we were looking for, drivability being the other main item.
Well with the sponge tyres you can dive deeper into the corners and once the car settles, immidiately start to put a load on the tyres while in the corner and thus start to accelerate before the exit of the corner. But the best thing about this run was that the car felt very safe. Even when you would exceed the range of the Motor magnets downforce there was enough grip left to catch the car in the slide.
The strenght of the sponge tyres lays in their increased lateral grip, which will be very helpfull in perfoming a succesful lane change.

Do the sponge tire have no vices then? Off course they do! Put to much load on the tyre and the sidewall will start to compress.
The first signs of you reaching that limit will be a lift on the inner rear wheel, back off quickly or you will risk pulling the car on its side and into the kitty litter.
Going for harder springs, running more on the front wheels and moving a bit off weight towards the front off the car are some of the options you can try here.

Track Power....less is more?
It had been a long day of testing but before I could close off there were still two test I wanted to do. First I wanted to double check to see how far improving track conditions had influenced the laptimes. So I switched back to the F22's I'd started with and did another 10min. run. Improved my best laptime by 0,02 sec, but average laptimes did drop by 0,2 sec. I could now comfortably run in the low 9,6 sec which now put the F22 more or less in the same range as the N22's and the NSR tyres.

During the track testing I had done on this day I specifically made no set up changes to the C6R, it ran well as it was, actually a bit too well.
Running alone on a clear track with all that power and (sponge) grip, challenged me to push harder and harder, as all I needed to focus on was..my own car.
But this situation is not representative of the race conditions during a GT3 event.
Here you will need to divide your focus between running your own car and the position of the other cars around you.
So it was now time for the last test of the day, doing some 10min. runs at reduced track voltage settings.

Running @ 11,5 volts
As you can see in the table above just, half a volt reduction in track power increased the laptimes on sponge by 0,25 sec and 0,10 sec on the F22's.
But what was more relevant, it made the handling of the Baby sprinter much more docile, requiring less focus to keep the car's laptimes at consistant level with a smaller spread.

Running @ 11,0 volts
Running at 11volts increased the sponge times by 0,4 sec. and the F22 times by just 0,2 sec.
But this power setting killed of all of the "sharp level of performance" I had enjoyed all day, and although circulating the track was now almost a no brainer...
...it did not improve the drivebility.
I actually had a couple of deslots because now you had to push the car all the time to compensate for the loss of power. And the only way to do so was to dive deeper into the corners, maximise cornering speed and and try to accelerate as soon as possible.
Now the extra grip of the sponge actually became a disadvantage, with not enough power to spin the wheels it was harder to keep the refs up and the C6R felt like as it was bogged down in sticky goo.

I would by no means claim that the tests I performed are 100% accurate and exact, or even approach academic testing...
..but they were thourough enough to give a good indication on how the different motor and tyre performances compared to each other.
Based on these test we're confident that the specs and rules of the new GT3 Open formula will provide the "sharp level of performance... and drivebility" that we were looking for.

I will continue to test some of the different cars and set-ups that can be used in the GT3 events and will post updates here.
Some of them you can already read in the posts below.

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