Ariel Atom Autocross Development

[762]

No new updates on setup while I wait for eventually getting new shocks (car is so slow in slaloms compared to steady state), just still been enjoying the improved grip of the RE71Rs vs R888s.

Had a night autocross this past weekend, which with the Atom's "excellent" lights was a unique experience. Still good enough for 2nd fastest overall time behind the national champion winning DM Lotus so I am content with the result.

(GoPro is bad at night so recommend increasing the resolution quality)

[762]

After missing a few events I got back out in the Arizona heat. Decided to just to throw the car around in the afternoon in time only runs to see what would stick and found some more pace even though I picked up some slalom cones. Lack of compression in the shocks still makes transitions inconsistent. Just waiting to hear back from TMI on what EU Ohlins might be available.

[762]

We had a 4th gear autocross yesterday. Really shows the short gearing, but longer gears are low on the priority list of things to fix. New Christmas presents are on the way.

[762]

Well it is now the off season so I have a pretty exciting development for the car.



These are Ohlins ILX36s as found on the UK Spec Atom 3.5R.

The UK car typically comes with the following spring rate pairings:
Road (F/R): 52nm/70nm [~285lbs/399lbs]
Track: 60nm/80nm [342lbs/456lbs]
Optional: 70nm/90nm [399lbs/513lbs]

For reference the US Atoms come with the following:
JRIs: 50nm/60nm [285lbs/342lbs]
Spec Race Atom QA1s: [400lbs/500lbs]

As my car is used primarily for autocross, where managing body roll is so critical, I opted to first try the 70nm/90nm setup. Ohlins was a pleasure to work with as we worked through 5 different valvings until we found a setup that I hope will provide enough low speed compression for autocross compared to the OEM valving without being unnecessarily stiff.

For reference here is a dyno plot for the Moton Clubsports used on my prior S2000:


Below is the first OEM valving plot for the Ohlins


Next is the first adjusted valving for my stiffer spring rates vs stock


Next we explored how the ranges could look if we tried to add even more low speed compression


Part 2 on next page

[762]

Adding low compression did not as greatly increase high speed compression. So I asked to go extra stiff on low speed to see what it would look like.


I thought the last valving was a little too stiff in high speed, and that it was unlikely that I would need that much low speed force, so I told them to soften it to a knee at around 225-250 and they came back with this final valving which is what I will be trying on the car.


If this ends up being too stiff on high speed I can either send them back for a re-valve, or add a high speed adjuster which gives a massive range of adjustment.

I can't wait to get them on the car in the new year and to see how the car drives and will report back then.

[MadMaxAtom]

Good info! Keep it coming..

[762]

One additional plot for reference. Here is what the highest compression valving would look like if it also had an adjuster for highspeed compression to make it a 3 way. The range of adjustment would be huge.

[Chris McCarthy]

This thread needs to be resurrected.

[762]

This thread needs to be resurrected.

I know, just been backed up at the office. That being said I have 2 events on the ohlins setup.

I will post my notes and updates sometime this week, but in the meantime here are some videos. General impressions are that body control is greatly improved, especially in transitions. However, shocks are likely too stiff on the valving. Springs may also be too stiff as well. However, my initial feeling is that it is the shocks that will need to get revalved.

First run on Ohlins (BUMPFEST)


Later run with car on full soft (still too stiff for surface)


Smoother site at other event (FTD at the event, but was in time only runs) + new camera mount

[timcking]

Some additional info for anyone interested in autocrossing and street driving their Atom. I've got a 2009 Atom 3 with Wilwood brakes. It has always taken a lot of effort to lock the brakes, so I researched the OEM pads. It turns out they were Hawk HPS compound. In talking to a Hawk tech rep, they recommended the HP Plus compound. What a difference. I can now threshold brake. Big improvement. As a result, discovered I still had too much front brake bias. Made another adjustment to transfer bias to rear. This last adjustment amounted to three (3) full turns from the OEM setting as delivered from the factory.