Saturday, July 16, 2011

Nitrons - 650Nm of fun

The issue with the left front riding low turned out to be a broken left front coil-over. Given that I busted the stock one once already, I figured an upgrade was mandated and by luck I found a set of used Nitron single adjustables with 650Nm rear, 525 front springs. That's approximately twice the spring of the stock Bildstiens.

So what happens when you double the spring rate on a sports car? Well after a couple of drives to work I would say the answer is you get noticeable improvements in everything except comfort, and handling over bumps. The ride over bumps is definitely stiffer overall, though the little stuff doesn't get the car jiggling around quite as much, possibly because the dampers are better.

However, body roll is now almost non-existant. The car is much more sure feeling on good pavement. The acceleration is sharper too. When you step on the gas pedal there are only 3 things that can happen:
  1. The car can tilt. Nose up rear down, you see this in the extreme with dragsters that actually lift the nose of the car.
  2. The tires can slip. Also common in dragsters and drifters, and teenagers who mistakenly think that sliding the rear tires around has something to do with going fast.
  3. The car can move forward. Well duh, of course this is the one we really want.
Since the springs are stiffer you get less of #1 and more of #2 and #3. So the car accelerates faster, but it's a bit easier to break traction if your not careful.

Also the stiffer springs increase the tendency of the car to unweight the tires after hitting a bump, and so the inconveniently placed manhole cover at the exit from my work tends to cause the tires to chirp when I leave. It didn't do that before the change. Similarly, the car sometimes has a feeling of slightly walking sideways when turning across a bumpy surface. I had previously noticed this when I added the stiffer sway bar, and it's increased.

I also noticed that the jerkiness and bumps can make the shifter a bit more reluctant to go into gear, so I'll have to keep an eye on that. Don't want to blow shifts. That can be expensive.

Basically the car now expresses an even greater preference for smooth pavement. When you feed it what it likes, the driving is very tasty indeed.

Saturday, July 2, 2011

Top 10 !!

The results from last sunday are in, and based on fastest time of the day, I was the 10th fastest car out of 104 cars. That's top 10% in raw times! I completely blew away one of my SCCA rivals (the turbo 2.0L stroked miata with the fully custom suspension) I've never come close to that before. Unfortunately it looks like something broke or wore out on the way home however, as my left front is now riding low and something feels loose and the car wanders pulls a little bit one way or the other when I go over bumps. The last run of the day was actually my fastest time, by 0.15, but I had one cone.

Hard to compare this to an SCCA result however since the crowd is different, and the car classes don't match at all.

So next comes the repair investigation... The initial suspects are a binding shock, or a A-Arm bushing that's worn out.