Nate hammers through Turn 3.
Photo by UniqueAngle Photography
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This weekend the Cobra handled better than it ever has, and we got our best Time Trial result yet!
Nate beat the class leader, James Garvey, for the first time ever, and scored a fantastic second place. Nate's 1:16.57 beat James' 944 Turbo S by 50 thousandths! I was only three tenths back in 4th place with a 1:16.89.
The winner was Leos Kubec, back
from "new baby retirement" for the first time in almost
two years. Although his best this weekend was a 1:16.1, Leos holds
the COMSCC
class record at 1:11.7, set two years ago in his monstrous 400+
hp winged Porsche 911 Turbo. We're going to have to raise our
game to compete with Leos!
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I made two significant changes to the car before this event:
1. I had Doug Arnao revalve the rear shocks to correct for a measurement error Nate and I made which resulted in valving that was too soft.
2. I relocated the steering rack to correct an Ackermann problem inherent in the FFR design (see sidebar).
The steering rack location gave much improved feel. It's lighter on center, and the car reacts more quickly and precisely to steering inputs. In the parking lot when the steering wheel is turned far away from center, the steering gets a little heavier, because turning the inside wheel more increases the jacking effect due to kingpin inclination, but I can live with that.
Revalving the rear shocks made the car more stable as a platform, with less pitch under braking and throttle transitions. It also somewhat reduced the understeer, but we still had too much. Nate came in from his first session and said, "it pushes everywhere."
I had anticipated this possibility and had a stiffer rear anti-roll bar on hand. We put it in, but even its second stiffest setting made little noticeable difference compared to the softer bar. The car still understeered far too much for Nate's taste.
Saturday night, we took the anti-roll bar arms off and took them home. We drilled another hole in each of the anti-roll bar arms, allowing us to go significantly stiffer on the rate.
Unfortunately it rained cats and dogs Sunday morning (starting about 5 minutes before our first track session!) so we didn't get to try the new setting in the dry until the Time Trials in the afternoon.
Fortunately, the new setting seemed to hit the nail on the head! We still had power understeer in the very slow Turn 3, but elsewhere, including the all-important Turn 11, the car was quite neutral. It was beautiful! Both Nate and I smashed our previous personal bests on the South Oval configuration; Nate took off over a second.
Tire temperatures suggest that we need more camber on the front wheels, because the outside edge is still running hot, so the main tweak for next time will be to relocate the upper shock mounting point. This will give more clearance to the upper control arm to allow us to get more camber and/or caster.
Once we get the front tires working their best, we should be able to back out a little on the rear roll stiffness, so more overall grip should result.
Set up the way it is now, our Cobra is more fun to drive than ever - and it takes less effort, especially when you're going fast. It is very, very forgiving at the limit. It's so much fun it almost feels like it should be illegal!
The car's steering response is crisp, linear, and direct, and its balance is quite neutral. It rotates like lightning on demand. If you overcook it a little going into a corner, it just slides sideways a bit and then hooks up again. Response to the throttle is just to squat a little bit and go.
Many people came up to me during the weekend and remarked about how great the car looked out on the track. One person told me, "yours is the only Cobra that's handling - and it's the only one that has no horsepower!"
Amazingly for such a competent competition car, our Cobra is also a sheer delight on the street. It's comfortable, smooth, nimble, fast, and it sounds glorious.
Except for the paint job and some welding and machining, Nate and I have done all of the work on the car, but the credit for the suspension redesign and tuning strategy goes to Doug Arnao. Doug, you're a genius!
A number of other people have contributed to various aspects of the suspension and brake changes we've made, including Bruce Allen, David Borden, Gary Cheney, Doug Milliken, Mark Reynolds, Jim Schenck, Brad Pelletier, and Wayne Presley. Thank you, guys!
At Summit Point I was lucky to get to drive Gary Cheney's new FFR Spec Racer and the 375 hp Roadster belonging to FFR engineer Jim Schenck (the same car that took second at Loudon in August). This weekend I got to drive Terry Shank's supercharged FFR Roadster, and Hank Dondero's, powered by a 350 hp crate motor. Both have had their suspension massaged by our suspension guru, Doug Arnao, and both handled well - far better than stock.
Terry's car has a 302 with centrifugal supercharger, aluminum heads and all the good intake and EFI bits. It makes 450 hp at the rear wheels - which is nearly 550 at the flywheel! This engine has enormous power at the top end, but I found it to be scary to drive because of that. At low RPM it feels about like our motor, but as the boost comes in the power goes up exponentially. Above 5000 RPM it feels like you are strapped to a rocket.
This is thrilling, but I don't feel it's optimal for road racing. Terry was my student this weekend. He is driving very well, but he was not as quick as the less powerful FFR cars. Granted, he'll get faster with more experience at Loudon, but I think it would take a very experienced, very skilled driver to drive that car to the limits of its potential. A tiny bit too much throttle at the wrong moment - even failing to roll out of the throttle at the proper rate as the power starts coming in midcorner - and you are going to be in the fence.
Hank's car is a special: a FFR Spec Racer with IRS. Spec Racers come with a live axle, but Hank wanted the ultimate FFR car for SPA, so he ordered a special chassis from FFR which combined the rigidity of the Spec Racer frame and roll cage with the sophistication of independent rear suspension - and added a honking motor.
Hank's car has the spring and Bilstein shock package from Doug, but it still had the 800/500 springs and softer rear shock valving that we started with, due to our original error in measuring the rear motion ratio. As a result, it feels a little softer and doesn't handle the bumps in Turn 10 quite as well.
Hank has a crate 302 rated at 350 hp at the flywheel, and it's very docile and comfortable. I really enjoyed it, despite the rear suspension, which felt slightly squishy compared to our car's, and steering which is a little less crisp than ours.
I think our car with that much power would be fantastic! Actually I think our car could handle significantly more power, as long as the torque curve was reasonably linear.
Anyone want to donate a nice set of aluminum heads or some big-breathing EFI bits to our cause?