Track Car Debate

[Jerry]

Look at the fastest times for street cars at Laguna Seca and the Nurburgring. Z06 is REALLY fast. It's about driver skill and courage !

[Manta22]

The Chevrolet Corvette Z06 has become a world-class sports car... and at a relatively bargain price at that!

[Sulley]

For Road Atlanta the track record for naturally aspirated I believe is a C6 Z06.

[Ken Walsh]

Hate to "chime in" late, but here's my thoughts. I own a 2015 C7 Stingray, 427 ERA Cobra clone (a 428 FE mill, actually....) and my twin turbo Manta.

Here goes:

1. The Vette is a great road and gentlemanly track car. The only "downside" is that it is very refined--and doesn't take much (if any) routine tinkering.... just gas it up, set the mode to "Track" and go........

2. The ERA Cobra is a beast, and can get you in trouble if you are too aggressive with the "loud" pedal. By now, I have dinked with most of the residual things I need to do to it, but...... It is very LOUD, so best for generally short trips/tours, and sooner-or-later, you will get branded by the side pipes--as my ankles can attest. The more I drive the Cobra, the more hair I get on my knuckles......

3. The Manta is my tinker car....and opportunity to play with technology.....and performance, even with a "light tune" on the turbo's is still blindingly fast, even when compared to the Vette and Cobra.

In short: I would drink a good chilled white wine with the Stingray, a cold beer with the Cobra, and wear racing shoes with the Manta (because the foot box on the Manta is so darned tight!

If I hadn't done most of the work on the Manta myself, I'd guess it would be an $80+K car by now. But I even hesitate to add up even the parts receipts for the car!

[Blueovalz]

Contrary to Ken, I would love to chime in . Last month I ran the car on a short road course, and had made some improvements in the rear suspension and bars over the previous track time at this track. The result was better than I anticipated. There were no Vettes nor Porsches that passed me, and there were none that I couldn't catch. The most surprising aspect of the car was that the largest gains were made in the corners much more so than on the straights.

The first couple of runs were after a night of rain, so it was very slick, but by the middle of the day, the car became very stable and planted. By the last session of the day, even the off-camber turn was feeling pretty good.

[Ken Walsh]

Terry,

Thanks for the update on your track days..... At some point, I'd probably like to siphon off your geometry settings. Considering the low COG of the Manta and the wide track, are you running much camber gain over the travel distance of your front suspension.

P.S. I'm still dinking with my traction control, but I'm down to 2.7 second 0-60 times. Might only be a matter of time, before I shell the transaxle!

[Blueovalz]

Camber gain in front is right at 4.5 degrees, and rear is 3.3 degrees over the full range of suspension limits (6"). Obviously the car is not designed to run to full bounce and droop, so actual range is undetermined, but guessing around 3" to 4". The change in the rear uprights was to increase the camber gain, which helped a lot, and allowed me to reduce the static camber. Net result was a 4 mph increase on track-out, with a much better planted rear. Springs are 350 front, 450 rear, with a .72 angle correction factor in front, and .95 at the rear. Thus there is not a lot of compression on the springs at ride height. Weight distribution is 39/61. Front bar is 1", and rear is 3/4", and I'm using a mid-range setting on the arms, which is the same for both bars. Even though I designed the uprights for little sway, I think there is more going on than I planned. Not sure if that is good or bad, but the ride is excellent, both on track and on the road.

Trammeling is a problem sometimes, and I hope to have that mitigated a bit with some new uprights on the front that will reduce the scrub radius to about half of what it is now. Hope I don't lose too much input when I do that though. I felt the C4 front uprights have worked out really well, and I will keep them as a back-up just in case the new ones don't work out as intended. Overall, the new fabricated front uprights will increase the arms length by about 1.5", increase camber gain by about .5 degrees, and give me the ability to adjust the geometry slightly using spacers.

Braking appears to still be very sufficient even with "small" 12" C4 rotors. I've had to bias the front more than was designed, so obviously I've either got more weight up front (which I do at 1% from design), and/or the CG is higher than I intended. Regardless, the brakes never got soft. I've changed the rear components to Wilwood hats and rotors once I found a very close (.004" or .040" ?) match to the C4 rotor spacing, and will work on replacing the front OEM rotors with Wilwood hats and rotors later (.810" thick, 12.19" dia rotors).

Guessing the final weight of the car to be a porky 2200lbs considering all the "street" stuff that is on it that added weight (thicker body panels, latches, lots of copper wiring, gauges, fans, larger Heims than was necessary, and a general overbuilding to ensure no failures on the street. Had I set this up solely for racing purposes, a single carb, with one low-pressure pump, no fans, minimal guages, and less framing would have gotten me under 2K (well, maybe not less framing...a stiff frame can make up for a lot of other weaknesses in the suspension). I am slowly replacing steel parts with fabricated aluminum pieces as time goes on, so hopefully I'm loosing a gram here and there.

[Ken Walsh]

Camber gain in front is right at 4.5 degrees, and rear is 3.3 degrees.......

And why am I not surprised that you keep METICULOUS records of this stuff? (Ya never cease to amaze me, Ox....!)

As for "beefy weight".....adding twin turbo's and intercoolers (~40 lbs), would probably be more beneficial than taking 40 pounds off your chassis/body....


Ken

[Blueovalz]

Ken, don't think that I haven't considered it. I've got plenty of room to hang them off the headers. I love the 8-stack look though, and yes, the turbo set-up would be breathtaking in looks and performance, but for now I'm sticking with the McLaren theme.