COTA recap w/ Viper TA

[Nine Ball]

I took the weekend off from beating up on C7 Z06's, and my wife and I had a great time at the VOA sponsored "Bucket List" race day at Circuit of The Americas. The Viper community certainly is special, especially those who are willing to get out there and use the cars as Dodge/SRT intended. I applaud everyone that put their Vipers to the task this weekend. Also good to meet a few big names in the Viper dealership network, and to see Ralph in attendance (and racing!).

This was my first time to race on COTA, and WOW what a track! The entire surface of this track is flawless, I don't even think I saw a repair patch anywhere. Plenty of run-off room, which made me more confident to push the car hard, without fear of meeting a wall. It took me a couple sessions just to learn each turn, and with 20 of them, it is certainly a challenge. Many of the turns are blind, due to elevation changes. Many of them are also decreasing radius, which can lead to 4-wheel drifts if you go in too hot. I've had enough seat time in the '13 SRT and now this '14 TA, that I feel very comfortable with how the car communicates. I only went 2 wheels off one time, on a hot hairpin turn 20, but nothing major. This track is simply beautiful, a work of art that we get to race on. Easily the fastest track I've been on, in terms of average speed. Surprisingly technical in areas, considering it was designed for much faster Formula 1 cars.

Now about the car. Our white 2014 TA never skipped a beat, all day. I literally just had to fill it up 3 times with gas, and adjust tire pressure. The car performed flawlessly for nine 20-minute sessions, as my wife and I split duties in the car, in two different run classes. I was in the advanced (white) group, she was in the beginner (blue) group. The car never got any cool down, as my group ran right after hers did. We literally changed out drivers in the pit lane, with the car still running. After my session, it got to park for 40 minutes while other groups ran. An even greater testament, I actually went my fastest laps in the last 2 laps of each session, as I got the tires hot enough. I was out there on the factory wheels, with Michelin Pilot Sport Cups, and found them to work best at 32psi hot. At COTA, the stock TA hits 150-151 mph on the back straight, which ends with a hairpin turn. The brakes were flawless, I never felt even a hint of fade. My 2013 SRT w/ Track Pack brakes would fade a bit, on a much slower MSR Houston track. That car was still manageable, but the TA brakes are excellent. I did experience the rearend side-to-side waggle when getting hard on the brakes in this car, as some others have noted. Ben Keating said this means the front end needs more brake, which he corrected on his own white TA, with the 6-piston setup that Tomball Dodge sells. If I get more serious about racing, I may try a more aggressive pad first, as that waggle only really happened after the two high speed straights. It was evident, but manageable, didn't scare me. I tried half a session on Street Mode shock setting, and it felt sort of like my '13 SRT did. Still pretty good in that mode. But, the Track Mode was excellent, the car feels very tight and flat in this mode. I always run with all the electro-nannies in full on, as they serve as good reminders when I'm doing dumb things. They are very non-intrusive if you are laying down good lines and driving the car well. They certainly will help you avoid spinning out, should you get too brave with the throttle. Those of you tracking previous generations will probably love the Gen V nannies, as they still allow you to drive as hard as you want.

Regarding tires, I've now tracked on the Pirelli Corsa, Michelin Pilot Super Sport, and now the Michelin Pilot Sport Cup. I would rank the Corsa and Sport Cup about equal. The steering response seemed a bit better on the Corsa, to me. It just felt more crisp. After 3 hard laps, the Sport Cups start to feel greasy and I'd have understeer in some corners, which wasn't there on previous laps. I also didn't have much traction in 2nd gear on the Sport Cups, and felt the Corsas did a little better there. Both of those tires are great street-legal race tires. The Michelin Super Sports are pretty far behind both, and are sort of spooky most of the time. I don't think I'll ever track the Super Sports again. I think at this point, it is time for me to put on the Hoosier R6/R7 tires, as I think I'm at the limits of my tires now. I would also like to try the Toyo R888's, to see how they compare with the Sport Cup and Corsa.

Anyways, here are some pics, and a video of one of my 2:35 laps.





Full Gallery: http://s466.photobucket.com/user/yno...A%20Dec%202014

2:35 lap



Whew!
Tony

[fastmd]

Looks great and the car seems to be really planted. Nice job.

[FLATOUT]

Man I want to go back already! Great vid.

[viper04]

Tony
Nice video,thank for posting. Just curious was your window open during the run?

[Bruce H.]

Great recap and driving, Tony! Nice to see your wife enjoying the passion with you...now that's awesome.

What was the ambient temp that day? Pretty impressive that any street car can run that long and hard without any heat issues...and it's one of a very few.

[Nine Ball]

Windows down to point others by for passing, this was a DE day.

Bruce, 60F morning, 72F mid day. Perfect.

[Dusty1]

Great recap Tony, your driving looked great out there too and glad the TA held up. Hoosiers are like Crack Cocaine once you go there you can't go back!!! What a perfect day at what has to be one of the best tracks in the world. Hope we can set something like this up again next year.

Richard

[FrgMstr]

Awesome driving Tony, 2:35 on street tires is humping it.

[Crotalidae]

Excellent write up & great video!!!

[VENOM V]

That's a gorgeous track, I'd really like to drive it one day. Interesting to see your thoughts on the tire comparison. I've found that tires are a little like brake pads, everyone's got their favorite. For me, I liked the Corsas a lot more than the MPSCs. The Corsas felt more predictable at the limit, and they were very consistent across a wide variety of ambient temperatures. And the Corsas kept decent grip all the way to cord,whereas the MPSCs heat cycled and lost significant grip after just a couple of spirited track days. The MPSCs were useless in temps colder than about 55 degrees, which we see in the morning sessions often here. The Corsas however had decent grip. However, neither tire is anywhere near the grip of a Nitto NT-01, which has similar grip to the R888s. And of course, Hoosiers are worlds above all of them. On a scale of grip, I'd rate the MPSCs about a 6, Corsas a 7, Nittos an 8, and Hoosier R6s a 10. A6s are an 11, on a scale of 1 to 10! Hoosiers wear out faster but man do they reward while they last. And I hear the new A7s are out of this world fast from a racing bud of mine, I can't wait to try them.

Man I wish my lady got into this with me, you're a lucky man! May will haul slicks to the track on occasion, but she pretty much just hangs out in the shade and reads a book while I'm tearing it up out there, LOL.

I had the same experience as you when I tracked the Viper at Laguna Seca: 10 25-minute sessions between two advanced drivers, and the Viper had no issues with temperatures, brakes, anything. My friend Mike is a long-time track rat that has owned and tracked several Ferraris and most recently a Porsche Cup Car, but is presently track car-less. Tracking Seca with me was his birthday present, and we both drive hard. The Viper is uniquely an awesome track car straight from the factory, pretty much race ready.

Regarding the shimmy under hard braking, for some reason it just doesn't happen to me any more. It used to, but that behavior vanished and I'm not sure why. Ben Keating told me that he thought it was the differential, and was planning on offering an aftermarket unit. He ran the stock Gen V in his race car while waiting for the racing rear end. As soon as he put in the racing rear end, the shimmy went away. But he told you brake bias, interesting.

I hope to track this weekend at Buttonwillow in my Camaro, that is if the damn gremlins are done haunting it. The plan is to try and beat my Viper's time, which I don't think I'll ever be able to do in the Camaro. It's actually very fast for a Camaro with all the mods, but the Viper is the king.

Looking forward to your next write up. I am still laughing at that Hitler video, my girlfriend thought I was nuts because I must have played it 5 times, laughing my ass off!

[Bruce H.]

Regarding the shimmy under hard braking, for some reason it just doesn't happen to me any more. It used to, but that behavior vanished and I'm not sure why. Ben Keating told me that he thought it was the differential, and was planning on offering an aftermarket unit. He ran the stock Gen V in his race car while waiting for the racing rear end. As soon as he put in the racing rear end, the shimmy went away. But he told you brake bias, interesting.

Interesting that it completely disappeared. I guess the diff could affect it, among other things. Check out Nambo's suspension thread.

[Nine Ball]

Venom, I'm not sure how it could be the differential, when it only occurs during hard braking. It would seem the diff has nothing to do with that, since the brake pads/rotors take the load at that point. Interesting. I wonder if your Hoosiers removed the occurrence, basically by improving the braking traction?

[TrackAire]

Venom, I'm not sure how it could be the differential, when it only occurs during hard braking. It would seem the diff has nothing to do with that, since the brake pads/rotors take the load at that point. Interesting. I wonder if your Hoosiers removed the occurrence, basically by improving the braking traction?

Tony,

I'm not an expert on how the rear diff of the Gen 4/5 engages, but do you think there might be a chance that the diff is actually incurring some amount of engagement (in other words locking the two axles together) and quickly disengaging as the rear brakes try to slow the axles? Coupled with the anti lock feature, it almost sounds like the rear axle is getting alternating left and right brake application.

I'd wonder if getting the diff fluid hot (gets thicker with heat) in the Visco Lok makes the unit lock up too much and causes this rear shimmy under braking.

Cheers,
George

[Steve M]

Tony,

I'm not an expert on how the rear diff of the Gen 4/5 engages, but do you think there might be a chance that the diff is actually incurring some amount of engagement (in other words locking the two axles together) and quickly disengaging as the rear brakes try to slow the axles? Coupled with the anti lock feature, it almost sounds like the rear axle is getting alternating left and right brake application.

I'd wonder if getting the diff fluid hot (gets thicker with heat) in the Visco Lok makes the unit lock up too much and causes this rear shimmy under braking.

Cheers,
George

Multi-viscosity oils don't get thicker in that sense...they do go up in viscosity as the temps rise, but that's just to prevent them from becoming too watery at operating temps while retaining good cold flow characteristics. They are still thinner at operating temps than when cold, hence why you drain them hot vs. cold.

[VENOM V]

Tony,

I'm not an expert on how the rear diff of the Gen 4/5 engages, but do you think there might be a chance that the diff is actually incurring some amount of engagement (in other words locking the two axles together) and quickly disengaging as the rear brakes try to slow the axles? Coupled with the anti lock feature, it almost sounds like the rear axle is getting alternating left and right brake application.

I'd wonder if getting the diff fluid hot (gets thicker with heat) in the Visco Lok makes the unit lock up too much and causes this rear shimmy under braking.

Cheers,
George

It's a good question, I didn't fully understand it. I think it's something like what George describes. When braking hard, you are typically not perfectly straight, so if the axles lock together and/or release abruptly it may cause adverse handling issues. Dunno, it would be a question for Mr. Keating.

[VENOM V]

Venom, I'm not sure how it could be the differential, when it only occurs during hard braking. It would seem the diff has nothing to do with that, since the brake pads/rotors take the load at that point. Interesting. I wonder if your Hoosiers removed the occurrence, basically by improving the braking traction?

I was thinking about whether the Hoosiers cured it too, but I didn't have the issue when I recently tracked with Corsas at Sonoma. On the other hand, I was taking it easy when on the Corsas as it was the first time at Sonoma.

It is also possible that my driving style has adapted to the handling of the Viper and I'm unaware. It's interesting to watch a vid of yourself on track and notice quick hand movements to correct for a car that starts to get loose. Sometimes I think experienced drivers are unaware of all the little corrections they make when tracking hard, it's all muscle memory.

[Nine Ball]

Here is a good tip for you track-rats. Install one of these IPSCO throttle pedal spacers. I put one on the last car, and this TA, and it makes rev-matching heel-toe a breeze, compared to the factory configuration. I'm much smoother at downshifts, with the spacer in place. When you are hard on the brake, it puts that throttle pedal right at your heel.

http://www.ipsco.org/Viper_files/SRT...sion%20Kit.htm

Takes 5 minutes to install. Easily removable, if you don't like it.

[TrackAire]

Steve,

Makes sense but the diff is probably going to react differently to the viscosity of the oil. (I wish I know more about the Visco Lok diff and how oil effects it)

I do know that on my track Mustang with an Auburn posi, it calls for 80/90 weight oil and limited slip additive. I had my mechanic put on a new bearing pre-loading diff cover on it and he thought that a thicker oil might be better for a race car. He put in some wiz bang Lucas 80/140 with the posi additive. No issues driving around town or the first or second session of the track day. But by the 3rd session, things had gotten hot enough that the diff would not unlock. Driving into the pits, moving the steering wheel just 10 degrees caused huge popping and shuddering sounds from the diff. I did not realize at the time that it was the fluid, I just thought the diff let go. By the time I trailered the car back home and backed it out, the diff worked perfectly normal. Drove the car for about 20 minutes and the symptoms came back. Put in 80/90 weight oil (per Auburns directions) and the diff has been perfect every since. Maybe the Visco Lok is "growing" as it gets hot.

VenomV claims his Gen 5 is longer doing the rear end wiggle. His Gen 5 is one of the most tracked, so maybe his Visco Lok has loosened up due to wear??

Is there a way to pull the anti lock fuse and disable the brakes anti locks system to see if the rear anti lock brakes on the rear axle are contributing to this?

[Victxv10]

Here is a good tip for you track-rats. Install one of these IPSCO throttle pedal spacers. I put one on the last car, and this TA, and it makes rev-matching heel-toe a breeze, compared to the factory configuration. I'm much smoother at downshifts, with the spacer in place. When you are hard on the brake, it puts that throttle pedal right at your heel.

http://www.ipsco.org/Viper_files/SRT...sion%20Kit.htm

Takes 5 minutes to install. Easily removable, if you don't like it.

I installed this in my 08 and love it.

[FrgMstr]

I installed this in my 08 and love it.

Did this on my 05 and 08. Worth every cent if you heal/toe.

[XSnake]

The rear anti-toe brackets fixed a lot of that wiggle on my Gen 2 back when I had that. I don't think anyone has developed anything like it for any of the later generations though.

http://www.viperpartsrack.com/viper-...ti-toe-bracket

[XSTAR]

#jealous I need to figure out a way to start getting track time now, just know when I do I'll be an addict