J-Rho autocrosses an SRT-10 in SCCA SS class

[j-rho]

Hi All,
Using this thread as a placeholder for the 2008 season, campaigning my 2004 SRT in the SCCA's "Super Stock" autocross class.

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Most people don't think of the the Viper as a good autocross car because of its size and power, but I think there's some things about it that make it a good choice. Its main competitors are the Porsche GT3 (2007 winning car), Lotus Elise (2006 winning car), and C5 Corvette Z06 (2005 winning car). Viper Pros/Cons,
Vs. the GT3-
Pros:
Has more power/accelerates better, esp. when GT3 is "off the cam"
Is ~250lb. heavier but has much better tire/weight
Is better balanced overall
Cons:
It's much much wider
It doesn't put power down as well

Vs. the Elise-
Pros:
Accelerates better, esp. when Elise is "off the cam"
Probably better in sweepers
Cons:
MUCH heavier
MUCH longer

Vs. the Z06-
Pros:
Puts power down better
Shorter wheelbase = more maneuverable
Better wheel and tire per weight
Cons:
A bit wider
Not as good 2nd gear acceleration when under 55mph

Also, I tend to focus on the "ProSolo" series within the SCCA a bit more than others. These events feature a drag-race start, where I believe the Viper's great traction and 1st gear acceleration will be of large benefit.

As a bit of background on myself, I started autocrossing in 2002 with my Honda S2000 in the "A Stock" class. I did pretty poorly that year at the National Championship, finishing near the back of the pack. The following year I did a lot of driving at autocross and track days, including the Open Track Challenge, where I got to hang out with some cool people like John Dearing, Ron Wasserman, Paul Mumford, and Brian Provost. Doug Hayashi, Erik Messley, and myself won Touring 3 in Doug's Honda S2000 sporting a moving wing I built:

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I also finished a close second in Dave Kennedy's Unlimited 2 class Honda S2000, which we'd swap the wing on to between sessions:
[media]http://www.jrho.com/track/willowfastlap.wmv[/media]

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That year I also built-up a friend's Honda Civic for the "STS", in which he won his first National Championship, and I finished a much better fourth.

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2005 was pretty interesting, I co-drive with multi-time National Champion Gary Thomason in his 600hp Corvette (with stock Z06 gearing!). That was my first time in a properly powerful car a real eye-opening experience. Gary won nationals that year and I placed a decent third, ahead of some guys I thought pretty highly of, including Viper racer Scotty White.

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Having done pretty well I decided I needed to race my own car again to get "first priority" for winning. So I bought a Nissan 240sx, built it up for the STS class I'd built the Honda Civic for, and managed to win the 2006 National Championship in that class.

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Having been bitten by G-Tho's powerful Corvette in 2005, I wanted to get back into something with some balls. In a bout of bizarre logic, I thought the easiest way might be to make the 240sx faster, after all, all the drifter guys were doing it. So I slapped on a big turbo, a stout clutch, killer diff, and some monster wheels and tires. The result:

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and a quick autocross lap:
[media]http://www.jrho.com/sm240/jrhos.wmv[/media]

That car was a blast but with a diet of race gas and life as a trailer queen, it was also a bit high-maintenance. With some life changes going on I sought something just as fun but a bit lower maintenance. It just so happened that the aforementioned Viper racer Scotty White had his mamba for sale, so we made a deal, and I went and picked it up from him in Washington.

It took me a while to get it ready and back into a healthy "Stock-class" trim. We are only allowed to change the fron swaybar, cat-back exhaust, tires (must be DOT approved) and wheels (must be stock width and diameter with offset within 1/4" of stock). So I built my own beefy front swaybar, ordered some CCWs, and kept the completely mufflerless exhaust it had from Scotty.

At the first event with the car put together, on my second run, I was within a couple tenths of a second of what will be my toughest competition. Needless to say, there is bound to be some "time" I've yet to find in setup and learning to drive the car better (as the video below clearly shows). This looks to be a very promising year for the Viper in SS...
[media]http://www.jrho.com/viper/viperclip1.wmv[/media]

Thanks for reading everyone, wish me luck!

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[rcl4668]

Jason --

Thanks for posting the awesome pics and video. I will be very interested in seeing your results as I hope to partcipate in some novice SCCA Oregon autocross events this summer.

Good luck!

/Rich

 

[Alan Patterson]

Since you now own Scotty's old Viper, you own parts of my VOI-9 coupe! Scotty and I traded his delrin bushed control arms for my stock ones which are now on your viper. FYI, I am a pretty serious autocrosser running in ASP. I have done nearly all that can be done to the car in the street prepared class: quaife diff, light weight flywheel, Corsas, Hi-flow cats, Extreme alignment (very low with 3 deg front/2 deg rear camber for A6 Hoosiers) Moton shocks, etc.
I have found that the stock swaybar works pretty well as long as there is enough stagger in front/rear tire pressures. Only thing left is headers which may or not be needed...

Prior to going to the ASP setup, I tried my car in SS class for a few events and found that the shocks/springs just didn't work well enough and the rules say you can only use "stock length" springs which means custom built shocks to mate with the "tall" springs. Also, I found that the stock positraction just did not work well. You will find it locking up suddenly when trying to put power down coming out of corners. (Oddly enough my old gen2 viper did not have this problem) the quaife diff solves this problem.

Anyway I hope you are successful in your endeavors and perhaps we can meet one of these days. I plan to run the Calif tour events and pro solos plus the Nationals this year.
Good news is I have a co-driver who is a previous BSP national champion to help me along. He will probably beat me most of the time, but it will be a good to learn from him!
Send me an email if you want to chat about autocrossing our vipers...
Al Patterson

 

[Alan Patterson]

I just noticed you live in the San Diego area... I will see you there at the tour event in 2 weeks! Last time I was there (2006 Tour event) Scotty took first place in ASP in your car! I came in "mid pack" in my old '98 GTSR...
Al

 

[j-rho]

Hi Alan,
I see you've got Harold Olsen co-driving with you. Harold is a great guy and a fantastic driver, it'll be very interesting to see how he does in your car.

Unfortunately (or fortunately, depending on the point of view) Scotty swapped out those nice delrin-bushed arms for some stock arms before I took delivery of the car. Those bushings wouldn't be legal in Stock class.

I have found the car works quite well with the big front swaybar I put together. Remember, with the stock springs, shocks, and diff, (Stock class rules) we only have a couple things to work with.

I'll be interested to see how your car works in ASP trim, and how close you guys can get to SS times...

 

[SnakeInTheGulf]

Jason
Great post! I'm really rooting for ya! As a true novice that I am 4 events to date, and I don't like losing at anything, especially in a Viper, I'll be following your progress! Good Luck!!!
By the way what tires do you use?
Thks Larry

 

[j-rho]

I use the only competitive R-compound tire out right now that fits stock-sized Viper wheels, the Hoosier A6.

 

[j-rho]

So we finished the first big event of the year, the San Diego National Tour.

Life's been busy so I thrashed to get the stock diff in the car on Thursday night. That was a bit trickier without a proper ball joint separator, but I got it done eventually. The car had performed brilliantly with the racing diff in it, and I was hoping that because of the rest of the setup, that the car would be similar with the stock diff.

Boy was I wrong!

Saturday was a real mess. I had to stand on my first run, leaving me in fourth. A couple course workers said I was leaving the longest black streaks they'd ever seen at an autocross, on the track's two big (by autocross standards) straightaways. Where the car would squat and accelerate before, it was zinging the inside tire, and the off-camber sections made it tough to get the rear tires evenly loaded.

I started to get the hang of it on Sunday, and got a better feel for how to get the car to work. I went for a hail mary on my last run, and might have actually pulled it off but for a single (big) mistake. The class was slow overall, but overall I was pleased with the showing.

I'll be playing around with the diff fluid before the ProSolo in 2 weeks. Better lockup will make this car a TON faster. My first experimental brew definitely wasn't getting it done - the diff never locked up.

Results:
SCCA - Results

Couple pics, please no 4x4 jokes... :

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Will report back in two weeks after the Pro!

 

[j-rho]

The ProSolo this past weekend went...okay. Still getting used to the car. The new diff fluid worked fine - it's still not nearly as good as it was before with the race diff, but the different fluid definitely worked better, and overall the diff felt like a regular viscous.

Biggest problem was I drove pretty poorly. In particular, I had no "clean" runs on the right course, and it's hard to do well when that's the case. Results:
SCCA - Results

I collected a lot of data with my DL1 data acquisition system that I can review and lament how much time I left out there. I also rigged up a very un-Viper-esque camera mount at the last minute that also served as a mounting plane for the GPS antenna.

Here is a "blooper" run, from Saturday morning. My front tires still had some crap on them from the previous event - plus I was still getting used to the course, which felt about 25% smaller than how it walked. I ended up overshooting a lot of things...
[media]http://www.jrho.com/viper/ElToro_blooper.wmv[/media]

This video is from Sunday morning, similar temps but the course and tires were both much cleaner, and I was a bit more comfortable. This was a super conservative run, though in that conservation I managed to hit the first right-side apex cone after the start straight. Oh well...
[media]http://www.jrho.com/viper/ElToro_SunRight.wmv[/media]

I'll try to follow up with pics as they become available...

Oh, another blooper - this was my very first run on totally cold and dirty tires, a total mess. Look at how badly the GT3 kills me at the launch:
[media]http://www.jrho.com/viper/eltoro_cackle.wmv[/media]

 

[SnakeInTheGulf]

hey Jason
A 4th and a 3rd is pretty good in a new car!!! Love the updates. How about picking off that Lotus Elise next event! You'll get that Porsche GT3 soon!
At least you have the Vettes down, I still can't catch the ones here in my local event
Larry

 

[SnakeInTheGulf]

Jason
Another question what wheel alignment do you use?
Thanks larry

 

[j-rho]

Front
Camber: -2.5
Caster: 6 degrees
Toe: 0

Rear
Camber: -1.25
Toe: 1/8" in

 

[rcl4668]

Jason -- congrats on your results thus far. Just a quick question: what would you recommend running as cold tire temps for a novice autocross? What hot temps should one be shooting for? The Viper in question has the Michelin Pilot Sport PS2 tires on stock size rims and no suspension modifications. The literature from the SCCA novice school recommends filling up all tires at home to the maximum sidewall pressure (which is 51 psi -- yoiks!--for the PS2s). I would rather not do this for safety reasons. Is this really nececessary as I will be bringing a compressed air tank to the event? Thanks for your help!

/Rich

 

[j-rho]

Hi Rich,
I don't know much about the PS2s, I've only ever had the old-school runflats or Hoosiers on my car. In any case, I don't recommend running those tires that highly inflated on your car, especially in the rear. I'd try something like 32 rear, 37 front. They'll go up a few pounds as you're running, but you aren't likely to notice the difference.

The SCCA recommendations were written with an "average" car in mind, the sort with really awful suspension geometry that gets around with skinny, high-profile tires.

 

[rcl4668]

Thanks for the recommendation Jason. I'll start with 36 cold front and 32 rear and see how it goes. I don't have a tire pyrometer yet so does the low tech approach of using a dot of white shoe polish at the sidewall/tread edge still work?

/Rich

 

[j-rho]

You can do the shoe polish thing if you like. If you look closely though, you should be able to see how far the tire is rolling over.

What alignment are you running and what's the suspension setup? How about wheel/tire sizes?

 

[rcl4668]

You can do the shoe polish thing if you like. If you look closely though, you should be able to see how far the tire is rolling over.

What alignment are you running and what's the suspension setup? How about wheel/tire sizes?

Thanks, then I'll skip the shoepolish.

Alignment and suspension are all factory stock for a 2008 Viper. The only change that might affect the suspension is the use of lighter weight "Sidewinder wheels" in the stock 18 x 10 and 19 x 13 sizes and the use of lighter weight stoptech aerorotors front and rear. Altogether, this saves about 60 lbs but I put back about 30 lbs with the install of an Autoform rollbar.

/Rich

 

[j-rho]

The shoepolish looks ok on a teenager's Civic, not so cool on a grown man's Viper.

I highly recommend getting the car aligned before the school. I think it'll make it a lot more fun, and will actually be nicer to your tires overall. The alignment I use would be good, though you may want a hair of front toe-in, and maybe also a little more toe-in in the rear, to make the car a bit more stable. My car turns great at the autocross but is very darty on the street. If you plan to put a ton of street miles on the car you could compromise with less front negative camber, but based on what I've read, I think you'd be best off with it maxed out.

Have fun!

 

[SnakeInTheGulf]

Jason
You haven't posted in a while, any new results? I tune in all the time just for more info!!!
Thanks Larry

 

[j-rho]

Hi Larry,
Nothing to report as of late. Been very busy with work and buying a new house, so time and funds for racing have been less than ideal. I plan to attend a local event later this month, another local event in July, the Wendover ProSolo in August, and the National Championships in September. Normally I'd be attending 1-2 events every month but it's just not in the cards this year.

Speaking of which, if anybody with a stock 2008 (especially one with the aero package, but not an ACR) is interested in teaming up for a trip to Nationals, let me know. I'll supply the wheels, fresh Hoosier tires, and the front sway bar, you need only supply the car. If you're somewhere between San Diego and Topeka and I could even trailer it there and back.

Going to the National Championships is a tremendous driver education. I think my '04 can win, but an '08 would be even better.

 

[j-rho]

2008 recap-
Ran the Wendover ProSolo last August, did okay but not great. Ended up not going to Nationals due to purchse of new home, and not having many ProSolo points.

2009-
Signed up for San Diego National Tour in March, as well as the El Toro and Alameda ProSolo events in March and April. Will be trying the 335 front tires instead of the current 315's, and will try to get some mufflers on the car to combat the sound issues I have at my local autocross venue.

The National Championships have been moved from a small asphalt lot to a postively humongous concrete site for 2009. This can only be a good thing for the Viper against the 911 GT3 and Elise competition. Should be a fun time, hope to get a bunch more seat time this year.

 

[j-rho]

This past weekend was the SD National Tour. As part of a codrive deal, the Viper was parked, and I co-drove with the class's 2008 National Champion, Gary Thomason, in his winning Porsche GT3. He will be co-driving the Viper with me next weekend at the El Toro Pro Solo.

I had never even sat in a GT3 before my first run on Saturday morning, so I wasn't sure what to expect. The car is actually pretty easy to drive, it generally wants to understeer and puts its power down well. The tall second gear really hurts its acceleration at autocross speeds - with a 20% shorter second gear, it'd be untouchable. The suspension is fully adjustable from the factory, so it handles more like a race car than the Viper. Still, the Viper is more fun to drive.

Saturday the car was a handful, and we never really got it sorted until Gary's last run. Sunday it was better and I was able to run within a couple tenths of the leaders.

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(even the GT3 has trouble putting power down on grass )
Looking forward to putting the hurt on 'em next weekend in the Viper! Got some fresh tires mounted, should be a good one.

 

[j-rho]

So we did the El Toro Pro Solo this past weekend. Tried a new tire setup, 315/35-18 front and 335/30-19 rear Kumho V710.

Initially the car had a bit of oversteer on the new tires. We made a pretty big toe change (more rear toe in) and that made it better. We probably went too far, and were dealing with a bit of understeer, but still had some yucky scary oversteer under braking. Car maybe needs more front bar. Definitely needs adjustable shocks too, I'm still running the stock pieces, will be researching options. The off the shelf stuff like KW or Moton is built and valved to work with the spring rates they provide, not to try and manage the porpoising fat heavy car with big sticky tires and stock spring rates.

Here's a video of a right-side run, it's pretty much a hack of a run. I'm using the new Dashware software from Chasecam (Solid State Digital Video Recording Systems and Cameras | ChaseCam) to combine video from the Chasecam video system, with the data acquired from the DL1 data acquisition system. This is a really basic representation, there's a lot more that can be done.
http://www.jrho.com/jason_et_right.wmv

Wendover ProSolo is in 4 weeks, hope to have some stuff sorted by then.

 

[j-rho]

Here's a couple pics from the ProSolo.

This is Gary Thomason (who drove the autocross portion of the Road & Track super-car test last year, including the Viper ACR) somehow picking up a front wheel. The car has a stiff front bar but this exceeded what I thought the car would do. The grip levels were very good.

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And one of me, not as interesting-

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[rcl4668]

Thanks for the updates.

 

[j-rho]

Hmmm, I moved web servers, and would like to fix my first post in this thread, but can't edit it. Oh well.

I'm on a mission at the moment to get some shocks built for my car. As stated above, I am running in Stock class, so I have to stick with the stock springs and ride height, and I have limited freedom over final fully extended length. Because of this, the most common options for Viper racers (Motons, KW, etc.) won't work because they're designed from a dimensional and valving standpoint to work with rather different spring rates.

Based on my experience thus far on stock shocks, I actually think the rears aren't *that* bad. Sure, some adjustability would be nice, but I think they're in the ballpark. Because of this, I had a rear shock dyno'd (engines aren't the only things that have dynos! ) to see where they were, as I'd like the new shocks to posess a place in their adjustment range that roughly approximates the present rear damping.

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This is actually a pretty nice curve for a factory shock. The curve centered at 0 applies to rebound, the other bump. Both curves are fairly linear.

The place where I think the car is going to undergo a big change is in the front, particularly rebound. My impression of the stock front damping is there's a marked absence of rebound - this helps the car launch and put power down well, but makes it kinda dodgy in some of the common autocross maneuvers we experience.

 

[j-rho]

Front shocks were completed today and should be on the car tomorrow night.

Fortunately, a dyno run of the front shocks validated the driver's feelings of how they felt and were likely to look when graphed. This is good news, as the different damping characteristics of the new shocks should be a big improvement in the car's autocross-ability. Being that we're racing in "Stock" class, there are very few adjustments we're allowed to make, and damping is one of them.

 

[j-rho]

Well, the Wendover Pro went pretty well I guess. The car won by a staggering 1.8 seconds! Unfortunately for me, it was with my codriver Gary Thomason driving. I drove really poorly, the worst I've done in a long time, and ended up fourth.

At least the car was fantastic! The new 28-series Koni shocks put together by ProParts USA were terrific. The course featured a ton of slalom cones and other transitional elements, and the shocks helped the car change direction extremely quickly, while maintaining its composure. The valving I specified was right on the money. A pretty amazing transformation from how the car was just a few weeks previous.

Here's a couple videos of Gary, one from each side-
[media]http://www.youtube.com/watch?v=0WzqsMTjBJg[/media]
[media]http://www.youtube.com/watch?v=xuwp9awrY14[/media]

There's still a few things I need to get sorted out, including replacing the limited slip, which is completely worn out at this point. This is a call to everyone with a Quaife or other aftermarket diff in their car - I want your stock diff! Particularly if it is low-miles/hasn't been abused.

Thanks everyone, will update again probably around Nationals time in September.

 

[j-rho]

Did a local event yesterday with a fresh limited slip in the car. The power-on behavior was much improved, with little to no wheelspin anywhere. Think I finally got the cocktail right.

Unfortunately the tires, rears especially, were at the end of their useful life, so the car wasn't as fast as it could be. Still, it worked admirably and was as much fun as ever.

[media]http://www.youtube.com/watch?v=QN4kvVsQOnQ[/media]

 

[j-rho]

Unlocking the Hydra-Lok

As mentioned throughout this thread, I'm racing (well, autocrossing) my car in a class where I'm not allowed not change out the limited slip. As such, I am interested in maximizing the capability of the factory Hydra-Lok unit, as autocross puts just about the most extreme demands upon LSDs a car will ever see.

With a fresh spare diff in the car now I was able to dissect the one I'd had in it. I bought my car with a Quaife in it, and had to switch back to a stock one. The used stock one had an unknown history, so it may have been slightly worn when I got it. The last few events the car was getting really bad inside wheelspin, telling me it was probably toast.

There's been a lot of stories and confusion on the Internet about what kind of diff (found stock in all '03-'06 Vipers, and lots of Jeep Grand Cherokees) it is, how it works, etc. Hopefully this can clear it up a bit. I think the mystery is partly due to the Chrysler factory not providing any details of the unit's operation in the factory service manual. For both Cherokees and Vipers, if the unit is malfunctioning in any way, the suggestion is to replace it, as it's not "field serviceable". Here's a cutaway pic I snagged off the 'net:

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Having now taken mine apart, I'm actually a little surprised by the don't-field-service stance. At the heart of it is a pretty standard limited slip clutch pack with a somewhat disappointing total clutch area. There are 6 axle-side and 6 diff-side friction plates, the friction material is about 1cm in width at about a 5" diameter.

The real magic of the Hydra-Lok is the piece standing on its side in the pic below - the hydraulic piston. A difference in wheel speeds side-to-side causes the oil pump (guts in left half of bottom row) to turn, which sends oil pressure to the piston, pushing it out, forcing together the clutch plates. Unlike a normal clutch-type limited slip, there is no initial preload on the clutches, and the force pressing them together is not at all torque-based. It's also different from a pure/regular viscous (as in the 2008 and newer Vipers) - a regular viscous will have its clutch plates isolated in their own sealed unit, with a special and usually silicone-based fluid separating them. When the clutches move relative to each other, the special fluid heats up and gets rapidly more viscous, binding the clutches together. The Hydra-Lok is like a viscous in that it is wheelspin-actuated, but from there on it's like a regular clutch-type.

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I'll be getting a few more used limited slips soon, so I'll have something to compare to for the clutch plate thicknesses. The clutch plates in mine looked pretty worn but I'd need to see a new or new-ish one to see how thick they should be. Additional wear to the clutch plates will require more fluid displacement before the clutches would engage, critically delaying the limited slip action.

It's probably a good thing the car was one-legging recently, as there was a more serious problem lurking-

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Again, hard to say if I did that or if it was already like it when I got it, but that spider gear tooth is gonzo. This side gear is also showing some troubling wear:

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I drained the fluid pretty thoroughly but still found several metal hunks in the housing once it was apart. Having turned a lot of wreches I generally have a pretty good "mechanical sympathy" for cars when behind the wheel and have never really maimed one like this before.

Going forward I have a pretty good idea of what I need to do to keep these things working right. Didn't really have any wheelspin issues this past weekend on my home lot in San Diego, where traditionally the problem has been its worst.