SRT differential gremlins at the track?

[Gforce]

Heard some very concerning comments from Scotty White this weekend that I wanted to get some more input on. Scotty campaigns a comp coup in SCCA.

He warned me to watch out for the SRTs on the track because the way the limited slip operates. It sounded prone to snap oversteer once the loaded wheel got to spinning.

really scared me so I'd like to get some input from any of you that actually track the cars.

1. Is this a severe problem?
2. Can it be overcome by driving style?
3. Does an SRT really need a new differential to be competitive at the track? My hope is that the $85K Viper would be already set up for track days.

thanks in advance -
j

 

[KaiPL]

Yes, the LSD isn't ideal.

No, it is not a "severe" problem. I drove my car at the track a lot with the stock LSD.

Yes, the issue can be overcome by driving style. You just need to be a bit more careful on corner transistions, and go easier getting on the throttle coming out of sharp corners.

Competitive with what? With practice and driving skills, your stock SRT will kill most anything at the track that has a license plate. You don't need to replace your differential (or anything else except the oil pan) to go fast at the track.

Track day modifications:
#1 Professional instruction.
#2 Roll Bar
#3 Comp coupe oil pan

These three are, in my opinion, really mandatory if you are going to do any serious track day driving. The roll bar could save your life, the oil pan could save your engine, and the instruction could help you go faster and keep you out of trouble in the first place.

After these three, you can look at modifications to help you go faster.

First on my list would be track wheels and tires. SSR Comp wheels and Michelin Pilot Sport Cup tires will make a big difference in lap times. Probably more than any other change you will make to your car.

Second, replacing the stock LSD with a Quaife differential will help smooth out corner transitions, and help you get the power down earlier and in a more controlled fashion.

After that, it's really up to you where to go. The stock suspension is actually pretty ideal for the track (its on normal roads where its shortcomings are revealed.) Some folks mod their engines for more power. I haven't yet felt the need, but this may well change before long.

Look at the mods in my signature. Most all of them were done to make my car faster at the track. The two that made the biggest difference in performance were tires and differential.

So, bottom line is that the car is plenty fast as it came from the factory. The stock differential is not ideal, but the car is still a track monster even with a mediocre lsd. There are other track day mods you should consider before replacing your dif.

 

[Janni]

Scotty is campaigning an SRT - NOT a comp coupe. He runs in SCCA T1 which mandates only slight modifications to a street car - mostly safety related.

The diff is definitely a weak point in the way it works. The Comp Coupe runs a Ricardo diff.

I can't see driving style making a difference.

If you were going to use sticky tires, I'd definitly upgrade to either the Comp Coupe diff or the Quaiffe.

But if you are gonna track the car - you have other more serious issues to contend with - such as roll bars and a decent oil pan - before changing out the diff.

 

[Gforce]

Kai -

thanks for the quick response. Appreciate the help.

interesting comment about the stock suspension. Seems like it is a bit soft for track but based on your comments, it sounds like it works well?

Also, does the soft suspension help or hurt the LSD issue? I can't sort it out in my brain. On one hand, it seems like a stiffer suspension would be a good thing but on the other hand, it seems like a harder suspension would cause the inside wheel to lift more - therby exagerating the LSD issues?

thoughts?

 

[Gforce]

Janni -


I was at the rose cup races with scotty last week and both he and cindy were driving comp coupes. I know scotty was going to get an SRT set up for solo but I don't know if this happened or not.

As far as the sticky tires, can you help me understand why those make it worse? Inhernetly, I was thinking that the stock tires would make the inside wheel slip more; thereby making the LSD stuff worse.

thoughts?

 

[KaiPL]

Kai -
thanks for the quick response. Appreciate the help.
interesting comment about the stock suspension. Seems like it is a bit soft for track but based on your comments, it sounds like it works well?
Also, does the soft suspension help or hurt the LSD issue? I can't sort it out in my brain. On one hand, it seems like a stiffer suspension would be a good thing but on the other hand, it seems like a harder suspension would cause the inside wheel to lift more - therby exagerating the LSD issues?
thoughts?

Remember that the "soft" stock suspension is designed to work with the street tires. If you tighten up your suspension, and keep the stock tires, the car will handle better up to a point, but you may find that the quicker suspension response can overpower your grip, making the car (even) less forgiving.

I got my suspension set up done while I was still on stock tires and with the stock dif. I put in stiffer springs, motons, and comp coupe sway bars.
The car definitely became more "lively" but the stiffer suspension magnified the limitations of the stock tires and differential. The car was very responsive, but also tended to be more prone to sliding rather than gripping, if I wasn't careful at the limit. The "hopping" of the stock differential in tight corners also became more evident.

To compensate, I kept the Motons set pretty soft, so the suspension had more compliance. This helped quite a bit, and the car handled very well, but I wasn't taking full advantage of the capabilities of my suspension.

Raising the level of grip by using sticky tires, and smoothing out the inside wheel spin and lock with the Quaife differential really evened out the handling equation, and brought the whole car back into balance. I can tighten up the Motons now for the track, and the car becomes more "crisp" but still very controllable. The grip of the tires is matched to the stiff suspension, and the result is a car that really carves the corners well. When the car is on street tires, I dial the Motons down for better grip. When the car is on the Sport Cups, I increase the stiffness. It's a good system, but all the parts have to work together or it won't operate at optimum levels.

 

[Janni]

Scotty and Cindy are racing T1. That's an SRT.

See this thread:
http://vca2.viperclub.org/forums/showflat.php?Cat=&Board=scca&Number=505955&page=0&view=collapsed&sb=5&o=&fpart=1

Dodge Motorsports and NayKid Racing Announce 2005 Viper T1 Program


PUYALLUP, WASH., February 16, 2005 – Dodge Motorsports and NayKid Racing are proud to announce that the multi-division Sports Car Club of America (SCCA) champions will make a momentous move and campaign two Dodge Viper SRT-10s in the 2005 SCCA T1 class. NayKid Racing owner Scotty B. White (Puyallup, Wash.) and Managing Director Cindi Lux (Aloha, Ore.) will be the first drivers to pilot the V10-powered American Supercar since 2002. The announcement is less a launch and more of a reunion for both sides. White earned an SCCA Solo title in a Dodge Viper and Lux started her immensely successful career racing a Dodge against now Dodge Motorsports Director, John Fernandez in the late 1980s.

Following a dominating season in-which the team won every regular season race on the way to two divisional titles, team principals Lux and White began an exhaustive search to create an even stronger program in 2005. An agreement between Dodge Motorsports, Mopar Performance Parts, Dodge’s SRT Division and NayKid was reached making the first two-car punch for Dodge in the T1 class. Longtime team sponsor KUMHO Tire will return in ’05 with a Dodge Viper version of their very successful V710 tire.

The American Le Mans Series’ inaugural Women’s Global GT Series champion, Lux will pilot the No. 78 KUMHO Tire/ Mopar Performance Parts/ Dodge Motorsports NayKid Racing Dodge Viper SRT-10. Lux, who became only the second woman to win the prestigious SCCA June Sprints at Road America last season, will challenge for her third-straight NorPac Divisional T1 Championship as well as pursue the unprecedented SCCA Triple Crown (wins at both the June Sprints and Runoffs matched to a Divisional title) in ’05.

White, a six-time SCCA T1 division champion, including the 2004 Rocky Mountain Divisional T1 titleholder, will wheel the No. 3. KUMHO Tire/ Mopar Performance Parts/ Dodge Motorsports NayKid Racing Dodge Viper SRT-10. In 2004, he had a nearly undefeatable season winning 10 poles, seven wins and three track records in 11 races. Only Lux could challenge her teammate as the two swapped first and second-places not only race after race but lap after lap.

While primary support for the 2005 Viper program will come through KUMHO Tires, Dodge Motorsports, Mopar Performance Parts and the SRT Division of Dodge, further support will come from new partners Forgeline Wheels and Moton Shocks along with longtime partners RedLine Oil, CORSA Exhaust, Nike Racing and UPR Racing.

NayKid Racing was formed to be a championship-winning effort. 2004 titles include Lux’s Northern Pacific and White’s Rocky Mountain T1 Championships. Lux had also won the Northern Pacific title and Oregon SCCA National Driver of the Year in 2003 while White won the Southern Pacific title. Since its creation, NayKid has earned eight SCCA Division T1 championships, as well as five SCCA Pro Solo and eight Solo II titles. With a focus on winning, NayKid Racing balances the intense workload of racing with a lighthearted attitude that encourages fun at the track.

 

[Gforce]

Thanks Janni.

Very interesting. Its realy clear that the article thinks they are running SRT10s but I can tell you - I was there - in the pits - and both cars were comp coupes.

Maybe they ended up running the SRT10s in the T1 and the comp coupes in another group. I think they were running in SPO but I don't recall for certain.

the odd thing is that they were both Khomo sponsored so now I'm confused. I'll give Scotty a call this weekend and post back once I figure it out.

cheers -

j

 

[GR8_ASP]

Not sure if my experience is worth noting. But, since I cannot keep my keyboard silent, I will give a novice' opinion.

Yes I have encountered what you speak of. In general I have had it in corners where I have overbraked and am accelerating through the corner or in increasing radius corners. As I accelerate I eventually find a point where the inside rear tire starts to slip rotationally. If I do not relax quickly I soon find the rear coming around. It almost seems like the diff is acting like an open diff due to limited speed differential between the rear wheels. This is not a fast slip rate but quite gradual. You can actually hear the inside tire start to spin. This usually happens when accelerating at a limited rate. When under hard power the diff locks up and works well. It is during these part throttle, gradual acceleration conditions that I have noted it.

 

[Brad04Mamba]

From this months viper magazine

Did you see these cars there?

 

[Janni]

Based on the results that were posted on the Oregon website, they ran T1 in the Nationals and ITE in the Regionals. Both were listed as Viper SRT-10s. They did not run in SPO.

Dodge is supporting their efforts because they are campaigning SRT-10s. Dodge looks to World Challenege and the VRL for the comp coupes.

The NayKid racing website is all about their T1 efforts with the new Dodge SRT-10s. They even discuss how SCCA is now going to let them upgrade the stock suspension on their cars for the next event (Rose Cup).

So unless there were 4 cars there, it was the cars that Skip posted above - SRT-10s with affixed hardtops.

 

[FrankBarba]

Jay....Janni knows what she's talking about. Don't test her.

 

[Scotty B]

I eventually find a point where the inside rear tire starts to slip rotationally. If I do not relax quickly I soon find the rear coming around. It almost seems like the diff is acting like an open diff due to limited speed differential between the rear wheels.

Hey guys,
I should pop in and clear up a couple things here.

Jay sorry I didn't have enough time to explain really well what I was trying to say, we were kinda crankin on tearing down and packing up to go home at the time so I was a bit hasty with myadvice.

What I was trying to get across was exactly what is described above and thatis to just be sure and "not spin the inside tire too much" in the corners because what happens is when you do that the diff itself acts as a pump to engage the diff clutches and it will eventually lock the diff whichis exactly what it is supposed to do, BUT. If you are really smoking the inside tire you are running the pump at high speed and the pressure builds rapidly and locks the diff rather suddenly. Thiscan result in rapid and andvery sudden oversteer coming on which can be a handfull. It is only a problem if you are doing a dramatic one tire fryer

The diff actualy is designed to operate as sort of an open diff until there is a wheel speed difference which rus a hydraulic pump to become more of limited slip and it works quite well and also allows the cor to handle well with the much smaller front tires which makes the car a pleasure to drive on the highway, makes it faster at the drag strip yet still turns on the road course... Its kinda a cool concept and a lot of forethught went into this deal. Just avoid enhilating theinside tire on the track and yer golden!

OK, myth 2

We are running SRT10 Vipers with the spec Autoform hardtop from Jon B at Partsrack. The cars are near stock with of course a 6 point cage, Racetech seat, a Mopar Performance parts T1suspension kit which consistsof shocks, sway bars, springs, camber shims and drop links and shock brackets and of course that lovely special SCCA MANDATED 40% INTAKE RESTRICTOR and perfect weight of 3560lb (280lb heavier than the vettes) which ***** and brings me to my next thing I need to clear up..

These cars ROCK on the track and with the great torque and great brakes they will run very well in a novice' hands. The problemswe run into is when more experienced hand get ahold of cars like the Z06 and stuff

With novices it's usually mostly about power and brakes (where this car rocks) but when veterans start carrying more speed in the corners and transitions (which is where the srt needs help with oil pan and bars) and stuff the SRT starts to need a bit more to keep up in the transitions and carrying speed in the corners etc..

Please don't get me wrong gang, I am not intending to talk don to anyone or pump up the chebby or porch it's just kinda the way it is. This car is an incredible value and I can honestly say that even though the SCCA is right now keeping us from being able to win at every track like we did last year in the vettes... I LOVE THIS CAR MORE THAN ANY OTHER RACECAR I HAVE VEVER OWNED!!! And that includes my WCGT Corvette, and Rich W can verify what a cool car that was

I just totaly dig this hot rod, it beautiful to look at, it fits me like a glove and I love the way the Corsa side pipes resonate!

We are learning a lot and I am happy to share with any of you what we have learned. I would also invite any of you Mid West guys to come see us at Sprints or Watkins Glenn on 6/28 and 7/10 respectively

sbw

 

[MAVERICK]

I agree with all of Kai's comments ... you should follow them if your purpose is to track the car

 

[Gforce]

yep - and boy do I feel silly. Apparently I was looking at a wolf in wolves clothing. I confirmed that these were in fact SRTs and I was just stupid <oops>.

Sorry for the confusion. My bad.

j

 

[Gforce]

Thanks Scotty. I guess I shoudl have looked closer at the cars. I watched the whoel race and thought they were comp coupes

Curious - are you using the stock differential or an upgraded one?

BTW - I knew you were not talking down on them so sorry if I made it sound like that. My 99GTS and I really had a nice zen thing going on and I am looking forward to getting the SRT up to that level.

The cars I am most worried about are the Z06 (have a mouthy friend who takes delivery some time this summer) and my 99GTS which I sold to James. The 99 had the archer suspension, braided brake lines, roller rockers and some other goodies. It was one of the fatest ones on the open track days last year. Combined with Jame's driving skills, its going to be fun to test them out on the track (and I hate to get beat by my old car - even if its not a convertible).

Only thing I am really struggling with now is how to spend my next $3K. On the one hand, I could go with the Motons and get the car lowered. Seems like a good way to go.

On the other hand, I could go with the differential. At portland, in the 99, I powered out of turn 6 in a controlled 4 wheel drift that gave me an incredible advantage on the back stretch versus almost anything else out there.

I haven't had the SRT out yet but after our brief conversation last weekend, I did get a bit gun shy.

thoughts?

j

 

[Gforce]

Scotty -

in your post, you mentioned that it was only a problem if I was dramtically smoking the inside tire - which I seldom do because its usually not the fast way around.

One of the other posts indicated that it only happened under partial throttle - which is really what I was concerned about.

I almost always "over-brake" and drive the corners under power. Not a ton of power - just a bit more than maintenance throttle to keep the back end weighted.

See any problems with this?

thanks again for your time -

j

 

[Scotty B]

Curious - are you using the stock differential or an upgraded one?

We use either the CC or the Quaiffe

The cars I am most worried about are the Z06 (have a mouthy friend who takes delivery some time this summer) and my 99GTS which I sold to James. The 99 had the archer suspension, braided brake lines, roller rockers and some other goodies. It was one of the fatest ones on the open track days last year. Combined with Jame's driving skills, its going to be fun to test them out on the track (and I hate to get beat by my old car - even if its not a convertible).

Well I hate to say itbut the C6Z06 is gonna be a tough show sinece the power is close to our hot rods and theweight is about 300lb less... The Gen2 car James has now will be tough if driven well so I dunno what to tell you but I can relat to getting beat by a car you sold to somebody, BTDT and its lookin like it could happen again...

Only thing I am really struggling with now is how to spend my next $3K. On the one hand, I could go with the Motons and get the car lowered. Seems like a good way to go.

On the other hand, I could go with the differential. At portland, in the 99, I powered out of turn 6 in a controlled 4 wheel drift that gave me an incredible advantage on the back stretch versus almost anything else out there.

I haven't had the SRT out yet but after our brief conversation last weekend, I did get a bit gun shy.

thoughts?

j

Jay, I am a big fan of a proper suspension and this would also allow you to lower the car which is gonna make it look bitchin on the street too The diff is a nice choice but if mod funds are limited you gotta spend the dough on the CC Oil Pan first before anything else, then chassis, then diff and now you got some kinda hot rod!

sbw

 

[Scotty B]

Scotty -

in your post, you mentioned that it was only a problem if I was dramtically smoking the inside tire - which I seldom do because its usually not the fast way around.

One of the other posts indicated that it only happened under partial throttle - which is really what I was concerned about.

I almost always "over-brake" and drive the corners under power. Not a ton of power - just a bit more than maintenance throttle to keep the back end weighted.

See any problems with this?

thanks again for your time -

j

I really think that huge inside wheel spin is the only thing you need to worry about and it sounds as though that is not your style anyway. So go buy the iol pan and have some fun!

sbw

 

[Viper X]

Good post Kai,

I ordered a comp coupe oil pan last week.

Dan