Need help keeping up with C6 Z06 & Porsche GT3 on Road Course

-
Do yourself a big favor and go get some on-track driving instruction. Get some seat time and learn car control. You'll have a blast, and when it comes time to put your car on the track you'll be that much more ready and experienced. It's very addictive; you have been warned!

Check into your local BMW club chapter, they run track events all the time. You get an instructor in your car teaching you the proper line and technique as well as keeping you out of trouble, plus their rates are very reasonable.
 
I am going to put my vote in for the Big sway bar and light(er) T- Bars.
One thing you got to remember is that lowering the front suspension with the stock LCA mount location will eventually evolve to a point of diminishing returns. That is, as the car is lowered more than 2 1/2 inches (with stock spindles being used) the lower control arm will start to move (during suspension travel) in a way that will negate the camber gain of the upper control arm (to some degree). The best option would be to use a lowered spindle to start off with. (some new ones have recently come on the market). This way the LCA can remaun in a somewhat factory orientation (or slightly of a more lowered position from factory) and you will be able to utilize the built in camber gain to its full designed-in functionality. One of the hard part of lowereing a T-bar car is the COG issue because the T-bar itself usually has to be mounted under the floorpan of the vehicle. This limits the location point of the Lower control arm mounting point to a less than ideal location as far as a performance setup is concerened. Now if you could mount the control arms ABOVE the floor pan then some real performance gains could be achieved as far as COG is concerened, Of course, this is unnacceptable from an OE standpoin due to the interior requirements of the buying public.
One other thing crossed my mind and I will be trying this in a future build. Try moving the ENTIRE K frame forward on the (sub) frame rails. You wouldnt have to go too far to gain a TON of caster ( which is one of the A body"s weak points). No need for offset bushings or anything like that. I know but you say" that will move the engine forward."
you can mod the mounts or just use some spacers on the motor mounts. Yes yo may have to move the steering shaft a bit but think of the benefits. try getting 3 or 4 degrees of caster with the stock setup, sometime you cannot even get the stock alignment settings without the use of problem solvers. You could either weld the K right to the subframe or jst modify the loation "holes" on the K frame itself.
That's all I got for now..just my .02.... like this build idea though and I know it can be done........I don't know if you remember the "GREEN BRICK" of Mopar Action (68 Valiant). It whipped up on alot of Porsches AND Corvettes with basically factory parts
 
autoxcuda said:
Extremely true!

And the older cars are going to be tougher to drive as quick as the new stuff even is they are equal capable cars. Experienced driver in new sportscar might be as fast in older modified car. But inexperienced driver will probably be much faster in newer sportscar.
Click to expand...

The newer Vettes are impressive and hard to beat, but most of the time it's technology driving the car. I'll never forget a student I had in a black C5 Z06. He would hammer up to a turn, pitch the car in and let the stability control do the rest. I kept asking him to turn off the stability control since the car was doing all the work, quite impressively I might add, and the student wasn't learning anything. He would not do it. After pressing him all weekend he finally 'fessed up. This was a new car he was driving. He tried turning off the stability control in his previous car (also a Vette,) couldn't control it, crashed and totalled it #-o.
 
This is interesting reading. Could somebody post the website/ particulars on the yellow Dart that was posted?
 
omahamoparguy said:
I am going to put my vote in for the Big sway bar and light(er) T- Bars.
Click to expand...
I agree with the lighter t-bars, nicer to drive on the street for a dual-purpose car.

omahamoparguy said:
Try moving the ENTIRE K frame forward on the (sub) frame rails. You wouldnt have to go too far to gain a TON of caster ( which is one of the A body"s weak points).
Click to expand...
Well, if you're going to go through all that work, why not move the UCA mounting points rearward? That way you won't need custom-made longer t-bars, worsen your weight distribution and wheelbase, and need to relocate the upper shock mount as the shocks will not line up with the LCAs.

omahamoparguy said:
I don't know if you remember the "GREEN BRICK" of Mopar Action (68 Valiant). It whipped up on alot of Porsches AND Corvettes with basically factory parts
Click to expand...
Yes it was mostly stock but it did have some trick pieces in it. An, 8 3/4 with aluminum center section and a Barton-built small block to name a couple, and others things I won't mention. Most importantly; the driver was/is a natural that could have gone pro if circumstances allowed.
 
omahamoparguy said:
try getting 3 or 4 degrees of caster with the stock setup, sometime you cannot even get the stock alignment settings without the use of problem solvers.
Click to expand...

Never been an issue with both of my A-bodies or other cars that I personally know and seen with offset bushings. Cars that can't get stock alignment with offset bushings have some car issue or an alignment tech issue. 40 years of mismatched parts, bad replacement parts, collision damage, and rust issues....

If you gotta move your K-member forward for 3-4 degrees of caster, there's something else not right or there's other options (adj: strut rod or UCA)
 
Mr.Ed said:
... Most importantly; the driver was/is a natural that could have gone pro if circumstances allowed.
Click to expand...

I heard that Kevin Wesley is a great driver. I know someone that is trying to woo him into co-driving a One Lap entry.
 
Brings up a good point, even the best driver couldn't keep the Brick out of the wall because he ran out of suspension travel....
 
I think that the green brick IS a good example of how to use some of the factory parts and get some good performance. The fact that someone does or does not know how to drive is moot. I was not defering to the Barton built engine, just the lowb buck suspension. You ARE going to have to know how drive if you are going to be going up against Porsches and vettes with an A-body mopar. That is one thing for sure. especially with the manual steering box in it. I would be more concerened with tire/wheel selection as that might be the deciding factor.
IT"S RACIN" FOLKS, I imagine a few vettes bough the farm in that one lap also. that is why racin is not too fun in the end when you run into a wall. If you got a deep wallet, it dont hurt AS much but if you got eveything you have into the car, then it hurts cause then you got to start over from scratch sometimes. If you got buds that can afford vettes and porsches you better really have your driving and car set-up down to a science cause that might be the only area where you could "out gun" them. As REdGreen says"were all pullin' for ya'"
 
omahamoparguy said:
I think that the green brick IS a good example of how to use some of the factory parts and get some good performance. The fact that someone does or does not know how to drive is moot. I was not defering to the Barton built engine, just the lowb buck suspension. You ARE going to have to know how drive if you are going to be going up against Porsches and vettes with an A-body mopar. That is one thing for sure. especially with the manual steering box in it. I would be more concerened with tire/wheel selection as that might be the deciding factor.
IT"S RACIN" FOLKS, I imagine a few vettes bough the farm in that one lap also. that is why racin is not too fun in the end when you run into a wall. If you got a deep wallet, it dont hurt AS much but if you got eveything you have into the car, then it hurts cause then you got to start over from scratch sometimes. If you got buds that can afford vettes and porsches you better really have your driving and car set-up down to a science cause that might be the only area where you could "out gun" them. As REdGreen says"were all pullin' for ya'"
Click to expand...

There's a movie (kind of a documentary) called "Love the Beast". This comment reminded me of it on every point. It's got the feel of one of those Warren Miller ski movies, but covers a guys attatchment to his car that he turns into a full on pro rallye car. Won't make you drive any better although you should be able to completely identify with the guy.
 
Just a technical question: do the road racing class rules permit replacement fiberglass body panels or do you have to run with factory steel panels?
 
I won't be racing in a class, and I'm not sure about the classes available and what rules they have.

I'll be running in the Drivers Edge program, which is a driving school. I'll do what it takes to become a proficient driver - obviously only then will I have a chance at keeping up. That being said, the times my friends are running vary. The Porsche GT3 is running 1:58-2:02 at Texas World Speedway, the C6 Z06 is running 2:08-2:10's, and a third buddy in a porsche is running 2:30's. Trackpedia lists 1:54's for porsche 933, BMW M3, etc. And spec miata's run about a 2:00 flat. So, I've just got to beat a spec miata ;) no easy task I'm afraid.

Drop spindles or no drop spindles? Autoxcuda, how much suspension travel do you have before bump stops? And how far does your K member sit off the ground right now? How much suspension travel is needed in both directions? I understand the magnumforce drop spindles do not interfere with 18's regardless of backspacing? I just spoke with magnumforce, and Clint said they advise 6-6.5" backspacing for a 8" rim (guessing still 18"), so he wasn't sure about 7.2" for a 18x9.5. But, he did offer me 30 days to try them, and if they didn't work, send them back, and I'd only be out shipping both ways. Good customer service right there.

I've got a single wheel on order to do some test fitting with the current set-up. We'll see how she looks.
 
Uhcoog1 said:
Drop spindles or no drop spindles? Autoxcuda, how much suspension travel do you have before bump stops? And how far does your K member sit off the ground right now? How much suspension travel is needed in both directions? I understand the magnumforce drop spindles do not interfere with 18's regardless of backspacing? I just spoke with magnumforce, and Clint said they advise 6-6.5" backspacing for a 8" rim (guessing still 18"), so he wasn't sure about 7.2" for a 18x9.5. But, he did offer me 30 days to try them, and if they didn't work, send them back, and I'd only be out shipping both ways. Good customer service right there.

I've got a single wheel on order to do some test fitting with the current set-up. We'll see how she looks.
Click to expand...

Drop spindles get in the way of 5.0 to 5.5 backspace front rims that you need to run 275/40/17 on an A-body. I don't run dropped spindles. Neither does Tim Werner. You should be running a 275 wide front tire, maybe more. In an 18" rim you would just need more flaring, rolling, and cutting.

I have about 5.25" between the bottom of the K-member and the ground. The header sit about 1/2" down from that. Oil pan is flush or a little above the bottom of the K-member.

I got about 2" inches clearance at the frame which is about halfway down the arm. Thats with the upward pointing flange cut off. So that would be about 4" at the ball joint for travel.

I don't run any LCA bumpstops. I've went off course and bent a rim, just slightly dimpled up area around upper shock, QA1 shock bottomed out first it seems. Car had fine alignment after that.
 
I've been warned of bumpsteer issues with the lowered suspension with no bump stops- does it create any unwanted geometry when you go this far?
 
Uhcoog1 said:
I've been warned of bumpsteer issues with the lowered suspension with no bump stops- does it create any unwanted geometry when you go this far?
Click to expand...

Honestly I haven't bump steered it.

But those who "warn" this should be able to provide you with thier bumpsteer measurements. Otherwise, it's just talk/guessing/heresay.
 
I just read up on a post on another forum with some computer program images regarding bump steer affects, etc. Looks like lowered factory spindles are okay in that category, and the 2" drop spindles are slightly worse. Not to mention, they determined the roll center height was higher with the drop spindles.

I'll aim for the measurements given (5.25" k member) by you, and stick to what works.

I've been researching everything for the last couple days, looks like my shopping list has grown! No surprise there.

I'm looking for an old 275 35 18 scrub to mount on this wheel for checking fitment- know anyone who's got one that is heat cycled out? The tires I plan to run are 275 35 18's on all four corners, used continental racing series tires. They seem to be in abundance and cost $50-100/tire after a few heat cycles. I just need to make sure I can make them fit.
 
Man, you guys have got it going here. It is intriguing to me how you make 45 year old cars handle with the newest. There is much science involved in calculating how much force is involved in cornering, which, I am sure, is the major variable in road racing.

Using the physics calculation for centripital force:

Force centripital = mass x (velocity squared) / radius; it seems that, all else being equal, i.e. power and meat on the ground and CG, the differentiatior is weight (mass). Is this assumption correct?

I know there are variables in rolling weight, but does the assumption of the mass variability have merit in road racing? Various steering geometry constructs are better than others, but is reducing sprung and unsprung weight the major or minor concern in road racing?

If this is the case, would concentrating on weight (mass) reduction be a large contributor to handling?
 
Mr.Ed said:
As far as Vipers being tubs compared to the 'Vette, remember the Viper OWNS the track record at the famed Nurburgring race track for production vehicles, beating the 'Vette as well as many other cars.
Click to expand...

Not anymore. The 2012 ZR1 beat the Viper record and the 2012 Z06 matched it. The videos are posted on youtube.
 
Uhcoog1 said:
I just read up on a post on another forum with some computer program images regarding bump steer affects, etc. Looks like lowered factory spindles are okay in that category, and the 2" drop spindles are slightly worse. Not to mention, they determined the roll center height was higher with the drop spindles.

I'll aim for the measurements given (5.25" k member) by you, and stick to what works.

I've been researching everything for the last couple days, looks like my shopping list has grown! No surprise there.

I'm looking for an old 275 35 18 scrub to mount on this wheel for checking fitment- know anyone who's got one that is heat cycled out? The tires I plan to run are 275 35 18's on all four corners, used continental racing series tires. They seem to be in abundance and cost $50-100/tire after a few heat cycles. I just need to make sure I can make them fit.
Click to expand...
I have 18x9s with that tire and no rub anywhere. If anything I bet you may need a 3/8" spacer. Mine is tight full lock left at the bellcrank bracket on the frame rail which could be trimmed if needed but in a real world scenario im almost never full lock left and if so the tire sidewall would pull away from it anyway.
 

Attachments

  • 20110517202118-1.jpg
    104 KB · Views: 186
Mr.Ed said:
The newer Vettes are impressive and hard to beat, but most of the time it's technology driving the car. I'll never forget a student I had in a black C5 Z06. He would hammer up to a turn, pitch the car in and let the stability control do the rest. I kept asking him to turn off the stability control since the car was doing all the work, quite impressively I might add, and the student wasn't learning anything. He would not do it. After pressing him all weekend he finally 'fessed up. This was a new car he was driving. He tried turning off the stability control in his previous car (also a Vette,) couldn't control it, crashed and totalled it #-o.
Click to expand...
I agree Driving a road course and following the correct line is a lot harder than it looks!! Plus it takes a lot of Nerve-Plus physically its exhausting=Blast (plus you can open your car up and see what she will do)
That is a smokin BB swinger!!
 
lilcuda said:
Not anymore. The 2012 ZR1 beat the Viper record and the 2012 Z06 matched it. The videos are posted on youtube.
Click to expand...
I retrack the 'Tub" statement and i was wrong. They are only a little heavier than the Vette's . 350lbs
They have plenty of capabillity I just haven't see a good driver in one yet?(Driver is everything) turns out
I am a Mopar Man so I will get back on the Viper band wagon. Lots of vettes and not many Vipers but i will look for one with a serious driver behind the wheel-exciting
 
You must log in or register to reply here.
-

Back
Top