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Putting a Race car back together

 
Old 01-29-2019, 07:01 PM
  #46  
Yogii
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My heal and toe is left ball of my right foot and right ball of my right foot.

-Yogii
AKA 968 Virgin
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Old 01-30-2019, 12:25 AM
  #47  
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Hey Cloud9! There are no secrets! I'll do the best I can:
Bilstein Escort Cup shocks, front and rear. Spring rate 900 front / 700 rear
M030 Front and rear sways with Racers Edge drop pinks and components
Had Delrin in the rear spring plate which I just replaced with Elephant Racing Polybronze bushings
Racers Edge Camber plates (front)
Racing dynamics upper chassis brace
Cage is not attached to the suspension. It is a full cage welded in. Pretty standard, but has a brace above the dash, which makes me feel safe!
Square set up 275/40R17 on 17x9.5 Porsche Cup 1 wheels.
Racers Edge A arm spherical bearings, front
RS BARN lower chassis brace
Elephant Racing Rear monoball trailing arm bearing
The car is lower than stock and height adjustable via the coilovers. I'm not sure what the actual ride height is.
What do you mean by: "Anything to compensate for the subterranean front roll center ..."


Thanks for sharing your car's information, and sorry for the slow response - been very busy with work. Our cars have a lot of the same (or similar) components. I seem to remember from your thread on your amazing torque tube repair that yours is a bit closer to a pure track car than mine; I still drive mine on the street, though mostly to and from the track. When I was doing the mods, I had considered possibly racing it someday, but I have bashed all thoughts of ever doing that out of my head - never in a million years - way too much constant maintenance, plus I don't have a trailer, a truck, or room for either, so it's strictly noncompetitive sessions for me at the local track (Driveway Austin), while I save up to compete in an arrive-and-drive series.

Considering it's just my "training tool", I went WAY overboard on the mods - like an addict, I just couldn't stop. Here are the major mods:

- Basically one of everything Racers Edge sells - solid/spherical bushings everywhere, camber plates, etc., except I went with the delrin spring plate bushings rather than the polybronze
- 2.25" i.d. Eibach coilovers (torsion bars deleted), 700/800 lb front/rear
- Racers Edge heavy duty geometry correcting control arms
- Racers edge billet hubs
- Double-adjustable Moton Clubsports with remote reservoirs (ridiculous overkill)
- Lowered about 1.5"
- Track oriented alignment - about -3.5 degree camber up front, about -2.3 degrees in back, but very little toe
- Welded half cage
- Design 1 Racing strut brace
- Design 1 Racing caster block brace
- Teflon steering rack bushing
- Weltmeister adjustable front sway bar
- M030 3-way adjustable rear sway bar
- Sparco Evo racing seat
- About 220 lbs taken out of the car, including fixed headlights, removal of front and rear bumper bars, 6 lb lithium ion battery, and too much other stuff to list. Still disappointingly porky at 2870 lbs.
- 944 Turbo S calipers with Zimmerman cross-drilled rotors
- 17 x 10.5” forged Signature SV103 wheels (49 mm offset), with 275/35-17 Maxxis RC1 tires all around. No spacers or fender modification were needed. The wheels weigh about 18 lbs.

The main goal here is to have fun, so I won't critique anything you or anybody else has done to their car, but I do have a couple of comments/questions. How did you come to select your tire size? 275/40-17's are about 0.7” taller than stock, which effectively lowers your numerical final drive ratio, costing you some revs coming out of the corners. Also, this is a big, heavy tire, and your wheels tip the scales at 27.5 lbs, and 275 is pretty wide for a 9.5” wheel on a track car. This is a controversial topic with many opinions, but Grassroots Motorsports has done a fair bit of investigation of the optimal wheel/tire width relationship, and concluded that it’s the width of the wheel that really matters; how wide of a tire you squeeze over it has little effect. Check out their December 2013 issue, where they cover this topic pretty thoroughly. So, next time around, you might want to consider a 245/40 or 255/40-17 – they’re a little cheaper, too. Just a suggestion.

951and944S has already commented on your springs. Those are an interesting choice, but I can understand the reasoning behind going so much heavier in the front than in the back (in terms of wheel rate). The car came from the factory with a staggered set-up, so when switching to a square set-up, you’re effectively adding more grip to the front relative to the rear, which pushes the bias toward oversteer. I originally had 1000 lb rear springs to go with my 700 fronts, and the car was a twitchy, tail-happy, uncontrollable mess. According to the formula for calculating spring rates based on the “optimal” spring frequency of about 150 cycles/min in the front, I should be running about 500 lb springs in the front, but I’m reluctant to move in that direction because I don’t want my car to get too tail-happy like it was before.

Regarding my comment on a subterranean roll center, what I meant is that when you lower a car, particularly one with a Macpherson strut front suspension, you of course lower the center of gravity, which is good, because it reduces the overall weight transfer during cornering, which increases grip, but it actually lowers the roll center, the point about which the car theoretically pivots during cornering, more than it lowers the CG. This is an outcome of the fact the when the car is lowered, the control arms’ inner attachment points are lower than the outer attachment points (the ball joints) – the arms are no longer parallel to the ground, in other words. The distance between the CG and the RC is called the roll couple, which constitutes a level arm that effectively induces sway during cornering. The longer the roll couple, the greater the torque about the lever arm, the more the car want to sway. This is fixable, but it’s either expensive, through the use of longer ball joint pins which bring the control arms back to level, or some people actually raise the inner control arm mounting points. To use the longer ball joint pins, you need the Racers Edge arms, which cost $1600. Also, it gets complicated, because if you raise the front roll center without simultaneously raising the real RC, you create a tilted roll axis (the line connecting the front and rear roll center), which does bad things, I’m told. There’s a guy named Bruce Karger in Houston who makes a modified torsion bar carrier replacement with raised trailing arm attachment points to balance out the front/rear roll centers. I have one of these (I know, what a shock), but haven’t installed it yet. There is a ton written on this general topic – just google roll center/center of gravity, and enough stuff will pop up to make your head spin.

All this stuff is interesting and good fun, but to me, the real goal of this hobby is the driving; I just want my car to be capable enough to not embarrass me, although I’ve clearly gone way over the deep end with all my mods. Do you have any type of data acquisition system? I have a pretty high end Aim system, including an Evo4S data logger, a GS Dash unit, a Smartycam HD video camera, and analog sensors for brake pressure, throttle position, and steering angle (I built my steering angle sensor myself). My next step is to corner the local track pro to do a few baseline laps in my car to see where he’s faster (no doubt everywhere!), and more importantly, why? Aim is hosting a data acquisition analysis hands-on seminar in my town in a few weeks, and I plan to go and immerse myself in the nuances of trying to understand where I have opportunities to improve my driving to lower my lap times. Then, once I’m satisfied I’d wrung about everything I can out of my car in its current configuration, I plan to install the longer ball joint pins, the bump steer kit that needs to go along with it, and Bruce’s bar, and rebalance everything with the appropriate springs, sway bar stiffness, and lastly, shock compression/rebound settings, see how much faster that makes the car, and recalibrate my driving to take advantage of it.

Anyway, sorry about the very long post, but I’d be interested to see if other people chime in with what they’ve done to their cars, what has worked, what they wished they hadn’t done, etc., so we can all learn from each others’ experiences.

Last edited by Cloud9...68; 01-30-2019 at 12:35 PM.
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Old 01-30-2019, 01:03 PM
  #48  
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^^^ Nice setup!

I have a similar game plan for my car and continuing to track / DE it but i'm still a ways behind where you're at.

I use to play the GP F1 simulator games on the PC with force feedback wheel and pedals. Would spend hours developing car setups, data logging laps and overlaying graphs...make a change, run 2 hot laps and in, graph, make adjustments, repeat. The graphics of the older game were not great by today's standards but the physics, data analysis, graphing and process of developing the car is/was all relevant and is what I would like to be doing with my 951...or as close as i can recreate. Sounds like you're there.
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Old 01-30-2019, 02:12 PM
  #49  
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Originally Posted by mj951 View Post
^^^ Nice setup!

I have a similar game plan for my car and continuing to track / DE it but i'm still a ways behind where you're at.

I use to play the GP F1 simulator games on the PC with force feedback wheel and pedals. Would spend hours developing car setups, data logging laps and overlaying graphs...make a change, run 2 hot laps and in, graph, make adjustments, repeat. The graphics of the older game were not great by today's standards but the physics, data analysis, graphing and process of developing the car is/was all relevant and is what I would like to be doing with my 951...or as close as i can recreate. Sounds like you're there.
That's quite a conicidence, since I'm toying with the idea of doing what you're doing, but in reverse. In other words, I'm interested in building a simulator to use to practice my technique between sessions. From the research I've done, it appears possible to build a home simulator that does a good enough job of replicating the real-life experience to actually help you become a better, faster driver. "Free" extra, precious seat time, in other words. The only problem is that such a simulator, without motion, runs around $15K, including a good direct drive wheel, VR set-up, the rig, a seat that matches the one in my car, quality pedals and shifter, and a computer capable of running everything with high quality resolution, and of course the installation and set-up. To add motion, it's more like $30K. Would you mind if I send you an IM or two as I get closer to pulling the trigger on this, since you're clearly very knowledgeable and experienced with this stuff? Thanks.
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Old 01-30-2019, 10:51 PM
  #50  
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You're free to PM me but I was playing a game on the PC and that has nothing to do with today's simulators.

I did build an adjustable race seat base and pedal deck pretty easily though. I have solid core doors on steel post legs for tables in my office/studio. The seat and pedals slide up and under the desk, I use a 43" TV for a monitor, wheel attaches to door/desk edge. No motion, I wear full over ear headphones and with the lights out I can get pretty immersed in it.

There's a couple good threads on simulators going in the race category. They've also had me thinking about simulators and maybe trying a sports car game. It's really the data, graphing and overlay capabilities that I liked in the GP games so I would want to find those capabilities in a sports car game as well. I haven't researched any of the latest games or simulators other than reading the mentioned threads.
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Old 02-10-2019, 12:05 AM
  #51  
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Default CV Joints

After cleaning CV joints last week and pulling some spares off the shelf, I selected 4 CV joints that had little to no signs of wear. Then greased them with Redline CV-2 and installed new OKG boots. All clean and ready to go into the car.

One of the spares that I had. It doesn't look so great right now, but a couple of these showed just street-car wear and cleaned up beautifully.


I used old gasoline as a cleaner. This picture shows the outside surface of the three pieces. The outer housing has 3 lines toward the outer face. The middle cage has a flatter edge on the outer face (the inner face has a more pronounced bevel). The inner cog has a flat outer face with a single grove line.


Four best CV Joints which were then stuffed with Redline CV-2. We managed to keep the work area very clean in the process.


Ready to go in the car - maybe tomorrow!
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Old 02-10-2019, 10:13 PM
  #52  
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Nice, you're becoming an old pro.

IMO, you made a good choice, since now if you have a problem at the track, you already know what you are dealing with.

Had you just thrown 2 new ones on, you never would have gained from this experience.

T
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