My Motorsports Passion
A new challenge, suspension redesign by a Rookie!
After deciding to use this chassis for R&D to hopefully, make it a really great road race chassis and to share what I learn with others so we can go racing and have a lot of fun. After all, that's what it's all about!
One of the first modifications I did was to improve the stock lower front suspension control arm and the front sway bar that was on my car when I purchased it a few years ago. First, the lower control arm was bending and as a consequence, the geometry and ride height would change during an event. The solution, add a gusset plate welded vertically to strengthen the existing tubing. Additionally, the front sway bar which was mounted to the lower front shock absorber would cause the entire front suspension to bind and restrict movement. With some 1/2" aluminum, I lengthened the sway bar control arm so that it would reach the center line of the lower control arm. I fabricated two tabs to mount the hiem joint or rod end to the lower control arm and used the same adjustable rod to couple to the new sway bar arm.
On and off during this first part of 2012, I was without a car to drive so I used the downtime to read up quite on suspension setups in books and blogs, talking to guys with knowledge in this arena and combing what I know about the car and building a model of the front and rear suspension in Performance Trends "Suspension Analyzer Software" with one thing in mind, and that is improve the good piece (chassis) we have to make it an even better handling car by adding fully adjustable suspension geometry with the exception of the front lower control arm pickup point. This will be fixed, for now! Even though we have been able to dive the car and recording some great lap times in its stock configuration, I could never eliminate the over-steer and under-steer we would experience entering a turn and then exiting a turn. It would push entering the turn then the back end would break loose on the exit. Remember, the stock chassis is a 20 year old circle track chassis designed to make left turns with a left offset built in resulting in different left and right side front suspension geometry and the rear suspension induced rear steer when the body rolled in the turns.
I started with the front suspension first. I stripped the chassis down to just tubing, even removing the foot box leaving the original right lower front and rear suspension mounting location and the left, lower rear mount. Then I went to work measuring everything and what I found was both a surprise and a relief. Surprised by the determining that not too much would have to be changed by using adjustable pick-up point hardware and making the front suspension symmetrical. Once I had all of the suspension (front and rear) pick-up point measurements programmed into my Suspension Analyzer Software, I was able to move the upper control arm pick up points a lot, simulate suspension travel, see the effects of the modifications by watching the animation of camber gain, toe gain and caster gain as well as the roll center height. This was so exciting to be able to "change stuff" so I could get a good starting point of what tubing to cut out and where to add new tubing. During that software process and then applying it on the chassis, an unexpected improvement presented itself where I could relocate the front shock & spring so it was in an arc with the control arm movement rather than the natural bind inherent with the original design. So with the software setup completed where the car is NEUTRAL, without over-steer or under-steer and minimized toe and caster gain, I went to work.
Relieved by determining that the RIGHT side lower control arm pick up points would be the basis and changes made from there. That meant drilling out the existing left front lower control arm side pick up point and moving it out at the same height so it would match the right side. The lower rear pick up points will remain as is for the time being. This was the first thing that need to change to make the lower control arms 5" out from the center line. Below is the new support tube tacked in place.
Below, the left side rear upper control arm bar had to be cut out and a new bar with a 7 degree bend installed to permit just enough clearance for the intake manifold and room for the clamp on bracket to slide up and down for adjustability. The right side bar did not have to be cut out, just grind off the protruding threaded bar to allow the clamp on bracket to slide up and down and turn.
After a full day of determining how the suspension pick-up point locations should be, I went to work cutting, notching and tack welding in the new tubing and as you can see below, most of the fabrication in complete with the exception of welding all of the joints. Provisions were also made to allow the new 2.4 Liter LE5 Ecotec engine and transmission that I had purchased in October 2011 to be installed. Since the engine mounts did not have to be changed, this means I will be able to use the original Mazda B2200 fuel injected engine and transmission if I chose to do so. It really is a tight fit and the foot box would have to be modified.
Another advantage of using the LE5 engine is the exhaust is on the right hand side whereas the B2200 was on the left, and reduce the direct hot exhaust header temperature so close to the cockpit.
The next step was to fabricate new front upper control arm tubing and install them in the appropriate location, moving the forward which is how I was able to get the shock in its new location.
Recommended by Randy Andersen in Houston, you will notice that I am using clamp on suspension brackets to secure the upper control arms to permit infinite adjustability. With off the shelf components to make up the upper and lower control arms, I will have the ability to really fine tune the suspension once testing begins. In the pictures below, I ordered just one ball joint holder in order to mock up the new geometry which as you can see place the front shock directly in line with the lower control arm at a 19 degrees angle. This de-rated the shock by just 10%, not much at all but the benefit will far outweigh that small loss. I would have to order a different offset ball joint holder because the front upper control arm was interfering with the spring as well as determining the length of the threaded tubes for caster and camber adjustment.
Now that I used the right side to mock up the new suspension geometry, I knew what I had to order. I considered reusing the modified original lower control arms but unfortunately, the sway bar brackets would have to be cut off and new shock mounts added so it was to much work and added components to my list to build new lower control arms that were much stronger and fully adjustable.
While I waited for my new suspension parts to arrive, I moved to the back of the chassis to figure out what I would have to do to install a new, larger fuel cell since my original fuel cell bladder was leaking and the cost to replace the bladder was more than a new fuel cell as it was originally a custom fuel cell.
The solution was to add 8 inches in length inside the frame essentially taking up room between the chassis's old rear weight box that I never used and the rear bumper bracket. It had to be moved back to allow enough room to perform the quick-change differential gear change. What I did to ensure the integrity of the chassis is measure, cut and weld in the additional 8 inches in length and then cut out the original back rectangular tubing. Once I did this, I was able to fabricate the fuel cell frame and hold-down frame with 4 securing points. An added benefit with this fuel cell in this location is it is located in the center of the chassis instead of on the left side of the car and it will be much easier to fill
That was the only work I elected to do in the back of the chassis for the moment. I will be researching modifying the rear suspension 3-link pick up points, most likely this coming winter as I need to get the car ready to race in October at Eagles Canyon Raceway. Back to the front of the car.
Now it was time to secure the engine and build the transmission mount. The original transmission mount remained unaltered and so I fabricated a new mount and welded it in place. Next was the foot box, mounting the clutch & brake peddle assembly and the new drive-by-wire gas pedal.
Another modification I made after studying pictures of a few Trans Am cars was the placement of the radiator. A lower radiator effects the center of gravity (CG) on a race car and this is a very important tuning point. What could I do to mount my radiator in a similar fashion, lower the weight and move it forward. I learned that shifting sprung weight around is better than adding weight to compensate for that when scaling the car at the end. So, what I did war modify the existing front bumper bracket, weld aluminum angle iron to the radiator, cut off the radiator filler and weld a plate to cover the hole and finally box in the radiator with new sheet metal to direct airflow. Another benefit later on will be front down force because of the way the air will travel through the front of the car.
Now it was time to fabricate a new battery mounting assembly, put the old sheet metal and body back on and see what had to be trimmed to accommodate the new power-train, electronics and fire system.
You will notice that all of the original sheet metal was reused after a little trimming here and there! The shifter is moved forward as well, permitting a more comfortable shifting pattern when seated in the car compared to before when the shifter was really too far back. Remember, this car was originally designed for circle track racing, you typically don't shift gears once you are up to speed and racing. If you are interested in this shifter adaptor, contact me.
Once all these components were installed, two new opportunities presented themselves and that was I had sufficient room in front of the engine with the radiator moved forward to relocate the front sway bar and fabricate brake ducts directly to the spinal which directs air flow too the center of the new, vented brake rotors. The Speedway Engineering sway bar is now mounted on top of the frame which allowed a shorter sway bar arm permitting the sway bar to me much more effective.
And finally after many hours of dedication and determination to finally have an almost "true" road race car built with what I had, the completed car was ready to go testing at Eagles Canyon Raceway on Saturday, September 15, 2012. And what a surprise it was. I was absolutely amazed at how easy the car was to steer, almost like I had installed power steering.
Unfortunately, the day I had available to do my first testing was cool, no sunshine, the track was damp in the beginning and I had a few "New Car" problems I encountered but not all was lost, I managed to improve my personal best lap time by just over 3 tenths of a second for just one lap before the camber, toe and brake problems I had exposed themselves. I don't know why but I used the wrong size front brake master cylinder which resulted in way to much rear brake. So this chapter of constructing my new car closes and I will begin a new page where I will detail the future testing results which will be at the upcoming NASA event at Eagles Canyon Raceway on October 6-7, 2012.
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