An alternator bracket, a little window, and some hoses.

Posted on March 31, 2013 by admin

Hi guys!

I’ve made an alternator bracket:

See the lowest hole on the block that’s almost in line with the lower hole on the alternator? A turnbuckle will go between those so that the assembly can serve as a belt tensioner. As it so happens, the spacing is perfect for that.

The alternator is supported both in the front and in the back on all axes. Once the long bolt is tightened down, the thing doesn’t move…at all.

A new alternator bracket was necessary for a couple of reasons. First of all, I replaced the GTO crank pulley with a shorter Corvette/CTS-V/G8 crank pulley for more swaybar clearance. That meant that the alternator needed to be moved closer to the block so that the belt would line up properly. Some people mill down the stock alternator bracket to bring the alternator in further. I chose not to do that since I wanted the alternator so pivot as to serve as a belt tensioner. I removed the stock tensioner and the associated mounting tabs to make clearance for a coolant expansion tank that I bolted to the passenger side head. By making an adjustable alternator bracket, I killed two birds with one stone. All I have to do now for the accessory drive belt is fabricate a mount for an idler pulley so that the water pump is driven. Fortunately, that should be a simple task.

This doesn’t look a whole lot like progress however the drivetrain no longer needed to be in for mockup purposes. Now I can finalize a few things in the bay, and before long, I’ll be able to begin prepping it for paint. The next time the drivetrain goes in, it should be going in to stay.

Now for the weird bit. I’ve put a window in the upper frame rail. You know, so the frame rail gnomes can get some light and fresh air.

But no, the window is actually there for the fuel line and accusump oil line to be fed through.

The lines go through the frame rails, beneath the floor, such that they’re protected from heat and impact, and I’m protected from them.

Most people put the lines in the transmission tunnel or under the car next to the frame rail. I don’t like the tunnel route because it places the lines above a hot exhaust system. In addition to prolonged exposure to heat, a driveshaft failure could potentially split a line and almost certainly cause a fire since gravity, which tends to be pretty reliable, will cause the fuel to end up on the hot exhaust pipes beneath. That would be quite lousy. I don’t think along the frame rail is a good place either since running a nylon braided line inches off the ground seems a poor choice due to the potential for bottoming out, road debris, and slow abrasion from particulates.

It’s beginning to come alive!

Posted on March 20, 2013 by admin

Yeah, that’s right, progress. I had some opportunities to work on this car over spring break….so I did. The outcome was a fair amount of electrical work and the first hint of life that the car has shown in many months.

For those not familiar with the early stages of this project, I removed nearly all of the factory wiring during disassembly. The process was not delicate–I marked what I intended to reuse and tore out the rest with cable cutters. I was left with a few wires in the car and a full trash bag of wires sitting on the ground, adjacent. Wanton destruction? No, not at all. The great wire massacre of 2012 paved the way for me to make a much lighter and simpler wiring harness. Who doesn’t love lightness and simplicity? This all-business harness has custom routing, was laid out with an emphasis on serviceability(fuses and connections are easily accessible), is clear of things that may wish it harm(tires and excessive heat), and will have some antitheft measures built in.

Note that this has not been finalized. This is a progress photo. A few more wires need to be added before I can finish it off with loom and a vast quantity of zip ties.

The fuse/relay panel is mounted to the dash bar, beneath the airbag cutout in the dash. This keeps everything protected and out of the way while still easily accessible from inside the car. A stuffed turtle will be set on top of this panel as seen on the site banner.

At this point, all of the lighting works. The low beams, high beams, turn signals, tail lights, and brake lights are fully functional. Integration with the already prepared engine harness comes next.

Stay tuned for a more thorough post once the wiring is finalized.

Photobomb!

Posted on January 31, 2013 by admin

This is a post for some of the little things that currently sit at varying levels of completeness. Things that are not ready for their own posts, but still deserving of attention.

Firstly, some overall photos of the engine bay. You can see the custom coolant expansion tank that one of my racing buddies fabricated.

These holes allow cool air from the naturally pressurized cowl to flow into the passenger compartment.

Aluminium cover to prevent water from entering the vent holes.

Another aluminum cover to keep water out of the factory HVAC inlet.

The engine wire harness has been thinned. All unnecessary wires were removed. The wiring will get a dedicated post once it’s done.
This is the harness after I stripped the loom and electrical tape, and before I started removing wires.

The junk that I removed.

The harness, post thinning.

The harness reinstalled on the engine with nice wire loom.

The PCM was mounted in the passenger footwell via rubber vibration isolating mounts.

An aluminium shield protects the wires and connectors from unruly feet.

The factory crash beam was motivated to leave via sawzall. I did that to facilitate the removal and installation of the drietrain. I made a bolt in crash beam to put in its place. My structure seems to be of greater strength and since it bolts in, servicing the engine will be a breeze.

One of the best things about my new crash beam is that the OEM bumper beam fits snugly over it.

I needed more clearance between the front of the engine and the swaybar so I replaced the GTO harmonic balancer with the shallower CTS-V harmonic balancer. I now have ample clearance.

All of the old control arm bushings were removed via the Harbor Freight ball joint service tool. The ball joint tool made the job significantly easier. Stiffer urethane bushings will be going in their place once the arms are cleaned up and repainted.

The Canton Racing oil cooler was mounted. More on this later when I write a post on the oil system.

The Accusump oil pressure accumulator was mounted beneath the trunk pan.

The stout Getrag differential has been mounted to the Miata subframe.

It’s a big fellow.

A Walbro 255 fuel pump is now installed in the tank.

And there you have it–a shotgun progress update.

Pedals and brakes.

Posted on January 24, 2013 by admin

We all know the importance of reliable brakes. When you push the stop pedal, the car better slow down. No exceptions, ever. Ensuring that that is the case involves more than having physically strong components. The components have to be appropriately sized for the application, must be able to dissipate a sufficient amount of heat, and the components also have to be appropriate for the temperatures that they will reach(i.e. a track car requires pads that can handle hotter temperateness than a street car). How much heat do brakes generate under hard stopping? Well, brakes work by using friction to resist movement. Friction is what warms your hands when you rub them together. Now imagine that your hands were rougher, you pushed them together with 4,000 pounds of force, and you rubbed them together at 112 feet per second. The cited force is an approximation of what will happen when I start to brake at the end of a 150mph straight–112 f/s is the speed of the outsides of the rotors relative to the calipers at 150mph. This is true for each corner in the front, and the numbers for the rears are about 20% of the numbers cited for the fronts. Your hands will not hold up to that and a lot of brake systems will not hold up to that either. Lots of heat is created, and the amount of energy that the brakes must absorb is exponentially proportional to the velocity of the vehicle. The heat is dealt with by using large vented rotors, using pads that retain their coefficient of friction under extreme conditions, and in some cases, by ducting air to the rotors for additional cooling. I’m doing the first two, and may have to do the last as well–time will tell.

Under heavy braking, a larger portion of the mass of the vehicle is over the front wheels. On a Miata with significant grip, the dynamic front weight bias could be as high as ~80% under heavy braking. This means that if you want to utilize all available grip to slow the car down, the brakes should have the same front bias as the dynamic front weight bias. That being said, it is common to give brakes additional front bias for the sake of safety. The car would have a tendency to spin out if the rear wheels locked up before the fronts, so brake systems are engineered to have the fronts lock up first. My brakes are no exception to this, however I am using a balance bar for fine control over front/rear bias. The balance bar will allow me to make adjustments to the bias, while strapped into my seat, to optimize the settings for the conditions that I am driving under. Other ways to adjust the bias are to adjust the caliper piston sizes, the number of pistons in the calipers, the diameter of the rotors, the diameter of the master cylinders, and the friction coefficient of the pads. These same things can be adjusted, as well as the pedal ratio(think mechanical leverage), to alter the amount of force the driver must exert to achieve the same outcome at the wheels. One thing to be mindful of is that nothing comes for free–if you have a pedal that requires little effort, that pedal will also have to be pushed further.

For the rotors and calipers, I chose to go with a proven setup. I got the Trackspeed Engineering front big brake kit and M-Tuned caliper spacers for the rear. The front setup includes 11.75″ Wilwood rotors and 4-piston Wilwood calipers. The pistons are 1.38″ in diameter. The kit also includes brackets and stainless steel lines that make these brakes plug and play. Trackspeed Engineering’s attention to detail manifests itself in things like safety wire to keep the bolts that connect the rotors to the top-hats from backing out. They also provide a good set of installation instructions. The stock rear calipers will be retained and spaced out further via brackets to allow clearance for 10.9″ sport rotors, which came on the Mazdaspeed Miata. Wilwood master cylinders were used for the brakes and clutch. I am not going to share the specifics there because my master cylinder choices, as well as the pedal ratios, have yet to be tested and proven. That said, my math indicates that there should be no issues. The pedals themselves are from a 2004 Pontiac GTO. They came with my drivetrain and have been modified to suit my application. The modifications included cutting and welding to alter the overall lengths and pivot points. The gas pedal was the simplest part, and minimal modification was necessary. I welded mounts into the car for the gas pedal to bolt onto, and added a point to the pedal assembly to provide the throttle cable with a place to attach in the new configuration.

In addition to greater capacity, these brakes weigh less than the stock components, and consumable items(pads and rotors) will last longer and are cheaper to replace.

Early stages of the pedal box. The balance bar is clearly visible here. The pivot point is adjustable so the forces applied to the front and rear master cylinders can be varied.

This is the finished pedal box.

You can see roughly how the pedal assembly is mounted and also the addition of a switch, which will operate the brake lights.

Can’t forget the gas pedal.

All three can be operated as needed. The gas pedal was placed with heel-toe shifting in mind.

The plumbing still has to be done. Steel hard lines will be run through the interior to the front and back, and tee off at the ends to provide pressure to the calipers on both sides. The stock rear subframe comes with a tee fitting bolted to the passenger side. I relocated that to the drivers side to better accomodate my intended line routing.

Steering column becomes more…erect.

Posted on January 24, 2013 by admin

I have done a number of things to this car to improve the static front/rear weight bias, and amongst them was moving the drivers seat as far back as it can possibly go. I made a new seat bracket early on that moved the seat back and optimized the positioning of my custom pedal assembly to work with the new seat position. The pedals, however, are not the only control that I need to be able to reach. The steering wheel needed to be about 6.5″ further back. A simple means of handling this is to make a steering wheel extender. To do that, I merged the base of the OEM wheel hub, which bolts to the steering column, to the front part of my Sparco steering wheel hub, which the wheel screws into, with a spacer in between. The base of the OEM hub and the front part of the Sparco hub are both made of mild steel, and I happened to have some scraps of 2.5″ exhaust tubing laying around. I cut the tubing to the correct length and welded the pieces together.

After optimizing the distance between the wheel and driver, I had to optimize the angle of the steering column because the extender alone placed the wheel up far too high–the top of the wheel obstructed my view out the windshield. This meant lengthening the mounts that hold the steering column to the dash bar, lowering the steering column itself. I ground off the old mount and welded my longer mounts in place.

Firstly, the OEM steering wheel hub resembles a slice of bread.

This photo illustrates the excessive angle that was present, placing the wheel too high, before I updated the steering column mounts to lower it.

After I adjusted the angle.

Optimal position is generally regarded as when you can rest the bottom of your wrist on top of the wheel without leaning forward. I’d say this is dead-on.

An exhaust system that the neighbors will love.

Posted on January 23, 2013 by admin

There are a couple(two that I know of) aftermarket exhaust systems that companies have made for this particular swap. The available units are well constructed, however I thought that I could build an exhaust system that suited this car better, and do so for a fraction of the cost. So far, it is looking as though I have done just that. My top priorities for this exhaust system were performance and ground clearance. Performance is self explanatory. Ground clearance is also important because this car will be low to the ground and having various parts of it, namely the exhaust system, scrape the ground under certain conditions will make unfortunate noises and potentially cause damage. Stressing over the ground clearance of the exhaust system also provides more space for the addition of a full flat underbody, which has aerodynamic benefits, in the future.

I built this exhaust system from 2.5″ aluminized steel pipe. I chose aluminized steel because I can weld it with equipment that I already have and it provides some corrosion resistance. The pipes were cut by a chop saw with a friction blade. Mandrel bent tubes of two different radii and straight sections of pipe were purchased. Unnecessary bends were minimized for the sake of performance. The welds were intentionally made with a cooler setting than what would normally be advised. I did this to avoid excessive penetration, which would likely result in some extra turbulence in the pipes.

The shape of the system was chosen to maximize consistency between both banks of cylinders. Since the passenger side header lets out further forward than the drivers side header, and has a sharper bend to clear the starter motor, the x-pipe was placed closer to the passenger side to help even out the length of the two runs of pipe that lead to and from the x-pipe. The x-pipe is present to even out the pressure between the two sides of the exhaust system, allowing the system as a whole to be used more effectively. The x-pipe also results in a scavenging effect which helps exhaust gasses leave cylinders. A V8 engine has two banks of four cylinders. They fire at different times, and with each firing, a pulse, or pressure front/wave, passes through the exhaust system. Since the firing in the two banks is offset, an exhaust pulse from one bank flows downstream and reaches the x pipe when the valve, of the other cylinder bank, opens to expel combustion byproducts. (The time between those events depends on engine speed.) The effect of having a pulse from one bank enter the pipe for the other bank, via the x-pipe, is a vacuum which helps draw combustion byproducts out of the cylinder with an open exhaust valve in the adjacent cylinder bank. That increases efficiency and efficiency is the key to making power.

The system nicely tucks into the bottom of the car and does not have any apparent points of vulnerability.

The midsection of the system is supported by u-bolts which attach to steel braces that attach to the transmission side of the transmission mount. That way, vibrations are isolated from the chassis.

You may have noticed that this system lacks mufflers so far, or perhaps assumed that I do not value my sense of hearing. This car will not have much muffling, but it will have some so that myself and those around me can maintain some sanity. Magnaflow 6″ round mufflers are being used. They are about 20″ long and have a straight through design. They are not currently installed due to my running out of time, however they will simply be welded onto the end of what I have already made. I will trim the bumper cover more before I install the mufflers so that they can be mounted higher. I want to mount them as high as is reasonable to maximize the space left over for a rear diffuser, another aerodynamic downforce adder that I would like to make and install in the future.

Before trimming the bumper, the mufflers leave just enough clearance for a diffuser mounted at 10*. 7-10* is the commonly accepted sweet-spot.

This is roughly how the mufflers will look coming out of the back of the car. As previously stated, the bumper will be trimmed more and the mufflers will be mounted higher. I think they’re going to look great and sound even better than they look once I’m done.

TheTurtleBuild

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