FM4.1 0.) Custom FM4 Race Car Design #1

A high power light weight race car similar to an IMSA GT3 car but front-mid-engine all wheel drive, that can be driven on the street and goes around turns fast with lots of grip.

At the time of writing this post, this is the plan:

Design a custom frame in Fusion and have the tubes cnc cut, bent, and notched so they arrive ready to fit together and weld.

Use OEM factory parts for major components like engine, transmission, differentials, brakes, steering rack, etc.

3D Print digitally designed body parts in pieces, bond them together, use them as a plug to build a mold off of, and then make carbon body panels to fit over the custom frame.

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Specs

Power: 900-1000whp

Weight: <2500lb without driver

Drivetrain: Front-Mid-Engine AWD (FM4)

Engine: Toyota 2JZ-GTE I6

Engine Control: Motec M150

Fuel: E85

Transmission: AWD BMW ZF 8HP 8 Speed Automatic
or Quaife 91G Nissan Skyline GTR Sequential

Differentials: Ford 8.8″, Nissan GTR, or Subaru R160/R180

Suspension: Custom spindle and double wishbone to optimize geometry

Brakes: Chevrolet Corvette ZR1 Brembos

Wheels: 18″x12″ Square

Tires: 335/30R18 (25.9″x13.5″)

Frame: Custom tube

Body/Aero: Custom 3d Printed plug turned into mold for carbon fiber final layup

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Design Considerations & Constraints

• Guiding Concepts
  • Must be “streetable”
    • must run on fuel available at gas stations
    • must have a full charging system and cooling system for extended drives
    • must have a ride height that can make it over curbs and speed bumps.
  • Engine and Transmission both placed completely between the front and rear axle lines.
  • Use the lightest components that will achieve the end goal within my available funds at the time
  • Optimize center of gravity (keep things low to the ground and close to the middle of the car)
  • OEM Components should be reasonably priced and readily available when possible
• Suspension
  • Optimize Camber, Caster, Scrub Radius, steering angle for the frames dimensions.
  • Mount everything as close to the center of the car and as low as possible
  • Optimize self centering, roll, squat, and dive
• Steering
  • Make the steering as responsive as possible without instability in straights
• Power Delivery
  • Keep the torque high and the power delivery responsive for quick acceleration recovery existing corners
  • Shift using paddles on the steering wheel
  • Slip based traction control using all 4 wheel speeds.
• Braking
  • Make the car stop as aggressively as possible without making the car harder to drive fast into turns
  • Mount the brakes as close to the center of the ground and as low as possible.
  • Minimize unsprung weight and rotating mass

These are the initial building blocks of the plan. They may change, but many of the decisions from here will require an initial plan so this is the information those next decisions will be driven by.

Here is my tentative order of operations:

1. Pick a Tire
2. Pick an overall vehicle width
3. Use the tire dimensions to calculate Track Width
4. Use the track width to choose a wheel base within a track ratio of 0.55 to 0.65.
5. Digitally model the 4 tires on a ground plane at the appropriate track width and wheel base locations.
6. Choose an engine, transmission, and differentials that will fit within the track width and wheel base
7. Import scans of the engine, transmission, and differentials into the model and place them where they need to go in relation to the 4 tires.
8. Pick a wheel hub/bearing
9. Use the wheel hub/bearing dimensions to design a double wishbone spindle with a reasonable inclination angle that creates a zero scrub radius and has steering arms that point at the rear diff.
10. Choose a steering rack
11. Model the steering rack mounts so that it is in an optimal location
12. Use the completed hub/spindle dimensions to create a wheel with the necessary dimensions to fit
13. Model the lower frame tubes necessary to hold the engine, transmission, and differentials in place with removable subframes.
14. Import a sample exterior body scan to aid in the placement of various components like the drivers seat
15. Import a drivers seat model and place it in the best position
16. Design the control arms to attach the spindles to the frame via a removable subframe that also locates the differential. Include provisions for adjustability.
17. Design the steering tie rods to intersect with the instant centers created by the upper and lower control arms.
18. Design the push rod suspension. Locate the coilovers low and central. Design the bell crank push rod linkage.
19. Design a sway bar setup
20. Model axles that connect the spindles to the differentials.
21. Import scans of the brake calipers and rotors
22. Model brackets to mount the calipers to the spindle low and centralized.
23. Model steering shaft and column to steering wheel.

Disclaimer: At the time of writing this post, I don’t actually know how to do any of this. So I will have to figure it all out as I go.