Drivetrain
Throttle cable: This is an important component to periodically check. Often, the cable will loosen (have too much slack) and prevent the throttle plate from opening fully at WOT (wide open throttle). If the throttle fails to open fully; it’s to the detriment of engine performance. This is a very common issue that late-model drive-by-wire systems eliminate.
Throttle body/ intake manifold cleaning: Even with the best filters, the bodies and plenums of intake manifolds get coated with debris that negatively affects airflow and engine performance. To remedy this use carburetor or throttle body cleaner (either is effective) and spray it directly into the intake past the throttle plate. The engine will have a tendency to bog. As this occurs, manually open the throttle just enough to keep it running without over-revving it. It’s critical to use caution and prevent any foreign object (EX: the cleaner straw/nozzle) from entering the manifold. This process can require up to a full can of cleaner. Carefully clean the throttle plate and bore as well. Often a good indication of cleanliness is a slight hissing sound emitting from the throttle plate at idle.
Air filter/intake positioning: Cold air intakes are effective in real-world use, but they aren’t available for all vehicles. To maximize airflow, remove or relocate items/components which block intake airflow. For example: third generation Honda/Acura Integra coolant reservoirs can be relocated for less obstructive airflow. Additionally, conical filters with breathable filter end caps are superior to their single-surface brethren. Most vehicles provide decent intake routing from the factory which usually provides an opportunity to enhance flow with a simple filter upgrade. Depending on the factory design, consider air box removal/replacement/modification. Experimentation is an unavoidable part of the process with custom setups.
Engine internal cleanliness: The cleanliness of the engine rotating assembly and piston rings are critical to efficient engine performance, but are commonly neglected. To maintain cleanliness, either purchase oils with detergents or add engine oil detergent separately. Consider adding a separate engine detergent roughly 240km/150 mi before the vehicle’s scheduled oil change interval. A neglected, sludge-filled engine will significantly liquefy the debris in approximately 160km/100 miles. The best time to change the oil will be when the engine revs with a buttery smoothness (approximately between 160km-240km in warm weather). An alternative is performing an engine flush at the oils change intervals.
Engine oil: Depending on the application, consider custom oil blends. In real world usage, a custom blended mix can provide enhanced protection with minimal piston ring blow by. Consider blending (EX: with a five quart capacity crankcase) three quarts of conventional oil with two quarts of full synthetic. Do so while utilizing the recommended oil weight for the engine. Older/high-mileage engines generally suffer more from piston ring blow by. Often, synthetic oils are less compatible in such applications.
Engine sound: While this parameter is subjective and variable by vehicle and configuration, it’s the concept that is important to consider. An engine is an air pump…or could be considered a musical instrument not unlike a trumpet or pipe organ. Both contain valves and manipulate air to varying effect. This is important because being able to discern a vehicle’s running condition by sound is a valuable ability to hone. Simply stated; a proper running engine should sound “good” while an improperly running one generally won’t. Also, listen for tapping noise from the valve train. It’s common for older MX-5s to need valve lash adjustments at regular intervals.
Quality spark plugs/wires: While often overlooked, plugs and wires properly chosen/gapped and routed will enable optimum combustion.
Engine sensors and injector cleaners: Ensure that all sensors (oxygen, MAP, etc) are functioning properly as malfunctions will reduce engine performance. Bottled fuel injector/fuel system cleaners added to fuel are effective and utilized by certified mechanics and dealerships.
Manual transmission oil: Depending on the application, consider upgrading the case oil to a quality, full synthetic or blend. This provides a noticeable difference—particularly in front wheel drive applications. For older Miatas, consider utilizing Red Line Oil‘s MTL. It can often help to remedy noisy gearbox synchros.
LSD: Regardless of vehicle drive configuration, a limited slip differential is usually a benefit.
Suspension
Proper strut/shock/spring combination: Evaluate ride and handling goals and experiment. The optimal solution will depend on those goals and the budget. Choices, obviously, are unique to the chassis and driver. If on a limited budget, consider purchasing used Bilstein struts which can be rebuilt by the company with custom valving for specific applications. Bilstein struts are high quality and have been offered as OEM components on Miatas.
Sway bar links/Polyurethane bushings: Regardless of the application or specification, the sway bar(s) and end-links are critical to vehicle handling ability. Evaluate and consider swapping inadequate/poorly designed end-links for aftermarket/superior units. For example: the third generation Honda/Acura factory front sway bar links are constructed using relatively fragile plastic joints. Consider replacing them with either aftermarket, competition units or OEM Nissan S13 units. End-links that fail unexpectedly can be problematic. In addition, consider upgrading the sway bar and end-link bushings with polyurethane replacements. End-link bushing are generally overly thick where they connect to the lower control arm. Depending on the application, consider cutting them in half for less flex and increased steering response. Also, do not ignore the contribution of bump stops as they prevent abrupt disruptions to suspension articulation. Polyurethane bump stops are available and can be cut down the owners desired height. Upgrading the sway bar bushings to polyurethane will help to ensure the effectiveness of the bar.
Alignment: A properly aligned vehicle will best utilize the suspension geometry and minimize rolling resistance.
Tire profile/quality/air pressure: Consider experimenting with tire pressures for street usage, not just the track. A tire is the first point of of flex in every setup. When choosing tires generally opt for the lowest sidewall height for optimum handling performance. However, because high sidewalks flex over a greater distance, they can be chosen for more gradual response/grip levels at the limit or during transitions. In addition, most mid-range performance tires can benefit from cold tire pressures up to 45psi. For street use, the heat cycles are generally less demanding than on the track and enhanced cornering performance and reduced rolling resistance can be achieved with carefully chosen, application-specific pressures. Think of the tire as a variable component of a suspension setup and dial pressures in accordingly for performance/ride goals. Please note that higher pressures can easily highlight a suspension setup’s shortcomings and are generally best suited for warm, dry road conditions. Also, be sure to purchase the best quality tires for the application. Remember tires are important since they are (ideally) the only part of the car which actually contacts the road.
Reduce drag on wheels: Attempt to reduce the drag on the spinning motion of the vehicle’s wheels. Properly balance the wheels and replace or upgrade worn wheel bearings. It’s also important to properly maintain the brake system to reduce/prevent excessive brake pad drag.
Chassis
The unfortunate truth: Most contemporary sports car chassis are unibodies and this isn’t the optimal manufacturing method for a high performance chassis. While cost effective (and budgeted down to the price of each spot weld), unibodies are fundamentally flawed by design and in execution. Even niche vehicles like sports cars have to cater to a broad segment of the population in order to sell. This means that packaging designs are innately compromised in regards to rigidity for the sake of utility. It’s beneficial to research superior carbon fiber monocoques as well as space frame chassis design. The development of 3D printed vehicle chassis is also notable. The future is bright, but the unibody chassis is a dated, inferior process in regards to structural rigidity.
Tune and balance a vehicle’s handling with fuel level: In addition to providing energy, fuel can serve as ballast. Fine tuning a vehicle’s driving dynamics can be accomplished by varying the amount of fuel being carried. This technique is especially effective with vehicles with 50:50 weight distribution like the Mazda Miata or Honda S2000. There is the added benefit that the weight is also located low in relation to the vehicle’s center of gravity. Obviously, in order to maintain the desired driving dynamics, the fuel level must continually be monitored. This parameter varies whether used to the driver’s benefit or not. By carefully accounting for the weight variance, a driver can use it to their advantage.
Door alignment: The door openings of a vehicle are notable weak points in the chassis structure. By properly aligning the doors it’s possible to maintain the maximum level of chassis rigidity designed into the chassis from the factory. Misaligned doors do not tie the body structure together as intended and therefore enable excessive flex. It’s usually older chassis which suffer from these issues since newer models are generally better designed. Observe the brilliant door designs of the Mazda RX-8 and the R35 Nissan GTR.
Reduce weight: This can be done many ways with the biggest benefits being weight losses highest above the vehicle’s center of gravity. Simple weight losses can be made by upgrading to lightweight wheels, battery and/or removing sound deadening from the trunk or interior. Obviously, weight loss can be extreme, but there are many creative ways to reduce weight without sacrificing utility. Body panels can be replaced with lighter components and options like sunroof assemblies can be removed and welded closed to save a few noticeable pounds. Unused or faulty items like malfunctioning air conditioning compressors or windshield washer reservoirs are also prime candidates for removal.
Lastly, if a hardtop is utilized, consider removing the soft top and its components entirely. Many MX-5s are heavier than necessary simply due to the redundancy of carrying the weight of two tops.
Make it quiet/rattle free: This is skill that will innately enhance your chassis knowledge through practical analysis. Body creaks, cowl shakes and interior panel shimmies are all clues to areas where the chassis is likely flexing. It’s important to gain the ability to discern between problematic structural areas and irrelevant, interior fitment imperfections. Common areas for flex in unibody chassis are the firewall, door/hatch openings and strut towers. It’s also valuable to become familiarized with good chassis design. Observe the details of a finely designed chassis and analyze it. Late model Subarus are generally exemplary examples of chassis design. Note the thick door sills and research the their multi-panel approach to their structural design elements. Additional knowledge can be gained by studying flawed chassis as well. For example: a Nissan Fairlady Z/Datsun 240z is a popular chassis, but succumbs to many flaws. Aside from thin sheet metal and inadequate reinforcement, it also (like many cars of the era) suffers from the lack of substantial A-pillars…not to mention the absence of B-pillars at all.
Triangulate the upper support: The firewall is a major stress point in virtually every chassis. The flex of this region of the chassis can result in everything from cowl shake, traction deficiencies and even (in extreme examples) cracked windshields. Triangulation of this area is nothing new, but surprisingly still neglected by some manufacturers. Strengthening this area with either an aftermarket reinforcement panel or a DIY welded reinforcement can greatly aid the rigidity of the chassis (especially when combined with a three point strut tower brace). Please note that any reinforcement to this area alters the crumple zone stresses of the vehicle. The Toyota 86/Subaru BRZ is a great example of good use of this structural element. Strangely, popular sporty platforms like 90’s Civics/Integras lack this structural element.
Install a proper driver’s seat: Choices abound with many aftermarket and OEM options available. Choose a seat with the most rigid structure as possible. Driver comfort should come from the seat foam and not from a flexing seat shell. Ensure that the seat sliders are firm and bolted properly to the floorpan. Doing this ensures that the driver’s body is receptive to the impacts and undulations of the road (IE: important communication from the vehicle/road surface).
The driver: Developing driving skill is invaluable and the knowledge retained is useful in every subsequent vehicle experience. In addition, take the time to evaluate project goals and choose the proper platform. Oftentimes, it makes more sense to change platforms than to waste time/resources on a vehicle that cannot reasonably perform to the driver’s expectations.
*The above streetwise tech tips have been evaluated and are intended to improve a driver’s daily enjoyment of their vehicles. The reader is responsible for their vehicle/behavior both on and off public roads.
