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So you want to modify your car.

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kamakazi
punchin NOS
Posts: 2862
Joined: February 14th, 2009, 10:32 am

So you want to modify your car.

Postby kamakazi » August 17th, 2019, 2:03 am

TLDR: IF there is anything I want you to learn from this article, (it is heavily opinionated :) )
• Understand that most upgrades involve tradeoffs. It is up to you to identify what they are and if you can live with them while not endangering everyone else.
• Proper Balance between all modifications is KEY. Too much in one area upsets everything else.
• Don’t waste money on unnecessary garbage(do your research). Identify what doesn’t make sense and ignore it. (unless that is your style and that is how you roll, in which case this article isn’t really meant for you)
• Sometimes first hand experience is the best experience so if you want to feel to learn, you can also go ahead and ignore this article and mod to your heart’s content
• Please modify safely.
• Never mentioned in the article but if you get it wrong, it can be costly


So you want to modify your car.
This is my attempt to dissuade young or new tuners from ill-advised mods. Seasoned people can ignore or feel free to correct and contribute. All these things are based on my observations and research and they are still just opinions. It is also my attempt to get new tuners to: understand/research what the mod does first before they make it, Identify what the tradeoffs are and decide whether you can live with it while not endangering everyone else.


First thing - set a target and keep it realistic
Identify what you want to do (goals), identify the platforms available (vehicles), identify the funds available (money), and identify the support available (parts and knowledge).
Ask yourself some questions:
1. what do you want to do: OEM plus, street rod, racecar, want to be faster than a Ferrari on a budget, just want to have fun in a car or modifying a car
2. What vehicle has the potential to meet the goal I specified (identify the strengths and weaknesses of the vehicle)
3. What is the cost of the vehicle
4. What is the cost to bring the vehicle up to the level that I want (remember the saying: CHEAP – FAST – RELIABLE....pick two); take into consideration availability of parts, the knowledge people have working on the platform, engineering work that might have to be done.
5. Can I afford it?
6. Is it more expensive than just buying the vehicle that already meets that goal or selecting another platform that is closer to your goal?
Knowing these things can help greatly in your decision-making process. It also helps if you understand the conditions the vehicle is going to be driven, to make an informed decision.

If you already have the platform and want to modify it. Well, that automatically limits you to the maximum potential of that platform but if it is in line with your goals go on to step two and modify it.

Second thing – Modifying
All parts that make up your vehicle inherently have a particular balance from the cheapest to the most expensive. Upgrading any of these components ultimately transfers the weakest link in any vehicle to the next component. Also performance and efficiency tend to be on opposite ends of the spectrum.
Off the bat, Racing components are not always suited to road cars.

ENGINE
Hint: set your goal and understand that all these parts/upgrades must form a cohesive unit to operate properly. Your goals and available money will determine the parts required to make it happen or if it can happen at all. Upgrading one component increases your potential to make power but doesn’t actually increase the power output by itself. They all require engineering and tuning.
• Engine management, Sensors
• Intake systems/Throttle bodies (larger or individual)
• Cams/valves/springs
• Pistons/con rods/crank/block
• Oil pump/baffled oil pan/accusump
• Fuel, Injectors, Fuel pump, Fuel regulator, surge tank
• Cooling
In some cases a sacrifice in drivability has to be made in the pursuit of power. The gains might also be very modest if there isn’t much displacement to make use of all the available potential of the parts in the build.
BTW you can indeed increase power output of an engine without upgrading any components but as mentioned earlier this is selecting the Fast and Cheap option so you will break something pretty soon if you go down this route.

Air filters
Air filters that flow more air (in favor of performance) has to reduce its filtration efficiency in order to achieve it. A filter that is 100% efficient does flow. As filtration efficiency is reduced, more dirt is allowed into the engine which reduces its longevity. Alright for racing as engines tend to be rebuilt more often, not so good for engines on the street. Performance gains are on average up to 1% and are only really available on the higher side of the rev range.

Expensive spark plugs
Expensive spark plugs by you longevity and maybe a little bit of horsepower but cheap spark plugs are just as good or even better in performance applications. Don’t waste your money on platinum and iridium plugs and especially any plug promising more power or stronger spark.

Expensive spark plug wires
Again save your money and buy a reputable brand and call it a day

Transmission
As you upgrade your engine power it has to be transmitted to the wheels somehow. You are now putting more power into a system that wasn’t designed for it. You now have to look at upgrading the components in your transmission. If you have identified your power goals and what you want to do with your vehicle, go ahead and select the appropriate parts to match, if they are available
• Clutch and Flywheel
• Gear sets (stronger and the ratios you want)
• Synchros
• Clutches
• Torque converter
• axles
• Or you can get a transmission built to your specs

LSD – Limited slip differential
If you are driving on the street I don’t see where you are going to save time by putting the power down one second earlier. Also doesn’t make sense if you aren’t struggling to put the power down after wheel and tyre upgrades.

Brakes wheels and tyres
Brakes
As you upgrade the power going to the axles, you will now need to be able to reign in that power. The brakes are going to be your next weakest link .Bigger brakes have the potential to stop you quicker, but doesn’t work if the tyres aren’t upgraded alongside it. (if the tyres lock up but the car is still moving: the brakes have done their job of stopping the rotation of the wheel and tyre, the tyres however haven’t done their job as the car is still sliding). The braking system should be upgraded holistically. If this isn’t done there is serious potential to upset the braking balance of a vehicle which can actually increase stopping distances or introduce strange handling characteristics (poor brake modulation, a stiff pedal with little brake assist, front or rear lockups, under or oversteer).
(what I mean by holistically: whatever you do, maintain a proper front to rear bias; if you upgrade your pads, upgrade the fluid and maybe your rotors to match; if you upgrade the caliper and rotor, upgrade your master cylinder and maybe your booster to match)
Cross drilled and slotted rotors: Cross drilled Rotors tend to crack under extreme brake use. Slotted rotors are better in this regard. They both eat up brake pads quicker.
Racing brake pads vs street pads: Racing brake pads usually need heat to perform so the first couple stops in the morning would be sketchy (they are actually worse than a street pad if it is cold. They also make a lot more noise and create more dust and wear out faster vs street pads.
Big brake kits allow you to stop more consistently lap to lap by keeping the temps within a working range (enough material to absorb the heat and enough surface area to dissipate it). I can’t see anything short of abuse creating this situation on the street but if you find yourself overheating your brakes on more than one occasion, this is a necessary upgrade for you

Wheels
Wheels and tyres have their inherent tradeoffs within reason
The bigger the wheel, the slower the acceleration is as metal is heavier than rubber and a bigger wheel is more difficult to turn. This doesn’t take into account sport wheels vs show wheels. Racing wheels are another story entirely (the trade off is they are extremely light and either sacrifice some strength or cost a fortune)

Tyres:
Narrow tyres vs wider tyres: Wider increases rolling resistance over narrow tyres which increases fuel consumption, increases steering effort and, increases lateral grip.
Bigger tyres vs smaller tyres (Circumference): bigger tyres effectively make the gearing taller (numerically smaller) and reduce acceleration.
Taller sidewall (high profile) vs shorter sidewall (low profile): Taller has slower steering response, a more comfortable ride and generally better acceleration.
Wheels and tyres are usually part of a combination so bigger wheels generally have a shorter sidewall tyre and vice versa for a small wheel. You trade off acceleration, fuel economy and comfort for steering response and lateral grip. Bigger wheels are also more difficult to stop turning so you potentially lose some braking performance.

High performance tyres vs economy tyres
High performance tyres generally have more grip (softer rubber compound) in the dry and usually trade off comfort, fuel economy, longevity and grip in the wet/cold conditions.

Contact patch
Generally the contact patch for tyres within reason has the same surface area. This area is altered by the type of tyre and tyre pressure, when the vehicle is stationary. It is more dynamic if the vehicle is moving. With that said a wider tyre has more lateral grip but has a higher potential to aquaplane in the wet and vice versa for a narrower tyre(it will have worse lateral grip but it has less chance of aquaplaning)

Suspension
Higher grip tyres will put more energy into your suspension and again all the components should be overhauled upgraded at the same time. Springs, dampers, sway bars, links, bushings. Upgrading one without the other has the potential to shorten the life of one of the components. Also upgrading without a planned path is setting yourself up for headache. Lowering a car without the proper components or alignment or without understanding what you are doing can make handling worse or cause parts to fail prematurely. The same goes if you lift your vehicle. These affect the alignment of the drive shafts coming from the transmission and places unnecessary stress on the velocity joints as they operate at increased angles and they will fail prematurely.
It goes without saying that stiffer springs, (even properly damped) will affect ride quality negatively.

Chassis
Beefier suspension components and stiffer bushings, additional weight and forces associated with bigger wheels, better brakes, sticky tyres etc. will put more energy into the chassis. This has the potential to bend or break the chassis components. So after all the above upgrades you are now looking at beefing up the chassis; Tower braces, chassis braces, fender braces, suspension attachment points etc. Some people might even go so far as putting in a roll cage. Funny thing is this adds more weight to the chassis and will cause you to go slower. A proper roll cage adds stiffness, but it adds inconvenience depending on if it is built to obstruct your ingress/egress of the vehicle. It also isn’t safe in an accident if your head smashes into it in an accident. (There is another reason while helmets are worn in racing cars).

Aero
Downforce usually adds drag, so depending on how aggressive the aero setup you either gain downforce and sacrifice top speed and acceleration, or sacrifice downforce to gain top speed and acceleration. In both circumstances, the front to rear setup has to be balanced accordingly and you lose fuel economy by having to overcome the drag.
Some vehicles are just more aerodynamic than others, and some actually have the opposite effect (they actually generate lift which is dangerous in a vehicle.
Aero is more functional if the components are attached to or supported by the chassis.

Other ancillary stuff
Steering wheel
Aftermarket wheels don’t really have airbags. Make sure you get a strong one with a good connection to the hub and steering column.

Bucket seats
You get more lateral support but there is the potential to be less comfortable than factory on longer journeys. Make sure it is secured properly to the chassis of the vehicle

Note: After all this there are still tradeoffs to consider. Your vehicle still isn’t the fastest thing everywhere e.g. Setup your car for smooth roads and it will be near un-driveable in the rough, etc.

kamakazi
punchin NOS
Posts: 2862
Joined: February 14th, 2009, 10:32 am

Re: So you want to modify your car.

Postby kamakazi » August 17th, 2019, 2:09 am

I got tired near the end so some parts are shorter :cry:
I am open to correction on everything said here. :D

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