I was toying with the idea of doing a similar write up myself but decided to use the forum search first to check who wrote what on the subject - just in case someone had already covered it. Turns out, that's exactly the case! Fantastic write up, tells it how it is. Sorry for necroing if you will, but I think this should be kept higher up in the suggestion section. Perosnally, I am a huge car fanatic and I absolutely hate seeing how even the most focused racing games dumb down car tuning to the point that it's no longer fun or challenging. Want a faster car? Buy LVL 1/2/3 package and you're done... yay... In reality, all the parts Thunderbee listed in one of the above posts often have to be ugraded on any car that is meant to make high power reliably. Tuning is a skill, it's also very involved and time consuming - but this makes it far more satisfying when it works. Engines have to be completely rebuilt with things like peak power, compression ratios (for N/A or Turbo), mixture, fuel octane rating and application (short drag races or long circuit races?) in mind. You CANNOT just buy a ''LVL 3 Turbo'' (wtf even is a lvl 3 turbo?!), slap it on and make power - only thing you can be sure of is you will destroy your engine without serious modifications if you do this. In a game, it would be no more difficult to implement than simply adding more menu options and items on a list to buy and build, then introducing power limitations on certain parts that would need to be upgraded if higher power levels are desired. This would allow players to build cars how they want to use them and give them more satisfaction and pride in their vehicle. Make tuning great again!!! I'd like to add a couple of points regarding actual tuning and... wheels, oddly enough. 1. Mapping Engines need to be mapped to make use of all the upgrades - or even to make them more efficient or slightly more powerful than stock. This introduces an opportunity for a ''minigame'' of sorts where a player measures the output of an engine (dyno?) and adjusts the map for improved performance. The more skilled a player is at this, the better this map and it's effects will be. Things like fuelling, boost targets and mixture ratios need to be set and corrected in order to maximise performance/economy. This means that if a player is good at this, an engine will have more power over a larger rev range and be more reliable, smoother and last longer. Bad maps will make less power, have more jerky power delivery, be less reliable and lower the lifespan of the engine. Such a minigame would DRAMATICALLY increase the level of involvement whilst keeping tuning fun and engaging. It would also mean that players could charge for their skills and tune cars for money for other people, contributing to the vast in-game economy and giving players more things to do in game. If someone is less skilled, they could just pay someone else to do it, meaning there would be a real incentive for players who are really interested and skilled in tuning to do what they do. There would NEVER be a maxed out vehicle - only more skilled tuners and more involved builds. 2. Wheels/Tyres A bit of a side topic. Games often not only simplify but downright OMIT 90% of these - often even in the real world drivers are completely clueless as to what wheel/tyre combos they run or SHOULD run. So here's an in-depth explanation regarding wheels and tyres as well as why it's important. In modern car culture, a good wheel fitment tends to make or break a car. It's only natural to emulate this challenge properly within a game. Wheels have a number of key parameters to keep in mind: - rims have parameters such as Diameter, Width, PCD and Offset. Diameter is how large the wheel is, Width is how... wide... it is, PCD relates to the bolt pattern (such as 4x100, 5x114, 5x108, 4x98 etc.) of the car hub that the wheel is meant to fit (WHEELS DO NOT FIT EVERY CAR!!!!! this is my pet peeve with racing games) and Offset is how far in or out the wheel is mounted on the hub. ALL of these (bar diameter) are often skipped completely in games. But these make fitment much more interesting and challenging. For example, you can't fit a wheel to a car that is the wrong bolt pattern. Wider wheels are wider in BOTH inner and outer dimension and you control how far they will stick out or in with Offset. Higher Positive offset means wheel sticks further IN, the closer to neutral (0) or negative offset you are, the further OUT a wheel will stick out. Spacers are also sometimes used to achieve this effect but choosing correct offset for application eliminates the need to spacers - thus saving money, weigth and potential point of failure. A typical rim will be denoted like this: 5x108 R19x9.5j ET35 - meaning it fits a 5x108 bolt pattern, it's 19'' diameter and 9.5'' wide and has an offset of +35mm. If it's fitted to a car with factory offset of say ET55, then assuming everything else is the same as factory, this wheel will stick outside by 20mm, giving a more aggressive look and stance while also improving stability. - tyres have parameters such as width, profile, load rating, speed rating and diameter. A typical tyre is denoted like this: 255/55R19 100Y What does that mean? Well, actually just like rims, this can be read as a sentence and tells you 99% of everything you need to know to make the perfect choice. 255 is the Tyre Width in milimeters. This is usually used in conjunction with Rim Width (in inches! some number conversion required) to determine the perfect tyre width. It's acceptable to have tyres wider/narrower than nominal rim width for fitment purposes, though not too excessive. /55 refers to profile. This is a PERCENTAGE value, it multiplies the width of the tyre to determine how large the side wall is - and thus how large the tyre is. The larger this number, the taller the side wall and so is the tyre itself. The smaller this number, the shorter the tyre is. Taller (larger) profile tyres deform more under load and cornering, lose traction more smoothly and gradually, flex more and are more comfortable.Usually madewith harder compound rubber, these often handle worse than low profile tyres and are less precise in handling but perfect for daily drivers, off roaders and drag race cars - which require a lot of flex in tyres to retain grip during launch. This is why dragsters often have massive tyres, as low profiles would lose grip easily with sudden acceleration, high profiles flex and keep gripping for longer allowing better launches. Shorter (lower) profile tyres deform less, flex less, are less comfortable and lose traction more suddenly. To compensate for lack of flex, these are often made with softer compounds - for physics reasons, this is why low profile tyres often are regarded as better handling for race cars. Softer compound grips more and less flex means driver is more aware of what their vehicle is doing. R19 refers to the rim size the tyre is meant to fit. It will ONLY fit rims of exactly the same diameter! 100Y is actually TWO parameters - the number 100 denotes LOAD RATING - or how much weight can be put on a tyre. Heavy cars will have higher numbers, light cars will have lower numbers. The letter Y refers to SPEED RATING - in this case, Y means this tyre is good for 186 MPH (or more). Speed rating basically means how fast the tyre is meant to go before it fails (or how fast you can go safely with this tyre). There are other ratings such as how lound the tyres are, wet grip and fuel efficiency. These can often be skipped, however for each individual build they are still important factors. Louder tyres will be... louder. If you build a steathy or comfortable car it's important to go for quieter ones. Fuel efficiency relates to the rolling resistance of the tyre - the worse this is, the worse your fuel consumption but sometimes your grip will be better as a result. Wet grip is important for anyone who plans on driving their car in all weather conditions and not just perfect sunny track days. If this is low, you may suddenly find your race car is unable to turn a corner at all after a light mist and your performance will suffer. For game purposes, this isn't very important really, not nearly as much as the other parameters anyway. There are also special racing tyres - slicks and semi-slicks, with little to no tread offering INSANE, almost cheat-like grip. I actually drove cars with racing slicks and they feel almost glued to the road compared to regualr road tyres But these are illegal for road applications. Something to keep in mind for tyre choice on your builds So why does ANY of this matter? Well... For looks, you often want a larger and wider rim. But to compensate, you need to select the proper tyre to fit your car. Too large and they won't fit/will rub on arches. Too little and you risk damaging your wheels and making the car unbearable to drive. Any change in total diameter will also change your gear ratios and throw your speedometer out. If you ''stance'' out your car, you may need narrower ''stretched'' tyres to fit your car without having to perform extensive body work mods.Choosing a smaller rim than stock may not always be possible because of clearances around brakes and other components - you need a rim at least of a certain size to fit a vehicle without issues. If you want slightly more agressive fitment, a lower offset and wider wheel will often be enough to go from granny mobile to mean race car look. Once you understand how these parameters work together and relate to one another, it becomes very easy to determine what you need for the perfect look and performance. For example, narrower tyres are better for dirt, mud and snow as they dig in and grip this way. Wider tyres are better for tarmac and smooth, hard surfaces. Larger wheels are better as a cheap alternative to increasing your gearing (gearbox work is EXPENSIVE!!). To help understand this better, there are tools online which help you compare wheel/tyre combos and determine what is perfect for you and your car. Search ''Rims N Tyres'' calculator - it's the perfect tool and visual aid to help you understand everything there is to understand about this. I know this got lengthy fast, but I hope it was clear enough for anyone to understand. These things matter, if you have a car in real life, chances are you will have encountered this problem yourself - and this is precisely why everyone should know what this means and how it all works. Understanding the basics means you can choose any combination of these to achieve the perfect fit that you desire. Emulating this in a game would greatly increase depth and provide an added layer of realism, even if tyre behaviour is greatly simplified. TL:DR I just want to see ONE RPG which gets car mods right and rewards people who take their time and interest in those things. Add depth and make things more interesting. Also, I don't mean to hijack the thread, only to contribute. Peace!