Car ''tuning'' 101

[klorophil]

Hi there just thought that I might share with you a little guide that I made a while back for another forum.Well it's not exactly small but I think it might be useful to some of you if not just a good read.Back then I tried to cover the basics so I'll share this with you and try to improve on it.Since that time I learned an awful lot of things on car engineering theory so I'll modify my original text accordingly.Also if you do not agree with what I'm saying please feel free to reply.

For those questionning my experience and validity as a so-called tuning ''specialist'', well I have been tinkering with cars, especially import sport compacts since I was 15, so I've been doing this for the last 10 years or so.Also, I'm a trained car technician I graduated at Québec's Wilbrod-Bherer technical school in 2004, and I've worked at a BMW dealer for 1 year and am now working at a Subaru dealership.I also did 3 years of mechanical engineering.Like I said I repair cars as a living and also do many sidejobs by modifying rides.

So enough introduction into the meat of the subject.

[klorophil]

Improving your ride

So you want to make your ride faster, better looking or more comfortable.Well that's a good idea and it can be a lot of fun.It will also make your car unique and be custom tailored to your taste.Depending on what you drive there's an awful lot of parts you can install to make your car better.Even if you drive a rare one off, there are many things available in the car customising market.It's a huge place and if you don't want to loose money you need to be informed.That's what I'm trying to do here inform and help you decide what to do with your car.I will try to focus on the mechanical part of tuning, since that's what I know best and also because I'm not very interested in ICE (in-car entertainment).My background is also in mechanics so I don't know all too well body kits and the technology and craft behind them.Then again, most of the time what will be the most expensive are the mechanical bits so you need to know what you're doing.For example, a certain type of parts if not properly installed or if not chosen right can be detrimental not only to your engine but also to your safety.That's the whole purpose of this guide.To help you choose and research the right parts for your car.

One of the first step you should do is to come up with a budget and a plan.The budget part should be easy, and it's all up to you.With the vast choice you have before you, you can easily invest 500$ and make your car faster or spend 50k$ and have an undrivable monster.That's why you need a plan.That is you need to know what is the most important thing you want to change about your car.What is the purpose of your vehicle is it a comfy cruiser from A to B but with some added punch or an all out drag monster.This is very important as it will dictate what you need to do to your car to achieve your goal.This with a realistic budget should give you the ride you want and in a short amount of time and also hassle free, or almost.

To achieve the plan you need to know your car.What is it you don't like about it what is it you like.Every car that leaves the factory was built and designed with compromises.Suspensions, tires, engine everything was made to satisfy the biggest crowd possible.And do not ever forget that it was built with a budget.It's entirely possible that you do not associate with those boys and girls for which the car was built.So identify what you would have liked to have in your car.The feel of a car is entirely subjective so go with your tastes not those of others.

One very important thing to understand is that if you remove an OEM (Original Equipment from Manufacturer) part and replace it with an aftermarket one there's all the chance that it will show in your daily life with the car.If you're building an all out race car its not that important but for a daily driver it might be advisable to know the limits which you do not want to break.A triple plate clutch may reduce slippage but it will take the calf of Arnold Schwarzeneger to push the pedal and with a carbon/ceramic disc its either on or off.Not something I would recommend in town or during rush hour.Just remember that if you improve one aspect of a car there's likely to be another effect somewhere else and that it may not be to your taste.So that's why it's important to know what you're doing when modifying your car.

A word on warranties.Basically anything you do to the mechanical parts of your car will render the warranty null and void.I'm not a lawyer but thats the case most of the time.Also if you install a body kit and you have a body warranty regarding rust and perforations it's not too difficult to understand that it won't apply anymore.As for installing all these parts please try to find a trusty mechanic.You might be able to do a lot in your backyard but for certain things it's best to call in the experts.Mechanics are the only ones with the knowledge and manufacturer support to understand fully your particular car.Moreover, most of them will love you for making them install performance parts on a car.I should know because that's my job and I love it when someone asks me for a turbo upgrade.

So that's the first step next up is the Tires Section as I feel that's the first thing you should change in most cars.

[klorophil]

Tires

First, let me ask you this question what is it that makes you slow down when you apply the brakes.The obvious answer is the brake themselves but that is far from the truth.It is your tires.Sure the brakes stops the rotation of the wheel and it might be a good idea to change those if you are to add more engine power, more on that later.However, what really makes you slow down is your tires.It's easy to understand that when the wheel stops rotating your tires will also stop, then it should also be easy to understand that whitout proper connection to the ground all that stopping won't do anything as you will slide your way into the nearest lampost.So tires should be your top priority.A good set of rubber is what will make your car go fast, stop properly and corner with aplomb.

On a stock car changing for better tires makes the biggest difference.There are loads of makes and models of tires for your car you just need to find the one that fits your style.For example an extreme performance tire that is DOT-legal might be excellent on a dry track, but will feel like driving on ice on a greasy patch of wet road.So you need to know what you want to do with the car.See the plan is coming in again.Is it for the occasional track-day or for pure racing?Is it for some occasional run down your favorite road or for the quarter-mile?The answer to these questions is what will dictate your choice of tires.

[klorophil]

Tire size.

Every tire sold has a universal code on its side.I guess many of you are familiar with it.It might look like something this way: 225/45HR17.So I'll explain what all those numbers and letters mean.

225: That is the width of the tire from sidewall to sidewall in milimeters.This is handy when comes time to determine contact patch etc... Basically, the wider the tire the more grip it has.225 mm is 8,85 inches.

45: This is the height of the sidewall expressed as a percentage of its width or the tire aspect ratio.In this case 45% of 225 mm which makes 101,25 mm or 3,98 in.Theoritically, the lower the sidewall the more rigid the tire will be and thus the less contact patch deformation under load.Less contact patch deformation is good, it gives you more grip.I say theoritically because, there are certain everyday issues that become problems when you have too low a sidewall.

H: This is the speed rating of the tire.When a tire rotates it creates friction with the pavement this is what makes your car go forward or brake.However, this friction has some drawbacks.The one we are interested in here, is heat.Rub your hands together and they will heat up, well it's the same for the tire and the road.At high speeds this can be quite massive.Since your tire is inflated with air, this air will expand when its heated ultimately blowing the tire open.Not a good thing.Since, we are mostly concerned with performance cars here, it's a good guess to say that you will go fairly fast with it.Thus it's important to have the right speed rating.It's quite difficult to judge how faster your car will be after you tune it, that's a job for engineers.So as a rule of thumb, you should go for the highest rating available in the size you want.Most of the time that would be a Z rated tire.Note though, that not all manufacturers print the speed rating of their tires.As of 1991, tire manufacturers who sold their tires in North America were not obliged to print the speed rating on the tire.However, this is available in the tire service description.I'll touch this in a little bit.

R: This is the type of construction of the tire.R means radial, which in turn means that the layers of rubber and materials that compose the tire are laid radially around the center of the tire.There are 2 other types of construction and their associated letters.D is for diagonal which means that all the layers are criss crossing each other on top of one another.This is what is called a ''bias ply'' or ''cross ply'' tire.This is very uncommon for road tires.B is for belted.It's basically a ''cross ply'' tire but with metal belts under the tread of the tire.This is old-school, almost no road or race tires are constructed this way nowadays.R is what you will find and what I would recommend for road or track usage.

17: This is the diameter, expressed in inches, of the wheel that the tire can fit or its internal diameter.A WORD OF CAUTION! This coupled with the aspect ratio, will be used to calculate the outside diameter of the tire.It's important although not compulsory to keep that inside the OEM measurements.If not, your speedometer will read wrong.A bigger diameter, will make the speedo read slower than you really are, while a smaller diameter will do the contrary.While some modern cars can be calibrated correctly some of them don't.Also, ABS, variable steering, traction control and ESP all take into account the speed at which the wheel is turning.If you change the OEM diameter your wheels will turn at a different speed and it can mess with all of those.

[klorophil]

Tire Service Description.

Since 1991 new tires didn't show the speed rating as I explained earlier.This was replaced by 2 numbers followed by a letter at the end of the size code printed on the tire.It should look something like that: P195/60R15 87S.

87: This is the load index or how much weight 1 tire can support.In this case that would be 545 kilogramms or 1 201 pounds.

S: This is the speed rating of the tire.You have to understand that this is associated with the load index.The S here means that at 545 kg on each tire you can travel at speeds up to 180 kph or 112 mph.

545 kilogramms might seem really small but if you multiply that by 4 then you can put 2 180 kg of weight on those tires and still be able to traval at 180 kph.That's a staggering weight.Staying in the sport compact world, most sports cars weight in at 1 300 to 1 400 kg.Add maybe 100-200 kg to that for full passengers and fuel and you are still way far from the maximum weight permittable.I wouldn't recommend going 180 kph five up on public roads, while the tires, as demonstrated here, will be able to support the weight, that doesn't mean they will have the grip to turn or stop the car.

[klorophil]

UTQG.

UTQG is probably the most useful information you can find on any tires.UTQG means Uniform Tire Quality Grade, and it is just that.Each tire sold in North America has a UTQG number printed on it.It might look something like that: 140 A A.

140: This is the treadwear grade.Without going into the details of its determination, this is just how much the tread will wear over time and use.It's a comparative value, what this means is that the tire is compared to a test tire with known properties and then given a percentage of its durability over the test tire.In this case, it means that this tire will wear 40% slower than the test tire.The value of the test tire being 100 and this tire's value being 140.For anything used as a daily driver I would not recommend anything below 220.Normal all-season tires have a rating of 380 to 480.Note however, that in theory the softer the rubber compound of a tire is, the more grip it will develop but in turn will lose durability.Then, a low treadwear grade can promise more grip than a higher grade but it will wear faster.

A: The first A when there is a space between the other one, signifies the wet coefficient of fricition of the tire on wet concrete and asphalt test surfaces.There are 4 ratings, AA, A, B and C.AA is the best performing while C is the worst.While this is useful, it has to be taken with a grain of salt.Firstly, the way the test is done is by braking some wheels mounted with the tires until they lock, when this happens fancy electronic gizmos calculate the coefficient of friction.Thus, it could be said that this only reflects the capability of the tire to brake not turn.While this is true, in the real world two things happen.First, the same rubber compound is used for braking and lateral grip, so depending on tread pattern and tire construction we can assume that they will be fairly similar.Secondly, on a winding track or road, braking performance is the most important thing.You go faster by braking harder.

A: The other A is just another speed rating for the tire.A is good for above 115 mph, B is between 100 to 115 and C is between 85 and 100.Note that this is not very precise and I would normally use the service description to determine speed ratings.

[klorophil]

Tire Conclusion.

So that's about it for the tires.With the following information you can decide which brand and model of tires would best suit your needs.Also note, that living in Canada, I'm only familiar with what is available here.There might be other useful information elsewhere in the world.

Just a small note on the legal side of things.Here, in Canada, you cannot have a tire that is wider than the outside width of the car.There are ways of getting over this law and I will discuss them later when talking about wheels and chassis alignment.Also, no slicks are allowed on public roads.I know that there are DOT approved slicks available in the US but those are illegal overhere.A slick tire, is just a tire without any form of tread pattern or a very small one just to let water out, i.e. a racing tire.

A little word on tire pressure.On the side of each tire is marked the maximum inflation pressure.THIS IS NOT what is recommended by your car's manufacturer.This is only the maximum pressure the tire can hold.It is most useful for your mechanic when he mounts your tires on your wheels.Finding the right inflation pressure is fairly easy.This is written on a sticker, located either in the front driver's door or in the glovebox compartment.It's also available in the owner's manual.Having the right amount of pressure in your tire is of utmost importance for performance driving.While the tire itself provides grip, having it under inflated or over inflated will affect it's ultimate ability.It will also wear the tire faster.

So that's about it for the tire part.You can find lots of information here: http://www.tirerack.com as well as longer descriptions of what I just talked.Next up is the brakes.

[T-Bird]

are you going to talk about building forged engines and turbo upgrades/kits, fuel systems modifciations, ECU tuning and standalone operation etc... I'm in the process of doing all those things right now on a few different cars. just curious how in-depth you are planning on getting.

[79TA]

That all depends on how in depth his friend from the other forum originally was. So far it looks like basic tips for going after aftermarket parts.

[HeilSvenska]

Maybe there's more, but right now it seems more like tire buying guide. No offense, but it does seem like it.

[RC45]

And a word on the "warranty void" issue - this is not 100% accurate. And I would hope such a guide is quite accurate.

Maybe in communist canada they can void you warranty over trivial items, but the consumer int he US is protected - and the manufacturer can only void the warranty on the componet that was modified or componets reasonably affected by the mod.

So an airfilter mod wont void your tranny warranty, and a rear wing wont void the rust warranty on your hood

Oh - and this paragraph is very misleading:

Originally Posted by klorophil As for installing all these parts please try to find a trusty mechanic.You might be able to do a lot in your backyard but for certain things it's best to call in the experts.Mechanics are the only ones with the knowledge and manufacturer support to understand fully your particular car.

The dealership is going to be the first one likely to try void your warranty and most are ill equipped and less than enthusiastic about supporting any kind of aftermarket. Not to mention not every technician is, lets say - as detail orientated as one would want them to be.

Originally Posted by klorophil Moreover, most of them will love you for making them install performance parts on a car.I should know because that's my job and I love it when someone asks me for a turbo upgrade.

Then you and your dealership ar equit eunique and not the norm, I would even hazard a guess you are in the 1% minority.

[79TA]

hmm, perhaps a useful topic would be scheduling your family and friends to have a Saturday free so that they might have time to help you drop in a built engine . . .

sigh, I just hope I can get my engine in before 2008 ends.

[klorophil]

Originally Posted by 79TA That all depends on how in depth his friend from the other forum originally was. So far it looks like basic tips for going after aftermarket parts.

That is effectively what I'm trying to do.Also I have to rewrite pretty much everything as I did this guide a couple of years ago.Back then a) my english wasn't as good as it is now, so I have to make sure the previous sentences etc... makes sense and b) I learned a lot since then and find that many if not all the parts that I included are not 100 percent accurate.

Also, view this as only my opinion on tuning and modifications.

[klorophil]

Originally Posted by RC45 And a word on the "warranty void" issue - this is not 100% accurate. And I would hope such a guide is quite accurate. Maybe in communist canada they can void you warranty over trivial items, but the consumer int he US is protected - and the manufacturer can only void the warranty on the componet that was modified or componets reasonably affected by the mod.

They can and do void it.Moreover, in certain province like Ontario modified cars are frowned upon.I remember something from a minister back there saying something like this:
"If you drive a modified car, we will find you, find your car, take it to the crusher and crush it and all your modifications.You won't have your car anymore and all your hard work will be gone."

That was their transport minister quite disconcerting I would say.

Originally Posted by RC45 So an airfilter mod wont void your tranny warranty, and a rear wing wont void the rust warranty on your hood Oh - and this paragraph is very misleading: The dealership is going to be the first one likely to try void your warranty and most are ill equipped and less than enthusiastic about supporting any kind of aftermarket. Not to mention not every technician is, lets say - as detail orientated as one would want them to be.

That is what I'm trying to explain here, you've got to watch out for those things.So to be safe I said that it will be voided.Where I work we do install performance parts for the cars we sell, especially WRXs and STis, and those are guaranteed.But if you were to install parts yourself or from another garage then the engine is not guaranteed or the suspension parts etc... Honestly, I can understand why the dealer won't guarantee it because when time comes for them to get repaid by Subaru Canada it's tough to justify the repair.Keep in mind though, that's what we as the mechanics are being told.

[klorophil]

Originally Posted by T-Bird are you going to talk about building forged engines and turbo upgrades/kits, fuel systems modifciations, ECU tuning and standalone operation etc... I'm in the process of doing all those things right now on a few different cars. just curious how in-depth you are planning on getting.

This is more like a basic guide I consider those mods quite advanced.I'll touch them but no there won't be anything like: "How to choose the right turbo for x engine?" or "How to calculate cam durations?" etc...

Although, if you have questions regarding all of this or what you are trying to do I guess it would be ok for you to start another thread and ask specific questions there.I will be more than happy to answer all of your questions.