FAQ

About this Blog...

There is an old saying that I like that goes “the only stupid question is the one that isn’t asked”.

When it comes to improving your car’s performance, more than likely you have more questions than answers. I know that I do. So with this in mind, I decided to create a “Frequently Asked Questions” blog.

Part of the reason for this is that when you decide to start modifying your car, you have a lot of the same questions that we all did when we started out, and no matter what you have done to your car, more than likely you are looking for the next thing you can do to make your car go, stop, or turn faster, and you might have a question or two…

Our goal is to make this “FAQ” blog into a resource for anyone from someone that is just starting to modify their car to someone that has put in a fully built engine or two, and is still looking for an answer a question.

To begin with, we are going to put up commonly asked questions, and our answers to them. However, if you don’t see the question that you have, feel free to post it as a reply to this first post, and we will do our best to answer it. Also, if you read an answer, and it sparks another question, feel free to ask it as a reply to this first post as well, and we’ll do our best to answer it too.

The only requirement that we have is that your questions stay on topic.

Thanks for looking and please check back often as hopefully this will continue to grow into a large resource as more people become aware of it.

Jon Cooley

What is the difference between Horsepower and Torque?

If you are thinking about improving your car’s performance by bolting on anything from an intake and exhaust to fully rebuilding your engine with different cam’s or pistons, it is very helpful to understand the relationship between torque and horsepower. The trouble with talking about the difference between the two is that there isn’t that much of a difference really.

In an internal combustion engine, when you ignite your air/fuel mixture, this causes the gas trapped in the cylinder to expand rapidly, and push the piston down. The piston is connected to the rod, which is connected to the crank, and as the piston is pushed down, that forced is translated to the crank. The twisting force exerted on the crank is also referred to as torque. Or, to simplify things, Torque is the amount of force the piston is pushing down with.

So what is Horsepower? Horsepower is a measure of the amount of Work the engine does over a given Time.

The basic definition of Work is:

Work = Force x Distance

Therefor: Horsepower = Force x Distance
                                         Time

But what we are talking about here is the relationship between Horsepower and Torque. Torque is basically the force that we are talking about in the above equation. So if we substitute that, and clean things up a bit, what we are left with is the following equation:

Horsepower = Torque X RPM
                             5252

This actually tells us a lot of interesting things. The first is that at 5252 RPM, an engine’s Horsepower should equal its Torque. I think that you will find that if you look at pretty much any dyno plot of any car, the torque curve and horsepower curve will cross right around 5,200 rpm’s.

The next is that no matter how much torque our engine makes, the amount of horsepower that it produces is directly dependent on how fast the engine is spinning.

Ever wonder how a Honda S2000 can make 230 Horsepower, but less than 200 Ft Lbs. of torque? Well, the early 2.0 Liter S2000’s have a 9,000 rpm redline. If it is spinning that fast, it doesn’t have to produce a lot of torque to make a lot of power. If you plug 230 horsepower and 8,000 rpm’s into the equation above, you should find that you only have to make 150 Ft Lbs. of torque to generate that much power.

Now, the flip-side of this is a diesel truck can make 1000 Ft Lbs. of torque, but only makes 500 – 600 horsepower. This is because a typical diesel engine might have a redline of only 3,500 rpm. If you plug in 1,000 Ft Lbs. of torque, and 2,000 rpm’s in to the equation above, you should see that you would only be making about 380 horsepower.

Lastly, what this means is that there is no reason that an engine will make its maximum horsepower when it makes maximum torque.

So if we want to make more horsepower, we really have two choices. The first is to make more torque at a given rpm. The second is to make our torque curve fall off more slowly, or in other words to make more torque at a higher rpm. And actually, if we could get our engine to make the same amount of torque over a wider rpm range, that would also produce more horsepower.

Lastly, to get a sense of how torque and horsepower relate, here are a few comparisons keeping horsepower or torque constant over an rpm range:

200 Hp at 2,500 rpm = 420 Ft Lbs. of torque
200 Hp at 5,000 rpm = 210 Ft Lbs. of torque
200 Hp at 7,500 rpm = 140 Ft Lbs. of torque
200 Hp at 9,000 rpm = 116 Ft Lbs. of torque

What this shows is that at a lower RPM, an engine must produce substantially more torque to produce a given amount of horsepower than it does at a higher RPM.

200 Ft Lbs. of torque at 2,500 rpm = 95 Hp
200 Ft Lbs. of torque at 5,000 rpm = 190 Hp
200 Ft Lbs. of torque at 7,500 rpm = 285 Hp
200 Ft Lbs. of torque at 9,000 rpm = 342 Hp

This shows us that if an engine can produce the same amount of torque at a higher RPM, it will produce more horsepower.

J. Cooley

What does an Access Port do exactly?

If you have been reading about Cobb’s Access Port, or engine management for that matter, you have probably come across the term “Re-Flash”.

There is a computer in your car that is in control of all of the engine’s running parameters, and it is constantly monitoring information from a number of different sensors to make sure that your engine is operating at its peak performance.  The term “Re-Flash” refers to going in and changing some of the parameters that your cars’ computer is using with the goal of improving your engines’ performance.

Simply put, the Access Port plugs into your OBDII Port (which your car all ready has), and is able to communicate with your cars’ computer and give it a new set of parameters.  The Access Port can change things like Ignition Timing, Fueling Curves, Boost Curves, etc., and by doing do, it will allow your motor to produce more power.  Once it up-loads these new parameters to the cars computer of ECU, they are saved so they will remain there until you choose to change them. 

This process of up-loading new parameters is called “Re-Flashing” your ECU.

One interesting thing about Cobb’s Access Port, which is unique, is that it can do two different kinds of “Re-Flashes”.

The first is called installing a “Base Map”.  If you think of your cars’ ECU in terms of your home computer, it is actually similar in that it has something equivalent to hard-drive memory, and RAM memory.  When you install a “Base Map” (as you will have to when you install your Access Port for the first time), all of the new parameters will be saved to the ECU’s hard-drive.  That means that they will remain there until you choose to change them, or remove them, even if you re-set the ECU, or the system loses power, etc.

The other type of Re-Flash is called a “Real-Time Map”.  This Re-Flash is not saved to your ECU’s hard-drive, but is rather saved to your ECU’s RAM.  This kind of Re-Flash goes much quicker than a Base Map, but it is not as permanent.  Because it is only saved in the RAM, if you re-set your ECU, or the system loses power, the Re-Flash will be lost.  For this reason, it is better to use this for a Re-Flash that you won’t need permanently such as a “Valet Mode” Map.

So if all you are doing is changing the running parameters of your engine, how much power can this really make?

Well, the answer to this is a lot. 

Cobb has posted Dyno Charts of their Stage 1 maps, and in virtually every case, a car can gain a substantial amount of power just from a re-flash of the ECU.  For instance, here is their Dyno-Chart of a Stock 2.0 Liter WRX compared to the same car with thier Stage 1 Map on it:

   

The other thing to keep in mind though is that the Access Port will also give you the ability to load a MAP that goes with other parts you put on your car, such as a Turbo-Back Exhaust.  If you compare the Dyno-Charts of Cobb’s stage 1 to their Stage 2 (which includes the addition of a full Turbo-Back exhaust with a corresponding Re-Flash), you can see that there is a definite difference in power.  However, if you were just to put on the Exhaust alone, you wouldn’t realize nearly as much of an increase because you haven’t changed your engine’s running parameters to go along with your new exhaust.

Jon Cooley

How do I convert PSI to Bar to MPa?

This question comes up quite a lot, and fortunately, it is actually pretty easy.

1 Bar refers to 1 atmosphere of pressure.  This is equivalent to 14.5 psi, or .1 Mega Pascal, or Mpa.

In other words:

1 Bar = 14.5 PSI = .1 Mpa

For example, if you have a gauge that is reading .5 Bar:

.5 X 14.5 = 7.25 PSI

One of my friends happens to be an engineer, and he kindly informed me that my example above was just a rough approximation at best.  The correct equivalencies are as follows:

1 bar = 14.50377 PSI = 0.9869233 ATM = 0.1 Megapascal

That being said, most gauge's aren't going to be this accurate, and are really just an approximation themselves, so in the real world, I'd still recommend going with the first approximation.

Jon Cooley

What are the differences between a Strut & Spring Set-Up compared to a Full Coilover Suspension?

There are a couple of big differences to keep in mind when choosing between coilovers and Strut/Spring Combo's.

First is that there are a lot of springs out there, but many of them are designed to give the car a certain "look" rather than improve the car's handling, and these usually end up lowering the car too much. When you are picking a Spring, or a coilover for that matter, you have to decide if you want the car to handle better, or if you really want a dramatically lowered look, and understand that if you mainly want the car lowered, there will most likely be some trade off's when it comes to handling and strut life.

The next thing to consider is that a well designed coilover has a spring rate and damping rate that are designed to work together. A lot of what you get when you pay for a quality coilover is the research put into their development. This can make your life a lot easier because all you have to do is bolt them on, and adjust the damping a little (if the dampers are adjustable), and away you go. When you buy a strut and spring separately, sometimes you end up doing the R&D yourself. That being said, there are a lot of combo's out there, and hearing what other people have tried and liked can point you in the right direction. Generally, I would say that as long as you shoot for a spring that doesn't lower the car too much (about 1" or so in front, and the same or less in the rear), and a damper that is a bit heavier than stock or is adjustable, you should have a good chance of being happy with your set-up.

Last is adjustability. Coilovers have a lot more adjustability than a strut/spring combo. Ideally, you would want a coilover that is double adjustable, which is to say that you can adjust spring pre-tension/spring seat height independent of ride height(moving the entire damper up and down). The advantage of this is you can raise or lower your car without losing suspension travel, or changing spring pre-tension. This can be really handy, however, you need to set them up correctly, otherwise you can actually do more harm than good. For many people, this may very well be over-kill, and for a car that is mostly driven on the street everyday, etc., this may very well be more adjustability than you will ever need.

If you are concerned about your suspension being too stiff for every day driving, you will most likely be happier going with a set-up that has a softer spring rate that will give you the ability to ratchet up your damping rate as needed. Suspensions with a higher spring rate, versus a higher damping rate will behave differently, but if you want something that will be softer on the street, focus on the damper, because that can be changed, spring rates on the other hand are pretty much fixed.

Jon Cooley

What is “Blow-By” or is it normal for my car to have oil in the intake plumbing?

In your motor, the piston is moving up and down in its cylinder, and the rings on the piston are creating a seal so that when you ignite an air-fuel mixture, that reaction is converted into power.  As good a seal as the rings make, they will never be perfect.  What this means is that some of that expanding gas will get past the rings, and then it will be present in the crank-case.

First, keep in mind that we are talking about a very small percentage of pressure here (as long as your engine is in good running order), but that pressure still has to go somewhere.  For this reason, your car has a Positive Crank-Case Ventilation (or PCV) to release this pressure, and it will rout it back into your intake system.

There are two reasons that this is sent back into the intake, rather than being sent out to atmosphere.  The first is that Automobile manufacturers aren’t allowed to emit anything directly to the atmosphere for environmental reasons.  The second is that it can actually be advantageous for there to be a slight vacuum present in the crank-case because then there is less on the piston’s down-stroke.

However, because this air comes from the crank-case where there is a lot of oil present, this air usually has some oil vapor present in it.  This oil is also referred to as blow-by, and in moderation, it is completely normal.

In a Subaru WRX for instance, it is completely normal for there to be a thin film of oil present on the intake plumbing, and for there to be a drop or two of oil pooled between the intercooler and throttle-body.  That being said, if you find a more substantial amount of oil present, it could be indicative of a larger problem, so it would be a good idea to find out the cause.

If you are running more boost than stock, there is a chance that you will send more oil through your PCV system.  This will especially be the case under hard driving.  This is partly due to the fact since you are pushing more air into your motors cylinder, there is more air (under higher pressure) that is getting past your rings.  This is one reason that it is a good idea to keep an eye on your oil level in between track sessions, and in between oil changes for instance.

One way to help minimize oil getting into your intake is to install an Oil Catch Can.  The idea here is that you will cause a drop in pressure, and cause the air coming out of your PCV system to make a sharp turn before entering your intake, and this will cause most of the oil present to get trapped in the Catch Can.  Most Catch Can’s also have a level indicator, so you can see how much oil you have accumulated, which can be a helpful tool to remind you to top-up your oil.

If you install a Catch Can, and you see that you have an excessive amount of Blow-By, you may want to have a mechanic inspect you car, and do either a Compression or Leak-Down test to make sure that your rings are still creating a sufficient seal with your cylinder-wall.

Jon Cooley

What is Boost Creep?

If your car is suffering from Boost Creep, here is the behavior you would see.

Assuming you are accelerating in one gear at full throttle, you will hit your target peak boost (the most boost that you want to make, say 15 psi) at a certain rpm, let’s say 3500 rpm. Then as you continue through the rpm range, you should see your boost pressure begin to taper off, say after 4500 rpm.

If your car is suffering from Boost Creep, what you will see is at some rpm after your boost begins to taper as normal, your boost pressure will begin to build again, and if it does, it most likely won’t stop until you let off the accelerator. It will also most likely build well beyond your target boost.

So what causes this?

What your car uses to control boost pressure is the turbo’s waste-gate. This is simply a door that opens up in order to direct exhaust around the turbine to relive pressure and slow the turbine down. Basically, the more the waste-gate stays shut, the more pressure builds, and the faster the turbine spins, and the more it stays open, the less pressure builds up, and the slower the turbine spins. Your car (or boost controller) will modulate the waste-gate frequently to maintain boost pressure…

In the case of Boost Creep, what happens is that in high rpm’s, your engine is pushing out so much exhaust that even with the waste-gate remaining open, it isn’t able to divert enough gas to keep the turbine from spinning faster, so your boost pressure continues to build. This is a problem because boost pressure will continue to build uncontrolled, and it may push past the point where you still have adequate fuel capacity, and cause a lean running condition.

Also, one of the reasons that boost normally tapers is because as the exhaust flow increases as rpm’s increase, it will actually push a turbo out of its peak efficiency range. This means that the turbo doesn’t make the same pressure as efficiently at a higher rpm as it does at a lower rpm. The less efficiently a turbo makes pressure the more heat it will put into the intake charge, which increases the chance of running into detonation, which usually requires more fuel to compensate.

So what causes this?

Well, basically, it is a simple problem of the waste-gate opening being insufficient to divert enough exhaust around the turbine. Sometimes this is because to small a turbo is paired with to large a displacement engine, or it can simply be that the waste-gate is just to small.

So what can be done to correct this?

Well, there are a lot of possible solutions, but we’ll stick to the simple ones.

First, sometimes Boost Creep can be helped by changing your car’s tune. Consult your local tuner to get their feedback as to whether this could be an option for you.

Another option would be to have your waste-gate ported. This simply means that you would go in and increase the size of the waste-gate opening so that when the door opens, it can divert more exhaust around the turbine. This is something that is probably best left to professionals, but most likely any company that builds turbo’s would be able to port your waste-gate for you. If you are ordering a new turbo, it wouldn’t be a bad idea to consider having this done when they are building the turbo for you.

Another option would be to go with an external waste-gate. One reason that the size of the waste-gate opening is limited is because it needs to fit inside the exhaust housing. If you go with an external waste-gate, you would actually have a second exhaust channel that skips over the turbo all together. This allows you to put in a much larger waste-gate, so it is much better able to divert exhaust around the turbo. The down side is that it requires some custom fabrication or buying new exhaust components, welding up your internal waste-gate, etc., but this can be a very effective solution.

If you feel that you are having this problem, it would be a good idea to take your car to a professional mechanic/tuner and get a second opinion before taking any of these steps. They should be able to help you decide on what solution would be best for your application.

Jon Cooley

Can an Access Port return your ECU back to stock parameters with a Re-Flash?

When you are installing an Access Port on your car, one of the first things that it does is to "Marry" itself to your ECU.  This is what allows it to communicate with your car, and what will prevent it from communicating with someone else's car.

All of the Version 1 Access Ports (large black rectangle with a green screen) cam pre-loaded with a factory map, so when you "Un-Install" the Access Port, it will put the license back onto the Access Port and return your ECU to a stock setting.

The Version 2 Access Ports work a little differently.  They don't come pre-loaded with a factory map, instead when it is "Marrying" itself to your ECU, it will actually copy the factory map, and save it in its memory so if and when you re-set your ECU to stock, you will put back the exact map that you had before you re-flashed your ECU.  This is handy because if your ECU had any updates flashed on it from a dealer, you would still have those when you return your ECU to stock.

Something else important to note is that the only way to return your ECU to stock is to "Un-Marry" your Access Port from your car.  There are some stock maps out there that you can load onto your car, so it will be have as stock, but the difference is that your Access Port license is still on your ECU.  If you just load up a stock map and your ECU is re-flashed, it will most likely over-write your Access Port license making your Access Port unable to communicate with your car until a license is put back onto it (The Access Port would have to be sent to Cobb to do this). 

Also, if you just load up a stock map, your Access Port will not be able to communicate with another car because your license is still married to your ECU.

Jon Cooley

What should I do first, put on and exhaust, or get engine management?

If you have a modern turbo-charged car, the exhaust and engine management are the two biggest limiting factors when it comes to making more power.

In the case of an exhaust, the problem is restriction.  Generally speaking, Auto Manufacturers are usually pretty conservative when it comes to their exhausts.  They rarely put on an exhaust that is mandrel bent, and they will put on a muffler that keeps the noise to a minimum in the cabin, but is also pretty restrictive.  Throw in the conventional catalytic converters, and it is clear to see that there is a big opportunity for a performance increase with an aftermarket exhaust.

By the same token, Auto Manufacturers are usually very conservative when it comes to the tune of your car.  Keep in mind that when they set up the tune for a car, it needs to work on every car, in all conditions and climates, and in any driving situation that they can think of, which is to say that they will put on a very general tune.  This leaves a lot of room for a tuner to go in and adjust the fuel, boost, and timing parameters to get more power out of your car.

Even if you don’t do anything else, a simple re-flash of your ECU can yield a good increase in power, and can actually improve drivability.  When you pair this with a more free-flowing exhaust, you can get a dramatic increase in power.

But if you are going to do only one, which should you do?

One thing to keep in mind with an exhaust is that you really aren’t going to get the full benefit unless you put on a turbo-back exhaust (from the turbo all the way to the back of the car).  Putting on the exhaust will allow your car to operate more efficiently, but if don’t have a tune for the car, you are still using the stock running parameters which will greatly limit how much power you are able to gain. 

Also, on some cars, you can actually run into drivability issues if you just put on an exhaust with no engine management.  An example of this would be the 2006 – 2007 Subaru WRX.  This car has a 2.5 liter engine, but it still kept the same turbo that the 2.0 liter WRX had.  Because of this, the turbo spools up very quickly.  However, if you put on a free flowing exhaust, it will sometimes cause the turbo to spool up faster than the stock boost control parameters can control, and you can over-boost.

Up-grading your cars tune, on the other hand, is usually much simpler, and in the case of a Cobb Access Port, you will also have the tune for the time when you decide to put on your Turbo-Back Exhaust.  Most cars will also usually gain more power by up-grading the tune compared to just putting on an exhaust.  Not to mention that this is usually a cheaper option when compared to a Turbo-Back Exhaust.

For these reasons, our recommendation is to start with Engine Management, and then to add the exhaust when you are ready.

Jon Cooley

What affect will putting performance parts on my car have on my gas mileage?

This is a question that comes across just about everyone’s mind who is considering making their car faster, and the answer is….  Well, it depends.

Generally speaking, when you are putting on various bolt on parts to increase your engine’s power out-put, the main way that you are accomplishing this goal is by allowing the engine to operate more efficiently. 

A perfect example of this would be an intake, or an exhaust. 

What you are doing in this case is allowing the engine to pull in or push out, air with less resistance.  This means that more of the power generated by the engine goes to moving you forward.

Another example of this is an ECU Re-Flash.  Cars that come with forced induction from the factory have a tendency to run very rich.  This is because it increases the margin of safety for your motor, but often times, car manufacturers go a little too far.  One thing that a Re-Flash often does is to lean out the fuel a little bit to make more power.  By doing this, you are injecting a little less fuel all the time, and this also has the potential to increase fuel economy.

Because of this, putting these parts on will not only increase the amount of power that your engine produces, but it can also increase your fuel economy.  But that isn’t always the case.

People don’t typically put these parts on with the goal of increasing fuel economy, they usually want to go faster.  If you are going to drive aggressively, your fuel economy will be bad no matter what you do, and this is especially true in a car with forced induction.

If your car has a turbo, the more that you in positive boost, the more air that you are injecting into your motor, which also means that you are injecting more fuel.  So the more that you mash the “Go” pedal, the worse your mileage will be.

We experienced all of this in our Project Car, which is a 2003 Subaru WRX.  Before we did a thing to it, we were getting about 24-25 mpg.  After going up to a Cobb Stage 2 (engine management and a Turbo-Back Exhaust), we actually saw our mileage go up to about 27 mpg on average, and to almost 29 mpg on a long drive.  At the track however (Which is mostly wide open throttle), we have seen as bad as 12 mpg…

So the moral of the story is that you are actually in control of your own destiny when it comes to mileage, but if you take it easy, you might be able to have a fast car, and drive it too.

Jon Cooley

Do I need to get my car custom tuned to use the SPT Intake?

There are a number of intakes out there that do require a tune for them to work properly (and safely).  The reason that an intake would require a tune would be because the intake creates turbulent’s before the Mass Air-Flow (MAF) sensor, or due to its design, it causes the highest velocity air (usually in the center of the air flow) to miss the MAF sensor.  Also, some intakes do not retain the original internal diameter of the factory intake plumbing.  Any of these conditions can skew the MAF’s calculation of the amount of air coming in, and will require a recalibration.

Different intakes can create these conditions to various degrees, but in the case of an extreme discrepancy in the MAF signal, this can actually throw a Check Engine Light for the MAF sensor reading out of range.  If this happens, it is recommended that you remove the intake as soon as possible in order to take your car to have it tuned with the intake.

Fortunately, this does not apply to the SPT Intake because it was designed by Subaru to work correctly, and not need any custom calibration.

Probably the strongest evidence of this is the fact that the SPT intake is one of only two performance parts (the other being the SPT Cat-Back Exhaust) that you can install on your Subaru that will have no affect what so ever on your warranty.  It is doubtful that Subaru would offer this coverage if there was any chance of the intake causing an issue as described above.

Beyond that, we have done our own testing of the SPT intake, and you can read about our results in our Project Car Blog.  We did this test almost two years ago, and the SPT intake is still on our car, working flawlessly.

One other question that comes in regards to the Legacy GT SPT Intake specifically, is how it can work correctly with the MAF sensor placed so close to a bend?

If you look at the stock air box of the Legacy GT, it is entirely different than the Impreza air box, and if you look closely, you will notice that the placement of the MAF sensor is just to the side of the air box, which would require the air to make nearly a 90 degree bend.  This requires a different design for an intake, and is most likely the reason for the difference in the design. 

Keep in mind that the SPT Intake and SPT Cat-Back also will have no affect what so ever on your warranty, so Subaru clearly feels very confident in their design.

J. Cooley

How will putting performance parts on my car affect my warranty?

First, the most common rumor out there is that if you put any kind of performance part on your car, that your warranty is voided.

This is not true because it would mean that no warranty claim of any kind would be honored.

Putting a performance part, or any aftermarket part for that matter, just means that any failure related to or caused by that part would not be covered entirely, or at all, by your warranty.  However, a failure not related to that part will still be covered.

This is because of the Magnusson-Moss Act.  Basically, a warranty can not be denied just because you put aftermarket or performance parts on your car. 

Great, so I can put any part on my car that I want to, and they can’t deny my warranty, right?

Well, no.  The manufacturer can deny a warranty claim if they can prove that it was caused by the aftermarket part.  And the thing that you have to keep in mind is that they have all the engineers that designed the car working for them so they have a pretty good idea what putting on this part or that will do. 

So basically, unless you have a team of engineers on your side, you probably don’t want to rely on this.   What this means is that there is a chance that a failure will still be at least partially covered, or it might not.  What I can tell you from my experience is that the further you push the car beyond its designed limits, the less likely that a warranty claim will be honored. 

Unfortunately there aren’t any hard fast rules as to what you can do, and what you can’t, and usually each failure is looked at on a case by case basis.

Okay, so what does that mean to you?

Well, first and foremost, it means that you have to understand what you are doing with your car.  It is great if you can get your car to make 100 wheel horse power over stock, but if that additional power causes the transmission to fail, most likely it won’t be covered by warranty.  As long as you understand this and understand the possibilities of what might happen, then this shouldn’t really be a problem. 

This is where it can help to have a good shop that can answer your questions and give you an idea of what might fail if you push past a certain point, or to let you to know the safest way to reach your performance goal, etc.

Another thing to keep in mind, especially if you work on your own car, is that if you do have an issue, you need to bring your car into a dealership so that they can have a technician look at your car.  Most manufacturers will not honor warranty claims from an independent shop.  Also, if you do take your car to an independent shop, and they start working on your car, this can sometimes cause a claim to be voided.  If they remove and disassemble a part, the dealer’s technician is not able to evaluate the part on the car, which usually causes a claim not to be honored. 

In other words, if you think that your engine failed, and you take your car to an independent shop and the pull it, you may still have a chance of the failure being covered under warranty.  However, if the shop disassembles the motor, more than likely a claim would not be honored at that point.  The reason for this is that a technician needs to see the parts in their original context.

So does this mean that you can’t take your car to an independent shop to get it worked on?  Not at all.  However, if you think that you have an issue that would be covered under warranty, you need to take your car to a dealership first.

This is definitely not an easy issue, and if you still have questions after reading this, post them as a comment and I will do my best to answer them.

J. Cooley

How do I un-marry the Access Port? Do I have to take to a tuner?

If you are going to remove your Access Port, and return your ECU to stock, you do not have to take your car to a tuner.  You can accomplish this yourself with the Access Port.

To return your ECU to stock, you are going to have to re-write your base map, so you will need to put your car into test mode.  Please check Cobb’s instructions that came with your car first.

Basically, you will just need to connect the green “test” connectors under your dash (and the additional connector if you have a 2002 – 2005 WRX).  Once you have done this, your Check Engine Light should flash, and you should hear your electric fan under the hood turning on and off.

Once you are in “test” mode, connect your Access Port to your OBDII/CANBUS port and put your key in the on position.

Before you proceed, make sure that you do not have anything pulling current from your electrical system.  Make sure that your lights, fan, and stereo are off, that there isn’t anything plugged into you’re lighter socket.  If you have a turbo timer, it needs to be turned off, and if you have an aftermarket stereo amplifier, you need to make sure that you pull out the in-line fuse (which is usually next to the battery under the hood).

Once you are ready, use the Access Port to select the “Un-Marry” or “Return to Stock” option from the main menu.  You do not want to select a stock map from the “Change Map” menu because this would just put a stock map onto your ECU, while leaving your license on your ECU (so your Access Port will not work with another car).

Once you select this option, let the Access Port run its course, and once it is done, your ECU should be returned to stock.

J. Cooley

What is "Understeer"?

Let’s say that you are driving on an icy street.  You are going straight, but there is a corner coming up, so you turn your steering wheel.  You turn it as you would normally, but your car just barely begins to turn.

This is called Understeer.

Basically, the term Understeer means that you have to give your car more steering input than the corner should require to get it to go around.  The advantage of this is that your car is usually very stable in a straight line, but you have to work harder to get the car to turn.

For a more scientific definition, imagine that we draw a tangent line to the circle that the car is traveling around.  If you have to turn the front wheels so that they are at a more aggressive angle (pointed more to center) than the tangent line, your car tends toward Understeer.

Here’s another way to think of Understeer.  If you are driving around in a circle of constant radius, and you start accelerating, your front tires will be the first to lose traction, which will increase the radius of the circle.

It turns out that most automobile manufacturers build in some degree of Understeer into their cars because it is considered to be as safer tendency than Oversteer.  This is because if you turn your steering wheel, and your car doesn’t turn, it is a natural instinct to slow down.  Once you slow down to a speed where your tires have enough traction to go around the corner, your car will do what you are telling it to do and go around the corner. 

It should also be mentioned that there are a lot of variables in play when it comes to a car’s handing, and even if you have a car that tends to Understeer, it may not do so in all cornering situations.  One of the more significant variables is weight transfer from either acceleration or braking, and it will be discussed in another FAQ.

Jon Cooley

What is "Oversteer"?

Let’s say that you are driving on an icy street.  You are going straight, but there is a corner coming up, so you turn your steering wheel.  You turn it as you would normally, but all of a sudden, the rear of your car starts to rotate.

This is called Oversteer.

Basicaly, the term Oversteer means that you need to give your car less steering than the corner should require to get it to go around.  Tending toward Oversteer will make you car will feel pretty nimble cornering, but it also can make the car difficult to control.

For a more scientific definition, imagine that we draw a tangent line to the circle that the car is going traveling around.  If you don’t have to turn the wheels so that they are parallel to the tangent line, yet the car still travels around the circle, your car tends toward Oversteer.

Here’s another way to think of Oversteer.  If you are driving around in a circle of constant radius, and you start accelerating, your rear tires will be the first to lose traction.  This will cause the rear of your car to step out (which would require a counter-steering input), and will actually push the front of the car toward the center and reduce the radius of the circle.

There aren’t many cars on the market that will naturally tend to Oversteer.  This is because it is much easier to lose control of an Oversteering car if the driver doesn’t respond with the correct steering input.

It should also be mentioned that there are a lot of variables in play when it comes to a car’s handing, and even if you have a car that tends to Oversteer, it may not do so in all cornering situations.  One of the more significant variables is weight transfer from either acceleration or braking, and it will be discussed in another FAQ.

Jon Cooley

What are my Brake Up-Grade options for a 2002-2005 WRX?

Okay, if we are talking about brakes, there are a lot of options out there.

First thing you should think about are tires. It doesn't matter if you have enough brake to stop a train if you don't have enough traction to take advantage of it. If you want to make a dramatic improvement in your braking, a good place to start is a good sticky tire.

Beyond that, you definitely want Stainless Steel lines, and to up-grade to a DOT 4 brake fluid (this will give you better pedal feel, and more heat capacity to keep from boiling your fluid). You might also want to look at a Brake Master Cylinder Brace, this takes out most of the fire wall flex from the master cylinder, and also helps to improve pedal feel. The reason this is important is to make sure that as much of the force that you apply to the pedal makes it to your caliper, and also to let you know as soon as possible if your brake system is starting to fail because of heat build-up.

Then as far as upgrading your brakes, you have a couple options.

First would be to upgrade pads in your existing calipers. There are a lot of pad compounds out there, and they make a big difference. One reason that we carry Hawk pads is because of the wide range of compounds that they offer. Their street pad (the HPS or High Performance Street) is a very good pad for daily driving, and light track use. If you want to get more aggressive, the HP+ compound is great, but it will dust more, and wear out your rotors faster because of their higher coefficient of friction. If you are just driving around town, the HPS should be adequate, and if you still want more, get some HP+'s to swap out for the track.

The next step would be to up-grade your caliper. One option is to upgrade to the Subaru 4-Pot brakes that were first used on the GC STI, and now on the 06-07 WRX. They are a direct bolt-on, and use the WRX factory rotors (in front). These give you more clamping force (because you have 4 pistons instead of 2), and your brake pad is slightly larger, however, because you are using the same sized rotor, your mechanical advantage has not improved. The nice thing about this set-up is that you don't have to go with a larger wheel (they will fit under stock WRX wheels with a 5mm spacer), and they aren't much heavier than the stock parts. Keep in mind that here again, there are a lot of pad compounds to choose from.

We are currently using these calipers on the front of our Project Car which is a 2003 WRX with HP+ pads, with the stock calipers and HPS pads in the rear, and have had great results.

Beyond that, the next step would be to go with the STI Brembo Brakes. These give you an increase in clamping force, and a lighter caliper (made of aluminum), and a larger rotor, so an increase in your mechanical advantage to stop the car. The larger rotor also has a better ability to disapate heat, but you pay a pretty big weight penalty. Also, because you are increasing the rotor size, they will not fit under stock WRX wheels (though they may fit under 06-07 wheels with spacers), so you may have to go with a 17" wheel just to get these to fit. Also, at this level, you would ideally want to up-grade the rear calipers too, and Brembo's kit is the easiest way to do this because the Subaru Factory parts are not a direct bolt on.

If you decide to go with the Brembo's, again, don't forget that there a lot of pad compounds out there to choose from, and that should be more than adequate for anything you are doing.

J. Cooley

Will Re-Flashing my ECU and/or making more power put any additional stress on my engine or other components?

An engine has to burn fuel to make power.  If you want to make more power, you need to burn more fuel, or to burn the same amount of fuel more efficiently.  Either way, then end result is that there is more force pushing the piston down, which translates to more force that is transferred through the rest of the engine and drivetrain.

So the short answer is yes.

Something to keep in mind though is that this in only the case when you are asking the engine to make more power.  When you are at full throttle for instance.  If you are just driving around normally, chances are that your engine and drivetrain are not seeing any more stress than they used to.

Our Flatirons Tuning Project Car is a 2003 Subaru WRX with almost 90,000 miles on it now, and about 30,000 of those have been at Stage 2 or better.  We are still using the original stock engine, transmission, and clutch, and have had the car out on the track a number of times in addition to its daily duties. 

The long answer is still yes, but as long as you stay on top of regular maintenance, and make sure that you are using the best fluids (such as Redline oil or Eneos oil) to put in your car, you will most not see much additional wear on your car. 

Maintenance is the key here. 

If you are going to ask your car to make more power than it was designed to, you must keep up with scheduled maintenance, and if you go above and beyond, all the better.

J. Cooley

What is a Dyno Correction Factor?

A chassis dynamometer, or "Dyno", is tool that calculates your car’s horsepower and torque output. They can do this through a few different method’s, but the most common are by looking at the rate that your car accelerates a known mass (inertial dyno’s), or by measuring your car’s ability to produce an electric current(Eddy Current, or load based dyno’s).

Regardless of the method used to calculate your car’s power, as long as a dyno is calibrated correctly, the reading’s should be within a few percent of each other. However, because an internal combustion engine burn’s air and fuel to make power, there are a few more variable’s in play, the biggest one being the air that the car is consuming to make power.

If you were standing at sea level, and capped off an empty 1 liter bottle, you would have one liter of air. If you were standing in Denver, Colorado and did the same, you would have the same 1 liter of air. However the amount or mass (not weight) of air, and oxygen for that matter, would be different in each bottle.

The reason for this is that Denver is approximately 5,280 feet above sea level, and we have a lower atmospheric pressure (about 12.2 lbs./in^2 versus 14.7 lbs./in^2). If you would take that sealed bottle down to sea level, it would actually be crushed a little because of the pressure difference, and would suck air in when you opened the cap. Conversely, if you took the bottle from sea-level up to Denver, it would actually bulge out because there would be less pressure and it would let air out when you opened the cap.

To put it simply, there is a difference in air density between the two bottles. By air density, we mean that there is a difference in the mass of the air (how much stuff there is) between the two bottles. Atmospheric pressure is one main cause for a difference in air density, but two other’s are temperature and humidity.

Generally speaking:

A decrease in Atmospheric/Barometric Pressure will cause a decrease in Air Density.

A decrease in Temperature will cause an increase in Air Density.

An increase in Temperature will cause a decrease in Air Density.

An increase in Humidity will cause a decrease in Air Density.

A decrease in Humidity will cause an increase in Air Density.

So, if you put it on a dyno in Denver, and an identical dyno at sea level, it would not produce the same power because it is not getting the same amount of oxygen, and there for not producing the same amount of power. For that matter, if you put your car on the same identical dyno in Denver in winter when it was 10 degrees out, and in the summer when it was 100 degrees out, the reading’s would not be the same either.

This is where a correction factor comes in. The Society of Automotive Engineers (SAE) decided that it would be really handy to be able to compare dyno output’s from a variety of conditions in a meaningful way. So they came with a formula to compensate for differences in testing conditions, and give you a reading that you would get in ideal testing conditions (60 degrees Fahrenheit and minimal humidity at sea-level). This formula basically generates a number to multiply your actual number by to get your corrected reading, and is largely based on the barometric pressure, temperature and humidity at the time of the test.

To put it another way, if you are making changes to your car and testing it to see how effective they have been, you don’t have to wait for a day identical to the one where you performed your baseline test to see how much of an improvement you have made.

Now, with all that being said, there are a few other things to keep in mind.

First and foremost, when you get your car tested, ask what the correction factor is, and if you can get a chart with a corrected number, and an uncorrected number. This is for two reason’s. First, even though a corrected number is more useful to compare to later tests, your car made the power that it made, and it might be handy to know what that is. Second, you can compare the two, and see if your corrected chart makes sense. (ie. If you made 170 horsepower uncorrected, but 350 horsepower corrected, that is one heck of a correction factor).

Second, keep in mind that the correction factor will most likely (and should for that matter) be different every time you test your car. Even if you start testing in the middle of the day, and finish at the end of the day, there is a very good chance that a different correction factor will be applied (though in this case, it would likely be just slightly different).

Lastly, remember that the dyno is just a tool, and if you are making changes in the hopes of making more power, the power difference before and after is what is most important. If your car is making 50 whp more when it leaves after tuning than it did before, it doesn’t matter what the correction factor is, you have made a substantial improvement in power.

J. Cooley