Read First! - All the commonly asked questions about the 2nd Gen Neon. Some of your questions may be asked and then answered in here!
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Post by quicksilvr » Thu Jan 18, 2007 10:11 pm

Engine Performance


This section covers all aspects of engine modifications, from intake and exhaust, to internal upgrades and everything in between. This is a good place to learn about common upgrades, including bolt-on mods, that are part of most Neon build plans. Please contact the authors with any corrections, or with questions or concerns.

Engine Basics

An internal combustion engine is basically an air pump. Air is mixed with fuel and ignited by spark to create a controlled burn. The combustion process translates to mechanical power, which is what turns the crankshaft, axles, and eventually the wheels. Although it's operation is simple, any modification to it must be thoroughly engineered and precisely tuned....or you will break stuff.

Here is a link to show how a four-stroke engine works:

4-stroke engine

The more air molecules you can cram into the cylinder during the intake stroke, the more power you can make. So it only makes sense that you want the intake dynamics of your engine to be such that each cylinder is able to pull as much air in as possible per intake stroke. Cold air is denser than hot air, so cold air will always create more power than hot air because there are more oxygen molecules in any given volume. This is the basic principle behind upgrading intakes, throttle bodies, manifolds, or by adding forced induction to an engine. More air equals more power, and if you can force more air in, you have the potential to make more power.

Once you have the air portion taken care of, fuel is needed to mix with the oxygen for proper combustion. Power cannot be made with just air alone. Fuel is a key factor to making power. Reliability and performance of any engine depends greatly on fuel control and tuning.

Spark (ignition) is the third and final parameter needed to make power in an internal combustion engine. The ignition system must be controlled so as to initiate a spark at the proper time in a combustion event so as to burn the air/fuel mixture most efficiently. The ratio of air to fuel (AFR) plays a big role in what kind of spark is needed, and at what time. The AFR is also critical in keeping an engine from blowing up, which is why proper engine management and tuning is extremely important.

Last edited by quicksilvr on Wed May 18, 2011 7:29 pm, edited 23 times in total.

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Post by quicksilvr » Sun Jan 21, 2007 11:03 am

Intake System

Q: Which intake setup is best for my car?

A: The best intake setup depends on what you are looking for. Low price, high quality, top performance, or a combination of the three. Below are the top three most common options to upgrade the Neon intake system.

1) A drop-in filter, such as a K&N.
2) A brand name intake system such as an AEM, K&N, or Iceman.
3) A knock-off intake (ebay/homemade).

*The drop-in performance air filter replaces your stock paper filter, while retaining the stock intake box and plumbing. This is generally the cheapest and simplest way to upgrade your intake system. The power gains from a filter replacement are low, but the bang-for-buck performance of a drop-in filter upgrade can't be beat. Additionally, for people just wanting a more aggressive intake sound, removing the intake resonator from the fender well is a cheap and easy way to increase intake noise a bit without having to spend money on an expensive cold-air unit.

*A cold-air intake (CAI) is another option. By far the most popular intake upgrade in the Neon community. The CAI consists of replacement plumbing up to the throttle body, mounting brackets, and an air filter. Some (AEM) come with a replacement pipe for the bellows tube, between the throttle body and intake manifold. A CAI relocates the air filter outside the hot engine bay into the fender well. Since cooler air contains more oxygen per volume, engine performance can increase with a CAI. The quality units, such as those made by AEM, K&N, Iceman, and Injen, to name a few, usually fit very well, come with detailed instructions, and most are even CARB legal (for those with emissions regulations to satisfy). The higher quality intake systems are well engineered and provide consistent and reliable performance without compromise.

*Also available, though much less popular, are short-ram intakes (SRI), which are similar in every way to a CAI, except they do not relocate the filter outside the engine bay. These are really a step in the wrong direction, since they actually increase intake temperatures, causing a theoretical loss of power and efficiency. Their only positive feature is a shorter total intake length, which may assist in throttle response and top end acceleration.

Generic intakes (both SRI and CAI) are available online. Quality and performance are unknown, therefore buying a 'knock-off' or 'eBay' intake (or any other part) comes with a few risks. You can expect fitment to be poor, and oftentimes these cheap intakes do not come with mounting brackets nor a quality air filter. They are inexpensive for a reason.

Q: Does an SRT-4 intake fit my car?

A: No it does not. An SRT-4 intake must run from the back of the engine where the turbo is, all the way to the fender well. They are much longer, and have completely different angles bent in them than our intakes.


Q: Does a 1st generation Neon, or SRT-4 throttle body fit on my car?

A: No, they do not. Both are designed to be mounted directly to the manifold, which our cars do not have a provision for. I would not recommend trying to use one unless you have a custom intake manifold or fabrication skills.


Q: What's the difference between a Magnum cold air intake and a standard cold air intake?

A: Because the aluminum Magnum intake manifold is designed differently than the standard plastic manifold, it requires a cold air intake with different angles bent into the pipes in order to fit. The biggest difference is in the short pipe that runs between the throttle body and the manifold. On Magnum engines, that pipe must be bent, while on the standard 2.0L, that pipe is straight.


Q: Is a 60mm throttle body a good performance modification?

A: Yes, they offer a nice increase in throttle response, sensitivity, and intake sound. However, horsepower and torque gains have been dyno proven to be minimal on naturally aspirated engines, usually only 1-2whp. On forced induction setups, they are fantastic....because you eliminate a bottleneck in the pressurized intake flow.

NOTE: As of 2008, Modern Performance has changed the listing on the 60mm throttle bodies to exclude the 2005 models. Apparently there were issues with that model year throwing a CEL when using their TB.


Q: What is the difference between the Modern Performance 60mm throttle body, and the LFS or "Lorenzo" throttle body?

A: Both TB's are high quality units. The main difference is that the LFS TB requires a modification to the bracket that bolts to it and holds the throttle cable. You have to trim a small tab of metal off the bracket so that it will clear the cam on the TB. The Modern Performance TB does not require this, because the cam on the TB is spaced out enough to clear the tab on it's own.


Q: Is there a difference between the TB's on a stock automatic transmission Neon and a stock manual transmission Neon?

A: No, all second generation neons recieved a 52mm throttle body.


Q: What does a catch can do?

A: A catch can fundamentally helps the pcv valve do a better job. The pcv valve is suppose to vent air from the valve cover, but keep all the oil inside. In reality, the pcv design on our 2.0L SOHC valvecovers is not that great, and a considerable amount of oil goes through the pcv valve into the intake. On cars that are turbocharged, this is an even bigger deal, because there is much greater pressure being dealt with.

A catch can installs inline between the pcv valve and the intake. A good one has a seperator to seperate the oil vapor from the air and collect it. Cheap ebay ones just have a longer input tube, so that "hopefully" the oil drops off it and doesn't just go right back out of the can through the output tube.


Special Note:

Let it be known that some models, primarily 2003-2005 models with the NGC computer, have been known to throw a check-engine light (CEL) when an aftermarket intake or throttle body is installed. This occurence is rare with intakes but fairly common with throttle body upgrades. The reason for the code is that the computer sees a difference between the TPS readings and the MAP readings that is viewed as abnormal. The larger TB requires less throttle position movement to allow a given amount of air to pass than a stock TB, causing the difference.


Intake Manifold

Q: How is the Magnum (H.O.) intake manifold different from a standard intake manifold?

A: The Magnum intake manifold differs in these ways:

-It is made out of aluminum instead of plastic.
-It has a larger plenum.
-It has 4 primary runners and 4 secondary runners for a total of 8, instead of just 4 on the standard intake. The 8 runners merge back into 4 about halfway up the manifold, because obviously only 4 runners can feed the intake ports.
-It has butterfly valves that control the airflow through the 4 secondary runners.
-It has an actuator motor attached to it that controls the butterfly valves.


Q: How does the Magnum intake manifold work, and why does it make more power?

A: The dual plane design (4 primaries, 4 secondaries) of the Magnum manifold works like this. There is a rod extending through the casting of the bottom half of the intake called the plenum. It goes through the entire row of secondary runners. In each runner, there is a butterfly valve screwed to the actuator rod.


As you can see, the secondary runners are round, and the primaries are rectangular. The primary runners are always open, there is no way for them to ever be closed.

On R/T and ACR model Neons with the Magnum engine, there is an ouput from the ECU that goes to the actuator motor on the intake manifold. When powered, that actuator motor turns the rod over, opening the valves in the manifold. Note that the butterfly valves are either open or shut....never in between. The ECU controls when to power the actuator, and from what I understand, on stock Magnum cars those parameters are:

-Under 3200 rpm (doesn't matter what the throttle position is) the secondaries are open.
-From 3200 to 5000 rpm, (again, not withstanding throttle position) the secondaries are closed.
-From 5000rpm to redline, the secondaries open at WOT (wide open throttle)

It is possible to hook up a Magnum intake manifold to a non-magnum engine, and make the secondaries work. Please refer to http://forum.2gn.org/viewtopic.php?t=3048 to read all about how to do that.

The Magnum intake manifold will make more power because it allows more airflow in the upper RPM range that is so crucial to peak HP. Without the secondary runners open to provide the needed air at high rpm, the HP curve takes a nose dive. The reason the secondary runners are not open ALL the time is to help keep the available torque high in the middle rpm ranges that we drive in every day. At part throttle, the engine doesn't need the extra airflow of the secondary runners, because it's not making peak horsepower anyway. Keeping the secondaries closed in the mid rpm's increases torque, because there is then not too much volume in the intake for what the engine needs.

NOTE:In turbocharged applications, when using a magnum manifold, it would be beneficial to remove the butterflies completely, and let both sets of runners be open all the time. The is because with a turbo, the intake manifold has positive pressure in it, not negative...and having both sets of runners open allows the most absolute flow at all times...which is what you want for a turbocharged application.


Q: What aftermarket intake manifolds are available for my car?

A: There are several options for intake manifolds for the 2.0. The following is a list of non-stock manifolds available, and some pictures of each.

Home-made manifold:

This a homemade manifold, made from the flange and runners of a stock plastic manifold, and a piece of pvc pipe as the plenum. The runners are usually sealed to the plenum with JB Weld, or some other high stregth epoxy. By design these manifolds will increase top end power and response, but usually lose torque in the lower rpm range. They also should not be used for turbo applications, especially high boost....as they very well could blow apart under high positive manifold pressure. If you have a big cam and you want a cheap manifold that will help it scream at high rpm, this is a viable option. It's usually ugly too......for what it's worth. :lol:

A blue one!

Sheet metal manifold

The user all_motor_mike custom makes intake manifolds. R/T Ernie is another name that you'll see attached to some custom intake manifolds. These manifolds can be made to your specification...long runners, short runners, big plenum, little plenum, etc. If you're not sure if you need one of these, you probably don't. These intake's are usually best used on highly modified cars. You'll know when you want one. 8) Here are a few pictures.

all_motor_mike long runner intake...

all_motor_mike short runner intake...

R/T Ernie intake...


This is a cast aluminum two piece manifold with mid length runners. This is a great intake for forced induction application, or really high rpm power in an N/A car.

Indy intake


This high quality custom intake is made with a unique design. It has even shorter runners than the Indy. From what I know from people that have used it, it's a great intake, but designed for optimal power in the 5000K and above rpm range. Only get this intake if you have serious mods and a higher rev limit. Kevin_GP uses one with his SRT-4 turbo setup on his '02 ACR.

Lonewolf intake on an R/T

Lonewolf on a turbocharged setup


Q: Can I use a 1st generation Neon intake manifold on my 2000+ car?

A: Yes and no. An intake manifold from any SOHC 1st gen will fit, because the 2nd gen SOHC head is the same as the 1st gen. A 1st gen DOHC intake manifold will NOT bolt up though. People have made them work, but they have different bolt points, and you have to cut the water neck off of them.

That said, there are no real performace gains from using a stock 1st gen SOHC intake manifold. But most of them are aluminum, so if you wanted to be able to do port work, it could be handy.

If you do try to use a modified DOHC intake manifold, the intake ports on your SOHC head will need to be port matched to the manifold, as the DOHC manifold is bigger.
Last edited by quicksilvr on Sat Dec 20, 2008 5:57 pm, edited 10 times in total.

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Post by quicksilvr » Sun Feb 04, 2007 11:42 am

Head, Camshaft, & Valvetrain

Q: What's the difference between the Magnum head and the standard head?

A: Both heads are cast from the same stock and are fully interchangeable. The biggest performance difference is in the exhaust port size, and the exhaust port bowl shape. The magnum head has bigger ports, and the bowl is shaped much differently, and much freer flowing. The magnum head also comes with stiffer valve springs, to support the more aggressive magnum cam. While possible, it is not recommended to mix and match Mag and non-Mag head internals; it is best just to swap the entire head. Keep in mind, there are spark and fuel differences between mag and non-mag PCMs, therefore simply swapping just a mag head onto a non-mag block will not yield the same performance.


Q: Can I put a 2.0 DOHC head in my 2gn car?

A: Yes, it will bolt up. But there are quite a few modifications necessary, so if you plan on doing it, it would be a good idea to have an entire DOHC donor motor to pull off of. You'll need: the manifolds, throttle body, sensors, timing belt drive components, cam gears and wiring harness to get it running. You'll also need a DOHC computer to get the right fuel and spark. SOHC's and DOHC's will run with the wrong computer, just not that well. The fuel and spark tables are totally different because the engines have different airflow characteristics.


Q: Can I put a 2.4 DOHC head on my 2.0 block?

A: Yes, it will bolt on just fine, but there are several other areas that need addressed if doing the swap.


Q: What does Porting & Polishing (P&P) a head do, and what kind of power increase does it add?

A: Porting and polishing your cylinder head has one main purpose: to increase the airflow into, through, and out of the engine. "Porting" refers to the process by which the intake and exhaust port openings are made larger and sometimes reshaped. "Polishing" refers to the process by which all the surfaces that affect the airflow are smoothed and polished.

The gains you will see depend on two things, the extent of the P&P work, and the other modifications you have done to the engine. Just for reference...your results may vary....a good P&P job from an experienced technician should gain you around 15 hp. If could be as little as 5...or as much as 35...it all depends on what else you've done to increase your flow.


Q: What does a valve job do?

A: The description below is copied from a general Yahoo auto page. It is not Neon specific, but it good information.
Yahoo Auto Page wrote:A valve job is removing the cylinder head(s) from the engine so the valves, guides and seats can be refurbished to restore compression and oil control. A valve job may be necessary by the time an engine has 80,000 or more miles on it, or to fix a "burned valve," compression or oil burning problem.

Before we describe all the steps that a typical valve job involves, we should warn you that some shops don’t necessary do all the steps. In other words, you get what you pay for. A cheap valve job might skip a lot of things that saves you a few dollars in the short run, but may end up costing you a lot more in the long run. So look for a shop or service facility that does quality work.

A valve job typically begins by disassembling, cleaning and inspecting the cylinder head. Cast iron heads are "Magnafluxed" to check for hairline cracks. This involves applying a strong magnetic field to the head and sprinkling iron powder on it. Cracks disrupt the magnetic field and attract the iron powder, making invisible cracks easy to see.

Cracks are bad news because they can leak coolant into the combustion chamber damaging the cylinders and/or causing the engine to lose coolant and overheat. If cracks are found in any critical areas of the head, the head must either be repaired or replaced. Cracks in cast iron heads are most often repaired by "pinning" (installing a series of overlapping threaded pins). Cracks in aluminum heads are very common and can often be repaired by welding.

If a head has been repaired (pinned or welded), most shops will usually pressure test the head afterward to make sure there are no leaks. Some may also apply a sealer compound to the inside of the water jackets as added insurance against future leaks.

Once the head passes this point, it is also checked for flatness. The surface of the head must be flat to seal the head gasket against the block. Excessive warpage, roughness or any damage can cause the head gasket to fail. If the head exceeds the maximum allowable out-of-flatness specs, it must be resurfaced or replaced. Usually there’s enough metal in the head to allow for a certain amount of resurfacing. But on many import aluminum cylinder heads, the amount of resurfacing that’s possible is minimal.

Overhead cam aluminum cylinder heads are often found to be warped (usually the result of overheating). If the condition cannot be corrected by resurfacing, the head can often be straightened by heating it in a special oven and then bending it until it is straight.

Next come the valves, guides and seats. The guides are checked for wear. They’re almost always worn, so they either need to be replaced, relined or knurled (a process whereby grooves are cut into the inside diameter of the guides to decrease the bore size). Few shops knurl guides anymore. Most install new guides, guide liners or bore out the old guides to accept new valves with over-sized stems. Aluminum heads have cast iron or bronze guides that can be replaced but most cast iron heads do not.

If the valves are to be reused, they will be inspected, checked for straightness then refaced. Many shops automatically replace all the exhaust valves to reduce the risk of failure (exhaust valves run much hotter than intakes and are much more likely to fail).

The seats in the head are either cut or ground to restore the sealing surface. If a seat is cracked or too badly worn to be refaced, the seat must be replaced. If that isn’t possible (as is the case on many late model cast iron heads because the casting is too thin), then the entire head must be replaced. All aluminum heads have hardened steel seats that can be replaced.

The valve springs are all inspected and tested to make sure they are still capable of maintaining proper pressure. The spring retainers, keepers and other hardware is likewise inspected. Any worn or damaged components are replaced. New valve guide seals are always used.

The valves are then installed in the head and shimmed to restore proper valve height. This is necessary because machining the valves and seat alters their dimensions. Valve height is important because it affects valvetrain geometry and guide wear. If it is an overhead cam engine, the cam is also installed and the valve lash adjusted prior to returning the head to the customer.


Q: What are the cam options for my SOHC, and which is best?

A: There are two aftermarket manufactors that currently make and sell cams for our SOHC 2.0 engines. One is Crane Cams, and one is Comp Cams.

Crane Cams:

They make three cams that are widely available. Crane's options are most widely known by number...#10, #12, and #14. Crane also makes some even bigger cams that are considered custom grinds, often referred to as the Crane 007 and the Crane 005. These are BIG camshafts that MUST have supporting modifications and higher compression to run effectively. Crane can also custom grind pretty much any cam you could dream up.

The #10 cam is the mildest cam available. In most people's opinion from experience, it's not even worth putting in; very minimal gains at best. This cam, while a little larger than a stock base cam, has less lift than the "Magnum" cam that comes stock in all Magnum engines, although the duration is still greater than the Magnum cam.

The #12 cam is a nice cam for a daily driver, or milder forced induction builds. The cam features a shorter exhaust duration than intake duration to help spool turbo's faster and reduce lag time. It is recognized to produce noticeable HP and TQ throughout the stock powerband in all applications.

The #14 cam is considered the most radical cam that is widely available. It has the same intake lift as the #12, but .75mm more exhaust lift. It also has considerably more duration on both intake and exhaust sides than the #12 cam. These characteristics lend this cam to making power at very high rpm...all the way up to 7500 rpm. Which is 1000 rpm higher than the stock rev limiter. Because this is the case, this cam can only be used to it's potential if the stock rev limit has been removed, via either a modified ECU, or a standalone engine management system (EMS).

The #007 cam has the same lift as the 14, but more duration. With supporting mods, this profile can get you into the 180hp range.

The #005 is the monster nasty cam that SGT BRAD uses in his DCR (Darrell Cox Racing) built engine.

NOTE: All Crane cams are designed to use aftermarket valve springs that are stiffer and stronger than stock.

Comp Cams:

They make only two cams for our cars, known as the 200 and 400. The 200 is the smaller cam, and the 400 is the larger. Comp Cams designed these cams to be used with the stock valve springs. They did this by decreasing the ramp angles slightly, so a stiffer spring is not necessary. Since Comp Cams and ZEX market stuff together, these cams are available at ZEX or on eBay.

Now, instead of trying to compare all these cams to each other with terms like bigger and smaller, I'm going to list their specs below, so you can see for yourself how they differ.

Crane #10:
Duration (@ .050"): Intake - 196 degrees______Exhaust - 200 degrees
Lift:_____________Intake - .335"____________Exhaust - .315"

Crane #12:
Duration (@ .050"): Intake - 204 degrees______Exhaust - 200 degrees
Lift:_____________Intake - .355"____________Exhaust - .315"

Crane #14:
Duration (@ .050"): Intake - 216 degrees______Exhaust - 212 degrees
Lift:_____________Intake - .355"____________Exhaust - .345"

Comp 200:
Duration (@ .050"): Intake - 200 degrees______Exhaust - 206 degrees
Lift:_____________Intake - .356"____________Exhaust - .336"

Comp 400:
Duration (@ .050"): Intake - 205 degrees______Exhaust - 206 degrees
Lift:_____________Intake - .384"____________Exhaust - .336"

Magnum '01 Cam: (NOTE: different measurement for duration)
Duration (@ .006"): Intake - 212 degrees______Exhaust - 228.5 degrees
Lift:_____________Intake - .344"____________Exhaust - .315"

You need to note that the only specs available for the Magnum cam are the factory specs. The factory uses .006 of lift for their duration measurement, I'm guessing because the SAE standard for hydraulic seating points is .004, with .003 of that being deflection. The Mopar engineers must be expecting .005 of deflection, therefore using .006 as typical "seat-to-seat" measure. However, there is no way to simply convert the specs, so unless someone measures a factory cam @ .050, we'll never know exactly.

Keep this above information in mind whenever you are dealing with ANY camshaft specs of any kind. Specs become meaningless when they are not measured the same.


Q: What do all those cam specs mean?

A: I thought you might ask. :) Here's "How Cams Work 101"...

Your camshaft is turned by the timing belt, which is being turned by the crankshaft. As the camshaft turns over, the lobes on the cam press against the rollers on the rocker arms. The rocker arms press against the valve's themselves. So as the cam turns, the rocker arms go up and down, forcing the valves up and down.

So the cam is turning, and the valves are going up and down. YES! First step down. 8) There are two intake valves in each combustion chamber, and two exhaust valves in each chamber. That equals four valves total per cylinder, hence a "16 valve" engine. How 'bout a picture?


Now, the valves are going up and down (or more accurately, open and closed). The only thing controlling how far they go open, or how long they stay open is the size and shape of the lobes on your cam. If one of the lobes on the cam is taller, it's going to push that rocker arm up farther, which pushes the valve itself farther open. This is valve lift. And if one of the lobes on the cam is shaped differently, it can hold the valve open longer. This is valve duration. Go check out How Stuff Works for a super nifty animation of how it all plays out, and for more detailed info on stuff like valve overlap, etc.

Concerning cam specs: Basically, if the number for duration is bigger, those valves are staying open longer around the rotation. If the number for lift is bigger, the valve is pushed open farther at it's maximum open point.

So for example, if you are comparing the Comp 200 cam to the Crane 12, you will see that the Comp 200 has less intake duration, but more exhaust duration than the Crane 12. This is mostly because the Crane 12 is designed specifically with a short exhaust duration for turbo application. But, you will also see that the Comp 200 has more lift on both intake and exhaust sides than the Crane 12. All this adds up to two cams that will perform differently at different RPM's, and respond differently to other engine modifications.


Q: Can I use a cam from a DOHC engine in my SOHC?

A: Absolutely NOT. A DOHC engine has one cam that only operates the intake valves, and one cam that only operates the exhaust valves. Therefore each cam from a DOHC has fewer lobes, and they are spaced completely differently. A SOHC engine cam has to operate both intake and exhaust valves.


Q: What valve springs should I use?

A: There are 3 choices for valvesprings: stock, (stock) Magnum, Crane, and Mopar Performance. Oops, that's 4. Well, the Mopar Performance springs are really expensive, and pretty much nobody uses them because of that.


The run-of-the mill springs that are on every standard 2.0 will work just fine with the Comp 200, and even supposedly the Comp 400 cam. If you want to try, that's up to you...i'd use at least Magnum valve springs with the Comp 400 because of the lift. Both the Comp cams were designed with milder ramp angles in order to work with the stock springs. But the Comp 400 is designed for the Magnum engines....so you could interpret that to mean it works with (stock) Magnum springs.


These springs come stock on R/T and ACR models with the Magnum engine. They are a high quality spring...I've never heard anything but good about them, and I haven't heard of anyone that's broken one. These springs will work great with the Comp cams, and they will also work just fine with the Crane cams...even the #14. Some people will argue that you shouldn't use them with the Crane #14, but lots of people do...and they've never had any problems. If you do use them and have problems...good for you, you were a pioneer. Make sure you tell me when it happens. :)


These springs are, from my research, really only necessary for use with the bigger DOHC cams. Which you won't be using. :lol: If you want extra insurance against valve float at high rpm or breakage from extended use at high rpm, these would be the springs to get. That said, even the Crane #14 doesn't have enough lift to make using the Crane springs necessary. They're just more of insurance than required fare. They are also abundantly available brand new from many retailers, which is always handy.


Q: How do I change my cam?

A: There is a fairly comprehensive How-To located here: Cam Install


Q: What does a cam gear do? Do I need one?

A: A cam gear allows you to adjust the cam/valve timing. This is not to be confused with spark timing. In essence, by advancing or retarding the timing of the cam, you can theoretically move the powerband of the engine. Changing the valve timing can shift the powerband to a different RPM range. Power can be set to come in early, but fall off at higher revs, or come in late, and pull to redline. The best option completely depends on what you want out of the engine. For racing, a top-end powerband is ideal, because that is where the engine will spend most of it's time. For the street, somewhere in the middle is usually ideal.

There are some very important things to understand when dealing with cam/valve timing. First, you always need to centerline the cam. This means that it's possible that your cam gear would be advanced or retarded, just to get the cam centerlined. All of your actual advance or retard would then be dialed in from that 'starting' point. Centerlining a cam means that the cam is actually operating at it's advertised specs. If it's supposed to open at 10 degrees before top dead center (BTDC), but it's actually opening at 8 degree BTDC, then you have to retard it 2 degrees to centerline it. Here's a link for info on centerlining, although some of it is missing Cam Timing

Usually in order to gain peak HP or TQ with most cams on our 2.0 engines, you must retard the timing 2-3 degrees, moving the power band (and the RPM where peak HP occurs) higher up the RPM range. However, unless you spend all your time above 5000 rpm blasting down the track, your car will actually feel weaker on the road during street driving because the optimized part of the power band is too high.


Q: How do I adjust the cam gear?

A: In order to adjust the cam gear, the outer timing cover must be removed or modified. If you want to be able to adjust the cam gear while dyno tuning, there is only one option, because you cannot remove the entire timing cover without serious labor and disassembly. The outer timing cover must therefore be modified to look like this...(a CD makes a good template for cutting the the hole)


Then, when you are on the dyno, you simply have to remove the upper motor mount, and loosen one bolt at a time on the gear, move the gear, and re-tighten one bolt at a time. Here's a picture...

Last edited by quicksilvr on Wed May 18, 2011 7:24 pm, edited 6 times in total.

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Post by quicksilvr » Mon Jan 28, 2008 1:32 pm

Exhaust system

There are several ways to modify and upgrade the exhaust system on your Neon. There are a variety of headers, cat-backs, axle-backs, catalysts, and muffler options on the market. But which one is right for you?

When shopping for an exhaust system, it is best to ask yourself what it is you plan to get out of the upgrade. This can be said of many upgrades, especially popular bolt-on's like intake and exhaust. Do you want a change in sound? Performance? Appearance? All of the above? How much are you willing to spend? Do you need to keep the vehicle street legal? These are the questions you need to answer before making the best decision.

Q: What are my basic exhaust options?

A: The most popular basic exhaust upgrades are listed below.


PROS: Inexpensive, easy to find.

CONS: Very loud; requires additional muffler to keep noise levels reasonable. See "AFTERMARKET MUFFLER" section for help choosing a supplemental muffler.


PROS: Fairly inexpensive, easy to find.

CONS: Very loud without an additional muffler.

NOTE: Since the diameter of this exhaust is the same as stock, using the midpipe won't yield any performance gains.


PROS: Usually bolt-on, no additional work required. Some of these systems are good for a small performance gain over the less expensive options listed above.

CONS: Expensive.


PROS: Cheaper than a catback, wide variety of styles.

CONS: Requires welding for proper fitment. Many people use glasspack mufflers to quiet down unmuffled exhausts (SRT). These are compact, available in a range of sizes, and inexpensive.

TIP: As a rule of thumb, the longer the glasspack muffler, the better noise reduction.


Q: What are my complete exhaust options for total performance?

A: For enthusiasts looking for more performance, there are a few additional ways to further upgrade the exhaust system. The best way to start with your additional upgrade is to install an aftermarket header on your Neon. A header is far superior to the cast-manifold found on the regular 2.0L engine. The R/T and ACR models come with a factory designed header, but they too can be upgraded for maximum performance. You can also use an aftermarket high-flow catalyst to further improve flow. The most popular header options are listed below.


PROS: A common upgrade for the budget minded enthusiast.

CONS: These are becoming more difficult to find, thus their prices are starting rise.


PROS: Available from companies such as Borla, this is typically a small step above the Magnum header both in design and quality. Most bolt up to the factory catalyst and cylinder head without modification. Look for units that have a bung for the primary 02 sensor (Borla).

CONS: Low-to-moderate power and flow gains.


PROS: Capable of slightly higher performance gains than their short-tube bretheren, maximized when used with a tuned engine that requires additional exhaust flow.

CONS: May require the catalyst to be relocated and reflanged for proper fitment. This can cause legality issues as well as a check engine light if the 02 sensors are not properly integrated. Slightly expensive.


PROS: Top of the line performance.

CONS: May require the catalyst to be relocated and reflanged for proper fitment. This can cause legality issues as well as a check engine light if the 02 sensors are not properly integrated. Most expensive header option. BRANDS AVAILABLE: Kirk, TTI, MPx, AF/X, Blackdog, Fast Fabrications. *Note that very few of these headers are currently produced and sold retail, most must be found second-hand in used condition*
Last edited by quicksilvr on Wed May 18, 2011 7:34 pm, edited 6 times in total.

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Post by quicksilvr » Sat Sep 20, 2008 7:48 pm

Underdrive & Overdrive Pulleys

Q: What is an underdrive pulley? I've heard they offer good performance gain...

A: An underdrive pulley is a lighter, smaller pulley that is installed on the end of the crankshaft. It replaces the stock harmonic dampener/pulley. Underdrive pulleys give performance gains by being lighter (less rotational mass) and by being smaller (accessories like A/C pump and alternator are turned slower). UDP's (as they are often called) are a good basic bolt-on part that will normally give you a small gain in performance.

*Most 2002 model Neons will throw a CEL at you if you use a UDP. It usually is a misfire code, and it only shows it's ugly head at 5000 rpm and higher. It will clear itself most of the time. It's up to you whether or not you want to put up with the problem*

Brands Available: MPx, Unorthodox, AF/X (not sure if still making them) are the 3 main brands. There are also some knock-off eBay brands I believe. You get what you pay for, and a crank pulley is something you don't want to screw up. Some of the cheap ones will not fit tight, or come loose easily.

You will need a new belt that is shorter than the stock belt. Dayco part# 5040295 or Gates part# KO40295.


Q: What is an overdrive pulley? And why would I want one?

A: An overdrive pulley is installed on the alternator. It is smaller and lighter than the factory pulley. An ODP is used to compensate for already having a UDP installed on the crankshaft. Since the alternator output is reduced when using a UDP, the ODP is designed to combat this issue. If you notice excessive dimming of headlights or lack of power to run audio accesories, an ODP on the alternator will bring it's relative RPM ratio with the crankshaft back in line with stock parameters.

*If you use a crank UDP and an alternator ODP, you will need an even shorter alternator belt, although not much, since the alternator is adjustable to compensate for different belt lengths.

Brands Available: LFS Racing is now offering ODP's. They look like a quality piece. Adam K. made ODP's a while back, and sometimes you can find one of his used. It is basically the same as the LFS unit.

Last edited by quicksilvr on Wed May 18, 2011 7:29 pm, edited 2 times in total.

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Location: Bay Area, CA

Post by OB » Mon Sep 07, 2009 10:58 pm

Ignition System

All PL models, including the SRT-4, use a DIS ignition system. There is no distributor. Also called a wasted-spark ignition, the DIS setup fires on two cylinders at a time, instead of just the one that is at the top of its compression stroke. The coilpack is one unit, but essentially houses two coils. The primary windings are energized by the ignition driver (transistor) when given a signal by the PCM. Briefly after energizing, the PCM cuts power to the primary side, which causes the energy to be transferred to the secondary side. This causes an extremely high voltage pulse of energy that is then sent from the coil to the spark plugs, via the ignition wires.

Spark Plugs, Coil, and Ignition Wires

The OEM spark plugs used in the 2.0L are nickel alloy, commonly referred to as "copper" plugs. They are manufactured by Champion. There are several alternative plugs that will work great for the SOHC engine, with NGK's V-Power and Iridium plugs being the most popular. However, the factory Champions are more than sufficient for stock or even moderately modified engines. The OE ignition wires and coil are also of decent quality. Both have aftermarket alternatives from manufacturers such as MSD and Magnacore. A high performance ignition system is also available from MSD for the hardcore build.


Q: At what point does the ignition system need upgrading?

A: The stock ignition system components are more than capable of running a stock engine with bolt-on modifications. Even with forced induction and a mildly built engine, the stock setup is sufficient. Only with very aggressive builds and huge power levels is an aftermarket setup needed. The key factor in modifying and tuning these motors is engine management.


Ignition Component Testing

Below are the OEM ratings for ignition coil and spark plug wire resistance values.

-Weastec (Steel towers) - 0.45-0.65 Ohms Primary / 11,500-13,500 Secondary

-Diamond (Brass towers) - 0.53-0.65 Ohms Primary / 10,900-14,700 Secondary

Spark plug wires (ohms):


Note, the SRT wires have identical ratings, EXCEPT #4, which is 2686-8062

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