After years of neglect, the Neon is finally gaining some aftermarket attention from the major suppliers, and several Neon-specific manufacturers have appeared. A large variety of upgrades is available, ranging from simple bolt-ons to complicated surgery. Outlined below are suggested programs for tapping some of the 2.0's potential, in both SOHC and DOHC flavors. For now, these are limited to work that most Neon owners can: A) afford, and B) hope to do themselves. Additional answers below will describe some of the higher-effort (and higher-performance) modifications for the hard core types.
This section specifically avoids stating horsepower gain figures or time figures. Insufficient dyno testing has been done (or documented, at least) by independent parties. Statements like "bolt on this product and add 10 hp" are usually based on retailer/manufacturer hype, and all performance modifications must be considered in the context of the complete engine system, rather than simply adding a number for each upgrade performed.
(Thanks to Jason Artley, Dale Seeley, Greg Smith, and Jim Waleke - alphabetical order - for their review and commentary on this section.)
2.9.1 Q: Will aftermarket parts void my warranty? What about Mopar Performance parts?
A: This question does not have a hard-and-fast answer. Dealers will be instantly suspicious if you show up driving a heavily modified car and complaining about defects. Just how suspicious depends upon the dealer.2.9.2 Q: What is a basic plan for increasing SOHC performance?
Adding aftermarket parts does not automatically void your entire warranty. For instance, having an Iceman will not affect coverage of suspension, transmission, or electrical problems. However, if you spin a bearing and the analysis shows dirt in the oil, you are probably out of luck. If there is an issue, technically the burden is on the dealer to prove that the particular part caused the problem. Realistically, though, you are starting out with one strike against you.
There is a continuing myth that Mopar Performance parts will not affect warranty coverage. This is not true. As far as Chrysler is concerned, Mopar Performance is just like any other aftermarket supplier. The 'Mother Parts' catalog carries a disclaimer stating the following:"Competition parts are sold 'as is' without any warranty whatsoever... Chrysler Corporation vehicle and parts warranties are voided if the vehicle or part is used for competition or if they fail as a result of modification."Yes, installing a Mopar Performance piece qualifies as a modification to the original car. In fact, until the 2000 catalog came out, MP parts themselves were not even warranted against defects. While they still void the car's warranty, most defective parts are now covered.
A: The SOHC has the reputation of being the DOHC's 'little brother'. However, due to some under-reporting of the SOHC's power figures, and some over-reporting of the DOHC's, the difference is not as huge as it might seem. Contrary to some opinions, the first step in upgrading a SOHC is not "sell it and buy a DOHC". Below is a 10-step program for getting more performance out of your single overhead cam engine:2.9.3 Q: What is a basic plan for increasing DOHC performance?1) Remove the black weatherstripping from the back edge of the hood. This adds 1hp and is the most cost-effective mod, since it's free. Approximately 10-15 degrees cooler underhood temperature means more power, too. One consideration: with the seal removed, an underhood leak can spray coolant steam over the windshield, causing visibility problems.There are plenty of other items which can be modified on the SOHC to improve performance; however, most of them fall into the realm of "serious folks only". As mentioned above, this list is geared toward the do-it-yourselfer.
2) Muffler. Replacing the restrictive, one-outlet muffler with something that flows better will add 3 to 4hp. Once you have upgraded the muffler, exhaust is no longer the bottleneck in the SOHC engine.
3) Plugs and wires. Replace the stock Champion plugs every 10-20,000 miles. Fresh cheap plugs do much more for the Neon than expensive ones.
4) Cold air intake. Installing a CAI ($100-300) replaces the stock airbox and the restrictive snorkel. Horsepower increase varies by manufacturer and installation, but is typically between 4hp and 8hp across the middle and upper band.
5) Throttle body. For an MTX car, install the throttle body from an ATX car ($35-75, get it from a junkyard). This modification is only effective in conjunction with a cold air intake. Over-bored TBs are also available, larger than the ATX throttle body. This step is not a critical option.
6) Cam/cam gears. Replace the '96 and later cam with the original '95 SOHC spec. This cam ($140) adds about 4hp; it is available as either an over-the-counter part, or as a Mopar Performance piece. MP also offers an even hotter cam, adding about 6hp; however, idle quality will be noticeably affected. If replacing the cam, use MP valve springs as well. This package is labor-intensive and can be expensive to install.
7) Computer. Install a revised PCM unit ($200-400), which alters spark and fuel tables as well as raising the rev limiter. Aftermarket PCMs may not meet emissions requirements, and are not available for all models. Certain units may require a header or other upgrades as well.
8) Header. Install a header ($150-300). This improves engine breathing and reduces backpressure in the exhaust system.
9) Underdrive pulley. Replace the stock accessory pulley with an underdrive unit ($180).
10) Headwork. The SOHC responds particularly well to porting and polishing the cylinder head for better flow ($500-900), especially in conjunction with #6 and #9 above. The only reason that headwork comes in at #10 is due to the expense and inconvenience of having it done.
A: The DOHC does have some advantages that help squeeze a few extra horses out of it. Its main bonus is the additional 500 rpm redline over the SOHC. Because of differences in the two engines, the modification lists are somewhat different. Below is a 10-step program for getting more performance out of your dual overhead cam engine:2.9.4 Q: What is a K&N filter, and what will it do for performance?1) Remove the black weatherstripping from the back edge of the hood. This adds 1hp and is the most cost-effective mod, since it's free. Approximately 10-15 degrees cooler underhood temperature means more power, too. One consideration: with the seal removed, an underhood leak can spray coolant steam over the windshield, causing visibility problems.There are plenty of other items which can be modified on the DOHC to improve performance; however, most of them fall into the realm of "serious folks only". As mentioned above, this list is geared toward the do-it-yourselfer.
2) Plugs and wires. Replace the stock Champion plugs with exactly the same thing (a buck apiece), and do it every 10-20,000 miles. Fresh cheap plugs do much more for the Neon than expensive ones.
3) Cold air intake. Installing a CAI ($100-300) replaces the stock airbox and the restrictive snorkel. Horsepower increase varies by manufacturer and installation, but is typically between 4hp and 8hp across the middle and upper band.
4) Throttle body. For an MTX car, install the throttle body from an ATX car ($35-75, get it from a junkyard). This modification is only effective in conjunction with a cold air intake. Over-bored TBs are also available, larger than the ATX throttle body. This step is not a critical option.
5) Computer. Install a revised PCM unit ($200-400), which alters spark and fuel tables as well as raising the rev limiter. Aftermarket PCMs may not meet emissions requirements, and are not available for all models. Certain units may require a header or other upgrades as well.
6) Header. Install a header ($150-300). This improves engine breathing and reduces backpressure in the exhaust system.
7) Intake manifold. Polish the inside of the intake manifold, which is somewhat rough cast aluminum. This can be done by hand, done professionally, or by the extrude-hone method, which is fairly expensive.
8) Underdrive pulley. Replace the stock accessory pulley with an underdrive unit ($180).
9) Cam gears/cam. Cam gears allow easier adjustment of the valve timing, which can improve performance. MP also offers hotter cams; however, idle quality will be noticeably affected. If replacing the cams, use MP valve springs as well. This package is labor-intensive and can be expensive to install.
10) Headwork. As with the SOHC, the DOHC head responds well to porting and polishing. The only reason that headwork comes in at #10 is due to the expense and inconvenience of having it done.
A: K&N manufactures high-flow air filter replacements commonly found on race cars. They have a screen-covered, woven cotton filter element that is soaked in special oil to trap dirt particles. Rather than being replaced, the filter is cleaned regularly using a cleaning kit. If maintained, one filter will last the lifetime of the car. Other manufacturers, such as Amsoil, make a similar product using oiled foam. Opinions vary about which type is better, but I prefer the K&N because of its tighter weave.2.9.5 Q: How can I upgrade my exhaust piping and muffler? Which muffler is best?
K&N filters come in two main applications for the Neon. First, there is the 'drop in' style (p/n 33-2087, about $35) which is a direct replacement for the paper element, and sits in the stock airbox. The drop in filter will provide a modest performance gain, mostly noticeable as quicker throttle response. Second, there is the 'cone' style (p/n varies by size) open element filter, which is typically used as part of a cold-air induction system.
Note that cone-style filters are not legal for SCCA Stock classes. However, they are permitted in Street Touring and Street Prepared classes. The drop-in type is legal in all Stock classes.
A: Exhaust system changes are probably the most popular modification among Neon enthusiasts; they vary widely in both cost and effectiveness. Some performance gains can be had for cheap, but it takes money to look good.2.9.6 Q: What about a header and cat?
The stock piping is fairly well laid out and produced; it is mandrel bent and adequately sized at 2-1/4" diameter (which looks like a water main compared to stock Honda pipes). It is not necessary to replace the stock catalytic converter or the rest of the piping until after some serious engine modification has improved flow through the engine itself. Borla makes a high-quality, stainless steel cat-back system ($300); Dynomax makes a 2-1/2" mandrel bent cat-back system that is cheaper, but is mild steel and will rust out.
In its stock form, the bottleneck in the SOHC's flow is on the exhaust side. Fortunately for SOHC owners, the only change necessary is the simple switch to a stock DOHC muffler ($30-50). These are usually available used on the Neons.org For Sale board; they should also be available at the local junk yard. The DOHC's twin-outlet muffler is slightly louder, with a little more rumble, but it is quieter than any aftermarket muffler. Other mufflers certainly look better, but will not offer the SOHC any performance gain over the DOHC unit. Note that the stock clamp is actually part of the muffler, not a separate piece. Once it is loosened, simply pull the muffler off of the pipe.
For DOHC owners, switching to an aftermarket muffler will provide only slight performance gains, since the stock DOHC's bottleneck is on the intake side rather than the exhaust. However, it can improve looks considerably.
The next step up on the cost-effectiveness scale is either the Dynomax or the Walker Ultraflow, both of which are aluminized steel with stainless tips ($70-90). The Dynomax looks like an OEM DOHC unit, with twin slightly oversized 2-1/2" tips; the Walker has a single 2-1/2" outlet and will need an additional pipe to exit the rear of the car. The Dynomax has been dyno proven to add a small power gain for both the SOHC and the DOHC. It is notably louder and deeper than the original equipment, with a moderate boom at around 3000 rpm.
For more aesthetically-oriented folks, the Thermal ($250) and Vibrant ($220) offer polished-stainless looks with the sound and fury of mighty 4" tips (of course the rest of the piping is still 2-1/4"). The Thermal has two outlets exiting the right side of the car; the Vibrant has one each side for that "dual exhaust" look. Neither of these mufflers offers a performance improvement over the less-expensive models listed above; however, they certainly look better. Sound for both is comparable to the Dynomax: notably louder than the stock unit, but without the 'coffee can' buzz common to some Asian-market mufflers.
Borla ($200 muffler, $300 cat-back) and Pacesetter ($175 cat-back) were two of the earliest makers of performance exhaust for the Neon. Borla's design has a large single outlet with the trademark "intercooled" tip while Pacesetter's dual look was copied by Vibrant. While the Borla is a high-quality stainless steel piece, the painted-steel Pacesetter has some reputation for low quality and quickly rusting out. While both are still made, neither is currently popular.
SuperTrapp makes a version of their unique multiple-disc muffler that fits the Neon. Opinion on the SuperTrapp varies widely; some have good success while others claim no addition or are not satisfied with quality. The SuperTrapp offers "tunable" noise (and theoretically power) level by adding and subtracting discs to the tube-like muffler body.
A: Several companies make headers for the Neon in both SOHC and DOHC flavors (the head bolts are different so the two are not interchangeable); Pacesetter and Kirk are the two most popular. A header improves airflow through the engine and can help "scavenge" the exhaust waste from the cylinders. See the essay on header theory for more information.2.9.7 Q: How can I upgrade my intake system?
The second-generation Pacesetter is an improved design, but occasional bad things are said about quality. Pacesetter's header is designed to improve midrange torque, which is helpful for drag racing. This piece will work with the OEM catalytic convertor in place. The Kirk unit appears to be of somewhat better quality but is aimed at improving high-rpm power; it is more suited to road racing. Because of its long-tube design, the Kirk header requires modification to the catalytic convertor location and therefore to the exhaust piping. Mopar Performance offers both street and track headers, as well, based on these two designs.
High-flow catalytic convertors ('cats') are also available from Random Technologies and others; it is also possible to 'gut' the OEM unit. Typically they do not offer performance gains for street use and are effective only in the later stages of a build-up program when other more significant bottlenecks have been removed.
A: Iceman ($200), Kirk ($100), and AEM all make cone-style filters that draw cooler air from the front of the engine. However, these pieces may require modifications or extra work to install. All three require either relocation or modifications to the battery and/or mounting tray. It is also possible to make an inexpensive home-built CAI using an open-element cone fliter, a little creativity and some ABS pipe (PVC gives off noxious gases when heated and should not be used). All of these units will perform similarly; the major differences come from other factors.2.9.8 Q: Can I install a cold air intake if I have an automatic transmission?
The Iceman ships with a replacement mounting tray which moves the battery up and back. Also, the "battery cooler" ductwork must be removed, which allows the intake pipe to snake down to the filter, located under the battery behind the lower left side of the front fascia. Mopar Performance sells a rebadged Iceman kit; it's a bit more expensive and absolutely no different than the Knight Engineering original.
The Kirk and AEM intakes both require relocation of the battery, usually to the trunk. One vendor (Nemo) sells a kit ($220) which includes a Kirk intake and a small gelcell battery, which doesn't require relocation. The Kirk unit is a very short U-shaped pipe that places the cone filter up high, approximately in the stock battery location. AEM's product is configured similarly to the Iceman, but lacks the accessories that make it possible to retain the stock battery under the hood.
The Kirk unit is said to be the best for absolute maximum air flow; however, the difference is small over the Iceman and a bit greater over the AEM.
The Quikpipe ($120) is another popular intake, which sits behind the battery approximately near the engine controller. This is not the perfect location, and the filter is smaller than the front-mounted units. However, the Quikpipe can be effective, is less expensive than some others, and does not require any modification to the battery. It is also a good option for ATX cars.
Focuz, Ractive, and Weapon R also make air intake kits for the Neon, which put a cone filter at the back of the engine where the stock airbox sits. Since it draws hot air from above the exhaust manifold, this is not an ideal position.. With their polished or anodized tubes, the accent is on show rather than go. They are also very subject to water ingestion.
A: On ATX cars, the larger transmission will inhibit the airflow improvement to some extent. Also, The Iceman and AEM must be shortened by 3 to 5 inches so that the filter element fits above the transmission. Automatic transmission owners may want to consider the Quikpipe, which is less expensive and easier to install, but nearly as effective as a shortened Iceman. The cruise control unit, which is located behind the front fascia on the left side, also reduces the flow of cool air to these units. The Kirk/Nemo kit is more effective for the ATX as well.2.9.9 Q: Is water a problem for a cold air intake, or not?
A: One item of which you should be aware: some CAIs (the Iceman in particular) sit quite low and may inhale water under some circumstances. Many vendors claim this is not an issue, but there are documented cases of major engine damage. It does not take much water to hydrolock an engine - less than a cup full can cause serious pain to pistons, connecting rods, and the block. If you live somewhere wet, and want to play it safe, go with the Quikpipe or the more expensive Kirk/Nemo kit.2.9.10 Q: What spark plugs and wires should I use?
The Focuz, Ractive, and Weapon R intakes are equally in danger from water ingestion, as they can be hit by water splashing off the firewall. They are even more susceptible to hydrolock than the front-mounted style because the intake piping runs downhill to the throttle body, rather than uphill. These intakes are not recommended.
A: Replace the stock Champion plugs with exactly the same thing (a buck apiece), and do it every 10-20,000 miles. Fresh cheap plugs do much more for the Neon than expensive ones. Gimmick plugs like Splitfires, +Fours, etc. have not been proven superior, and in some instances hinder performance. Platinum plugs may seem to last longer, but many owners don't think they perform as well.2.9.11 Q: What does an underdrive pulley do?
Replace the plug wires with 8mm or 8.5mm wires from Mopar Performance, Magnecore, Crane, or others ($30-60). These do not actually add power, but do tend to smooth out uneven spots in the power curve. It is not worth changing the plug wires until the older ones are ready for replacement (40,000 miles or so). Really expensive plug wires such as Nology HotWires have not been proven to offer a performance gain.
A: An underdrive pulley reduces the power transmitted to accessories such as the alternator, A/C, and power steering, thus freeing up more power to send to the wheels. UDPs are also usually lighter than the original unit, which helps reduce rotating mass. It does not *add* power to the engine. Several are available from various manufacturers such as AF/X ($200) and Unorthodox Racing.2.9.12 Q: What aftermarket computers (or 'chips') are available?
The accessoriy pulley is located in a very difficult place to reach, and is an interference fit on the shaft, making it extremely tight. Removal requires a special puller tool, which can be bought from Miller Tools or rented from your local automotive store. The replacement pulley must be heated enough to expand before it will seat properly on the shaft. Consequently it can be extremely difficult to install, and is probably beyond the ability of your average do-it-yourselfer with limited facilities.
Please note that the stock unit is called an 'accessory pulley', not an 'underdrive pulley'. It is also referred to as a "harmonic balancer" and a "crank damper". Part of its job is to reduce vibration in the crankshaft, though it is not designed to balance the crank like a tire weight does. Be aware that aftermarket underdrive pulleys (no matter how well they are balanced and manufactured) have not been long-term tested for effects on crankshaft and bearing life.
A: A common upgrade among both Japanese and German cars, reprogrammed engine controllers have only come to the Neon recently. The two most common are the A/FX unit ($350, plus exchange) modified by Gary Howell's development company, and the recently-released Mopar Performance unit ($200-300, no core charge). These computers contain modified ignition and fuel information tables, which the controller uses to vary the spark timing and the quantity of fuel delivered by the injection system. In most cases they also raise the built-in rev and speed limiters.2.9.13 Q: Won't I get in trouble for switching the PCM? I thought they tracked mileage or something.
These units are not cheap, but do offer real performance gains, especially in conjuction with other modifications such as intake or flow improvements. For the A/FX unit, various 'stages' are available, some of which are not emissions-legal. All of the Mopar Performance controllers are emissions exempt. Also, most will require 92 octane gas or better to prevent detonation or 'pinging', which can be very harmful to the engine.
The PCM is specific to year and type of engine, and not all models are available. For instance, the A/FX unit is not currently available for '95 m/y cars because it lacks a fan control circuit. The MP computer is available for the '95, but is not available for ATX cars because it cannot control torque convertor lockup. See the table below for the Mopar Performance part numbers (part status information courtesy of Jim Waleke).
Mopar Performance PCMs Part Number Status 1995 SOHC P5007033 Shipping 1995 DOHC P5007034 Shipping 1996 SOHC P5007035 Shipping 1996 DOHC P5007036 Shipping 1997-99 SOHC P5007037 Shipping 1997-99 DOHC P5007038 Shipping
A company called JET offers "reprogrammed" engine control units ($400). However, analysis has determined that the only modification performed by JET was to place a sticker on the PCM case - the programming remained identical to stock. The Venom 400, another aftermarket computer, also has not been proven to significantly help performance. The Venom unit is a 'piggyback' computer that operates at partial throttle positions, but has no effect when the regular PCM goes into 'open loop' mode at wide open throttle.
A: The '95 m/y Neon was not required to be fully OBD-II compliant, and does not track mileage. '96 and newer cars, however, do store a variable that contains the vehicle mileage. This is used to set the 'Maintenance Required' light at specified intervals, and may not exactly agree with the odometer reading. Below are some additional words on the subject:2.9.14 Q: What do 'porting', 'polishing', and 'headwork' mean?"I don't know how this issue keeps coming up, but there is no mileage or VIN related legal problem with installing a new PCM in a used vehicle.Some people have claimed that the Mopar Performance computer will set the CEL unless it is flashed by the dealer, but this is not the case. If the PCM is setting a code it is a symptom of some other issue.
For example: an injector driver in your 1998 Neon's PCM fails -- what does the dealer do under warranty to fix it? They install a new PCM with the appropriate 1998 Neon programming. Once the new PCM is installed, the tech needs to use the DRB III scan tool to program the car's VIN into the PCM and enter the odometer mileage intro the SRI (service reminder indicator) mileage counter in the PCM. However, the SRI mileage counter in the PCM is not used for anything except as a reference for the dealer's MDS2 diagnostic system. Therefore, in this scenario the '98 Neon would leave the shop with a new PCM containing the car's VIN and the current mileage in the SRI counter.
Mopar Performance is currently selling emissions-exempted performance controllers for various '96-98 Dodge trucks. Since the OBD II laws (Clean Air Act of 1990) apply to light trucks as well as cars, I have to believe that the Mopar management and the massive corporate legal staff checked out the legality of selling a performance controller for these vehicles. I do not think that there is a legal requirement to update the mileage counter in the PCM; a customer could install a performance PCM on their own without running afoul of the law."
A: Headwork means modifying the original cylinder head, which is the top part of the engine containing the combustion chambers, valvetrain, and passages where air/fuel mix flows in and exhaust gases flow out. Typically this is done by two seperate processes called 'porting' and 'polishing'.2.9.15 Q:What is the difference between the SOHC and DOHC intake manifolds?
Porting means that the openings at each end of the head are bored out to a larger diameter in order to improve flow. Often they are 'port matched' to the intake manifold or exhaust manifold/header, meaning that any offsets or misalignments between the two parts are machined out. Sometimes the valve openings are modified as well.
Polishing means that the inside of each passage is polished from a rough cast surface to a smooth finish. This reduces drag as the combustion gases move along the walls and therefor increases the velocity of the air/fuel mixture. This can be done by hand, or by a process called 'extrude honing' in which an abrasive paste is pumped through at high pressure. Extrude honing is very effective but expensive.
A third form of head modification is called 'decking'. The bottom face of the head (which joins the block) is milled or ground down in order to reduce the combustion chamber volume, which increases compression.
A: The DOHC's intake manifold is made from cast aluminum, which means that it can be polished and ported to match the head. Even if headwork is not planned, it is recommended that the intake manifold runners be polished or extrude honed inside to remove casting roughness. The intake manifold is much easier to remove and polish than the cylinder head.2.9.16 Q: What is the significance of the throttle body? How do they differ between cars?
SOHC owners are at a disadvantage, except for a few lucky '96 m/y cars. The SOHC's intake manifold is made from plastic, which cannot be modified this way. However, due to a supplier problem early in the '96 m/y manufacturing run, a small number of SOHCs got an aluminum intake manifold which can be polished and ported. Oddly enough these were painted black to match the plastic piece rather than left natural metallic like the DOHC manifold. This is one reason why more high-performance parts are available for the DOHC.
The SOHC's plastic intake manifold does have some advantages, however. In its stock form it is smoother inside than the aluminum DOHC manifold, though not as smooth as a polished one. Plastic is also several pounds lighter, and transfers less heat to the intake air.
A: On a fuel-injected engine, the throttle body takes the place of the carburetor. This is where the gas pedal moves a butterfly valve that varies the amount of air let into the engine, and thus determines engine speed.2.9.17 Q: What do cam gears do?
ATX Neons have a slightly larger bore to the throttle body than MTX Neons do. This is because a small flange was added around the rim of the MTX throttle body to restrict air flow at low throttle positions; this was done in an effort to make the manual transmission car more forgiving of poor throttle/clutch technique. Switching to the ATX throttle body may cause the car to be more jumpy and difficult to drive smoothly.
If done in conjunction with a cold air intake, switching to the larger ATX TB seems to improve acceleration for the MTX car, though it has not been completely quantified. The throttle body is available from junkyards ($35-75); however, when making the swap be sure to retain the sensors that came with the original car because the different transmissions use different types of sensor. Cruise control mechanicals complicate the swap as well. Also, retain the original throttle plate shaft from the manual transmission TB, which helps limit the jumpiness that was engineered out of the MTX in the first place.
Over-bored TBs (larger than the ATX unit) are available through Nemo, Howell, and others. Both manual and automatic cars can benefit from an over-bored throttle body; however, this is only effective in conjunction with a cold air intake. Note that homemade oversize TBs sometimes reuse the OEM throttle plate, meaning that the restriction has not been removed. Buy one from a reputable dealer instead.
A: Cam gears replace the fixed factory gears at the end of the camshaft, which carry the upper end of the timing belt. They are used to tune the valve timing relative to the crank. To make this job easier, they are indexed with decimal degree markings and are designed to allow precise adjustment. This can be done using the stock pulley; however, it is not nearly as easy. Cam gears do not add any power themselves - they are merely a tuning tool. Because of variation in each engine, cam timing is not perfectly adjusted at the factory. Most engines can benefit from some degree of fine tuning.2.9.18 Q: Enough of this sissy crap. I need boost!
On the SOHC, a cam gear is used to adjust the cam timing relative to the crank position, since the intake/exhaust overlap is fixed. Advancing the cam will increase low-end power; however, it can cause the upper end to fall off dramatically. Conversely, retarding the cam will improve high-end power at the cost of low-rev grunt.
Cam gears are also used to adjust the relative timing of intake and exhaust valves on the DOHC. As a rule of thumb, the general method of tuning is to retard the exhaust cam in small steps with multiple timed or dyno runs between. Continue retarding until performance stops improving, then advance slightly.
This kind of tuning is by necessity a compromise. Otherwise, manufacturers would simply set the cam for maximum power at the factory! Which method you choose depends entirely on the type of performance for which you're looking.
A: Moving beyond normal bolt-ons like those above means finding a way to force more air/fuel mix into the engine than it can inhale naturally. The two main methods of applying boost pressure to the intake are turbocharging and supercharging. These two units accomplish the same goal, a dramatic increase in power, by somewhat different means. This discussion will be very limited, because the details could be an FAQ unto themselves. Both systems are very expensive, with kit prices starting around $3000 - not including installation or improvements to other engine components to compensate for the added stress.2.9.19 Q: Which is better, turbo- or supercharging?
Turbocharging utilizes exhaust gas to spin a turbine, which drives (via a shaft) an impeller to force air/fuel into the intake system. Turbos are very efficient because they utilize wasted energy; however, they can be finicky to install and maintain. Also, turbocharging creates a large amount of heat, which must be dealt with effectively. Several kits are currently available; they range from near-prototypes to complete packages. The first true kit was developed by Hahn Racecraft, and enjoys an excellent reputation for quality. Turbocharger installation is beyond the amateur mechanic and requires a professional. Due to differences in the intake manifold, among other things, the Hahn kit is available only for the DOHC.
Supercharging uses a belt-driven compressor, which come in several varieties such as the screw, centrifugal, and roots types. Boost is available even at very low rpm; however, the 'blower' itself adds a parasitic load to the engine approximately equal to an extra air conditioner. No supercharger kit is currently shipping, though Rimmer Engineering and Jackson Racing (both big in the Import scene) are said to be developing Neon kits. Rimmers product is said to be close to release; however, development problems have set the project back several times. Typically, supercharger installation is feasible to a skilled amateur with good facilities; this is an advantage for the system.
Both systems benefit greatly from an intercooler, which is usually added as part of a 'Stage Two' system. Physics dictates that compressing a gas also heats it; hot air is less dense than cool air and does not burn as well. An intercooler is, in essence, an additional radiator through which the intake air is piped before entering the throttle body. This cools the air to a better charge temperature and improves combustion.
A: In general, turbocharging is a better system because its potential maximum power is higher than the supercharger. However, supercharger systems have some advantages in their favor. Which system is right for you will depend upon your application.2.9.20 Q: What about nitrous oxide?
The turbocharger's effectiveness increases with rpm, so that power increases smoothly. In a front wheel drive car like the Neon, this means that traction is not overwhelmed at the launch, and the power is effectively put down after the car has begun moving. For racing applications with a small engine, the turbo's even power delivery and high top-end performance give it a clear advantage over the blower.
However, the supercharger excels for a predominantly street-driven car, because its constant boost adds the low-end torque missing from nearly all smaller engines. The 80/20 rule applies here - the supercharger will give most of its power gain in the rev range where most people spend 80% of their driving time. Additionally, the installation is simpler, meaning that the average street performance car driver has a hope of being able to 'do it yourself'.
A: Nitrous oxide is like steroids for your engine: it'll make you strong, but ultimately it's unhealthy and leads to premature death. Nitrous oxide does not actually burn in the engine. Rather, rapid cooling caused by the expanding gas drastically increases the density of the air/fuel mixture, allowing more into the engine. This leads to large (50 to 150hp) but short-lived (measured in seconds) boosts in horsepower.
Nitrous systems can cause many problems. The engine will run lean, causing melted pistons, unless a carefully managed program is followed to deliver additional fuel. The increased internal stresses often result in crank, rod, or piston failure. Also, nitrous systems by design operate under very high pressure (thousands of pounds per square inch) and improper installation is a serious safety hazard. It must be a professionally designed and installed system.
This is not to say that the 'throttle in a bottle' is not a highly effective method of improving short-term performance. However, it should only be considered for racing applications, or by those who (like most racers) consider engine replacement a 'routine maintenance item'.
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