Breathing Mods

After starting in on my system, watching others with their setups, and doing tons of research both on-line and at the library, I feel the best way to approach these mods is from the outside in, alternating in and out.  You'll see what I mean as we get started.  By doing this, you normally attack the most restrictive parts of the system first, generally spend less money, and they are normally progressively harder to do yourself as you go along.

Muffler

Almost without fail, the muffler is the most restrictive part of any car's entire powertrain.  More often than not, it's also an eyesore.  Even the guys who don't know what they are doing go for the muffler first.  We're going to learn what to do, what to avoid, and why.  For a great technical discussion on exhaust systems in general, read the article by David Vizard (p1, p2, p3, p4, p5).  And for those of you that think that an exhaust system needs some "backpressure" to work properly, read this discussion thread.  Another pitfall to avoid is the concept that louder equals more power.  If you read Mr. Vizard's article, you'll know that this is not the case.  Flow through the system is the key thing to keep in mind.  And here are some flow numbers.  Notice that some of the "performance" names like Flowmaster and Dynomax aren't as free-flowing as you would think.  Why do people still buy them?  Well, maybe they like the sound, maybe they bought a bigger size to make up for the flow, or maybe they just wanted the sticker on their car.  Now, your area might have laws on noise levels.  You may or may not want a louder system.  Quite frankly, I can't see putting one of Mr. Vizard's termination boxes under a Neon, or any other sport-compact for that matter, so that option is out for the time being.  If you can find a similar car with the same muffler that you are looking at, you'll be able to get a feel for the sound in advance.  If you get the muffler and find out it's just too loud, you can always put in another glasspack or a Moroso Spiral Flow (no bench test results yet) in the system to quiet things down.  To help eliminate some extra flow restriction, you can cut off the last 90 degree bend and have the exhaust exit straight out the back on the driver's side (requires non-stock style muffler).  Muffler choice is personal and complex.  The most performance can be had from any of the name-brand, true straight-through mufflers like the Hooker Maximum Flow, the Dynomax Ultra Flow, and the Thrush Magnum glasspack.  Be sure to check your local laws regarding sound levels, and always ask around neons.org for opinions before buying.

Intake Tube

Often referred to as a Cold Air Intake (CAI), most are not.  For a CAI to do it's job properly, it needs to meet a few criteria.  First, it should be made of a material that does not conduct heat well.  A good example is ABS plastic, a hard rubber compound would work as well.  A bad example would be just about any metal.  So those shiny e-bay specials are already starting on the wrong foot.  Second, it should not travel over hot components.  Particularly for the Neons, but for many other sport-compacts as well, the tube often travels over the engine and/or transmission and/or exhaust manifold.  Third, it should be pulling air from the coldest location possible.  This will almost always be from the front of the car near the ground.  Finally, K&N makes excellent filters.  Plastichrome paper filter cones in 145 cool colors belong with the e-bay specials.  I'll also add here that "ram air" is a term that has been misused, misunderstood, and abused by just about everyone.  It originally referred to the effect caused by proper intake runner tuning, where the pressure waves would actually force more air into the cylinder than would be normally possible without forced induction.  Keep that term in mind, forced induction.  Pointing the air inlet tube in the direction you are going is not ram air.  Sure, if you stick your arm out the window, you can feel the pressure of the air push it back, right?  So there must be more pressure  in the intake on a "ram air" intake tube right?  Nope.  What you are feeling is static compression.  There is no mechanical means of maintaining that pressure.  It's a tough concept to understand.  Just take my word for it.  You'd have to be doing well over 100 mph before you would see even a 1 psi increase in manifold pressure.

Budget - Use the stock intake tube from any early 1990's Dodge/Plymouth car/minivan that had the 3.0L V6 engine.  Cost at a salvage yard should be about $10.  Attach a good filter on the end of it, costs about $20.  Hose clamps, $5.  For this mod, you will most likely have to do some cutting to your stock battery tray.  As an option, you can cut the hose wherever you feel the need and insert short pieces of exhaust piping to route the intake tube however you want.  Dyno results are practically identical to the Iceman.

Best - Iceman makes what is considered the best CAI for the Neon.  It comes with a replacement battery tray.  Costs $200+.

Best Buy - By far, the "ghetto" 3.0L intake.

Exhaust Piping

The wannabe tuners often flash out the term "i/h/e" when they talk about mods.  That's Intake, Header, and Exhaust to the layperson.  So why aren't we getting to the header?  Well, because there's a fair amount of pipe between the muffler and where the header will eventually go that we may need to fix first.  Many of the sport-compact cars come from the factory with undersized, crush-bent piping.  The Neons came with 2.25" mandrel-bent piping, which is so much better than what you might find on other cars.  Even so, if you'll recall from the "No Loss Exhaust" article, you will need to have larger piping as your engine puts out more power.  For the Neons, the chance of you exceeding 225 HP without forced induction or nitrous is practically nil.  So 2.5" mandrel-bent piping is the answer.  Any larger is just a waste.  If you do plan on nitrous, etc., think about where your HP goal is.  3" piping should cover you to nearly 500 HP.  If you are going above that, you belong at a more advanced web site...  Going too large with your piping can hurt low end torque since exhaust gas velocity is lower, and exhaust gases may get sucked back into the cylinder before the exhaust valve closes.  Don't worry, once you get a god header with a proper merge collector, the problem will go away.  Dynomax makes 2.5" piping that is a factory fit for $75 plus shipping.  If you want it installed, a local shop will charge around $50 to weld everything up.

Throttlebody

To determine the most flow you will need for your engine, there is an equation: (displacement in cubic inches/2)x(maximum rpm/1728) = maximum flow in cubic feet per minute.  This assumes 100% volumetric efficiency, of course.  For the from-the-factory engine, you will probably never reach 100% volumetric efficiency.  In fact, most cars, at best, run in the 80% range.  And it's not constant either, it varies with load and rpm.  So why go to a bigger throttlebody at this point?  You don't have to.  But as you start making your engine breathe better and rev higher, and later when you start controlling the fuel and air mixture better, and even later when you start manipulating internal airflow (like using a properly tuned header and intake manifold with the right camshaft), your volumetric efficiency could be up in the 110% range or more (not likely, but possible).  So now is a good time, because the header is next.  For the Neon's 2.0 liter engine, the factory 49 mm throttlebody (TB for short) on the manual transmission is plenty for stock use.  As a step up, you can use one from a Neon with an automatic transmission, since it is 52 mm.  Even at 110% volumetric efficiency at 8200 rpm, you won't have a need for anything larger than a 56 mm TB.  Later, if you increase your displacement by boring 0.040" over, a larger 60 mm TB would work just fine.  Putting one on now that is too big may reduce air velocity, allowing it to heat up more, and possibly reducing the air/fuel mixture quality for cars with TB injection (not Neons).  In any case, you won't see the full effect until you fix the intake manifold, since the hole where the elbow enters the plenum won't fit a 52 mm TB plate.  You'll either have to make that hole bigger (DON'T break out the Dremel just yet!) or replace the intake manifold with a better one.  Also, you will need to make sure that the TB and manifold are port matched.

Budget #1 - 52mm TB from a Neon with an automatic transaxle (ATX).  If you already have an ATX, see Budget #2.  Costs around $30 on ebay.

Budget #2 - Either the 56mm TB from an early 1990's V6 Jeep Cherokee, or the 60mm TB from the V8 Jeep Cherokee.  Cost at a salvage yard about $40.  Some modification is required.  I'll post a link soon...  or you can do a search on neons.org for it yourself...

Best - Depends on your application.  If you want a showpiece, Modern, Howell, and a few others make quality 55-60mm TB's that look awesome for $200-250.  If you are all motor or nitrous only, any 55 or 56mm TB will do, since they all work the same.  If you have forced induction or larger displacement, any 60mm sill do.

Best Buy - Either of the Jeep TB's, depending on your needs. 

Header

In the "i/h/e" wannabe tuner speak, by "intake," they usually mean the e-bay special, by "exhaust," they mean muffler, and by "header," they mean something with individual pipes attached to the head.  Most tuners, wannabe and otherwise, have little to no understanding of exactly what a header is and what it does.  For some good reading, see the S&S page, an excellent tech paper, another tech discussion, this one as well, the "pressure wave tuning" portion of this site, and this lecture (refresh the page if it doesn't show up the first try).  Are you starting to notice a trend here?  The shiny, short-tube e-bay specials are, you guessed it, worthless.  Well, not completely.  They do flow better than the stock exhaust manifold at least.  But if you are going to dish out several hundred dollars, wouldn't you like to know what rpm range the header is actually tuned for?  Wouldn't it be nice if that range was below your redline?  So how do they keep selling?  Two reasons.  First, there's a sucker born every minute.  Second, proper length headers usually mean moving or removing the catalytic converter, which violates Federal regulations.  Now, you or your buddy or some guy on-line may have passed his emissions inspection with flying colors, whatever.  The law is the law, so if you go the long-tube route and get ticketed, don't come crying to me, your mechanic, or the manufacturer.  That said, if you have a shed or garage, it might be a good idea to keep the stock exhaust in there for emissions testing.  If you are considering buying a high-flow catalytic converter (cat), why bother?  It's just as illegal to move it or replace a functioning cat as it is to remove it.

Budget - Hedman Headers makes the Chikara header for the Neon.  It is a very short tube, direct fit header, meaning you don't have to make any other alterations to your exhaust system.  The runners are far too short do help make any real power.  But it does flow better than stock, is CARB exempt, and installs easily for under $200.

Best - Blackdog Motorsports, without a doubt, makes the best headers for the Neon.  They are dyno proven 15 HP above their next highest competitor (Kirk Racing).  Each header is custom made for your application, and wait time can be up to 3 months.  But you are assured the best performing header available.  I would strongly recommend coating the mild steel to prevent rust.  Uncoated head costs around $325.  See their site for more details, or give them a call!

Best Buy - Still Blackdog.  There are other decent performing headers available for under $250, but BDMS headers give the most HP gain per dollar.

Other Options - 

Intake Manifold

Like the header, the intake manifold runners can be tuned to improve volumetric efficiency, and thus improve power.  There are some detailed class notes on this, and an excellent article worth reading, which you probably should have read before buying your CAI, but there's only so much you can adjust on those anyways...