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VTEC MODIFICATION PAGE

 

All the modifications on this page are for Normally aspirated applications.

LAST UPDATE: 5/1998

* Dohc Vtec engines are very hard to improve upon since they already have very good components from the factory.  There are some performance parts out there that will not  increase power, and in some cases, will even cause loss of power or engine damage.

Intakes:  The purpose of switching to a higher flowing or cold air intake, is to increase the amount of oxygen being taken in by the engine.  Almost every modification you do is done to increase Volumetric efficiency.  Colder air is more dense, this is a reason why on a cold night, your car feels more powerful.  Cold air intakes are very effective, but expensive.  A good alternative would be a K&N filter replacement in the stock airbox, connected to a hose leading into the bumper to allow cooler air to be taken in by the engine.  This mod would cost anywhere from $35 to $60 depending on the price of the K&N replacement filter.  This setup would not offer the ultimate gains in (intake) power.

 I have the Spoon Sports in-box filter in my GS-R.   In-box filters offer a good performance gain over the stock filter element, but for ultimate power, they are somewhat restrictive.  On the dyno, this filter proved to be somewhat restrictive, causing a loss of 1.3hp compared to an open element filter system. 

UPDATE: I recently replaced my in-box filter with an AEM cold air intake system.   Dyno testing showed that my in-box filter was causing a loss of 1.3hp compared to an open system. The car has better throttle response with the AEM intake, but it is MUCH louder.  On the dyno, the AEM  actually added more than 1.3hp.  It added 5.7hp, bringing the total hp to 171.9 (corrected).

K&N Engineering also offers in-box airfilters.  The K&N filters are made of cotton and are re-usable.   

The best cold air systems on the market today are the AEM and the ICEMAN.  The ICEMAN is two piece so during rainy seasons, the filter can be moved into the engine bay.  These two intakes offer the most hp gains compared to other intake systems on the market. They replace the entire intake system from the throttlebody onwards. They can cost anywhere from $190 to $250.

FACTORY COLD AIR INTAKE

This Honda factory illustration clearly shows the difference between the Type-R and non-Type-R Integra  intake system.  On the Type-R model, cooler air is drawn from inside the fender area.  

      

Header:  The VTEC engines come from the factory with a very efficient exhaust manifold.  This is the reason why most aftermarket headers dont add any power.  Proven headers available for the GS-R are the RS*R, Spoon Sports, and Mugen header.  

                                                                                                       There are two types of header design, a 4-2-1 (Tri-Y) and a 4 into 1 design.  The 4-2-1 design is very popular, and offers good midrange power.  The 4 into 1 design offers more high end power, but sacrifices bottom end torque.  The main problem with 4 into 1 headers in the past has been ground clearance, but the power gain the 4 into 1 header offers is unmatched by the 4-2-1 design.

Comptech and Greddy have both introduced their new header for the GS-R.  These are excellent alternatives to the DC header.  The problem with the DC header is that the top section of the header was originally developed for the 130hp B18A in the 90-91 Integra.  DC continues to use this upper section for all Integras since 1990 and the Del Sol VTEC.  In my opinion, a 130hp engine with a 6500rpm redline has different exhaust needs than a 170hp 8100rpm redline motor.  So I advise against the DC header.  

Exhaust: At this point, there are MANY good cat back exhaust systems on the market, its just a matter of how big of an exhaust tip you like!   Notable makers are Greddy , HKS , RS*R , DC Sports  , APEX, and Comptech.  The main problem with these exhaust systems is the high cost.  They start at around $400 and can go as high as $700.  These are all complete cat-back systems (except HKS Superdragger), which means they bolt on after the factory catalytic.  

If you're on a budget, you can have a local muffler shop build a custom exhaust system for you. The pipes wont be mandrel bent, but unless you are making A LOT of power, mandrel bent pipes dont really make a difference.  It is a good idea to use a stainless steel muffler such as an Ultraflow or a Borla XR-1 for durability.

Throttle Body:  A larger throttle body will flow more air and offers a crisper throttle response.  Make sure to port match the intake manifold to the throttle body.  Tuners take a stock throttle body and bore it out 3-7mm depending on the vehicle.  This is a good mod for the GS-R.  

           This is a PYR modified throttle body.

RC Engineering offers a complete throttle body replacement.  These are not modified stock pieces, they are brand new billet pieces.  They are very large and cost twice as much as a modified factory piece.   They are called "Monster" throttlebodies.

Coolant Bypass: This is a trick used on Group N and Group A Honda race cars.  It is very simple, costs under $1.00, and takes about 15 minutes to perform.  It involves disconnecting  the two coolant lines that lead to the bottom of the throttlebody.  DO NOT PERFORM THIS MOD WHEN THE CAR IS HOT, LET THE CAR COOL DOWN COMPLETELY.  You will need a "straight hose connector", which can be found at any auto parts store.  Disconnect the two coolant lines that lead to the bottom of the throttlebody.  When you disconnect the pipes from the throttle body, coolant will leak out.  Check your coolant level afterwards to make sure it is adequate.  Insert the "straight connector" between the two lines and join them together.  Use the clamps that are already on the pipes and secure them tightly on the "straight connector".  

The purpose of this mod is to keep the coolant from heating up the throttle body.  Although the throttle body will eventually heat up due to the heat transfer from the engine, it will be considerably cooler than before.  

*This mod is not recommended for vehicles that operate in VERY cold climates.

Type-R Intake Manifold on GS-R:   coming soon.....slight modification of manifold req'd

Camshafts:  DON'T BUY RE-GROUND CAMS.  Simply put, they are Just Garbage. A billet camshaft has the correct valve angle geometry and will also provide a much longer valve train life compared to a re-ground cam.  Good billet cams are the factory Honda Type-R cams, Spoon Sports cams, and the Toda racing cams.

In terms of cost and reliability, the Honda Integra Type-R camshafts cant be beat.  They are OEM and the dealer sells them for $278 per cam.  The intake cam alone adds over 7 horsepower, and both cams will add over 10 horsepower un-tuned. Another alternative is the new Civic Type-R intake camshaft which has 3 degrees more duration on the intake camshaft. Dyno testing has shown that in a GS-R, it adds 2 more hp than an Integra Type-R intake camshaft.  The Spoon Sports and VISION cams are made by TODA Racing.  TODA Racing is a racing company and machine shop that manufactures parts for other Japanese tuners.  These cams can cost anywhere from $600 to $1300 per cam depending on if you buy from Spoon, VISION or TODA.   They offer street cams to full race spec cams.  Power increases range from 14hp to 29hp.  

Cam gears (below) are very beneficial on GS-R engines equipped with the Type-R intake camshafts. On my GS-R, peak horsepower increased by 16 at the driving wheels, and the midrange power increased by 21hp at one point !  

Valve System:     coming soon....wanna rev high?

Adjustable cam gears:  These will allow you to advance or retard your camshaft timing.  On GS-Rs, they are tuned to increase torque and midrange power.  This a VERY good mod for the GS-R.  The only problem is that to take full advantage of the gains, these have to be tuned on a dyno, and some people don't have access to a dyno.  Most of the cam gears on the market today are manufactured from aluminum.  While aluminum cam gears are cheaper to produce and offer a larger profit margin to their producers, they are not durable.  Most of the aluminum gears (AEM, STR, etc) have the timing marks silk screened or painted on.  Over time, they will wear off.  They are also more prone to stripping if tightend too hard.  I recommend going with steel cam gears such as HKS , JUN , Toda Racing , or Spoon Sports (also made by Toda Racing).  

These are JG gears.  

I have Spoon Sports cam gears on my Integra.  The Spoon Sports cams have index marks on them, some of the gears listed above do not.  

* Caution, when advancing / retarding the intake cam, the ignition timing will also be advanced / retarded automatically since the distributor is on the intake cam.  Make sure the ignition timing never exceeds 18 degrees.

Larger VTEC Solenoid:  coming soon.....Is this mod worth it or not?

Cylinder Head Modification:  It is very hard to improve upon the GS-R cylinder head.  The only company that has had any success with ported GS-R heads has been  Honda motor company.  The GS-R cylinder head is very efficient from the factory, buti t can benefit from a mild port job.   I used to have a link to DPR under this section, but I've changed my opinion of them.  A friend of mine recently had $7,000 worth of work done on his GS-R at DPR.  They estimated that his car would be finished within 4 weeks.  To make a LONG story short, it ended up taking DPR 10 weeks to complete this simple project.  I estimate that a project like this would've taken 4-5 days to complete.  

Higher Compression:  Higher compression can be achieved in four ways.  With higher compression pistons , a thinner head gasket , by milling the head, or by reworking of the combustion chamber (cc ing). On s street driven B16 or B18C, the "safe" compression with 92 octane gasoline is around 11 .6 to 1.  Even higher compression can be employed, but the ignition timing will have to be dialed back  (manually or via a knock sensor) to prevent damage.  Also, higher compression will require higher octane gasoline.  When increasing compression via milling or a thinner head gasket, camshaft timing will automatically get retarded.  The cam timing can be brought back into desired spec with adjustable cam gears.
Stroker Kits:  Stroker kits increase overall displacement.  The kits for B16A engines increase displacement to 1.8 liters, and the stroker kits for the B18C and B16B engines increase displacement to 2.0 liter.  Kits include a new crankshaft, rods, pistons, and all additional parts.  Power gains will depend on compression, cams, and manifolds.  But they will generally add at least 20hp and 16 lbs of torque.  
Sport Injection:  Sport Injection replaces the entire intake manifold and throttle body with 4 throttle bodies (one for every port), it is very similar to Mikuni or Weber side draft carbs.  In Japan, many companies offer this setup for Hondas, and some even offer kits that work with the stock ECU and wiring harness.  In most cases, the Sport Injection is teamed up with aftermarket fuel injection such as Motec, TEC II, or Accel DFI.  In most applications, sport injection will add 20-30hp.  The draw backs are the high cost and loss of torque due to the short intake manifold.  
Ignition / Wires:  An upgraded ignition is only needed in a situation where combustion chamber pressures are higher than the stock ignition was designed to handle.  An upgraded ignition is a must on turbo/NOS Hondas, but on a normally aspirated Honda, (unless its running real high compression) it's not needed.  An upgraded ignition will help the engine run smoother if it is equipped with a large camshaft.  Dont expect large power gains on a normally aspirated car.

Performance sparkplug wires will only add power if the stock ignition wires are real old and are causing the engine to lose power.  

SparkPlugs:  The GS-R comes from the factory with platinum tipped sparkplugs.  The main reason for this is to decrease maintenance costs.  The platinum sparkplugs do not have to be replaced until 60,000 miles because they can resist corrosion.  Regular copper plugs dont last as long as platinum plugs, but they provide better performance because copper is a better conductor.  Just by switching to regular NGKs, you can expect a 3hp gain on a GS-R.  Not bad for $10.
Vtec Controllers: Vtec controllers allow the user to lower or raise the vtec engagement point.  They are supposed to improve acceleration and were developed in Group N racing honda Civics.  There are many vtec controllers on the market, but they offer little performance gain for the money.

  This is a Data systems vtec controller.  Mugen, Spoon Sports, etc , also make vtec controllers.

 ECU Upgrades / Chips:  For the GS-R, the stock program or the stock program with a 8700 rpm fuel cut is the best.  Most people get different results with Chips.  Dont use a chip that is meant for a stock car if your particular car is modified.  The best thing to do is to get a chip that is made for your specific modifications.     Most ECU tuners are aware of this and offer many different programs for each vehicle.  

Tuners are G-Force Engineering    ,  Dinan , JET, and Superchips.  

Fuel Risers:  A fuel riser increases fuel pressure ONLY under WOT (wide open throttle) situations, unlike fuel regulators which increase fuel pressure at all times.  Adding airflow enhancements (intake, exhaust, header, TB), lean out the engine at WOT. Depending on current mods, the fuel riser will add between 2-9hp. Dont put this on your car if all you have is an exhaust.  The riser mounts between the stock regulators "out" side and the fuel return line.  

Fuel Controller:  An electronic fuel controller allows precise tuning of the fuel mixture. It allows the user to richen or leanout the fuel mixture.   They are useful if your car is equipped with larger injectors or a fuel pressure regulator.  Combined with those mods, the fuel curve can be precisely tuned with the fuel controllers.  For VTEC engines, the Field SFC-VTEC is a better deal since it is a VTEC and FUEL controller.  

The Data Systems unit (above).        The Field unit is a fuel and vtec controller.           

Light Flywheel:    A lighter  flywheel reduces rotational mass.  This will allow the engine to rev much faster, and will increase acceleration.  There are drawbacks to a light flywheel however.  The engine will be able to rev faster, but this also means that the revs will drop faster.  If the flywheel is too light, the car will lose a good deal of torque.  "choose your flywheel wisely".  

 

Light is good, but too light on a daily driver will make you suffer during rush hour traffic.

Type-R or Civic Sir Tranny: coming soon....better gearing and standard LSD

LSD:  LSD stands for Limited Slip Differential.  Most transmissions have an open differential which allows each wheel to turn independent of the other.  This is the reason most drag racing Hondas have the stock differential welded.  A welded differential will cause both wheels to spin together, this offers greater traction, but around turns the inside wheel needs to turn at a slower rate than the outside wheel.  That is the problem with welded differentials. A LSD will replace your stock open differential. It allows the wheels to spin independently until one wheel starts to lose traction, when this happens, power is transferred to the wheel with greater traction. For a Normally Aspirated street Honda, a torque sensing  differential is best.   Probably the best street LSD for the GS-R is the Honda Type-R LSD.  

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