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Old 01-18-2005, 09:08 AM   #1
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Default How Much Horsepower Can I Expect if I Install...

By: Extasy

Looking to add some horsepower to your ride? Well with the basic bolt on items like intake, header, and exhaust, it breaks down to what will work with what you have. Online searches are probably the best for comparison shopping and third party reviews. A lot of manufacturers are more interested in selling you their product than whether it actually works so believing what they say can be a tough call.

Also, Honda motors are very efficient, probably some of the most efficient among any car maker out there so pulling power out of a Honda motor isn’t easy. The B16 makes 100 hp per liter of displacement; the S2000 makes 120hp per liter. Honda puts a lot of time and money into these engines and unfortunately they are pretty much already running at their full capacity when you purchase the car from the dealer.


I get into some arguments in this area since I think the OEM Honda intakes are very good. They aren’t all that restrictive, but their major downfall is “heat soak”. Plastic likes to hold heat, and this effects performance.

I could go on for hours over cold air versus “shorty” intakes. The cold air intakes get air from the lower part of the front bumper, where as short ram intakes usually get air from just behind the radiator. The cold air intakes will benefit you simply by providing colder air; the shorty intakes will help with somewhat cooler air than OEM, mainly because the intake tube is typically metal, which can dissipate heat better than the OEM plastic/rubber setup. Predict about a 3-6 hp gain from an after-market intake system.


A header will help to open up some breathing room for your motor. They will primarily benefit the D-series motors, B16A, B18C, or any motor equipped with a cast iron manifold from the factory. The B16B, B18C5 & F20C have a very good header in OEM form, so the major benefit here would be weight savings.

So you decide you want a header; what do you get? A 4-2-1 or 4-1 design? This is mainly personal preference. 4-2-1 headers typically help in making lower RPM power where as the 4-1 designs will help in the higher end of the rpm band.

There are many headers out there, and quality is also a key factor. Do some homework on which brands work well for your particular motor.

You can probably expect a gain of around 5-7 hp on a stock motor with an after-market header. Keep in mind though, that this may not be an even 5-7 hp across the entire RPM band, but more likely 5-7 hp above or below 6000 RPMs depending on the header design. It can also be more specific to a particular RPM range (4300-5100 RPMs for example), or at red-line, which is close to where many Honda engines make their peak power.


Loud means fast right? Actually, in some ways it does, though bigger isn’t ALWAYS better. Engines don’t like backpressure, especially turbo'd or supercharged engines. Most after-market exhausts are larger than stock, but some are too large. If the exhaust is too big then the engine can’t effectively “scavenge” the exhaust out of the cylinders. The exhaust helps pull air out of the motor; too big and it can’t effectively “vacuum” the air out. Since a turbo'd/supercharged car, is forcing out excess amounts of air you would want a larger exhaust.

Construction and fit are also deciding factors. Part of making a car faster is making a car lighter. Mild steel will rust like the OEM exhaust; stainless will last forever but will be heavier. Some companies, like Apex'i, use aluminum which will not rust and is lighter and there are other companies who make ultra-lightweight exhausts from titanium.

Here you could expect another 5-7 hp gain like with the header. With a 4-1 header the exhaust power gains would more than likely be at higher RPMs.

OK! So now that you’ve got a 5 hp gain from the intake, a 7 hp gain from the header, and a 7 hp gain from the exhaust system, your car is now 19 hp faster, right? WRONG!! In reality, it’s probably about an 8-10 actual hp gain overall when you account for drive-train power loss. Without some dyno-tuning and cracking open the motor, don’t expect any more than about a 10 hp gain; however, your car is now lighter, which will help to maximize that horsepower gain.

Last edited by 94accordex; 12-04-2007 at 10:02 PM. Reason: Added additional formatting
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