Headers are probably one of the most debated topics for the IS300 platform. There are lots of reasons to buy them – some of them good, some of them bad. Most likely you’re considering headers because you want to gain power or because you want to increase your exhaust sound… right? Or, maybe your cats are clogged and you just need something to replace them.
Whatever the case may be, you’ll benefit from a better understanding of each style of header and what each style does. There are two main types of headers: long-tubes (often associated with equal length headers) and short-tubes (aka: shorties).
Long-tube headers: Because of their design, long-tube headers are known to produce power in the mid-to-high RPM range. Long-tube headers have lengthy individual runners coming out of each exhaust port, and they typically merge into a common collector (also called a “dump collector”). As a result, the scavenging effect takes place later, which will produce the most power “up top.” This provides for a lot of potential for peak horsepower, but waiting until 4000 rpm and above can be miserable for a street-driven car. Now, for a high-quality set of long-tube headers (such as the original Mazzuri product or the Team Lexus race header) this doesn’t hold true. The Mazzuris made gobs of power of top, but they also improved the entire power-band, though they are quite raspy. Another example of this is the Dezod Development header (either Red or Green), which features their twin 3-1 hand crafted low angle merge collectors and their much-hyped 6-2-1 design. The Megan Racing headers are nowhere near the level of the Dezods or Figs Engineering (or even any of the “OG” headers), for the record. I’ve attached the dyno sheet from Dezod’s website for their Red headers, and as you can clearly see, not only is peak power significantly improved, but also the midrange power is substantially improved. You won’t get this with a cheaper header. Period.
Short-tube headers: If you peek under your hood, you might notice that the factory headers are a form of short-tubes. This is to maximize low-end torque (aka: usable power). As a result of the shorter runners, the scavenging effect occurs earlier and is less drastic. You might find that you’ll make less peak power, but you’ll have most of your power before a car with cheap long-tube headers even starts making any (again, with a high-quality set of long tubes this doesn’t apply). So if you’re racing from a dig, unless you have a very high stall torque converter, the car with the short tube headers is going to pull away from you in a hurry. With a short tube header, you’ll exceed the stock low end power, but you won’t make as much up top.
Okay, so now that you have an idea of what these two popular header styles do, which one should you buy? Well, frankly, you need to take these characteristics and apply them to what you wish to accomplish.
Megan Racing’s header is probably the most well-known example of the long-tubes, mostly because of its price. Speaking from experience, the Megan header does indeed provide an increase in power, but the power does not come where it’s needed. Due to the low amount of R&D and quality control that is inevitable at its price point, the scavenging effect is not as well utilized as it could be. It makes power, but it leaves a good amount on the table: power you’re not going to find for $200. In addition, waiting until 4000 rpm for the catless header to overcome its lack of backpressure can be quite annoying.
On the other hand, Dezod Development offers a high-quality, American-made long-tube header for our platform. Another American company, Figs Engineering, recently released their own stepped-primary race header. As it is so new, I have not yet come across a dyno sheet for the Figs model, but it’ll compete with the Dezod models, and Mike (Figs) is putting in tons of hours getting them ready. These two headers are the cream of the crop, but many of today’s IS owners say that they’re “too expensive” or “not worth it.” Frankly speaking, if you want to gain power through headers, you’re going to have to open up the wallet a little bit. The saying “pay to play” holds true, and I stand behind it.
OBX headers are something to consider, but even then they’re not ideal. While not a ton of R&D went into their development, they fairly mimic the OEM design, and as such provide a small bump in your usable low end torque production. Realistically, a very high percentage of IS300s on the road today are street cars. Sure, many are track beasts, but for the average IS300 owner, power is needed down low. It’s not often you get above 5k RPM unless you’re really pushing the car. As such, it is more effective to have less peak power, but a large percentage in the low-to-mid range (speaking in terms of a street driven/daily driven car). If you truly want to make good gains, you’ll have to actually spend some decent money on headers.
Now, as I said, both styles of headers will gain some power. Their style (short or long) will determine where that power is gained. Neither will gain something crazy like 50 horsepower, which raises the question: are headers truly worth it?
I can say from personal experience that Megan headers are not worth it. The power band is so much better on stock headers (unless you only plan on running the expressways, in which case Megans might suit you better), especially when tuned. OBX headers will provide a small bump in low end umph, but if you’re looking for true gains with headers, then you need to either source a used set of Mazzuris or Xerds (as they’re both discontinued), or you need to purchase a new set of Dezods or Figs headers. The fact of the matter is that you’re not going to get high-quality power with a low-quality product.
Both Figs and Dezods are impressively high-quality, and offer the best overall power increase. Yes, they are indeed more expensive, but you’re paying for hours upon hours of R&D, in addition to build materials and rather impressive performance gains. For most people, paying real money for headers is out of the question, except for the naturally-aspirated purists. If you’re serious about making good old naturally-aspirated power in your IS300, then you’re going to have to look beyond the price. Megan Racing and OBX headers just won’t cut it.
Note: If you plan on installing catless headers, you will need an o2 simulator or delete. Spacers and foulers are the cheap way to solve the issue, and they are hit-or-miss. If you’ve been listening long enough and you understand that cheap headers won’t cut it, why even bother trying the cheap route to resolve your Check Engine Light?