[QUOTE=longnights;5095059]So, you're new to the site (or at least to modifying you're IS300) and you want more power, but want to keep the drivability and reliability of a naturally aspirated IS. Here are some suggestions to get you started, be forewarned that there are many different opinions on many of these parts. This thread will cover a couple different scenarios, follow the one that best fits the image you want to fill:
1. I want more power, enough to feel, but I want to stay quiet and have no headaches like CELs or black soot coming from the exhaust.
2. I want a lot more power, I still donít want any headaches like CELs and I still want to keep the car fairly quiet.
3. I want as much horsepower as I can economically get, I still donít want CELs, but noise and tuning are okay.
Joe-Z (or PLP SFI, though this is no longer manufactured, they still sometimes pop up for sale in the member sale/trade forum) upgraded intake pipe and a drop-in air filter (consult the IS300 Bolt on Upgrades Catalogue Sticky)
$99 plus $8 shipping from the my.is store
30 minutes, easy enough for anyone to install on their own car
Both the Joe-Z and PLP retain the stock airbox, they merely replace the pipe from the airbox to the throttle body. The OEM pipe has a resonator and baffles which quiet the intake down some but also slows and disrupts airflow through the pipe, limiting the amount of air available for combustion in the engine. Both of these upgraded pipes are straight through and make for less resistance. Retaining the stock airbox does two things; it keeps the intake fairly quiet and it also makes the modification less noticeable to anyone inspecting your car, especially if you stick with the anodized black version (call it CARB unnoticeable instead of legal). The aftermarket drop-in air filter will also improve air-flow. There are a couple types of these, foam and cotton generally, many of the cotton ones are cleanable and re-oilable. Personally, I recommend avoiding the re-oilable ones as excess oil can damage the mass airflow sensor (MAF) in the intake pipe.
TurboEast/OBX/Toyomoto/Alphaworks/Megan Racing/any ebay header, there are only two designs for all these headers, long runner and short runner, they are basically one-offs of each other, many of them actually made by the same company. Make sure the header comes with nuts, bolts and gaskets. You will also need an o2 simulator to trick the ECU into not realizing you removed two catalytic converters
Last header I saw on ebay was $190 plus shipping (new)
O2 simulators are usually ~$30-40
If you arenít afraid to work on your car, get a friend and expect to spend 3-4 hours doing this, it is fairly easily done with a lift, though many do without one. The o2 simulator will require that you cut and cut and solder some wires. If you donít do it yourself, expect to pay $200 to $300 to have a shop install the header for you.
These are all pretty generic headers and there arenít many differences between them. Theoretically, the short runner designs will make more power down low and not as much up high in the RPM range while long runner designs will gain more up high, though there isnít anything to prove that among these headers. The o2 simulator is required because there are 4 sensors in the exhaust, 3 on the header and 1 on the y-pipe that measure oxygen and fuel levels in your exhaust to determine if your catalytic converters are properly functioning, two are ahead of the cats, then the one after them should detect lower levels because of the upstream cats. Because we are removing the cats, this will not be true, however, the o2 simulator will imitate the ďeverything is fineĒ signal from the o2 sensors so the ECU doesnít know there is a problem.
Keep the stock one!
The stock y pipe will put some restriction in the exhaust which will keep some backpressure around to make more torque. An exhaust can actually be not restrictive enough; some of the people on the forum have actually lost power when they added a y-pipe to their exhaust system. Keeping the stock y-pipe will also keep the last of the stock catalytic converters, this will clean up the exhaust so you donít get the black soot commonly seen on the rear bumpers of cars without catalytic converters. All of this together will keep down the volume of your system as well.
Whatever you want, all of the exhausts for the IS make about the same gains whether they are cat-back or axle-back. Pick your exhaust out based on the sound you like, sound is a subjective property, what one person likes, another may find loud and ďricey.Ē Once again, check the IS300 Bolt-on Upgrades Catalogue sticky for ideas, it lists 8 cat-back and 9 axle-back systems.
Depending on the exhaust you choose, anywhere between $300 and $600, people switch exhausts like crazy, check the member sale/trade forum for some deals
Also easily installed, get a jack, a 14mm wrench (longer the better) and 30 minutes to put on a new exhaust (a penetrating lubricant like PB blaster might also be necessary if your bolts are stuck).
Whether you decide on cat-back or axle-back, the rear section of the exhaust does more for the sound of your car than it does for power, most make 5-8 horsepower, but every exhaust sounds different. In my opinion, you canít go wrong with a Tanabe, Borla, or L-Tuned, these are all on the quieter end of the spectrum and all produce a deep sound, though the Borla and L-Tuned are both discontinued and very difficult to find.
Results will depend on whether your car is an automatic or manual as well as the dyno but should be in the 185 to 195rwhp range, lower end for automatics, higher end for manuals. Stock autos should dyno in the 170-175 range and manuals should dyno in the 180-185 range, so you are looking at 15hp or so worth of gains at the wheels.
Joe-Z intake - $107
Whatever header you get - ~$210 depending on shipping
O2 sensor - $40
Exhaust - $300-$600
Self installed Ė $657 to $957
Shop installed - $857 to $1257
im probably just not understanding this.
but doesnt the 300 come with 215 sotck horsepower?
if you could..just explain so i understand?