Grimmspeed Divorced Downpipe 04 Wrx Hi Flo Cat Review

Downpipe FAQ

The primary purpose of an aftermarket downpipe is to remove or supercede the stock catalytic converter with a better flowing unit. It also increases the frazzle diameter for improve flow.

HP proceeds is 15-20HP. This figure is highly debated equally different manufacturers apply different dynos with different cars with different levels of mods. It also varies because some downpipes use one high flow cat, while others are catless and actually extend far enough back to eliminate the 3rd cat besides.

I have an 06/07 WRX, is the downpipe the aforementioned? No. The 06/07 WRX has a unique exhaust in that it's downpipe is both the downpipe and catpipe sections of the "older" exhaust. This means you must use a "long" downpipe to commodities up to the residual of your frazzle organisation. A full TBE will fit fine, but when replacing only the downpipe, you must utilize a long downpipe.

I have an 08+ WRX, is the downpipe the same? No. The 08+ WRX has a unique exhaust in that it'due south downpipe is the same, fitment wise, equally the Legacy GT. So if you accept i of these models, you must ensure you land your model/year to your vendor or specifically asking the "Legacy GT downpipe" for your machine in social club to assure proper fitment.

Which manufacturer is all-time? This topic is highly debated. In that location take been no reported consistent "bad" downpipes on the marketplace. Obviously, there may accept been bad pipes sold, but non enough to written report as "bad" overall.

Who articles downpipes? The NASIOC user fliz has kindly started a downpipe chart that lists all the downpipe manufacturers and lots of comparative data. fliz'due south downpipe chart.

What downpipe metal material is best? Downpipes are made from mild steel and stainless steel (304 & 321). At that place is no irrefutable evidence that 1 material is ameliorate than the other. Plainly, corrosion levels are higher with mild steel (coated or otherwise). Article on frazzle materials.

Which downpipe construction method is best? Downpipes have 4 main construction methods:
1. Blank plate: Identical to stock construction with the wastegate portion completely covered.
2. Bellmouth: Completely open pattern.
3. Split bellmouth: Like to bellmouth only with a divider inserted to divide the wastegate.
4. Divorced or Twin Dump: Separate frazzle and wastegate pipe that connect further downstream.

At that place is no irrefutable testify that one pattern is amend than the other. The thought process is that the greater the separation in that location is betwixt the wastegate gases and exhaust gases, the smoother the overall frazzle flow.

Which downpipe construction method is to the lowest degree expensive? Generally, the blank plate design is the least expensive. The other designs, depending on manufacturer, are all around the aforementioned general price range.

Can I gut my downpipe like people exercise their uppipe? Yes. Scoobymods.com directions. Others have used a 2 pes department of bent rebar and a hammer and reported the de-catting process takes 30 minutes total if the scoobymods directions seem too labor intensive.

Can I use an STi downpipe? Yes. At that place is very little difference betwixt the STi and WRX downpipes though. Using the STi downpipe is fine, but do not consider it a significant upgrade. Differences in HP between the ii are likely to be very tiny (5HP or less is a estimate) and non worthwhile.

What other differences are there with downpipes? The other differences are as follows:
1. High menstruum cat or catless.
2. Overall pipe diameter. Sizes range from 2.5, 3.0, and 3.v inches. three.0 and 3.five are generally just necessary for higher (300-400+ HP) applications.
3. Length of downpipe, some are stock length and others are longer to remove the 3rd true cat.
4. Propietary length. Some take manufacturers have unique lengths or are JDM length which requires manufacturer specific length or JDM specific length components after the downpipe.
5. Flanges. Some are manufactured with a donut gasket and some with a flat flange, the end user needs to research what bolts up to what earlier purchasing.

Which downpipe has the best gains? In that location is no irrefutable evidence that whatever downpipe has better gains than another. The consensus, if in that location is one, is they are all within 5HP or less, proceeds wise, of each other.

Are in that location any downsides to downpipes? There take not been significant amounts of problems with downpipes. At that place take been some reports of wastegate issues with divide bellmouth and divorced or twin dump downpipes. These type of downpipes have a "splitter piece" that juts into the turbo to separate the exhaust from the wastegate. Sometimes this piece is too long and requires some slight cutting or grinding for a perfect fit. The telltale sign of this occurrence is less than full boost or irratic boost upon installation. Every bit with any aftermarket part, even "perfect" ones, sometimes you run into a rogue issue. From research, this is not a widespread issue at all, only an informational if this situation should occur.

Where exercise I purchase a downpipe? Every Subaru/Import functioning shop sells downpipes. For purchasing, support your local economy or the NASIOC Vendors.

What is some good background information nigh exhaust piping fitment?
By and large speaking, there are 2 types of catbacks:
Blazon 1: It has a sliding flange designed to bolt up to the stock downpipe.
Type 2: It has a flat flange designed to bolt up to iii" downpipes.

By and large speaking, there are 2 types of downpipes:
Blazon ane: It is designed to bolt up to the stock catback and other type one catbacks.
Type 2: Information technology is designed to bolt up to only type 2 catbacks.

Blazon 1 catbacks do non commodities upward well to type 2 downpipes, and type 2 catbacks practise not bolt up well to blazon 1 downpipes.
Type 1 catbacks and downpipes taper to two.5" where they meet.
Type 2 catbacks and downpipes are full 3".
Type 2 downpipes are unremarkably less expensive than blazon 1 downpipes.
Blazon 1 and 2 catbacks are relatively like in price.

All 2.5" catbacks are type 1.
Some three" catbacks are blazon 1, and some are type 2.

What questions should I ask of the retailer or manufacturer before purchasing?
1. Volition this unit of measurement mate upwardly to the remainder of my exhaust? Some downpipes volition fit the stock exhaust, or must be fitted to a larger frazzle.
2. Will this unit throw a CEL? Some practice, some don't, so find out beforehand.
iii. Does it come with new gaskets? It is always a adept thought to replace exhaust gaskets.
4. Does it come up with a CEL fix if needed and is it the right one? In the case of the electric fix, at that place are 2 unique fixes, i for the 02/03 and 1 for the 04. The 05+ does non currently have an electrical fix.

How difficult is it to install a downpipe? Allow effectually one-two hours for install time. Professional installation, depending on your area, is around $75. This is one vehicle modification that is very simple and can be successfully accomplished past even the greenest shade tree mechanic.

What is that prophylactic hose on the lower rear firewall that is near my downpipe? That is the Air-conditioning drain line. Movement it out of the way of your new downpipe past moving the mounting tab, loosely nil tieing it out of the manner, or past trimming it. Do not nix tie it closed as it needs to drain and practice not trim is flush or nigh flush with the firewall as it will popular inside the automobile and drain into the passenger bicycle well. Replacement of this bleed line is said to exist a real bear, so ensure you do not over trim it. People have not taken steps with this and information technology has melted on it'due south own due to the downpipe heat, but there'due south no reports of catastrophic burn as a result. This does non requite you license to but let it "cook to fit" though, but a comment for people that have missed the fix and have noticed a melted tube.

How exercise I install a downpipe? Refer to the downpipe manufacturer'due south instructions. For downpipes without instructions, below are links to some of the improve known downpipe installation instructions:
TurboXS'south Instructions
Perrin's instructions
Scoobymods.com instructions
Scoobymods.com instructions
Cobb instructions

Proceed in heed that the short black rubber hose on the passenger side side of your fire wall is the Air-conditioning drain line. It'due south best to ensure that it is routed away from your new downpipe to ensure it properly drains and does non cook onto your downpipe. It tin can drip onto your downpipe and this causes no reported problems if y'all choose to cut information technology short and allow information technology to drain on the downpipe itself. Though not the best route, this is mentioned as a possibility.

What about ceramic or other heat wrap coating? Though in that location are pros and cons to heat retention treatments with exhaust components, the general consensus with headers is that heat retention benefits outweigh the liabilities.
Pros:
Increased estrus retention, which is beneficial for exhaust flow.
Reduces underhood temps, which decreases IC heatsoak.
Cons:
Boosted expense.
Additional lead fourth dimension, in the instance of coatings.
Increased heat retention, which in some cases, tin accelerate metal fatigue, especially at weld joints.
No proven HP increase.
If you plan on using a blanket, ensure you are enlightened of what impact this will have on your header warranty if applicative. Coating or wrapping your header can void exhaust component warranties. If using a ceramic-type coating, ensure information technology'due south working rut range is above the known EGT. EGTs tin can be as high as 1400-1600 degrees in the extremes. Some normal coatings are non rated to this temperature level.

What types of ceramic or other heat wrap coating are available? The two most popular manufacturers of heat wrap are Thermo Tec and DEi. The two about popular coating manufacturers are Jet Hot and Beau Tech Coatings. Wrapping is a DIY project with a shorter life span than the professional only coating with a longer life span.

Excellent coating thread
.pdf file on coatings
Auto Craft magazine's testing of Jet Hot

What is the CEL fix? It stops the rear CEL code P0420 Goad System Efficiency Below Threshold from appearing, this lawmaking being caused by the lack of a catalytic converter in the frazzle. This is ordinarily fixed with a Pony Limited MIL Eliminator (no longer in business), Casper Electronics set, or Perrin Functioning fix. The 05+ does non currently take an electrical gear up. Another fix is the mechanical gear up, which works on all models. ***Notation*** In that location are two CEL fixes for the WRX, the other one is the two.2 KOhm 1/2 watt resistor. Information technology is used to gainsay the CEL lawmaking P0546 = Exhaust Gas Temperature Sensor Circuit Malfunction (High Input) in the

uppipe

. This notice, though not important to this thread, acknowledges at that place are two "CEL fixes" and defines them individually to avoid possible defoliation.

Many aftermarket engine management systems tin can besides exist used to forbid the CEL calorie-free from showing up.

Which is the best CEL gear up, mechanical or electric? Both work fine, though personnel living in states with OBDII testing prefer the mechanical fix. The reason for this is during state mandated OBDII testing, the electrical fix can show up as a malfunctioning sensor. For some states, this ane malfunctioning sensor is fine, for others, y'all will have to fix information technology and return. In the end, the mechanical set is cheaper and easier for nearly users.

Can I drive around with a P0420? Yes. This is not a code that will throw your auto into limp mode, and so yous tin drive unremarkably with it until you lot become a CEL fix. It'southward never wise to practice so though every bit a CEL is hands seen by police who may then do a "safe inspection" as well as crusade problems during any local emissions testing.

Exercise I demand engine management with a downpipe? For 02/03 WRX and 04-06 STI users, no. For 04+ WRX and 07+ STI users, information technology's pretty much a requirement equally the open loop/closed loop fueling issue mandated by the EPA causes long term reliability bug with using a downpipe and no tuning. For STI users, the STI was the one exception manufacturers are allowed to have, but it's a wise move regardless as the STI and 06+ WRX users have a good risk of heave pitter-patter occuring with downpipe utilize. Tuning can ease this issue, but the cause/issue/cure of heave creep tin exist researched via this link.

Should I reset my ECU after this mod? Information technology is never a bad idea to perform an ECU reset after a mod. The traditional route is to disconnect the negative battery concluding, press the brake pedal for a few seconds to bleed the arrangement of accuse, and reattach. Some use the more advanced Vishnu Reset.

What well-nigh emissions issues similar emissions tests and legality? Using a catless downpipe is a violation of section 203 of the Make clean Air Deed. Each state has statutes that comprehend this subject likewise. Every bit far as passing country emissions tests, every bit long as yous yet have 1 true cat in your organisation, you should be fine unless you run into a sharp-eyed and knowledgeable inspector who knows there should be two in the main exhaust. The exhaust should be properly warmed prior to any testing to ensure it is operating efficiently. Another smart motion is to observe someone in your local area with the same gear up to compare notes. Seek out locals via the NASIOC Capacity or NASIOC Regional Areas. A overnice commodity on cat testing tin be establish here.

Editors Note

This post was created because I wasn't able to find a adept downpipe FAQ. I came upwards with the text based on LOTS of searching here. Information technology was also created to exist intentionally brand neutral so that information technology serves as a stepping stone for further research. Upon reading this you should have an idea of what type of downpipe best suits your needs. The manufacturer is up to you.

If you discover an mistake in this FAQ, please PM me with factual details and I volition update this post. Responses such every bit, "I have XXX's downpipe and it's great!" or "Xxx's downpipe leaked subsequently 1 month" are not appreciated hither, that is what the Machine Parts Review Forum is for.

leonardfroverce.blogspot.com

Source: https://forums.nasioc.com/forums/showthread.php?t=445812

Share this post