Front pipe replaced.

[muncher]

Hi All. Thought I would share what I have had done recently. Had a Rage front pipe put on my V8 STI. It replaces the stock front pipe/cat converter. The result has amazed me. The turbo now spools way quicker. Before max boost was approx. 18psi. Now , with no other mod other than the pipe, is approx. 23psi. This mod has given a better low down response which I was hoping for. MPG I think is about the same or so it seems to me. Exhaust note is slightly louder but not by much. You can now here the turbo spooling more than you could before. Sounds like a jet engine powering up.

If anyone was thinking of doing this mod then in my case this was a huge success.

[loner]

You might want to get an after market boost controller and bring the boost back down to a reasonable level.

I'm assuming you haven't got a tune for that boost level.

[Guest]

Normally removing a restriction like a cat means a drop in boost. In your case with no change in boost control its running settings for 18psi so it now overshoots and hits epic boost. Run it on wastegate pressure until you tune the boost map.

[loner]

Really? I've always experienced the opposite... less restriction means more flow which means more boost.

[muncher]

So would running this higher boost cause me problems down the track. It runs great like this, power is awesome.

[Guest]

 loner said:

Really? I've always experienced the opposite... less restriction means more flow which means more boost.

Boost is just restriction. So if you have a collapsed muffler boost goes up but power doesnt. Hard to explain.

[Guest]

 muncher said:

So would running this higher boost cause me problems down the track. It runs great like this, power is awesome.

Yep best get a 3 port solenoid then swing by dtech for a tune.

[loner]

 evowrx said:

Boost is just restriction. So if you have a collapsed muffler boost goes up but power doesnt. Hard to explain.

Who said anything about power? You said that increasing the flow through the

exhaust reduced boost. Please explain how this is possible. I'm not calling

you a liar, but it doesn't make sense to me logically or from experience.

edit: I can see how increased flow can reduce the need for boost to attain a

certain power level... but to me if the exhaust turbine is spinning faster

due to more gas flowing through it, then it's going to make more boost.

Edited March 25, 2016 by loner

[Guest]

 loner said:

Who said anything about power? You said that increasing the flow through the exhaust reduced boost. Please explain

how this is possible. I'm not calling you a liar, but it doesn't make sense to me logically or from experience.

Without boost control. With boost control you end up with more boost as ecu works on a duty cycle. So the map that worked for 18psi doesnt work when you improve the airflow.

[slystiguy]

 muncher said:

So would running this higher boost cause me problems down the track. It runs great like this, power is awesome.

unless you've got a wideband and knock light installed I wouldn't risk it (esp top end). You'll probably find your tune is leaning out. Not safe unless you know what afr's are doing. Would be a shame to pop a nice engine for the sakes of a few psi of boost/spending $800 on a tune. Be smart get it checked out before it's too late. Or get a boost tap and restrict it back to factory boost until you can get tuned.

[Guest]

Just run a line directly from the compressor housing to the actuator till you get a tune.

[Guest]

 loner said:

Really? I've always experienced the opposite... less restriction means more flow which means more boost.

More flow doesnt mean more boost. Boost is a measure of restriction. That is why everybody wants to increase v/e and reduce restrictions like small exhausts. If it flows easier/less retriction you run less boost for more power/safer engine.

On a factory car like a v6 sti running 16psi if you just change exhaust to a 3" tb it will boost 18psi or so. This has nothing to do with more flow making more boost it is the ecu being untuned and using the settings required to maintain 16psi which are incorrect for the less restrictive setup it now has. Goes for any duty cycle based boost control.

Until you understand what boost is nothing makes sense. All it is is restriction through the engine not directly relative to power/torque/flow etc.

[hunter951]

23psi + no tune = f&*ked engine in no time

[loner]

 evowrx said:

More flow doesnt mean more boost. Boost is a measure of restriction. That is why everybody wants to increase v/e and reduce restrictions like small exhausts. If it flows easier/less retriction you run less boost for more power/safer engine.

On a factory car like a v6 sti running 16psi if you just change exhaust to a 3" tb it will boost 18psi or so. This has nothing to do with more flow making more boost it is the ecu being untuned and using the settings required to maintain 16psi which are incorrect for the less restrictive setup it now has. Goes for any duty cycle based boost control.

Until you understand what boost is nothing makes sense. All it is is restriction through the engine not directly relative to power/torque/flow etc.

Hmm, not that it matters... but the fact is that if you put a catless downpipe on a WRX it makes more boost and needs sorting out. End of story.

You're whole, "usually reducing restriction reduces boost" statement was quite random and unnecessary... and not even correct given the context.

Edited March 26, 2016 by loner

[Guest]

Its all very related if you care about understanding why its happening and why you want to sort it. If you dont care the simple fb answer is its fine just keep boosting it g.

[loner]

 evowrx said:

Its all very related if you care about understanding why its happening and why you want to sort it. If you dont care the simple fb answer is its fine just keep boosting it g.

I'm not the OP... and it's not that I think the simple answer is better... I'm just saying that your statement was wrong in the

context of a "normal" turbo car... as they all have boost control.

[muncher]

I am not sure if my gauge reads true. It seems like the boost level was reading high to start with. I did a bit of reading before replacing front pipe. Found this.

Due to emission standards, Subaru included a

catalytic converter

in the uppipe on the 2.0L WRXs ('02-'05). This is an issue because the

catalytic converter

has been known to break apart and subsequently get sucked into the turbo. This has since been fixed on the 2.5L vehicles.

If the "preventative maintenance" aspect doesn't entice you to do this modification, the power benefits should. You should see an increase in spool time by 500RPM (or more), and ~10hp gain. The best part about these gains is that there is no tune required to see the benefits like with some other power modifications.

A few "horror shots" showing the carnage of someone whose uppipe let go (pictures from a Nasioc

thread

by Davenow):

This can happen at stock power levels (a local guy here just went through this ordeal when his stock '04 WRX uppipe let go and grenaded his turbo), and the risk increases exponentially as you modify the vehicle. Any "StageII" package, even if not specified in the map notes, should include this modification.

To remedy this, it is imperative that you remove the

catalytic converter

from the uppipe as soon as possible. You have three options:

1) Gut the OEM one

2) Purchase an OEM STi or '06/'07 WRX uppipe (these were all catless from the factory)

3) Purchase an aftermarket uppipe

Gutting the OEM uppipe is the cheapest option. This only requires hardware not readily available to you, and new gaskets (~$50 from your local dealership). I have helped many people gut their OEM uppipe. If you don't have access to a vice to hold the uppipe, having a second set of hands will help, but isn't required (I've done them by myself). I've had good results using a long drill bit, a long flat-head screwdriver, a rubber mallet, some built-up aggression, and a 6-pack to get the majority of the cat material out. Once it's complete, I take a drill bit with a wire brush to do a final cleanup (you don't want to be lazy here) - a good flashlight (or even a snakelight) will help you see any spots you may have missed. Make sure you do this in a well-ventilated area (I've always done this outside), and use some form of respiratory protection (the cheap paper face masks are pretty cheap and do the job). The entire process usually takes me about an hour to complete being thorough (not accounting for removal/installation if necessary). Most people I have helped have purchased a second uppipe to allow us to gut one while having no downtime on their vehicle (they can then install the gutted one at their leisure), and sell theirs for the same price they paid. There is some belief that the hallowed out

catalytic converter

creates some turbulence, which would make this the least effective method.

Purchasing an OEM 2.5L uppipe saves you the hassle of gutting and purchasing any tools you do not have (or can't borrow). These can usually be found for ~$75 used, and also requires new gaskets. There is no cat to hallow out, so this should theoretically offer better airflow compared to a gutted OEM uppipe.

Purchasing an aftermarket uppipe is arguably the best option, considering the funds are available. A quality uppipe should run in the $150-250 range (figure ~$50 less if purchased used), plus the cost of new gaskets. Aftermarket uppipes tend to offer better airflow compared to OEM 2.5L ones (see TiC's thread

here

). With an aftermarket uppipe, there are two types: solid and flex. The OEM 2.5L uppipe came with a flex section, so it's my opinion that it was done for a reason, and you should stick with a flex section uppipe.

Subaru included an EGT sensor in the OEM 2.0L uppipes as a precautionary measure to check the healthiness of the catalytic converter. Since you're going to be removing the cat, it is no longer necessary to run this (EGT should be measured in the

exhaust

manifold for accurate readings anyway). Reusing the stock EGT sensor is only going to run the risk of that breaking off and getting sucked into the turbo, causing damage. If the uppipe you're installing has an EGT bung, then use a bolt (M12 x 1.25) to plug the hole.

There is a CEL associated with this modification that needs to be taken care of: P0546 Exhaust Gas Temperature Sensor Circuit Malfunction (High Input). This is often disabled with "StageII" maps, but if you're running the stock map, you'll need to do the "2.2 KOhm resistor mod". You can buy these at any electronics store (e.g., RadioShack), and should cost you ~$1. This resistor gets placed in the bottom connector just in front of the passenger strut tower.

On the topic of "

eBay

" uppipes, I would recommend against them. The quality of materials used is generally lower than of a reputable company, the gaskets supplied tend to be garbage, and the fitment isn't always great. You are far better off gutting your OEM uppipe if you cannot afford to purchase an OEM 2.5L or quality aftermarket one. One issue with material quality with "

eBay

" uppipes is the flex sections used, which have been known to break apart. Another set of pictures taken from Davenow (see

post

) showing a popular "eBay" brand uppipe that is sold by many vendors:

This post was written in hopes to make it easier for members to find information (I got tired of searching for Dave's thread). If anyone has any comments/suggestions for improving this, please feel free.

[Guest]

They are talking about the up pipe not down pipe dude.

[yoUaReABUS]

I did a whole bunch of research on down pipes and up pipes when I was buying my Turbo Back Exhaust.

The USDM wrx's have cats in the up and down pipes for their emissions, which was removed on the 06+ sti

I know in the JDM models they didn't have cats in the up pipes. At least for my v7 sti they don't.

When I did my TBE I didn't notice any power gains, apart from the noise, I think I may have actually lost power. That's when a tune really woke it up. Anything that changes the characteristics of the exhaust gases the ECU needs to know how to handle that, as is looking for back pressure leaving the turbo.

Edited April 14, 2016 by yoUaReABUS