I'm looking at getting an exhaust for my '03 WRX. My WRX came with the dual output exhaust and i was wondering how much an exhaust boosts the power. I have heard that the muffler on the WRX is the most constricting part of the whole exhaust system so you get "a lot of bang for the buck" even if you only get an axle back exhaust. Is this true? Any advice?

 

dyno after dyno has shown that the stock muffler is very constrictive.
Replacing the muffler will allow the flow to move better. Do not expext gobs of power from just doing this mod.
an up pipe, boost controller, and your muffler mod will get your ride off to a good start.

chris

 

Voice of experience here.... I had a complete turbo back system installed in my WRX. It certainly is not worth the $$ spent for the power gains. I never had it dynoed (more money) but I'd guess it gave me .2-.3 seconds off the 1/4 mile if that much. After quite some time I finally got tired of the louder exhaust (my wife and friends were tired of it fom the start), It also caused a small loss of low end torque too! (pre-boost, where you most need it). Also, even the best units will eventually cause a CEL which spells "trouble" with service work and in many places an automatic failure of emissions test when you go for them. I finally had it replaced with the original system (always save those things) before I traded the car. I'd advise (even if you did not ask) to save your $800 to $1400 and just enjoy driving your fine stock WRX. It's fast as hell anyway

 

I think his question is very straight forward. The question is how much power will the exhaust make?

I say not enough to warrant the cost and the hassle (CELs, warranty issues, driveability, etc.)

Secondly, the TXS claims are, in my experience, misleading and exagerated. I had the TXS Stage II Unichip and a 3" turbo back exhaust. As far as I'm concerned it was not worth the $$ I spent in the products plus the installation and later putting the car back to stock configuration. To each his own, but I question the wisdom and validity of many of these modifications. The main thing to remember is "caveat emptor"

 

hey, if your like me, you want a few things out of your car and the mods you put on it... good looks, long lasting, and performance.

as far as exaust goes...you gota think about all three of these as well as PRICE. how much do u wana spend to add some horses and some *****? well, average axle back muffler is around $450. this is pretty steep. but, if you goin with full headers back your talking like 1500 bucks. you have to think how far u wana go and how LOUD you want your car. and BTW....how many people will really be looking under your car to see what you have? not to many.

I have been thinking about my exaust since the first day i bought my 98 RS.....and since i dont want to spend too much loot on it untill i get my turbo..........cut your muffler off(right before the muffler) and go buy a 20 dollar tip at autozone. saves you a bunch, sounds GOOD and hey you only spent 20 bucks =)

just my 2 cents

 

Go out and get the latest Turbo mag. They did a review of 7 turbo-back exaust systems. That should give you an idea of what to do and if its worth it.

 

With a Turbocharged engine installing a less restrictive exhaust should NOT yeild a loss of low end power unless you did what most people so these days and just "bolt on parts".

With any upgrade you have to truly understand what the upgrade will do to the engine. For example an exhaust will typically allow the engine to breathe better on it's intake and exhaust side. This will speed up the spool time of the turbo, and allow more air to be pumped into the combustion chamber. With more air you will also need more fuel; these two combined with faster turbo spool will yeild more low end torque and more horsepower.

However, this is of course assuming that you are providing the needed fuel to allow the exhaust to give you a benefit. If you are loosing power then you are not providing enough fuel and are causing a lean condition which will eventually destroy your engine.

 

Is ssignorelli really right?

I am planning on adding a uppipe, downpipe and silicone hoses and nothing else to my wrx. Could this really damage the engine?

I want my car to last 200k miles, it seemed to me that these mods were VERY low risk.

 

SSignorelli:

How exactly does an exhaust allow the intake to breathe better? There may be increased airflow... but the restriction from the intake is still there.

I agree that keeping the air/fuel ratio in the proper range is crucial to not leaning out and melting the engine... but the engines have ways of metering incoming air and compensating by increasing fuel.

If there is enough increased airflow by swapping an exhaust to max out the injectors... something is seriously wrong. I don't see how you can say with any certainty that power loss is due to running lean. Maybe running too rich... maybe the exhaust was big enough that the gas expansion actually slows the flow at low rpms... etc

IMHO putting a less restricitive exhaust on your car is probably one of the safest upgrades out there.

Justin

88 Porsche 944 turbo S

 

Justin,

By placing a less restrictive exhaust on an engine, you end up reducing backpressure and turbulence, which will allow more of the exhaust gases to be removed from the cylinder. The more exhaust gases you remove from the cylinder then more fresh air you can pump into the cylinder on the intake stroke.

You are correct that the intake will still have it's own bottle neck in the whole process.

"I agree that keeping the air/fuel ratio in the proper range is crucial to not leaning out and melting the engine... but the engines have ways of metering incoming air and compensating by increasing fuel. "

Beyond having the A/F Ratio in the proper range to keep the engine from premature failure, people tend to forget that there are ideal ratios to actually produce HP/TQ instead of loosing it.

You are also correct in the engine's ability to monitor and compensate for the increased airflow...to a point.

The problem is that every engine built in a production line where profits play a role in staying in business there are compromises. These compromises include the rate at which the production line tools are replaced/recalibrated/re-sharpened. Because of this every engine will have inconsistencies in it's components..such as your fuel injectors, MAP sensor, Fuel pump, computer, and over all cylinder tolerances. All this will play a major role when you bolt on parts to an engine. One engine may get 14hp from an exhaust while the exact same engine in the same type of car will only get 10hp.

People tend to forget about this when "bolting on parts" and then you get people like Yellow Rex, who loose HP because their engine lost HP when they bolted on an exhaust and didn't think check his A/F ratios.

I have grown up with cars around me all my life, it was my dad's passion and I could not help but pick up on it in the 24 years I have been on this earth. The fact is that today's crowd thinks they can buy a part...slap it on their car and BAM! they have more HP/TQ with nothing else to consider. The art of tuning an engine to perfection has been lost in the import scene.

The fact is that Yellow Rex should have kept his ignorant statement to himself unless he was going to back it up by stating what his A/F ratios were when he lost HP/TQ. He's just another "I am gonna bolt on this part that someone told me to and not adjust my engine setup....I am gonna kick some butt now!"...6 months later, he is at a Subaru dealer discussing his warranty and they are showing him the holes in his pistons.

I guess I should have explained my self more clearly in my original post but I was tired acting in a fit of disgust when I read Yellow Rex's post.

–Steve Signorelli

 

Well, my friend, all these parts are sold and marketed as "bolt-on" parts. If they don't works as advertised that is a problem created by the sellers..... Anyway, while in theory the larger exhaust will always help a turbo engine, the reality is somewhat different. As you say, the proper fuel delivery is crucial to the safe and efficient function of the engine. In the case of the WRX, that is a real problem.... For example, what I did was install a full 3" turbo back exhaust *and* purchased a TurboXs Stage II Unichip setup. As some folks found out, the TXS Unichip is a POS and will never work "as advertised". So, the exhaust mod is just so much money poured down the drain for the miniscule increase of performance gained. Now, some folks (not I, since I wised up) installed various sorts of intakes in their WRXs. Most found out that they created more problems than they solved. Unless you are a motorhead with lots of time, skill, patience and a good bit of disposable income, you are much better off spending money on the truely upgradeable part of the system: the driver . I'd say take some performance driving classes or spend some time at the local dragstrip learning to shift better (and using plenty of very high octane gasoline). This is a much better use of your money ... Oh, there is another very good and worthwhile up-grade, and that is good tires and brake pads. I wish I'd kept my money that I spent on all the exhaust and unichip. I would have had more fun with it in other ways

 

Steve, chill on the bs and hostility. My statements are neither ignorant nor out of place. The original poster asked about the wisdom of purchasing an exhaust for his WRX, I told him what I thought and why, plus I backed it up with my experience. You are running your mouth without regard to the facts that you are ignorant of. Your long answers and bragging about how much you know about cars is backing up exactly what I said "don't just put an exhaust in your car, it's a waste of money".

For your information, I've been around for a good number of years and I'm quite familiar with cars. I do a good bit of work on them myself, but I don't pass myself off as an expert mechanic. I'm a car enthusiast. I've owned and modified a number of neat and interesting cars up to and including the 02 WRX which I just traded in on an EVO VIII.

Now, all the stuff you said about tuning cars is fine. What you said about me on the other hand, is inexcusably rude, aggressive, hostile and totally unprovoked. I suggest you grow up a little and try to learn as much about manners as you claim to know about cars.