OK, the thing is im only planning on getting an up/down pipe + exhaust put on my car. I read something that if your not gonna take your car past 280hp then you should get a 2.5 in exhaust? anybody know this kinda stuff...

 

if u still have the stock turbo 2.5" piping is enough for the dp and the catback. For the uppipe u want the smallest diameter piping possible. Something less than 2" is sufficient.

 

what he said...and get it reflashed with cobb accessport for even greater gains

 

what if am gonna run a 2.75'' or maybe 3" w/silencer since it causes a restriction and narrows the exhaust flow..... ? Would that work? B-cuz i MAY get some sort of engine management in the future beacuse I know i will want more powerin the future if i can afford it.....

 

Imma disagree. You want 3" turboback. Uppipes are pretty much all teh same. You want a nice 3" downpipe and 3" exhaust. ESPECIALLY if you getting a catted downpipe, which is what I recommend to save all the birdies and the flowers...

 

I am by no means an expert but I would like to ask you why would u need 3 inch piping turboback for a stock turbo wrx? I talked to cKevin at his shop and he told me there's no need for 3" piping for such a small turbo. His coworker's forester has a full zerosports exhaust system which is like 2.7" piping on the turboback (downpipe is a catted one) mated to a twin scroll turbo. Zerosports uppipe, don't recall the diameter but it's less than 2 inches, and is virtually lag free. Boost comes on at like 2k rpms. There must be a reason why 2.7" piping was favored over 3" piping.

But getting back to the subject, I don't see any reason to use 3" piping for a stock turbo wrx. Correct me if I'm wrong, but with 3" piping, your top end and hp may improve, but you sacrifice some torque and your low end.

 

I will give you more than 1 reason. It's very simple. But first, let me tell you something.

If a company makes or sells product A, they will preach you product A, they will tell you it's the best. They will do all they can to prove to you that it is the best. They are not liying to you. They just have a biased opinion. And yes, Zero Sports products are 75mm. They have few 80mm exhaust systems, but those are only available for GC8's. The only way to find out what is better, is to actually try everything yourself on your car and be in control of the environment. I have dont that with over 10 different exhaust systems and 6 different turbo combinations. All that on my car. That is where my advice comes from. Aside from that, not only do I work for a company that sells exhausts, I am also a user just like you. You cannot say that my opinion is biased. ESPECIALLY since I did not name any particular brand names.

3" is optimal for WRX. Engine diplacement and its volumetric efficiency calls for high flow exhaust system. Let alone the fact that you DON'T want any backpressure AFTER the turbo.

Also, there are a lot more options in 3". The only 2.5" systems are available from those companies that market their products towards people who just want a different exhaust note and minimal performance.

Catted 2.5 downpipe is useless. Might as well just take the turbo off completely and Flinstone your *** around.

Even if I agree that gain from going extra 0.5" in your piping is not THAT big, there is no WAY you will disagree with me, that 3" turbo back exhaust system will insure that you will have adequate exhaust system once the turbo gets upgraded.

And about your last statement about low end loss. EVEN if I agree with you (which I don't in this case, but I will say yes for the sake of conversation), you contradict yourself, sort of. Why would you care about loosing low end on a puny little turbo? Stock turbo has NO top end, so isn't that what you want to gain?

3" more top end at low end sacrifice is not true 99% of the time on turbo cars. We are not talking NA here.

Proper statement is that 2.5" will choke your turbo and you will NOT GAIN as much top end as YOU COULD if your system was flowing good e.g 3.0".

If anyone wants to agrue my statement with me, I will be happy to discuss this even further...

 

wow, thanks for the info. I think im gomma buy a used Tanabe Ultra... it's 2.75'' but i will have the helix up and catted down if u care to lend more info upon that..... peace

 

Tanabe Ultra Medelion is a great system. Very very light and priced great too. It is one of 3 best sounding systems too, in my opinion. And also, it is very straight through, which is great too. Very similar to 5Zigen Miracle Fireball, which is what I currently use.

However, it is 80mm, which is actually a little bit bigger than 3". So, imma love it even more if you get it, haha.

Helix products for Subaru's are great. Fit very well and the quality is great too. And, being cattted, Helix dp actually flows very very well too.

So, you get my full support on your choice of parts.

I am sure, that for you, knowign that you can get an upgraded turbo and not worry about your exhaust system will be a + to you too like I said.

 

Like I said, I'm no expert, but this is what Kevin told me. I most likely phrased it wrong. About being biased or not, Kevin was also a user so it's not like he is biased towards a particular brand (well he may be biased to anything jdm lol ). As you may recall, he used to own a "400 hp" wrx (with nothing but jdm parts) before he traded it in for a G35. Now most people have said that the HKS downpipe was crap and from all the stories I've read on the forums, I started to believe it too. But he used it on his "400 hp" wrx and had no problems with it whatsoever.


Yes, but your car is heavily modified along with a bigger turbo. I'm merely talking about a lightly modded, stock turbo wrx. In this case, a turboback along with uppipe and engine management. I still don't see any significant advantage of going with 3" piping vs 2.5" piping (or in Zerosport's case approx 2.7-2.9").

Because low end torque gives you more useable power when it comes to daily driving. Perhaps I'm just talking out of my ***, but low to midrange power is also where the majority of the time is spent on daily driving, not the top end.


I have to disagree with you on this. When I bought the helix catted downpipe and had it installed, Kevin showed me how bad the fitment was with the Helix. I saw it with my own eyes and there was literally a good 1/2 inch or more gap between the downpipe and the turbo. He had to force them together to get it to fit, which creates unnecessary tension on the turbo.

 

HKS downpipe is crap comparing pretty much anything out there. Small diameter, no divorced wastegate, mild steel construction. That downpipe got nothing JDM in it but the name. HKS does not sell that downpipe in Japan IIRC. And, I bet you if that 400hp WRX had a nice 3" downpipe with uber wastegate passage design, it would have made more power.

I am not saying Kevin is biased. I am just giving you a general adive when it comes to taking "shop's advice". Talk to some other shops. Talk to people. Don't just swallow what one person tells you regardless who he or she is. That's why we have i-Club after all.

About Helix fitment. I should have been more careful. I have not installed a single catted downpipe. I have seen it and have seen it being dynoed. I am not sure on its fitment. Catless downpipes I have not had any problems with. But then again, it is not JDM.

For downpipes right now, if I had to get one for MY car, I would get CUSCO or Tanabe. HKS downpipe, I would buy for fun, cut it in 6 different peices, melt it in a big ball and throw it off the GG bridge. The only good thing about HKS downpipe is its price. If you just want "something" and you don't care about getting the most out of your car, then HKS downpipe is ok. And, it fits good. For anyone interested in maximum performance, HKS will not do.

 

Kevin is biased towards anything jdm, but his advice to me isn't just to sell me parts. His shop is just a service shop and does not represent or market any particular brand of products. The only time he recommended me a particular brand was when I asked him what he recommends lol.

Now if I were to go to another shop that does sell products of a particular brand, then of course they will say anything to get you to buy that certain part that you need.

I could go and talk to people, but how many of them really really know what they're talking about? How many times have you read on the forums (not just here, but anywhere) where it seems like a lot of the members are misinformed? Most people on the boards educate themselves (like I do) by reading the stuff that's posted. But if somebody posts inaccurate advice and everybody starts believing in it, then there really isn't any useful advice to follow.

But like many others in the Bay Area have experienced before, Kevin really knows his stuff and he has the experience to back it up. That is why I trust his advice.

 

Forget about Kevin, hehe.

Someone asked for advice on DP. I said 3 inch and you challenged my advice based on someone elses advice. Regardless who it is. I gave you reasons why I would go 3" and you have said nothing besides "person X said 2.5 is better...".

How about this. I will start a poll of 2.5 vs 3 inch downpipes and we'll see how it turns out.

 

gotta include the hp range for the two or it's pointless ;for the poll.... and what could i do to help low end torque loss, im guessing engin managment is the best way but is there cheaper fixes?

 

You are not going to loost anything you can notice. Don't worry.

Here are the results so far...

https://www.i-club.com/forums/engine-power-ej20t-pre-2006-wrx-jdm-60/downpipe-better-your-opinion-133972/

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Another good example of similar misconception would be the notorious VF22 turbo lag. While everyone typically says that it lags, I have a dynograph to prove that when properly tuned, it actually spools up the same as the stock TD04 turbo. Hell, you can all see it for youself. Sport Compact Car from October of 2001. My car was dynoed there along with a stocker that provided a baseline.