Arctic_blue I'm really curious as to why you are so afraid of the boost creep issue? Especially here at altitude.
I'm really not trying to be a dick. What you're about to read will really make me sound like one though.
I like you and you've done quite a bit of homework which is very good to a point. I see about 2 hurt engines a month come through because people didn't do their homework. 90% of the tech info you read on the Subaru forums is bullshit. It's deeply frustrating to me when people just parrot what they've read on forums because somebody else didn't do something correctly and had a bad experience. Especially when I spent all that time answering questions in PM's. Going the route you chose was way more expensive, you're going to be giving up quite a bit of power, sacrificing mileage AND turbo life (the cats NEED to go away or EGT's spiral completely out of control and cook turbines). If you are bound and determined to stay with the catted downpipe, at least go with the 3" in the rest of your exhaust.
We have done in excess of 200 stage 2 Subaru's. 95% of them are still happily on the road with 0 issues. Every single one that has experienced a mechanical failure was an owner error. Ranging from "I was in the middle of nowhere and had to put 85 octane in the car" or "I didn't check the oil" or "I accidently went from 5'th to second at 90mph".
I could probably count the number of guys doing the turbo Subaru thing in this country longer than I have on all my fingers and toes. I mean... hell. The reason that Wiseco can make a decent set of pistons for the EJ series engine is because my buddy mark up in Evergreen burned down 5 engines running custom wiseco's before wiseco was able to figure out the correct oil control ring dimensions. I blew up two of my own turbo EJ engines (ovaled the cylinder walls and bent rods) as learning experiences before the WRX was even available in this country. I have blown up about 4 more of my own personal engines since then as experiments. Anybody who claims to be a technical expert without using up quite a few expensive parts is full of shit. Because they haven't been in the game long enough, or haven't pushed the boundaries enough.
Boost creep happens because of a shit tune or a shit downpipe, or both. The factory ECU does all sorts of barometric compensations. As long as these tables are dealt with appropriately, the wastegate duty cycles/fuel trims/timing adjust as needed. A stock STi motor can take 20+ PSi of boost and 350-400whp before reliability becomes questionable. The stock turbo is totally incapable of pushing anywhere near this. Guys who pop motors because of "boost creep" are just blaming a completely phantom problem for bad parts, bad tuning, or their own stupidity.
I never really recommend people go with heavier/lower springs on the stock struts. It ruins the already fragile STi struts with a quickness. The valving is trying to hold back way more fluid pressure due to increased suspension frequencies and the valving just goes to shit. Especially on our wonderful Colorado roads. A stock set of rear STi struts is basically cooked after 60,000 miles of driving here. About 100,000 -> 120,000 for the fronts. A percentage increase in spring rates is about equal to a percentage decrease in strut life.
Like I said... I'm really not trying to be a dick... but I'm a wee bit obsessed with what I do. I just HATE to see people wasting money more than anything in the world. Like... I get pretty irate when I see every other Subaru that MAC has worked on come through the door having spent $700 on a set of completely useless fuel rails. This is also why we haven't really done anything with the Mazdaspeed stuff.... because up until the CPE system and the accessport... nothing you bolted onto those cars would mean didly squat for power, and I'm not about to take somebodies money for something that doesn't work.
I'm just trying to steer you in the direction you will be the happiest with. Not down the path where you spend money you don't have to because of some un-informed post some goofball made on the internet.[/b]
I respect your opinion and professionalism. I will explain to you exactly why boost creep worries me so.... I'm just finishing up paying for a wedding & engagement ring, and to top that off, me & my wife are expecting our first child in September. I understand the vast majority of Stage 2 cars do not experience boost creep, but I also understand that financially I am not in the same boat I was years ago, as I now have a family to support, and it would be extremely difficult for me to budget for a blown EJ257, in the case that I just happened to be one of those unlucky few individuals that run into boost creep issues.
Let me explain, now granted, I'm not a professional, this is my hobby, not a profession, as much as I would like it to be lol. While I'm sure I have not tuned nearly as many cars as you have, as you do it daily, and I'm also sure I've not blown as many motors as you have, as I haven't been afforded the luxury of doing as much "testing" lol. With that said, in the past, I've blown 3 motors, a 4G63, a 3S-GTE & an EJ205. I've had extremely bad luck when it comes to being "one of those unlucky bastards" lol. I've never used anything less than premium fuel, and only fill up at stations I trust. I almost never over rev, and have never accidentally shifting into the wrong gear at a high speed. I'm very conscientious about my oil levels and the type of oil I run, often changing oil when it probably isn't necessary lol. Needless to say, the problems you describe with people blowing motors, have never happened to me, yet, I've still managed to grenade 3 motors.
The last of which was an EJ205... it was ECUtek tuned by a very reputable shop (MZM in Austin), my AFR's were between 10.8-11.2:1 from the onset of boost to redline on 93 octane. The car experienced 0 knock on the dyno. I was running a Walbro pump, to avoid failure with the stock pump, and IIRC, my IDC's weren't over 85%... it was a pretty safe tune. Yet, in the end, I still ended up with a cracked ringland on the cly #4.... which was diagnosed to the FPR hose bleeding off pressure from the intake manifold... since then, I've been paranoid, and have not wanted to push the envelope.
Now, with that said... yes, I'm paranoid... yes, it's probably needless paranoia haha, but that doesn't change the way I feel. I will tell you in dozens of hours of researching specific downpipes, I am yet to find one specific cat-less downpipe that no one has ever experienced boost creep with, to include Cobb, Helix, Invidia, HKS, Perrin, TurboXS and I'm sure several others that just aren't coming to mind right now. I've also done plenty of searching and studying on divorced wastegate vs bellmouth vs split bellmouth vs flat plate, only to find they people have experienced some form of boost creep with all of them.
Now, obviously you state the problem lies with either tuning or a shitty DP... so, I would ask of you, if I did change my mind, what downpipe would you recommend? What style do you prefer to tune, DWG or bellmouth? If, for no fault of my own, if my car was to boost creep, damaged a piston/ring, and it was provable (even though it would be hard to prove...), would your shop be willing to stand behind your tune and pay for a new motor for my car?
You mistake me for an idiot, as I'm perfectly aware of what the cats will do to my EGT's, you also assume I don't know what that can do to a turbo, and think that I would rather make less power for no good reason? I do know this, VF39's cost significantly less than shortblocks do. If you can recommend a downpipe that would be sure not to cause creep, and would be willing to stand behind it, my mod path might change, but for now, I haven't been swayed.
As far as springs go.... I'm not an idiot. I understand perfectly well what higher rates on stock struts can do to the life of a strut. However, I'm going to be replacing struts eventually anyway, but it's not like I'm making an astronomical jump in rates, the stock STI springs are rated at 224/194 lb-in while the springs I would be swapping to (JDM pinks) bump them up to a 257/217 lb-in.... so, a 15% increase up front and a whopping 12% in the rear. I understand the STI struts are fragile, but I didn't realize a 15/12% bump would "break the bank" per se, as I've considered a bump that small very mild IMO, and yes, I will be replacing them a bit sooner, but in stock form, the car feels VERY undersprung/overdampened, and it drives me crazy. Of course I could spend thousands of dollars on coil-overs that I would probably hardly ever use to their full potential, or, I could run the springs I want that have rates I can live with & will match my stock struts dampening very well, and when the stock struts start to die, I will probably end up doing just about the same thing I did to my WRX... dissect them, insert Konis, dampen them to my liking and call it a day.
I understand your perspective, and I truly do appreciate your input. You're an extremely knowledgeable guy, with a TON of experience. I understand where you're coming from. I see the consequences of my upgrade path, and nothing is set in stone, however, from a business perspective, if I wanted you to tune my car, and after tuning with the mods I intended to get, if later, I found myself wanting more... from a business perspective, in would be in your best interests to let me run what I want the first time, as then I would end up paying your shop for at least 2 tuning sessions instead of 1. I know you're trying to save me time and money, which I think is AWESOME!! I respect that, but in the process, it might be costing you money that I might have payed to tune twice lol... but then again, that's a maybe. Some people might need a 50whp gain to be happy, and I might be one of those conservative bastards that would be overjoyed to only see a 20whp gain, you never know.
Which is why I asked you repeatedly in PM's- What kind of numbers/gains do you guys usually see when tuning close to stock cars? This is a question, I asked more than once, without receiving an answer... if you only see 5whp gains, that would be something I would want to know, to take into consideration. If you see 20whp gains, that would be good to know as well. You've been trying to sway me over to another mod path, the easiest way to do that: By giving comparison results. Obviously I wouldn't want to spend $1000 to gain 5-10whp, when spending an extra couple hundred could net me 40-50whp, safely. Which is why I kept asking you what tuned stock cars/close to stock cars put down on your dyno. I've seen a couple miracle close to stock STI's (cat-back & panel filter) put down 35whp over stock... but then again, I wasn't there to see them tuned, I don't know exactly how lean those runs were, what kind of octane they were running, if they iced down the intercooler in order to exaggerate the effect.... which is why I'm asking you, the professional, who tunes them for a living. Hoping that you can give me a clear and decisive answer, that would help me weigh my decisions. It may sound stupid to you, but things like that matter to people like me.
Anyway, I'm glad you posted. Thank you for your time, insight and advice. I'm glad whenever I can have conversations with someone of your knowledge & experience, it's refreshing and extremely beneficial to people like me who don't tune cars everyday for a living. Thanks again.
-Brandon
