hi everyone,

i put on my helix downpipe, and it's pretty cool, i notice my car is much faster... however, when i let off the throttle sometimes it sounds like rocks are hitting underneath my car... like right below where i sit... i have the stock mid pipe and a stromung axle back. is this normal? how can i tell if i have a leak or whatever?

also... anyone know the part number for this bolt (see image) ?

it comes off the downpipe here (see pic)


TIA!

 

oops...sorry, not sure what size that one is.


I had the exact same sound w/ my helix dp...sounds like rocks jumbling around in there...it's just the turbo noise

 

i don't have that.. and i have helix up and down with blitz nurspec catback

 

I dont have that either....I have a JDM STI uppipe, and a Helix DP.....no rocks in my exhaust. An exhaust leak sounds more like a ticking sound....but to be sure, check the gasket between the Downpipe and the cat back (or Mid pipe it is sometimes called, that gasket is just below the front seats), also, check the gasket between the mid pipe and the axle back. Also, a good practice when installing exhaust parts, is to always go back after the engine has been heated up and re-torque all the bolts that were loosened or removed during the install. As the metal heats up it expands and the bolts could come loose again, thus causing a leak.

-Ted

edit: for that bolt that you need....just take it to a suby dealer ship, show it to them and say "I need one of these" then proceed to tell them where it came from. They MAY just give it to you free....but if not, it cant be more than a couple of bux. Also, take it to a hardware store....its a metric bolt, but they may have one too, just make sure to get a "grade 8" bolt if you go to the hardware store, or other autoparts store.

 

i have helix up/down and catback.

when i put my exhaust to stock, i used old gaskets and i guess they didn't seal right. i had an exhaust leak. you probably have one too.

when you're idling in your garage or on your driveway or something, look under the car, and see if you can tell if there is an oddly louder pulse coming from where you think the leak is. that's the gasket you need to replace

 

what year do you have? 04/05?

I had that problem too, from what I have been told is that is the sound of detonation which is BAD!!!!!
BAD!!!!!

First suggestion: Get 1 step down colder plugs.
second suggestion: Talk to Mike at Gruppe-S, or your closest EcuTek tuner and get yourself tuned.
From my understanding, with the 04/05 they have an open/close loop fueling delay that will cause you to run too lean under boost.

I personally don't think its the gaskets, I reused my gaskets after installing my uppipe for both uppipe and downpipe and it was fine. Given this is when I only had about 18K miles on the car. I now have 39.5K miles and just swapped the downpipe with a stock gutted downpipe and purchased new gaskits for that cause I didn't want to chance it reusing them.

 

oh and its a 14mm grade 8 nut and stud. you *did* replace that nut and stud... right? :x
The turbo exhaust side outlet stud from a subaru dealership should run you between $12-$15 and $1.50 for the nut. Both special order.

Did you use any WD-40 or PB blaster or something to try and crack any of those nuts? sometimes you gotta hit it 3-4 times and let it soak in before they will come out. then use some anti-seiz on the exhaust parts so they don't have to be replaced next time.

 

wastegate flutter? iono.

 

so say if i want do replace my stock dp/up, i also need to replace the nuts and stud? for an 02 wrx by the way if that helps

 

don't need to replace the nuts and bolts, just gaskets. did you torque all of them down to spec? should be like 26lbs.

 

Looks like the stud came out with the nut. It's happen to me on my 05. Just get them both replaced.

Yup, it sounds like detonation.

Check out this thread. It's long but it'll tell you what's going on.
http://forums.nasioc.com/forums/showthread.php?t=671294

 

Hi guys,

thanks for the replies... I did replace the bolt with something of the same pitch/thread and about the same length, I went to a local subaru dealer and i'm having the stud and nut ordered...fyi it's $7.50 plus shipping...and yes i did use WD-40 and they're all torque to 21ft/lbs.

I do have an '04... as for the 'detonation' sounds, it happens often when i'm going in reverse or at low speeds.. i've never noticed it when i'm punching it, but it just could be i can't hear it. so does this mean i have to shell out big $ to have mike tune my car?

 

was a little worried... so i just went out for a spin... i get that 'popping' 'rocky' sound every time i drive in reverse kind of quickly... you don't produce boost in reverse do you? why would i be detonating in reverse?... :/

 

hmm, for the turbo exhaust outlet bolt and nut, subaru of santa cruz told me $11.50 for the bolt, $1.50 for the nut. I assumed that they would charge more for a stud but I was WRONG!

 

my advice: go to a tuner shop like gruppe-s and have a mechanic or tuner have a listen. Hell if you want to come to san jose and give me a ride in your car I will tell you if it sounds like the detonation my car made before I got it tuned.

I got my car tuned for $700 at gruppe-s and is the best performance mod i've had done to my car. It also does not detonate anymore.

I don't want to scare you, but its a seriously bad thing to be detonating. Maybe first try colder plugs since that isn't too much, for some that has fixed it or made it not happen as often.