v5sti

Hi All, First post but have found this forum a great resource so it is my turn to contribute.

I am an Engineer that has owned for last 10 years Subaru STI's. This has included a Japanese import Version 4 and MY06. I have always modded these rides to extract the most out of them. This has included self tuning of OEM ECU's and racing.

Being 45 (ish), my wife wanted me to ditch the boy ricer image and go for something more conservative.....hence the C32 was purchase a few months ago with 32k km on clock.

I know what forced induction vehicles like and so I will be doing the following mods in the order shown;
1. C55 Y-pipe Air intake - (completed)
2. Air induction cooling system - (undecided which way to go)
3. Exhaust - Sec cats or Resonator or both (undecided)
4. Main or Supercharger pulley with ECU re-tune
5. TCU re program

The above mods will be done over the course of the year and I will post results as per this thread when they are completed.

SO...onto the first mod;

C55 Y-Pipe purchased for AUD$165 and installed. I also cleaned the air OEM air filters while I had air boxes open.

First reaction is that part throttle response is much better. I am no longer doing the ECU reset procedure. After comparing results on Gtech, I am getting upto 10 hp more at low end so this explains the better response. 0-60 times down a little from 5.111s to 5.001s. This was with ambient temperature about 10 deg C higher, so I am stoked with result.

Notes on Gtech results attached.
1.Main run (black) is best time achieved as stock vehicle.
2. Other two runs are typical runs with new Y-pipe
3. All runs on same stretch of road, using 30cm roll-out (don't want too much stress on car components).
4. Stock run was at night time at about 15 degC and other runs were during the day at about 25 degC

macbryanie

Nice write up and gains, but more amazed that you got a c32 with 32,000kms on the clock. It must be perfect. Enjoy the new toy.

anasdaouk

im getting the ypipe and a drop in K&N filter..any comments?would they give me some nice sounds different than stock anybody got a picture for an intake y pipe??those are my first mods in the course of the next month ill be ordering eurocharge pulley kit (185mm) with a ecu tune from diff source and a tcu flash..unleashing the beasttttttttttt and oh primary and secondary cat deletes well am worried abt it dono if it gives gains or not and dono if it will sound decent enough appreciate comments peace

AMG3.2

Nice, FYI though, you won't gain anything from secondary car and resonator deletes. I have them both and didn't notice a thing.

MBfinatic

what really? I did! different car tho.

v5sti

Hi, My experience with forced induction cars (mind you I always test before and after with Gtech and data logging) is that if you let them breathe in and out easy, this is the best way to get gains without changing boost etc. However you must be careful on how the Engineers have programmed the Maps in the ECU, sometimes they are adaptive and sometimes rigid. I am not convinced about aftermarket filter systems making a huge difference, I have done this to two prior vehicles without registering any discernible gains. From my point of view the C32 has very good intake capability with the twin intake system and two separate filters. However all that size and then running into the OEM restrictive Y-Pipe is a bit lame. I Have attached photos of my Y-Pipe set-up, you will notice it is hard up against firewall.....two points to consider that is not covered in the DIY guides is to remove to metal clips on the firewall which will rub through the Y-Pipe and also I placed some foam tape between the ypipe and firewall to prevent rubbing.

With regards to secondary/primary cats, dont remove the primaries as this has A/F ratio gauge attached and depending on the Maps is used as a feedback loop to trim A/F ratios for optimum fuel economy when running on highway etc. I presume you mean the resonator. Again, gavin looked at the exhaust and reading stuff on the forums it seems like a fairly unrestrictive system. It becomes a personel taste thing regarding sound output. have a listen to the different options on You tube. I will eventually by modifying this also and will post before and after Gtech results.

Just as a side note, by making the intake and exhaust free flowing it helps with the air flow when upping the boost with a pulley. Also be careful of the possibility to run leaner due to the increased amount of air flowing. Not too many WOT runs before doing the pulley and ECU re-tune!

Cheers and enjoy the modding bug!

P.S I would also consider ways to cool the intake air. Huge gains can be had due to a denser air means more air in charge and bigger boom!

AMG3.2

So you got a 10 horsepower gain huh? Since you've tested it and gotten reliable results, I think I might grab one of these y pipes for my intake.

I think you mean 55 Kompressor series Y pipe though. The C55 is N/A and has a different Y-pipe.

One question though. Did you just order the Y-pipe or did you also order new hoses etc?

v5sti

10 hp was not across the board but it was at some low end points, but generally better throttle response all over.

Please find attached my install bible which was originally based on a post in the SRT forum but I have included my inputs based on C32 install. It also has pictures and WIS information also. I am not sure who posted the original DIY guides but most of the credit goes to these guys (I guess they know who they are).

FYI: I bought the complete Y-pipe assembly with hoses.Part no's are in attached document.

Cheers

mkonei

There is no "y" pipe on a C55 intake...the air box mounts directly to the throttle opening, and the filters are contained in the box. SL55/E55 etc must be what the OP is thinking of.

jturkel

+1

additionally, to see the full effect, it is recommended to get the tubes and the larger 55k intake boxes since they are (IIRC) 50% larger

AMG3.2

My bad on the C55 part, none the less, I meant the SL55 or E55 part. OP, thanks for the advice!

FrankW

you can definitely gain power from removing the primary and secondary, but you will need to make sure you have consistent piping size all the way to keep the exhaust free flow and keep the exhaust velocity up. it'll benefit more if you have improve the intake as well as getting a tune.

AMG3.2

I didn't delete the primary cats. This is probably why I didn't notice anything.

FrankW

secondary is actually just a small resonator. that's why it only affect sound.

macbryanie

Please advise where you purchased the SL55/E55 y pipe in AU as dealership has quoted $427 for 1130900129

v5sti

Macbryanie...please check email.

Cheers

macbryanie

Brilliant..Thank you.

johnng117

http://www.parts.com/parts/2003/MERC...icleid=1429488

$134.40 at Parts.com

macbryanie

Thank you; but I am "down under" and Parts.com are not international. If they were it would be my holy grail. Cheers,

positronicC32

You can use a mail forwarding service like http://www.reship.com/?gclid=CMme7o2y5q4CFYYepAodREgXhw. It's like having a replica Holy Grail.

My buddy uses it for all the stuff he buys from the U.S, when the company doesn't ship externally.

...anyway, now I'm after a Y-Splitter and connecting hoses, I'll be setting one up. My usual haunts don't have the parts available.

Cheers.

johnng117

Problem is that part.com need a credit card which is registered in US which is the biggest problem.

positronicC32

Thanks for the heads-up. Until they offer PayPal or some other form of payment like internet banking/direct deposit then that is definitely an issue! I will ask them. Cheers.