Tune options after downpipe install

[phate]

Hey guys, so I got around to putting a new catless downpipe onto my STI...(sorry)

I just replaced the factory part, and kept it in case I want to go back. The car is otherwise completely original. The change has been fantastic, boost comes on almost 700rpm quicker and you can really feel it. However my boost now spikes to around 18-19 PSI (according to ****ty test boost gauge) where it was just a little over 15 PSI before.

I've been doing a bit of reading, and people seem to be divided about this mod and the safety to the engine. Some say with stock muffler and intake it is ok without a tune on the stock ECU, others say a tune is mandatory because the turbo will damage in boost spikes.

The guys down at crowe sport have said to "modify the restrictor so that youve got 15psi and you will still get the benefits of quicker turbo spool, which is the main advantage of the aftermarket downpipes. If you wanted to spend a bit extra you could get an electronic boost controller, this will allow more accurate boost control"

If I wanted a proper tune I would need a new ECU yes? Anyone had experience with this issue? Any help is appreciated. Of course I want to keep the car as unmodified as possible!

Cheers,

Fraser

[Guest]

Ball and spring tap job done.

[Marky]

Yep do that ^

Modifying the restrictor will be putting in a smaller "pill" in the hose to (or from?) the boost control solenoid, letting it bleed off less air will lower your boost level. (just need something with a tiny orifice, welding tips are a common culprit)

You'll be able to get it bang on right without too much stress, failling that option B as said is an aftermarket boost controller - you don't need an electronic one as such

A tune is a great idea but looking at $800-1k to do it, it can be done on the factory ECU by a couple of people - Raijin on these forums in Auckland can do it and I can't remember if NZEFi in Christchurch are or aren't - might pay to call them. If in doubt a couple of dyno run health checks can put your mind at ease, it might end up ok on that boost level

[WRXONP]

Wouldn't u need a restrictor with a larger hole ? Because removing it completely lowers the boost - and putting a restrictor of any sort raises boost

I would go ebc - I'm doing the exact same thing to my v2 sti - full exhaust including 3 inch dowbpipe and a closed loop ebc to control boost

[Marky]

Oh there you go then

Depends if the restrictor is in the bleed off side or before the solenoid (I think it's R32's will run more boost removing it from memory)

[czar loc]

 Marky said:

Yep do that ^

Modifying the restrictor will be putting in a smaller "pill" in the hose to (or from?) the boost control solenoid, letting it bleed off less air will lower your boost level. (just need something with a tiny orifice, welding tips are a common culprit)

I had the same problem, reused the pill of my gtb when I converted to single, was spiking at 19psi, ended up chuking a .9mm mig tip in and now it sits on a clean 14.5psi now no spikes and very lil to no drop of off at all

[Rosssub]

I'd go with the ball and spring type MBC or an EBC. Changing the restrictor pill to a larger one counters the boost spike and changes the overall WGDC. So it also lowers the boost gain, sort of defeating the purpose of de-catting in the first place.

[Guest]

Pretty sure these run about 16psi and can get them out to 18ish safely but best check that on a dyno. Only cost you 80-120 and lets you know you're not driving it to death. Oh and you can say I have many wkw.

[phate]

So pills drilled and got it to 15PSI - nice.

However before having this done, I would sometimes get a bumpy idle. Drop to 500rpm then up to 1000, etc etc. Popped a code for airflow meter, so that was replaced however didn't fix the issue...

O2 sensor removed and replaced during downpipe install - most likely this is the issue do you think? I don't really want to have to take this in if it's something I can check myself.

Cheers for the help.

[Rosssub]

Nice, did you drill it out to 1.0mm?

Check for vac leaks/boost leaks and give the IACV a clean out.