dump pipe + mid pipe + stock muffs

[gtspec]

i got a 07 GTB but not a STI thou, and from my experience i have only changed to the phat dump pipe (stock mid and muffs) and just from that i noticed a big difference in response and the power delivery up top end..

i would 100% recommend doing this..

Out of interest have you had an ECU tune? If not any dyno time to check vitals (A/F ratio, boost spikes, torque curve)?

Interested to see - yes before everyone jumps in - I know a tune will make the most of it, but I have strong suspicions the stock ECU is smart enough to handle this safely.

Also on the TBSTi - I'd be inclined to try keeping the stock muffs - the dump and centre are obviously restrictive, and sure the cans would open up a bit more, but seeing as its two 2" pipes on the stock TBSTi mufflers I dont think it'd be huge with such a small turbo on a 2.5lt car. From what GTSPECB is saying its along the same lines. I wouldn't want a loud rumble - IMHO the Liberty doesn't suit a loud exhaust note like say a WRX does

I have it on good authority (well lets say 'reasonable authority' ) the GTB mufflers and TBSTi mufflers are the same internally, but I dont see how - as the TBSTi mufflers are twin pipes all the way into the muffler body (its not just the twin outlet on the end plate of the can)

no tune as yet.. but there are plans for one in the near future

[Boxer]

as the TBSTi mufflers are twin pipes all the way into the muffler body (its not just the twin outlet on the end plate of the can)

eh? are you saying that from the y at the diff, each muffler has two pipes? I know the 06 TBSTi doesn't

Nooooo From the twin tip outlets - shine a torch inside and you can see sepearate chambers to at least halfway back into the muffler body. Hence not the same as GTB muffs

[Boxer]

i got a 07 GTB but not a STI thou, and from my experience i have only changed to the phat dump pipe (stock mid and muffs) and just from that i noticed a big difference in response and the power delivery up top end..

i would 100% recommend doing this..

Out of interest have you had an ECU tune? If not any dyno time to check vitals (A/F ratio, boost spikes, torque curve)?

Interested to see - yes before everyone jumps in - I know a tune will make the most of it, but I have strong suspicions the stock ECU is smart enough to handle this safely.

Also on the TBSTi - I'd be inclined to try keeping the stock muffs - the dump and centre are obviously restrictive, and sure the cans would open up a bit more, but seeing as its two 2" pipes on the stock TBSTi mufflers I dont think it'd be huge with such a small turbo on a 2.5lt car. From what GTSPECB is saying its along the same lines. I wouldn't want a loud rumble - IMHO the Liberty doesn't suit a loud exhaust note like say a WRX does

I have it on good authority (well lets say 'reasonable authority' ) the GTB mufflers and TBSTi mufflers are the same internally, but I dont see how - as the TBSTi mufflers are twin pipes all the way into the muffler body (its not just the twin outlet on the end plate of the can)

no tune as yet.. but there are plans for one in the near future

So any idea how healthy it is in regards to boost spikes, AFR and torque curve?

[gtspec]

So any idea how healthy it is in regards to boost spikes, AFR and torque curve?

sorry got no boost gauge to check spikes.. but i did notice sometimes a bit of backfire in the exhaust, so i think it runs a little rich but besides that i havent had any problems and have had it installed for the past 6 months

[Sheik Jabooti]

For those interested here was a PM sent to Pips asking about the results:
--------------------
Hiya pips,

I was considering this exact same option. Did you go ahead with the DP + 3" mid + 3" Y + stock Muffs? What were the results?

-------------------

Results were fairly good. The car ran 140kw atw with phat dump + 3" mid section + standard muffs. A custom tune took that to 166 kw atw. The dump pipe made a massive difference even without the tune, i highly recommend it. If i was to do it again i probably wouldn't worry about the mid section unless your planning on changing the mufflers.

[cpitts]

as the TBSTi mufflers are twin pipes all the way into the muffler body (its not just the twin outlet on the end plate of the can)

How did you come to that conclusion?

MY05 GT Wagon Muffler (I suspect the MY07 one is a LOT more restrictive, just from tests I did when changed over)



Read here for full thread: http://forum.liberty.asn.au/viewtopic.php?f=10&t=4667

And the centre pipe from a MY05 GT Sedan (all looks consistent for MY07's as well):



http://forum.liberty.asn.au/viewtopic.php?f=2&t=5362

Reality is, the mufflers are the biggest source of back pressure in the system. The dump pipe would be the second.

To avoid volume increases at the cans, keep the tip size (diameter) the same.

[Sheik Jabooti]

Reality is, the mufflers are the biggest source of back pressure in the system. The dump pipe would be the second.

To avoid volume increases at the cans, keep the tip size (diameter) the same.

Yeah, but from what i understand the oem dump affects the spool up time. Restrictive plate causes spool up to take longer so gives a touch of turbo lag. The phat dp (or similar) allows turbo to spool up faster so gives a more responsive feel. If you're looking at top end power then, yes i agree the stock cans will definitely slow you down. For me though - i just like fast starts posting.php?mode=edit&f=18&p=111800#

BTW. What did you mean by "To avoid volume increases at the cans, keep the tip size (diameter) the same". What tip size were you referring too?

Also nice pics - it helps alot.

[cpitts]

Don't get me wrong, a bigger bell mouthed dump pipe will give you some instant throttle response improvement, but also consider that the output of the turbo is less than 50mm wide (exhaust is bigger than that at the very top) so when it comes to air speed at very low rpm, you're not really hindering things.

If you want to improve throttle response there's a range of things you can look at, not just the first 30cm after the turbo. Look in front of the turbo if you want throttle response, get rid of the restrictions and you'll quickly have a quicker take-off, oh, and get an ECU reflash. The stock ECU program is robbing you of throttle response, not the dump pipe alone.

Also get some straight through mufflers on there to remove pressure points AFTER the turbo. It'll give you more results that changing just the dump and leaving the stock cans in place.

TIP sizing comments: the pipe coming out of the muffler can itself. So typically the last 15-20cm of pipe out of the muffler can. Keep the diameter of the pipe the same as stock and the noise out of the muffler will be pretty much the same. Very little difference in tone (maybe an octave or 2 lower, but that's about it). Volume may go up a small amount at most cruising speeds, but be warned rev it out and you will certainly get more noise.

[parso_rex]

Hmm I wonder could I just drop the Y section when I dyno thing tomorrow LOL - got flamez Br0

[cpitts]

Just get a pair of 2.5" mild steel pipes made up with a hanger point and a joiner and away you go.

WARNING: It may be loud.

[Sheik Jabooti]

If you want to improve throttle response there's a range of things you can look at, not just the first 30cm after the turbo. Look in front of the turbo if you want throttle response, get rid of the restrictions and you'll quickly have a quicker take-off, oh, and get an ECU reflash. The stock ECU program is robbing you of throttle response, not the dump pipe alone.

Also get some straight through mufflers on there to remove pressure points AFTER the turbo. It'll give you more results that changing just the dump and leaving the stock cans in place.

Thanks cpitts.

Yep I had all that on the MY07 GTB manual sedan I just sold. The only thing missing was the dump pipe. In the end it was all a little too aggressive (ie cop magnet). Now I got a more family oriented auto GT Wagon (no B.Spec and no loud muffs). A bit like the original poster, I'm now looking for a little extra oomph without the boy racer broom broom sounds. Hence I was following this thread. I reckon your gut, cut and shut in combo with a resonatorectomy and a dump pipe looks like a pretty reasonable compromise. Oh yeah, the tune (verso in my case) is mandatory.

[cpitts]

In that case, I'd agree.

In all honesty though, if you do a silicon intake and dump with gutted muffs and otherwise standard airbox you'll get more than enough throttle response. But be warned, the muffler gutting is time consuming and could be costly (still under $1K easily though) if you get someone to do it.

The changes your looking to make are directly in line with the mods I'm making to my car for the same reasons.

The other thing to change is the boost control solenoid to a 3 port unit, you get MUCH tighter boost control without going to the full on electronic boost control with bells and whistles in the cabin of the car. Very wife freindly and invisible.

[parso_rex]

I don't reckon you'd need the three port solenoid for mild mods. For some reason the two port seems to be doing a very good job rock solid round 16 psi maybe the VF46 design is a bit better than the VF39 and similar who knows
It might be a different story with 18 psi and every desirable bit of gear attached of course

[cpitts]

That's a surprise! Normally they can't hold boost that well at all. Hit their peak early with a spike then peter off real fast. Wonder if they're using a better model???? I'll go have another look at your historic charts.

[GTSPECB STI]

for most set ups here a three port is not necessary imo, boost control is pretty damn good with stock vf46 set up from my experience....get a good hotdog resonator and stick it in the mid pipe if you are concerned about noise for neighbors and family. After market free flowing dump pipe is an absolute for performance imo.