club.liberty.asn.au

Feel better than the 2.0GT?

kiahatsiu wrote:Feel better than the 2.0GT?

Heaps. Like a completely different car, sounds and goes a lot better I'll do a bit of driving on the weekend and post up an exhaust vid once it settles down a bit

Although it has cost me a fortune to get there

Exhaust video

I don't know how to embed the video so here's the link

http://youtu.be/swN8b5QTaDQ

So another exhaust update post downpipe; It is exactly like I intended it to be, small noise increase over stock with the performance benefits of the dump however now I want a little more noise and a deeper tone/rumble.

So I plan to order an XForce Mild steel cat-back and only use the 3" mid and Y-pipe and get the exhaust shop to mate them to the STI quads. From looking at the (few and pretty low res) pictures of it and comparing to my memory of the CES Racing dump with high flow cat flanged up after it, I think they'll need to trim the mid pipe a little to get it to fit and maybe get rid of that flex joint.

Borrowed someone else's photo

This photo is a couple of years old and I'm not sure if they still paint/coat these anymore, so if not I might spray it with some VHT.

I've read that flex joints aren't the best and disrupt flow a bit so if it does need cutting I'll see if they can replace that. The resonator looks fairly large so that should reduce any drone that it would introduce, although if it does drone a bit I'll change it out for a nice mid muffler like I did on my old GT.

Hopefully that'll achieve my aim of making it a bit deeper and louder on power but still quiet when cruising around, keen to hear thoughts and opinions from the experts though

Mild steel plus sedan, it might be ok.
If the drone or noise off wot is too much go for a muffler to replace the hotdog.

Xforce cat as well ? 100 or 200 ?

I already have a 200 cat, it's just the XForce Mid with hotdog and Y-Pipe I'll be putting on.

That's what I was thinking Ben if it does drone I'll swap the hotdog for a mid muffler. It does look like quite a large hotdog though so I'm hoping it'll be ok

Dan if your down-pipe bolted straight up to your stock exhaust (like mine did), I am not sure you would need to modify the cat back section unless Xforce are non-standard. I thought most aftermarket exhaust bolted up in the same places at mufflers and dump flange.

Just a question, have people had problems with drone when using a hot dog resonator? I thought they were only getting drone when removing the resonator all together. If it can still drone I might need to reconsider my plan to replace the stock resonator in the stock cat back with small glass packed hot dog.

Shaheenis wrote:Dan if your down-pipe bolted straight up to your stock exhaust (like mine did), I am not sure you would need to modify the cat back section unless Xforce are non-standard. I thought most aftermarket exhaust bolted up in the same places at mufflers and dump flange.

Just a question, have people had problems with drone when using a hot dog resonator? I thought they were only getting drone when removing the resonator all together. If it can still drone I might need to reconsider my plan to replace the stock resonator in the stock cat back with small glass packed hot dog.

Depends on the entire exhaust system, but having had a full TCP TBE with a resonator, it droned really badly. Depends a little on the tune too

alexeiwoody wrote:

Shaheenis wrote:Dan if your down-pipe bolted straight up to your stock exhaust (like mine did), I am not sure you would need to modify the cat back section unless Xforce are non-standard. I thought most aftermarket exhaust bolted up in the same places at mufflers and dump flange.

Just a question, have people had problems with drone when using a hot dog resonator? I thought they were only getting drone when removing the resonator all together. If it can still drone I might need to reconsider my plan to replace the stock resonator in the stock cat back with small glass packed hot dog.

Depends on the entire exhaust system, but having had a full TCP TBE with a resonator, it droned really badly. Depends a little on the tune too

That's not great news, I had a quick look at some photos of the TCP system and it's got a fairly large resonator as well...

Makes me wonder whether this is a symptom of having too much of an open free flowing exhaust. I remember reading a very interesting thread years ago on tuned exhausts where bigger wasn't always better. You want it bigger closer to the turbo but smaller towards rear was the very basic theory. Small but not restrictive per'se. Exhaust gas cools as it condenses so you need less exhaust pipe volume the further the gas moves away from the engine. This somehow ensured exhaust gas velocity was at it's maximum assisting spool. People don't get too scientific about exhaust but ideally it should be tuned/designed for your performance and power goals like any other part of the engine.

Shaheenis wrote:Makes me wonder whether this is a symptom of having too much of an open free flowing exhaust. I remember reading a very interesting thread years ago on tuned exhausts where bigger wasn't always better. You want it bigger closer to the turbo but smaller towards rear was the very basic theory. Small but not restrictive per'se. Exhaust gas cools as it condenses so you need less exhaust pipe volume the further the gas moves away from the engine. This somehow ensured exhaust gas velocity was at it's maximum assisting spool. People don't get too scientific about exhaust but ideally it should be tuned/designed for your performance and power goals like any other part of the engine.

I ended up going to even more free flowing muffs (straight through) and simply replaced the resonator with a straight through mid muffler. My current exhaust is completely free from restrictions, and at the same time it is smoother and doesn't drone.

Drone doesn't have much to do with free flowing exhausts, it's more to do with how you're 'muffling' the sound. From the multiple soobies I've seen or helped modify, and my own - I would say a resonator doesn't do anything. It is simply ineffective at reducing noise on a decently sized exhaust.

In regards to having smaller exhaust at the back - while it is true that a larger dump will help gains the most, the rest of the exhaust also plays a big role, as the gases are still quite hot. Once the car starts making a decent amount of power (say over 200kwatw) you don't want to go too small on the middle or rear, because you'd just be hurting flow. I've seen a number of times people claim on this forum that going to smaller mid section/rear (say from 3" to 2.5") has helped their spool.

For one Phil Lowe says this is not true and he builds some insane cars....

...and for two I have the Varex muffs on the rear, and I can close them at will (opening becomes smaller, similar to stock muffs) and create a restriction in my exhaust. I've had it dynoed multiple times and we've checked out the effect of the more restrictive rear. The turbo has to work harder, need more WGDC, exhaust temps go up, engine can't breathe properly etc. As MSR likes to say "like farting through a straw".

The result on mine is slightly less torque, but similar power, and a very high chance of blowing my exhaust off or hurting the engine. Driving on the street - you wouldn't really notice the difference, but the quieter setting can 'appear' more punchy because all of sudden the car is moving without making noise

Here's my dyno graph of the two runs - Red line is the dual Varex's open and blue line is with them closed.

Very interesting thanks Alexei.

So what is your opinion on running a 3" DP and Mid to a 2.5" Y to the small inlet STI quads (1.75" I think) on a car doing under 200atw?

alexeiwoody wrote:

Shaheenis wrote:Makes me wonder whether this is a symptom of having too much of an open free flowing exhaust. I remember reading a very interesting thread years ago on tuned exhausts where bigger wasn't always better. You want it bigger closer to the turbo but smaller towards rear was the very basic theory. Small but not restrictive per'se. Exhaust gas cools as it condenses so you need less exhaust pipe volume the further the gas moves away from the engine. This somehow ensured exhaust gas velocity was at it's maximum assisting spool. People don't get too scientific about exhaust but ideally it should be tuned/designed for your performance and power goals like any other part of the engine.

I ended up going to even more free flowing muffs (straight through) and simply replaced the resonator with a straight through mid muffler. My current exhaust is completely free from restrictions, and at the same time it is smoother and doesn't drone.

Drone doesn't have much to do with free flowing exhausts, it's more to do with how you're 'muffling' the sound. From the multiple soobies I've seen or helped modify, and my own - I would say a resonator doesn't do anything. It is simply ineffective at reducing noise on a decently sized exhaust.

In regards to having smaller exhaust at the back - while it is true that a larger dump will help gains the most, the rest of the exhaust also plays a big role, as the gases are still quite hot. Once the car starts making a decent amount of power (say over 200kwatw) you don't want to go too small on the middle or rear, because you'd just be hurting flow. I've seen a number of times people claim on this forum that going to smaller mid section/rear (say from 3" to 2.5") has helped their spool.

For one Phil Lowe says this is not true and he builds some insane cars....

...and for two I have the Varex muffs on the rear, and I can close them at will (opening becomes smaller, similar to stock muffs) and create a restriction in my exhaust. I've had it dynoed multiple times and we've checked out the effect of the more restrictive rear. The turbo has to work harder, need more WGDC, exhaust temps go up, engine can't breathe properly etc. As MSR likes to say "like farting through a straw".

The result on mine is slightly less torque, but similar power, and a very high chance of blowing my exhaust off or hurting the engine. Driving on the street - you wouldn't really notice the difference, but the quieter setting can 'appear' more punchy because all of sudden the car is moving without making noise

Here's my dyno graph of the two runs - Red line is the dual Varex's open and blue line is with them closed.

20140724_172537.jpg

Alexi this is where this forum shines so to speak with factual information. I agree with theory and MSR insists on 3 inch through entire system except I'm certain the xforce Y pipe is 2 3/4 inch ? Could be wrong.

Results speak for themselves..
Thanks Alexi for taking the time to graph this and share factual info

ferret89 wrote:Very interesting thanks Alexei.

So what is your opinion on running a 3" DP and Mid to a 2.5" Y to the small inlet STI quads (1.75" I think) on a car doing under 200atw?

Hey Daniel, it's quite a common setup, for whatever reason the Sti quads are a popular choice, and it's worked quite well for most people

If the car is tuned accordingly by a careful tuner, there wouldn't be any problems. Overall maybe you're not optimising the 5kw you might get with bigger mufflers, but I'd say the noise isn't worth 5kw.

Once you go to a bigger turbo and/or E85 - you'd want to open up some more flow, but on stock or even vf52 on 98, should be adequate. We're lucky to have dual exhaust on the lib (we don't have to run a giant cannon muff)