kiahatsiu wrote:Feel better than the 2.0GT?
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.
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
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.
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.
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?
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