exhaust too loud?
- Thread starter Quinton Exler
- Start date
Quinton Exler
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Thank you for that! Could you imagine driving by a small car with a huge 3" exhaust showing? lol
firstorbit84
New member
yeah the A6 had this crazy flat x-pipe resonator as the stock resonator and I wanted no-res true duals with dynomax mufflers and it sounded wonderful at wot because it was a german v8 with 5 valves per cylinder, and at idle it had a great low rumble that would always getme asked "that thing's got a v8?"
however, removing the stock resonator resulted in this terrible drone around 1900 rpm, right in the cruising zone, and I didn't want to add resonators which would have quieted down the whole exhaust. So I calculated the proper length for side branch resonators to basically capture the sound and bounce it back at half a frequency out of sync with the drone to cancel it out. meanwhile the exhaust flowed by unrestricted. I based the length on the result of an equation using the sound frequency and exhaust speed.
The guys at the shop thought I was smoking something when I told them the idea. But I had my laptop with me to see the sound frequencies, and you could see the hump where the drone was and after it was gone. it completely worked!
I lost none of the WOT or idle sound and the drone at a specific RPM was gone. I shared the info with the shop owner and later when I went back for another service he told me that he's used the technique several times since then.
i think the gray one is a top cat
Quinton Exler
New member
Yes! Exactly! So you must believe some of what I am saying and not think I am crazy! lol.
Eric Smit
Enforcer
firstorbit84
New member
well. I really don't have any experience building bass boxes, so I don't know if you're crazy or not...
I'm not even sure the same principles apply. I thought exhaust sound tuning was more like tuning a wind or brass instrument, like a flute or trombone.
Quinton Exler
New member
Very hard for me to explain, I may come up with a photo soon to show my idea.
EDIT EDIT EDIT
@eric Hawt exhaust tip bro.
EDIT EDIT EDIT
@eric Hawt exhaust tip bro.
Quinton Exler
New member
Correct me if I am wrong, but if you used a straight pipe too large isn't it damaging to the turbo?
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firstorbit84
New member
no, it will just be pointless after a certain diameter.
Quinton Exler
New member
I'd say anything above 2.25 or so becomes pointless with our cars doesn't it?
ThatTmoGuy
New member
There was a pretty lengthy debate a while back about when it becomes to big. Some would say 2.25"-2.5" is perfect, others have said if it would fit you would see great results from 4", Imho 2.5"-3" would be perfect.
Quinton Exler
New member
Brings me to my next two questions, question one is short and simple. Does a high flow cat still throw codes. Question two is this, if someone were to use a 2.5" straight pipe all the way back there is decent pressure always being maintained inside the pipe especially upon acceleration. So what about this, You take the 1ft of catalytic or whatever it may be which is roughly a 5" diameter stock and keep it there. Then use a 5-6" pipe all the way back from it. Meaning VS. the pressure that is kept in the 2.5" you now only have pressure built in 1ft of exhaust and the other end is so large its literally propelling exhaust out with no resistance. it would be a similar concept to this... what would be better for power, A 1st cat with NO exhaust at all after it... Just cut it straight off, no resistance after it at all. Or a 2.5" straight pipe which has a battle with being controlled in a lengthy tube.
ThatTmoGuy
New member
Well IDK that anyone has ever tried something that radical on a small turbo car like this. In theory If you could just dump the exhaust at the DP it would be ideal. It would be SUPER LOUD, and not really street able.
IIRC there is no downpipe on this cruze when they shot this.
IIRC there is no downpipe on this cruze when they shot this.
Quinton Exler
New member
Tmo guy, your my new best friend! That's my exact idea! except make it like you have nothing but a stock downpipe. the pressure would have no length to travel at all therefor pressure cannot hardly build even if there is a cat in the way. the 5ft of pipe after the downpipe is a pretty large restriction and people don't realize that. even 3" pipe at that length being a straight pipe still has a restriction and controls the exhaust holding it back.
Quinton Exler
New member
I know Eric, thank you. I am just implying a similar concept. keeping the 1ft or so of stock downpipe then using an obnoxiously large pipe after that and back. so it was as if there is only 1ft of restriction VS. others who run 6ft of 2.5-3" restriction.
Quinton Exler
New member
Not exactly Eric, Let me try to explain it again... If pressure is releasing something and you want as much pressure as possible being released into only a certain area (in this case the turbo) so it can spool harder. This concept works almost like a small creek, or a funnel. When water is flowing if it reaches a larger area it is not only spread out but it is actually propelled faster. However if the area is always small the water will do the exact opposite. It will slow down. you could imagine that large area would have exhaust propelled from the downpipe area if the pipe after it was extremely large. Because the exit has less resistance.