I have a Borla with MAC headers and an ory. I love the sound everywhere but between about 2000 and 2500 RPM. In this range it sounds miserable. Sounds sort of like someone making that "plfffffff" sound with their tongue only 1,000 louder. Hope you enjoyed that description. When I'm accelerating linearly during normal driving, say from a start to driving speed, shifting around 3000 RPM or so, the rasp will be produced. Why would it only be in this RPM range? Just some sort of natural frequency of the materials in the exhaust? Any chance of a leak? I can't find one... Thanks

 

I guess you didn't listen the first time around.

http://web.camaross.com/forums/showthread.php?t=366051

It's because of the catless Y-pipe design (causes that mid-rpm range rasp)...And open Borlas are known to be the "raspiest" without cat...

 

No, I went in with the knowledge that my system would be raspier than say, a Magnaflow cat back with the ory and MAC's would be. I just was suprised when the rasp was created only between 2000 and 2500 RPM's, no where else. It just seems strange to me. Would those cones that go in the collectors help at all?

 

By the way, I did appreciate your advice before I installed the system (in the old post you linked in your reply,) seems you were right on with the sound. Thanks

 

I have the MAC's and the ORY, with no cats, and the hooker catback. I have ZERO rasp. (I do have a bullet muffler in place if the cat though)

I'm betting that you have a pretty good exhaust leak somewhere. The pffft sound you are describing is exactly what an exhaust leak sounds like. I had a leak on my MAC's inside the drivers side collector. One of the welds was bad and made that terrible pffft sound. It wouldn't happen when revving the car in neutral, only under acceleraion. The only fishy thing about your sound is that it only happens between certain RPM's. Are you sure the exhaust doesn't just mask the pffft sound at other RPM's?

Find that exhaust leak. and yes, the Borla's are known to be about the raspiest catbacks with headers.

Dan

 

Yes, I am sure that it only happens in that particular RPM range, and it is under normal, gradual acceleration (though if I go really slow it will not resonate at all.) When I go WOT it really sounds good throughout the entire RPM range. I can't rule out the exhaust leak, and like you said in your case, it does not happen when I rev in neutral. This makes it difficult to diagnose. How did you finally find your leak?

 

I found my leak with one of those little extendable mirrors and a flashlight. Look Everywhere on the headers. It was easy to see the leak due to the black soot streaks that form from the exhaust escaping the leak.

Dan

 

Dan, I highly doubt he has an exhaust leak (you would hear more of a ticking sound and should be able to hear it at other times as well). What he is describing is 100% on the mark about a catless LT1/LS1 running through a wide-open Borla. The rasp that set-up causes in the mid rpm range is horrible just like he is saying. I've heard it in person numerous times before. Same exact thing happens with a Loudmouth. Heck, my LT1 with Mac's & no cat (bullet muffler) kinda partially had that annoying sound in that same rpm range (2000-2600ish) with my old GMMG system, although not quite as bad as the Borla.

The simple fix is this: Weld some highflow cats into that Y (won't be easy though) or just have a custom highflow catted Y made (which is what I'd personally recommend). That nasty sound he hears will be gone and the car will sound much better overall. OR, just keep the ORY and replace the Borla with the Hooker Dan has (which sounds MUCH better to me without cats anyway).

 

Good post.

I haven't heard the Borla with an ORY and headers, so I believe you. My exhaust leak didn't sound at all like a tick though, more like a pfft, pfft, pfft like he describes, which led me to the exhaust leak idea. The hooker catback does sound great regardless of a cat or not

Dan

 

Mine has a noticeable raspy "gat gat gat gat" during the above mentioned RPM range. But only when its cold. Once the pipes warm up, the sound goes away leaving a deep throaty tune.

 

My setup is very raspy, and I do have the Y-pipe with No cats, and the cutout on the Y... For this reason I am considering going with an X-pipe And true duals