phile

I think crabman is onto something. One of the posts on the first page was about a member who talked to R/T about the raspiness. R/T Stated that the raspiness could not be from the cats themselves. Since the raspiness is most likely not do to cats, it is the straight piping w/o any sort of dampener that is probably the culprit.

Even if some people here have removed their high flow cats and eliminated the raspiness, that does not mean that the raspiness occurred IN the cats. Although the addition of the cats may have changed the harmonics, the raspiness most likely occurrs in one of the non-dampened straight areas. The only solution is to prolly change out one of other the pipes, or weld round stock on like crabman suggested--that is, unless the problem is the metal cage around the 02 sensors

myz8a4re

iTrader: (2)

i agree highly. this is why the resonated cats are such a great success. there is dampning added to the long, hollow straight testpipes.
so crabman, its just a test-&-go type installation of these metal pieces right. would it be true that the bigger(longer/wider) piece of metal would be more beneficial since numerous applications & attempts to add pieces could be eliminated? a special thickness off the added metal pieces? any special metals to use? if i had the regualr testpipes i would try this w/o a doubt. i have access to many different metals as well as being able to weld. i have access to all this at my work. would be a very interesting test & would prove that the rasp is only harmonics related & not an internal design problem, wich was stated previously in this thread. lastly would show very affordable as a fix to the rasp!

-justin

booger

iTrader: (6)

Let us know if you do the test like that and it works.....I think my cats collapsed last night and the rasp went away

myz8a4re

iTrader: (2)

i have the kinetix resonated testpipes so i have no need to do the metal tab weld on pieces, i mentioned that i would deffinately try this if i had the regular testpipes & was dealing with the rasp. im hoping somone else can take this test on & let us know the results. if i can be of any assistance in the test ill be more than happy to take part. if tere is somone local that has the rasp issues we can schedule a test day!
-justin

crabman

Yes, the straighter and longer the piece the more likely you are to have the possibility of building up a resonance/drone/rasp. As I said this is a very common problem in the diesel world.. We use 4 or 5" pipe and straight through mufflers. Combine this with the long runs you have in a truck and some sort of drone is almost a given unless some steps are taken such as a resonator or tabs. I would use a metal suitable for the exhaust. Stainless roundstock for instance on a stainless exhaust. I say roundstock just because it is the cheapest and most readily available in stainless. For galvanized I have seen folks weld on chunks of angle iron. Other than being stiff the piece need only be heavy enough and long enough to have the effect of changing the pipes tone. It would be interesting to see how or if this works on the smaller diameters and pieces you are dealing with here. I'm not sure if the drive pressure is a factor here either. I run about 50 psi of boost on a 70 psi drive pressure which is typical of a bombed truck. Might be worth a look though, because its a proved and common method of dealing with this problem in our trucks.

supra crazy

iTrader: (22)

Whats round stock and where can it be purchased?

booger

iTrader: (6)

I believe he is talking about round stock being piping just like your exhaust but the inside diamiter would be the same size as the out side diamiter of your exhaust

myz8a4re

iTrader: (2)

yes round stock is metal material(steel)that is round just as the exhaust piping itself, just as angle iron is angled metal stock. the round stock would need cut so that pieces of it can be welded to portions of the testpipe tubing. this is not what has to be used to be welded on. for example, if anyone is planning to let thier local muffler shop help them with this, any scrap chunks of metal can be used. just have pieces welded to the testpipes on each tube or any long stretch of tubing where no resonated material or muffled material is found. then go for a test drive. add more pieces untill the rasping deteriorates.......again, as crabman said there is no guarentee this will work on our cars, but worth a try as no one would see the welded on pieces under the car........this gets touchy since most will not want to weld on pieces to thier expensive aftermarket exhuast systems. but if the time were taken, nice long pieces of angle iron could be ran across long exhuast pipe sections on the top if those pieces were removed from the car. this would be almost totally unnoticeable as it would be hidden on the top. then once welded on the piping could be put back into place. this could be done much more easily if pieces of metal are welded directly to the bottom of the exhuast piping so no parts are needed to be removed......option is of those who take on the task..........now that the obvious has been stated well see if anyone wants to do this, lol.

-justin

crabman

Round stock is a long round piece of steel that is not hollow but rather solid and available in various lengths. Think pipe but not hollow. The shelves in your oven are made of a whole bunch of pieces of thin round stock. Angle iron is shaped like an L but both legs of the L are the same length. Both are commonly used in metal work and will be available at any welding shop. As stated any piece of stock will work so long as it is stiff, reasonably heavy, and it needs a little length. Six to twelve inches or so is common. Remember that you are trying to prevent the pipe from having a harmonic or at least change its pitch. If you for instance welded a chunk of coat hanger to it you can imagine it would be able to do little to effect any dampening. The concept is simple. The pieces in your exhaust are in effect acting like a guitar string. This gives you a harmonic. Good with a guitar, bad in your exhaust. You are simply trying to dampen that harmonic. This is something the manufacturer does in design and R&D, shape the exhaust and place the mufflers/cats so that the car does not have this problem. It would be helpful if one of the aftermarket folks came out with an entire system, header,high flow cats, right on to tailpipe.

myz8a4re

iTrader: (2)

Well, as long as we keep buying these aftermarket exhaust systems then they'll keep selling them, rasp or not. BUT as I keep mentioning, kinetix did the research & designed the resonated testpipes just for this reason. In the majority of cases the testpipes are seperate from the exhuast systems sold so these pieces can easily be added to the exhuast to eliminate rasp....unfortunate for those that have purchased the nonresonated testpipes already & are dealing with rasp.......I'm thinking of removing the added inline resonators that come as part of my borla true dual kit to get the exhaust louder, ill still be safe since I have resonators in my testpipes.........its all about the resonators!

-justin

F2dmfine

Justin,

Where in FL are you?

chaparro78

iTrader: (2)

I had the same rasp problem on my car when I installed race pipes. I saw kinetix made race pipes with inline resonators. Thing is, I had already spent almost 200 on my regular race pipes, did not want to drop 400 on some with resonators. So I did the next best thing. I went to a specialized muffler shop that makes custom exhausts for cars and had them weld resonators to the race pipes right past the O2 sensors. It took just over an hour, $95 for both resonators and installation.

Here is a picture of how it used to look

chaparro78

iTrader: (2)

A piece of the race pipe as well as a piece of my exhaust were cut in order to make room for the resonator

chaparro78

iTrader: (2)

Then the flange is welded to one side of the resonator and the race pipe to the other

chaparro78

iTrader: (2)

Finished product
=No more rasp
=No loss of airflow
=Deep tone

The resonators are 12 inches - 2 3/4" on the inside, just over 4" on the outside

booger

iTrader: (6)

best salution Ive seen so far .Im glad La Bree was out of resonators untill the first of July . Taking the car to a muffler shop pronto

LBSOHK

any updates ?
<\=-- thinking about getting test pipes soon...

coachk

iTrader: (21)

Chapparo78,
Brand name of those resonators please? Sounds as though you might have solved the mystery.

chaparro78

iTrader: (2)

Dunno brother. He put on the ones he had there in his shop. Honestly, any good resonator should work.

KISS

Rasp finally gone! I also went the resonator route.