550 Tubi Resonance

very interesting data, stephens. i had a troubling resonance on mine when i bought it and had the tubi removed. when i had the tubi replaced (the same cans) the resonance wasn't there. never measured the mount points though. intriguing.

doody.

 

It's a wierd one. To fit the centre section, the rear is not even lossened, never mind removed. The slip of one pipe once the car was heat cycled/driven has made the pipes stick out more on one side than the other.

The only difference in length therefor is inside the centre section, not the rear box or even the link pipe.

It's possible the slip has exposed the clamp slot, creating a small leak, which in turn reduces the resonance via a drop in back pressure...??

Just guessing, havent seen the car yet.

 

I'd been itching for a long time to measure my 550 w/ Tubis to see if I would be denied access to some race tracks which have severe noise regulations. Verdict: 80dB tracks are out of question and 90dB tracks borderline.

Conditions:
- 550 w/ post-2002 Tubi mufflers, all the rest stock
- static measurements, 3 meters behind the car, db meter at hip height

Ambient noise: 40 to 60dB

Noise measured:
- idle (1000 to 1100 rpm): 83dB
- 1500 to 2000 rpm: 88dB
- 3000 rpm: 81 dB
- 5000 rpm: 91 dB

Clearly illustrates the peak resonnance between idle and 2000 rpm.
Static measurement means much less induction noise, but this is the conditions that most track marshalls around use when they find a car suspicious.

 

Where's the best place to purchase Tubi's 550 center section pipes also known as X pipes? And yes, I am looking specifically for Tubi.

 

Drew:

I'm not aware of a Tubi X-Pipe offerering for the 550. You can call Stebro and hope they can ship you one in a reasonable amt of time. About $600 USD. If Tubi has one, it will likely take many months, have to be shipped special from Italy and cost about 3 to 4 time the cost of Stebro.

Or you can do what I did...had one made by a local muffler shop in Costa Mesa. (Mesa Muffler - ask for Bud). Took them about 1 hour and cost ~ $200 installed. If you do this route, keep in mind:

1. They cut off the center resonator as close to the flange as possible and weld in place the X-Pipe. When you are done, you now have a bolt on system. If you decide to put the OEM unit back on, they reverse the process or you need to buy a used OEM resonator. They can't reporduce the flange on Ferrari's - special tooling

2. They can provide the X portion in SS (Magaflow, Burns etc) or make you one out of aluminized steel.

3. They join the X part with aluminized steelpipes cut to length and weld them all together, then weld the finished X-pipe to the old resonator side of the exhaust pipes.

4. The overall finish is just OK, so as long as you are going for functionality and don't care what you can't see looks like, then maybe this is a way to get what you want for less $$ and a far less time from Stebro or Tubi if they make one.

MB

 

MB, Actually Tubi USA currently has these in stock. Although I haven't seen them I'll assume the fit and finish is up to par with their other systems. When I spoke with them there was no mention of reverseing the process so can't comment on that. For comparision I'm checking out the Stebro system this week. Thanks for your input.

 

Drew:

I meant the custom system is a cut in. I'm sure the Tubi and Stebro are properly flanged for a bolt on installation. When I wanted the X-pipe, I waited months for my order to show up so I finally lost patience and had one made. No where near the finish quality of Strebro or Tubi, but it works for me and I got it one hour.

By the way, the sound you will get with an X-pipe is a more thumper exhaust note at idle and a little more sound under heavy acceleration. Under normal driving, you will not know it is there. Get the Tubi exhaust either "tube only" or the traditional silencer set up from Tubi, with the X-pipe, then you get the sound your looking for. Also, a BMC or K&N air filter will also effect the sound slighty.

If you search "550 tubi exhaust," about a year ago there is a guy on F-chat who has done this already.

MB

 

Maybe I was lucky, but I got the Stebro in just a few days since they had one in stock already. I am having it installed next week along with the BMC airfilters and spacers. I already have the Tubi on which made a BIG difference.
I dont see any reason to pay for a tubi SS since you cant see it anyway. The Stebro was around $600 delivered by DHL.

 

You have a PM

 

I put the $ 600 Stebro X-Pipe on my 550 .... with tubi's. I called Stebro, ordered the x-pipe and received it in about 2 weeks via UPS. If you want a great V-12 sound (much better than tubi's only) ..... I highly recommend this set up.

BTW, to answer a few comments above ..... the Stebro bolts right on using the factory flanges .... in my case it went on fast and was a perfect fit.

 

hey, your results are interesting although not completely correct. It was not the resonant peak you were measuring rather it was the dB-SPL, probably A-Weighted. I dont know what type of meter you used but most cheap ones can use either A or C weighting. If you did the test with C weighting your results are a little too high. C weighting adds more low frequencies.
As for the resonant peak. As most of you have found out the pipes resonate at certain frequencies because they all have a natural frequency in which they just go off. If the pipes happen to be around that natural frequency then they'll resonate like mad. Now that natural peak might be at idle it might be at redline depending on the length of the pipe and the engine. Your right about the resonant peak at 2000 rpm. try lengthening or shortening the pipes it will kill the peak (there at least)
Might i ask why you did your readings from 3 meters away and not 1. most test usually are done at one (easier math). So check your weighting on the meter you used because if the 80 dB tracks dont let you in then ask then what weighting they are using. They should be using A, but who knows....

-mike

 

Thanks for the comments. dBA, equipment from our lab, 3 measurement ranges. We ran the measurements at 3m intuitively, I have to say we were a bit stunned to be well above 80dB at idle.

 

excellent, well i guess you cant get away with the 80 dB tracks. The onbly reason i commented it because I;ve seen people use cheapo meters and keep them on dB-C and then there results are skewed. I re-did a test for someone and their car ended up passing with an A weighting.

Enjoy!

-mike