cottoneg

Not sure how many guys here run at Lime Rock. They have an 86 dB noise restriction. I currently have C3 with hooker side pipe headers with max flow inserts. The car is loud.

I called Borla, and they recommended the 400261 as the quietest muffler they have. They mentioned the 400069 may work also, with 400374 being the “loudest” of the quiet mufflers. Anyone try these?

Any help appreciated if you found another side pipe solution. BTW: the Hooker quiet pipes are not an option. The opening is so small, while quiet, it kills the engine. Cuts the horsepower in half. Like running a marathon breathing through a straw.

69autoXr

Would you run the Borla's with the Hooker sidemount headers?

I have no experience with them, but comparing the specs of the Borla to the Max Flow, I'd be surprised if they were quieter. They have a larger flow path i.d. than the Max Flow (3.5 vs. 2.5) and are a shorter length. They may have more volume of packing material however, so maybe they would be more quiet.

racervette69

Have a friend that ran them after failing Roebling's 105db. Have heard them, they rumbled. They passed there, but dont think they would pass the 85db. Think these were the #69. They are off the car and think they are for sale, see what he thinks.

cottoneg

Thank you! What your friend did was exactly what I have in mind.

A few questions:

Do you know the muffler #? I looked up 400269 and it does not correspond to a current active number.

Why did he pick that muffler? I have been looking at muticore mufflers. Is his a multicore or straight through?

I was also thinking of having the tip rotate down and point to the ground so they would not point directly at the meter. Did your friend try that?

Any other mufflers to consider? Dynomax Super Turbos… MagnaFlow's??

racervette69

Just got off the phone with my friend. Said he was able to pass the db with the Borlas at the tracks in the SE. They were multicambered. He thinks the 85db is possible with the pipe rolled down. Think they are called XR10's now.

midigike

Don't race but a 85db sound restriction at a race track is just crazy. My wet and dry vacuum is rated at 85db and I can here my small block rumble while the vacuum is running. What a PITA
All that horsepower and then have to choke it with the mufflers.

cottoneg

There are a few tracks that have sound restrictions. What I am trying to do is get a very low restriction system without the noise. With all the guys that run cars at events, I actually surprised nobody has run across and solved this issue. racervette69 has really provided great info and picture!

I will follow up with Borla. The preliminary info I have is that Borla Multi-core XR1 mufflers may be the way to go. I want to confirm with them that 400261 is the quietest, followed by 400069 and 400374. If anyone else is interested, here is the link:

http://www.borla.com/products/xr1.ht...FcMSHwodWrYAiw

As racervette69 mentioned, I may make the pipes with tips that can be rotated, and if too loud, turn the tips down. I would not want this for the street as I will blow up all sorts of stuff.

If anyone has anything else to contribute, please feel free.

Thanks

0Magna_Flow

We have a couple of options with 4" in/out that might work for you. You can check out our specialty race mufflers here; the 6" x 6" x 14" race muffler might work to take some of sound intensity out, but 86 dB is a tough target with this car, I can well imagine.

We also sell a universal muffler, which comes with our straight-through design, but for a 4" in/out, you'll need a muffler with a 7" diameter, which probably starts to border on bulky-looking with the sidepipes. If that fit was fine, we offer that in plain stainless (part # 12770) or polished (part # 14770) finish. It should remove more sound than the race muffler, but 86 is such a tough target.

David Borla

Our multicore technology is fully straight through and will actually out flow any traditional single core muffler that attenuates sound to the same degree. In other words, if you have to meet a specific decible level, and use a traditional single core muffler to meet that limit, our multicore muffler will meet that limit but will also dramatically outflow/outperform the single core muffler. Of course this is providing you use the same inlet/outlet size. For example, if you use a 3" in/out muffler with a single core and compare that muffler to our 3" in/out multicore muffler, you will see far better performance and sound attenuation from our multicore muffler. Race teams have been testing our mufflers in this way since the early 90's and the technology just works. This multicore muffler design was invented/discovered by Alex Borla and he still hold numerous patents for multicore technology to this day.

Also, our mufflers are made of 100% T304, austenitic stainless steel which will never rust and is more durable for racing applications. Unlike other manufacturers who use an inferior grade of 400 series, ferritic stainless steel. Do a quick search on "rust" for muffler manufacturers that use 400 series stainless and you will see that after a short time the mufflers rust. The 400 series alloy was not designed to last forever unlike 300 series which was designed to NEVER rust. You can find all of this information on the web.

Here's one of thousands of links on the subject - http://www.twi-global.com/technical-...ss-steels-101/

So, if you want a muffler that out flows a single core muffler, attenuates sound to a greater degree and is made of the best materials, which will never rust, you need our multicore muffler.

If you want to discuss this with me directly please send me an email to davidb@borla.com or call the direct line to my office at 805.246.6067.

Regarding part number 400269, give me a call or send me an email and I will sort this out for you.

Cheers!

lvrpool32

Limerock's noise limit on none "big race day" is crazy! Mine was way too loud and I determined it was a waste of time and money to try and make it work (different mufflers, welding, re-tuning etc etc)...and went to NJMP instead

cottoneg

Thank you, it is a tough target! But with more tracks going with sound restrictions, it is something that needs to be addressed so people can run on tracks near them.

cottoneg

My only issue, living near Riverhead on Long Island is it took me over 10 hours to get to the track due to traffic. I love NJMS, but the ride is killer. I will speak with Dave on Monday and see what we can work out.

cottoneg

Thank you Dave. I will call you Monday, June 15th..Thank you!

cottoneg

Please allow me to follow up on this post. My intent is to help anyone running into a similar noise issue some trouble at local tracks.

I took Dave Borla up on his offer and called. I also spoke to Ryan Baker
Customer Service Specialist (ryanb@borla.com) at 805.246.6073.

We went through the spec on a number of mufflers and came to the conclusion that the Borla 400115 XR-1 Multi-Core racing muffler would give me my best chance at meeting the sound requirements. This muffler is usually used on racing trucks and is almost as big as a side pipe. 34”X8.5”X5.5”. Initially I was a bit concerned with the step down from the 4” collector to the 3” muffle opening. However, if you pull a side pipe and look down the tube, the most free flowing Hooker Max Flow is about a 2” opening. Having said that, this muffler may very well make MORE horsepower than the Hooker Max Flow and tons more than their “quiet muffler” inserts that have a 1” opening.

Another big piece to this is the outlet of the exhaust. Borla makes turndown/turnout outlet (part # 20146) that will allow me to rotate the tip. I believe racervette69 had posted a great picture of this. But I guess it was deleted. If the tip is not pointed directly at the meter, I have a better chance of passing.

I received the 4” outlets and the mufflers should arrive soon. After all the fabrication is done, I’ll let you guys know how it turned out.

MelWff

Unless things have changed they stand behind the car when testing the sound level so don't see the point of aiming downward. Have you confirmed how the actual test is performed. I spent most of a morning years ago dealing with this issue at a time trial. Ended up with large coffee cans with steel wool attached to the outlet, not pretty. After that experience I found Bridgehampton which had no noise restrictions but is now sadly gone.

cv67

Sidepipes a necessity?
Could you remove the spare tire carrier would think it would open up some room for options, just a thought.
They make oval tubing although not cheap for ground clearance issues

cottoneg

I miss Bridgehampton. Darn that was a great track. You are correct, the last time I was at Bridgehampton they stood behind the car and asked me to bring the revs to 2000. There was a sound restriction near the end, but they were very forgiving.

Last time I was at Lime Rock it was a rare no noise restriction day. My friends told me they have the sound meter down the main straight. I am not sure how many feet away from the track it is and that is how they do the sound check. So in that case, turn down tips would help. I have heard others just lift or step in the clutch.

Other tracks are starting with sound restrictions, seems to be the way of things unless the track is way out of the way like NJMS.

cottoneg

No, side pipes are not a necessity, Just a personal choice.