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Topic Review (Newest First)
07-13-2007 02:07 PM
454C10 check this out
07-13-2007 06:43 AM
454C10 I have used dynomax bullets as a resonators with great results. They also have perforated tube design and they don't cost much. They flow also like a straight pipe.

Recently I install dual 12" dynomax mufflers in a very ugly sounding exhaust that would resonate so badly you would think the exhaust was dumping in the cab. After the two little dynomax's, it sounded almost like stock exhaust with no flow penalty.
07-12-2007 05:52 PM
Originally Posted by 1970Chevy
Hey does anybody know what would happen if one were to only run resonators and no muffler. I know that on luxery cars there is a muffler Plus a resonator, thus a very muffled and quiet sound. I would think that the resonator doesnt do as much murdering of sound that a muffler does. I also take into consideration the tone of the sound produced, and Im assuming that depends on the volume of the resonator chamber.
slp has the loudmouth resanator exhaust system for camaros etc .....some resonators look like a perforated core glasspack(tips) but arent the resonators found in the exhaust system upstream of the exit just hollow like an expansion chamber ? ........I have an old set of "glasspacks" that appear to have 2 tubes in them ........that I'm going to cutapart and make resonators out of
07-11-2007 09:20 PM
jimfulco 15" of water refers to how they measure the vacuum. It's a vacuum that's strong enough to lift water 15" up a tube. Imagine putting a 6-foot clear rigid plastic tube on a vacuum cleaner and sticking the tube straight down into a bucket of water while the thing's running. If it sucks the water up 15" higher than the level of water in the bucket, that's the strength of vacuum they used. The "Hg refers to how far it'll suck mercury up a tube. The whole stinkin thing's kinda confusing, like measuring power in horsepower vs kilowatts.

Conversion: 1.5"Hg = 20.4"H2O = 0.74psi

But just in case anybody's curious, glasspacks actually are quite a bit quieter under water, with sort of a burbling sound. Can't say how they performed though, what with the wet tires and the resistance caused by water up to the stinkin doors, but the sound was kinda cool.
07-11-2007 03:55 PM
454C10 Yes the 3 inch will flow better but the extra length (32 inch versus 18 inch) will cancel out a lot of the flow improvement gained from the extra diameter.

3" pipe has 180% more cross section than a 2-1/4 pipe but 32 inches just happens to be 180% longer than 18 inches. So there should be no flow difference between a 32 inch long, 3 inch diameter hornie and a 18 inch long, 2-1/4 diameter hornie.
07-11-2007 02:58 PM
elcaminodragster ok so they tested 2 1/4 inch louvered glass packs. how long where they???

also on that web page the test results for straight pipes...

2 1/2 inches 521 cfm
2 1/4 inches 365 cfm
2 inches 283 cfm

so from 2 inches to 2 1/2 inches it nearly doubled with just a 1/2 inch. so what might the flow be for 3 inch louvered glass packs??? it must be far better then the 2 1/4 inch ones.
07-11-2007 02:49 PM
454C10 You got it.

They make a consistent pressure differential across the muffler and measure the flow. The more air that goes through, the less restrictive the muffler is.

In this case, they are sucking air through the muffler. The vacuum pump speed is increased until a certain pressure differential is created across the muffler and then they measure the flow.
07-11-2007 02:16 PM
elcaminodragster hey 454c10,

a low cfm would mean high back pressure??? and a high cfm would mean low back pressure??? correct??? i know its a dumb question but hey im here to learn and cant learn with out asking stupid questions.
07-11-2007 01:52 PM
454C10 Vacuum is the absence of pressure. So yes, you can have vacuum without atmospheric pressure. However, if you live on a planet with no atmosphere then vacuum would be atmosphere pressure.

Yes, soda would shoot into your lungs but your lungs would explode not implode.

And since sound doesn't travel in a vacuum. Glasspacks would be very quiet in a vacuum.
07-11-2007 01:37 PM
REALGONEKATT Can you have vaccuum without atmospheric pressure? Wouldnt it cease to be vaccuum and just be atmosphere?? wouldnt the soda just shoot into your lungs as they imploded???? at any rate your glasspacks would sound like ****t...
07-11-2007 01:17 PM
454C10 Let's say you have a big glup in your center consel and you don't feel like picking in up because is a about 1 gallon. So you get a long straw to suck out the life giving soda. If your lips were 15 inches away from the top level of the soda, it would take 15 inches of soda vacuum to get it into your mouth.

If you were in outer space (perfect vacuum) then your vacuum gage would read 29.9" hg or 407" of water. Since hg is much heavier than water it takes more vacuum to pull it a certain distance up a tube.

15" of water is about 1.1" of hg. Not much vacuum.
07-11-2007 12:45 PM
REALGONEKATT HaHa... under water!!!!! inches of mercury makes infinitely more sense tho.....
07-11-2007 12:42 PM
REALGONEKATT Yeah man, those little darlins look good under there, sound nice too.....sounds alot like, dare I say; my old ford truck.....I didnt use the packs with the turndowns on the end,and I had about 2 1/2 foot pipes on the end...sounds the same tho, rock on....
07-11-2007 12:16 PM
454C10 They are not testing under water!!!

and they used 15" of water as the vacuum.

Inches of mercury (hg) or inches of water (h20) is what they use to measure vacuum. They are sucking through the muffler at some vacuum level and measuring the flow.

Just like they use pound per square inch (psi) to measure flow rate on a fuel pump. And they aren't putting weights on the fuel pump to measure flow.
07-11-2007 11:22 AM
Originally Posted by jimfulco
Did it say something like 15" of water or 20" or 28"? That's most likely a reference to how much pressure (or vacuum) was used to force the air through the muffler. More pressure will force more air through per unit of time. Vacuum is just negative pressure, and it's generally measured in inches of water ("H2O) or inches of mercury ("Hg), kinda like barometric pressure on the weather report is measured in millimeters of mercury (mmHg).

You'll probably see different flow rates out there for the same muffler, and it's probably due to different pressures used. There's not really any standardization in the industry, and until there is, there's always going to be some confusion.

Same deal for carburetor flow rates. Fuel injection systems and 4-bbl carbs are rated at 1.5"Hg while 2-bbl carbs are rated at 3"Hg. To add to the confusion, doubling the pressure does NOT double the flow rate, it only increases it by a factor of 1.414, which is the square root of two. So a 500cfm 4-bbl will flow 1.414 times as much air as a 500cfm 2-bbl.

Walker, parent company of Dynomax & Thrush, uses something around 20"H2O, which is pretty close to the same as 1.5"Hg, for their advertised flow rates. Vizard's rule of thumb (2.2cfm/hp) for required exhaust flow was also developed at that pressure.
i think it was 18" of water. i still dont understand why the hell they would test a car part under water especially a damn muffler! that makes absolutely no senses.
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