if you have ever gone from a chambered muffler to a straight through muffler, and gained or lost performance, please post up your gains/losses. i'm having a debate on another board and need at least 30 (according to the central limit theorem) scenarios so i can form a proper hypothesis and interval test. depending on where this goes, i may use it as my senior paper, lol.

thanks for the help guys!

Ps, please provide DA data for the runs so I can standardize the info. I put this in this section because it directly correlates to drag racing. it should be noted that for this test, only n/a cars/trucks will be considered as a turbo or blower might skew the data.

 

so i'll start, format should be as follows

Muffler type: Moroso spiral mufflers
DA: 2400'
1/4mile mph: 121.8
1/4 et: 11.31

Muffler type: Dynomax Bullet
DA: 3200'
1/4 MPH: 122.4
1/4 ET: 11.26

i will then take your data, and correct it for DA to sea level using dragtimes da calculator, which is universally accepted as accurate. here's the link:http://www.dragtimes.com/da-density-...calculator.php
i will use the stock/midly modified results across the board for standardizing.

new corrected times:
Muffler type: Moroso Spiral
1/4 MPH: 125.4
1/4 ET: 10.99

Muffler type: Dynomax Bullet
1/4 MPH: 127.4
1/4 ET: 10.83

so the gains seen in this scenario was +2mph and -.16 in ET. once i get 30 scenarios, i can then apply the central limit theorem that says if the mean values of the sample are normally distributed, then the mean values of the population are normally distributed. i can then do some hypothesis testing to see if all mean's are essentially equal, and if i have any outliers (like the one pass mentioned in another thread...lets see if it's mathematically believable).

 

Interesting project!

Sorry, I dont have any data for you.

Just out of curiosity , how many runs did you do with muffler? and then you just took your best time?

 

yes, i'm just using my best time for each, trying to keep just the muffler being the changed variable. it's pretty tough getting data together for this actually, lol. i think i had 6 passes or so each night one muffler to the other. i'm comparing DA's, and correcting et/mph for sea level, then converting to HP based on weight and mph. there are so many variables that it would take several months to get this straigth if i didn't assume some things as constants. i wish i had thought of this 6 weeks ago, as i'd go way further in depth, but with only 2 weeks left, i need to just get my data and start going, lol.

 

Wish I could help Matt. Never ran the dang 89 once I went from 1 chambers to bullets before I wrecked it. Would have been 1/8th mile anyway. But I also swapped clutches. Would have made the data wrong.

Good luck, will be in for final results.

 

While I have no first hand experience with this (other than my research into exhaust pulse theory) but I know of one well written article describing the effects of either style of muffler. Very brief and included in the latest edition of Vizard's SBC book.
Apparently there's a lot to be gained (or lost) with attention paid to this area.

 

Skinny, do you have a link to this book? Sounds like it'd be a good resource for more info.

 

Herer's a link through Amazon.



(Why the link is shown twice I can't explain. There's only one book)

I've scanned a section from the exhaust chapter which I think is relevant to your research.

 

I'll check it out, thanks man. Currently, I have enough data to do a nom-parametric method, whiz is what I may do. If not, my paper will be on some sort of sports probability, but I'll still do the hypothesis testing on here to find out what we're looking at.

 

From 5 years ago:

Flowmaster 80 series crossflow (3" in, dual 2-1/2" out), ran a best of 14.61 @ 93 MPH, worst of 14.88 @ 93, with some 14.7's @ 94. Best 60' 2.11. Calm winds, DA 8200', 5/8 gas tank.

A week later, with Magnaflow single 3" in/out, rest of the exhaust and car the same. First run DA 7200', 1/2 tank gas, 5 MPH headwind, ran a 14.33 @ 95.17. 60' 2.07. Next TT, DA 6800', 5 MPH headwind, 14.31 @ 95.47 MPH.

 

awesome! thanks tim! how much did it weigh?

 

Wow, not sure. I think around 3500 at the time.

 

ive been doing alot of research myself on the exhuast setups this might help with your project

http://ls1sounds.com/faq.htm

look at the bottom of the page they have dyno chart showing power gains or losses with different muffler

also decibl read outs at idle and wot

 

Is it muffler construction i.e., glass pack (like a Cherry Bomb) vs chambered (like a Flowmaster), that you're interested in as a comparison or muffler cfm?
In 57Kid's example, it appears to be a flow related increase in output that produced the numbers he's presented. If I understand correctly, a Flowmaster and a Magnaflow are roughly of the same design (internal chambers or baffles) hence my flow related comment. The results he experienced are similar to my experiment with a single cutout located directly before my stock location muffler. The increased flow achieved in bypassing the muffler saw almost a tenth reduction in et and over 1 mph gain in last years 1/8 mile testing.
8.124 @ 83.82 1.81 60’
8.070 @ 85.14 1.81 60’ 3700 lbs race weight.
This is different from what might result from a glass pack being installed in the same location. The glass pack acting as more of an extension of the full exhaust system thereby changing the pressure wave characteristcs as seen at the exhaust valve and the resulting "tune".

 

Why do you say the test can't be with a supercharged engine? I'm pretty sure the exhaust system has no idea what is going on in front of the intake valve.

The main thing to know about exhaust systems is that if it flows good at high rpm, it won't flow good at low rpm. And if it flows good at low rpm, it won't flow good at high rpm.

There's no such thing as a perfect exhaust system.