irocurpony8489

iTrader: (2)

Right now my car has a 4" mufflex catback with a single flowmaster muffler. I bought the car like this i cant stand the way it looks or the sound. Most importantly i care about the power. This week i bought a dynomax ultra flo bullet catback 3". My question is will i lose or gain any power on a bolt on 99 ls1 going from 4" to 3".

01ssreda4

iTrader: (96)

Probably not much if the muffler flows well.

irocurpony8489

iTrader: (2)

19418 is the part number it comes with a bullet style muffler looks like a copy of the slp lm2.

VandykeT/A

Probably not on a bolt on car but I assume you have a 3" to 4" merge. You could just put a 4" cutout right after the Y then reduce it back to 3" and run the catback. I did this on my 408 with a hooker catback. My 4" system was just to loud.

The Alchemist

iTrader: (19)

On a bolt on car, I doubt you would notice any hp difference between the two.

I'm running a 416ci, with an F1A procharger and have the Stainless Works 3.5" catback, and I might be losing 10-20hp at my hp level going through the catback. Granted, I'm north of 800rwhp, so 10-20hp is barely noticeable.

senicalj4579

iTrader: (41)

I did some research a while back on this. If you really wanna get technical the formula is PI x R x R = Area x 115 CFM / 2.2 CFM Per HP

The easy answer to your question is...
A 2.75” (stock) single system is good for a 310hp engine with zero loss…
A 3” Single system is good for a 370hp engine with zero loss…
A 3.5” Single system is good for a 503hp engine with zero loss…
A 4” Single system is good for a 657hp engine with zero loss…
A 2.25” dual system is good for a 457hp engine with zero loss…
A 2.5” dual system is good for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…


I never went the 4" route. My car still has 3". I wonder if I'm really leaving power on the table.

irocurpony8489

iTrader: (2)

I've read that too if that's hp at the engine then I guess any cam car would be pushing the 3" catback a limits

omc8

iTrader: (7)

If it has the flowmaster 3" to 4" merge , I would just keep it and get a quieter muffler .

MonmouthCtyLS7

iTrader: (6)

Flowmaster is one of the worst flowing mufflers around. As posted above with a na setup I doubt you'll notice anything but a sound difference.

01ssreda4

iTrader: (96)

Flowmaster makes about 1 million different mufflers. Citing specifics here would greatly increase the chances of sounding intelligent. If you are specifically referring to the flowmaster catback like most here do, then thats not even what he has. Actually reading and comprehending the thread helps you sound more intelligent. Or are you here to just repeat hear say info? It sounds like he has a 4 inch flowmaster, thats a race muffler and does flow well. I should know ive owned one. Flowmaster merge, yep owned that and still currently do. 4 inch exhaust, yep still run that, been running it for a couple years. Flowmaster catback, owned one of those too on a z28 I bought. People like you have owned one car with one exhaust and think your advice is the Bible. Sheesh.

Burken01

iTrader: (88)

no, you might even gain power.

4" is overkill on these cars Imo

Exhaust gas needs velocity as it cools off, stepping down the exhaust helps speed it up!

For example a c6 zo6 is 3" exhaust then necks down to a 2.5" inlet on the muffler, then even smaller to 2.25" outlet from the tips..

I know you don't have a zo6 but just illustrating the idea that biggest diameter piping isn't always the best answer.

redbird555

iTrader: (14)

^This is true. However a 4" catback flows roughly the same as a dual 2.5 system which comes standard on pretty much every v8 car out there. Velocity with no backpressure is the most important part of an exhaust but to actually get into a situation where thats a problem you have to go stupid large lol.

Op I would personally not go to a 3" I would keep the 4" and use a different muffler. However the part number you gave 19418 is for a dynomax system not a mufflex and by that it is a 3" system with 4" tips. Judging by the layout of the system I'd be willing to bet you'd gain power by putting th stock catback back on lol, it looks rather terrible and theres not much room for replacing the muffler unless you hack the back of the system apart

lemons12

iTrader: (71)

4" will make more power.

The merge design will have the largest impact.

Burken01

iTrader: (88)

Forgot the fbody cars are not true duals..

Sheesh, well hopefully that info helps someone searching for answers lol