camz28arro

iTrader: (12)

I replaced my stock catback which had a hooker aerochamber welded into it for a SLP loudmouth II looking for a big hp gain considering my mods. After getting the catback, the first thing I noticed is the damn thing goes down to 2.5 inch ID in the muffler/resonator. Is this STILL restricting my exhaust and does anybody have LM1 vs LM2 dyno numbers. I'm probally going to replace the muffler with a quieter one too, any recomendations besides Borla XR1. Thanks.

Fbodyjunkie06

iTrader: (10)

Try a powerstick muffler I think these are the same used on GMMG exhaust.

camz28arro

iTrader: (12)

Should I get a Hooker aerochamber 3" catback since it doesn't go down to 2.5in, I searched and found some dynos where people were getting slightly less HP than expected and had the LM2 as their exhaust.

hitmanws6

iTrader: (20)

first of all, it does not neck down. it goes from 3 inches to 4 then back to 3 in the resonator. it goes to 2.5 where the tailpipes split. the LM1 or 2=cutout power. and going to the hooker will make you lose a few hp

hitmanws6

iTrader: (20)

they are not the same, they are more like a bullet

gavspurplez

iTrader: (6)

so i am running LTs, ORY cutout, and a rotted out 80 series flowmaster.
i was thinking about the LM2 to replace the cutout / muffler i have now......but was thinking of a 3 " i pipe, and 2 single chamber flowmaster mufflers before the tips....
eliminating the LM2 bullet muffler.....

and i going to lose power ?? LM2 over the cutout ? or the flowmasters over the Lm2 ?

can't have power loss !!!

StangeatinZ28

i dunno man, hooker's flow really good

hitmanws6

iTrader: (20)

with that setup, you will not lose power. the 10 series are straight through. you will see the gains of a cutout

hitmanws6

iTrader: (20)

yes they do, but you cannot beat the flow of a straight through catback. it wouldnt be much, probably less than 5 rwhp, but the op seems concerned with every possible hp

gavspurplez

iTrader: (6)

how about 1 single chamber flowmaster muffler in the i pipe......some say there may be ground clearance problems.... but if you can fit a bullet muffler, this should fit...

will it affect the sound if the muffler is that far forward in the system ? it shouldnt right ?

hitmanws6

iTrader: (20)

it will a bit. there will be ground clearance issues. the rumbler is already tight to the driveshaft, so you would have to mount it vertically, hence the ground clearance issue

gavspurplez

iTrader: (6)

aahhhhh, the driveshaft....

i see.... damn these cars.

camz28arro

iTrader: (12)

Maybe the LM1 does but the LM2 has only a 2.5in ID path through the muffler. I tried fitting a 3 inch OD pipe through the muffler and it wasn't even close to fitting. I know it goes down to 2.5 after the Y split though.

I think the Hooker and Loudmouth II would be the same HP if not giving a 5hp favor to the hooker. Plus it's not a ticket magnet when cruising. I AM concerned with every hp possible because it may not be much but it adds up in the end.

camz28arro

iTrader: (12)

Took the muffler off today to verify, HitmanWS6. Actual ID is about only 2 3/8 inches. I was wondering if anybody knows the ID of the Borla XR1 and if it soulds better as well. I cut the exhaust crossmember since the Y-pipe was resting on it and readjusted the exhaust and the sound is acceptable now.

breze84

LM2's are not going to make you lose power, They are a straight through design bullet muffler.... Your not going to see really any gains by swapping to a LM1.... Bullet style mufflers flow better than Chambered but chambered give a distinct sound like flowmaster ect.... Just my .02

camz28arro

iTrader: (12)

I'm still trying to convince myself about the muffler flowing enough air but am also trying to learn about exhaust flow, design, sizes ect.

If the 2.2cfm @ 20.4in/hp guideline is true, for a car that makes 400rwhp/.82 for drivetrain loss through an automatic, that is 487 rough hp. For less than 1% loss in power the car would need a exhaust that flows 1071 CFM. The 3 inch mandrel piping on all the aftermarket exhausts flow about 980-1000CFM, 3.25 inch or bigger would be oversized until the car makes over 560hp.

(these are very rough numbers)
2.5" dumps, 618hp
The mufflex 4 inch pipe will handle about 795hp.
3.0" dumps, 890hp
4.0" open collectors, 1600hp (Pro stock cars run these and make about 1500hp)

The stock cats flow 567 CFM combined, only flowing 258 non restricted horsepower. My 2.5 inch carsound cats were tested to 746 CFM to flow 339hp.

The loundmouth 2 in question should flow about 680CFM (2 3/8 ID). To the guideline, that is way too small, and flows 66 less CFM than the carsound cats. Compared to a completely non restrictive exhaust, this exhaust is costing me about 16-20hp, but over just a LM2 Vs 3.0" straight pipe it will be much less.


So LM1 vs LM2 should be at least 4-5 hp which is a lot considering all aftermarket exhausts add about 10-15hp. (33% more power) But not as much that I was thinking.

gavspurplez

iTrader: (6)

wow, thats way too much "science "

if someone is worried about losing 5 hp... then stick with what you have or do more homework before buying something different.

5 hp can't be that important... + / - 5 hp is acceptable...

if it was 25 i would be worried.

camz28arro

iTrader: (12)

I searched a lot before getting my catback but never saw anybody mension the very small inner diameter, I got the SLP LM2 because the hooker catback has been out of stock for months. If it's 5hp now, who knows how bad it will be restricting after my heads, maybe 10+, for hp that I thought I was paying for to have, its a big deal to me.

I just would like it to give at least the same numbers as the hooker would have gave me for less money.

camz28arro

iTrader: (12)

I finally took a picture to show you how restrictive the LM2 actually is. You can see the LM2 is less than 2 3/8 diameter and the borla is 3 in all the way through. If you changed the stock exhaust out because you thought it was restrictive, the LM2 is even smaller than that 2 3/4 piping.

camz28arro

iTrader: (12)

So I guess everybody that told me it wasn't costing me any horsepower has nothing to say now after seeing those pictures? Or maybe they themselves had LM2 mufflers and didn't want to believe it.