My Formula is going to need a new exhaust sometime in the next few months, and I think I'd like to get something with a nice, louder-than-factory sound to it.

The rest of the car is all stock, with no performance modifications, and it will be staying that way. I rarely run the engine over 2500 RPM or thereabouts. So, I really have no need for high-end horsepower, just the low-RPM grunt.

My car has 2.25" or 2.5" stock exhaust, right? Most of the aftermarket stuff I see is 3", and the guy on the phone at Borla says I'll definitely lose some low-end torque if I install a 3" system.

Any comments?

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Chris

The guy is full of it, you will gain torque everywhere.

When I went from the factory exhaust to a full Gale Banks system on my LG4 (back in 1990), it amazed me how much torque it added from 2500 to redline. The car would burn rubber at will where the stock exhaust wouldn't. The system I used had a 3" y-pipe, 3" cat, and 3" cat back. Gave the car an easy 40hp and dropped times a full second (at least). Ran as good as 1987 350 cars back in the day (15.1 at 92mph).

Why Borla? Too expensive and not enough perfrmance in my book.

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Paul "chicks dig me" Huryk
Monkey Guy Racing
Living life 12 seconds or less at a time

Paul's home page

1984 Camaro 350 LG4 Best: 12.21s at 121.7mph
2002 Acura TL Type S

Since I dont have hardly any track experience, I'm gonna let someone else raise the BS flag on this one.

but if he RARLEY ever runs past 2500.....

the bigger you get then yes the more LOW END torque u might loose, especialy on ur engine. however i would recomend making sure ur Cat has something in it, if not then get a new one to help give u a little more backpressure. but the stock y-pipe and cat should be a good bottle neck.

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series Muffler added to Unkown CatBack, Ported Intake

http://www.geocities.com/david_angel_16

Any V8 engine, even a 305, will benefit from a 3" cat-back. Go for it. Just remember you will need to have your exhaust shop make up a 2.25" cat to 3" pipe adapter, not too tough. Or even better would be to replace it with a 3" cat as well.

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1991 Camaro Z28
5.7L 5-Speed (originally 305)
317 RWHP, 418 RWTQ
13.23 @ 107.62 MPH (2.10 60')
Southern California
Member: SoCal 3rd Gen F-Bodies
Member: SoCal F-Bodies
-=ICON Motorsports=-

How can you not go past 2500 rpm?
I go past 2500 rpm every time I take
off from a stop light..

he has a 5 speed, and maybe he likes to shift earlier..

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- David
88' GTA 5.7L TPI MODS---> air foil, K&N, Shift Kit, 180* therm, TB bypass, Gutted CAT, Flowmaster 80 Series Muffler added to Unkown CatBack, Ported Intake

http://www.geocities.com/david_angel_16

Yes, I do shift up fairly early, for the most part, usuall even when the Shift light tells me to. I'm not sure if I do it for fuel economy, or because I just recently got my license back, and I've calmed down a lot.

Anyway, my car FEELS like it's the most powerful car in the world when I drive it... but my best track time ever was a 16.8. So I figure it must just be the low-end torque that makes me think it's so powerful. But that's all perfectly fine with me... I just don't want the bigger exhaust to change all that.

So some of you are saying I'll gain torque, and some of you say that if I do actually lose some, it won't be much anyway. So I'll just not worry about exhaust size then.

Oh, and the car does have exhaust manifolds, and a factory-looking converter. But I have problem with replacing the cat... maybe it's a good idea to do it all at the same time. Any recommendations on what to buy?

Oh, and the only reasons I was thinking of Borla were the stainless steel (I'll be keeping the car until it's dead), the way you can adjust the sound, and the cool intercooled tips......... until I found out that you don't get the cool intercooled tips, which means that they probably won't get my business.

So I'm thinking about Flowmaster, and open to any other suggestions.

I need something has a cool burble at idle...but is still quiet (car will have remote start; don't want to disturb the neighbors with it). But when you stomp on the gas, it should sound nice and aggressive.

There is definitely some torque loss, although it appears slight to me.
however the loss of low end torque is EASILY offest by your gain in high end pull. Just my opinion though,

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ORIGINAL OWNER
92 Camaro RS, LO3, 5-spd, T-tops

Performance:
K&N Open Air Filter, Partial TBI mods, Edelbrock performer TBI intake, Fastchip Prom, Timing +4 degrees, Centerforce clutch, Xact 8mm wires, SLP 1 3/4" Headers (coated), Flowmaster Catback Exhaust, Richmond 3:42 gears, Torsen HD Posi
Sights & Sounds:
Alpine 8030 Alarm System, Valentine One Radar Detector (How did I ever drive without one?), Pioneer DEH 7450 Head Unit w/6-pack CD changer, Pioneer DEQ 7600 Sound Processor, 2 Kenwood KAC-846 Amps powering 2 12" Pro Red subs, 2 Pioneer 6x9 and 2 MTX 4x6 speakers. Spectre valve covers and accessories, Z28 grille w/aftermarket lights, MacEwen whiteface gauges
NEXT UP: the rest of the TBI mods & Suspension upgrades

When I switched to a 3in exhaust and 3 in cat on my Lg4 I had no loss of low end torque or throtle response at all.I picked up alot of mid and upper end power.This was with the stock exhaust manifolds still on though.When I added headers a few days back it was very different.I did lose low end power and throttle response with the headers installed.I knew this would happen but decided to put them on anyway when I had my sub frames welded on so that i wouldn't have to pay twice to have the exhaust shop reroute my ypipe.
If your Lg4 is stock by all means add a 3in cat converter and 3in cat back exhaust,you'll love the improvement in sound and performance.I would not recomend adding headers on top of that unless you modify your Lg4(cam,heads,carb tuning)or swap a larger motor in.The upper end gain is not worth the low end loss for a daily driver in my opinion.

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1987 Firebird Formula LG4,700R4,WS6,2.73 open rear
Current Mods:Flowmaster 3in. American Thunder cat-back,3in. Catco converter,L69 dual snorkel,K&N filter,roof console,Pioneer 1.5din cd player,BostonAccoustics 4x6plates,eclipse 6x9
ComingSoon! 350 crate motor(caprice),SLP coated 1 5/8 headers,edelbrock intake,edelbrock aluminum water pump

It all depends on what you do to your complete exhaust. Take a peek at my examples.

Car #1:SLP Y-pipe,no cat,3"Int,dual 2.5" out
Car #2:SLP Y-pipe,catco cat,3"Int,dual 2.5" out
Car #3:Stock Y-pipe,catco cat,3"Int,dual 2.5" out
Car #4:Stock Y-pipe,stock cat,2.25" Int,dual 2.25" out
All cars with factory manifolds.

Car #1 will have the least low end torque where #4 will have the most. A stock Y-pipe is enough restriction to still make low end torque but the high end power increase of a free flowing one should overcome that. It also depends what engine you have too. A 305 TBI is not going to have as much low end torque to sacrifice as a 350 TPI would. This is what I ran on my 1991 Formula 305 TBI it was great with little low end torque loss.
Factory manifolds, Larger y-pipe (one designed for an 88 350) 2.5" Catco cat, 2.75" Interemidiate, Dynomax muffler with dual 2.5" opposite side outlets.
Please do not flame here.




[This message has been edited by CODY BEHNKE (edited November 25, 2001).]

Cody, I want to make sure I understand right. This is what you said was on your '91 TBI Formula, right:
-------------------------------
Factory manifolds, Larger y-pipe (one designed for an 88 350) 2.5" Catco cat, 2.75" Interemidiate, Dynomax muffler with dual 2.5" opposite side outlets.
Please do not flame here.
--------------------------------

In that case, I have a few questions:

Does the larger Y-pipe bolt directly to the factory TBI exhaust manifolds?

Is the Catco cat a direct bolt-on, or is a universal-fit piece? If it is universal, how much trouble did you have fitting it? And did it match right up to the Y-pipe?

How did you attach a 2.75" intermediate to a 2.5" cat? Did you need an adapter?

I haven't seen many 2.75" intermediate pipes around, but a 3" shouldn't be a whole lot different, right?

Was the Y-pipe aftermarket, or from/for a factory 350 car?

How loud was the car at idle, and at, say, 2500-3000 RPM with the gas floored while accelerating? Would the car disturb a neighbor if idling in your driveway?

The Y-pipe was a OEM style from a 88 TPI car from Walker. The only problem was the right side down pipe, it needed to be cut and replaced with a piece with a small angle to it. As for the Cat it was a direct fit one from Summit, it needed to be expanded a very little bit to fit the y-pipe bt that was all.
The rest of my last exhaust was a Dynomax cat back #17495. The Dynomax cat backs come with either 3" flange(17495) or 2.50" flange(17493) but both are 2.75" the rest of the way back. I have had quite a few different systems used with the y-pipe/cat. combo above here they are.
#1 Flowmaster 80 Series with 2.5" Int.
#2 SLP Same side dual with 3" Int.
#3 Dynomax(#17495) with 2.75" Int.

The Flowmaster was the loudest, not crappy no exhaust loud but muscle car loud.

The glasspack oops I mean the SLP was a waste of time and money, totally wortless

The Dynomax isn't as loud as the Flowmaster but still had a very cool low gurgle and WOT rumble.

With the OEM style Y-pipe and cat. my car still retained it's unique Camaro/Firebird tone that is lost with most other header/cat removal exhausts.

Due to complete stupidity heres my sig

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Had a 1991 Formula WS6 With 49,000 miles 305 TBI 5-Speed Hypertech Chip,Hypertech Pullies, MSD Ignition,Dynomax Cat-back,Firehawk SZ50ep's, etc..... A stupid drunk totalled this one out on Nov.3,2001 My new toy
1995 S-10 SS Vortec 4.3
Hypertech pullies and Power programer, K&N Filter,Dynomax Cat-back,BF Comp T/A HR4's

[This message has been edited by CODY BEHNKE (edited November 25, 2001).]