Is a 4" exhaust necessary...

With a T-Trim and a 355, will a 3" lose much over a 4" exhaust?

IMO you can make alot of power out of a 3-inch. I making over 700 rwhp out of my 3-in ATR catback. :) I have heard of some people losing some bottom end power but gaining alot up top when going with a 4 inch exhaust.

Originally posted by IDOXLR8
IMO you can make alot of power out of a 3-inch. I making over 700 rwhp out of my 3-in ATR catback. :) I have heard of some people losing some bottom end power but gaining alot up top when going with a 4 inch exhaust.

What setup do you have? I'm in the process of building a forged 355 for a t-trim. I bought a 4" and lost some bottom end with my n/a 355 but I can program that back in. I just want to know if the 4" is is necessary cause my car is slammed and the 4" sux for clearence. I'm either going to build a 4" catback with oval tubing or go back to a 3" catback.

Originally posted by solid95z
What setup do you have? I'm in the process of building a forged 355 for a t-trim. I bought a 4" and lost some bottom end with my n/a 355 but I can program that back in. I just want to know if the 4" is is necessary cause my car is slammed and the 4" sux for clearence. I'm either going to build a 4" catback with oval tubing or go back to a 3" catback.

Check my sig. :)

Originally posted by IDOXLR8
Check my sig. :)

Oh yea...DUUUUUHHHHHHH :D

How much boost are you running and what nubmbers did you make?

My car runs 10.40 at 133 mph though a 3" Hooker Aerochamber Cat-back. I detached the exhaust from the 4" Mufflex Y-pipe and gained nothing, indicating my 3" is fine for the power level.

. . . PROVIDING you have a good muffler (not Mufflex or Flowmaster).

Mike

I gained 10rwhp on an NA cam'd 350 from the Borla muffler to the wideopen plate.

Get a 3" and put a cutout on it - I think it is the best compromise. Unforunately, its "look at me" loud :mad:.

Ryan

Originally posted by engineermike
My car runs 10.40 at 133 mph though a 3" Hooker Aerochamber Cat-back. I detached the exhaust from the 4" Mufflex Y-pipe and gained nothing, indicating my 3" is fine for the power level.

. . . PROVIDING you have a good muffler (not Mufflex or Flowmaster).

Mike

That's VERY good to know. I've had a Hooker catback for the last 4 years and that's what I am going back to :D . Hopefully I'll have the same good luck you had :bow:

Originally posted by engineermike
My car runs 10.40 at 133 mph though a 3" Hooker Aerochamber Cat-back. I detached the exhaust from the 4" Mufflex Y-pipe and gained nothing, indicating my 3" is fine for the power level.

. . . PROVIDING you have a good muffler (not Mufflex or Flowmaster).

Mike

Damm Nice numbers :) What is done to your suspension? Also what are you running for slicks?

We did 3" to 4" testing on the dyno. Of course its not on my f-body but either way hp is airflow, so this would replicate itself on our cars in the 700rwhp range. Anyhow the link is below...

http://forcedinductions.com/ipw-web/bulletin/bb/viewtopic.php?t=6

I think turbos gain A LOT More from a totally free exhaust than a supercharged vehicle, given that they need that pressure differential to AID in the flow through the turbine.

Now... I did gain 29rwhp from closed plate to open plate borla on my 383 S -trim... I did from 457-486 and eventually did 501.

Originally posted by IDOXLR8
Damm Nice numbers :) What is done to your suspension? Also what are you running for slicks?

The suspension is generally stock, except for tubular panhard rod and tubular LCA's. I ran with both sway bars connected.

I'm running 16" salad shooters with 27 X 10 - 16 ET Streets with tubes in the back and 17" SS wheels in the front.

My converter is a Vigilante "0" pump (2800), but it probably flashes to around 4000 due to the torque output of the blown 383.

Also, I'm the guy you hear about running mid 10's with a 7 1/2". It has 3.42's.

Mike

Turbos will gain somewhat more then a S/C or N/A, but that proves all the less that a 4" exhaust is not needed.

Jose

Originally posted by engineermike
The suspension is generally stock, except for tubular panhard rod and tubular LCA's. I ran with both sway bars connected.

I'm running 16" salad shooters with 27 X 10 - 16 ET Streets with tubes in the back and 17" SS wheels in the front.

My converter is a Vigilante "0" pump (2800), but it probably flashes to around 4000 due to the torque output of the blown 383.

Also, I'm the guy you hear about running mid 10's with a 7 1/2". It has 3.42's.

Mike

Impressive :) Is the car a light weight car?

I'd love to do a true dual setup or go a 4" and am convinced there would be some significant hp to be gained, but there is just no damn room for it under my car.

Rich Krause

What about going to a 1 7/8 headers?? ?a lot of the ls1 guys are running them...

Originally posted by The Highlander
What about going to a 1 7/8 headers?? ?a lot of the ls1 guys are running them...

It probably would be pointless into a 3" exhaust.

Rich Krause

Oh yes obviously... but on a 4" exhaust...

What about the borla XR1? does it fit? worth it?

Originally posted by IDOXLR8
Impressive :) Is the car a light weight car?

It's lighter than my Lightning. :D

I'm guessing around 3750 lb. It's a '95 Z28 with T-tops, add a roll bar with door bars, a supercharger, an intercooler, a driveshaft safety loop, and a water tank in the trunk. It's a pig.

The only thing that reduced weight is the tubular K-member (-25 lb, maybe).

Mike