HILL_SS

iTrader: (4)

I have some questions on Exhaust Pipe Size with a Blower for a STREET car...

Now I have been talking with a buddy of mine who is well respected car enthusiast in my area who also runs many well Horse Powered f-bodies...And he is saying that I am...What he calls "Constipating" my engine by running 2.5" TD with a blower. Which I am currently running 10.5 psi out of a D1SC Procharger

He is telling me by going up to 3" or even 3.5" TD I could see as much as 30 to 80 "At the Engine" HP

Now I have been running the 2.5" for clearance reasons thus far...but now that the car is not my daily driver anymore (more of a weekend warrior)...I have been looking into some of the 3 or 3.5" oval piping that some exhaust companies offer now. To keep as much clearance as possible, but gain power.

So my question/questions to all your Blower FI guys is what size of exhaust piping are you running on your "STREET" cars? My car isn't much of a strip car, so I'm wanting street car opinions ultimately...

Do you believe the numbers he has given are possible by making the exhaust pipe size change? (now granted i understand get the air in, get the air out it makes sense that power will increase, but by how much?)

The reason for the questions is I know to get either one of those setups done in True Dual/X-Pipe like my current setup which will go out the rear into my CME dual/dual tips will cost a pretty penny...Will it be worth it?

And finally I just want to cure my curiosity of what he has told me, and confirm a round-about number in you guys opinionated HP gain, per $ spent on this project...

Obviously if these gains are possible it would be more than worth it. I'm just wanting to get some opinions before I spend the money on this kind of project...Sooo with all that being said...POST AWAY!

Lastly I am including a POLL to include votes/opinions on what I should do!

LS1Silverado05

iTrader: (41)

I could see going to maybe 3" duals...but I cant imagine the 2.5s are killing you 80HP bad....

How about just running a couple E-Cut Outs in what you have...?

stevied916

iTrader: (30)

When my setup is finished it will be 3" to 3.5" Y with race muffler. I think it will be fine. 3.5 is a little excessive. Dual 2.5" is not going to cost you much at all over 3"

ZLEEPER

iTrader: (24)

With a F1a on a 408, we were doing 4" from the y back, but had to reduce to a 3.5 for clearence over the axle.

NightMoves

From longtubes to muffler (no Y pipe)
Two ea 2-1/2" in two ea 2-1/2" out MagnaFlo W/X pipe (true duals) with 2 DMH 2-1/2" wide oval cut outs at end of long tube headers = no recordable difference in torque or HP with cut outs open or closed on dino pulls. 5.3L, 112 MagnaCharger, 9.5lbs+ boost, 460lbs T & 490 HP. Prior to this setup Y pipe into 3" single then into 2 2-1/2" in 2 2-1/2" out Flomaster @ rear of car = about 20 HP gain with same cut outs open.

I hope the explanation makes sense.

pwrtrip75

iTrader: (8)

Thats what i was going to ask. Why not do a single 4" all the way back? Way easier than duals of a decent size. I put a single 4" on my fiends car, 4" over the axle and all...plenty of room.

BigRich954RR

iTrader: (1)

I would try doing one 4 inch all the way back.

F1C here on a 364 from stock dual 2.5 to dual 3inch i picked up a lot but it was a stock 2.5 on before. with a dual 3 inch im still seeing a little back pressure

BlkHwk

iTrader: (8)

It's nice to let them breath as much as possible. I doubt your losing 80 Hp. I also have 4" single over the axle. My biggest ground clearance issue is my tunnel mount for the torque arm. It would be interesting to dyno it now and then upgrade,tune and see what you get.

HILL_SS

iTrader: (4)

I would like to see pics of you guys that have Single 4" all the way out the rear...

Also if you guys have some sound clips...I really like the tone of the X-Pipe (Eliminates all the rasp and drone from the y-pipe) but I also haven't heard a 4".

Also here is my only battle with doing 4" is I have the CME on my SS... may be very difficult to incorporate that and make it look right...My car is a street/strip/show car...must keep a clean look along with make gobs of power...

Here is a quick shot of the rear and what I am working with...

HILL_SS

iTrader: (4)

So it also sounds like you guys agree that there is power to be made, but not the 30-80HP I was told...Any other opinions on that???

Also Single 4in has been the most suggested way to go by the post....but 3in TD through the POLLS...

I will let the thread cook a little longer and see if the posts/POLL stay the same...

My numbers by the way at the rear through a 3400 Stall are 521RWHP with the 2.5" TD's...

Jimmy P

iTrader: (177)

I wonder if someone can do a true dual 3.5" in setup oval piping. The collectors on my Kooks headers are 3.5", so I would have to step the rest of the exaust down just for clearance issues.

HILL_SS

iTrader: (4)

i wondering the same thing if it can even be done...I was thinking it could be 3.5" up until it goes over the axle may have to be 3in over and back to 3.5" out the rear???

HILL_SS

iTrader: (4)

Anyone have any 4in exhaust pics or sound clips?

ZLEEPER

iTrader: (24)

Did those of you that did 4" all the way experience or have you checked to see that the pipe has not been crushed at all? It looked really tight when we mocked it up on my car. ??

BlkHwk

iTrader: (8)

Yes I have checked and no it hasn't been crushed.

Here is a little vid of my car from last may. This is 4" mufflex with spintek muffler. It's best if you click on the hq button and watch it that way.

http://www.youtube.com/watch?v=C1C2CY9qpIs&feature=user

HILL_SS

iTrader: (4)

Sounds good (very deep tone)...What are the specs on the cam you are running...(if you dont mind sharing)

So are you 4in off the header back? If so are you using oval piping under the front driver side floor pan? Seems like clearance would be an issue...

BlkHwk

iTrader: (8)

Kooks header 1 7/8" stepped to 2" 3.5" collector, Kooks 3.5" "Y". Yes it is oval shaped on the drivers side. 4" out of the Y pipe. Mufflex 4" intermediate pipe. When I got the intermediate pipe it came with a reducer welded on the pipe where it connects to the Y. I had to cut that part off and make a new one to attach to the Kooks Y pipe. The cam is 242 248, 610 615, 115 lsa.

Inspector12

iTrader: (29)

I was running a single 3.5 to a 4" mufler, but now a 4" all the way back. Personally the dual 2.5's arent killing you at your power level yet, but I do think you are getting close any more power(600+) and I would probably do something different. JMO. I made 700rwhp on a single 3' so you have to look at surface area not just the size of the pipe etc...GL.

WS6HUMMER

iTrader: (19)

4" to the torque arm crossmember and then dumps here.

HILL_SS

iTrader: (4)

Yea those are some good RWHP numbers on a single 3in...

And speaking of "surface area" I saw this in another thread that may apply to this...

Quoted from: jmilz28
For comparison, let me give you rough cross sectional area, which indicates maximum flow:
single 3" - 7 square inches
single 3.5" - 9.62 sq in
dual 2.5" - 9.8 sq in
single 4" - 12.5 sq in
dual 3" - 14.1 sq in