Can you do this "Y" pide install and a 3" pipe to the muffler without changing anything else with the factory exhaust, and would it make any performance gains?

 

Honestly.
I don't think you would get that much of a benifit from this.
If you are going to got through the trouble of changing the 'y' then go all the way & do the muffler..

Joe T

 

ChadHick88,

I have to agree with Joe T.

Remember that you're trying to exhaust 2 pipes from each side of the engine that are both 2.5 inches in diameter. But dumping both into a Y-pipe with a 2.5 inch diameter outlet won't gain you a thing.

Think "outlet" capacity. A 2.5" diameter outlet pipe has an area of 4.91 sq. inches. (area of a circle: [Pi (3.14) x radius squared]

The area of a 3" outlet pipe is 7.07 sq. inches, or 2.17 sq. inch, 44% less restrictive than area of a 2.5" pipe.

My recommendation is to install the 3" outlet Y to a single 3" aftermarket exhaust system, or install a 2.5" X-pipe to a dual 2.5" aftermarket system.

 

The 3" exit Y-pipe and 3" pipe going to the muffler would do nothing at all, it's immediately reduced back down as it enters the factory muffler(2.5"inlet); it only changes the restriction area. If you want to improve the factory exhaust system, change the muffler only; it only flows approximately 200cfms. The factory 2.5" PIPE can easily handle a slightly modified modular engine.

 

this is what I did. I left the exhaust system stock, but replaced the muffler with a Flowmaster 50 series. Even the exit pipe is stock. I opened up the front end with a K&N mounted right onto the tube and walla, I have much more throttle response and the sound is great.
My gas mileage has improved as well.

 

Hey Peter1, how is the sound with the stock pipes and FM50?

I'm thinking of just replacing the muffler as well.

 

Max,

If I am planning to put in an FM Delta Flow 50 on the truck SI/SO 3" (I think they make that), wouldn't it also make sense to replace the Y and pipe back at the same time? Seems like the added cost is small. I agree that the 2.5" pipe isn't a problem but that Y sounds like it has issues.

Thanks,

Chuck

 

I did the same thing as deep6. It sounds good. I get a little drone around 60, but I can't say that I hang around 60 too often. I know some people that can't believe that the sound comes from stock pipes and just an aftermarket muffler. Well worth the $50 plus change to make the switch.

 

deep6blue -

I really didn't want to have bigger pipes, because I think that is where backpressure is lost which might result in less pulling power for my trailer.

I just wanted to maximize airflow in and out and the stock muffler is way to restrictive and large too. If you are going to put one in, then do the airbox mod in tyhe Technical Articles section of this site for sure. You don't want to do just one without the other.

The sound is great. It's louder than stock but only if you step on it. I think it sounds like a truck now, but its definately not too loud. I would go with this one, unless you want it like stock, then get a 70 series.

I'm also getting a Gale Banks Trans-Command Automatic Transmission computer this week to improve trani shifting.

Peter

 

"pipe back" is a bit confusing. Are we talking just a 3" intermediate pipe or a complete 3" system? I take it that you mean a 3"exit Y-Pipe, a 3" intermediate pipe, and a 3" in/out muffler with the stock tail section at 2.5". If so, it's a complete waste of time; you're still reduced down, only farther back. To fully utilize any 3" exhaust part, there must be no smaller sections anywhere. This would function just like a 2.5" system. To make matters worse, the press bent factory tailsection's tight curves reduce it below 2.5" functionally.

 

If you're looking for advice, Max Mitchell couldn't have stated it any better.
There will not be much of a return on your dollar if you just install a larger aftermarket muffler and leave the stock upstream and downstream pipes. Granted, the sound will improve because of slightly less baffling in the aftermarket muffler, but the outlet pipe to the tail is limited due to flow capability based on it's diameter. By installing the full 2 1/2 inch pipes from each bank of the engine into an aftermarket Y pipe on the front and then a 3 inch coming out the back of the muffler to the tail, you'll gain a lot more in performance and some MPG gain over the life of the system......and with the total upgrade, you should have a faster return on the money spent on gas and greater satisfaction of having the extra horsepower when you need it.
If anyone is concerned about loss of low-end torque by adding a full aftermarket system including the Y-pipe, think about how often you are towing versus when you're not. Since adding my FlowMaster Y, which was just after my SuperChip install, I have no doubt about the towing capabilities of my truck. If needed, the overdrive can be disengaged to stay up with traffic if I'm towing a 6k lb trailer.
As a side note, Gibson Performance recommended sticking with a single 3" SideSwept if you tow. Going to their "true duals" would result in too much low-end loss for towing. That's the reason why I installed the SweptSide in addition to being quieter at cruising speed (no droning noise).