Intermediate Pipe Diameter

[nwilson44]

Hey guys! Hope everyone had a great Christmas! I wanted to ask something that may have been answered already but I wanted to be specific to my set up because I am finishing up my exhaust.

My car is a 2001 and I have the Ceramic coated Pacesetters and their 3 inch y pipe, and magnaflow catalytic converter. It is currently connected to the stock cat back.

What I know for sure is that the stock cat back is going in the trash! I have a Borla XR-1 Muffler coming in (unless I have some evidence not to get it) and I am having issues deciding on a diameter of the intermediate pipe. Originally I thought a 3 inch is perfect since it matches my y pipe and cat. However I have someone telling me that that may be too big for the V6, and that the V6 doesnt move enough air for that big of a pipe. They recommended a 2.5. Any objections? Will I rob my power and torque with a 3 inch!?!??! Help?!

[FIREBIRDV6RAGE]

There is a whole discussion I'm talking about page after page on here or full throttle v6 of this myth. Its never been proven but people say they feel the differences between having the 2.5 and a 3" system. As for me I couldn't tell you since my car is runing stock exhaust other than the flowmaster muffler.

Sent from my SGH-T999 using Tapatalk

[nwilson44]

Re: Intermediate Pipe Diameter

There is a whole discussion I'm talking about page after page on here or full throttle v6 of this myth. Its never been proven but people say they feel the differences between having the 2.5 and a 3" system. As for me I couldn't tell you since my car is runing stock exhaust other than the flowmaster muffler.

Sent from my SGH-T999 using Tapatalk

I read all the theory behind the smaller vs larger but it was all generalized. I wanted to hear from some people that have tried and tested it on their cars. I dont know if I should go with 2.5 or 3 inch. I really wanted to know before putting on either or.

[FirebirdGT]

Re: Intermediate Pipe Diameter

Stock size is 2.25" for V6 and 2.75" for V8. Aftermarket Cat-backs use 2.5" for V6 and 3" for V8.

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[nwilson44]

Re: Intermediate Pipe Diameter

Stock size is 2.25" for V6 and 2.75" for V8. Aftermarket Cat-backs use 2.5" for V6 and 3" for V8.

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So for the 3.8, the 2.5 is probably the best way to go?

[nwilson44]

Re: Intermediate Pipe Diameter

"Intermediate Pipe

The intermediate pipe carries the gases from the cat to the muffler at the rear of the vehicle. The stock one on the 3.8 is 2.25" in diameter and is also a site of great loss of flow. High flow I-pipes use larger diameters and Mandrel bends, which are the exact same diameter through a bend. (Imagine taking a pipe and bending it 90 degrees--the interior diameter decreases in the bend, right? Mandrel bending prevents this, the metal is actually molded as a bend.) The larger diameters available are 2.5" (124% of stock cross-sectional area) or 3" (178% of stock cross-sectional area, usually sold as upgrades for V8 models but a great choice for V6 owners). Intermediate pipes are usually not sold seperately; rather, they are sold together with a muffler and tips as part of a catback exhaust system.

Be warned: muffler shops often sell "high performance" intermediate pipes seperately but these are not Mandrel bent--they are straight pipes that are bent by a machine at the shop. Mandrel bends are a requirement for high-performance use. Do not buy a custom bent pipe if you care about performance. They are not equal, regardless of what the muffler shop mechanic tries to tell you."




This is what our site says about them. I am just having people tell me that the 3 inch is going to kill my low end torque. I just wanted to know what I should do for the best performance.

[flamingchicken]

Re: Intermediate Pipe Diameter

I ran 3" for a while, then went back to 2.5 inch. I saw no increase in the top end from a 3 inch exhaust but did notice that it was a dog until about 3500 rpms. My last setup was 2.25 inch x-pipe, and I loved it. With the cam I was running I revved all the way to redline and felt it make power all the way.

[nwilson44]

Re: Intermediate Pipe Diameter

I ran 3" for a while, then went back to 2.5 inch. I saw no increase in the top end from a 3 inch exhaust but did notice that it was a dog until about 3500 rpms. My last setup was 2.25 inch x-pipe, and I loved it. With the cam I was running I revved all the way to redline and felt it make power all the way.

So the 3" took your low end torque and didnt pay you back with top end power?! Do you think the 2.75" mandrel bent, would be a good happy medium or the 2.5" is the best?

[2.8 Bird]

Re: Intermediate Pipe Diameter

Probably over ten years ago someome did a test on 3" catback vs stock diameter and cleraly showed a 8 hp gain but tq.pretty much stayed the same.

If your car is heavily modified especially with force induction then you'd be better off having this. But if your car is close to stock then go with a smaller.diameter.

[nwilson44]

Re: Intermediate Pipe Diameter

Probably over ten years ago someome did a test on 3" catback vs stock diameter and cleraly showed a 8 hp gain but tq.pretty much stayed the same.

If your car is heavily modified especially with force induction then you'd be better off having this. But if your car is close to stock then go with a smaller.diameter.

Okay so with full bolt ons and a custom tune 2.75 is best?

[fbodyrs96]

Re: Intermediate Pipe Diameter

I like my 2.5" I could feel a little noticeable difference over stock and gave it a little better tone. you can get one form rockauto shipped for $100

Walker part # 47696

then add your muffler of choice.
mine Borla pro xs

[nwilson44]

Re: Intermediate Pipe Diameter

Okay thats great to know! anyone with the 2.75" pipe?

[2.8 Bird]

Re: Intermediate Pipe Diameter

Okay so with full bolt ons and a custom tune 2.75 is best?

Imo I would just go with 3" since it's only a quarter difference and it's only a single pipe. It's already dyno proven and plus you'll get more power at your midrange rpm all the way to redline. It'll make your car sound better too.

[nwilson44]

Re: Intermediate Pipe Diameter

Imo I would just go with 3" since it's only a quarter difference and it's only a single pipe. It's already dyno proven and plus you'll get more power at your midrange rpm all the way to redline. It'll make your car sound better too.

That was my original thought. But guys have been saying that 3" is too much for the 6 cylinder, and I'll loose bottom end and mid range, and I am afraid of loosing either. I want some top end too, but I dont want to loose anything.

[ssms5411]

Re: Intermediate Pipe Diameter

I like my 3" pipping.