Jump to content
Sign in to follow this  
dcass72

Exhaust Question

Recommended Posts

Alrighty, getting ready to do some exhaust work, as the muffler has officially fell apart on my 96 pathy. My question, is there any reason not to go with a bigger diameter pipe compared to the stock system? Also, true duals or 2-into-1? Has anyone noticed a loss in MPG by going bigger? Thanks for any info!

Share this post


Link to post
Share on other sites

Without getting into a bunch of technical jargon. The factory dual 1.75" into the muffler provides more than enough flow for our trucks. The factory dual 1.75" pipes have the same flow rate as a single 2.5" pipe. (Actually 0.639 cfm less).

To keep the same flow rate for a dual in, single out muffler. Would be to find one that has dual 1.75" in, 2.5" single out. But a single 2" out is fine.

Here is a chart to show you:

tubingsizeversusarea.jpg

  • Like 1

Share this post


Link to post
Share on other sites

Any preference of muffler brand? What sounds good?

Share this post


Link to post
Share on other sites

Through all my years doing hot rods. I have had Napa, Dynomax, Thrush, Flowmaster, Magnaflow, Borla, etc etc mufflers. By far my favorite has been Magnaflow mufflers. They seem to have a nice idle tone, that is noticeable but not obnoxious. Yet when at full throttle. Open up nicely and have again, a nice tone. Plus with most others I always had drone and rasp sound problems.

  • Like 2

Share this post


Link to post
Share on other sites

While I don't have the same amount of experience with exhaust, I agree with the above. My first Pathy had a good sound with a cat back system and a Magnaflow, but not too loud and obnoxious. My current header/custom system with a Flowmaster sounds great at idle/low range but gets loud and raspy at 3k+ rpm.

 

B

  • Like 1

Share this post


Link to post
Share on other sites

I cut my stock exhaust off. It just dumps off the header. Sounds awesome on the vg. ESP when you drop a gear and give it.

Share this post


Link to post
Share on other sites

I cut my stock exhaust off. It just dumps off the header. Sounds awesome on the vg. ESP when you drop a gear and give it.

I had it like that for about a week, but was a bit much for me. I ended up getting the stock resinators (short glasspacks) and tips off a 2012 SS Camaro and used those as mufflers. Actually came out pretty well, has a great tone at idle, and not too raspy on accel. I'll try and post some pics tomarrow.

Share this post


Link to post
Share on other sites

the muffler on my 01 is kinda rusted just thiking of getting a muffler and double rolled tip to give it a lil but of agression but i have to many projects on this thing so that is total back burner

Share this post


Link to post
Share on other sites

Can we run true duels on these? Won't hurt anything?

Share this post


Link to post
Share on other sites

Can we run true duels on these? Won't hurt anything?

I did on mine, haven't noticed any issues, but did get a little better acceleration I feel. Gas mileage is about the same, which is kind of a bummer.

Share this post


Link to post
Share on other sites

tubingsizeversusarea.jpg

 

It's not possible to compare the areas of the pipes to compare the flow rate. There is friction along the walls of the pipes, and a single 2.5" pipe has way less wall area (29%) than two 1.75" pipes.

 

The diameter of the primary pipes is very sensitive (the manifolds) but after the cats (the secondaries), it is much less so. Generally from there onward, bigger+shorter is better.

Edited by pathfounder
  • Like 1

Share this post


Link to post
Share on other sites

The theory craft of exhaust flow rates has been done over and over. Easy to find on hot rod forums. Especially Mustang, LSX engine forums etc. <br />There is actually a formula to calculate it the flow rates of pipe comparisons. But I dont know it off the top of my head. To say the wall friction will make that much of a difference is null. The amount of friction is next to nothing. <br />Where you get the greatest difference is the velocity of the exhaust gasses as they exit. Which needs to be balanced with the needs of the engine. <br />Check out the exhaust section of LS1tech.com<br />Tons of information there on exhaust and its corresponding theory craft. With proven results showing gains and losses. <br /><br />Sent from my Galaxy Nexus using Tapatalk 2<br /><br />

Share this post


Link to post
Share on other sites

I didn't say that a 29% increase in wall area means a 29% decrease in overall fluid flow, but to say that the wall friction doesn't matter is completely wrong. Anything that moves past anything else will encounter resistance. If you look at velocity profiles of pipes, the velocity is always greatest in the centre, and slowest at the wall.

 

fig3_9.gif

Share this post


Link to post
Share on other sites

Nah. No popcorn needed.

His point is valid. Just that IMO the size piping needed for our engines 3.0/3.3/3.5 the difference is close to null. Considering we dont need full 2" dual for proper flow.

 

Getting a little technical. But has anyone ever determined the Volumetric Efficiency of our engines? Cant imagine its much higher than 80% at best.

 

(Someone needs to shoe horn a LSx engine in one of these!)

Share this post


Link to post
Share on other sites

:jacked: Well, kind of...what do S/C Xterra's use? I mean, they can't be using piping much larger than what we

 

 

have, especially given the "modest" HP bump. If one uses the stock configuration with 2" piping all the way back from the headers, (assuming one gets headers) then it should provide a decent increase without losing much torque, if any.

 

In my 4-bangers, I always changed the puny 1 7/8" for a 2.5" from the header back and although I did lose some low-end grunt, the gains were well worth it. Also, believe it or not, I did see an increase in MPG while cruising on the hwy. (Note that I said cruising, please) :lol:

 

Having said that, In this truck, I would not want to lose the low-end grunt and would be happy with just a tiny bit of increase at higher rpms. So, I'm still voting for stock configuration with 2" piping. Magnaflow muffler and either no resonator out back or a cherry-bomb, just to quiet things down...a bit.

 

I am currently running stock everything, except for the end resonator. Just straight piped that one and the sound is great. Not loud enough to hear while driving but loud enough to hear it at idle and low speed cruising in alleyways. :laugh:

Edited by Bluewulf73

Share this post


Link to post
Share on other sites

so not trying to jack his thread but if i was to run a single inlet of 2" to a dual outlet of 2" would i be ok or no?

i would be runing the stock 1.75 pipe to the 2" inlet of the muffler then running 2" for the tail pipes

Share this post


Link to post
Share on other sites

I realize I have a different motor (VQ35) but I have the dual in/single out 2.5" Magnaflow 18" muffler, removed the resonator, and love it. Little more power, little bit better mileage, and the perfect tone- not obnoxious at all, but a nice hum.

  • Like 1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

Welcome to NPORA Forums

 

Please REGISTER to gain full access to the forum.

Make sure you read the Forum Guidelines and don't forget to post a new intro in the New People Start Here! section, to say hi too everyone.

 

-NPORA

×
×
  • Create New...