Modifying exhaust to increase mileage? - Fuelly Forums

Click here to see important news regarding the aCar App

Reply
 
Thread Tools Display Modes
 
Old 09-14-2005, 07:50 AM   #1
Driving on E
 
Matt Timion's Avatar
 
Join Date: Sep 2005
Posts: 3,110
Country: United States
Modifying exhaust to increase mileage?

Will modifying the exhaust pipe yield better gas mileage? Some people have said that putting on a larger pipe will in fact help with fuel economy, as the exhaust is less restircted.

There is a Civic EX at my local junkyard with a dual point exhaust. it should bolt right up to my car. Do you think that switching from single point to dual point will help increase my gas mileage at all?
__________________

Matt Timion is offline   Reply With Quote
Old 09-14-2005, 10:28 AM   #2
Registered Member
 
Join Date: Sep 2005
Posts: 144
Country: United States
Help! 87 Honda Civic A/C Wiring

There was a thread about this not too long ago over at honda-acura.net that talks about exhaust diameter and performance (or efficiency in our case). Conceptually it's easy to see why a larger diameter pipe would allow more exhaust flow. However, there is a practical limit in this. The details are in the article I referred to, but the basic idea is that it's about balancing cross sectional area with velocity. An exhaust pulse traveling down a pipe will go faster than an identical pulse going down a larger diameter pipe.

I just searched for the thread because I think it might be a worthwhile read everyone here.

<a href="http://www.honda-acura.net/forums/showthread.php?t=201281">Backpressure: The myth and why it's wrong</a>
__________________

__________________
Scouring the country for an excellent condition Civic VX
Flatland2D is offline   Reply With Quote
Old 09-14-2005, 01:56 PM   #3
*shrug*
 
Join Date: Sep 2005
Posts: 6,195
Country: United States
Vertical Range of Electric Vehicles?

Quote:
Originally Posted by Matt Timion
Will modifying the exhaust pipe yield better gas mileage? Some people have said that putting on a larger pipe will in fact help with fuel economy, as the exhaust is less restircted.

There is a Civic EX at my local junkyard with a dual point exhaust. it should bolt right up to my car. Do you think that switching from single point to dual point will help increase my gas mileage at all?
Lower back pressure is better for mpgs is there theory, but then why did honda make our pipes like 1.25"? I dunno, mehbe cheapness since it's not a preformance car and mehbe something else. Either way, the real question is how it the cross sectional area of the entire system going to flow? If you have a 2" pipe going into a muffler with a 2" tip, then it is the same as a 2" pipe going into a muffler with two 2" tips. The resistivity of a system is governed by the section with the smallest cross sectional area, if you add some big piping on the end but leave smaller stuff somewhere else it'll come that same speed as always out the 2" and then just sit around cuz the flow from the 2" pipe is not enough to use the possibility of the 4" pipe. I hope that makes sense in the case of getting a dual exhaust thingy.

PS: any luck on the knuckles?
SVOboy is offline   Reply With Quote
Old 09-14-2005, 08:33 PM   #4
Registered Member
 
Join Date: Sep 2005
Posts: 33
Country: United States
Sometimes being a fuel economy dork is the coolest thing

I have always been told that back pressure is good at low RPM's. It seems to help torque.
Nissan has a muffler on the 2.5 L cars with a spring loaded valve. At low RPM the valve is closed. As pressure increases (at higher RPM) the valve opens increasing flow. Best of both worlds.
chasgood is offline   Reply With Quote
Old 01-02-2006, 06:55 AM   #5
Registered Member
 
Join Date: Dec 2005
Posts: 24
Country: United States
Jet turbine exhaust

Here is a link for a jet engine car exhaust:
http://www.aero-turbine.com/how/

Anybody know how to add an afterburner?
GasSavers_JustMe is offline   Reply With Quote
Old 01-02-2006, 07:28 AM   #6
Registered Member
 
Compaq888's Avatar
 
Join Date: Oct 2005
Posts: 1,460
Country: United States
Re: I have always been told that

Quote:
Originally Posted by chasgood
I have always been told that back pressure is good at low RPM's. It seems to help torque.
Nissan has a muffler on the 2.5 L cars with a spring loaded valve. At low RPM the valve is closed. As pressure increases (at higher RPM) the valve opens increasing flow. Best of both worlds.
Are you talking about the 2.5 altima? I don't know if it has it. But when you open it up it sounds like a police siren.
__________________

Compaq888 is offline   Reply With Quote
Old 01-02-2006, 07:39 AM   #7
FE nut
 
diamondlarry's Avatar
 
Join Date: Sep 2005
Posts: 1,020
Country: United States
I'm not sure how effective

I'm not sure how effective it is but I hear that you can weld a sparkplug into the exhaust tip and plumb in some propane with the appropriate controls and flip a switch while tou're gunning the engine to shoot flames out the tailpipe.
__________________
Horsepower is how hard you hit the wall, torque is how much of the wall you take with you.

2007 Prius,



Team Slow Burn
diamondlarry is offline   Reply With Quote
Old 01-02-2006, 09:24 AM   #8
Registered Member
 
Join Date: Oct 2005
Posts: 1,978
Country: United States
Re: Modifying exhaust to increase mileage?

Quote:
Originally Posted by Matt Timion
Will modifying the exhaust pipe yield better gas mileage? Some people have said that putting on a larger pipe will in fact help with fuel economy, as the exhaust is less restircted.

There is a Civic EX at my local junkyard with a dual point exhaust. it should bolt right up to my car. Do you think that switching from single point to dual point will help increase my gas mileage at all?
I'm still at a loss with trying to find out info about exhaust diameter. I have exhaust leaks and need to replace all but the header and cat as soon as I can make a decision. I'd hate to stay stock and find out that a different muffler or diameter could have yielded better economy, but it's tough searching the Net. For a larger diameter, free-flow muffler, the marketing is "More Power, Better Fuel Economy!" -- but that's a but of a contradiction.

I'm trying to look at the design of fuel-efficient Hondas for direction. It seems like the more restrictive, the better.

Since the EX had a more powerful engine, I'm guessing that it has a larger exhaust system. My gut feeling is that it would yield less torque and a loss in economy.

This is all just thinking out-loud, but if you lose torque, you press on the throttle more to get going from a stop, which means more fuel used. Once out on the highway, free-flow may mean better economy since the RPMs are up and it would take less energy to push the exhaust out -- but for some reason, you need backpressure at lower RPMs.

If I had to decide right now, I'd go with smaller diameter piping and a stock muffler, or one with a valve like the 2.5 Altima or Lancer Evo. A device called the "Turbolator" is on the market that does the same thing (separate thread). I'd really like to understand the science of backpressure better...

RH77
__________________
rh77 is offline   Reply With Quote
Old 01-02-2006, 10:33 AM   #9
Driving on E
 
Matt Timion's Avatar
 
Join Date: Sep 2005
Posts: 3,110
Country: United States
You may want to just visit a

You may want to just visit a local muffler shop and ask them what the correct pipe size is for various cars. I'm certain they have this information on hand.
Matt Timion is offline   Reply With Quote
Old 01-02-2006, 11:50 AM   #10
Registered Member
 
kickflipjr's Avatar
 
Join Date: Sep 2005
Posts: 933
Country: United States
I think that the stock pipe

I think that the stock pipe diameter on most cars is the best. If it's possible you can install maderall bent pipe for a tiny increse in mpg.

The turbolator (sping valve exaust tip) looks interesting. I think it would help at idle.
__________________

__________________
2008 EPA adjusted:


Distance traveled by bicycle in 2007= 1,830ish miles
Average commute speed=25mph (yes, that's in a car)
kickflipjr is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
feature requests ThatGuyDuncan Fuelly Web Support and Community News 4 09-18-2008 12:18 PM
suggestion for stat comparison zahampton Fuelly Web Support and Community News 1 09-04-2008 07:29 AM
All Licensed Drivers terrapin Fuelly Web Support and Community News 0 08-07-2008 09:49 AM
Calendar picker for entering fuel-up date? delfuego Fuelly Web Support and Community News 1 07-19-2008 01:18 PM
"active" aero grille slats on 06 civic concept MetroMPG General Fuel Topics 21 01-03-2006 12:02 PM

» Fuelly iOS Apps
No Threads to Display.
Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 06:51 PM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2024, vBulletin Solutions, Inc.