Most Efficient Header and Exhaust Design - Page 2 - Fuelly Forums

Android Users - Coming Soon! - Migrating from aCar 4.8 to 5.0

Reply
 
Thread Tools Display Modes
 
Old 12-15-2005, 04:29 AM   #11
Moderator
 
GasSavers_DaX's Avatar
 
Join Date: Oct 2005
Posts: 1,209
Country: United States
Re: what do you guys think of

Quote:
Originally Posted by They
The result is increased horsepower and torque, improved fuel economy and less harmful emissionsówithout having to modify original engine specifications.
Sounds like you get everything - mileage, power, torque, less emssions... Generally when they offer a solution to all problems (i.e. - if it sounds too good to be true), it IS too good to be true, and I'm going with my gut instinct on this one.

Plus, who wants to ride around with that ricey fat *** chrome tip on their exhaust, haha.
__________________

GasSavers_DaX is offline   Reply With Quote
Old 12-15-2005, 09:12 AM   #12
Registered Member
 
Join Date: Oct 2005
Posts: 1,978
Country: United States
Re: what do you guys think of

Quote:
Originally Posted by DaX
Quote:
Originally Posted by They
The result is increased horsepower and torque, improved fuel economy and less harmful emissionsówithout having to modify original engine specifications.
Sounds like you get everything - mileage, power, torque, less emssions... Generally when they offer a solution to all problems (i.e. - if it sounds too good to be true), it IS too good to be true, and I'm going with my gut instinct on this one.

Plus, who wants to ride around with that ricey fat *** chrome tip on their exhaust, haha.
D-Money, that phat bling would pimp my ride hella badd. In all seriousness, I was thinking of this concept. Compaq888 may be able to confirm this, but I think the Altima muffler has a similar device to maintain backpressure at low RPM, then it opens up at higher RPM for the maximum free-flow (my '03 Evo had a simlarly valved muffler -- it sounded cool from behind, once the turbo spooled-up and you hit about 5000 RPM+ it sounded like a jet engine -- another side point :-) ) Basically backpressure for torque and free-flow for when you need it (so you're not stuck with a choked-off exhaust at 6500 RPM). I might give it a shot.

RH77
__________________

__________________
rh77 is offline   Reply With Quote
Old 12-15-2005, 11:01 AM   #13
Moderator
 
GasSavers_DaX's Avatar
 
Join Date: Oct 2005
Posts: 1,209
Country: United States
Re: what do you guys think of

Quote:
Originally Posted by rh77
D-Money
HAHAHA, I haven't laughed that hard in a while...
GasSavers_DaX is offline   Reply With Quote
Old 12-22-2005, 08:59 AM   #14
Registered Member
 
Join Date: Nov 2005
Posts: 34
Country: United States
When a buddy of mine

When a buddy of mine from work was into drag racing motorcycles, I was looking for a header to put on my Kawasaki GPZ, also. The 4/2 designs gave better mid range power, and lower red line power. While the 4/1 designs gave better red line power and less mid range power. The ratioal behind this was that the 4/1 designs could take advantage of tuning all of the cylinders in one acoustic chamber. So one big fat pipe was the answer, for peak red line performance. Headers seemed to be designed like air craft wings, with a super-critical RPM or speed in mind.
CruiseControl is offline   Reply With Quote
Old 12-22-2005, 10:07 AM   #15
Registered Member
 
MetroMPG's Avatar
 
Join Date: Dec 2005
Posts: 4,223
Country: United States
can someone explain the

can someone explain the relationship between backpressure and torque? it seems counter-intuitive that more backpressure = better low end torque.

my brain says, "how could backpressure help if the engine has to work harder to expel exhaust from the cylinders?"
MetroMPG is offline   Reply With Quote
Old 11-12-2008, 02:51 PM   #16
Registered Member
 
Join Date: Nov 2007
Posts: 1,111
Country: United States
Send a message via AIM to dkjones96
Digging up an old thread, but everyone is doing it.

But this question was never answered. Backpressure doesn't increase torque. Backpressure is ALWAYS counter-intuitive of fuel economy and power.

It used to be thought that bigger pipes reduced backpressure and you lost torque and economy. That is only half true. The bigger pipes did reduce torque and economy but not because of backpressure, it was the result of less exhaust gas velocity resulting in less scavenging and more waste.
__________________
- Kyle
dkjones96 is offline   Reply With Quote
Old 11-12-2008, 04:15 PM   #17
Registered Member
 
Join Date: Jul 2007
Posts: 31
Country: United States
I am no expert, but my understanding is this: Backpressure is always bad, as it increases pumping losses. The problem with large pipes, however, is an exhaust velocity that is too slow, especially at low RPM, when there is not much gas to be pushed out. The factory-equipped exhaust is small because most street driving involves RPM < 3000. At these speeds, a larger pipe would have very slow exhaust gases, and because of the low volume of exhaust, backpressure is not an issue. Upgrading to a larger pipe would increase power at higher rpms at the expense of some torque at the low end. If you like to drive to the redline, it will help, otherwise it would hurt. You want the smallest pipe that would have minimal backpressure at the target RPM. As a hypermiler, you would probably want to stick with the smaller exhaust.
__________________


skale7 is offline   Reply With Quote
Old 11-12-2008, 05:08 PM   #18
Registered Member
 
Join Date: Dec 2007
Posts: 170
Country: United States
rh77,
I would start with working out your RPM for your highway driving then tune the exhaust to match the highest level of efficiency you can find for that RPM.

The debate about power/ economy is about the choice of either/ or but not both at the same time.

Pete.
GasSavers_Pete is offline   Reply With Quote
Old 03-30-2009, 09:28 AM   #19
Registered Member
 
Join Date: Sep 2008
Posts: 9
Country: United States
ok i have a d13b engine 1.3l what if i change the header to a d15b stock one ?
kakaroto_ss4 is offline   Reply With Quote
Old 05-22-2009, 11:32 AM   #20
Registered Member
 
Join Date: Sep 2008
Posts: 170
Country: United States
The d15b header should work well on your 1.3.

Honda does have somewhat restrictive exhaust manifolds, but they've moved on recently to longer runners. Smaller, longer primaries and a well designed collector help exhaust air move with better velocity, improving engine breathing and power production. The size of the primaries (smaller= lower) is probably the most important factor in determining what rpms power is available. More torque at lower engine rpms will allow you to drive in a lower range thus improving mileage. It's all about driving in the most efficient rpm range that maximizes economy!
__________________

__________________
I exit lean burn when my life is at risk.
1998 Odyssey 24.1 mpg average
1984 crx project now on the road
hondaguy72 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
What is New 2012 Camry Agerage MPG nehalrana General Fuel Topics 3 10-20-2011 03:36 AM
Slightly annoying sort order on 'View all fuel-ups' lowlevel Fuelly Web Support and Community News 2 11-25-2010 09:04 AM
Make / Model/ Year averages jeadly Fuelly Web Support and Community News 1 08-15-2008 12:02 AM

Powered by vBadvanced CMPS v3.2.3


All times are GMT -8. The time now is 10:08 AM.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.