Most Efficient Header and Exhaust Design

[rh77]

OK, so there's an age-old debate on which header and exhaust makes the most horsepower, but what about fuel economy? I have an exhaust leak and all but the Cat must go. 80/20 Highway/City driving. What is the opinion:

* For the Integra, should I go for the 4-into-1 header, or the 4-into-2-into-1 header?

*Backpressure: leave the stock exhaust diameter
or go larger (or smaller, for that matter).

*The RS-R Ex-Mod may be the muffler of choice (instead of a stock replacement) for sound preference and free-flow.

The CO is getting to me at stops, so everything must go (but the Cat seems to be doing the job for now).

I'm willing to take a sacrifice in power for better economy.

RH77

[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.

[skale7]

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.

[GasSavers_Pete]

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.

[kakaroto_ss4]

ok i have a d13b engine 1.3l what if i change the header to a d15b stock one ?

[hondaguy72]

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!

[Ranana_Zess]

heres the deal:

Im sure like most, you too are sick of the constant and chronic "what exhaust" or "what sounds best" or "insert exhaust question here"

So, heres what I am thinking:
explain exhaust theory and practicality velocity, backpressure, flow, etc,
discuss headers short, long, TriY, etc,
organize all sound clips into one post,
have people with personal experience post up with their opinions on how the system worked



Also, please post any and all pictures you have of setups for ideas of pipe routing, clearances, etc.



Opinions/Input/Changes? Post them up.

[CA ExhaustCoatings]

http://ssheaders.com/
http://www.headerdesign.com/extras/design.asp
http://www.burnsstainless.com/TechAr...ry/theory.html
http://www.headersbyed.com/
http://www.kengineering.info/headers.html