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

[SVOboy]

Unfortunately, this question is not age old, and you will get a different answer from everyone, and you'll end up figuring I'll just have to go for a shot in the dark and see what the hell happens. I'd try more restrictive, but that's just my shot in the dark. The economy models from honda all came with super restrictive exhausts and intakes.

[Matt Timion]

Originally Posted by SVOboy

The economy models from honda all came with super restrictive exhausts and intakes.

he's right. The honda economy models have restrictive intakes and exhausts. It kind of flys inthe face of what everyone has been saying to me for the last year.

Originally Posted by everyone

More power equals better fuel economy.

See, they just did it again.

Seriously though, I'd start researching the smallest possible diameter you can put on.

I wish we could get a Honda engineer here to talk about why certain choices were made and how fuel economy was considered in the process.

[rh77]

Yeah, I figured that "more restrictive" might yield better economy, but too much backpressure could be counter-productive. Since the '06 Civic get's awesome mileage, I'd figure I'd start there with some research. It turns out that it doesn't even have an exhaust header. It has an exhaust manifold integrated into the cylinder head, and a Cat right off of the outlet for quick burn-off, etc. It's a tidy design, but doesn't help my cause.

Further research shows a direct correlation between more backpressure and decreased fuel economy. So...perhaps leave the header and diamater the same, but add a free-flow muffler.

RH77

[rh77]

Originally Posted by Matt Timion

he's right. The honda economy models have restrictive intakes and exhausts. It kind of flys inthe face of what everyone has been saying to me for the last year.

See, they just did it again.

Seriously though, I'd start researching the smallest possible diameter you can put on.

I wish we could get a Honda engineer here to talk about why certain choices were made and how fuel economy was considered in the process.

Everything I read keeps saying more flow = more power/economy. But more power doesn't seem to relate to economy -- seems like the opposite. I remember when I replaced the muffler on my old civic DX with a free-flow model, the torque went through the floor. After damaging it in a "Winter incident", I put the stock muffler back on, and it felt like it had a turbo installed. Hondas must thrive on that backpressure. We could certainly use the help of Honda engineer.

RH77

[kickflipjr]

Yeah, I think: Bigger Exaust Pipes=more air flow=more fuel to keep an even ratio.

The best setup would be free flowing but small (stock size maybee smaller). Manderal Bends and a free flowing muffler would help.

I assume, Bigger pipes also have less air velocity at lower rpm (were most economy driving is done).

[SVOboy]

My stock size is 1.5 inches I think, so think about that. What else...No point in having a high flow muffler with a stock exhaust, defeats the purpose. I think you want to be able to strike a balance between exhaust velocity and backpressure. Not enough velocity and it kind of stews around there.

[rh77]

I think the diameter is 1.8" -- I'm not sure of the different sizes of tubing, but I can see trying to go down to 1.5" as a solution and find a close-to-stock muffler replacement. Does anyone know what diameter the late-90's Civic HX Coupe exhaust system is? That may be a good starting point...

RH77

[SVOboy]

I dunno for sure, but I'll be damned if it ain't smaller than either of your cars'.

[kickflipjr]

what do you guys think of the turbolator



They claim it save gas up to 8.3% (which dosen't mean anything).

"Patented self-adjusting internal control valve responds to RPM load and temperature to equalize pressure and regulate exhaust flow. During high exhaust flow, the internal valve opens to let engine gasses escape freely. At lower RPM, the internal valve closes to regulate exhaust flow and improve engine performance. The result is increased horsepower and torque, improved fuel economy and less harmful emissions—without having to modify original engine specifications. Must be welded to exhaust pipe. "




I would like to try one out if it wasn't $64