Looking for a fuel efficient solution. I've got a few ideas.

[tasdrouille]

Originally Posted by CuriousOne

[...]As far as I know there's no way to make more power while having better fuel efficiency when you modify your intake[...]

Reducing the restriction of the intake will benefit both power and fuel economy.

[DifferentPointofView]

Backpressure in an exhaust system is never needed,

WOAH WOAH WOAH!!! wait a minute. in order for best efficiency or best power, a balance of back pressure vs. exhaust flow is needed.

Exhaust comes in pulses.

(team integra) To understand how to properly tune an exhaust you must first understand exactly how the gasses will be flowing through it. Exhaust gasses do not flow in one continuous stream they get shot out in pulses. Each time a valve opens and gas is pushed out of the combustion chamber, it creates a pulse. As you can see from the picture, the head of the exhaust pulse remains at a high pressure after it is shoved out of the combustion chamber. The center of the pulse is closer to the ambient pressure of the exhaust system and the tail turns into a low pressure vacuum.

Now look at these exhaust pulses all lined up as they travel through the exhaust. This would be an exhaust system which was sized perfectly for the car at the right RPM. The pulses, to an extent, will move through the B-pipe to the muffler by themselves. But we want the exhaust gasses to travel as fast as they possibly can. How can we get them moving faster? Well you get them to line up like shown, and the pulses will then pull each other through. As with most naturally occurring phenomenon, opposites will attract. The high pressure heads are pulled into the low pressure, almost vacuum-like tails. So each pulse will follow after the other, effectively leading each other to the muffler and away from the engine.

too much back pressure equals a restrictive exhaust system.


Here is a correctly sized exhaust system. just the right amount of back pressure.



INCORRECT EXHAUST PIPING!!!! Too large and even though it is "unrestricted" It restricts itself from the lack of back pressure. If you want unrestricted, might as well go with no pipes at all.




I'm not baggin' on ya, I just don't wanna give out the wrong idea. Your right that most pipes are usually crush bent, which is way too restrictive. but back pressure is essential to an exhaust. otherwise you'd just go with no pipes at all.

Heres' the full article
Team Integra-Exhaust Basics

[RH77]

Team Integra -- Oh Yeah! (Enter Kool-Aid Man)....

RH77

[CuriousOne]

What is needed is taking advantage of the exhaust scavenging effect and have the highest exhaust velocity. Backpressure is not needed, but if you think it is, then that's cool. But I don't really think it is from everything I've learned and read about.

Anyways, has anyone experimented with timing on the cars listed above? Should I advance or retard it from it's base?

[RH77]

Originally Posted by CuriousOne

What is needed is taking advantage of the exhaust scavenging effect and have the highest exhaust velocity. Backpressure is not needed, but if you think it is, then that's cool. But I don't really think it is from everything I've learned and read about.

Anyways, has anyone experimented with timing on the cars listed above? Should I advance or retard it from it's base?

I've heard to warm up the car (WAI at full temp, if equipped), advance the timing until you hear a knock, and back it off a degree or 2.

Someone step-in if I'm mistaken...

RH77

[Duffman]

Originally Posted by CuriousOne

What is needed is taking advantage of the exhaust scavenging effect and have the highest exhaust velocity. Backpressure is not needed,

Absolutely correct. The balance is that smaller pipes that promote velocity create packpressure, but mufflers and kinks in the pipes etc are pure losses.

[RH77]

Originally Posted by Duffman

Absolutely correct. The balance is that smaller pipes that promote velocity create packpressure, but mufflers and kinks in the pipes etc are pure losses.

Consider the stock exhaust on the Civic VX -- very restrictive, yet very efficient -- hmmm...

RH77

[AXMonster]

Originally Posted by RH77

I've heard to warm up the car (WAI at full temp, if equipped), advance the timing until you hear a knock, and back it off a degree or 2.

Someone step-in if I'm mistaken...

RH77

Absolutely correct. All vehicles (without knock sensors) are mapped to DBL (Detonation Borderline) -2, which is as you say the knock point -2 degrees.
However, they are mapped on the worst reference fuel at the worst conditions. We probably won't be driving at those conditions (although the WAI is bad for knock) so you can probably advance the timing by a few degrees until incipient knock is heard (about one knock every second or two) then back it off by a degree. This is your engine's DBL-1, which may be quite a bit advanced over the stock setting. High octane fuel will help get this higher, although there is usually a cost involved over regular gasoline.

To hear knock you should be familiar with the sound you are listening for (sounds like two hammers being hit together), or fit a knock meter or det cans (either electronic or a length of bundy tube).

Home made det cans with metal bundy tube can be made with a length of tube long enough to go from the engine block to the driver's seat, passing through a hole in the firewall. The block end needs to be flattened and drilled to bolt onto the block about 1/3 of the way down the block in the centre. Then route the tube through the engine bay and bulkhead (without touching anything) to about head height by the driver's seat. A piece of rubber hose can be fitted on the end of the tube and split into two at any point, then fed into a pair of ear defenders with holes drilled to feed the hoses in.
The aim is to be able to hear the engine combustion noise without hearing all the surrounding noises.

[trebuchet03]

Originally Posted by CuriousOne

Backpressure is not needed, but if you think it is, then that's cool. But I don't really think it is from everything I've learned and read about.

It's not really just "do we think" - a great deal of money and resources have been invested in researching, modeling etc. this... What do you think manufacturers are tuning when they claim "tuned exhaust"? It'd be quite effective for them to just go with super big diameters rather than spend a LOT of money to do fluid flow analysis.... As a hint - they don't tune for sound

The tricky part.... In vehicle design, the engine exhaust manifold is typically the same regardless of application (vehicle to vehicle)... So the engineers have several options. They can tune for the designed pressure in the manifold itself, tune for some knowing more will come from other components, etc. Things are always a compromise, but these engineers are purty smart....


And to top everything off.... If you're outflowing your stock exhaust... You're not eco-driving You should never outflow your intake or exhaust... If you do, it's not the mechanics holding you back - it's your driving style/technique

[8307c4]

Gut the interior - Yes.
> Keep in mind you'll need to keep all the parts, and re-installing these when it comes time to sell it is a fair requirement, but it does help. One of the easier and most beneficial things to do is removing the back seat.

Remove Power Steering - You'd have to replace this with a manual steer box, otherwise the lack of fluid flow in the system can, over time, ruin your whole steering mechanism.

Remove Air Conditioning - Yes.
> However this could prove disastrous, how do you plan on relieving the freon?
Also when reselling the car, you'll either have to re-install it all or lower the price (and it could make it hard to sell).
The easy solution is to just not run it, maybe remove the belt if it's independently driven.

Increase Tire Pressure - Don't go past max.psi sidewall, you'll only wear the tires down the center, but max.psi sidewall is the best psi.

Originally Posted by CuriousOne

A warm air intake has less oxygen molecules which means the car will make less power, which means more fuel efficiency. Cold air intakes contain more oxygen molecules since they are denser. As far as I know there's no way to make more power while having better fuel efficiency when you modify your intake, but with an exhaust it is.

Keeping a light foot on the throttle?
If you can increase FE with an exhaust mod that increases power then the same holds true for the intake. A warm air intake is the equivalent of putting a wooden block under your throttle pedal, govern the engine forcibly or govern the foot voluntarily.
Because I am 90% sure exhaust upgrades will do as little if we can't keep the foot light.

On that note, and inexpensive mods:
First, keep up on the maintenance religiously.
Air filter, pcv valve, breather cap, fuel filter, O2 sensor, oil and filter, just to name a few.

Double platinum spark plugs (run better, longer).
10+mm high performance spark plug wires (about $80).
High performance cap and rotor.
> Increase spark, hence power and FE.

Synthetic oil tends to help as well, but not sure if the cost difference is worth while.