Aftermarket exhaust and intake fact or fiction...

[waterpoloman13]

I am looking at aftermarket exhausts and intakes, and would like to check on some hear-say before I pull the trigger based on real-world experience:

Do aftermarket exhausts and/or intakes increase fuel economy?

I know that there is an increase in power, that seems to be pretty common in most posts I've seen, but I have read mixed tales about economy.

Can anyone clarify this based on experience?

Thanks,

Chris

[SASKCB7]

From what I understand it will help the engine to breath easier, run eaier. making it consume less fuel to put out power. More air going in, less backpressure in theexhaust.
I'm no expert but I think that's what ive heard.

If not correct I hope someone will clarify how things go.

[Yakima]

I am looking at aftermarket exhausts and intakes, and would like to check on some hear-say before I pull the trigger based on real-world experience:

Do aftermarket exhausts and/or intakes increase fuel economy?

I know that there is an increase in power, that seems to be pretty common in most posts I've seen, but I have read mixed tales about economy.

Can anyone clarify this based on experience?

Thanks,

Chris

Fuel consumption: This is true to a degree. Think of the engine like a giant air pump. If it can't pump out air to the best of its ability (restrictive stock exhaust) then it will use extra fuel to get that air out. So, making the exhaust bigger helps with fuel consumption, and with power, because the power comes more freely. However, If you increase the size of the exhaust too much, you'll lose power and increase fuel consumption.
Bear with me, because I don't fully understand "too big", but it seems to be general knowledge.
When the exhaust exits the engine, it has a certain speed (velocity?). In order to maintain that speed, you need optimal exhaust size.
Too small and you get what I described above. Just right and you have optimal speed. Too big and you create areas for the exhaust gas to pool and slow down. That will rob you of power like you wouldn't believe.

Extra stuff: I think 2.25 inch is about optimal.
Ignore what anyone says about back pressure.

[Joey GT-R]

If 2.25 was optimal than we wouldn't need performance exhausts since that's the size of the stock exhaust. 2.5-3.0 would be beneficial to a well modified motor.

[JoshM]

If 2.25 was optimal than we wouldn't need performance exhausts since that's the size of the stock exhaust.

OEM is about 1.75".

[Joey GT-R]

Seriously? Mine came with a 2.25 and a chrome exhaust tip....with no other mods. Guess the original stock rusted and was replaced. Learn something new everyday....

[wed3k]

it will get better economy as long as you dont flog on it to hear the intake sound.

[dano28]

Yes.. you will get a bit of added fuel economy but who cares !!

[deevergote]

@ stock exhaust size being 2.25"


Anyway, an aftermarket intake and exhaust on a stock ECU will probably DECREASE fuel economy, honestly. The ECU will read a greater oxygen content via the o2 sensor, and it will increase the amount of fuel that is delivered. Also, increasing the intake and exhaust diameter will shift the powerband up a bit. so you will need to rev slightly higher to get the car moving. Nothing really noticeable, but 100-200rpm increase over an entire tank of gas will have an effect. Finally, your car will sound more aggressive, so you will probably be driving with a heavier foot... and that will certainly decrease gas mileage.

Allowing the engine to breathe easier CAN increase fuel economy, as long as you reprogram the ECU to know what to do with it. When I had my ECU tuned for my H22, I gained 3-5mpg (25 to 28-30 on average.)

[Andryzzle]

Finally, your car will sound more aggressive, so you will probably be driving with a heavier foot... and that will certainly decrease gas mileage.

That really is a huge part of gas mileage.

[gloryaccordy]

@ stock exhaust size being 2.25"


Anyway, an aftermarket intake and exhaust on a stock ECU will probably DECREASE fuel economy, honestly. The ECU will read a greater oxygen content via the o2 sensor, and it will increase the amount of fuel that is delivered. Also, increasing the intake and exhaust diameter will shift the powerband up a bit. so you will need to rev slightly higher to get the car moving. Nothing really noticeable, but 100-200rpm increase over an entire tank of gas will have an effect. Finally, your car will sound more aggressive, so you will probably be driving with a heavier foot... and that will certainly decrease gas mileage.

Allowing the engine to breathe easier CAN increase fuel economy, as long as you reprogram the ECU to know what to do with it. When I had my ECU tuned for my H22, I gained 3-5mpg (25 to 28-30 on average.)

It could go either way.

ECU won't necessarily dump fuel, just maybe add a little more.

But on the upside, w/less restrictions the engine will burn less fuel to make the same power under part load. Which I don't htink even the ECU could overcome efficiency wise.

So I think bolt ons are worth it. All my Accords were uncorked and I got like 20MPG all city in my H22 ones and ~25MPG in my first one (also mainly all stop n go city driving).