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Old 01-10-2012, 07:53 AM   #1 (permalink)
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Remove Resonator for Intake Or Change Exhaust?

I'm yet to test but still thinking as restriction goes, the less the better.

DIY Intake

Do I remove the Resonator - Not necessarily Warm Air, just no resonator, on the intake, or do I focus on the exhaust options:
Resonator Drums down excess noise.
Muffler (straight through) Enhances sound!
Hi-flow cat converter Better flow than standard.
Extractors Improves power & efficiency!
Stainless Steel Muffler For a distinct sound & style.
2.25 inch system Improves overall performance!

The engine is lean burn, so I don't want to interfere with that if it relies on exhaust pressure (not too sure how exactly it works in terms of lean burn - or if it is, I thought it was from Wikipedia).

Of the exhaust options, I'm not sure headers would be helpful, however, freeing up the exhaust flow might help ?

Low end power is where I want to focus.

Perhaps:
- Remove Resonator On Intake to reduce one point of restriction.
- After Cat Converter, go to 2in exhaust with a resonator to reduce exhaust noise..

Would that make a not so noisy daily driver with some improvement in fuel economy? (assuming the exhaust changes don't matter to the lean burn ?)

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Old 01-10-2012, 08:22 AM   #2 (permalink)
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It sounds like you have your mind made up already, it also sounds like you have not read any air intake or exhaust design books.
On my car I've had to replace both the intake resonator and switch the exhaust back from over sized to stock and saw a MPG increase with both of those.
Also, what is your current exhaust back pressure and what do you hope to reduce it to? (do you even know if you have exhaust back pressure?) you can have exhaust back pressure tested by a mechanic pretty easily but larger exhaust tends to increase the back pressure at lower revs because of loss of momentum of the exhaust gasses.
So please, before you spend any money make sure that you understand what you are doing, pretty much any book on exhaust design will give you the formula to size your exhaust for the engine speed that you want to run at and you just might find that your current exhaust piping is even larger then you really need if gas mileage really is your goal.
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Old 01-10-2012, 08:36 AM   #3 (permalink)
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why would you run a 2.25 pipe?
is there a large (400 inch) V8 under the hood?

There are several calculators available for dtermining correct OD of exhaust pipe.
you need to use them.
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Old 01-10-2012, 08:54 AM   #4 (permalink)
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The Honda Civic VX, a lean burn vehicle of superb mileage used a smaller diameter intake duct as well as a smaller diameter exhaust.

If you know more than Honda did when they built the VX then go for it, but as the previous two posters have alluded to, you may be making the wrong assumptions.

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Old 01-10-2012, 03:21 PM   #5 (permalink)
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What's the point of asking questions to determine if one is following a possible solution, if the response is go source books on the subject?
And who is to say the books are free of errors...

My question was based on the possibility that less restriction on the air intake will help the engine breathe freely, and with air more easily available to pump in, should require less time in higher RPMs to get to the desired speed. This combined with driving techniques, I thought might reduce fuel consumption.

The exhaust has a similar line of thinking, if the exhaust can be more freely flowing, perhaps it requires less energy lost in pistons forcing air out of the cylinder, as the back pressure is reduced. But I was reading somewhere that Lean Burn engines rely on exhaust back pressure. I can't recall where.

So I figured who better to ask then here! Many exhaust websites claim improved fuel economy is possible with aftermarket exhausts. I've got no problem with stock or aftermarket, was merely contemplating possible mods and hoping for feedback...

The resonator's purpose is noise reduction. How does removing that, reduce fuel economy? It'll remove a restriction on air intake - isn't that a good thing for fuel economy?
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Old 01-10-2012, 03:36 PM   #6 (permalink)
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How is the resonator a restriction? Its simply a tube going to a chamber off the main pipe. At the rpms that ecodrivers drive at, this is not a restriction at all, neither is the filter or the intake plumbing.

Aftermarket intakes and exhausts are made for one reason, increased horsepower. Increasing horsepower means shifting torque to higher rpm ranges where it will produce more horsepower. This is what everything you have listed above does. Again, being an ecodriver means you don't use the engine in those upper rpm ranges and you now have less torque than you had before at lower rpm.

A tuned intake and exhaust may increase fuel economy, to figure this out you'd need to do a lot of testing. I have yet to see any soild testing on this (it would be a huge pain testing different diameters and lengths) but it can be done. If you wanted to mod your intake and exhaust you'd most likely go with a smaller intake and exhaust to shift the torque down to a lower rpm. This would result in less total horsepower and greater engine loads which also causes the engine to be used at lower BSFC rates which increases fuel economy.
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Old 01-10-2012, 03:50 PM   #7 (permalink)
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Quote:
Originally Posted by toc View Post
What's the point of asking questions to determine if one is following a possible solution, if the response is go source books on the subject?
And who is to say the books are free of errors...
You are right, there is nothing saying that those books are free of errors, but many of them do have formulas that have been tried, tested and proven over the years and as far as I know no one has proven those formulas to be wrong and I would link to an exhaust sizing calculator that I used to use but the last time I went to look at it the web site was gone, it did however use the same formula for figuring out exhaust size for a small engine running at low RPMs as it did for a large engine running at high RPMs because no matter the speed or engine size you want to size your exhaust to work with the engine, instead of fighting it.

Quote:

The exhaust has a similar line of thinking, if the exhaust can be more freely flowing, perhaps it requires less energy lost in pistons forcing air out of the cylinder, as the back pressure is reduced. But I was reading somewhere that Lean Burn engines rely on exhaust back pressure. I can't recall where.
Again, when you put a back pressure gauge on your exhaust (threads in to the O2 sensor bung) what is the pressure that you are seeing and how much do you hope to reduce it?

Quote:

So I figured who better to ask then here! Many exhaust websites claim improved fuel economy is possible with aftermarket exhausts. I've got no problem with stock or aftermarket, was merely contemplating possible mods and hoping for feedback...
If you are running your car at high revs and seeing poor mileage it is most likely because your exhaust is not tuned for those high revs so at that point going with a larger exhaust will help slightly with mileage, will it help you get better mileage then if you were not pretending to be a pro-racer? no, will it help you get above EPA mileage? most likely not.

Quote:

The resonator's purpose is noise reduction. How does removing that, reduce fuel economy? It'll remove a restriction on air intake - isn't that a good thing for fuel economy?
The intake resonator works kind of like a fly wheel, it helps store the pressure caused by pulses of incoming air between the pulses so that the flow of air coming in to the intake is steady and smooth, in other words it's quite, removing that resonator prevents the intake from storing the momentum and forces the engine to start from scratch pulling every fresh charge of air in to the combustion chamber.
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Old 01-10-2012, 04:14 PM   #8 (permalink)
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You've posted 70+ times so your not a noob.
Try using the search botton.
There are amazingly informative posts on theis vary topic that you should read first.

Most of your 'comments' reflect what is posted on retail product sites and not sites like EM.

Beleive me, a lot of us came here with similar misconceptions. But this is one of the best non biased non product orreiented sites on the net. There is rarely a thread that you can't learn something from.
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Third: Full underbelly pan
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Old 01-10-2012, 08:27 PM   #9 (permalink)
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If you are after all out horsepower, you want the engine to breathe better.

if you want better mileage, you are going to probably be running at VERY little throttle opening, and trying to get the most power out of the least air and fuel.

For these reasons, changing your intake won't help for mileage.
Further, opening the exhaust won't give you better mileage. Your engine was designed to make 70 horsepower max, so it doesn't need very much exhaust or intake.

Your VX is a pretty cool car. You are going to have a tough time making the basic engine more efficient. I would look at ignition timing, check compression, and learn to drive it.
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Old 01-10-2012, 09:24 PM   #10 (permalink)
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Sorry if 1) I can't read 2.) can't see 3) am stupid........

but........

Nothing anoys me more than a poster who
1.) assumes we know the car he is refering to
2.) doesnt state the car he is refering to.
3) presents multiple issues withuot refering to the specific car.

at this point, two responders say he has a honda, yet the diy link is a nissan and the op owns a sonata and a pulsar....

any clarification?

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First: ScangaugeII
http://ecomodder.com/forum/showthrea...eii-23306.html

Second: Grille Block
http://ecomodder.com/forum/showthrea...e-10912-2.html

Third: Full underbelly pan
http://ecomodder.com/forum/showthrea...q45-11402.html

Fourth: rear skirts and 30.4mpg on trip!
http://ecomodder.com/forum/showthrea...tml#post247938
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