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I am debating on getting a CAI or short ram but I am wondering of it's actually worth the money to hear the loud sound and will it increase my mpg really???? I am wondering if I will achieve better results than the factory OEM design?

 
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You will definately hear a small roar from the SRI. (What Ive got)

btw I went short ram bcuz my i didnt wanna risk hydrolock

lol I went the cheap way and bought an ebay short ram intake pipe then used a K&N filter.
I had fitment issues tho, and had to really force the SRI pipe to sit on the throttle body and when I close my hood it rattles the hood. I love the deep sound when the throttle is applied heavily!

 
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It depends on the engine (D-series doesn't see much of a gain from i/h/e bolt-ons) and whether or not you're going to add any other mods. My gas mileage stayed the same with my SRI, but my foot is definitely heavier than it used to be as well. I love the sound my intake makes when I stomp on the gas!

 
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Hydrolock is only a problem if you completely submerge your filter in water. If that happens then you really shouldn't be driving it in that deep of water. I have a CAI and have driven my car is some pretty bad rainstorms, never had an issue. I do have to be mindful of what roads to take if it has been raining for a whole and if it looks to deep, I don't risk it wouldn't be as big an issue with the SRI but I like the sound and midrange torque the CAI adds.

That's the problem with cheaper eBay intakes is the fitment quality.

 
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That's probably why I shouldn't get a CAI or SRI. I'll burn more gas due to punching the gas to achieve that deep tone. I'm keeping it OEM.

 
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Do some research on intake turbulence. You will learn why the OEM intake is far superior to any aftermarket.

 
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before I put in a SRI the car would run about 3900RPMs at 75mph, now it runs at 3500RPMS at 75. I'd say it's worth it. It makes more noise than stock but that's what the radio is for.

 
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What in the world does an intake have to do with gearing?

 
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i was thinking the exact same thing

 
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i'm assuming the engine is more efficient with a air intake so therefore it doesn't have to turn as fast. lower RPMs would mean less fuel consumption right?

 
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No it doesn't work like that at all. The RPM vs. speed is determined by the gearing inside the transmission. Your RPMS should be identical before and after an intake.

 
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I don't see how it wouldn't affect your RPM.

With the air intake you get more air in the cylinder -> more combustion -> more power per stroke. So with a fixed speed of 75mph, the engine is producing X amount of power at 3500RPMs to push the car to 75mph. With the stock air box, the car has less powerful combustion and has to turn at 3900RPMs to produce the same power.

If that's not the case then what could explain why I have lower RPMs now since I haven't done anything with the transmission?

 
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More air in the cylinder pushing more power to the engine just means less throttle necessary at the same RPM to maintain equivalent speed. As far as different RPMS I'm not sure put your stock airbox back on and drive it around see if what your seeing is accurate because it makes no sense.

 
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^^^ incorrect

^^^ correct

 
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i don't understand how you can have less throttle AND the same RPM. With less throttle the engine should turn slower.

I found this EQ for HP:

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Also did some a search and found at 4800 RPMs, an 02 Civic EX produces about 114 lb-ft of torque. So just plugging in the numbers, you would get 104HP at 4800 RPMs. Lets say 104HP pushes the car to 90MPH.

An air intake is going to increase your torque so lets say we get an extra 10 lb-ft. So we rerun the formula with 124 lb-ft and get 113HP at 4800RPMs.

So at the same RPM the engine is producing more HP which would drive the car faster right? By this calculation I can produce 104HP with 124 lb-ft of torque at 4,400RPMs. So therefore I'm pushing the car to 90MPH at a lower RPM.

I don't understand, what I'm not understanding. hahaha

 
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TBH? when driving an auto, if I lift the throttle, the trans shifts gear up.

all depends on how the ECU controlling the trans was programmed. Of course, my long gone civic did refuse to shift up from 3rd in a mountain road when a car cut me off and slowed down.

drhawkinz, you car *could* have shifted or not. Other than that, the gearing is what it is, no changes in RPM due to power.
did your car shift?

did you say that in acceleration instead of steady state?


If not, your trans/clutch could simply be slipping...

 
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an intake can not have any effect on gearing,

if your rpms are 3,000 in top gear at 70mph (just an example) then that is the way its going to be ALL THE TIME, unless you change one or both of the following......

the first would be to physically change the overall gearing of the transmission, with a different tranny, and/or different internal gears/ratios,

the second would be to change the overall diameter of your wheels

 
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Not necessarily. Engine speed and throttle are not exactly linked. Lets start with Wide Open Trottle. If you find a way to get more fuel and air into the engine at WOT you will get horsepower. Cooler air is denser so even though the trottle is the same the engine will intake more air and fuel and produce more power. As the air and under hood temperature increases the air is less dense and power decreases.

When you drive you don't know exactly how far open the throttle plate is. Most people give the car enough throttle to get the acceleration they desire, they don't know if they pushed the gas pedal down 30mm or 31mm.

When you look at engine RPM and vehicle speed the main factors are the gears. Either a clutch or lock-up torque converter locks the crankshaft to the transmission preventing slippage. At a certain engine RPM the wheels will be turning a certain number of corresponding RPM's.

 
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drhawkins could be right, as I saw similar things happen on my (POS) Escort SE...

I'm assuming we're talking about an automatic, as it wouldn't apply on a manual, no way. The explanations drhawkins is using though, kinda miss the point a bit...

The torque converter depends on pushing fluid through a turbine to transfer power; meaning the TC is a load. If the motor is creating more power with each combustion stroke, that means more power is available to push past the fluid resistance in the TC, meaning more power makes it to the ground. Following that logic, that means less power strokes are required to maintain a certain speed. Less power strokes = lower rpm.

As long as the TC isn't locked up at the time... the fewer revs will be required to maintain a speed in a gear with a fluid coupling like a TC... that is, until the trans decides to shift. Usually what happens is the add'l power will cause shifts to occur slightly sooner... and when your trans has only four gears and fluid pressure shift logic... it means your trans will hold a high gear on going uphill much more than if the motor was weak. This is exactly what my Escort was doing after I serviced it after buying it from my maint-allergic mother.

If we're talking about a manual though... drhawkins, the crank is then linked physically to the wheels in gear. Faster crank speed = faster wheel speed, and vice versa. No way can more power (much less a CAI/SR) can affect rpm@speed.

 
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I'll use wind as an example because it displays resistance. If your driving down a perfectly flat highway with no wind at all. Your foot will only have to be on the pedal a little bit to maintain 2000rpms and a speed of say... 80km/h. Now. Put a 200km/h (I know.. I know) headwind and you will need to have the pedal down almost all the way to maintain an RPM of 2000 and a speed of 80km/h. Just because your at 2000RPMs doesn't mean your using all the power at said RPMs. Same goes with an intake. You might have MORE power at 2000RPMs which means that your foot will be slightly lower on the throttle to continue going down the same highway. Our 5 speeds don't have CVTs so the gear is physical and the only way your RPMS can change going 100km/h is by changing the physical gear.

CVTs may be different. I shouldn't have assumed he drove a 5 speed and I don't know if it would make a difference with a CVT or auto.

 
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drhawkinz, bottom line is: depends on which gear your trans ECU was shifting the car at the time.

if it was in the same gear as before, then no. should not make a big difference, unless your trans/clutch is slipping.

 
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yeah I was thinking about the example of driving up a hill. On the flat part before the hill you could be at 50% throttle and going 45MPH but then once you start the climb you have to go WOT to maintain the same speed. I would expect your RPMs to increase as you now have gravity pulling you back down the hill. Same thing if you had a truck that was pulling a boat. I would think it would take more force to pull the extra 700lbs behind you so the engine would have to turn at a higher RPM to produce more power to maintain the same speed.

If it's a 5 speed and fixed gear with where RPMs relate directly to speed then where does the extra HP from the air intake go? I would assume that would have to show it self somewhere since everything is physically binding together.

It's a manual 5 speed. And it's always in 5th, I never really paid attention in 4th since I was usually passing somebody then. I remember when I first got it wondering if it was normal to scream at 4K RPM driving down the road. Then I searched in here and discovered that was the norm. Then after the RAI I noticed it was running at a lower RPM. But maybe it's time for a transmission fluid flush and hopefully the clutch isn't on the way out.

 
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Going up a hill is a little different. On normal transmissions the reason you see an RPM increase is because the car actually shifts gears. With a manual you don't see an RPM increase but you have to shift gears sometimes to actually make it up the hill. On CVT I don't know. I hate automatic transmissions. Both examples you stated are because you are running in a different gear. If you car is a manual your RPMS will not change with an intake. I guarantee it. Even with a CVT because the power gain is so minimal your RPMS wouldn't change. The RPMS / speed / gear on a manual is set by a physical gear and the only way to change it is if you actually replace the gearing. You can have 800HP and you would still rev the same unless you replace the gears. This is why race cars run adjustable racing transmissions, so they aren't limited to acceleration / top speed by the transmission.

 
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if you were keeping same gear, they should be same...
or your clutch was slipping.
or you put larger OD tires...

it's hardware, not software.

 
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To return for a sec to the CVT issue re: Blue... in CVTs the ratios are variable, but the crank is still mechanically locked to the wheels any speed past stall, if it were to maintain one ratio. This is why they get such good mpg -- there's no slippage outside the parking lot AND they can be set up to accelerate and hold the motor at peak output. So again a CAI/SRI wouldn't give them same gains as would be seen in a torque converter trans.

Even the worst of the modern slushboxes are pretty efficient (esp the new breed of 8- & 9-speeds from ZF). But they still can't match even a poorly-programmed CVT (like Ford's or Nissan's) on similar cars for efficiency. People hate the drone because it feels like the car isn't accelerating as fast... but that's a perception thing, plus programming for mpg. I know some damned fast snowmobiles, and they have no problem with acceleration when set up for it.

 
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Gonna throw in my pennies and get back to the original question, no not worth the money. SRIs and CAI on our cars really only make them louder and breath a little better. In five minutes you can remove the stock air box and tube and just leave the filter box on the throttle body and get the same effect as a SRI for free. You are then left with a 2.5" opening for air to enter the engine and the engine has a little more noise. Don't believe me? Try it!!

 
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When I did that it droned really loud at highway speeds but it does do the trick!

 
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It'll also have the same flaws as a SRI -- that it draws hot, dirty air from right next to the head. The heat is a good thing when driven in winter... but not where it gets warmer than 70-75 degF.

One of the benefits of the stock resonator setup is that it draws cooler, cleaner air from the front corner, generally away from hot parts and hot air drawn thru the rad... not to mention a bit of extra volume (why it's called a resonator) to help with filling in flat spots in the torque curve, and quieting intake honk. More restrictive, but also more drivable. Less restriction won't get you a lot of power with a speed-density MAP FI system anyway (though it will on the MAF-equipped DOHC Hondas, like the K20s).

I'm wondering why no aftermarket intake maker's taken advantage of the room the missing resonator leaves, to make a larger flat-panel filter box, then running a much larger tube to the same place the stock intake starts, so there's less total intake resistance. Having the filter at the far end of the tube seems like it's the worst place for it... in the stock filter box setup it serves to not only filter, but also to reduce turbulence before entering the TB, just as similar setups do on sportbikes. Probably because it's a lot easier to overprice a cone filter and a bent aluminum tube with some tacked tabs.

Actually... the D17 filter box is setup very much like the old VFR750F and CBR954RR sportbike airboxes, except with one big TB instead of 4 smaller carbs... and a lot less filter area/cc.