Are cold air intakes really unnecessary?

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Corwi
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Are cold air intakes really unnecessary?

Postby Corwi » Tue Jun 04, 2019 5:54 am

Hello everyone!

So today I was notified by my auto-shop teacher that cold air intakes actually do not gain power but just makes it unnecessary and says to keep the stock air intake box. He actually advocates keeping an engine all stock with no modifications because that is not what the ECU was tuned for nor was the engine made for those kinds of MODS. What is your opinion on this?

BTW, I have the following MODS to my Ka24de (came with these when I bought the car, I am not the one accountable for these modifications):
1) DC headers 4-2-1
2) Injen CAI
3) 5Zigen Border III Cat Back Exhaust.

My other questions:
1) Is it worth having these MODS on my car?
2) What Modifications are actually useful for a stock engine like my ka24de?

I appreciate any help, thank you very much!


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Thupertrooper
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Postby Thupertrooper » Tue Jun 04, 2019 7:36 am

Its been proven. ECU can be tuned.
CAI by itself isnt as effective as it is with a combo(exhuast,tune)

Proven for years

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underworld1001
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Postby underworld1001 » Wed Jun 05, 2019 1:59 pm

So its a safe assumption that the combination of your items will increase upper RPM HP/TQ. Given that the KA generates the a lot of TQ down low, those mods aren't that bad. Basic bolt-ons that most people would do. Plus you have a DE and not the E, so you have the better engine.

Bolt-ons the KA are like bolting on the VQ. They help, but won't make a huge difference. The engine is pretty well tuned as it is. You can go the turbo route, but you'd have to header for a turbo one (or rear mount it). If I'm not mistaken the KA can usually handle about 300hp on stock internals, though I could be wrong on it.

If you're looking to make a dragster, then you'll have to cough up some cash for internal parts (pistons, cams, etc.).

As far as the ECU goes, it'll adjust enough in stock form to adjust for the bolt-ons. Not all cars are like this though and some will toss the CEL indicating something is wrong with the car when it's not.

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palmerwmd
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Postby palmerwmd » Wed Jun 05, 2019 10:51 pm

I also do not believe in cold air intakes..
modern nissan intake boxes are already well positioned as it is.
Same with hiflow intakes of filters.. they dont really increase flow in an appreciable manner.

But they are easy mods to do so people enjoy doing the,

higher flowing cats, plus exhaust and then a retune on a dyno ( I know the $$ are adding up) are a proven way to make bolt ons effective..

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smj999smj
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Postby smj999smj » Thu Jun 06, 2019 2:32 am

I don't think there's a general answer that fits all applications in regard to this question. Most modern vehicles, at least since multi-port fuel injection became the standard in the late '80's and early '90's, usually have a factory air cleaner that is actually a "cold air intake" by definition. The bigger question is whether the intake system in the vehicle restricts the air flow going into the engine under its operating conditions? If the vehicle and its engine are going to be operating at high RPM for a length of time, then it's possible a less restrictive air cleaner or intake system may be beneficial. As far as the R51 Pathfinders, the stock air box and air cleaner are actually pretty good. On the factory-supercharged Nissan Frontiers and Xterras of the early-mid 2000's, the stock system is pretty small and has several resonators included in its design. I can tell you by personal experience that replacing the factory air intake (which is a cold air intake design) with an aftermarket system like K&N or aFe's does make a noticeable improvement in performance (along with making it a lot noisier, for better or worse). Modern ECM's will be able to compensate for minor bolt-ons to the engine. Older ECM's like used in GM vehicles has its software on a PROM chip which could be removed and replaced easily. Older Nissans had the software on a chip soldered to the circuitboard, so reprogramming consisted of removing and re-soldering a new chip to the board with different software. In the 2000's, Nissan started the move to programmable ECM's (as did most other manufacturers), so performance tuners were developed by companies like Superchips and Diablo which allowed DIYers the ability to reprogram their vehicle's ECM software via the OBD II port using one of several custom tunes on the programming device (i.e. "tow," "91-octane performance tune" or a gas saver tune). These were made for stock vehicles with no or minor bolt-on mods. Those with more serious mods could get an interface to work with their laptop or get the ECM tuned by a professional company specific to their vehicle, i.e. UpRev.
It's all a matter of what you want to do with your vehicle and how much performance you want out of it (or, can get out of it)....which also is relative to how much money you want to spend.

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ShipFixer
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Postby ShipFixer » Fri Jun 14, 2019 3:43 pm

Adding some engineering insight here...

Yes, CAI's work. No, they do not necessarily require a tune or exhaust. I had a great AEM model on my Sentra that boosted HP and was advertised as not requiring a tune (and was CA legal to boot!). They had bigger CAI's for more volume through to match a higher fuel tune and exhaust setup, but that's not what that one was for.

The big advantage of the CAI is colder denser air. More air + more fuel = higher efficiency and more power. Yes, your current setup takes air from the same place in the fender. But a.) the resonator/air box combo has what we call a higher "hydraulic diameter" (just think 2D surface area the air flows through) plus more turns to defeat intake tract sound from leaving the vehicle. A wider pipe/bigger hydraulic diameter means lower velocity through the intake plumbing, and more time to be heated through conduction through the sides of the intake. A CAI is designed to reduce the amount of heat you absorb from conduction through time next to the engine as well as providing sufficient air intake volume.

So do you need a tune and exhaust to use it? Not necessarily, no. Your vehicle depends on perfect stoichiometric combustion to keep operating, and it has a range of air intake it can accomodate. So think about a mild CAI just dropping your intake temperature 10-20 degrees. Your truck doesn't behave wildly different on a 60 degree day vs. an 80 degree day...slightly higher power but it's within the range of what it can accomodate.

If you significantly boost intake air (which is a related rates problem, not just the CAI) then yeah, you need a retune plus exhaust to maintain stoichiometry through the engine. If you're outside of the amount of air the computer is programmed to see it needs to be adjusted.

This is incidentally along the same lines of mythology as "back pressure = torque" from the 80's. No, back pressure from the exhaust doesn't equal torque, those vehicles just weren't tuned appropriately for the increase in air volume through the engine.

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Zen_master
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Postby Zen_master » Sat Aug 10, 2019 5:59 pm

As others have said CAIs can potentially work, with most of the benefit coming from it augmenting other mods (headers, exhaust, intake manifold, etc.). In my experience the air intake on the pathfinder is pretty good in that it actually ports to the fender cavity, doesn't have a ton of restrictive bends, and the materials used are fairly smooth/low drag (on the VK56 by the way). Since no one makes a true replacement for the V8 path and considering it's already pretty good I opted to leave mine alone. On virtually every other vehicle I have owned I have installed a CAI because the aftermarket versions were superior in some way, eliminating one of the OEM flaws (too restrictive, no port to external air, lots of high drag coefficient material or whatever).

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smj999smj
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Postby smj999smj » Sat Aug 10, 2019 6:36 pm

Zen_master wrote:As others have said CAIs can potentially work, with most of the benefit coming from it augmenting other mods (headers, exhaust, intake manifold, etc.). In my experience the air intake on the pathfinder is pretty good in that it actually ports to the fender cavity, doesn't have a ton of restrictive bends, and the materials used are fairly smooth/low drag (on the VK56 by the way). Since no one makes a true replacement for the V8 path and considering it's already pretty good I opted to leave mine alone. On virtually every other vehicle I have owned I have installed a CAI because the aftermarket versions were superior in some way, eliminating one of the OEM flaws (too restrictive, no port to external air, lots of high drag coefficient material or whatever).
K&N makes a CAI for the V8 R51.


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