all i have to say is go YO, that test and the conclusion was bogus with nothing substantial to back it up.

-steve

 

Larry - I still don't understand what you mean by "cold air" portion of the airbox.

You've got an airbox and an air scoop on the max. Are you talking about losing the scoop? I believe there is somewhat of a slight ram air effect with the scoop attached especially at highway speeds - plus you can eliminate just about any possible restriction this might have with an OSCAI setup (see sig).

 

Gawd, you folks sure do have your panties in a huge ruffle over this one....

The premise of what Larry measured is correct. The stock air inlet "scoop" is a source of restriction. Thus, he measured vacuum in the intake manifold, which indicates that the intake system is not able to supply sufficient air to the engine when the engine is running at higher rpms. The volume in the intake manifold responds by expanding and the pressure drops from ambient. Remove the intake scoop, though, and voila! you've uncorked the intake. Measure the vacuum with only the filter housing in place and there's no more vacuum. An efficient, unrestrictive intake system would respond under the same conditions by showing little vacuum at the manifold.

The point some of you seem hung up on is that the engine pulls vacuum, right? Heck, it's a pump, so it's trying to "suck" air into it. "Suck" implies vacuum, right? Not quite. Yes, the cylinders are *trying* to pull vacuum as the pistons travel downward from TDC but an efficient intake system would respond by FLOWING AIR...enough air that there would never be a drop in pressure. The increased volume in the cylinder would be instantly filled with air from the intake. An engine is not a closed system. If the intake were sealed off, then yes a vacuum would be pulled inside the intake as the volume increased inside the cylinder. This is not the case, though.

Another side note sorta tidbit: The reason why the stock airbox makes more low end power over the cone intake is...taaa daaa...volume. The stock airbox has more air volume than a cone intake, which decreases the resonance frequency of the intake system (system being the ports on up to the inlet). This drop in resonance freq tunes the engine to a lower rpm. It's a fairly minor rpm drop, though, but people "feel" it since the torque comes on just off idle. This is also the reason why people feel more low end torque with the CAI than all other intake systems. That ~1.5' long 3" pipe adds quite a bit of volume. This is also why people feel the cone intake beats the CAI at higher rpms...CAI has a lower resonance freq than the CI.

Everyone always focuses on flow rate and velocity and assumes an IC engine is a constantly-flowing air pump. It's NOT. Not by a long shot. It's a cyclical system that starts flowing then stops flowing at a high frequency. It's a DYNAMIC system, not a STATIC system. Resonances abound and are a critical factor to engine performance.

That all said, the general results of Larry's experiment do indicate that there is some airflow to be gained by simply removing the stock intake scoop. However, whether or not it flows more than a cone intake or CAI requires more accurate method of measuring vacuum...but vacuum IS an accurate way to judge restriction. Also, just because the stock box sans piping and cone intake were to, hypothetically, flow the same, that STILL does not mean they make the same amount of power. Both will create different resonant frequencies in the intake system and will tune the engine to a slightly different rpm. Likely, the cone intake will resonate higher, thus make slightly more power, but consequently make slightly less low-end torque. Overall acceleration, however, might well be the same.

 

Yes, he's talking about ditching the intake "scoop". BTW it's not a scoop. It's tucked up above the bottom of the hood and receives no forced air while driving. It's primary purpose is more for noise reduction than for obtaining "cold" air. It's a nasty, fugly straw for your engine to breathe through. Cheap, easy noise reduction. Restriction is one of the most effective methods of noise reduction (just look at the stock exhaust on most cars).

 

Keven97SE,

Bless you Kevin! Finally somebody that understands engines and what I am saying. Well said!!! Whew!!!

sleepermax,

I had not seen a pic of the OSCAI. Does the same thing that I have recommended and better. It appears to draw cool from the bottom. Neat idea!

Keep in mind though, this may not suffice with aftermarket exhaust and/or other mods. More testing would have to be conducted after those mods were done. Quite possibly then an aftermarket inlet may be required to optimize flow to the engine.

 

Then why is it NOTICEABLY cold to the touch right after turning the motor off. Especially considering that a very hot radiator hose sits right below it.

There is a ram air effect, although slight. There has to be - it may look to bu tucked up but if you look closely when closing your hood you'll see there is a an almost direct airflow path into the mouth of the scoop from outside. The edge of the frame where the scoop sits is even tapered.

I certainly understand your explanation about the resonance frequency being lower with the stock airbox. Most of us use our max for daily driving so I personally WOULD want this lower. Although this obviously isn't the optimal set-up for the track!

 

Lets, cool out people, this is the most interesting thread on the org that I've fell upon, lets not have it locked for pete sakes. I am really learning something with this, now only if someone could prove there point already.



proceed...

 

damn straight. i've learned so much from this thread.

Keven97SE and Chimp DJ,
if i made the intake piping larger (therefore increasing volume) i should be able to notice a difference in low end, correct?? is there a point of no more benefit with increasing the piping? like can i go too big and it won't help anymore.

 

At some point, it won't matter because the maf and TB sizes will become the limiting factors(if not the engine itself). You can't just use bigger and bigger pipe to get more hp.

 

ok, that makes a lot of sense now. so wouldn't the maximum size of piping be the size of the TB and MAF, so anything at all bigger would have no effect. therefore the only was to increase volume would be to increase the length in piping.

 

Keven97SE, you had your panties bunched too.

Your idea of an "efficient" intake system makes sense, but think of it this way, it does exist. If the intake system was able to be efficient, you'd be on that line of having vacuum, and having 0.01psi boost, like RAM AIR.

Thanks for starting CAI vs HAI battle
It was unnecessary.

Thanks for repeating what I said earlier

As for your comment on motors and "suck."
You shot yourself in the foot. Read it again. I won't quote it, but read it really carefully. I found a boo boo.(Maybe my own, but, we'll see.)


Obviously you can gain airflow by removing that side duct, even a 10 year old would say that ?
Flows more than a CAI or HAI ? Stop making me laugh.
Power-point taken well.


That was a cheap shot, made more contribution than yourself, so sit back down. unbiased opinion my left nut. Business aside, this concerns his business, not yours. If you have a "cheap" comment to make, take it to PMs or emails.

 

Victor, in theory it works, I've never tried it.
I think there was a misunderstanding between the lines.

My fault on this one, perhaps Jeff missed it.
2.5" @ TB, expansion chamber between MAF and TB(4.0"-4.5" dia.) piping, 3.0" @ MAF, MAF+ Adapter/Filter.
_____
_/ \__
_ __###>>> <~~~YOU GET THE POINT.
\_____/

 

What did I say that promoted CAI or HAI over the other? I simply stated what the resonant freq for both are and what that translates to in terms of power. I started no battle. Simmer down.

What are you talking about?

Look, if you can't even bother to point out my mistake and just say "you made a boo boo", then find another thread to harass. This type of comment adds no value to this thread.

That's the whole point of this friggin thread, dude! That removing the inlet scoop removes a restriction and allows the stock filter box to flow better. Why did it take you so many harassing posts to admit it?

I never said that. Read my post again. I agree that either the HAI or CAI are less restrictive than the stock intake sans inlet scoop, just not a whole lot better. The stock inlet scoop is a large restriction and removing it make the stock filter box breathe a whole lot better. PowerPoint? Yes, I like that software a lot. Allows you to build great presentations [/sarcasm]

True. I apologize.

 

There's only so much room to work with under the hood, so you can't go with a massively long or large diameter intake pipe.

That limitation aside, what would happen if you added a larger intake pipe, the resonance frequency would drop and the motor will tune to a lower rpm. You'd gain low end torque. HOWEVER, since the torque curve would have shifted to a lower rpm, high rpm torque would DROP, which would likely mean a loss in peak HP. The engine would be stronger down low but weaker up top. You would need the middle east variable intake to counteract the high rpm torque loss.

Even if you did lose top end power at the expense of low end torque, though, that doesn't mean the car would be slower. It might be just as fast if not faster. Only accel testing before and after could.

 

chimp dj, i couldn't make out your diagram correctly but i think i understand your statement on the size of the pieces, check this out:http://pegasus.cc.ucf.edu/~vs58993/intake.jpg

if that's correct, i'm going to try it out. i'd rather have more low end rather than more top end.

another question, is it ok to change the piping that house the MAF sensor to a larger diameter?? i figure we can't cause it'll mess up readings, but if we can than that would subtract a bottleneck from the system.

 

I won't speak for ChimpDJ, but yes your drawing would provide a setup that would boost low end torque.

The MAF assembly includes the housing. You can't change the housing even if you wanted to, and if you could, you'd totally change the calibration of the sensor.

FYI the MAF is not a bottleneck in that it does not offer a flow restriction. At all. It's very big for a n/a 3L V6. It does prevent you from hogging out all the inlet piping, though, and obtaining an even lower res freq.

 

alright that's cool. i'll see what chimp dj's got to say, then i'm going to go work on that badboy.

if it doesn't work, then oh well, it gave me something to do. how much are dyno runs usually?? maybe i can go get a few dyno's done, with stock, oscai, and then one with the bigger 4-4.5" diameter expansion piping. maybe i'll get some gains, comparable to aftermarket intakes... lol.

 

So if I get this all right, I should put a Q45 TB and MAF, get the ECU adapted with a S/C and 3" y-pipe, exhaust and Cat, also let the fuel boost pump on all the time to prevent starvation.

 

thanks hogan. while my opinion might be slightly biased i understand fully what's going on here and the dynamics of an intake system. he measured the wrong measurement to say one "flow's" better. also there are many other factors liek i said, intake velocity and turbulence that aftermarkter systems eliminate, some more then others.

 

This is also the reason why people feel more low end torque with the CAI than all other intake systems. That ~1.5' long 3" pipe adds quite a bit of volume. This is also why people feel the cone intake beats the CAI at higher rpms...CAI has a lower resonance freq than the CI. <~~posted by you




If you want some low end, custom build an intake w/ 2.5" tubing @ TB expanding out to 4.0-4.5" then to 3.0" for MAF, and MAF Adapter and filter.



My Mistake, I read something wrong in your post.



I know, but the point is that, his experiment was not worded properly, poorly executed, and I pointed that out several times, but he insists he is right or agrees w/ someone who "understands."





Yo its ok...

 

Victor,

http://pegasus.cc.ucf.edu/~vs58993/intake.jpg

Exactly, what I had in mind. I can't be as creative behind a screen.

Steve, yo its ok, no one deserves a personal attack on the .org, unless it was me who was doing the attacking, but look where that got me, right ? Just trying to gentle w/ a big 3.0" Pipe.

Keven, wanna see a bottleneck of a MAF, get the SR20DE MAF and see how much of a bottle neck that is.

 

I've seen those types of intakes for sale for Accords or something. Always wondered what the hell was up with those. Tried them?

 

the only problem with gthat on a 2k2 is the TB is 3inches not 2,75 like the 2k1-back so the effect might not be as great.

 

seen them, drove a Honda CRX w/ something similar, I'm biased towards Hondas, so I couldn't tell. If I could adapt one to a Maxima, then I would try, but at this point, its useless to me.


dmbmaxima88, Great Gobs of Monkey Shlt, no wonder them MAFs keep blowing out.
3.0L V6 sucks through a 3.0" MAF.
3.5L V6 sucks through a 2.75" MAF.
They sell Silicone reducers.

-WTF is Nissan Thinking ??

 

i think you have the MAF's reversed from what dmb said. i took off my scoop just now and it makes a difference i think, i should reset the ecu maybe though.

 

My mornings suck, I can't function in the morning.

Didn't read TB, folks sleep is a good thing, always get your 8 hours, or you'll post like an a$$ like me.

Thanks for the correction, I was right about using silicone reducers.

 

yes you were.

 

i meant the other way around, 3.0 engine through a 2.75 TB and 3.5 throught a 3inch TB. wooops
and i do use reducers but they are plain rubber.

-steve

 

Did anyone notice the ONE MAJOR problem with Larry's test.

He said that once his engine reached 5000 rpms, it started to have vaccuum. His engine makes it's max HP OVER 5000rpms. In his test he simply looked at the low-end NOT the top end. If his theory is correct then the stock intake even with the cold air piping removed is RESTRICTIVE above 5000 rpms....most of the 1/4 mile is done ABOVE 5000 rpms...and the max power on a dyno is ABOVE 5000 rpms....there's your "simple" answer...to ALL questions.

 

good point. like with a CAI and 1/4 mile times, a cai might give you slightly better low end but when tyou race hyou never go below 4200rpms or so and that's where a pop/frankencar shines even more.

 

Larry never said that. This dang thread is so long it's easy to confuse the wording, but I re-read everything and what he said was that the stock intake (incl scoop) yielded 0.5"Hg vacuum (~0.25 psi) at 6300 rpm (approx. HP peak). No vacuum was measured at the same rpm with the intake scoop removed. Larry later said that on the entirely-stock intake, he didn't start to see any vacuum until 5000 rpms-up. There was no vacuum ever on the removed-scoop setup.

A nice little tidbit is that you can approximate the HP loss due to the vacuum via a correlation with intake pressure. Power more or less follows intake pressure. Max HP at the wheels is, say 200 HP. Atmospheric pressure is 14.7 psi. The measured 0.5"Hg loss equals 0.25 psi. The HP loss due to vacuum can be approximated by 0.25/14.7*200 = 4 HP at the wheels. Not really that accurate of an estimate but it gives you an idea what ballpark HP loss you're getting due to the vacuum.

Common sense approach: If you shoved a rag inside the intake piping upstream of the MAF, you would expect to see an increase in vacuum at the intake manifold due to the engine trying desperately to breathe and not getting what it needs due to the restriction.

 

ok...well I don't think he was very clear on that. Anyway, all the FACTS (dynos, 1/4 E.Ts and traps) show that aftermarket intakes DO make more power than stock intakes. I don't think anyone can argue that....

and about everyones "butt-dynoed" low-end power loss with an intake...all I have to say is

 

Quoted by Kevin

Thanks again Kevin for straightening these guys out!

dmbmaxima88,

I measured my throttle body and mass air meter on my 3.5 2002 Maxima so we will all know for sure. The throttle body is 2.765 inside diameter and the mass air 2.751.

 

i'm talking OD. sorry for teh confusion. it's about 3inches, slightly more.

 

dmbmaxima88k

I added ID to my post to avoid any farther confusion as well.

 

k thanks, i was jsut using what i know from making the intakes. i need a 2.75 inch coupler that just squezes onto 2k-2k1 and a 3 inch that just squezzes onto a 2k2.

 

what im wondering is how nissan doesnt know all this and why they all left it how it is....there is a reason why the exhaust,filter ect is how it is

 

sound levels and comfort for most drivers, 95% of the people who buy maximas don't want it faster or louders so they cater to the majority.

steve

 

yup. i took out the scoop from the information on this post, and guess what??? it's louder. sounds almost like i have a cone intake on there.

 

I tried this too and it did make a slight difference at highway speeds. But I've found the OSCAI to be better as long as it's properly set-up (because you can introduce some turbulance if the downward pipe is angled incorrectly). I'm very sure there's a slight ram air effect with the scoop intact.

By the way I've also tried CAI, WAI, ect. And although I liked the CAI the best it's still not as good as OSCAI from a standstill - it's great from a roll though. It all depends on what you're looking for. I do a lot of stop and go driving but if I did mostly highway driving I'd stick with the CAI. The torque you get at highway revs (3-4K rpm) is awesome. I could quickly pass up most anybody effortlessly and smoothly! OSCAI with K&N is not too shabby compared to it though.

And, yes, these are all butt-dyno impressions but everyone can tell if you're accelerating or going at a steady speed. Some people are more perceptive than others - so I guess those of you that say butt-dyno doesn't mean a thing don't HAVE as sharp a sense of speed and acceleration as others.