IStnr

i made a post about this in another thread randomly but had meant to eventually make a thread with good pictures and maybe some results. however, this will have to do for now...pics/vid taken during install with phone. nothing too big, just a little project with the car. i have been wanting to play around with the stock air box, so i did one night...

purpose: increase the flow to the stock air box from a cold air source while keeping the stock air scoop fully functional


old Honda intake duct i found (probably from my old rsx type-s):



here's the hole i cut out with a dremel (had to cut the box AND scoop pieces):



video of the duct rough fit into the hole:

http://myselfmyself.com/BG/IS/IS CAI mod.MOV

duct rubber trimmed:



looking at the duct inlet through the hole next to the fog light:



plenty of air flow down in the fender but just for fun:



this is on my IS 350 with JoeZ intake tube, HKS filter, and Tanabe MT. i simply wanted to open the air box up a bit and get a little louder sound out of it...maybe a slight increase in hp, throttle response, less heat soak, etc... probably nothing substantial, but the fundamentals are there...

there really aren't too many options in places to open the stock air box up (and keep the stock scoop), so i decided to use the end of the scoop. i made the hole slightly smaller than the rubber tube (seals under compression). the new hole was also cut at a location that did not interfere with the stock scoop's min. cross-sectional area. thus, the limiting factor is now increased to the area at the intake box's larger square inlet...not the stock scoop that necks down at one point. this should increase it's ability to flow air...and form a colder source. also, the effective plenum volume (basically the immediately available air) of the air box is slightly increased.

i may or may not 'improve' this mod in the future, and unfortunately, my baseline for comparison with the car sucks since it's not my daily...and i've only owned it for 6 months. plus, my exhaust is pretty new too. i do think it's a bit louder, and it does seem to respond quicker to throttle input. probably mostly placebo. i do know that it certainly doesn't hurt on those WOT highway pulls!

enjoy. comments are welcome.

DRivera250

iTrader: (6)

i don't mean to burst your bubble but the stock air box is a form of CAI begin with. the scoop is right in front of the car and it appears to be larger then your final product.

IStnr

the stock scoop necks down to a smaller area than the opening to air box itself. it doesn't maintain the same shape you see at the front. open your hood, take all the unnecessary plastic off, and check out your engine sometime! haha

DRivera250

iTrader: (6)

hmmm... i have seen it.

smokyis350

iTrader: (21)

I don't know if this will be beneficial. Seems like the stock snorkel is pretty good already.

These kind of mods will be difficult to prove if there are any gains. Since a dyno would be useless because this relies on wind resistance to increase air flow. I would be interested in the 1/4 time.

new.era.13

iTrader: (10)

its a nice mod. but the stock air intake, gets more than enough air from the snorkel than actually needed.

Kurtz

iTrader: (1)

This.

Even been tested- the stock intake supplies more air than the engine is capable of using. That's why gains from intakes are so tiny on the car, the only benefit is a slightly smoother airflow from something like a Joe Z pipe.

heyarms

iTrader: (5)

My logic about your intake is it might be doing the opposite of what you want... If the stock intake is bringing in more air than the duct you put in, your new hole may just be releasing un-needed air down the tube due to the force of the air coming in from the stock snorkel. Just a thought.

IStnr

yup- this was my only fear...decreasing any ram-air effect. however, i'm pretty sure it's not substantial to begin with, so it's not like there was much to lose. not to mention, the pressure at the inlet of the 'additional duct' (in the fender) doesn't come close to a vacuum, as seen within the intake system under load.

in regards to some of the other comments:

- i'm sure the stock snorkel supplies enough air flow for a stock set-up. however, not every 2GR-FSE has the same 'amount of air flow it needs.' this is a variable that is highly dependent on the modifications. in other words, a highly modded N/A 2GR-FSE 'needs' (or rather, can take) more air than the stock snorkel can supply. just think of a larger TB or even an ITB set-up. you really think that gives you zero increase in air flow? maybe...if your exhaust is the super small...or you have another limiting factor.

- it should be noted that the minimum cross-sectional area of the stock snorkel is VERY close to the cross-sectional area of the intake (JoeZ) tube. additionally, there's the pressure drop across the filter, as well as pumping losses seen in the intake tube(s). this all adds up to more pressure drop (decreased air flow capability) within the intake tube compared to that of the stock snorkel that has the same cross-sectional area (because it's very close or with a ram-air effect, even above atmospheric pressure).

- speaking of pumping losses (think of throttle response), the additional duct can help with this. it can't hurt to decrease any pressure drop prior to the air box opening, especially considering the stock snorkel isn't significantly larger than the intake tube/TB. the opposite of this would be a really long intake pipe/snorkel/duct...which would certainly result in a power loss at some point.

- i highly doubt anyone has done any significant testing at speed (ram-air effect). without that, you can't decisively say that there are only 'tiny' gains to be had in the intake. sure- there may be little gains to be had under dyno'ing conditions, but that is not a direct correlation to the fluid dynamics and an intake's performance at high speeds. also, once again, i'd be willing to bet i could show decent gains (i.e. not 'tiny') from the stock intake to an aftermarket intake on a decently modded 2GR-FSE...on the dyno.



i'd just like to reiterate- i don't think this mod is anything substantial. however, the fundamental concept and theory behind it is sound. as a R&D ME by day, this was simply a fun, 2 hour project that had little to no negative consequences...only minor improvements, if any. these improvements could be related to a number of intake-related phenomenons...as mentioned in the OP and discussed a little further in this post.

i also realize the Lexus/IS community is not nearly as performance oriented and doesn't indulge in the same sort of grassroots engineering (at least by the typical owner or on the forums for that matter) as with other vehicles i've owned and modded. in fact, it almost seems at times as if technical discussions/explorations are considered faux pas around here...

Kurtz

iTrader: (1)

Can you show me any examples of "highly modded N/A 2GR-FSE" 2ISes?


No, it's really more a question that Lexus engineered the motor really well, and then locked it the hell down to any further efforts.

Hence why there's so little to gain even from parts produced by major aftermarket companies.

If there was much "easy" hp to unlock in the motor Lexus would've done so in the 09 refresh to try and keep up "on paper" with the G37 and 335i (despite the fact that in actual performance it's faster than the G37, on paper it has less hp...)

Even 5 years into production applying every street-legal +hp NA mod available to the IS350 (both of em!) gains you a whopping 10-12 rwhp.

Among illegal mods the results all suck for the cost... the PPE headers are about the only exception, just cross your fingers it's installed right and no CEL... even then you're talking under 20hp. A midpipe? 1-2 hp for a couple hundred bucks... insane. Supercharger kit? $6000 for 40 hp... thanks to the joy of 12:1 compression. Turbo kit? Every attempt has been a laughable disaster so far.... and costs are pushing you into the area you might as well just have gotten an IS-F.

Engines swaps are possible... but you get to pick between just a bunch of labor and nothing factory working... or several hundred hours of labor and only a few factory things won't work.... so again an IS-F might make more sense for most.

Nitrous seems to work pretty decently, but again the legal thing, and it's not always on.

So it's not that mod discussions are faux pas around here, it's that there's just not a lot really worth discussing... thus do you see 687 threads on "which exhaust sounds the best"

Initial B

iTrader: (2)

Kurtz - you've proven to me in many of your posts that you're one of the more knowledgable/helpful guys on here - so no attack intended, but those 2 statements are contradictory and can't both be true

brociouz

iTrader: (65)

^ They're not contradictory. He's right in saying that there's more than enough air supplied by the stock intake, but (slight) gains can still be had with smoother, less turbulent airflow.

Kurtz

iTrader: (1)

Yup... there's more to airflow dynamics than just volume.

(which is also why simply slapping a crazy-big exhaust on a car isn't usually the best plan)

Initial B

iTrader: (2)

the "more than enough' phrase is what I have issue with. It implies that motor was already receiving more air (volume, pressure, whatever) than it can process when the intake piping was stock, which is proved incorrect when you can slap on the Joe Z pipe and gain ~5 hp.

Kurtz

iTrader: (1)

But to be really clear here- exactly what i said:

That means, pretty straightforwardly, more volume of air than the motor can use.

It's why putting a huge honking cone filter on the intake doesn't help because the car doesn't need "more" air. It already has more than enough from the stock intake/filter.

But the Joe Z pipe provides a smoother direct path for that "enough" air to get into the motor.

As I said, if volume was all there was to airflow dynamics everyone would drive around with 5" exhaust pipes on their cars.