Air Box Question

[1qckser]

What purpose do the 2 lil containers conected to the airbox serve, are they present to reduce noise? or do they help with intake valve pulses or somethin like that? and if they are just there for noise then would it be a problem to remove them? Thanks:thinker

[Q45tech]

The entire air box system is tuned to minimize noise while not overly restricting air flow. At the same time creating WATER traps and drains to avoid hydrolocks.

From the front of the MAF [top of filter box after the filter] the worst total restriction to the atmosphere is 7.5" of water [roughly 1/4 of a psi]..........the oem factory filter only has a 1.0" restriction.

A 274 cubic inch engine can only ingest so much and the valves and head design are the major restriction. The whole system is tuned to have a negligable restriction until just past 4,000 rpm [the torque peak rpm], where it begins to be measurable on very sensitive equipment [manometers].

1 psi [28" of water] is roughly 6.6% so the whole system in front of the MAF leaves up to [1/4 of a psi] 1.65% on the table at 6,500 rpm and less than 0.5% at 4,000 rpm.

No filter no nothing in front of MAF might yield 5.0 HP at best. A K&N or other cone has some restriction so maybe a peak improvement of 2.5-3.0HP [below the repeatable accuracy of a dyno to accurately measure]!

The problem is the factory system is already a cold air intake [getting air from a plastic cone in front of condenser/radiator in a high pressure area [which adds around 0.75-1.2" of pressure at 80 mph [120 mph adds 1.9-2.5"].

Replacement Cone filter suck in heated under hood air after passing thru radiator and AC system in summer even winter.Every 11F rise in injested air temperature lowers the air density by 1% which directly reduces the engine power by 1%.

Thus the power difference between 32F air and 120F [88F/11= 8%].....humidity and real barometer are also significant effects].....but the radiator raises temp by at least 30-40F and the AC add 20-30F so a inside cone loses from 3-7% depending on ambient not to mention the radiative heat from the engine effects on injested air.

Hopefully you see that the small gain in lower restriction is immediately conteracted by the temperature rise and the net is almost always a significant loss unless some way is found to place the cone where it is only exposed to cool air flow, which creates water problems.

Sure racers with big engines use K&N but not in the rain or standing water and the air flow is routed so that the heat does add to problems.

[Q45tech]

I had occassion to measure the restriction of a G35 air intake system it was 5.3" of water almost 2.2" better than a Q in front of MAF ......0.078 psi better yielding maybe 1/2 horsepower more than the Q system.

Once you already have a modern low restriction cool air system, little can be done to improve it without a wind tunnel and supercomputer.

I can assure you that a team of engineers spent a solid year testing retesting the design of the Q air intake system. If more was available they surely would have found it in the 7 years it was used essentiallly unchanged.......if they could have made it cheaper without losing power they would have for 1994 or 1996.

All that convoluted plastic and tuned resonators cost a lot of money [try buying a total replacement - dealer cost half of retail] so figure the factory spends $160 to acquire the $390 worth of parts.......that's more than the alternator cost them!

I sure some engineers took a beating over the intake design but they seemed to have held fast. Compare it to the cheapo LS400 or BMW 745 or MB S500 units.

[Chally]

The airbox alone, here in Australia, cost just over $1000.00. I got one on a throw-out deal for $80.00. Good deal I think..

[911/Q45]

I've modded a lot of different cars and my experience is that you need to make a 30 hp change to even feel it, especially in a heavy powerful car like the Q. Any sacrifices you make to gain less than 30 hp are not worth it.

[1qckser]

I was just curious as to what the function of these items where, I need some room on that side of the car, Thanks for the awesome info

[Chally]

The first sentence of Q45Tech is your basic answer.

In some Korean cars, they actually just drill holes in the intake tube, & this actually works. (to a degree)Just like a muffler in the exhaust, they're there to interrupt & capture sound waves.

[Q45tech]

Actually if 2" of water colum restriction matters to you, drill a 2" diameter hole in the fender side of the lower air box section and with a flexible tube/hose plumb some air from the fender - either straight down [see the rubber plug or to the side, see the rubber flap].

This mod will change the restriction [to the MAF input] from 7.5" down to ~~~5.5 "........maybe 1 horsepower. [with a K&N dropin filter maybe another 0.25 HP]

With 28" to the heads.........you have only 3.3% TOTAL to play with........happy testing..........don't try to experiment without a accurate manometer as sometimes things that look good may actually hurt air flow.

PS: I have cut up 6 intakes experimenting

Don't even think of fiddling with the MAF or throttle body as minute changes will affect the idle and cruise.........they are both on the ragged edge of being too large for this application!!!!!!!!

Nissan traded off low rpm resolution [MAF too big] for an increase in WOT high rpm flow [the MAF has half the restriction of a similarly sized one from GM or Ford]............don't even think of removing the air straightening screen as the induced errors are gigantic for a <1 HP gain. Not to mention the replacement cost if a tiny bit of filter breaks off at high rpm and destroys the sensing element!!!!!!!!!!!!!!!!!

Keep remembering the new 2003 Q engine only produces 333 lb/ft and the old engine can make 330-335 with a JWT ecu.And you are then within 40-45 lb/ft of a full Indy methanol burning racing engine [375] of the same size.

4.5 liters [4494 cc] normally aspirated is just too small for a 4300 pound car to acheive serious performance.Isn't it strange how MB has creeped up to 5.5 liters and Chevy has been there for 30 years [5.7/5.66...350/346ci].

Watch Hot Rod TV, the new 4.6 mustang engine ;block and heads]looks to be a perfect copy of the old Q engine with less rigidity and block reinforcement...........oh my they have a 6 bolt crank girdle what will Ford invent next.

[AZhitman]

HAHAHA Ford's resorted to copying a 15-year-old Nissan engine design... And adding their own cheap-a$$ shortcuts. Typical ignorant basturds that they are....

Why every Ford car I've driven (Escorts, Contours, Taurus, Mustangs, Focus, Vics, Interceptors) has had significant driveability issues... And the American public (sheep) keeps on buying.

[maxnix]

Quote »Keep remembering the new 2003 Q engine only produces 333 lb/ft and the old engine can make 330-335 with a JWT ecu.And you are then within 40-45 lb/ft of a full Indy methanol burning racing engine [375] of the same size.[/quote] But the CART engine is 2.6L under high turbo pressure. I don't believe there is an Indy Infiniti 3.5L normal V8. But I am no expert on either series.

[Q45tech]

Infiniti had 4.5 and 4.0 non turbo racing versions in the past they never did too well. I should have used CART as an example not really Indy as this was old news.

The point is there are physical rules/limits about how much torque a NA engine can make ..................HP is a meaningless mathematical manipulation for the unwashed public to believe in and trade stories about!

[maxnix]

Damn! Where are (were?) these? There should be some great NISMO parts somewhere.

The discussion about optimal engine size vs. efficiency got me to thinking about the 5.5L SOHC 3-valve MBs, and wondering if their volumetric efficiency with any kind of assisted intake boost wouldn't be greater (more powerful) with a 4 or 5 valve head and two camshafts per bank that can be varied?

Did MB pork the pooch on this one? Audi S4 & S6 would seem to confirm this.