I'm sorry, but not factoring in ALL the other variables involved, (valve lift, duration, compression ratio, etc.) renders that theory useless when it comes to performance. Think about it: Just using those factors alone, you'd have to measure a stock 350 one-barrel carbureted engine from 1968, and a brand-new 5.7L LS2 using the exact same factors to determine their respective CFM capabilities? Doesn't work, my friend.

 

Uhhhh, yea it does. It's just simple math.

Which all (except compression ratio which has nothing to do with intake CFM) reduce the VE below 100% on NA engines.

Don't believe me? Look it up.

 

I am long familiar with what the theoretical math formula for CFM requirements works out to. That's not the point I am trying to get across.
I guess what I'm saying here is, of course I know that my little 281 doesn't need, nor will it use 1,000 CFM of flow capability, nor will it even need the 800 or so the CAI claims to have. Heck, I doubt those numbers are even accurate in a real-world setting, outside of a controlled dyno facility, But I can tell you this: There is no way in hell that the stock setup is delivering 550 cfm through that little rectanglular hole in the corner of the box! SO therefore, the open air filter, regardless of it's real CFM rating is allowing the engine to breathe better, and it's responding with higher power numbers. That's been proven by anyone who's ever bought and installed one.

 

Not trying to tick you off but....

A 90mm MAF has opening of 9.8 sq in
An 83 mm MAF (C&L) is 8.34 sq in
The stock 80mm is 7.74 sq in


The stock air box plastic opening is 12.5 sq inches. The rubber snorkle opening is 9.18 sq inches. (aprox)

The stock air box opening is larger than both the stock and C&L MAF, so that can't be the restriction.

 

There is way more involved than just the size of an opening to determine if it's a restriction or not. This is the reason that we port our cylinder heads, do three-angle valve jobs, and radius venturis and such.

 

I've looked up several conversion tables at different places on the internet, and they all calculate the 4.6 engine to be able to flow 410-450 CFM, depending on what VE and redline numbers you input into the equation.

I'm far from a physics expert, but it seems to me, that a STOCK 4.6 is not going to flow any more than 450 CFM, regardless of what size the air inlet to the engine is. It can't "digest" any more air than that. The stock MAF flows more than enough air. The opening in the stock airbox is capable of flowing more than enough air. So how does increasing the airflow beyond what the stock components provide increase performance, if the engine is only capable of using 450 CFM?

Forced induction works by pressurizing the air and forcing more of it (along with more fuel) into the engine. But in a naturally-aspirated stock engine, only as much air as the engine can use will be taken in. No more.

So, I submit that a proper CAI system provides a SMALL horsepower gain by introducing "cooler" air into the intake stream, not a greater volume of air. Oldsmobile was a pioneer of this concept back in the '60s, when they used hoses to duct air from either between the headlights or under the bumper to the air cleaner assembly. This OAI (Outside Air Induction) system was used on 400 and 455 cubic inch engines, and was good for approximately 10 horsepower. Following along the lines of this theory, it seems to me that providing a better QUALITY of air is more important than providing a larger QUANTITY of air.

With that in mind, what I intend to do is to keep my stock airbox, remove the rubber snorkel, and install a high-flow dry air filter made by AEM. The filter itself may provide no benefit over the stock filter, but I'm going with it "just because". Then I'm going to fabricate a ram air system that draws air from the lower valance area and ducts it directly to the stock airbox intake, similar to what Oldsmobile had. I believe this "cold air" system, along with a dyno tune, will provide as much, if not more, of a horsepower gain than the traditional CAI setup with conical filter. I'll know more later on this fall when I get it completed and dynoed. I may be right in my thinking and I may be wrong, but the dyno will tell.

 

JonW,

I 100% agree that intake air temp and quality have everything to do with higher performance numbers. I just don't believe that the factory airbox is delivering a nice, smooth 450 cfm charge of air to the TB. I think by the time it's done bouncing around through all those turns and sharp corners in the factory box, it's fairly turbulent air. I will say this, though...after installing the CAI on my car last week, I've noticed two things. 1. It's ever so slighty more sluggish out of the hole, and 2. It has a little more power up top. So, six of one...half- dozen of the other...Does it really provide a performance gain? Hard to say w/o a trip to the track. (Don't really care much for dyno numbers... I mean, if sheer numbers were all that mattered, we'd be "beaten" by every single '05 GTO in existence, right?)

In summary, I think the biggest benefit of a CAI is just good prep for future mods (i.e., tune, headers, nitrous, heads...)

 

Is there a link to buy one of these no time tubes?

 

Look into Airaid instead.. They offer the same no tune insert and also offer much better quality and lower price..

http://www.americanmuscle.com/airaid-cai-0509gt.html