Flowed both bridges last night.

@ 2" of vac

stocker halltech
377 cfm 368 cfm

Both flow more air than any LSx N/A motor I've dealt with can handle. Interesting however, to note that GM has some serious design in the stocker, and it is NOT a restriction like so many think.

 

great...
if only you would have posted this info last year, you would have saved me 1 hour of aggrevation of removing the MAF off the stock bridge and onto my halltech stinger.

 

haha, i'm sure lots of people spent their hard earned dollars on air bridges. i know a few that did. i'm sure they have their merits...i just cant think what they would be? looks? mounting nitrous foggers?

 

Mmmm, Jim Hall has a flowbench as well and he insisted that his airbridge outflows the stocker. The simple fact that the Halltech airbridge cross sectional area is larger than the stocker suggests he is correct. Perhaps you are not testing it the same way he did. From what I've read here in the forum, most people know that the stock air bridge flows adequately for non-artificially aspirated engines. It's the super and turbo-charged engines that require more flow that the stock intake components can provide. Besides, at the price Halltech charges for the Stinger package, the airbridge and smooth TB couple are like freebies compared to other systems that contain only an air filter.

 

thanks, interesting info. I've always thought to myself that the accordian type pleat present in the stock unit CAN'T be helping flow, as it would probably induce turbulence, but I can't justify spending $170 on a 'smooth' unit.

I appreciate your research on this.

 

What was the flow velocities?

 

I can say, that I saw with my own eyes that the stocker out flowed the halltech. I had a gentlemans wager of $1 with a friend that the stocker flowed as good as (i.e. within a few cfm) his halltech...I was dumbfounded when we saw it did 'better'. FWIW, I'm not bashing the halltech (or any others)...just saying the stocker is just fine. If you do the math, you can see that the cfm each of these units flows is waaay more than 99% of these motors need.

 

You could keep the stock air bridge but replace the stock bellows coupler with a smooth silicone coupler for about $50.00 (Eklers, Mid America).

 

cant be that turbulant if it flows as good as it did! air flow is a strange beast, sometimes the 'golf ball' effect can help quite a bit.

 

When you replace the accordion couple with a smooth coupler all you get is increased noise and more stress on the engine. The accordion coupler was designed to muffle the incoming air sound and handle the twisting of the engine during accel/decel. The CPU firmware looks for the air pattern the coupler creates and compensates accordingly. If the smooth couplers made more hp, then the Z06 would have had it on. Even the C6 Z has that set up for the same reason.

 

This is interesting, because when I put my Halltech bridge on, while it sounded louder, it actually seemed like I was not getting as much power as the stocker. I swapped back and forth a couple of times, and I thought it was just me. Maybe I wasn't imagining things after all.

Anybody else notice the same thing I noticed?

Sure, many might say you can't feel something like a few CFM, but the computer adjusts for this, which would probably result in a tune change in the areas of mixture, and maybe even spark, which would then translate into a performance change, albeit a small one. And, other Corvette owner buddies of mine have said in the past that I seem more sensitive to changes than they do.

Also, anyone ever tested actual driving performance between the two bridges?

 

Can you explain this statement?

 

Personally, I feel that you'd be hard-pressed to notice a difference in real-world driving OR in a dyno test. The simple fact that the Halltech bridge has a larger cross-sectional area throughout its length tells me that the "flow bench's" method of measuring flow is closely tied to its ability to reproduce typical engine intake requirements. I believe that the flow bench's accuracy between two or more back-to-back tests would produce the differences wango is posting. In other words, I'd bet that if the flow bench were to gradually increase its "pull" of air through the bridges, the Halltech would outflow the stocker and continue to pull away. The law of physics cannot be fooled.

 

Good point, Dave, and I agree to a degree... I think. What I mean is, I was actually shocked to discover that the stock airbridge seemed to perform better than the Halltech. I must admit, though, that from a 25mph roll, I mashed the pedal, and when the powerband kicked in, it sure FELT like the car accelerated faster with the stock airbridge than when the Halltech was in place.

With that said, I did not do any SOTP tests at sustained high RPM driving... to clarify, I did not run 3rd and 4th to redline or anything like that. I basically stuck to mid- to high-rpms in 2nd and 3rd.

Also, to me, physics would dictate that a larger bridge is not necessarily the entire story; I believe the SHAPE of the bridge COULD be more important, because I'm sure you'll agree that the VELOCITY at which the air travels into the intake is more important than the volume of air held in the airbridge. Thus, I believe the best design for an airbridge is one that would result in an accelerated air intake rather than just a LOT of air. So, Wango Tango's test could be indicative of a good factory design. However, like you said, the real question is whether or not the Halltech outflows at higher rates.

 

Any old dyno data on this, he asks as he polishes his newly bought Pomagranite Red Haltech Air Bridge

 

The CPU firmware looks for the air pattern the coupler creates and compensates accordingly
GM did a hell of a lot of design testing for the C5 and the end result in how the operating system's
adaptive strategy software is expecting to see a certain amount of airmass (grams/sec). The coupler GM uses has two purposes, first is to quiet the sound down and the other allows the engine to move a bit on motor mounts and not break the coupling loose.

The PCM has 512K (1M for 03+) of information, only 80K of it is programable and the remainder is "firmware" or non erasable or programable data. The PCM uses 23 performance PIDS (programable) that can be programmed but the firmware contains the formulas on how they interact. When you add larger imputs for the air intake like bridges and bellows the larger size actually slows down the velocity of the air of the measured surface.

That is why people buy scanning and tuning software to measure the effect the changes they made had on airflow and temperature and make compensations to better utilize the changes. In a stock engine the intake manifold act like a reserve air chamber, since the cylinder can hold only so much air/gas mixture. Adding more air via larger couplers and bridges will do nothing on a stock engine. What make more HP is cooler (more dense) air. Sorry for the long windedness.

 

First, let me just say that if you read some of my past posts, in my book, this is NOT a long-winded post - in fact, info like this is what helps all of us make better decisions.

Now, what you said here is EXACTLY what I've experienced with the larger Halltech airbridge. And, I've said before in other posts that it feels like the engine can't make use of the increased airmass, like it can't "digest" it. I've always felt that the larger volume of air actually seems to reduce the rate at which the air is ingested (velocity factor), thus slightly hinders performance.

It's kind of like if you fill a funnel and let the liquid drip down through it, the liquid does not drain nearly as quickly as if you were to pour a stream of liquid straight down through the funnel drain without allowing the liquid to pool up in the funnel.

A more fun way to look at it is if you fill your mouth with some of a drink, and try to swallow it, it takes longer for that liquid to go down your throat (because your mouth cavity is larger than the opening of your esophagus) than it would if you reduced the amount of liquid you ingest into your mouth. In fact, at less volume, you can swallow even MORE of the drink at a faster rate. That's why in beer drinking contests the people that win are the ones that pour the beer straight down their gullets at a steady rate, compared to the people that try to down the beer in big gulps. But, I wouldn't know anything about that.

With that said, I believe that if you increase the engine's ability to "digest" the larger volume of air, as would be the case if you increase valve lift and/or duration (performance camshaft), thereby increasing the vaccum at the intake manifold, a larger volume of air can be better utilized. I think that at that point the Halltech airbridge would shine, because it only makes sense that LS engine engineers designed the stock airbridge to maximize not only the volume of air traveling through the bridge, but also the RATE (velocity) at which that volume of air travels for a stock engine. And, as pointed out already LS1 and LS6 use the same bridge, which indicates to me that the stocker can still be pretty darned efficient depending upon the significance of the internal engine mod. It's all about balance. This topic is one of the perfect examples of how sometimes more can be LESS!

Let's not even talk about Z06 swaybars on base springs!

 

my stocker broke... split banana style along the mold lines on the side. car was throwing codes and freaking out like crazy with unmetered air coming in. sooo i purchased one that look a lot better too. will you feel or notice 5hp? nope so what im giving up ill just add more elsewhere

 

Let's also not forget the brilliant stock airbox design that increases velocity of air via a pencil-sized opening! Honestly, we should ask ourselves why we so quickly replace the stock airbox with a more open design to increase volume (and thus, airflow) to the engine. The answer is simple - instant HP. I noticed that the Chevy SSR has a direct, cold air intake setup. In fact, the Lexus RX400h has a similar setup. Yet, our C5s do not have a CAI directly from the factory.
The reason I bring up these points is that I want everyone to understand that cost and noise reduction IS a factor (and does compromise HP) in many ways when it comes to power output from our C5s. To believe that any stock component or subassembly represents the best way to achieve HP is misguided thinking, IMO. This is especially more true as our "air pumps" are beefed up.
Another good example is an aftermarket cat-back exhaust like the Borla Stingers. Some people like to point out that the Stingers add little, if any HP, despite their obviously freer-flowing mufflers. Yet, a twin-turbo LS1 gains 50 HP after the installation of the Stingers.

GM had a C5 budget, along with other constraints; always remember that.

 

Exactly.. Some folks think simply, that 100 highly-skilled GM engineers "can't be wrong". It's not that our arm-chair engineering is "superior" to theirs, it's that we have a different set of parameters to work within.

This post kind of shoots a hole through the "Callaway intake is worth 500 bux because it includes a higher following replacement air bridge." theory.