What about that accordion?

[Paul Workman]

As part of a TB upgrade, I saw where the air horn had been thinned to increase efficiency. It occurred to me later that opening up the air horn could be mooted by the "accordion" tube leading into it.

It raises the question of what (if any) improvement could be had by having a smooth link as opposed to the stock accordion link? Would the accordion type tube negate some/much of the benefit one might be trying to gain by upgrading the TB? In other words, would it be advantageous to installing an aluminum sleeve inside the accordion hose for support (AND air flow) instead of wire support hoops (often used for support)? If so, how much? (I mean when you think about it, so much is done to smooth the air flow when P&P'ing the plenum/IHs, etc, why wouldn't it apply to that intake hose?)

P.

[A26B]

Mark Coplan used to make & sell such an item called the Coplan Air Duct. They are still floating around. A lot of owners use the Samco hose made for the application.

[Locobob]

Paul, I've been toying with the idea of making an internally cleaner airhorn/accordian for quite a few years. A few years ago I got as far as working on a balsa wood test mule but it seems something always comes up and the project gets relegated to the backburner. Might be a little something to gain here - I wouldn't expect a whole lot though.

[LGAFF]

isn't the samco straight in?

[tomtom72]

Originally Posted by LGAFF

isn't the samco straight in?

Yes it is.

I did a hardware store dryer duct insert on my stock accordion duct, smoothed it out nicely. It took some fiddling to get right, but it was the right price.

[Aurora40]

Does smooth = flow? I would think air would flow pretty well through the middle of the accordion tube. Stuff like that Coplon duct is just filling in the accordion center, so I don't see how that would flow better since it's by design smaller.

The Samco is a pain to put on, it doesn't want to fit up right since it has no flex at all. But it may be worth it if you want something smooth.

[A26B]

Originally Posted by Aurora40

Does smooth = flow? I would think air would flow pretty well through the middle of the accordion tube. Stuff like that Coplon duct is just filling in the accordion center, so I don't see how that would flow better since it's by design smaller.

Yes. Surface roughness is part of the equation to calculate flow capacity, along with velocity, etc. Laminar flow would be disturbed by the acordian and create turbulence, which would impede maximum flow capacity. However, if the cross section area is large enough to keep the velocity low, roughness/turbulence is less of a factor.

The Coplan duct's primary function is to prevent collapse of the accordian duct. The Samco duct is more resistant to collapse also.

I don't think air flow through the acordian duct is much of a factor for a 350 cu in displacement motor. I did find through dyno testing that the AO Engineering front plate ducting system cost me about 10 Hp vs nothing in front of the air horn. The stock (94) filter system difference was so minimal that it could have also been heat soak or otherwise.

Summary: IMHO, the only significant fault of the accordian duct is its tendancy to collapse under hot conditions and WOT.

[Locobob]

My thoughts were to start at the throttle body and create a longer air horn piece which features a cleaner, more gradual funnel from the air cleaner assembly into the plenum. Hard part is getting the mounting bolts outside and out of the air stream - that and clearing the A/C and alternator. Like I said I got as far as playing with some balsa wood mock-ups of this idea, hopefully some day I'll get something together for a dyno test to see if there is any merit to the idea.

[Jim Nolan]

The Coplon duct which I have on mine was the fix for the collapsing factory duct. The factory would over time get weak and start failing at w/o throttle.

[Paul Workman]

Looking at the hose, horn, and TB as an individual group, any upgrades to one of the three in attempt to increase air velocity and volume would be subjugated to some extent by the other two...hypothetically.

I think in electronic terms, mostly...

Three resistors in series impede (current) flow.

Reduce the resistance of one and though the current flow increases thru the three, the voltage drop across the other two increases, negating the effect reducing the resistance of one might have had.

Reduce the resistance of two of the three, and current increases, but the voltage drop across the larger one now becomes significant; as though it was the sole impediment to flow and that of the other two becomes negligible (more or less).

Back to mechanics: Substitute "pressure drop" for voltage drop, and "air flow" for current and you have the picture. Reducing the impedance in any one or two of the three and the pressure drop across the remaining "impediment" becomes significantly greater (relative to the initial drop before anything was changed). And that brings (me) back to that remaining impediment of the three...ye ol snorkel hose...

Pickin the fly specs outta the pepper, no doubt. But, if it is worth say $300-400+ to open up the TB and perhaps the horn too to increase laminar flow, then shouldn't there be some attention paid to that nasty ol snorkel tube?

And, don'tcha wish my car was runnin' so I wouldn't be boring y'all with all this trivial chit??

P.