Spoon snorkel restrictive?
03-28-2006 | 11:40 PM
#21
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From: NorCal
Originally Posted by i_heart_my_DB8,Mar 28 2006, 11:48 PM
Wait wait wait. I know NOTHING about fluid dynamics, but it sounds like a couple of you guys do.
If I'm interpreting you both correctly, you are saying that the pinch in the snorkel is a non-issue, because the air will simply speed up to pass through there at a higher speed, thus flowing the same volume of air as a less restrictive snorkel, correct?
And by the above reasoning, there is NO detrimental affect to the airflow our engine needs, due to a kink in the snorkel, since the air speeds up to get through there anyway.
Now I'm generalizing and taking this to the extreme, but if this is true, by your logic, as long as air CAN flow through the pinch, it is a non-issue. But what if the pinch gets down to 1mm of space? It seems to me that there would be a point where the restriction would be too much for the engine to pull the same amount of air through there, correct? I'm not saying I know what I'm talking about (I don't), but help me understand.
As far as I've always known, there is an ideal intake diameter and flow for each engine. Ideally, you want as much air to flow through it, as quickly as possible. I've heard an engine compared to you sucking air through a straw. A coffee stirrer (too small) will not allow you to breathe properly. A paper towel roll (too large) will not allow the air to pass through quickly enough. There is an ideal diameter somewhere in between where speed AND volume are maximized, and for some reason... I have an inkling that it is a bigger diameter than that pinch...
It's pretty clear that the pinch is a compromise. Colder air, with the stock hood. But is it ideal? Well, both Mugen and J's sell snorkel intakes that maintain a larger diameter all the way from the induction point to the airbox, and they require a modification to the hood. If the pinch was fine/ideal/non detrimental, why go to the trouble of modifying the hood?
Or correct me if I'm wrong.
If I'm interpreting you both correctly, you are saying that the pinch in the snorkel is a non-issue, because the air will simply speed up to pass through there at a higher speed, thus flowing the same volume of air as a less restrictive snorkel, correct?
And by the above reasoning, there is NO detrimental affect to the airflow our engine needs, due to a kink in the snorkel, since the air speeds up to get through there anyway.
Now I'm generalizing and taking this to the extreme, but if this is true, by your logic, as long as air CAN flow through the pinch, it is a non-issue. But what if the pinch gets down to 1mm of space? It seems to me that there would be a point where the restriction would be too much for the engine to pull the same amount of air through there, correct? I'm not saying I know what I'm talking about (I don't), but help me understand.
As far as I've always known, there is an ideal intake diameter and flow for each engine. Ideally, you want as much air to flow through it, as quickly as possible. I've heard an engine compared to you sucking air through a straw. A coffee stirrer (too small) will not allow you to breathe properly. A paper towel roll (too large) will not allow the air to pass through quickly enough. There is an ideal diameter somewhere in between where speed AND volume are maximized, and for some reason... I have an inkling that it is a bigger diameter than that pinch...
It's pretty clear that the pinch is a compromise. Colder air, with the stock hood. But is it ideal? Well, both Mugen and J's sell snorkel intakes that maintain a larger diameter all the way from the induction point to the airbox, and they require a modification to the hood. If the pinch was fine/ideal/non detrimental, why go to the trouble of modifying the hood?
Or correct me if I'm wrong.
03-29-2006 | 03:59 AM
#22
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From: Gie
Originally Posted by i_heart_my_DB8,Mar 29 2006, 02:48 AM
If I'm interpreting you both correctly, you are saying that the pinch in the snorkel is a non-issue, because the air will simply speed up to pass through there at a higher speed, thus flowing the same volume of air as a less restrictive snorkel, correct?
Now, we have two similar pipe systems with the same delta P, but one has a slightly more restrictive constriction. They will NOT provide the same flow rate. The flow rate will be constant throughout the length of each individual snorkel, but the less restrictive one will have the higher flowrate of the two.
03-29-2006 | 04:12 AM
#23
Joined: Sep 2003
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From: New Jersey
yes what slimjum8201 is saying is correct.
We can use what I said to say the flowrates will be about constant throughout each intake but they will NOT equal each other due to the different designs and restrictions
We can use what I said to say the flowrates will be about constant throughout each intake but they will NOT equal each other due to the different designs and restrictions
03-29-2006 | 08:48 AM
#24
Joined: Nov 2002
Posts: 2,060
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From: Durango, Colorado
I must respectfully disagree with the concept that the "pinch" in the snorkel matters not. Here's a "fluid dynamics" experiement you car try that shows what I mean. Put a ballcock shut off valve on a garden hose, and turn on the spigot full. Observe how mcuh water is flowing (and its pressure) with the ballcock valve in the full on position. Now fill a container with the water, and time how long it took to fill that container. Now, turn the ballcock valve to the "half on, half off" position and fill the same container with the water, and time how long it took. Here, the water pressure from the spigot remains the same. But when a "pinch" is added to the flow by turning the ballcock valve to the "half" position, the rate of water flow is significantly lessened, and it takes longer to fill the given container.
I also respectfully disagree with the statements that seemingly say that a ram air device on an automobile won't work. I will agree that it will not produce any great increase in hp. and/or torque, but it will produce a little. As I recall, the "ram air" option on the mid '90s Trans Ams was good for about 10 hp. And many Grand Prix cars have ram air scoops mounted on them. And the intakes are made as large as possible, and the air paths have no "pinches" for the reasons I mention in the paragraph above.
Thanks,
Richard
I also respectfully disagree with the statements that seemingly say that a ram air device on an automobile won't work. I will agree that it will not produce any great increase in hp. and/or torque, but it will produce a little. As I recall, the "ram air" option on the mid '90s Trans Ams was good for about 10 hp. And many Grand Prix cars have ram air scoops mounted on them. And the intakes are made as large as possible, and the air paths have no "pinches" for the reasons I mention in the paragraph above.
Thanks,
Richard
03-29-2006 | 10:41 AM
#25
Joined: Nov 2003
Posts: 2,246
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From: Atlanta
In the HVAC engineering world that I deal with (I'm an architect), the dimensions of a duct are just as important as the cross sectional area. For example, a duct that is 12x12 will flow much better than a duct that is 24x6. Surfaces that are close together in a duct create turbulence. Turbulence makes for resistance. Resistance is bad for flow.
03-29-2006 | 12:42 PM
#26
Joined: Nov 2002
Posts: 2,060
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From: Durango, Colorado
gagola1:
You are correct, sir, to me experience. That is why I prefer the AUT type CAI to the Spoon, as the entrance area in that critical area over the radiator brace is taller than the opening in the Spoon. Not only a greater cross section, but "not so skinny" and area for the air to pass through.
You are correct, sir, to me experience. That is why I prefer the AUT type CAI to the Spoon, as the entrance area in that critical area over the radiator brace is taller than the opening in the Spoon. Not only a greater cross section, but "not so skinny" and area for the air to pass through.
03-29-2006 | 02:36 PM
#28
Joined: Nov 2002
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From: Durango, Colorado
I think you will find that the "pinch" part of the Spoon has significantly less cross sectional area than the area where the stock horn enters the air box. Further, as glagola1 says above, the "pinch area" of the Spoon may be wide enough, but it is very "short" (top to bottom measurement) so it is not as effective as it would be if it were, say, more square.
Thanks,
Richard
Thanks,
Richard
03-29-2006 | 03:45 PM
#29
Joined: Oct 2002
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From: St-Redempteur,Qc.
Originally Posted by dolebludger,Mar 29 2006, 06:36 PM
I think you will find that the "pinch" part of the Spoon has significantly less cross sectional area than the area where the stock horn enters the air box. Further, as glagola1 says above, the "pinch area" of the Spoon may be wide enough, but it is very "short" (top to bottom measurement) so it is not as effective as it would be if it were, say, more square.
Thanks,
Richard
Thanks,
Richard
03-29-2006 | 03:59 PM
#30
Joined: Nov 2002
Posts: 2,060
Likes: 1
From: Durango, Colorado
And then we are ignoring (or denying) the fact that a properly constructed airscoop/snorkel type CAI actually can put the airbox under greater than atmospheric pressure. The "mechanical force" required to compress air is provided by the car itself, as it travels at a speed greater than the air around it, allowing the rushing air to be "captured" for this purpose. My unit based on an AUT does just that. How do I know? Well my entire intake actually involves a second source of air via a pipe out the pax side of the gutted airbox through the pax side fender well, on which I have a flapper valve installed inside the air box to prevent the escape of "compressed air" from the airbox into this pipe --- when this occurs at relatively low rpms and relatively high speeds (such as in 6th). On an early prototype of this mod, I constructed the flapper valve too small, and out of too light a material. After a spirited run down the freeway, I found the flapper valve had been blown through the 3" pipe and into the fender well by this compression in the airbox.
IMO, it takes a larger "air catching" device than the horn on the spoon to do this, and mine is built much larger. So I criticize the Spoon not only for the "pinch" but also for having too small an "intake horn" to provide ram air.
Thanks,
Richard
IMO, it takes a larger "air catching" device than the horn on the spoon to do this, and mine is built much larger. So I criticize the Spoon not only for the "pinch" but also for having too small an "intake horn" to provide ram air.
Thanks,
Richard