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#15 by Gizmoman on 24 Apr, 2014 05:18
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A quick test using the factory air box and a sensitive vacuum gauge in the intake tract might answer your question. As long as you're seeing less than 15" water column you should be fine.
OK - got it
"First, the term Absolute Pressure means the pressure above a zero reference (a perfect vacuum). Ambient atmospheric pressure at sea level on a "standard day" is approximately 14.696 psi absolute (or 29.92 inches of mercury, "HG, explained below).
Manifold Absolute Pressure, then, is just what it says: The absolute pressure which exists in the inlet manifold, usually measured in the plenum (if one exists). The MAP in an engine which is not running is equal to atmospheric pressure. If, on a "standard day", an engine is idling at a measured manifold "vacuum" of 14 inches,, the MAP is actually 15.92 "HG (29.92 - 14 = 15.92)."
Quoted from here http://www.epi-eng.com/piston_engine_technology/volumetric_efficiency.htm - bottom of page.
I also found this handy calculator and plugged in a few numbers. This calculator was developed for the Mitsubishi 3000GT VR4 and Dodge Stealth TT turbocharged cars. "Overall density ratios are usually less than 2.5 (that is boost pressure is less than 24 psi)."
The calculator is found here http://www.stealth316.com/2-air-fuel-flow.htm -
#16 by RabbitJockey on 24 Apr, 2014 05:30
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15" of water sounds like a lot, and that is half a psi, im not sure what would be an appropriate amount tho.
my only suggestion would be to try the stock air box from a vehicle that has at least 200hp stock, which shouldn't be hard to find by browsing through a junkyard -
#17 by Gizmoman on 24 Apr, 2014 05:41
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15" of water sounds like a lot, and that is half a psi, im not sure what would be an appropriate amount tho.
Yeah, I though of doing that. I've been looking at various boxes online but they don't offer dimensions. The good part though is they are generally designed to be quiet.
my only suggestion would be to try the stock air box from a vehicle that has at least 200hp stock, which shouldn't be hard to find by browsing through a junkyard
Browsing through a junkyard with a tape measure and a few simple tools would be a smarter way to approach this.
I've been driving the van to work every day this week (several semi-steep grades at 65-70). The round trip is about 45 miles. Other than the low drone from the intake - this engine really goes! -
#18 by 410 on 24 Apr, 2014 06:14
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15" of water column is about 1" hg so it's pretty minimal. Although it's the max amount of "vacuum" you want to see in your intake tract. As a reference it would be a worth while test to do on your current system. Sometimes air filter box's are built to flow way more air than the factory rated airflow through an engine. The MK4 is a perfect example. The stock air box on an MK4 can flow a ridiculous amount of air to the point that only the highest hp builds run custom systems. It's virtually the same air box on a 90 hp ALH and a 280 hp VR6.
If you end up at a junk yard, see if you can find a filter minder off a diesel truck. A lot of the GM gas trucks and SUVS have them too. It can help you get the most out of your air intake system. -
#19 by GEE-BEE on 24 Apr, 2014 18:06
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I like the hoses....
GB -
#20 by Gizmoman on 24 Apr, 2014 18:40
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I like the hoses....
Yeah GB, everyone who looks at the engine likes em as well
GB
. I tell em they're wrapped with 20 dollar bills and painted blue
Thanks for the input fellas. I removed the can today and wrapped it in rattle trap. Then I got a 4" diameter bit of expanding aluminum dryer duct and formed it over the intake of the can and up the rear pillar. I but a few bends in it and its a very rough surface. I'll report tomorrow if the ride to work is a bit quieter. -
#21 by GEE-BEE on 24 Apr, 2014 19:34
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I can make a custom silicone flex duct with cuffs on each end 1' thru 5' i.d.
I make these for aircraft heating and cooling systems
send me a email for a pic you may load, helping you helps others
GB -
#22 by carrizog60 on 25 Apr, 2014 02:06
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i wasnt refering to stock vanagon airbox,my mistake.
was talking the golf ones.
seen many people running tdi engines on mk2 shells with above 200hp using OEM airboxes(to avoid problem with police),i am running a vnt2052 at 1.5bar with passat airbox(just removed the snorkel as it was smaller diameter) and -not as a good example because its a gas engine- i run stock airbox with my golf g60 and i am hitting above 180hp.
stock golf limited was 210hp from factory and used same box.(equal to late TD ones,just different locations on exit holes).
how can we check if airbox is becoming a problem? -
#23 by Gizmoman on 25 Apr, 2014 04:48
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i wasnt refering to stock vanagon airbox,my mistake.
was talking the golf ones.
seen many people running tdi engines on mk2 shells with above 200hp using OEM airboxes(to avoid problem with police),i am running a vnt2052 at 1.5bar with passat airbox(just removed the snorkel as it was smaller diameter) and -not as a good example because its a gas engine- i run stock airbox with my golf g60 and i am hitting above 180hp.
stock golf limited was 210hp from factory and used same box.(equal to late TD ones,just different locations on exit holes).
how can we check if airbox is becoming a problem?
Agreed, there are probably plenty of air boxes I could use that wouldn't hurt the airflow and if what I did to mine didn't do much (very likely), it's time to go browsing. -
#24 by Mark(The Miser)UK on 25 Apr, 2014 17:29
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i see high HP buils using stock airbox(the larger,square one), why do you think it may not flow enough?
Interesting thought, maybe I should have kept the 1.6 exhaust as well
Kidding aside, typically automotive engineers who design stuff like this don't design them for three times the capacity required - just a guess though.
I ran a quick calc (keep in mind, I am math challenged) and came up with 322 CFM for my engine at 3200 RPM @20 psi. In comparison, the 1.6 NA runs about 90.4 CFM@ 3200.
Granted the numbers are rough, but that's nearly a 256% increase in air volume over the stock engine.
A stock 2.1 gasser vanagon intake box (as you suggested) would be designed to flow approximately 119 CFM @ 3200 - still 170% less than required for my engine.
If anyone want's to take a stab how many CFM's I may be running at 20 PSI/3200 RPM, that would be very interesting. Turbo is an HE200, medium head porting and short 2-1/2" exhaust.
I might be wrong, but have you overestimated the extra air gained by 20 psi?
If n/a air is at 14.7psi, and true pressure is atmos + reading, ie 34.7psi, I make that 90.4 x 34.7/14.7, or 213cfm... -
#25 by Gizmoman on 25 Apr, 2014 18:15
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i see high HP buils using stock airbox(the larger,square one), why do you think it may not flow enough?
Interesting thought, maybe I should have kept the 1.6 exhaust as well
Kidding aside, typically automotive engineers who design stuff like this don't design them for three times the capacity required - just a guess though.
I ran a quick calc (keep in mind, I am math challenged) and came up with 322 CFM for my engine at 3200 RPM @20 psi. In comparison, the 1.6 NA runs about 90.4 CFM@ 3200.
Granted the numbers are rough, but that's nearly a 256% increase in air volume over the stock engine.
A stock 2.1 gasser vanagon intake box (as you suggested) would be designed to flow approximately 119 CFM @ 3200 - still 170% less than required for my engine.
If anyone want's to take a stab how many CFM's I may be running at 20 PSI/3200 RPM, that would be very interesting. Turbo is an HE200, medium head porting and short 2-1/2" exhaust.
I might be wrong, but have you overestimated the extra air gained by 20 psi?
If n/a air is at 14.7psi, and true pressure is atmos + reading, ie 34.7psi, I make that 90.4 x 34.7/14.7, or 213cfm...
Am I wrong? extremely good chance of that -
#26 by Gizmoman on 25 Apr, 2014 20:40
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What I did, with the 4" wrinkly drier duct and rattle trap on the can seems to have brought things under control.
Now all I can hear is the cabinet doors rattling
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#27 by 745 turbogreasel on 26 Apr, 2014 00:33
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If you get the total tube length exactly wrong, not only is it loud, it's also self amplifying.
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#28 by burn_your_money on 26 Apr, 2014 07:00
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What I did, with the 4" wrinkly drier duct and rattle trap on the can seems to have brought things under control.
Now all I can hear is the cabinet doors rattling
I'd be interested in some pictures next time you have it out
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#29 by Gizmoman on 26 Apr, 2014 10:18
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Ha - Im big on taking lots of pics while I work, except for this time - go figure.
When I fabbed the can up, I just got lucky when I made the intake which ended up having the same perimeter measurements as the ID of 4" flex duct (12.57"). I used the 4" aluminum drier ducting from Home Depot (found in the ducting isle). Mashed it into an oval and bent it to look like a flattened 2' long candy cane.
I formed one end to fit onto the intake and stuffed it up the pillar. You can see the top end of the candy cane if you look down into the pillar through the vent.
Then I installed the back half of the can. It was tough but after I got the can in and worked the formed the flex-duct end onto the intake (which is pointing straight up), I used that aluminum ducting tape (not the fabric duct tape) to hold in in place. I also added some tape to the inside where the flex slips over the intake just to make sure it never comes off.
Heres a shot of the intake - it's ponting like this when mounted and aligned to shoot straight over and up to the vertical pillar - in other words, a slight jog is required in the flex before it goes vertical.
As suggested, the sound has to smack against the first bend at the top (the "J" of the candy cane shape), hit all the "ruffles of the ducting, hit the jog in the bottom, then finally enter the can.
Sorry, but chances of ever taking it out are slim. Hopefully my explanation combined with your imagination, you can visualize the outcome.
I wish I had Db readings from before and after (have an app on my phone) but I don't have that either