VWDiesel.net The IDI, TDI, and mTDI source.
Engine Specific Info and Questions => IDI Engine => Topic started by: psyte on October 31, 2006, 12:02:05 am
-
ive been wondering lately if a ram air set up would be a good idea on a diesel engine. ive got a 86 VW jetta with a 1.6l N/A diesel. the small tube that goes into the passanger side fender looks like a pretty restrictive way for this engine to be getting its air so i figured mabey if i built a little scoop on the hood and fabricated up a bigger tube that feeds air directly into the front of the filter box it might get me a little more performance and mabey better mpg. does this seem like a good idea to you guys?
-
There is no ram air effect (dynamic head) until over 120 mph at which point you might get nearly 1% with full pressure recovery - Wow!
What is much more importnat is that there is no air cleaner restriction (replace at service intervals) and that the inlet tube doesn't get crushed, or sucked in.
Also there is far more to be gained in hot weather by collecting the air at height, than near the tarmac, as there can be several degrees difference between top of cab and down low. Obviosly don't collect air from behind any radiators or the engine compartment - but ram effect? - forget it.
-
i wasnt talking about getting some serious performance or anything close to a real ram air or turbo. just looking for little ways to improve performance and mpg. dont you think it would at least take a little load off the engine trying to suck the air through the tube when air is also being pushed down it? even if i only get an extra 0.1mpg i think it would be worth it.
-
There is no ram air effect (dynamic head) until over 120 mph
If by dynamic head you mean "The pressure equivalent of the velocity of a fluid", then I would have to disagree. The stock air intake comes off a hole in the right fenderwell, so I doubt that there is air flow from pressure or velocity while the vehicle is moving. Air flow would be due to vacuum created by the piston movement in the engine.
If you drive say 50 mph, turn off your heater fan and check the air flow at your vents. There will be some, possibly enough to keep your car warm. So open up your firewall at the air intake at the base of your windshield, and plumb this into your air cleaner assembly. The area at the base of the windshield is a known high pressure area which is why some racers use this same setup. You now have at least a little extra "free" velocity on the air entering your engine and have done so without creating any extra drag on your vehicle. It won't increase your horsepower by 10% by any means, but it has to help at least a little. The other advantage to this location is that if you run through a puddle you won't soak your filter. Keep the bottom of your ducting above the bottom of the air box or whatever you want to call it so that water can't run into your air cleaner. One potential problem is in areas with snow, where the snow could block this intake or enter the air cleaner assembly, so for winter I would go back to a more stock style air intake setup.
-
I agree that good place for an air intake might well be the stagnation point, and one of them is often around the base of the screen, hence the vents for air conditioning often being found there.
But that is about flowing air, and compared to atmospheric pressure (14.7 psi) which is what forces air into an NA engine, these local pressures around a vehicle are, as I said, insignificant at say 60 mph (about 0.25%) and let's say until 120mph (about 1%) also pretty insignificant.
It is pressure we want and higher density. Velocity, unless very high, is overrated as the figures above show - this is common and well known theory - and a common and well known fallacy...
..until it's enough to make a difference when slowed down and converted to pressure, which requires a diffuser, you are better off if the ground is hot (sunny summer weather) going for density through the odd few degrees difference between surface and a couple of metres up (out of the super-adiabatic layer stuck the the ground).
See the Formula 1 style overhead intakes, scoring on velocity AND density through colder and cleaner airflow. At 180mph maybe 2~3 % might be had, + being 1 metre above the ground and in clean and slightly cooler air is definitely better than lower down, particularly as detonation from high intake air temperatures would be the limiting factor of such beasts :)
Cars in close proximity throw out enormous amounts of heat, and the tell-tale sounds of pinking as a 3-lane summer traffic-jam eases and drivers move off again without waiting for a gap big enough to pull away at sufficient revs, or even dawdle away in 2nd gear, are all too often heard. Most of these cars have pickup low down around the wheel arches (fenders). Oh! for a 4 metre shnorkel intake or a free supply of cool air :wink:
-
the key isn't so much ram air, but cool outside air, and also to make the inlet hose much bigger on the n/a motors, they were made really small to help make the car quieter, not to make more power, that little 2" inlet or w/e is choking you up, get a bigger inlet, and route it to the rain tray or the back to fender well where it was...
-
Would it not be better to put the intake just behind the grill? It'll be pulling cooler air (assuming the fender area pulls from the ground) and would it not also be less restrictive then from pulling inside the fender?
Increasing the size of the piping will defintly help, I'd cut a whole in the air box for even bigger piping
-
What about just fitting a 1 psi electric supercharger for $300 to make more difference than any positioning, or you could say, make the most of any better position... which might well be banman's I think, if it could be put in the exact right spot usually a few inches forward of the base of the screen.
-
I have a 1.6l NA Caddy.
I cut the neck off the standard air intake anout 2" from the air box and ran a 70mm pipe to the front of the grill and used a air intake from Demon-Tweeks screwed to the back of the grill.
The difference is quite noticable, yep a little noisier but the truck ran so much free-er.
A very worthwhile, and cheap mod for more power. I dunno about increase in MPG as, well, Im not that arsed about it!
I also then used a K&N style air filter, which made more difference again.
To me you would be better checking the valve clearances if you have buckets and shims, getting the pump timing and cam timing bang on with a set of fresh filters first, then start messing about with the other stuff.
:)
-
My cold air intake works well on my 1.9D engine:
http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake
(http://www.4crawler.com/Diesel/CheapTricks/Images/ColdAir.jpg)
-
Fresh air! Can't beat it :)
But then don't kid yourself there's any RAM effect, there ain't!
-
My cold air intake works well on my 1.9D engine:
http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake
(http://www.4crawler.com/Diesel/CheapTricks/Images/ColdAir.jpg)
Very similar to mine only I cut the beak more or less off, the end of the beak is quite small bore and quite restrictive I should imagine.
-
Admin/Mods - Why don't the
xxx
s work on this forum???
-
Heck they do then, if done manually!!!
That was a surprise :shock:
Hello this is a quote
heh, hee
Must be the buggering it up
-
Mr Brick Yard...
That looks pretty nice there...
I was wondering if you could describe
what is stock and what is not stock on
your cold air intake........
I do see the 3" abs 90's there..
The black piece that is going over the
valve cover and the air filter housing
is that stock?
Monst 8)
-
Mr Brick Yard...
That looks pretty nice there...
I was wondering if you could describe
what is stock and what is not stock on
your cold air intake........
I do see the 3" abs 90's there..
The black piece that is going over the
valve cover and the air filter housing
is that stock?
Monst 8)
Assuming you are referring to my post/picture. The intake/air filter box is stock, the long tube over the valve cover is stock, then the rest is ABS plumbing fittings, as noted on the web page:
- http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake
I chose a size fitting to just fit over the end of the stock air tube (has a wrap or two of tape on it for a snug fit and a single sheet metal screw to hold it in place.
-
Here is mine i did up on my caddy, Its constructed of 3 inch pvc at the air box, and at the grill I have a 8''-4'' Fernco, and a 4''-3'' Fernco to hook up to the 3 inch PVC.
(http://img.photobucket.com/albums/v622/bryanbryan89x/new%20folder/coldair1.jpg)
(http://img.photobucket.com/albums/v622/bryanbryan89x/new%20folder/coldair.jpg)
-
:D
Wow, that's we we call a soil pipe, night soil :wink:
-
This is what I have screwed to the back of my grille.
http://www.demon-tweeks.co.uk/products/ProductDetail.asp?cls=ROAD&pcode=GLOJC70
On a European Caddy/MKI Golf there is a handy cut out of the grille just to the left of the right hand headlamp, see the image below..
(http://i13.ebayimg.com/04/i/08/c8/ea/f6_12.JPG)
I used one of those ducts, trimmed slightly and screwed into the grille between the lats.
You can't tell from looking unless you look real close then you can see the intake and the tube leading up into the airbox.
I had to trim the grill also and add some more slots below the factory ones but it all looks factory from the outside. I used some flexy tubing from the intake funnel to the airbox.
I would take a picture but the Caddy is scattered around the workshop in a million pieces as it's just in the precess of having a spot of welding/filling/painting![/img]
-
Hi ,
I got two quesetions...
One 4 Mr. Brickyard...
On the stock air box..
what would you say it the dimensions
of that hole.. for air inlet.....
I am almost thinking of maybe
getting a Caddy air box....
Mine is like byranbyran98x....
if the dimesion is sizable... I may go that route....
NEXT QUESTION:
BryanBryan89x Could you explain you
air box mod.. in terms of the plastic
box itself..... It looks real clean and
you have a large inlet on it now....
what did you do to make the inlet bigger....
monst
-
Ah, mine isn't like BrianBrians, er hang on..
mine is like this one..
(http://www.4crawler.com/Diesel/CheapTricks/Images/ColdAir.jpg)
but I cut the beak from the standard airbox almost completely off as it gets bigger bore the closer it gets to the airbox, they used flexy tubing to connect the beak to the funnel.
-
would anyone be interested in pictures of the factory cold air intake on my rabbit? it's missing 2 pieces(the most vital) but otherwise is complete
-
Yeah, that is cool Mr.Brick...
Where that piece kind of flattens..
over the valve cover...and then attaches
to the air box.... it is nolonger a circular tube
it is flattened some, when it attaches to the air box.
(it is oval).... what would you say the dimension
is of the oval opening on the air box.
-
pvc is the go....
i cut my airbox and riveted/siliconed a piece of sheet into the box as an adaptor then made the pvc so its attached to the steel pipe into hte airbox - easy to remove..
(http://images4.pictiger.com/thumbs/36/d9fc6df6786848a3cc487b3d8876fa36.th.jpg) (http://server4.pictiger.com/img/272494//engine-bay-1.php)
click pic for larger view
-
No limit to the imagination here! I suppose a large rubber drain plug could be used as an anti-theft device on that one :)
Wish I could rename this whole thread 'cold-air pickups' though :wink:
-
http://www.eng-tips.com/viewthread.cfm?qid=156700&page=8
Worth a quick browse...
-
Hi ,
I got two quesetions...
One 4 Mr. Brickyard...
On the stock air box..
what would you say it the dimensions
of that hole.. for air inlet.....
I am almost thinking of maybe
getting a Caddy air box....
Mine is like byranbyran98x....
if the dimesion is sizable... I may go that route....
NEXT QUESTION:
BryanBryan89x Could you explain you
air box mod.. in terms of the plastic
box itself..... It looks real clean and
you have a large inlet on it now....
what did you do to make the inlet bigger....
monst
Monst - To make the air box, I used a fiber reinforced polymer, And I took the old air box and made a few mods to it, then I used the old air box as a mold, and kept putting on layers of the polymer (Contact molding). Then I removed it from my mold (old air box) and i cured it in a oven.
I built that set up, because i wanted to see if the cold air intake really made a difference or not, in mpg and performance on the highway. It proved to be a waste of my time, not much of a difference at all
-
It proved to be a waste of my time, not much of a difference at all
You learnt something, you can hardly call that a waste
-
Yeah, first, I like that "use a plug in it for the
purpose of a anti-theft device" that is a great one..
Bryanbryan,
You didn't see any gains at all that were
noticable? And this mold that you made
sounds interesting..... this fiber reinforced
polymer that you mention...... where does
one purhase it.(brand).. Fabrication is always a good
skill... and figuring out that one has options
and can be resourceful......... is a good skill to
have also..... Wasting time.. I can relate........
time is a precious resource.......
How about some resources to "super charging"....
This is definetly in the back of my mind.
-
Yeah, first, I like that "use a plug in it for the
purpose of a anti-theft device"
I'm not so sure that is a good idea. I think you could mess your engine up pretty good. A cheap anti-theft device is simply unhooking your stop solenoid's power source
-
(https://lh4.googleusercontent.com/_l6Ce480D_oM/TH5Z5T1UFVI/AAAAAAAAAOg/xyPnKHOKE0s/s640/IMG_20100827_225712.jpg)
(https://lh5.googleusercontent.com/_l6Ce480D_oM/TMUB3SAGqDI/AAAAAAAAAV8/kHhB_mWZ9aQ/s640/IMG_20101024_191355.jpg)
My setup is working great. No water issues.
-
I too personally saw a huge gain over my stock intake on my 1.6 na.. When I switched to 3" abs to my passenger side highbeam spot.. Above 1500 in any gear there was noticeable improvement.
However I am agreeing that this is not a ram air.. It is a cold air intake. And it does well.
-
if you want ram air, bolt a turbo on, they ram as much air as they can into the cylinder.. lol..
-
The only true ram-air. Turbo-Ramming.
-
find me an actual ram air setup that even comes close to boost??
might make 1 psi? maybe?
-
Not my calculations, found from google search on a forum thread here (http://www.physicsforums.com/showthread.php?t=249971)
Doing the math, assuming no losses:
pressure increase = 1/2 density speed ^2
pressure of air at sea level at 70 F = 14.696 lb / in^2
density of air at sea level at 70 F = .074887 lbmass / ft ^3
1 slug = 32.174 lb sec^2 / ft
1 foot = 12 inches
density of air at sea level at 70 F = .000001346969 slug / in ^3
if speed is feet / sec
pressure increase = 1/2 .000001346969 (slug / in ^3) speed ^2 (ft^2/sec^2)
1 slug = 32.174 lb sec^2 / ft
pressure increase = 1/2 .000001346969 (lb sec^2 / (ft in ^3)) speed ^2 (ft^2/sec^2)
pressure increase = 1/2 .000001346969 (lb / in ^3) speed ^2 (ft)
1 foot = 12 inches
pressure increase = 1/2 .000001346969 12 (lb / in ^2) speed ^2
pressure increase = .00000808181 (lb / in ^2) speed ^2
1 kph = 0.621371192 mph = .9113444 ft / sec
at 100kph, pressure increase = 0.067123 lb / in^2, less than 1/2% increase
To check the math, I compared with an article on ram air:
150mph = 220 ft / sec, and pressure increase = 0.391160 (2.66% increase)
1 psi = 68.948 mb (millibar)
150mph, pressure increase = 26.97 mb
For a speed of 150 mph, the resulting maximum theoretical pressure would be about 27mb (approximately .4 psi).
http://www.sportrider.com/tech/146_9910_ram/index.html
So yeah.. uh.. his math says .07psi at 100km/h and an article from sportrider.com claimed .4psi at 150mph.
I'll assume those are both correct, which seem to go along with what someone earlier in this thread was saying.
Colder air, definitely. Ram air seems to be overrated though
-
Just because imperial units are dumb and overcomplicate everything! ;D
Pressure = n/m^2 = 1/6895 psi
Density = kg/m^3 = 1.204 @ 20deg C @ sea level
Velocity = m/s = 3.6 km/h
For 100km/h
P = ρ/2 * V^2
P = .6020 * V^2
P = .6020 * 27.78^2
P(n/m^2) = 464.6
P(psi) = .06738psi
For 150mph (241.40km/h, 67.056m/s)
P = ρ/2 * V^2
P = .6020 * 67.06^2
P(n/m^2) = 2707
P(psi) = .3926psi
-
i would rather have like 15 psi, rather that 1/15th of a psi.. lol..
TURBO!!
-
just saw this thread popped up again.
Thought I best dig out the pictures....
I loved this truck, it had 250k on the clock and went like Billy-O.
Engine was original, and it revved, oh did it rev!
The air box mod made a big difference.
(http://www.brickwerks.co.uk/images/Simon/forums/GTD/caddyair01.jpg)
(http://www.brickwerks.co.uk/images/Simon/forums/GTD/caddyair02.jpg)
-
Also, one might be wise to observe that the size of the opening, or more accurately the surface area of the opening is directly proportional to the amount of air rammed in. Granted, you're going to have overflow per properties of fluid dynamics, and there will be a point of diminishing returns, however...the size of your "scoop" will dictate how much available air you have to ram into the intake. It will not be anywhere near turbo levels, but say if I were to place a 3ft wide x 3in high x 3in deep air scoop under my front bumper, I'll have significantly more air available, than say a 3in diam hole, and the pressures will be greater at speed. But as previous posters noted, it won't be significant, but by increasing the scoop surface area of the scoop in the prior example (3x3x3), would be significantly more beneficial than a 3" round hole.
-
I'm no fluid dynamasist, however my mechanics logic says that throwing the tiny beak away, chopping it down where it's a larger diameter and connecting a larger diameter hose to somewhere up from the ground and forward facing is going to be a damn site better that the factory snorkel.
I'm not saying that you get "Ram Air", I'm saying that there was a big difference between the standard item and what I did.
:)
-
I'm no fluid dynamasist, however my mechanics logic says that throwing the tiny beak away, chopping it down where it's a larger diameter and connecting a larger diameter hose to somewhere up from the ground and forward facing is going to be a damn site better that the factory snorkel.
I'm not saying that you get "Ram Air", I'm saying that there was a big difference between the standard item and what I did.
:)
Agreed