Ram air on a diesel?

[psyte]

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?

[HarryMann]

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.

[psyte]

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.

[clbanman]

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.

[HarryMann]

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:

[RabbitJockey]

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...

[burn_your_money]

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

[HarryMann]

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.

[Baxter]

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.
 

[VWCaddy]

My cold air intake works well on my 1.9D engine:
http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake

[HarryMann]

Fresh air! Can't beat it  

But then don't kid yourself there's any RAM effect, there ain't!

[Baxter]

My cold air intake works well on my 1.9D engine:
http://www.4crawler.com/Diesel/CheapTricks/index.shtml#ColdAirIntake

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.

[HarryMann]

Admin/Mods - Why don't the

xxx

s work on this forum???

[HarryMann]

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

[monst]

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