external intake duct

[bandit86]

talked to a guy with a vW eurovan who had a giant 4" pvc pipe hanging out by front right bumper, right through the fender. i asked him, he said it looks stupid as hell (it did) but he had 500,000 kms on the van and he noticed a 3mpg increase after installing it he said he can regularly get 35mpg on the highway if he drove careful.

i had a snorkle on a truck of mine, it did seem to make a difference. anybody try one yet? i know it is like a ram intake but maybe it was in a higher pressure area on the side

[Diesel_Dave]

I've pondered it, but never attempted it. On a turbodiesel I suspect it would help to reduce the pumping losses, although it should be done in a way to minimize the potentially negative aero effects. On a throttled, naturally aspirated engine I suspect that it might not help that much because the increased intake air density will force the throttle to be more closed, so the pumping losses might actually increase.

[oil pan 4]

On a diesel it will work.
I believe in ram air turbodiesel enought to relocate the battery to make room for it.

[Tesla]

Have just started looking at this, starting to check pressures around the body.
I figured ram air should ease the load on the turbo and hence get some economy improvement as long as the setup does not introduce a new drag area, so I am thinking or drawing air from behind the front grille.
One question I was thinking of is that it will pressurize the inlet system slightly pree turbo, but this is also where the PCV dumps blowby gasses in from the crankcase, will this cause more blowby to be retained in the crankcase by pressurising it, is this an issue?

[Diesel_Dave]

Originally Posted by Tesla

Have just started looking at this, starting to check pressures around the body.
I figured ram air should ease the load on the turbo and hence get some economy improvement as long as the setup does not introduce a new drag area, so I am thinking or drawing air from behind the front grille.
One question I was thinking of is that it will pressurize the inlet system slightly pree turbo, but this is also where the PCV dumps blowby gasses in from the crankcase, will this cause more blowby to be retained in the crankcase by pressurising it, is this an issue?

Potentially the crankcase vent should be a small issue. The solution to that is quite simple--disconnect the crankcase vent tube from the compressor inlet. Prior to 2007 I know the 5.9L Dodge Cummins engines were configured that way. I believe many off-highway diesels are still that way.


As far as where to draw ther air from, I think it could be done in such a way as to actually help the aero if done correctly. I'm still looking into the best way to do this. One thought I had was to see if you could do it via cowl induction (pull it in right from the base of the windshield). Seems to me like that would slightly reduce the high pressure region that forms there and perhaps help the aero just a little. That being said, I think the effect would be quite small because the amount of air you draw into the engine vs. the amount of air your flowing past your vehicle would be quite small in most cases.

[Tesla]

The small amount of testing I have done indicates the pressure at the base of windscreen is around the same as that at the front of the vehicle.
As for volume it may be significant, say 4.0l engine = 1l/revolution @ 2,000 rpm = 2,000l, this may have a measurable reduction in the pressure wave.
I can't see a practical way for me to get a duct to the windscreen, that's why I'm going up front. Still need to do some checks and see what sort of vacuum is present post air filter, it may be that under cruise conditions by using ram air it may just get the preturbo pressure up to atmospheric.
The other thing that I am considering is when coasting down it may be beneficial to restrict the ram air so the engine is not just pumping air needlessly and loosing the benefits of a downhill coast.

[Diesel_Dave]

Originally Posted by Tesla

The small amount of testing I have done indicates the pressure at the base of windscreen is around the same as that at the front of the vehicle.
As for volume it may be significant, say 4.0l engine = 1l/revolution @ 2,000 rpm = 2,000l, this may have a measurable reduction in the pressure wave.
I can't see a practical way for me to get a duct to the windscreen, that's why I'm going up front. Still need to do some checks and see what sort of vacuum is present post air filter, it may be that under cruise conditions by using ram air it may just get the preturbo pressure up to atmospheric.
The other thing that I am considering is when coasting down it may be beneficial to restrict the ram air so the engine is not just pumping air needlessly and loosing the benefits of a downhill coast.

Yeah, the front of the vehicle would also be easier, since you don't have to worry about interacting with opening & closing the hood.

[euromodder]

Originally Posted by Tesla

I can't see a practical way for me to get a duct to the windscreen, that's why I'm going up front.

Make sure it won't scoop up water being splashed around when driving through puddles.

[Tesla]

Originally Posted by euromodder

Make sure it won't scoop up water being splashed around when driving through puddles.

Yep, that's been on my mind as well.
It would actually be behind the grille block, I have put an airdam under radiator and infront of tyres, this sits slightly back from the front bar and main grille, it creates a pressure area behind the grille infront of the radiator.
The way the vehicle is currently the front bullbar acts like a splitter, so above the bar, which includes the main grille, is all blocked and am streamlining that to flow air over and to the sides.
Below the bar is open up to the airdam, which is set at about axle height, this then reduces air going under the vehicle, but also creates a pressure area behind the blocked grille above it.
This is where I intend to draw the intake air from, I will also include a water trap/drain in the ducting in case of a major splash, then also need to provide an alternative/temporary raised intake for water crossings.
There are a number of compromises I am working with, I do want to maximise my fuel economy, but still want the vehicle relatively capable off road, so approach/rampover/departure angles are important as well as other offroad ideals.

[oil pan 4]

I had my ram air when I drove from virginia to newmexico and drove throught the longest and worst rain of my life.
My ram air was behind the factory grill and went up hill 5 inches.
As long as you can run the intake pipe up hill you will be good to go.