No not that old chestnut
While reassembling the tin work after some work on the van engine bay I pondered about the design intent regarding the vents behind the rear windows/panels.
Having it in mind that the air box on my WBX is ducted into the right hand side I deduced that that would be a good place from which to ingest fairly clean air.
Then tinkering around in my admittedly somewhat addled mind with our old friend the Bernoulli effect I decided it was not as simple as that.
The Bernoulli effect helps hydroplanes fly, your hat to get sucked out of your side window and old gentlemen to have wet trouser fronts to name a few examples.
It seems obvious that air is drawn in through those vents if you take it on face value but....
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
Both the voids infront of the tail light clusters on my my van are pretty much blocked , on one side I have a 12l kero tank for my heating and on the other side is my engine battery , so no real air flow occurs from those vents
My air intake stops just after the filter box , I have no need for a snorkel as I can’t go that deep in water anyway as the underfloor domestic water tank breathers are lower than the air intake .
There have been various, at times heated, arguments about the air flow through these vents on thesamba. From what I could gather:
- it was dependent on engine, tinware and bashplate configuration as different types were more likely to scoop up more air from below the vehicle than other types. This in turn would effect the pressurisation of the engine bay, which in turn would effect how likely air flow through the vents was in a particular direction.
- it was dependent on speed - the vents were more likely to be intakes at low speed and exhaust at higher speeds, but again depending on the above factors.
Basically there was no categoric conclusion that would lead anyone to conclude that you could rely on the side vents performing in a specific way.
1988 LHD T25 1.6TD Westfalia Club Joker Hightop syncro
To be honest I had in mind the fact that at a standstill they would make excellent chimneys acting to draw on the flames taking fresh air from under the engine while at speed and bearing in mind the ground effect slowing the airflow under the van, could actually suck air in the reverse direction with quite different outcomes.
One would imagination particularly in the current "lets have it all out in the open" ethos that somewhere deep in the VW covert info files that there will be records of tests the results of which were deemed best not promulgate.
Unless of course they are stuffed with all sorts of ancillary equipment etc.
Well-timed silence hath more eloquence than speech.
"A quiet shy boy who took little part in games or sport"
88 High top 2.1 WBX
itchyfeet wrote:What is needed is a real experiment and not urban myth.
attach some short ribbons to the vents and watch as you drive in your rear view mirror.
Like I said, there are plenty of arguments and data on this topic on samba. For example these two threads:
There are others as well, but these are the two that spring to mind, so there's plenty of dangly thread action on video to be found, lots of overly prescriptive pressure gauge readings, and accusations aplenty of urban myth and magic thinking. Funny thing is that the people who are look to be most agitated seem to be the ones who've spent money on adding accessory scoops. Go figure...
1988 LHD T25 1.6TD Westfalia Club Joker Hightop syncro
I'm going to stick my neck out without reading the Samba threads...
I'm fairly certain that the vents were a good source of cooling air for the Aircooled T25's. That may have changed when the WBX was dropped in, open engine bay, no longer sealed, changes the air pressure below the van, and not least the absence of the nice large cooling fan.
I realise the above may not have been a wholly helpful response
1981 RHD 2.0 Aircooled Leisuredrive project, CU engine
1990 RHD 1.9 Auto Sleeper with DF/DG engine
I stopped reading all the "in theory" posts on the samba some time ago. The 'mercuns are very reluctant to ask anyone not stood on their continent what they may know, so expound at length with endless conjecture and untested notions.
PS the "snorkel" isnt provided for wading, its actually a silencer for reducing intake air noise and preventing the engine drinking rainwater, whether static or while in motion (thats why the air inlet holes face backwards)
