`J` tubes - a quandrey ....

Discussion in 'Mech Tech' started by Lasty, Jan 12, 2014.

  1. Heat exchangers have been on the van for years, and in dire need of replacement .
    I can honestly say they are surplus to requirement as the van is SORN`d October to April so am thinking about sticking on a pair of J tubes rather than shell out £100`s for decent replacements ..
    A search seems to bring up all sorts of comments - an interesting point being the need to block off the exchanger blower ports so more air is diverted around the engine . Seems like a good idea ??

    The thoughts of the TLB massive please - especially folks who have actually gone down this route ..

    Oh - 1600 upright fan...

  2. did think of j tubes for my type 4 but could not see how the bottom half of the engine keeps cool without the under tins .
  3. ^^^ My thinking too - i did come across a feature to suggested fabricating tin deflectors which fill the gap created by removing the exchangers ...

    Any more thoughts ??

  4. You need the heat deflectors from a static engine if your running j jubes otherwise your adding extra heat into the heads
    Lasty likes this.
  5. this is a good mod for j tubes.....get some builders strap tape (bendable metal strip about 2 cm wide...wrap it round the the j tubes to reinstate the tabs that would have been on the heat exchangers....run the normal tin ware...if you want to go the extra mile make some of these...
    keeps the air flowing where it's most needed
    Lasty and paradox like this.
  6. Cheers Vano - that`s what i was trying to get ma heed around ...
    A picture paints a thousand words :thumbsup:

  7. the extra plate is basically doing the job the HX used to do by directing the air over the cylinders and pushrod tubes
    Lasty likes this.
  8. Nice one - any thoughts on reducing the fan holes supplying the heat exchangers , in theory forcing more air over the engine ??
    The thinking behind it all seems to be :-
    Hot weather = heater off = more air to the cooling system.
    Cold weather = heater on = less cooling - not as critical as the air is cooler ..
    Seems reasonable to cap / reduce flow methinks ??


  9. This is another can of worms question.
    Yes blank them off, blanks are available from VWH among others. The can of worms is this:
    Some say if you completely block off the outlet it causes the air in the housing to stall and LESS air goes through the cooling system (my gut feeling is that's not right) so what you need is a hole in each cap that allows enough air through to mimic the back pressure from the heating system. That hole is about 10-12mm IIRC. Perhaps @vanorak would like to comment. :)
    Lasty likes this.
  10. Perhaps I will:D
    From what I've read, the VW techs put a great deal of thought into designing the shroud....I think the heating system will have been designed to have minimal backpressure to maximize flow...Blanking the outlets is definitely going to pressurize the shroud...the fan was designed to operate efficiently within a specific range of pressures....I fail to see how increasing the upper range is going to improve cooling.

    Having said that, plenty of aircooled owners in hotter climes, blank the outlets off, but presumably this is because they don't require the heating system....
    If it were me, I'd retain the ducting and vent to fresh air through the tin....this would more or less mimic the situation when you open the flaps on the HXs in summer
    Lasty likes this.
  11. No brainer really .....

    Gotta go with the stock setup - it works soooo well, even though i never use the heaters :thumbsup:

    Thanks again chaps, input was much appreciated :hattip:

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