On the question of fans, Rick, do you have the "warm air blower" (squirrel fan?) shown with arrow on image. When that's turned on the air pressure closes the bottom non return flaps item 32(where you attached the J pipes to the fan housing) and deals with the heating and allows the main fan to concentrate on cooling the engine. That's assuming you have the non return flaps?
DD, yes i have 2 fans in my shed (not fitted havent got pipes to the risers so they are blocked off to stop hot air getting in cool zone) the flaps on fan end are missing they (i thought) aren't critical as surely with engine running the air forces them open, i just assumed the flaps shut when you turn off and stop hot air bleeding back into the engine via the fan?
are you saying then that in theory the squirrel fan runs permanent if heat is on and thus the flaps shut and cool the engine totally with the pulley fan just like when they were blocked when i had j tubes? if so how? as it looks like they have no way of being held shut.
Fan only runs when control levers are fully down unless you have a speed switch but these arent common. The heater fan that is as obviosly the main fan runs all the time as its on the end of the crank!
Yep think you are right Ricky, and I also think the squirrel fan only really has an effect at idle speed
yes, it's true that the squirrel fan keeps the heating going at tick over but it's a balance, between the two fans. The squirrel fan is pretty good too and the main fan only gets to pump air down two little channels bu t does a great job at higher revs. This is from Atwell's web: "Because there are two sources of airflow there are 4 flaps in the system to direct air. Two are located in the booster fan and keep air from the impeller fan, which has now been warmed by the heat exchangers from entering the engine compartment. When you turn on the fan while driving the flaps open a little because the booster fan has a powerful motor. Chances are you still have these flaps because they are hard to notice (the PO can't toss what he can't see!). If your flaps are missing then you'll have engine overheating issues just as if you had removed the hoses and left the heat riser tubes open. The other two flaps are in the base of the fan shroud and prevent air from the booster fan from re-entering the engine compartment. Often if there has been exhaust modifications the flaps have been lost or left out. Sometimes they have unknowingly fallen off while driving. They are held in place by a simple pin so if you ever have someone work on your engine be around when they are about to put the fan shroud back on. You will notice (or never have known that you lack) a serious lack of heat if you are missing these flaps." I tend to think that VW knew what they were doing, but they did build 'em to last so we get away with murder.
agree DD so as long as i fit squirrel with flaps (i know i have those) that's the important part, at the moment i have the risers from the exchangers fitted and in the engine bay but capped off so in effect they are doing the same job as if the squirrel was fitted but not running, this still proves my point that the engine pulley fan in normal running with flaps fitted will push them open as they are only held in place by gravity, therefore they must stop heat bleed back only when the engine isn't running?
reading ratwell it seems that if i dont have main pulley flaps it's best not to fit the squirrel fan.
