underbonnet ventilation---cooling fans (280i)
Discussion
hi. i changed my viscous fan to a two-speed electric fan, switched by an adjustable thermostat. thermostat is located in the upper radiator hose. the setpount on the scale of the thermostat is set on ~70degrees
the fan is located behind the radiator (sucking) directly mounted(no gap) on the radiator.
when it runs you can definately feel the air being sucked from the front of the radiator, through the radiator and the radioator surface is cold....but interstingwise the engine temperature is higher than with the viscous-fan. (beofre it was 190-200 fahrenheit, now its 200 to 210)
the airflow of the electirc fan is definately a multiple of the viscous-fan (from what i can feel) but efficiney seams to be poor.
now i recognized that there isnt any airflow under the bonnet possible. the fan sucks the air from front and blows it inside the enginebay where it cannot escape.
with a closed bonnet the fan on a hot machine runs nearly permanent, opening the bonnet and it will stop soon.
any possibility to increase the underbonnet airflow?
the fan is located behind the radiator (sucking) directly mounted(no gap) on the radiator.
when it runs you can definately feel the air being sucked from the front of the radiator, through the radiator and the radioator surface is cold....but interstingwise the engine temperature is higher than with the viscous-fan. (beofre it was 190-200 fahrenheit, now its 200 to 210)
the airflow of the electirc fan is definately a multiple of the viscous-fan (from what i can feel) but efficiney seams to be poor.
now i recognized that there isnt any airflow under the bonnet possible. the fan sucks the air from front and blows it inside the enginebay where it cannot escape.
with a closed bonnet the fan on a hot machine runs nearly permanent, opening the bonnet and it will stop soon.
any possibility to increase the underbonnet airflow?
Various people have suggested lifting the back of the bonnet a little to us, i.e space out the catch and add a bit more rubber to the corners. It does seem to have helped on the 400 a bit.
I have also seen holes drilled in the rear lip of the bonnet though I guess you might not want to perform surgery on your wedge, I might have a picture of this somewhere.
I have also seen holes drilled in the rear lip of the bonnet though I guess you might not want to perform surgery on your wedge, I might have a picture of this somewhere.
the viscous didnt had a shrout or surrounding.
the new electric one has a surrounding and fits without gap on the radiator.
when the electric-one is running (engine hot) you can touch the front side of radiator core: ice-cold.
or maybe i´m too sensible and the temperature between 200 and 210 fahrenheit is normal?
the new electric one has a surrounding and fits without gap on the radiator.
when the electric-one is running (engine hot) you can touch the front side of radiator core: ice-cold.
or maybe i´m too sensible and the temperature between 200 and 210 fahrenheit is normal?
I've just changed mine from viscous to electric. The viscous one went solid and stopped being viscous Then the gauge showed a good drop which the electric one can't manage if left on.
Mine used to indicate about 200-210F when in town and seemed ok. I now just turn on the override if approaching town traffic and the gauge now settles at just over 200F. That assumes the gauge is correct.
Mine used to indicate about 200-210F when in town and seemed ok. I now just turn on the override if approaching town traffic and the gauge now settles at just over 200F. That assumes the gauge is correct.
It's because with the viscous fan it would be running all the time, whereas the electric one only runs over the thermostat set point.
When you are moving, plenty of air gets pulled out of the engine bay under the car, it's not a closed box. The trouble comes when you stop, and heat tends to gather at the top of the engine bay. However it will eventually spill out underneath. (This assumes you haven't installed an undertray on your car!!!)
I think 210F is OK (why not centigrade though!??!), is 220 boiling? That would put 230-240 about 110, which is just about the upper limit when stationery.
When you are moving, plenty of air gets pulled out of the engine bay under the car, it's not a closed box. The trouble comes when you stop, and heat tends to gather at the top of the engine bay. However it will eventually spill out underneath. (This assumes you haven't installed an undertray on your car!!!)
I think 210F is OK (why not centigrade though!??!), is 220 boiling? That would put 230-240 about 110, which is just about the upper limit when stationery.
i had also a damaged viscous (running permanent). temperature was around 190 to 200 fahrenheit. than i changed the damaged viscous to a new one and the temperature increased to 200, stable.
by the way: TVR never fitted a shroud around the viscous ones.
than i removed the viscous (loosing 3 bolts which hold it on the pulley, took visocus of and fixed pulley again) and changed to a electric one.
the electric one is running nearly permanent and doesnt get the temperature under 200 fahrenheit. so even an override switch wouldnt help. opening the bonnet helps a bit.
why do we discuss in fahrenheit? cause my SW gauges show me fahrenheit and not celsius.
by the way: TVR never fitted a shroud around the viscous ones.
than i removed the viscous (loosing 3 bolts which hold it on the pulley, took visocus of and fixed pulley again) and changed to a electric one.
the electric one is running nearly permanent and doesnt get the temperature under 200 fahrenheit. so even an override switch wouldnt help. opening the bonnet helps a bit.
why do we discuss in fahrenheit? cause my SW gauges show me fahrenheit and not celsius.
Micha, think that your setting of 70 degrees is much too low. Would expect something like 87-90 degrees!
This is not helping on your problem, as it will continue to exist.
Are you sure you have no air trapped somewhere in the system?
Did you change by any change the thermostat, and is it the 'correct' one (and correctly installed, as there should be a small hole and to be positioned at the top).
Did the overall cooling fluid capacity go down?.....
Rob
This is not helping on your problem, as it will continue to exist.
Are you sure you have no air trapped somewhere in the system?
Did you change by any change the thermostat, and is it the 'correct' one (and correctly installed, as there should be a small hole and to be positioned at the top).
Did the overall cooling fluid capacity go down?.....
Rob
never touched the thermostat, cooling fluid is stable and no leaks.
my intense was to reach around 85-90(max) degrees by changing from viscous to e-fan.
but the things changed vice-versa.
again: the viscous fan (without surrounding) seams to be more efficient than the e-fan.
and i didnt touch any other parts in the meanwhile.
www.convert-me.com/en/convert/temperature
210 fahrenheit = 98.89 degrees celsius
200 fahrenheit = 93.33 degrees celsius
the gauge shows around 200 fahrenheit.
i´m owning another tasmin with smiths instuments (in celsius). i dont use this car much, as its only for collection. this car is also in original configuration (viscous fan, no surrounding). i tested it during weekend, too. the instrument shows around 93 degrees during running.
so same "problem"...so it seams "normal"....but dont forget: outside temperature was on weekend around 26 degrees...so far away from a hot summer with 35degrees or more here.
conclusion:
viscous versa e-fan: no improvement for cooling, only a little gain of engine power. (which cannot really be felt during driving).
contacted my garage today: "if you want to bring your temperature down throw away this old brass radiator and take a modern aluminium one...and the best would be to put it in the nose-cone instead of the enginebay"
ok...thats maybe a solution...alu-radiator ok...but changing into nosecone looks like a big job?
my intense was to reach around 85-90(max) degrees by changing from viscous to e-fan.
but the things changed vice-versa.
again: the viscous fan (without surrounding) seams to be more efficient than the e-fan.
and i didnt touch any other parts in the meanwhile.
www.convert-me.com/en/convert/temperature
210 fahrenheit = 98.89 degrees celsius
200 fahrenheit = 93.33 degrees celsius
the gauge shows around 200 fahrenheit.
i´m owning another tasmin with smiths instuments (in celsius). i dont use this car much, as its only for collection. this car is also in original configuration (viscous fan, no surrounding). i tested it during weekend, too. the instrument shows around 93 degrees during running.
so same "problem"...so it seams "normal"....but dont forget: outside temperature was on weekend around 26 degrees...so far away from a hot summer with 35degrees or more here.
conclusion:
viscous versa e-fan: no improvement for cooling, only a little gain of engine power. (which cannot really be felt during driving).
contacted my garage today: "if you want to bring your temperature down throw away this old brass radiator and take a modern aluminium one...and the best would be to put it in the nose-cone instead of the enginebay"
ok...thats maybe a solution...alu-radiator ok...but changing into nosecone looks like a big job?
If the electric fan is hard up against the face of the radiator with no gap then you are only using the proportion of the radiator that is swept by the fan. An unshrouded fan spaced away from the radiator is going to recirculate the end around the engine bay which will reduce the flow through the radiator, this loses a small amount of cooling, on the other hand it will be pulling air through from more of the radiator are which increases cooling a lot, equally importantly it is probably several times more powerful than the electrical fan.
Nett result is you may well have reduced the total cooling capacity. If you can space the fan back from the radiator by about an inch and shroud it so it draws air in from the whole surface of the radiator you will find you get far more cooling from the radiator.
Also do everything you can do discourage hot air from the back of the radiator from nipping back round to the front. Stick your hand in front of the rad and feel how warm the air is - your hand is remarkably sensitive to small temperature rises in this temperature range and a very good way to test for air recirculation.
Nett result is you may well have reduced the total cooling capacity. If you can space the fan back from the radiator by about an inch and shroud it so it draws air in from the whole surface of the radiator you will find you get far more cooling from the radiator.
Also do everything you can do discourage hot air from the back of the radiator from nipping back round to the front. Stick your hand in front of the rad and feel how warm the air is - your hand is remarkably sensitive to small temperature rises in this temperature range and a very good way to test for air recirculation.
micha said:
hi. yeah i remember this holes on bonnet-lip, too. would be great to see the picture again.
but what i still not understand: why the viscous fan has more efficency than the better-sucking electric one?
strange.........
but what i still not understand: why the viscous fan has more efficency than the better-sucking electric one?
strange.........
Because it's blowing air directly at the source of the heat and the area of the engine where the temperature is being measured. If the temperature is a problem go back to the viscous fan
My viscous fan went south, I replaced it with an electric one. I tried two thermostats neither seemed to work very well.
I got a new viscous fan and the operating temp is now around 85 C and very steady, I can leave it idling in Summer temps of 90 + F without worrying.
In fact I seldom even look at the guage anymore !
PS A viscous fan is not running all the time it only "locks in" when it gets hot, it is "freewheeling" most of the time.
I got a new viscous fan and the operating temp is now around 85 C and very steady, I can leave it idling in Summer temps of 90 + F without worrying.
In fact I seldom even look at the guage anymore !
PS A viscous fan is not running all the time it only "locks in" when it gets hot, it is "freewheeling" most of the time.
i know that the viscous isnt running permanent, but a viscous costs some engine horsepower. thats the main reason people change it. thats the reason why i changed it, too...and i can feel it during driving.
i guess my radiator is blocked. so i will try to get a 2nd hand one and recore it.
so now the the next problem: the TVR handbook says the radiator is from a ford capri 3l. but all capri radiators i´ve seen have the top-water-inlet on the left instead the right.
i guess my radiator is blocked. so i will try to get a 2nd hand one and recore it.
so now the the next problem: the TVR handbook says the radiator is from a ford capri 3l. but all capri radiators i´ve seen have the top-water-inlet on the left instead the right.
thomas7037 said:
What do people think to using exhaust insulation to try and keep under bonnet temps down? Am going to give it a go.
This one's been done to death already. I'll summarise but for more detail do a search... The wrap absorbs moisture when cold and this combined with the elevated exhaust temperatures promotes a rate of corrosion any early 80's Alfa would be proud of
Even if the exhaust is stainless it's not good news as the extreme temperatures can cause cracking. Best solution is ceramic coating inside and out which is ex£en$ive to say the least! My early Tasmin 2.8i had a p**sy little 10" electic fan with just a switch when I got it. I made a bracket and fitted one from a cavalier which is spaced about 1/2" behind the rad and just to one side. The only time I need to switch on the fan is in traffic and it drops the temp by 10degs to 190F.
Kev
Kev
exhaust insulation has some major (negative) side effects, i think:
your manifold stays warmer, automatically the outlet-valves do not get as cool as they could and so could damage earlier.
also i guess on the ford v6 the manifolds are located very low inside enginebay and will not effect the enginebay´s temperature so much compared to other cars.
your manifold stays warmer, automatically the outlet-valves do not get as cool as they could and so could damage earlier.
also i guess on the ford v6 the manifolds are located very low inside enginebay and will not effect the enginebay´s temperature so much compared to other cars.
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