Discussion
Perhaps a simple solution could be to take a small pipe off the bottom hose of the radiator to a small electric waterpump, and run it back into the system using a T piece with the outlet of the heater matrix hose.. (effectively bypassing the waterpump).
This could be wired in with the Fan Circuit, so when the fans are on with the engine running this pump runs as well as the waterpump, and when the engione is not running, it will still circulate the coolant when the fans are on.
Just a thought.
Cheers
Matt.
This could be wired in with the Fan Circuit, so when the fans are on with the engine running this pump runs as well as the waterpump, and when the engione is not running, it will still circulate the coolant when the fans are on.
Just a thought.
Cheers
Matt.
I've got Davids (Mod Wise) excellent 2 stage fan kit fitted and wired off the 'mains'.
When I turn off the ignition, the fan keeps going until the coolant temp falls back to a predefined temp (at least I think thats the way it works.....)
It stops heat soak ( and I haven't had a flat battery even in the silly temps we had last year) and can only do good as far as my limited brain can see.
When I turn off the ignition, the fan keeps going until the coolant temp falls back to a predefined temp (at least I think thats the way it works.....)
It stops heat soak ( and I haven't had a flat battery even in the silly temps we had last year) and can only do good as far as my limited brain can see.
N17 TVR said:
I've got Davids (Mod Wise) excellent 2 stage fan kit fitted and wired off the 'mains'.
When I turn off the ignition, the fan keeps going until the coolant temp falls back to a predefined temp (at least I think thats the way it works.....)
It stops heat soak ( and I haven't had a flat battery even in the silly temps we had last year) and can only do good as far as my limited brain can see.
Sadly it doesnt help with coolant circualtion though when the engines not running.. so whilst excellent when on the go, it doens't change the problem here of localised heat within the engine block...
Matt
Edited to add.. do you know who L17TVR is btw.. I see him occaisionally around my way..
>> Edited by M@H on Wednesday 26th November 11:05
Leaving the fan on with the engine not running does virtually nothing to help with the engine temperature as there is no water circulating. All it does is cool the radiator and its content until its temperature is reduced to turn the fan off.
Leaving the engine idling until the fans go off also does virtually nothing as this may take a long time or not happen at all becuase idling is a very stressful time. This is why traffic jams are not much fun for any car. The engine temp may drop a few degrees but switching the engine off will reduce the heating and thus cool the engine far quicker.
When the fans switch off the water temperature is still very hot. The engine is still very hot and the exhaust is extremely hot. So switching off when the fans go off is not going to do much for these conditions either. The arguments about localised boiling etc are still there.
The only real way that leaving the fans on afterwards is with the engine switched off to prevent the engine from continuing to generate heat and with a secondary electric pump to circulate the water. Is it worth it? It might be for competition cars where there is a need to get the car cool but for everyday use, I can't see the point to be honest.
Leaving the engine idling until the fans go off also does virtually nothing as this may take a long time or not happen at all becuase idling is a very stressful time. This is why traffic jams are not much fun for any car. The engine temp may drop a few degrees but switching the engine off will reduce the heating and thus cool the engine far quicker.
When the fans switch off the water temperature is still very hot. The engine is still very hot and the exhaust is extremely hot. So switching off when the fans go off is not going to do much for these conditions either. The arguments about localised boiling etc are still there.
The only real way that leaving the fans on afterwards is with the engine switched off to prevent the engine from continuing to generate heat and with a secondary electric pump to circulate the water. Is it worth it? It might be for competition cars where there is a need to get the car cool but for everyday use, I can't see the point to be honest.
Incorrigible said:
wolosp said:
That's why when I fitted my two-stage fan kit, I declined to opt for wiring it so the fans stayed on....couldn't quite see the point if the coolant wasn't circulating through the rad.
So did you fit an electric water pump too then
Nope, there's enough problems with batteries draining without adding to them!
>> Edited by wolosp on Wednesday 26th November 11:27
Hi Guys,
The discussion concerning water-pumps reminds me of the arrangement on my VW Corrado VR6. This electric pump certainly ran after the ingnition was switched off, with the radiator fans, to prevent heat soak. I'm not sure if it ran with the engine running but if it did it would provide a useful back-up if the main pump or fan-belt failed.
Like others I always let the car idle for a few minutes when I get where I'm going. If the fans are on at that time I wait until they switch off before turning the engine off. I've always thought that this is good practice but is especially important in turbo cars. I suppose the VW solution is to get round this problem.
Kevin
>> Edited by kevin secker on Wednesday 26th November 11:33
The discussion concerning water-pumps reminds me of the arrangement on my VW Corrado VR6. This electric pump certainly ran after the ingnition was switched off, with the radiator fans, to prevent heat soak. I'm not sure if it ran with the engine running but if it did it would provide a useful back-up if the main pump or fan-belt failed.
Like others I always let the car idle for a few minutes when I get where I'm going. If the fans are on at that time I wait until they switch off before turning the engine off. I've always thought that this is good practice but is especially important in turbo cars. I suppose the VW solution is to get round this problem.
Kevin
>> Edited by kevin secker on Wednesday 26th November 11:33
shpub said:
Leaving the fan on with the engine not running does virtually nothing to help with the engine temperature as there is no water circulating. All it does is cool the radiator and its content until its temperature is reduced to turn the fan off.
Disagree - Any heat sink on a hot engine is worth having, cooling the rad will draw heat away from the engine through the coolant. On top of that you have the fact that the fans are pushing out the hot air under the bonnet, standing next to the front wheels when the fans are on will prove this point.
Ivan
wolosp said:Ahh
That's why when I fitted my two-stage fan kit, I declined to opt for wiring it so the fans stayed on....couldn't quite see the point if the coolant wasn't circulating through the rad.
you DECLINED to opt for wiring etc I really should read things a bit more carefully
ribol said:
Leaving the fan on with the engine not running does virtually nothing to help with the engine temperature as there is no water circulating. All it does is cool the radiator and its content until its temperature is reduced to turn the fan off.
Disagree - Any heat sink on a hot engine is worth having, cooling the rad will draw heat away from the engine through the coolant. On top of that you have the fact that the fans are pushing out the hot air under the bonnet, standing next to the front wheels when the fans are on will prove this point.
Ivan
I think what we may be discussing is the amount of difference. Yes there is heat that the fans push out but that is from the radiator and yes I agree that it will be hot. However the only way that the engine will cool down is through convection as there is no circulation and that effect is small. If a fan belt fails and the water pump stops, it can only take seconds before the engine starts to overheat.
Yes there is an air flow that helps cool as well but again the effect is not that high. There is plenty of stuff in front/on top of the engine that negates it. There is also a cat which is probably about 1000C as well. Probably the best thing is to lift the bonnet if you really want the engine to cool.
I have temp sensors all over the place in the 520. One on the rad inlet, one in the block and one in the air intake by the plenum. Leaving the fans on with the engine off will reduce the rad temp. The air intake temp actually goes up because of the local heating from the exhaust in particular and the engine block temp hardly moves in comparison with the rad one. So yes there is cooling but is it worth the hassle for the relatively small effect it has? I still maintain no.
N17 TVR said:
[quote=M@H]
Edited to add.. do you know who L17TVR is btw.. I see him occaisionally around my way..
[quote]
Matt - unfortunately not, he was 2 years below me at school and we didn't mix with the younger kids. You could ask M17 TVR as he would have been in the year above
You got the wrong plate N17 should it not have been TVR 17A to reflect your age
>> Edited by seasider on Wednesday 26th November 12:46
Even with the pump stopped, water will keep circulating slowly through the cooling system due to convection. This will gradually slow down and stop when the radiator heats up or the stat closes. By running the fan after the engine stops, you can keep this convection going as well as washing heat out of the engine bay. It does work a lot better if you use an electric water pump to raise the water flow rate though. (With the engine off, mine pulls the engine temperature down by about 5 degrees a minute.)
Having read all these threads the best solution for a big engined TVR would seem to be, to ensure that one drives at moderate speed and revs for the last mile or so before switching off.
The objective being to reduce a little the engine and engine bay temperatures that are going to be involved in any subsequent heat soak.
The objective being to reduce a little the engine and engine bay temperatures that are going to be involved in any subsequent heat soak.
look what you have started Phil PeterC said:
Having read all these threads the best solution for a big engined TVR would seem to be, to ensure that one drives at moderate speed and revs for the last mile or so before switching off.
Also has the advantage of cooling down the brakes etc. This is recommended practice for track days BTW.
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