Temp drop on a radiator

[jmorgan]

OK, just trying to get my head around this. Sorting the huge gaps around my rad and just wondering if there is any info on the efficiency of radiators. I do not know the spec on mine but with a infra red temp sensor I can measure the difference in input and output. I appreciate this may not be accurate but is there a ratio I can expect?

Also related, I assume that in ducting as much air as possible or rather stopping air going around the rad I am improving things? This leads on to the fans. I am not sure they are up to the job. They are butted tight to the rad. I had a wind speed checker jobby and measured 30mph but that was not across the whole diameter. Towards the outer diameter. The inner did not register much. No info on the fans.

I should add that normal running the temp is OK. OK to a point in traffic but does climb and I have a manual override. I do suspect the fans are not the best. Any pointers there would help.


Cheers

[Snake the Sniper]

Going to need a little bit more info. What car and what engine? Ducting the rad should help, as it forces the air to go through the rad rather than around it. Is the fan in front or behind the rad? Moving it behind the rad can make some difference, but not always. Also, channelling the air through the rad is good, but it does need somewhere to go afterwards, so it helps to have a suitable way of venting al the hot air.

[jmorgan]

Right o. TVR and Rv8 4.2. Rebuilt. The rad is the largest core that will fit the existing fixings and side tanks. Recent accident damage lost what little foam there was around it and I am boxing the area or blocking gaps to get the air through. But that is fine traveling along. It's creeping in traffic that gives me the worries. That is why I suspect the fans etc.

Anyway. Fans are behind, cover most of the rad, that is the diameter is is about 2 or 3 inches short of the height (and yes the suck;)). Most versions of this car appear to have no ducting after the fan, even the fruitier versions. And no info on the fans.

Edited by jmorgan on Thursday 31st July 12:36

[Snake the Sniper]

Looks like the fans aren't pulling enough air through the rad and/or the engine bay to keep things cool. If it's ok when moving, but creeps up in traffic, then air flow is the problem, rather than insufficient cooling capacity. Might be worth seeing about stronger fans. Have you tried the usual things like water wetter? This may make the system less marginal in traffic and help keep it cool.
PS, ally rad or metal/plastic? An ally one will generally help keep things much cooler.

[jmorgan]

Alloy rad is on my list but it needs some cash. Think I will attack the fans. So if I read this right, I would have issues traveling normally if it is a rad capacity problem? Still be nice to verify the temp difference though.

Ta.

[Snake the Sniper]

Yup, you are correct. If the cooling system isn't up to dealing with the engine, it will overheat if driven as a TVR should be! Ie most of the time.
As for the actual temp drop across a rad, the easiest thing would be to buy a cheap IR thermometer from Maplins or similar. You just point it at bits of the engine and press a button to see how hot they are. Quite interesting really to see just how hot some bits get.

[rev-erend]

Jeff - also make sure you are using a 74 degree stat - this helps a lot.

See my thread for Mat-Man on the wedge forum.

Cost is only £10 - so worth doing.

[v8ian]

There is a popular misconception that Bigger is better with rads, Many Rads that are recored with more cores do suffer from bad airflow because of the extra cores blocking airflow, this in turn slows and even stops the air flow thru the rad, thus negating the effect of the extra cores and often making the cooling situation worse. I know ive made the mistake,
for the fans to work correctly they need to be mounted as close to the rads as feasable, having a airgap between the rads and fans will allow them to suck air in from outside the rad and not drawing the air thru the cores, Air like water will take the route of least resistance.
Another thing that is often done is remove the Thermostat, which allows the water to run thru the rad too fast and not allowing the heat to transfer to the rad fins and then to air. it will also not allways allow the engine to warm up and this in turn promotes engine wear
Ian

[andyquantum]

Done something similar on the Quantum as part of a turbo conversion. Swapped to an alloy rad (have a look at Radtec) and Kenlowe blower fan rather than suction. Spal would be cheaper, I've always used Kenlowes

[jmorgan]

Thanks for the input all.

Alan, 82 at the moment. Not a problem tootling along just in heavy traffic or standstill.

The recent bump lost all the cladding around the rad and in the process of blocking it all back up. I was concerned that warm air from the engine bay was making its way back in the front in standing traffic. When the fans are on it ain't half hot comming from under the car. The fans butt tight to the rad back. I do suspect the fans though and easier to change them at the moment than the rad for some known air flow kenlowe spiral type jobbies. Failing that its the belt and braces rad on TVR car parts.

I also notice that wedges have a huge gap between the spoiler and rad at the bottom. Now plated up. Foam has arrived to fill in the rest of the gaps where I cannot easily plate it up.

[neal1980]

Which type of fan is best if you can get both in suck or blow. Sounds wrong in my perverted mind that!

[Howitzer]

We used to aim to get an 8°C drop from coolant out temp to coolant in temp when testing. This was on tractors though.

Dave!