Uprated cooling fan?

[Nuttah]

Is anybody clued up on cooling fans? i would like to upgrade the one on my rs turbo for summer, Last year we had some VERY hot day's, Engine temp was ok but in traffic in the intense heat it was too close for comfort. I would like to install an uprated fan this year for a little peace of mind. I am not fussed about it being noisy just something powerful. Any recomendations on brands/models to look at?

Thanks

[TooMany2cvs]

Is the problem that the fan's putting insufficient air over the rad?

Or that the rad's not doing a good enough job of converting that airflow to heatloss in the coolant because it's silted up...?

Basically, are you fixing a design flaw, or working around something broken?

[DrDeAtH]

How old is the radiator, and is the car modified?

If the answers are old, and yes,. Replace the radiator with something a bit better and a thicker core

[tr7v8]

Go through the cooling system, checked the rad is 100%. I found on the TR7V8 one of the secrets was bringing the fan in earlier. So I change the otter switch for a lower temp one. Also put a relay onto the fan if it doesn't have one so it gets full power with no volts drop.

[stevieturbo]

Nuttah said:

Is anybody clued up on cooling fans? i would like to upgrade the one on my rs turbo for summer, Last year we had some VERY hot day's, Engine temp was ok but in traffic in the intense heat it was too close for comfort. I would like to install an uprated fan this year for a little peace of mind. I am not fussed about it being noisy just something powerful. Any recomendations on brands/models to look at?

Thanks

If the temperature in traffic was ok....how was it too close for comfort ? That makes it sound like it was not ok ?
What fan/rad setup do you currently have ?

OEM fans are often hard to beat

Other than that and what others have said, Spal make some of the best fans

[GreenV8S]

Increasing the air flow will help, but it will give diminishing returns. Don't expect a significant improvement in cooling unless you massively increase the fan performance.

The fan will be most effective when it is shrouded to pull/push air through the whole of the rad surface. If the fan isn't shrouded, fitting a shroud will help cooling at idle. Note that it will tend to reduce cooling at high speed, although that is unlikely to be a problem.

Make sure that hot air from the engine bay can't be pulled round to the front of the rad and sucked through it again. Whatever percentage of air recirculation you get comes directly off the cooling capacity. You can test for this by measuring the air temp on the 'cold' side of the rad compared to ambient.

Internal and external corrosion will act as a barrier to heat transfer. You may find that flushing and descaling the rad helps but if the rad is old then a new one of similar spec will probably give better cooling - or take the opportunity to uprate the radiator while you're at it.

[PositronicRay]

Nuttah said:

Is anybody clued up on cooling fans? i would like to upgrade the one on my rs turbo for summer, Last year we had some VERY hot day's, Engine temp was ok but in traffic in the intense heat it was too close for comfort. I would like to install an uprated fan this year for a little peace of mind. I am not fussed about it being noisy just something powerful. Any recomendations on brands/models to look at?

Thanks

I've a powerful fan here you an have if you want? I think it's a pusher from a Volvo.

[PaulKemp]

Having fitted an engine putting out nearly twice it's designed bhp in to a Lotus 7 replica with a small nose area and a tight engine bay I have some thoughts on cooling that may help.

You don't describe the temperature profile as observed. What temp does it run normally? Does it overheat on Rickover if so after a hard drive or every time?

My solutions were ....
An earlier opening thermostat, it's the cheapest easiest way to give a bit more cooling in the system you currently have.
Making sure the gaps round the radiator are sealed so air can only go through the radiator helps but if your stationary you won't see much benefit.
I made sure the hot air in the engine bay could get out and in my case I propped the rear edge of the bonnet 10mm which made a surprisingly big difference.
A bigger oil cooler with thermostat.
A twin core radiator with more cores than standard, ally radiators are supposed to be more efficient.
There are other things that can help such as antifreeze and water wetter.
Some aftermarket fans have a boost facility, an overspeed but I assume they need there own thermostatic switch.

[S0 What]

If it's the standard S2 fan it's actually an AC fan from a Mk2 granada and TBH was at it's limit when new as were the rads (due to squeezing the I/C in next to it) no doubt after all these years it's not reaching full speed either, pacet make good fans, i've used them in the past without issue on RS turbos but you may need to trim the rear of the bumper/grill to fit it in
To be very honest i'd probably be looking for an uprated rad or at the very least a new core in the old one, an uprated unit will cost you around the £300 mark from somone like radtec or £220 ish from AIRTEC (burtons stock them at just under £220), a recore would i expect be around the £150 mark ? it's smaller than the XR3i rad (to fit the I/C) but thicker so the core will be more than a normal rad recore.

[McVities]

PaulKemp said:

My solutions were ....
An earlier opening thermostat, it's the cheapest easiest way to give a bit more cooling in the system you currently have.

Whilst you may have found this works for you, a lower temperature thermostat is not the best way of achieving better temperature control. There are many factors which dictate how much heat energy a cars cooling system can shed, primarily it is the size (and surface area) of the radiator, the bigger the surface, the more energy that can be radiated away.
After this, there is then the temperature of of the coolant within the rad - energy flows at a rate proportional to the difference, i.e. the hotter the coolant and rad are, the more energy per unit time that will be shed to the surrounding air.....essentially the cooling airflow over the radiator will leave a hotter rad at a higher temperature than if it had passed over a cooler temp rad, this will remove more energy from the hotter system.
Airflow through the radiator - more is better, and a properly ducted/sealed system will pay off - as per below:

PaulKemp said:

Making sure the gaps round the radiator are sealed so air can only go through the radiator helps but if your stationary you won't see much benefit.

Having a thermostat which opens earlier at a lower temperature will help slow down the rate at which the engine gets to higher temperatures or overheats, but as it does nothing to the rate at which heat is lost from the engine will not actually stop it from happening. If a car is overheating, something is not functioning correctly and needs addressing.

PaulKemp said:

I made sure the hot air in the engine bay could get out and in my case I propped the rear edge of the bonnet 10mm which made a surprisingly big difference.

Getting the hot air out is important, but doing so appropriately is more so. I would imagine the exterior airflow around a Lotus 7 differs a tad from an RST. Does your Lotus have quite a small windscreen? I only ask, as with most 3-box style cars, the air pressure at any sort of speed tends to be higher than atmospheric to the front of the grille/rad, with lower pressure just behind the apex/leading edge of the bonnet. Then as you move rearwards along the bonnet towards the windscreen, the pressure normalises then becomes higher, where it is highest at the junction of the rear of the bonnet and base of the windscreen.
I tried jacking up the rear of a bonnet once with spacers, and found that running temperatures actually were higher at cruising speed on the motorway - the new gap at the rear of the bonnet was allowing the higher pressure air to enter into the engine bay. This reduced the pressure differential across the rad, and thus the airflow through it. The RST (if series 2) already has some bonnet vents in place, which should cover this angle nicely.

PaulKemp said:

A bigger oil cooler with thermostat.
A twin core radiator with more cores than standard, ally radiators are supposed to be more efficient.
There are other things that can help such as antifreeze and water wetter.

These points are where you will have made your gains - the bigger oil cooler will shift more heat, remember oil is a coolant medium too and not just a lubricant.
The twin core rad will be more efficient than the previous incarnation, again shifting more heat.
The correct mix of water and anti-freeze will provide a decent specific heat capacity (pure water is best in theory for S.H.C, but not for boil/freeze or corrosion protection), whilst still depressing freeze points and elevating boiling points. Water wetter (a surfactant - reduces the surface tension of the coolant mix) will again provide a small gain through improved heat transfer at coolant-metal boundaries.



OP if you are on a tighter budget, first of all clean out the cooling system - maybe use a chemical de-scaler, then really flush everything through clean. Clean the outside of the rad too - get rid of all the dust, grime etc, be careful with the fins, they will be delicate. Some fins may be bent out of shape, see if they can be gently persuaded back into place. Then, find a suitably sized fan with higher airflow - look for the current rating, the more amps it draws, the more air it will shift. Wiring it direct via a relay is also a good plan.
Dare I suggest, turn the boost down a psi or two? Less energy in means less to get rid of.

I would also consider some under-bonnet insulation - can you wrap the manifold, turbo and/or downpipe? Keep the underbonnet temps a little lower.

The uprated rads suggested by S0 What look a good option too - just make sure to clean out the cooling system before you fit it.