My car is overheating when idling since getting the supercharger fitted.

Its fine on the open road but it quickly overheats on idle.

I've checked the obvious items.

1) Fan is working correctly
2) No air in system (bleed multiple times)
3) Correct coolant levels

I've discovered that everything is fine when the bodywork (nose and bonnet) is off the car. Fan kicks in, cools the car down and turns off again. Once its all back on the problems start. I assume that its under body heat that is the issue.

I'll look into getting a bigger fan on the basis more air will give better cooling but if the hot air is being trapped that might not cure the problem.

The exhaust isn't heat wrapped. Is that likely to make much difference?

Any other ideas? The velocity has a bonnet scope but I'm not sure how much heat that lets out. More vents?

More vents at the back of bonnet. Wrap the exhaust or some sort of heat shield would be best.

What is the ignition timing at idle ? retarded timing makes the gas temperature at the end of the combustion stroke very high which means a lot of waste heat gets rejected to the cooling system and exhaust.

Good question, I'm not sure how the timing is configured but it was retarded to reduce power. It made 260bhp on the dyno and got retarded to 248bhp for engine longevity.

Think I've got room for a second or bigger rad fan but its going to be a squeeze. Hopefully this plus exhaust heat wrap might be sufficient to expel enough air.

I found cutting some vents into the rear of the bonnet and lagging the exhaust manifold reduced the under bonnet temperature on my Luego locost . Water wetter also reduces coolant temperature

What management are you running - or is it stock and the dizzy tweaked to reduce the maximum advance? If the latter, then it's retarded way too far on idle now, hence the mixture is still burning whilst going down the exhaust, rather than being used to propel the engine!

If the "only" thing you've done is add a supercharger, then the blame can't be put on a water pump.

Its running an OMEX 600 ECU. All I've done is add the supercharger although the fan was changed from an 11" pusher to a smaller puller due to space requirements.

It's running a 7.5" Revotec fan now. Not sure a 9" Revotec fan will fit but surprisingly I might get two 7.5" Revotec's side-by-side.

Need to see if I can pick-up a fan tomorrow or Friday so I can drive to Stoneleigh on Monday.

7.5" sounds rather small for a single fan IMHO..

If you've added an intercooler in front of the rad, the (small) added restriction plus a smaller fan won't help matters at all. Might be enough to tip it over the edge?

Just purchased a second fan so now I'll be running two 7.5" Revotec's. Hopefully that will do the job.

Might also grab some bonnet vents at Stoneleigh and exhaust wrap to be on the safe side.

What temperature does the fan kick in at, might be worth lowering it if you can.

Fan kicks in at 92 and goes off at 90. I've changed the settings to on at 90 off 88 and it does slow the overheating down but doesn't stop it.

I could try using 88 and 86 as short-term thing to buy me a little more time.

I still suspect one of the causes is the advance curve around idle speed.

However it is also apparent you need more air cooling the only things that will help the symptoms is to get more flow air in contact with the coolant ie a bigger rad and or fan(s) and extractor vents.

Extractor ducts will reduce the back pressure (aka "blockage" on the fan -- but be careful as a duct positioned in a high pressure area such as too close to the base of the windscreen can cause reverse flow at speed. The area towards the rear of the nose is usually a low pressure area because the air is flowing faster at this point, hence "nostril" vents on the upper surface of nose behind the rad on late 1960s early 1970s F1 and CanAm cars. such as the Lotus 49B

Link to Lotus 49B photo http://cars-database.com/data_images/gallery/03/lotus-49b/lotus-49b-05.jpg

McLaren M7 picture link http://en.academic.ru/pictures/enwiki/72/Hulme68.jpg

[Edited on 2/5/13 by britishtrident]

Thanks for the comments and advice

Second rad fan now fitted. Problem appears to be resolved.

Thats good news, see you at Stoneleigh