Push or pull

gelmonkey · Post by **gelmonkey** » Tue Oct 04, 2011 2:12 pm

Hi All
My motor is getting a little too warm when sat in traffic.
Fan is in push mode sat on front of rad.
Have large ali rad,16" electric fan on Audi temp switch and overide switch on dash.
Fan comes in just over 180.
Main problem not too much open space at front of car for airflow when sat.
How big a difference do you think it would make if fan put on back side of rad and switched to pull mode?

Ta v much

cheers
Paul

SuperV8 · Post by **SuperV8** » Tue Oct 04, 2011 3:04 pm

The fan is more efficient when it's pulling air through the rad. The air is very turbulent as it leaves the blades so it its pushing air through the fan the air won't take as much heat with it.

One point to double check (I made this mistake) check the blades are actually the correct way around. The blades are aerofoil in shape same as an aeroplane wing and use both the angle of attack and the aerofoil shape to lift the air. It is possible to get the wrong combination so the fan will still push the air BUT it will be doing it inefficiently. (same as an aeroplane flying upside down!)
When the fan is pushing air through the rad the flat surface of the blade needs to be next to the rad. When pulling the curved surface needs to be next to the rad. Easy to get it wrong even though air is moving in the right direction.

Also can you desctibe your coolant plumming layout?
Quite common for there to be too much bypass coolant flow, which means a large volume of coolant misses the rad!

Tom.

gelmonkey · Post by **gelmonkey** » Tue Oct 04, 2011 6:38 pm

Hi Tom
I know that the fan would be much better on the back of the rad but am really anal about an uncluttered engine bay look and putting the fan engine side is not really what I want to do but sometimes needs must.
Here is a picture of my radiator /plumbing layout.
Pretty much standard.
Have also thought about two small fans on the engine side of the rad to help cooling but dont know if the fan on the outside will shroud them too much.

I have about 3"behind the rad and the water pump pulley but thats about it.
Have looked at a Zirgo 3000cfm fan but it is just too big for my application.

cheers
P

Ian Anderson · Post by **Ian Anderson** » Tue Oct 04, 2011 7:09 pm

Have you got vents or anything on the bonnet to release the hot air?

Perhaps when moving the hot radiator air can get forced down past the engine, but whenp slow not enough fan force to push the hot air downwards under the car

Ian

ChrisJC · Post by **ChrisJC** » Tue Oct 04, 2011 7:12 pm

Get a nice engine driven fan. Never any bother.

Chris.

gelmonkey · Post by **gelmonkey** » Tue Oct 04, 2011 7:33 pm

Ian Anderson wrote:Have you got vents or anything on the bonnet to release the hot air?

Perhaps when moving the hot radiator air can get forced down past the engine, but whenp slow not enough fan force to push the hot air downwards under the car

Ian

Hi Ian
Yeah got a big F/O vent at the back of the bonnet and a smaller one at the front.
You can just see where the bonnet drops down to the base of the vent at the front.
This is a fairly big vent which I had hoped would help get rid of heat build up when in traffic.
I have a plate over the top of the fan (see pic in first post) and wonder if this is helping or not as the air is forced through the rad rather than all around it

No the trailer is not mine (shudder the thought)

The motor runs just spot on when running even at 20mph but as soon as I slow down to a crawl thats when it starts to climb.
Have seen it get close to 210 and that is too hot IMO.
What do we think apart from bolting on a windmill blade to the motor?

cheers
P

ramon alban · Post by **ramon alban** » Tue Oct 04, 2011 8:42 pm

gelmonkey wrote:What do we think apart from bolting on a windmill blade to the motor?

There are a raft of things you should consider, some already mentioned, but this covers them all:

# Air must be pulled thro the rad - avoid turbulence and scattered air.

# Use a cowl - ensures that ALL the radiator gives up heat to air flow.

# All galleries must allow free coolant flow - flush and reverse flush.

# Lower temp stat - opens fully before the engine temp gets critical.

# Water pump blades in good nick - no inefficiency caused by cavitation.

# Pump bypass circuit - too large diameter disallowing radiator flow.

# Radiator too small - simply unable to give up enough heat.

# Fan temp switch set too high - lower setting to approx 5C above stat

# Engine driven viscous - rapid negative feedback to rad temp changes

# Air Locks - Trapped air allows internal engine hot spots to make steam

# Pressure cap - correct spec or working ok raises coolant BP to 130-140C.

# Fuel/Air mixture - running too lean causes overheating.

These two article may be adapted to apply to your system.

http://www.vintagemodelairplane.com/pag ... emp01.html

http://www.vintagemodelairplane.com/pag ... ing01.html Follow the link and Open the PDF

Hope this gives you some things to consider.

gelmonkey · Post by **gelmonkey** » Tue Oct 04, 2011 9:15 pm

Thank you Ramon
Most things covered in your post apart from a few so may well have to consider swapping the fan over to the engine side and see how that goes.
Will read the articles a bit later tonight
Thank you also for the help with the speedo issue that is still on going but I will get there and keep all those interested informed.

cheers
Paul

SuperV8 · Post by **SuperV8** » Wed Oct 05, 2011 11:39 am

Looking at the engine photo your bypass hose looks very large to me.

You could still get a large flow through the bypass circuit which will miss out the rad!
You could try crimping the bypass hose to reduce the bypass collant flow and see if that helps?

Also as I said in my previous post can you double check and confirm the fan is the correct way round?

Tom.

Ian Anderson · Post by **Ian Anderson** » Wed Oct 05, 2011 11:49 am

Paul

That car looks fantastic and the engine compartment so uncluttered - I am jealous - so much neater than all the wires for Efi

Sorry cannot give more input on the cooling issue than already given

Ian

DaveEFI · Post by **DaveEFI** » Wed Oct 05, 2011 12:15 pm

Ian Anderson wrote:Paul

That car looks fantastic and the engine compartment so uncluttered - I am jealous - so much neater than all the wires for Efi

My initial reaction was the spark leads are too closely grouped. Rule of thumb is they should be spaced away from anything by their own diameter.

gelmonkey · Post by **gelmonkey** » Wed Oct 05, 2011 1:41 pm

Tom,Dave and Ian
Bypass looks huge I agree but is standard SD1 internanl hose size.
Am going to check the fan orientation tonight as you suggest but am fairly sure it came as a puller from Trimline.

Dave,
Yes the HT leads are to close together but as I have said I am a little too anal about engine bay appearance.
I know that they should be further apart but then it all starts to look a biit like a snakes wedding.
I have no crossfire issues though the car runs sweet right through the rev range.

Ian thanks for the help and the kind comments about my wagon.

cheers
p

Darkspeed · Post by **Darkspeed** » Wed Oct 05, 2011 4:33 pm

As pointed out above - cowls are very important many traffic overheating issues are down to the fan just circulating the hot air round and round the rad - In your case finding it easier to push through the rad and then just drag it round or through the rad not covered by the fan rather than drawing in cool air from the grille and pushing it out through the bonnet.

May be worth placing a smoke bomb just infront of the rad to see what the circulation is doing.

Andrew

gelmonkey · Post by **gelmonkey** » Wed Oct 05, 2011 5:46 pm

Hi Andrew
It really does look like I will have to swap the fan to the other side of the rad and I will have to live with it like that as long as it works.
The reason for putting it in front was just for asthetics/clean engine bay but this is proving to be an unwise desicion.
The fan does have an integrated cowl and am hopeful that swapping sides will get rid of this small problem quickly and cheaply.
Thank you for your comments and yes I know I should'nt be so feckin fussy!!

cheers
P

Ian Anderson · Post by **Ian Anderson** » Wed Oct 05, 2011 7:28 pm

Can I ask something stupid? Does the fan move the air the right way? It may not be the first time that the fan has worked against the natural flow of the air. At stop no cooling problem fast and no cooling problem only when at slow speed it over heated!

Ian[/i]