Engine Bay Fan

Actually Ken your car is a lot later than Dave's and mine, So you should have the diagonal engine bay bracing bars, which might get in the way of you bolting/cable tying the fans to the grill like we have. Depending on how much room you have maybe type "B" might be better for you.

My original plan was to fit the fans into the boot lid itself, which might be the way you'll need to go.

Thanks Cobber, and you're right on both counts. Davies Craig don't do under 8 inches and I do have the bracing bars which look like they may interfere.
Thanks for the advice re the model to get and also the option of perhaps fitting in the space between the two skins.
I'll let the group know what I end up doing and I'll take
Some engine bay measurements if possible re temp differences etc.
Ken

Sent from my iPad using Tapatalk HD

I dunno, just suggesting, but if you use type "C" you may well find it easier to fit if you cut those two mounting lugs off, the ones that have the hole centres 165mm (6 1/2") apart.

You could cut out a cardboard template About 125mm (5") square and see where it might fit. For types "A" & "B" I'm guesstimating they're @ 100mm (4") diameter across the fan &125mm (5") diameter overall.

I hope that helps.

Good on you mate, the cars running well but bugger me, its hot here at present. (Not Vic or NSW hot, but too hot for the roof down) of interest, I've also been discussing this mod on the .Org site and there is comment from a member with automotive aerodynamics back ground that the fan may in fact negatively effect engine bay air flow at speed.
More to follow.
Ken


Sent from my iPad using Tapatalk HD

The trouble with aerodynamics is that so much of it is theory.
Sure there are a great many established principals, that are known to be utterly reliable, but it's the never ending variables that make it an art as well as being a science.

Many an aerodynamic design has done well in wind tunnels and computer simulations, only to be found not to work in the real world.

A case in point being the design of the MGF's bootlid, the original design didn't have the vents punched into the top, it had the air ducted through to the rear of the bootlid, exiting where the centre stop light and handle is.
This, got through the design stage to the point of doing the tooling dies for the bootlid pressings.
It was found not to work in prototype testing, so the modified the bootlid skin press die to include the now familiar vent slots, and plugged the old hole up with the handle and centre stop light.
The duct is still in the inner bootlid pressing.

Don't get me wrong, wind tunnels and associated computer simulation programs are fantastic tools, but like dynometers they still are only really comparators and as such useful as indicators to measure before and after changes in hopefully repeatable circumstances.
It's nearly impossible the get any two of the things to come to the same conclusion and there still needs to be real world testing to really prove the product.

I gather the thinking is that the fans may block airflow at high speed. And I did consider this factor.
Well, you could say the radiator fans and their shrouding would do much the same thing, and to a degree they do, but I wouldn't run my car without them.
In fact, it's often common practice to not run fans on race cars at all, because the fans inhibit the airflow through the radiator at high speed, which is of course what race cars are meant do most of the time.

I'd say a bigger variable, to airflow extraction efficiency would be whether the roof is up or down, even whether the side windows are up or down with the top off would probably cause a larger variable to the engine bay airflow than any real or imagined hindrance of air flow through the engine bay by the extraction fans
.
And of course The way Dave and I have ours mounted we can easily remove and refit them in seconds, to suit any circumstances that might dictate such an action.

Now the real world for our cars won't be involved in much high speed work unless they visit the track.
Our cars (and in this case I mean our cars here in Oz) do however have to sit in traffic in baking heat ( with all due respect, heat the like of which most of those in the UK and Europe would never have experienced) and this hot / low speed situation is one of our cars biggest potential problems, one they weren't designed to cope with at all.

I suspect, that these extraction fans would make little or no discernible difference to the actual engine running temperature, but that's not what I envisaged them for, I'm trying to cut down engine bay temperatures to reduce engine heat soak when the engine is switched off and to prolong the lifespan of various engine bay components both whilst the engine is running and at switch off.

All that constant heat build up will be cooking the various rubber and plastic components reducing their life span.
Plastics will get brittle, wiring insulation will break down, rubber will perish and the electronics will fry, under constant excessive heat exposure.
The older our cars get the more we'll see of these problems.
I've been around classic cars for a long time now, and one of the things I've noticed is the cooler you can keep the various componentry under the bonnet the longer it all goes for.

I'm not saying I've got all or indeed any of the definitive answers, but I'm making an educated and considered approach to the problem based on a mixture of experience and intuition, which is really as much as any of us can hope to do.

P.S. maybe our friends over at .org would like the idea of extraction fans a bit better if the fans in question were studded with flashing multi-coloured LEDs :lol:

I think Cobber is the Adrian Newey of Oz! Great analysis, mate :yesnod: I know the car was tested in Australia at prototype stage,but exactly what and where, I don't know.:shrug:

These fans are not difficult to get out I have replaced mine recently. Disconnect the electrics connector, and undo the two fan cowl retaining bolts with a socket . Then twist and turn the assembly and it lifts out. Reverse to fit new assembly. This is a ten minute job.

Sorry Stephen;
Which fans are you referring to?
It may give me the drive to swap some over for modern designs.
Thanks mate.
Ken


Sent from my iPad using Tapatalk HD

The engine bay fan is the one located at the off side of the engine adjacent to the intake. its function is to cool the engine bay

The extraction fans are, to work in conjunction with the standard engine bay fan they're not intended to replace it.
The problem with the standard engine bay fan is that a lot of the air, it's meant to pump into the engine bay is lost by spilling out the bottom of the engine bay, so it leaves a lot of hot air somewhat undisturbed at the top of the engine bay.
The extraction fans, are there to push some more of this hot air out.

stephenj wrote: These fans are not difficult to get out I have replaced mine recently. Disconnect the electrics connector, and undo the two fan cowl retaining bolts with a socket . Then twist and turn the assembly and it lifts out. Reverse to fit new assembly. This is a ten minute job.

Seems like 12 months ago I did it the hard way then :oops: