One for the techy's, size of radiators in relation to airflow

[joshg123]

Okay, heres a strange one.

My car is extremley nose heavy, due to having nothing but a diff and rear suspension behined the midpoint of the wheelbase, ive moved the driving position as far back as possible. I am also wanting to shift my radiator to the rear of car. I have plenty of places it can go, but getting air into it, and venting from it is another story.

Being a time attack machine, i am building the fuel tank etc to only do 3-4 hard laps and a out/in lap, so its not doing 20+ laps at a time enduracne spec. My intention was to duct fresh air to the area, but have powerfull thermofans to pull air through.

My question is, and i dont know if you can actually work it out. I dont want to carry excessive weight (coolant) around, so i will fabricate the radiator as small as is required. I was thinking the size of AU thermofans for ease of availibility. Will this be enough?

Can anyone point me in the direction of someone whos done this before. I dont really want to get it all ducted, and plumbed if the radiator ive built is too small for the job

Cheers

[Lump]

seems risky to me - wanting a smaller radiator with much less airflow & more complexity for very little weight distribution gain.

you have all the weight of the 2 new long coolant pipes/brackets/fans/mounts etc vs what you have now.
dont know what water pump you have but you might need a secondary one as well or will the one you have definately be up to it?

i see plenty of quick cars up there with far worse weight distribution than yours going very quick & they are only fwd.

[duste]

If you're wanting a small radiator, why not just one of the Honda Civic rads Josh?

Wouldn't you want as much weight as possible in the rear though? It's going to be light as fuck back there as it is, unless you're planning an epic aero setup to bring huge amounts of downforce in back there.

Best case scenario, I'd imagine, would be to use a full-size radiator with a couple thermo fans and NACA ducts in each rear quarter window to bring in plenty of fresh air. Make some CFRP/GFRP moulds to smoothly transition from the NACA duct tubing size to the thermo fan size and you'd be sweet. On the rear, make another shroud to direct air flow in to a couple ducts exiting through the rear window (which I'm assuming because you're madcore it'll be lexan/acrylic). Another idea could even be to direct airflow out through the floor and have some sort of rear diffuser that would be sucking air out anyway.

KOYO/Mishimoto radiator w/ Davies Craig thermos and you'll be set.

EDIT: Even better, I'd do the rear exit like this:
http://juiceboxforyou.com/wp-content/uploads/2010/09/2263497193_e13e09c576.jpg

That duct above the rear diffuser is the exit for a rear-mounted radiator.

http://juiceboxforyou.com/wp-content/uploads/2010/09/2265512339_6e91ec3911.jpg

And here you can see the inlet ducts on the rear quarter windows - more airflow than NACA ducts but incredibly less efficient.

[monk_13]

What are you doing for underbody aero?

If you are going flat, you could incorperate NACA style ducting under there, with the air feeding up a couple hoses to a rear mounted rad, and then have the air escape out the back end. Similar to above car.

[djr81]

Thin = light. So find the thinnest one you can.

[duste]

What are you doing for underbody aero?

If you are going flat, you could incorperate NACA style ducting under there, with the air feeding up a couple hoses to a rear mounted rad, and then have the air escape out the back end. Similar to above car.

Some problems with that:

1. Dirt, sand, rocks, whatever getting kicked up in to it (you never know). Anything going through could damage the fan, and if it doesn't and gets propelled by the fan, it'll fuck yo' radiator upppp!

2. Hot air from the ground going through and raping your cooling efficiency.

[monk_13]

Some problems with that:

1. Dirt, sand, rocks, whatever getting kicked up in to it (you never know). Anything going through could damage the fan, and if it doesn't and gets propelled by the fan, it'll fuck yo' radiator upppp!

2. Hot air from the ground going through and raping your cooling efficiency.

Valid points there Duste.

Fine mesh or something can be used for "filtering" purposes, and will stop the majority of objects without sacrificing too much airflow. A typical radiator picks up all sorts of track shit in the normal spot. And the fans can be rear mounted (suck through) if desired as well.

Point 2 is more of a worry, and would place's more emphasis on Josh's original question. I do however think it could be overcome in a time attack car, and would be more important in an enduro/multilap car.

[joshg123]

To put my problem into perspective.

Here is a photo of where i intend on putting the radiator, the rear diff is mocked up in a approximate location, inner suspension pickup points are to come and lower control arms will obviously go onto those. I was thinking on making a radiator the width of the hole ive cut in the floor (which goes from chassis rail to chassis rail). I was intending on mounting this radiator to point towards the ground beneath the rear diff, duct air from in front of the rear wheels and have the fans pump the air out in between my taillights.


http://i6.photobucket.com/albums/y220/joshg123/100_0755.jpg