I'm planning to place the radiator in the back of my 1973 1303 beetle.
See details:
http://home.tiscali.nl/~gmolhoek/alfa/radiator/index.htm

Tell me what you think of it.

I seriously doubt that you will be able to get enough cross-section area of ducting up to rid the waste heat of a 200kW engine. The EJ20T conversion I was involved in seems marginal - and that is with the rads and two thermo fans up front

The ducting from under the car will also be expensive and vulnerable

Another factor - more weight, more rearward and higher... not real flash for handling.

BUT if you are willing to cut sheet, try it and see. If it doesn't work, it will be easy to rectify

I've already done that, and have been running that set-up for over 2 years.

Perhaps you should read this post;
http://forums.aussieveedubbers.com/viewthread.php?tid=40641

Some pictures aren't working as my site is changing servers

you can make anything work if you want, but why reinvent the wheel?

the rad will work better at the front, even VW did this when they turned Type2s into water pumpers. And this is coming from a man with a rear mount rad.

As much as I hate to say it, I'm sure you could make it work for a small engine like this if you are really against cutting up front. If you look at my speedster cooling system from the Alfa days it had a mini radiator either side of the bellhousing and that cooled fine but was at its limits with 120bhp. Depending on the hight that you mount them you may be too reliant on the electric fans which I would NOT want in any situation. One of the better rear rads I have seen is the Bennetton F1 styled wasserboxer bug on design 90's which had it at the upright position where the firewall was and fully enclosed with rear quarter panel Remmele style ducts...

Rich

Gentlemen, thank you for your replies.

I'm going to give this setup a try.

gerrelt. talk to 72rsbug about this. i know i have and his ej20tt is having cooling problems and he said to me that he is doubting the functionality of the rear radiator setup. i think he is starting on a front radiator setup in the spare wheel well.

i would go something that has been proven as it is not worth the money nor the time to do the install just to find the motor runs hot or gets damaged.

it is an alfa motor you are using yeah?

i dont know how the alfa 4cyls run but mum has a 156 with the 2.5l v6 and it runs quite hot considering.

Anthony

mine gets hot on the highway because I currently have no scoops at all.

I hoped the low pressure behind the car would suck the air through. It works fine up to 100kph. Over that and the air flowing under the car is going so fast it seperates at the rear torsion bars and creates a low pressure under the radiator. Essentially the air is going to fast for the flow to curve up under the car and turn into the radiator.

I also think when this occurs because the radiator is in a low pressure pocket, but the cooling fans are going, it just causes the air coming out of the radiator to turn back around under the radiator and recirculate. A plate at the rear of the radiator extending down around the gearbox would fix the recirculation.

I am sure the lack of air flow at 100kph+ will be fixed with a couple of scoops mounted off the trailing arms / torsion bars. Don't bother with pipe style ducts, they will be too small and won't provide enough air. You need a plate as wide as possible.

Your also going to have to cut out alot more than you have shown for the radiator. You want to cut out the whole parcel area and put a curved cover in there, so the air flow into and through the radiator is smooth.

I agree with wes on the scoop front. Pipes are too small. You need a ducting that is at least 1/3 the surface area of the radiator if you are going to get enough air. Ricola clued me up on this when I made my scoop.

Secondly, I've read the reply you got from the guy on the shopforums and looked at his pinto/bug conversion. His radiator had the fan running all the time. This a bad idea coz firstly, it drains a lot of current from your alternator and secondly, if the fan dies, the motor cooks very quickly. And factory fans are not designed to run constantly.

Another thing to consider is that you need COOL air getting the rad. This means scooping air from the outside of the car into the rad box and then getting rid of the hot air effectively when it's done it's job. Making a shroud for your fan will help it work better too.

Look at my write up on what I did for mine...

http://www.geocities.com/peterwood734/buggyproject/buggyproject10.html 

I have since discovered that the rad gets so much air from the scoop that the fans hardly come on the freeway...that and the temp maxes out at 85deg, even on hot days at over 110Km/h. This is ideal.

ARR NO NEED FOR ANY MORE DISCUSSION ON THE MATTER AS BUGGY BRAD ( IM THE EXPERT JUST ASK ME I BROUGHT A VW SHOP) HAS SPOKEN... :sandrine

And as per usual VDUBYA has offered another futile attempt at being funny. If only that little brain of yours could control your rogue fingers from typing.....

Back to the topic...there have been hardly any problems with front radiator setups, yet I have heard of numerous cooling probs with the rear setup. It is really busy back there and I am finding running a 3.5 inch flexible tube to my air filter a squeeze.

Good luck whatever you choose...copy one that works!

Matt

Im for Brad with evidence than vdubya with vitriol

I have found with my experience in regards to a supercharged Holden 6 cylinder motor, that airflow is not the only factor. I had a 3 core radiator with two big thermo's on it and at higway speed was the only time it got hotter, due to the extra hp it was using to go that fast.

Physics is a science with laws that cannot be changed and in this circumstance the radiator was simply not big enough. The heat generated from the hp was not able to be removed from the fins of the radiator, no matter how much air was put through it. This is a front mounted radiator in a Holden dont forget.

The solution was to provide more physical surface area to remove the heat. This I did with a performance radiator designed for 350 Chev install into EH. Seeing as my motor was now putting out similar hp figures as a warm 350, it seemed logical.

In the end the problem was solved and it runs sweet as.

My opinion the rear setup will work if you have the required amount of air and a large enough radiator. You can get custom units made by companies like Aussie Desert Cooler.

The other EH I have has twin 9" thermo fans on it which are awesome. I got them from the USA with an air conditioning condensor setup, and I recommend 2 x 10" rather than a single 12". 2x12" fans would be even better.

if I get time at work I will do some quick calc's for you guys to show you how the air flows.

So you start by quickly modelling the rear of a beetle (baja style), gearbox, torsion bar, axle and suby motor in CAD. This was a real quick job. You only want a cross-section, no wheels or anything.

then you put it into a CFD program (computational fluid dynamics).

Below is a simulation of it travelling at 100kph. notice the air doesn't want to flow through the radiator area by itself at all. This is what I am currently running in my car, so no surprise it gets hot on the highway.

When I get time I will model 100kph with scoops, and some slower speeds.

I'll probably get shot for this, but perhaps run a whale tail and have the radiator under the wing? Is that possible? or is it too much weight?

works for Reub's car...or is it just the intercooler in the back?

Wes, what program did you use to get that? I'd be interested in running a couple of ideas through it...
Rich

Cool! Wes is getting scientific! That's a really usefull picture. I like where this discussion is going.

But, if I put the scoop in your picture where I planned it, it would be right in the air-flow. Like this:



I would be really interested in that picture of the airflow with a scoop, Wes!

Great replies!

Rueb has the intercoolers in the tail.

Matt

Sorry Pete you are totally right, in an effort to make a constructive coment to the post I have been preparing a air flow diagram just like our technical guru Wes. Unfortantly I can not post it as yet as the kids are hogging the coloured crayons.

I wouldn't say me and Brad are VW legends. However we do know a thing or two about engine conversions, and I'm sure Brad has already done more conversions than nearly everyone on this forum (we do have a few good experienced guys here) and tried a lot of different theories in the process.

I only post in posts that I know something about. Unlike some people on this forum that post in posts they pretend to know something about, or just can't help themselves from wanting to sound like they know something.

How about the pessimists in this post go elsewhere. This is a good thread with some good info. I don't want to have to moderate peoples posts.

What we need to remember COLD AIR is needed to the RAD.Dragging air from under the car on a hot summers day,a hot road and air being dragged to the RAD to the rear of the car is not very effective.....COLD AIR sits higher.Look at setting some NACA ducts from the side or top of car.A RAD up front is capable working better and attracting COLDER AIR and practicle.......Just to note Brad & Baja Wes know ther stuff ...JVLRacing

true, the air low near the road is hot. But you have the same problems with a front radiator in a beetle unless you cut holes in the bonnet.

Again from this perspective the rear radiator is more suited to a baja than a lowered beetle, as you get a heap more air under the car so the bulk of it isn't so hot.

So if you set some air scoops under the car,at the end of the tubes set some electric fans that will draw the air colder to the rad.That possible make the air cooler for a baja.Do you think that would work?....JVL