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 gerrelt
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| posted on October 12th, 2005 at 07:19 AM |
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radiator in the back idea
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.
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VWCOOL
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| posted on October 12th, 2005 at 07:31 AM |
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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
Pay your debts, CxxT
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Baja Wes
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| posted on October 12th, 2005 at 08:49 AM |
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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
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Brad
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| posted on October 12th, 2005 at 01:49 PM |
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mmm
| Quote: | Originally
posted by Baja Wes
I've already done that, and have been running that set-up for over 2 years.
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Yep and it is in a Baja with heaps of air flow and still gets hot on the highway... maybe scoops will help but bug is much lower to the ground and
doesn't see anywhere near as much air flow as a baja.
Not saying it won't work but I think you will have to cut a hell of a lot of sheet metal out to make it work.
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pete wood
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| posted on October 12th, 2005 at 04:52 PM |
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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. 
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ricola
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| posted on October 12th, 2005 at 05:52 PM |
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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
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gerrelt
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| posted on October 13th, 2005 at 07:32 AM |
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Gentlemen, thank you for your replies.
I'm going to give this setup a try.
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71superbug
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| posted on October 13th, 2005 at 07:46 AM |
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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
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Baja Wes
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| posted on October 13th, 2005 at 09:03 AM |
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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.
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pete wood
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| posted on October 13th, 2005 at 04:11 PM |
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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.
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VDubya
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| posted on October 14th, 2005 at 12:54 AM |
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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 |
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boof2332
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| posted on October 14th, 2005 at 07:23 AM |
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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
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koolkarmakombi
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| posted on October 14th, 2005 at 08:02 AM |
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Im for Brad with evidence than vdubya with vitriol
This disclaimer does not reflect the thoughts or opinions of either myself, my company, my friends, or my dog: don't quote me on that; don't
quote me on anything; this disclaimer is subject to change without notice; text is slightly enlarged to show detail; resemblance to actual persons,
living or dead, is unintentional and coincidental; dry clean only; do not bend, fold, or mutilate; anchovies or jalapenos added to this disclaimer
upon request; your mileage may vary; no substitutions are allowed; for a limited time only while supplies last; offer void where prohibited; this
disclaimer is provided "as is" without any warranties expressed or implied
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Baja Wes
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| posted on October 14th, 2005 at 08:39 AM |
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| Quote: | Originally
posted by koolkarmakombi
Im for Brad with evidence
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Well Buggy Brad's evidence is actually my car, so maybe you should be listening to the owner since everything Brad knows is 2nd hand information of
what I have told him (not talking anything away from Brad's expanse of knowledge, we are good friends afterall  ).
My rear radiator set-up runs hot at highway speeds+ only. This is because it currently has no scoop at all. It seems pretty logical that the scoop
will give it the air flow it needs. The engine also works harder on the highway being an unaerodynamic Baja and all.
A front radiator hidden behind the body work would also probably get hot too unless you add some sort of scoop to kick the air up.
Having said all that, The front radiator set-up is easier to pull off successfully. In a beetle I would put the radiator at the front for the easier
cooling, and better weight distribution (you want more at the front to counter the extra engine weight at the rear).
I went rear on the Baja because offroad you want all the weight over the drive wheels and can live with some understeer. The rear radiator is also
more protected from damage from the ground and stones from the car in front.
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pete wood
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| posted on October 14th, 2005 at 04:15 PM |
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| Quote: | Originally
posted by VDubya
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
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um yeah, ok, right whateva. :o
Have you got that out of your system? coz if you have maybe you'd like to help the discussion now.
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 helbus
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| posted on October 14th, 2005 at 04:52 PM |
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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.
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Baja Wes
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| posted on October 14th, 2005 at 05:55 PM |
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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.
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Baja Wes
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| posted on October 14th, 2005 at 05:58 PM |
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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.
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oval TOFU
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| posted on October 14th, 2005 at 06:01 PM |
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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?
...and Robert's ya father's brother...
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pete wood
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| posted on October 14th, 2005 at 10:29 PM |
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works for Reub's car...or is it just the intercooler in the back?
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ricola
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| posted on October 15th, 2005 at 04:58 AM |
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Wes, what program did you use to get that? I'd be interested in running a couple of ideas through it...
Rich
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gerrelt
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| posted on October 15th, 2005 at 07:23 AM |
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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!
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Baja Wes
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| posted on October 15th, 2005 at 10:55 AM |
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| Quote: | Originally
posted by ricola
Wes, what program did you use to get that? I'd be interested in running a couple of ideas through it...
Rich
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It's CFX, related to ANSYS 10. The licence for both is over $50,000. If you draw the geometry of your idea I could probably do the run for you.
Drawing the thing is the slow part.
What I drew was actually 3D, but I only posted the 2D screen shot. I have the gearbox modelled (roughly) and engine varies in height to roughly model
a boxer engine. I'll try to add a scoop and show some more stuff next week if I get a chance.
I should have changed the scale on the side. It is showing 0 to 44.59m/s which is 0 to 160kph. The red is the 160kph, the yellow is 120kph, the lime
green is about 100kph, and the green is 80kph.
So on the left I set the air velocity to 100kph (the lime green). The air is seperating from the rear window area and causing a large low pressure
behind the car. This is pulling the air under the car faster than 100kph (mainly 120kph). Under the sump is the smallest area so this is where it hits
the highest velocity of 160 or so kph. All pretty bad for aerodynamics.
Some air is going up through the gearbox area, hitting the front face of the engine and making it's way over the top. But in the radiator area the
air flow is much slower, around 40kph (cyan). You can see dead pockets of flow behind the axles and torsion bars (blue). My car has even more of these
because it also has trailing arms causing dead pockets.
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boof2332
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| posted on October 15th, 2005 at 05:43 PM |
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Rueb has the intercoolers in the tail.
Matt
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VDubya
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| posted on October 15th, 2005 at 06:01 PM |
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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. |
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jakjones
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| posted on October 16th, 2005 at 07:31 AM |
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| Quote: | Originally
posted by VDubya
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
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Ha Ha ha ;
Brad and wes the VW legends
Great Post VDubya
are y guys having a lovers tiff ??
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Baja Wes
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| posted on October 16th, 2005 at 08:39 AM |
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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.
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jvl054
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| posted on October 16th, 2005 at 10:55 AM |
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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
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Baja Wes
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| posted on October 16th, 2005 at 10:59 AM |
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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.
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jvl054
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| posted on October 16th, 2005 at 11:18 AM |
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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
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