Hi,

I'm working on a conversion of a 1Z TDI engine into a 78 Bus. I live in Los Angeles which has a relatively hot climate. I'd like to be able to drive in 100*F heat without overheating.

I have an aluminum radiator with a core that's 13"x27" with dual 12" fans.

Ideally, I'd like to mount it without a scoop so I retain ground clearance, easier maintenance, less fabrication.

I realize that most here like Subaru's. The difference with the TDI is that it throws of less waste heat.

I know that I can mount dual radiators without a scoop and be fine. I know that I can run a scoop with the one radiator and be fine. The question is whether I can run the one aluminum radiator without a scoop and be OK?

I'd appreciate any opinions.

Thanks!
Mark

Have a little looksee over at VWKD

http://www.vwkd.co.uk/bb/viewtopic.php?t=16 

Hellbus and EJ71van are running good setups on here, but there's not much info.

At the end of the day, scoop's the way to go. Belly mount - go the full width of the rails on the scoop. It costs you SFA in materials (in comparison) to go full width.

Best design is to go for a blower fan mounted above the rad with the cool air flowing above, hot air going down.

I intend to go flat mount rad next time around, XJ40 size but with a hinged scoop. Why? Because I can't fit the surfboards under when camping

HTH

Mark,

I just got my belly mounted radiator and Subie 2.2L on the road! I test drove it on a day picnic yesterday and am sorting through some cooling questions. I do not have a scoop on mine. It sits between the rails on my Bay and has a slight half inch tilt from front to back (front down). It has two 14" pusher fans and blows air down and out the back (obvioulsy)

We had it modestly loaded with 2 kids, a 110 pound dog and some picnic accessories, drove highways, biways, and gravel roads at elevation with some sustained and steep mountain climbs. Totaled about 150 miles round trip. Ambient day temperature was probably in the low 70*F. Hottest reading I got was 212*F. My fans were kicking on around 177*F, which I think is way too low (hence my cooling questions). So, take it for what its worth. I'll keep more data on the radiator set up withouth a scoop but don't believe its necessary.

You can see more details on my blog if you're interested.

I was after the Bernouli effect with my set up! I figure I can always add a scoop or plenum to the set up later as I get real data on temperatures. I have not blocked the sides along the frame rails or rear support to create the high pressure area...though I am not sure I actually need to as is.

I'll keep driving it and see what my coolant readings say.

Thanks Dan. I've been watching your blog and your Samba thread too. I'm glad the cooling system is working nicely.

I ended up getting a smaller radiator and am most likely going to do a scoop. It's an experiment as the scoop itself is pretty small. 7"x15" opening.

My bet is that it will work as the diesel doesn't create much waste heat. We'll see. I'll post when I have it built and of course when I'm all assembled and running!

177F (80C) is way too low for the fan
Stat's operating temp is 78C (172) - 82C (180)
Fan should kick in around 95 (203), but this is dependant on speed if using ECU control

With my setup I fully sealed the chassis/floor gaps etc so the scoop is pressurised

General_Failure "but I haven't seen anyone do that" - you've not looked very hard

Mark, keep us posted and snap some pics!

Thanks ES for the info on coolant temps. Confirmation is always good.

Quote:

Originally posted by ElusiveStranger 177F (80C) is way too low for the fan Stat's operating temp is 78C (172) - 82C (180) Fan should kick in around 95 (203), but this is dependant on speed if using ECU control With my setup I fully sealed the chassis/floor gaps etc so the scoop is pressurised General_Failure "but I haven't seen anyone do that" - you've not looked very hard

Since I posted about using the scoop, I've changed my mind again #*!&@^

I mocked up the scoop with cardboard and it just looks like there's not a big enough opening to flow enough air. This is all very non-scientific -- i.e. what is "enough"?. The TDI doesn't produce as much waste heat as a gasoline engine, so it MIGHT have been OK.

Previously I had my mockup larger and I was concerned about the loss of ground clearance.

So now, I'm going the route of dual radiators. This is definitely more cooling than what's needed. I' have two new radiators which are replacements for mid 80's VW's. They're 31" long including tanks. I'm going to put two fans only although four would fit. I just know this is already overkill. Once I have something built, I'll post pics.

Part of my logic here is also cost. These radiators can be had for USD$70 each. The dual radiators is a proven setup from others. The cost is probably less than one with the scoop.

Mark

Webwalker: if you've had a pog on VWKD... nothing's changed. You don't say where you're from. Our air temp is approx -5 to + 30C

Scoop's the width of the frame rails, approx 5" below the rails. It's wide, well it'd be rude not too as it's free space. I did run a front spoiler but it severely limits airflow to the rad

I don't understand what a "Hx" is - I'm a Pommie (ps - nice 1st post, I'm in the Avionics industry. We were all stoodents once)

Mine's based on Hellbus's and EJ71's set up but with "hairydymaniccs" theory behind it. COR copied it Hot air *down*, not stagnating above.

Mark - simple rule of thumb... modern cars.... 1/3 rad size into the rad (well it's mostly solid) 1 times the rad outlet (the air's changed density)
Post up some more info on what you're doing. We're not mind readers

what about a coupla naca style ducts on top of the rad with some fans to push thru. the idea being that you start with a smaller opening say 40% of your rad size each then slowly open it out over the top of the rad into a thermo. just make sure your ducting keeps expanding in volume so it keeps drawing as th pressure increases!

Just wondering if anyone has had a radiator with scoop but with suck through thermos with a shroud?
I have heard that these are 15% more efficient than blow through but not sure it this is only when mounted on the front.

I've done some mockups..

I'd like your feedback, but I'm leaning towards building the mountings for two radiators but only using one radiator initially. I'm thinking with the TDI's low waste heat I may be OK with one radiator. One radiator simplifies things -- 1 is less than 2 -- it also means I don't have to deal with the air pocket between the radiators.

So since I'm laying groundwork for two radiators, all of the pics show that..

Here's was an idea. It didn't work because the connection between the two radiators was hitting the clutch cable, e-brake cables under the bus. It would have worked, but the radiator would have been hanging low.

http://realityisreality.com/tdi/cooling/coolingdidnotfit.jpg 

Next, the layout which did fit:

http://realityisreality.com/tdi/cooling/cooling-newlayout.jpg 

I'm going to start with installing radiator#1 only, and add radiator#2 only if needed.

The annoying part is bleeding air from the connection between the two radiators. I'd plan to have a hose barb welded in to the pipe between the two 90 degree hoses. If anyone has any suggestions on how to decrease the vertical distance between the red lines, please let me know!

http://realityisreality.com/tdi/cooling/cooling-radiator-joining.jpg 

Here's the clearance at the rear (about 10")

http://realityisreality.com/tdi/cooling/cooling-clearance-at-rear.jpg 

I plan to tilt the radiator down at the front about 1" to encourage the air-bubbles to exit from the rear. So figure 1" less clearance at front.

http://realityisreality.com/tdi/cooling/cooling-clearance  at front.jpg

Other specs... each radiator is 31" x 12". The core is 27" x 11.5".

I appreciate any comments and suggestions :-)

Mark

I have looked at cooling alot on the vw conversions...bus and bug... just remember it is the creation of a low pressure behind the radiator that draws air throuh.....if air can flow directly behind it there will be no pressure drop and you will get hardly any flow....
That is why modern cars have the black plastic piece from the front bumper to the front suspension...when removed in a wrx the engine bay had more pressure than the air hitting the scoop and flow was backward through the intercooler.

Easy to achieve, just have sides and a flat bottom that goes a couple of inches past the radiator.

Good Luck

Matt

Belly mounted radiators would work well in the city but not much chop out here on rural roads.

I called into the subi joint the other day and it was nice to see another subi powered vw up on the hoist, even if it was australias most roughest EA81 converted kombi with a cooked engine.

I was looking at the radiator thinking no wonder this thing nuked the fins are completely caked with mud.

Till I realised thats the A/C condenser




Granted thats the original dealer fitted A/C and probably never been cleaned since the car was new 36 years ago but slow travelling on dusty roads especiallly with the fans running alot would pull heaps of dirt and crud in.
its a good example of how rads underneath can clog up if you don;t keep your eye on them.

I don't take the title? That's good.

Here's the radiator setup.

These are two radiators which fit 80's VW diesels. They're each 31" x 13". Each core is 26.5" x 12.5". The inlet and outlet are the outside connections.

Mounting is simple. There's a flat steel bar running beneath the radiators at the rear. At the front, a steel bar is also used but it's bent to give the radiator a rake effect - lower at the front. I have long carriage bolts which attach the bars to the bus and which can be used to adjust the height. Even in a worst case scenario, I seem to have over 9" of ground clearance which should be plenty.

The rubber hoses are Gates 21528. The U is made out of aluminum. Naturally it's 1.25" OD and I believe the bend is a 1.8" radius. For the bleed I got parts from McMaster Carr. There's a 90 degree 1/8 NPT and then a 1/8 NPT to 1/4" barb fitting is screwed in with some teflon tape. I had a local welder Heli-Arc the 90 degree fitting into the U tube.

The fans are Chinese from ebay. They're rated 1000 cfm in pull configuration. I reversed the blades and polarity to make them push. With 13.8v across them, they seem to blow nicely. The fans mount with a zip-tie like arrangement through the core. I bought some improved mounts which came with little springs. I think this is useful as the aluminum is going to deform a little and I still want the fans to be snug.

I'm using a temp sensor in one radiator to control a relay which switches the fans on and off. I actually wired in a second relay for two more fans just in-case. I don't think they'll be needed.

There's a lot of seat of the pants science in judging what cooling is enough. I know Greenbuspilot from the Samba who has a water cooled VW engine. He has a copper Chevy truck radiator which is less square inches than my double radiators. Another guy on the Samba has a custom aluminum radiator to cool his Subaru. I have more square inches than him too. Gas puts out more waste heat than diesel so I should have plenty of margin for error.

Two radiators is a PITA because of the need to join them together and deal with the resulting air-pocket. However, I liked the idea of using a readily available cheap radiator. If I need a replacement, I can get one for $100.

I did find an even cheaper radiator. $60 shipped, but it has flattened tubes rather than round ones. I blew through it and it felt more restrictive than the round tube version. Since I'll have more plumbing than stock and double the radiators I wanted to avoid any additional unnecessary restriction so both of these are of the round tube variety.

Pics:




Close-up of the bleeder and U tube:

Pete, I appreciate your suggestions as well as Matt's. I'm trying to understand...

I took a look at Wikipedia on the gurney flap. If I understand correctly. I would make a small flap which extends down from the front of the radiator. I made a sketch which follows. I'm thinking that this flap will block a little of the air flowing under the radiator which will create a low pressure area. Does this look workable?

Thanks for the help!
Mark

You can angle the rad like that. But you want a flat bottom on the box. Then the air rushed along under it. It should hit the flap, create a vacuum and suck the air from out of the radiator.... if I understand it correctly. I've drawn you a pick of the way I understand it.

Imagine the same setup but upside down at the front of the car... and you'd have this car... Flat air intake under the car, flat air exit on top, smooth surface and a gurney flap just before the opening.

Something like this?

black is aerofoil
Green is air flow (tight lines are high pressure, wide spaced lines low)
red is rad
blue is fan.

Yes. That's the literal upside down expression of the race car nose, but the flap doesn't need to be anywhere near that deep. Think about this way, if a NASCAR gurney flap on the boot is big enough at 4" high to hold the back of the car down at 100km/h, then 2" in depth should more than suffice behind the radiator. And the other factor is, the closer to the ground, the better it works IIRC. Also, because the air will stick to the surface, a longer surface under the car (prior to the flap) for the air to run along makes for a bigger disturbance --> then vaccuum when it gets to the gurney flap. ;o)

Guys this is a fascinating thread. But who would have expected such a thing from people who drive bugs with vertical windscreens and kombis that resemble house bricks!

Pete, Vlad:

Thanks so much for the explanation and pictures. I think I'm getting it now.

In my current setup, I did not plan to have a box. There's no sides and no bottom.

I could rework things to have that, but I'll need to stare at the radiators and think about it.

If I were to stay without a bottom and sides, could I achieve some of the effect by adding the flap shown in my sketch?

Thanks again,
Mark

Quote:

Originally posted by markd89

Quote:

Originally posted by markd89 Pete, Vlad: Thanks so much for the explanation and pictures. I think I'm getting it now. In my current setup, I did not plan to have a box. There's no sides and no bottom. I could rework things to have that, but I'll need to stare at the radiators and think about it. If I were to stay without a bottom and sides, could I achieve some of the effect by adding the flap shown in my sketch? Thanks again, Mark