Another rear radiator question

[Wags74]

Sorry to raise this topic again. I've read the other topics that address this but haven't seen anything about my particular question/proposal.

I'm putting a ej22 into a Baja bug and have thought about mounting the radiator to the tube bumper behind the engine. I'd be using the stock radiator with dual fans installed to pull through it.

Let me hear your thoughts on this.

Thanks in advance.

[Ol'fogasaurus]

airflow around things.jpg

This should be a good starting on what the air flow might be around your bug. Probably not perfect especially if you have done some outside mods that could change things.

The best thing is to tape a bunch of pieces of yarn to top, rear and sides of a bug. Have someone video (not the driver of the video car) as the vehicle is driven around at different speeds. I think you might be surprised (and maybe happy... or not) to see just what happens to the yarn at different speeds.

For what it is worth.

Lee

[Wags74]

Thanks for the response Lee. My only issue is that I'm not sure I could interpret the results correctly. I found a website where someone did this and recorded it to test out a spoiler that installed at the top of the back window.

https://www.gerrelt.nl/section-aerodyna ... -tuft-test

Without the spoiler the tufts at the back window laid flat like those on top of the car. This makes me think that the air stays attached to the car until an obstruction (license plate light holder, bumper, etc.) forces it to separate.

I'll try to set up the test just to have the data but i'm leaning towards trying it and keeping an eye on the coolant temp. If it doesn't work out I have a radiator intended for a Civic I can install in the front. Since this is a Baja I'm hoping to avoid running lines under the car.

Thanks again,

Ron

[Ol'fogasaurus]

One thing is that I have never seen the air flow picked up from the sides of the vehicle work well on anything. I've seen many tries on things like street/dune rails. Side mounted radiators even with covers to direct the air into the radiator doesn't seem to work well either. Single or double radiators mounted to the side don't seem to like the airflow they get.

The airflow over the top of the car doesn't "stick "to the top but as the shape goes down the underside of the airflow the vacuum curls some of the airflow under as the pix show.

I have also seen wings and other things designed to change the airflow to come down but there has to be room for the airflow to be directed (somehow) through the radiator. I'm dealing with something similar on my black buggy

scan0002_zps67913d45[1].jpg

This is a very old pix of my black buggy when it was going to be street legal but an incident in my blue buggy stopped that so the toy is now being modified to be an off-road toy. The engine is a Mercury Bobcat V-6 that has been modified for off-road (e.g., a high lift short duration cam used for adding torque to the engine as well as a center pivot 2bbl carb setup) and this shows the mockup for the engine cover... a same problem of flow through the radiator mounted in the rear of the cover was also a potential problem.

Using the yarn pieces taped to the/a like beetle to see just what is going to happen at speeds is really a good thing to do if you can and it should be worth the effort. You can lose a lot of time wondering if something is going to or maybe not and why.

Lee

[Wolfin]

My rail is powered by a Ford V6. I built the engine for fun on the dirt or street since it's street legal. This was my first water cooled build so I went thru a LOT of trial and error in putting mine together. There's really not a lot of info available for that type of conversion because all of them are different but I'll pass along some tips from mine. I used Pressure Differential Pressure Meter to fine tune my airflow,. It has a probe so my passenger was able to just stick it into the wind anywhere and read it. It reads in Positive and Negative pressures. Oh yeah. There are places in the airflow that are a vacuum!

First, make sure your engine is running good. Wrong ignition timing can make it run really hot. Advancing the timing can make it run cooler up to a certain point. Then it goes the other way. I used a new four core radiator that was the biggest that would fit where I needed it to fit. I mounted it "up on her back". Because of air flow dynamics, mine does not work well with a shroud. I get a better draft effect without it. I have four fans on it, two on top that run automatically with a thermostat and two more underneath that I switch on as needed. I added a small scoop to the top of the radiator to catch more air and direct it underneath. I also added a scoop to the top of the windshield to catch the high pressure air blowing up and direct it back to the radiator.

It was loosing to much airflow that should have been flowing from the front windshield air scoop to the radiator so I put in ducts to help it get where I wanted it to go. Plastic is easy to bend and mold around corners but it's expensive so I used ready made ducts from Homy Depoot! Vinyl rain gutter downspouts! Oh Hell yeah! Cheap and easy to work with and perfect for what I needed. It's a Rat Rod Trail Rail so I can do anything I want to as long as it works and stays attached to the car!

[Ol'fogasaurus]

I have a Ford V6 conversion in one of my buggies, but it isn't running yet (seems like 50 years since I started the buggy) due to the cage mounting and a couple of other things that came up.

I'm not sure on my radiator location yet but being in the rear one has to re-think things out. If I rememeber correctly the basics of them are of European design. Good engines, I have mine tied to a 6-rib bus trans.

Opinion: I think I would have set the angle of the radiator a bit more vertical like down where the brake lights are. Take a look at airflow diagrams/pictures

https://www.bing.com/ck/a?!&&p=2c8a9d6a ... MDY3&ntb=1

Hit the "see more" marker as there are some additional pics that might help.

Starting more towards the windshield the airflow is going to flow more like this. redirecting the airflow with scoops may... or may not work as well. Don't try the side mounting of the radiator as it doesn't work well. One bunch I know tried it several different ways including scoops and large scoops. If I remember correctly, they finally mounted it facing forward but up a bit higher than the seat backs are and I think (this happened years ago) they finally got it to work enough to cool the engine.

I have seen others try this but the next time I saw them the radiator was moved and mounted differently.

One thing you can try before you start moving things around is to see just what is going on. What is often done is is to tape cotton strings along the top and sides of the rail and in front of the radiator and maybe behind it also as you could get a merge of the airflow and get a dead spot as the airflow curls back. Then you drive it with someone videoing the air flow.

Lee

[Wolfin]

All you need for airflow thru the radiator, is a high pressure zone on one side and a low pressure zone of the other side. Once you have that working, you can improve the airflow. Mostly, you'll have to do that by experimentation since they're all different. In my case, it used to lay flat on the frame. It ran hot so I lifted the front edge of the radiator a few inches to catch more air. I thought about sliding it more down the back and lifting the front end up almost vertically but decided that would stupid. All of the changes that I've done to it have added up so I expect no problems this summer in Arizona heat.

If I were going to build another one of these, I'd look into mounting the radiator behind the engine by lengthening the tail frame and running a pusher fan off of the engine. Just a thought.

[bad_chopper]

i know this question is from a while ago, but i have an ej22 in my baja. My radiator is mounted to the bumper, i do not have a cooling problem, i do not have the stock radiator though. i have a single core aluminum radiator that was pretty inexpensive about 150 bucks i think and it let me weld the bungs were they needed to go. if you are still interested i can figure out how to load a picture on this forum. not sure how the moderators feal about posting a link to another forum. But if they are okay with it there are some pictures of my build at https://www.thesamba.com/vw/forum/viewt ... c&start=60 this is page 4 it shows a couple pictures of me trying to mock up the stock radiator, then a final installed look of the aluminum radiator. good luck feel free to ask

[Ol'fogasaurus]

What Wolfin said it pretty much true, but you also have to deal with air flow turbulence as it moves around other things which can also affect your airflow at the cooling system.

I mentioned this in another post but if you put your hand in the sink filled with water in it then moved the flat part of your hand (fingers and palm) forward, watch what the water does on the back side of your hand as you move it. You displace the air/water as you move and then the air/water fills up the area your hand was in with usually a swirling action. The same is pretty much true when moving a mass of different sorts in the air.

Until someone points it out people usually see it but don't notice/recognize it.

Very basic but it is what goes on.

For what it is worth.

Lee

[Ol'fogasaurus]

Also there can be turbulence if, for example, the radiator is too close to something that can cause the turbulence with the air rolling off or over it.

It is very interesting to see actual air flow action. The cotton strings (knitting yarn for example) taped to the body or as I said, or on anything standing up or is close to the radiator. Also, air going into scoops can be interesting to see also as the airflow isn't always smooth but turbulent.

Videoing the airflow using the cotton strings is a good idea to see just what is going on with the airflow as you move.

Just remembering things from long ago.

Lee

https://www.bing.com/images/search?view ... ajaxserp=0

[PhillipM]

A lot of the problem with turbulance around scoops is people falling for the old idea of making them wider at the front and narrow at the back to 'force' air in. All it does is stall and spill out around the sides instead.

[Ol'fogasaurus]

A lot of the problem with turbulance around scoops is people falling for the old idea of making them wider at the front and narrow at the back to 'force' air in. All it does is stall and spill out around the sides instead.

Good point PhillipM! Kind of like filling (jamming) a water bottle using a funnel vs. filling a bucket. With aa air scoop facing sideways to airflow is a similar problem.

Lee

[Piledriver]

I once looked into doing an ej22 or wbx with a 911 style fan housing with a pair of motorcycle radiators in the front of the fan housing, with some exit ducting out the trans seal plate... didn't go there but I'd be surprised if it didn't work. Would cost a few hp running that fan but the cooling system would be fully self contained and far away from branches rocks etc.
(was actually looking at it for a 914, zero desire to cut up the car for water cooling)

It would probably get some strange looks on a V6 but it wouldn't shock me if it worked fine.

[Ol'fogasaurus]

Pile, I have seen something like that before and from what I was told it didn't work well. Too much stuff in the area.

scan0002_zps67913d45[1].jpg

This is the black buggy when it was going to be street legal. A modified Mercury Bob Cat (2.9) V-6 tied to a 6 rib. The radiator w/fan was designed to sit low in the back of the lightweight engine cover (it has paper over the frame to check some things.

This was before someone I knew got hurt with a Dune Buggy on the street.

For what it is worth.

Lee

[GaunchLauncherII]

Has been working for me at the back of my car with a K20 and a forklift radiator but I put side vents in my car. Autocross, street driving, and 1/4 mile racing. 2 summers now. With the deck lid on and temps have never been higher than 200 yet. Its always 194 and below using a davis craig electric water pump

https://www.youtube.com/watch?v=HO0Y7q3 ... evinKaiser