Mid-engine Radiator Mounting and Ducting

I'm thinking ahead to radiator mounting for my V6-swapped Lotus Europa. Engine is out back, but there's a front compartment where I'd like to mount the radiator. There is a good sized front inlet in the body. Drawings below of the original Lotus radiator scheme - it's a front inlet, side-mounted, fender well exit. Keep in mine my radiator will be much larger than stock - it's the original from a Toyota Avalon, so it will have to lean at an angle to fit. I will also have the puller fans off the donor car. Also keep in mind the Lotus body has completely flat floor until the engine bay behind the driver. Questions:

• What angle should the radiator lean - top forward, or top rearward?
• Where should the exit go - out the bottom through body floor, or sides through wheel wells like stock? Is pressure lower in a wheel well or near the front of a flat-bottomed car?
• Any other tips?

Goals: minimal changes to visible body - no crazy hood ducts or scoops. 

Lay it down, top forward, air outlet through hood.

In reply to AngryCorvair (Forum Supporter) :

But what if I don't want to cut the hood?

In reply to maschinenbau :

make another one.  TVR Scott can teach you how!

This car is going to be really low, right?  I think the answer in the under vs wheel well debate may involve how much room is between the bottom of the frame and the ground as seen in that front-on shot.

Plenty of front engine cars rely entirely on dumping their hot air under the car, so if that gap is big enough I don't see why you couldn't do the same.

It will be low, but should still have 4-6" of ground clearance under the flat bottom. The bottom tapers upward near the front just a bit. I'm aiming for stock ride height.

I don't see why you couldn't center it and dump the air under in that case.  I forget, do you have a radiator picked already?

How many complex curves in the hood? Could you make another hood without too much effort vs cutting up the stock one?

I think layed forward with some big F50 or GT40 extractor vents in the hood large enough to fit children would be cool. Maybe mock it up with cardboard

Thinking about venting out the bottom.

It seems that directly behind the front spoiler and under the car would be the lowest pressure area relative to the radiator inlet under the bumper. Lower than the current wheel arch exhaust that has the wheel pumping air into the radiator exit, and lower than the top of the hood that has the higher pressure air deflected from the front of the car.

Does this make sense? It would be an easy mod that would allow a larger radiator and preserve the vintage look.

Ron

Considering the existing holes in the frunk and your plan to keep mostly stock bodywork, I would suggest your best option is to lay the radiator in top back and vent the outlets as far back in the front wheel tubs as possible (thru the suspension) or even under the car.

Reasons: 1) the pressures at the front of the tire are higher than behind, 2) using the existing inlet means you can fab simple ductwork that seals to the frunk lid but still lets you see/service the rad when opened (fans on the bottom surface or as part of the duct to the outlet), 3) the nose shape will be adequate to provide flow pressure for the system, 4) outlet directly to the back/bottom/center impacts the chassis, 5) hoses will be aimed down and aft, which is where they need to go, 6) the frunk floor is already in need of work make it require less repair and involve more cutting.

Downsides: 1) bleeding will suck (add at least one high location near the front to bleed the system - X19 style was on top of the radiator, 2) header tank will require some creative plumbing, 3) long runs of tubing will reduce pump effective pressure for the system.

L know this would be a budget hit, and not what you were asking, but square bodied Jeep Cherokees had an unusually short and wide radiator. Maybe available @ Pull-a-Part?

Leaned top backward, exit down under the body seems like a good way to go. I can easily trim a rectangle exit hole in the floor just in front of the frame where it's already torn up. I might try to test fit the radiator soon. That Jeep radiator is a nice shape if I can't fit the Toyota one. Thanks everyone!

maschinenbau said:

Goals: minimal changes to visible body - no crazy hood ducts or scoops. 

I'm not sure we can be friends anymore..

Fieros lean it too forward, air comes in the bottom, there is a air dam, and then air goes right back out the bottom of the car.  It works..  fine.  Fieros don't overheat any more then normal cars in my experience.  

So the Avalon radiator is quite large... It literally only fits top-backward at this very flat angle. Would this be a problem? Might be able to trim some fiberglass to make it more vertical, but it's tight in there.

In reply to maschinenbau :

The way that sits right now, I can't imagine how you will burp it.  There are high points all over with no way to empty them of air.

I see that getting VERY little airflow...

That's incredibly horizontal.  I wouldn't be impossible to get air through it but it would probably violate your body mod goals to get there.  

I can measure my pile of heat exchangers to see what I have available.  They are all castoffs from various projects and therefore leftover and therefore basically $Free.

Keep in mind this is mostly an autocross car, so the fans will be doing most of the work most of the time. But yeah, it's super flat like this. 

There is room behind the engine to mount it vertical, but also lots of exhaust heat.

In reply to maschinenbau :

You really don't want that weight out back if you can help it either. 

Just to keep this topic going separately, here's how a junkyard Jeep Cherokee radiator fits. Good call, wheelsmithy! I think it's perfect.

Do we think a simple fiberglass bulkhead to seal the sides and top of radiator is sufficient? Or should the body inlet be ducted to the radiator? I think I could easily make everything forward of the radiator a sealed compartment, with the body inlet the only way in and the radiator the only way out.

In reply to maschinenbau :

i had a setup like that in my 914, i didn't duct it really just sealed it off. The duct will make it more efficient and cool better but sealing it off will probably work fine. 

Wow! That's an exceptionally nice fit! I may need to change / update my restoration. A couple of observations.

Cutting a little fiberglass would let you move it forward which would then make it reasonable to vent some of the exhaust through the left and right wheel arches. There is a rule of thumb about how big the exhaust vent area should be but I don't recall what it is. 

I would think that simply doing a good job of sealing the front of the trunk lid (soft foam, flexible V strips, etc) would be good enough to seal the top of the intake side. Then you could still use the hood hinge as is. Of course some fiberglass ducting would be needed on the sides of the radiator.

It would make sense to add a couple of separate air ducts to provide cool air to the passenger compartment.

Some folks have found an aero advantage (drag and lift) by ducting air towards the outside edge of the wheel.

Nice concept!

Ron

maschinenbau said:

Just to keep this topic going separately, here's how a junkyard Jeep Cherokee radiator fits. Good call, wheelsmithy! I think it's perfect.

Do we think a simple fiberglass bulkhead to seal the sides and top of radiator is sufficient? Or should the body inlet be ducted to the radiator? I think I could easily make everything forward of the radiator a sealed compartment, with the body inlet the only way in and the radiator the only way out.

 

Yes, you will be good to seal the rad to the existing body owrk and let that be your plenum on the front of the core.