Cooling a mid-engine V8 Corvair

regarding the mid-engine V8 Corvair i'm building for the $2000 challenge, i think i've got the radiator inlet and outlet stuff under control.   using the C4 radiator and cooling fans, mounted in the nose of the car, with lower valence cut for air inlet and ducted to radiator core.   will vent radiator outlet either through hood or through fenders aft of front wheel arches.

where i'm looking for help is what to do about engine compartment heat.  in this case, the engine compartment is what used to be the back seat area, separated from driver by and insulated NHRA-compliant firewall and engine cover.   so i'm not trying to manage passenger compartment heat, although that will be a nice benefit.   what i'm trying to do is manage some airflow through the engine compartment to keep things from getting too hot in there.

it's got the old-school cowl vents in the front kick panels.   i'm OK with using the passenger side one for engine compartment airflow, realizing that it is only effective when the car is moving.  

probably goes without saying that I'm OK with cutting holes in the car, as long as the shape does not become a caricature of a Corvair.  OK with flares, splitters, diffusers, etc, but number one desire is to keep as much OE appearance as possible.

GO! 

Make use of the vents at the back/bottom of the rear glass for sure. Open them up as much as possible to allow the heat to rise up/out of the engine bay. Opening the rear bodywork will help too. Dont discount small panel gaps to help let the heat out when you are not moving. Maybe try to add a small radiator fan that just pulls cool air and blows across the intake.

Add heat shields around the exhaust and flow cool air towards them and up/out of the existing vents. In the CART cars we did this with the headers before the turbo (we called them header bags). They had forced air ducts blowing across the primaries inside the bags to keep the radiant heat from everything else.

Louvered decklid...

stafford1500 said:

Louvered decklid...

"decklid" = rear, i ASS-u-me?

AngryCorvair said:

stafford1500 said:

Louvered decklid...

"decklid" = rear, i ASS-u-me?

In cars that arent completely ass backwards this is the case. In the Corvair.....who knows. 

Use a pressure gauge!!! I got a magnehelic gauge on eBay for like $20 that reads differential pressure in scale of 3 inches of water.

Run one line to the engine bay and then the other to various spots on the outside of the engine bay. Have a drive. Note the places where the pressure outside is less than the pressure inside the engine bay (points for "most" less). Cutting holes in those places will actually flow air out of the engine bay because of the pressure differential. (And with pressure differential and sq in of the hole, you can estimate the airflow volume).

I've not done this yet but in a couple weeks I will be thoroughly testing an AMC spirit ;). I'll be using this technique to check radiator airflow, best place to bring engine intake air in, best place to let engine bay hot air escape, best place to let wheel well air escape, etc.

You can borrow my gauge if you want for the cost of shipping, but it'd be cheaper to just buy one!

And if you don't use a gauge, I'm guessing the area between the taillights would be a place where there is a pretty large pressure differential between inside the bay and outside. That and the base of the rear window.

Can you build a scoop in the passenger door to pressurize the engine compartment and an electric fan to help blow the hot air out the back ?

What do they do with all the OEM mid-engine cars?

In reply to nimblemotorsports :

At least for the mr2 Spyder, one side scoop is air intake and the other is engine compartment cooling. Plus a louvered deck lid to let hot air out the top and a perforated grille in the lower bumper. No fans or anything but also not a stonking v8 worth of heat to deal with. 

AngryCorvair said:

stafford1500 said:

Louvered decklid...

"decklid" = rear, i ASS-u-me?

Yes, the rear horizontal panel that most cars would refer to as a TRUNK lid, but you can't do that because your trunk is in the front....

Also decklid because that is what we refer to the trunk lid as on the car I had in front of me a the wind tunnel yesterday.

How about NACA ducts in the rear windows?

So maybe this is a stupid question, but why not a rear mounted radiator with pusher fans, ala of road truck or formula drift car?

In reply to SVreX :

Not sure if it will have windows...

In reply to RevRico :

Weight placement and airflow, more than any other reasons.

In reply to nimblemotorsports :

Yep.  I was thinking about cutting NACA ducts into the quarters.

Would the Corvair club have a copy of the instructions from Crown Mfc that made this conversion in the late 60s ?

In reply to californiamilleghia :

I’ve read the Crown documentation and it does not address airflow through the new engine compartment.

check out Cop cars For a Plastic Rear seat That looks Lots Like The crown Rear seat, I Saw one at auction in a Dodge ,it was more like 2 Buckets, I  Called The local cop car Sales Place ( Precint one ) he Gave me 3 but they look more like something for a bus, Not as Cup Like as I want.

The Back rest could Be Modded into a Huge Front splitter  Hint hint

You might poke around HERE or search for info on Charlie Friend's V8 Corvair.  There might be some details on cooling.

On my Renault 8, I believe the air intake is where a spoiler would be mounted then the air goes through the radiator and exits out the bottom of the engine bay. The engine bay has a lower panel that slopes downward towards the radiator and the air under the car probably helps suck the air out.

How cool do you want to be? 1980s MR2 cool, or late 90s Boxster cool? Boxster engine compartment fan, or '94 Honda Del Sol Radiator fan? Suck air from the top deck through louvers or a grill and blow it out the side. The Porsche parts will cost just enough to bust your budget, you can have the other stuff for the cost of shipping.

In regard to the other thing, I found the cables, but when I was looking for the shifter a mouse jumped out of a box in my shed and bounced off my face. I'm still a little freaked out. The cats are moving in for a few hours and I'm pretty sure I'll find a 6MT shifter eventually. Maybe not until tomorrow.

In reply to slantvaliant :

thanks!  I did get some visuals from the V8 Registry site, but no descriptions of what people did or any A to B data.

AAZCD said:

The Porsche parts will cost just enough to bust your budget, you can have the other stuff for the cost of shipping.

I see how you are, gonna try to break my budget so you'll have a chance at being the fastest mid-V8-swapped Challenger this year.   ;-)

In regard to the other thing, I found the cables, but when I was looking for the shifter a mouse jumped out of a box in my shed and bounced off my face. I'm still a little freaked out. The cats are moving in for a few hours and I'm pretty sure I'll find a 6MT shifter eventually. Maybe not until tomorrow.

You're a good man.  I'm not in a rush, as I don't even have the transaxle yet.  Thanks!

On the original air-cooled 'Vairs, they vented the heat out the bottom, there is a high-pressure area ahead of the transaxle and a low-pressure area behind the engine, because rear-engine.

Look up SuperVair on the Googley-goo and you'll see that he is using a lexan rear window with holes in the top edge and the bottom is vented by virtue of being proud of the sealing channel a good 2", tilted out that is.

Most of the CorV8 cooling stuff is centered on big rads, big fans, and ducting, not enough on sealing the engine compartment and using naturally occurring pressure zones to vent the heat.

The thing about louvers and vents on the decklids in mid-engine Corvairs, is that at-speed most of them appear as-solid to airflow, only working at low-speed and idle conditions to bleed off heat. Same goes for mesh panels in the rear, at-speed all those holes cause a lot of turbulence that effectively makes them a solid panel as far as air-flow is concerned.

I would start with an air-tight firewall and engine cover, then figure out how to use the rear vents under the rear window (originally air intake channels for the flat-6) as a way to pressurize the engine compartment, and either sealing the entire engine compartment floor off into rear-exiting ducting, or through the decklid, again using ducting, making the air flow the way you need it to.

Unfortunately a mid-engine Corvair is nothing like a Boxster or MR2, other than sharing an engine location. Those cars have actually had R&D to develop airflow through the engine compartment.

CorV8's on the other hand, have had 40+ years of trial and effort and not much real success. Most of them are garage-queens, only the guys racing CorV8's have any real practical experience with cooling them.

EDIT 3 YEARS LATER: this post is BS, i'm not running a rear-mount radiator.

Bumping because cooling concept has changed. Mounting radiator in the former engine compartment, with the OE fans in their OE puller configuration. I can make whatever inlet and outlet ducting I need. The lower valance has 2 vent areas, each is 15” wide x 2” tall, for a total 60 sq.in as seen below:

I’m OK with enlarging those vents, probably by making an entirely new panel from stretch-metal. Total panel area is 40” x 6” = 240 sq.in. I’m also marginally OK with venting the decklid. This could be a temporary setup to get through the Challenge, or if it works well it could be permanent.

Feedback please!