Engine compartment cooling

A raised louver on the engine lid will suck air out of the engine compartment. The air flows over the raised part and low air pressure is created, just like an airplane wing. If there is enough airflow into the engine compartment it could possibly help slightly with cooling, but that is just conjecture on my part. A flat louver (like VW used on the engine compartment lids starting in 1970 or '71 or their convertible lids) will allow air to turn the corner and enter the engine compartment at speed.

Ways to get air into the engine compartment-

1- Leave off the front (front of car: flywheel side) breast plate. A cht gauge would be a good idea here, as a sudden spike in head temps would indicate a platic bag or rag lodged in the fan. Don't forget to extend the exit ducting for the doghouse cooler so the warm air doesn't get reused as cooling/carburetion air.

2- Duct cool air from under the car through a hole in the right side of the front breast plate (or firewall above it).

3- A hole in the firewall opposite the fan intake hole.

4- Holes in the engine compartment side panels. For those worried about dust entering, K&N makes flat panel air filters-

#33-2238- 5.188"x4.438"x.625"

#YA-1602-U- 5.438"x4.313"x.688"

#33-2633- 6.375"x4.625"x.938"

#33-2709- 5.75"x5.75"x.875"

#KA-0009- 5.75"x5.25"x.688"

These are just a few that I found on their website. K&N also has 4 round flat filters from 9.625" to 10.25" and 1.5" thick, which could be used for the access hole in front of the fan intake, should dust entering from there be a concern.

Any other ideas? 

I've fabricated two brackets to hold open my engine hood 4 inches.  It takes me less than two minutes to unbolt the brackets so I can close the hood. 

I don't particularly like the look, but it sure does decrease the temperature in my engine compartment.

When I stop the car while on a hot day, after driving on the highway with the engine hood closed, I can't rest my hand on the shroud, air cleaners, alternator, etc.

If I do the same drive with the hood popped, I can rest my hand on the shroud and air cleaners-the alternator is cooler, but still pretty warm.

Interestingly enough, the oil and head temperatures stay the same (hood open or closed).

I was planning on installing an actuator for the hood, but when I added up the cost for all the needed parts it came to $250.  For now I keep on using my free brackets that I fabricated from bits in my shop.

Maynard, very cool (no pun intended)

It baffles me though that drastically reducing the engine compartment heat doesn't also affect the cylinder head temperature?

Maybe cracking the lid just induces an air flow that evacuates the upper engine compartment heat, while the heads are caught in a swirling, circulating vortex of heated air...much as a plunging waterfall creates a 'trapping' vortex at its base.

What if venting portholes at #1 and #3 cylinders from the wheel wells at a level just above the spark plugs would break up that vortex and cool the heads?  

I think Gilligan has flipped his lid

I liked the side vents that were on DrClock's Red TX speedster (#26?) - maybe he can post the picture for us.  Not sure if he ducted those vents but they were just ahead of the front rear wheels.

The primary function of the air in the engine compartment is to feed the intake and cooling systems. I suppose more air over the outside of the engine sheetmetal would remove some radiated heat and lower the temp of the intake air a little, but I think you'll have the most success by directing more air into the fan intake. The majority of the cooling happens in the area between the cylinders/heads and the engine tin, so I think it would take a huge drop in ambient air temp to show an appreciable difference.

 Dual carbs draw a lot of air, and unless you provide more air intake into the engine compartment they can "rob" air from the cooling fan, and this can cause a negative air pressure situation in the engine bay, and overheating. This is why I talked about getting more air into the engine compartment in my post above. Driving with the engine lid open at highway speeds allows the fan and carbs to draw more air, cooling the motor more efficiently (but does look a little goofy). There can be as much as 2psi difference between the air going through the cooling sheetmetal and the airflow under the car at freeway speeds and this is why the bottom "sled tins" are so important; they introduce the spent cooling air into the under car airflow efficiently.

Introducing more air intake from the engine compartment side walls will have measuable effect on cooling, but not for the reason you've suggested; it allows the carbs to draw more air and function properly without taking it from the fan.

I've mentioned this before but it bears bringing up again; if your car runs "fine" around town but has cooling issues at highway speeds in hotter weather (and you haven't provided more air intake to the engine compartment), do an easy air pressure test. Buy enough clear aquarium air tubing (the small stuff; it's not expensive and you may even find it cheaper at a hardware store) to go from the engine compartment to the passenger seat, fix one end to the fan shroud about where the coil normally sits, and have a friend sit in the passenger seat with the other end in a glass of water. With the car parked but the motor running, note the level of the water in the tube. There shouldn't be much of a rise; without the low pressure area around the back of the car created at driving speeds I would imagine air intake would be sufficient. If it's not, open the engine lid and note what happens. Drive in traffic, keeping track of what happens, and then hit the highway. If at higher speeds the water is rising in the tube, you have a negative pressure situation in the engine compartment and the cooling and intake systems are fighting for air.

Make sure all the engine cooling tin (bottom sled pieces and heater boxes or industrial tins and the back small pieces that fit below the cylinder tins) is in place and fits fairly well. With any sort of hot rodded motor you will have cooling problems on the highway with out the sled tin assemblies. Without them the spent cooling air comes straight down from the motor and hits the under car air layer at 90 degrees and can't join the airstream efficiently, and this reduces the cooling air volume over the heads. Make sure the rear engine compartment seal works so hot air from the exhaust isn't entering and the spark plug seals are there and fit properly; Gene Berg documented a 10 degree temperature increase from just one rip in the rear seal and the same from an absent plug seal.

If you're still having temperature issues at highway speeds then introduce more air into the engine compartment. Do the aquarium tube test again and note how much lower the water level is in the tube. You'll know there is enough air intake when driving with the engine lid ajar has no effect. If after all this you sometimes have oil temp issues in hot weather, now is the time to add an oil cooler. And to truly know what's going on, gauges (cht as well as oil temp) are invaluable. If at the beginning all one did was note the high oil temps and throw on an extra cooler, without the cht gauge (and the sender under a spark plug; mounting it to a fin or the sensor boss doesn't give accurate readings) the heads could be happily cooking themselves to an early death ( probably somewhere most inconvenient; I'm thinking in the middle of nowhere on a long trip) while you don't understand what's happening because the oil temps were always reasonable...  

When you think of what we do with these little motors, getting 2, 3, and even 4 times the hp out of them and then expecting them to cool and live like stockers, they're pretty amazing! 

My apologies for the long post; if this helps one person better understand VW motors...

My oil temperature usually sits around the 180/190 mark (I have an external oil cooler/fan-which comes on a 180 degrees), but the temperature does start to creep up when cruising at 3900/4000 (75 mph).

I'm seriously considering pulling the engine and tranny this winter to have a 3.44 r&p installed.

Terry, your prop to keep the engine hood open looks great.  While mine takes two minutes to set up I bet yours only takes a few seconds.

Ron

Al:  AWESOME post!  

It also bears consideration to have a fan inlet scoop as Bill Drayer has on his car.  It scoops air from the under body air flow and runs through a 5" or 6" diameter tube right into the fan inlet.  I always thought that made some sense.

For those of you still considering a way to hold your engine cover open, you might consider a power window actuator.  There are two types:  One is a lever-action job used in GM and Jeep vehicles, while the other has a coiled cable running through a tube to the window frame.  I was playing with the latter for Pearl (I think it came from a Toyota) but never completed it.  The business end of the actuator cable had a ball and socket arrangement that made it really easy to attach to the underside of the cover and, depending on where it was placed it had the strength to hold the cover up into the upper body airstream.  You could be really cool and have a bellows on it like a 911!!

Al, "AWESOME POST" says it all!!

You've taken some of the 'steepness' out of my long climb up the learning curve. Many thanks.

As for "looking goofy"...when the vented lid is noticed, they'll take a second admirering look at your roadster and naturally assumed that you know what you're doing !!

Looking Goofy?...I think it's neat. Just for kicks I'd be tempted to have a couple of stuffed gloves reaching out of the lid...but that's just the practical joker in me. (It's something Vinny would do too!!)

Since we're talking about engine cooling and the proper sheet metal, how many of you are missing these two important pieces?

http://vwparts.aircooled.net/S...earch=Rear+deflector

The rear deflector plates mount on either side of the pulley tin under the breast plate. According to John Connelly they are vital in directing air to # 2 & 4 cylinders.

They also tie the breast plate to the cylinder tin.

These pices were a missing from my JPS when I picked it up new. 

My engine goes back in Penny on Saturday. With the addition of these two vital pieces I'm anxious to see if there's an improvement in cooling.

Ron, thanks for the compliment. My hood prop isn't fancy but it's functional and, yeah, it only takes a couple seconds to lock into place.

Thanks guys, I'm glad it was worth the time it took to put together. Ron, you're right; cruising at 4000rpm with a modified motor, especially one that puts out 2 or more times the hp of a stocker in summer heat is hard to do. Have you checked into your air pressure situation in your engine compartment? I'm just in Burnaby, maybe I can give you a hand...

Gordon- that's what I've been thinking, a scoop and ducted air to a hole in the firewall directly in front of the fan intake. Are there pics of Bill's set up? TP- those are the "the back small pieces that fit below the cylinder tins" I was talking about. They get left off way too often, and as all the tin pieces, are there for a reason. Thanks for posting the link to the pics.

And Carl, glad you got something out of it.  

For those of you who really, really want to ride around with your engine cover open, I've seen a lot of these devices on street rods lately, they are electronically operated, can withstand the pressure on the hood in the car's slipstream (i.e., they'll stay open when half way) AND, best of all, are fully programmable so you can have 3 positions:  fully closed, fully open and anywhere in between that you set (it has a three-button controller) so your cover could rise to horizontal, just like it's big brothers, the 911's.

Look here:  

http://www.carolinacustom.com/.../trunk_lift_page.jsp

Terry, I got motivated after looking at your simple hood prop bracket.  I opened the hole in my bracket on one side so I can now hook or unhook my bracket by just loosening the bolt.  Next step is to buy a metric wing nut so won't need any tools.

Gordon, I have considered purchasing an actuator.  I even fabricated a bracket to hold it in place.  I ended up not ordering one because the actuator, end pieces, and switch was going to cost me around $250. 

I still may go that route, since I have the wiring in place.  It would be nice to drive around town with the hood down and be able to raise the hood 4 inches with a flick of a switch when I hit cruising speeds of 65+ mph.

Al, do you frequently post on SAMBA? (user name ALB).

Ron

Yup, Carolina Custom isn't cheap.  I still think a power window actuator from a GM or Toyota is the way to go.

Al, can't find any pics but it's pretty simple. I just used 4" alum. flex duct from Lowes. I have a CMC with the cut out in front of the fan. Did a baloney cut and pop riveted the duct to the bulk head. Then ran the duct down and around the shock mount to underneath the passenger "B" pillar. I keep an Empi air intake screen over the fan intake at all times and routinely reach behind with a rag to keep it clear of debris the duct may scoop up...particularly in the fall when leaves are dropping. Didn't do any real testing, but I think it helps feed cooler air to the fan.

I don't think the air intake screen will fit dog house fan shrouds.

So, Make one out of 3/8" square opening mesh to fit the fan opening on your dog house shroud.

I did...

I do have mesh on the CMC opening in the "firewall". I just wanted to discourage people from buying the EMPI screen if it won't fit their shrouds.

"Baloney cut"?...What's a baloney cut?

 Out of 80,000 SOC members am I only one who hasn't the foggiest idea of what a baloney cut is?

Ever watch the Three Stooges??  One episode, they took an old car and repainted it to   replicate a police car.  On the door they painted the round police insignia.  To get the round part, they traced around a boloney, hence, the name.

Got'cha, Mike.  Good idea!

Baloney cut sounds like hole saw cut to fit ducting.

http://en.wikipedia.org/wiki/Hole_saw

(step 3 - somewhat illustrative image)

Yes Ron, that's me. Al

A baloney cut is a mitered or angled cut. Many Harleys have "baloney cut" pipes.

There wasn't enough room to run the air duct straight into the fan opening, so I baloney cut it at an angle to fit in front of the opening in the bulkhead.

WildBill, are you describing an oval cut in the firewall, (perhaps using a reciprical saw?) and an angled cut to the ducting tube also?

If so, how did you secure the tube to the firewall?

The CMC body has the opening molded into it. There is a lip on the front side of the opening to which I pop riveted the duct to.