More air, please

Hello Ron:

 

I am contimplating this same fix.  I believe that Kirk at Vintage is making all his current cars with a 6-8 inch firewall opening.  You can look at some of the Vintage cars that Troy has advertised and see from the engine compartment pictures the relative size and location.  I was at Kirks shop two weeks ago to see if he is doing anything else, and he only installs the wide mesh screen acoss the opening and does not do any ducting upstream.

 

Grant

I did, Ron.

 

Here's a brief description from a thread not too long ago:

 

https://www.speedsterowners.com...179#4951634960843179

Ron, on my first 1911cc Type 4 install my mechanic recommended we drill a hole here. It seemed to work well, my engine ran super cool.

Terry, why did you install a bilge blower?  Was the main purpose of routing the hose from the front of the car to get 'clean' air?

 

Grant, so Kirk thinks that just the hole is enough to add to the engine compartment's air flow?

 

Rick, yours is just a hole, right?

Yup, mine was a meager hole to let the air in. Nuttin' special there.

take a close look at the factory deck lid, you will see two or three holes above the grill on the inside, the factory found this out early, i cut these in mine and whe the engine is ideling it will suck a piece of tissue on the grille, thats all you need. bill

As for the decklid (I forgot), this photo shows the large hole cut for my 911 shroud and the other hole marked with the "x" was cut for my first upright shroud. Sounds similar to what Bill mentions above.

Air can also enter around the engine lid if you use 4 rubber button spacers --- vs the continuous foam gasket (recommended in the FF/CMC build manual).  Guess its like winterizing a house - an 1/8" crack is like having a brick removed.

 

I think the bilge pump is to move air when sitting still and "prime" the flow once moving??? For a long run probably a good idea.  

Ron, I live in a rural area off a long gravel/dirt road so I felt that air coming from the front of the car would be cleaner. It's cooler as well. The blower was to help force more air into the engine bay. I underestimated the power of the fan, as there seems to be no need for the blower. The setup works quite well and I'm thinking about running the system down the passenger side to increase the amount of available clean air.

 

For additional cooling I cut the "bump" out of the decklid and installed two rows of louvers, very similar to what's under the twin grills on a C decklid.

Buckwheat (and anyone else)- Remember that the air requirements for the engine at speed (3-4 times more air and having to enter the engine compartment at freeway speeds and higher) is much different than at standing still and idling or running around town. Someone on the Samba once calculated/guesstimated? that the air intake vents below the back window in a beetle at about 30 sq. inches and the vents in the decklid another 30; iIrc, my older intermeccanica doesn't have half the first amount. And yes, I've measured it. VW put air intake vents in the deck lid as the air requirements increased; 2 sets in 1970 when engine size increased to 1600cc's and 2 more in '72 when they realized there needed to be more air for the new doghouse fan/shroud (and they were starting to tune the motor to run hotter for better emissions).

 

I've said this before but I will repeat myself because not enough people understand it's importance; lack of air intake capability is the major cause of a signifigant number of people's overheating problems (in the aircooled VW world as well as VW based replicars). The doghouse fan draws 1250 to almost 1500 cfm (200-250 cfm MORE air than the earlier fan) at 4000 rpms. Couple this with dual carbs that use at least twice the 124cfm a stock 34-3 solex flows, remembering that a 2200-2400 cc motor with 48mm carburetors can draw upwards of 1,000 cfm at full throttle (even a pair of 40mm Webers and Dels are capable of 700-800 cfm, depending on venturi size), and you can see the need to increase the air intake capability of these cars. 

 

A simple air pressure test can be done with clear aquarium air tubing (I got a 20 ft. piece at a local pet shop for $3). Affix one end to the shroud (near the coil works) and have your helper sit in the passenger seat with the other end in a glass of water. Sitting still and at idle, note the water level in the tube; now open the engine lid (this is where the extra tubing comes in handy). If there is much of a difference I'm guessing the results later are going to surprise you!

 

Drive around town a little bit with your partner watching what happens to the water level in the tube in different conditions; different steady rpms at different speeds and accelerating. Now see what's happening out on the highway. Water rising up the tube means the motor is using more air than the engine compartment can supply.

 

A car may seem to run fine around town (even when getting on it constantly), yet run hotter on the highway; this can come from the fact that at lower speeds air can turn the corner into the engine compartment through the decklid easily, yet the air pressure (and turbulance?) outside the engine lid at highway speeds is different, not allowing the motor to feed itself. This is why air intake from the front of the engine compartment is beneficial; it allows the motor to stay reasonably cool on that high speed romp on the freeway or those twisting canyon roads!

 

A couple more points: adding an extra cooler before figuring out the air intake situation in the engine compartment could be a disaster (Gene Berg called this putting a bandaid on your elbow for a hurt on your knee, or not fixing the problem); the result will certainly be cooler oil but the cause of that oil getting too hot hasn't been addressed. You could drive away happily into the sunset, only to have the motor die from overcooked heads; it won't happen anywhere convenient and likely the heads (and maybe the pistons and cylinders, bearings...) will need to be replaced. When dealing with big, hot rodded motors, oil temp and cylinder head temp gauges (while not essential) are invaluable, as they let you know exactly what's going on. 

 

Ron.

This is exactly what I had my mechanic do on my car.  He did it all with flexible dryer hose and plastic for less than $20 and it works great at freeway speeds where I was having problems.  He was going to do a second vent/scoop on the left side of the engine compartment if the single one wasn't enough, but it was.

Troy

Hello Ron:

 

Yes, according to Kirk he is only putting the hole through the firewall with no additional ducting.  I don't think that Kirk is doing any high-level CFM calculations.  I think its more of a gut feel for him, as he told me that the firewall hole isn't needed on stock 1600's.  Maybe this is because he doesn't seal the engine between the firewall and engine firewall tin, and relys on that 1-2 inch gap to provide extra air.

 

I spent a good part of the day yesterdat sealing that gap between the firewall and the engine firewall tin to prevent hot air from recirculating back into the engine compartment during highway use.  I left a 6 inch section open right on top, thinking that this is far enough away from the exhaust and heat exchangers to take advantage of any extra air coming up from under the car.

 

 

 

Here are some pics below.  The first showing Kirk's hole size and placement through the firewall.  The second and third are my firewall seals installed yesterday.

 

 

 

 

 

Nice job!

 

 

Here's a general question related to cooling - Do those alternator/generator pulley fans draw any more air in or do they just cool the alternator or generator?

 

 

 

 

 

The 2" between the bulkhead and the motor allows for clean cool air to enter the engine bay, then exits through the deck lid grill scavaging engine heated air.....  the add'l fan intake air hole does some but probably isn't that significant.  ~Alan

Terry, I'm not sure what you're talking about here.  I take it the blower is the bilge blower, but what fan are you talking about?

 

Alan, when you leave off the tin between the engine and the bulkhead do you extend the oil cooler vent tin, so hot air exiting the cooler can't come back up into the engine bay?

thanks

Ron

Ron, the doghouse fan.

Ron: for the best results, you should.

" ....do you extend the oil cooler vent tin, so hot air exiting the cooler can't come back up into the engine bay"

 

 There is enough clean air exchange in the engine compartment, I haven't had heat issue in thirty speedster builds.

Al, which 'should' should I do-cut a hole in the bulkhead or leave out he bulkhead tin?

 

I put the IM up on my scissor hoist today to have a look at the area behind the bulkhead.  Free space is definitely at a premium.  With the fuel injection lines, fuel injection regulator, torque bar parts, and heater tubes there isn't room to add much of anything.

I went to our local Home Depot (not sure if you have Home Depot in the US) to buy a Demel tool and price out a six inch hole saw.  Holy Crappola, they wanted $65 for one six inch hole saw!!!

I passed on the hole saw, but bought the Demel.  Looks like I'll be cutting come fiberglass behind the front bumper real soon.

I do both / leave the 1-1/2" - 2" gap at the bulkhead and cut the fan air intake opening

There is a bit for the Dremel tool that is normally used for removing grout from between tiles.  It looks like a drill with really shallow flutes.  It is especially effective with fiberglass.  As an alternative, they also offer a small rasp that works well, but has a tendency to burn a bit (not the fiberglass, just the bit) - just run it a little slower and it'll work just fine.

 

Another attachment worth its price is a hole cutting jig that will cut holes from about 3" to 8" using the grout bit or hasp above.  Since you already have the Dremel, at least you can save the $65 for a hole saw.........

 

My Dremel is my most used tool in the shop - apart from the 8" vice, of course.

Gordon, what about the small cutting disk?  That's what I'm considering using.

I want to add a fan to my VS at the firewall hole and add a k&n flat filter . Hot vws had a article where they added filters boxed on the side . Gave filtered air and access to dual carbs .

I don't get the redundancy in filtering the air coming in; the carbs already have air filters on them. I would say a screen mesh on the hole is a good idea to prevent leaves or other debris coming in but filters are overkill, IMHO.

He just wants to keep his engine compartment clean...

Ron O,

 

Whatever cutting tool, or combination of tools, they're going to produce a surprising amount of fine talcum like powder...abrasive non-soluable, and a real health concern for both your lungs and your engine.

 

Wrap and tape your engine like a Christman present! Wear a gauze mask, and vacuum every nook and cranny in the engine bay.

 

 

 

That firewall could be 1/4" thick.  Can't you get a saber saw above the transaxel? Or remove the cooling shroud to provide access room.

 

Harbor Freight has a small $10 air powered body saw that would work too.

 

http://www.harborfreight.com/h...metal-saw-91753.html

Dremel motor tool with a spiral cutter bit.....   Lots of dust however...

If you're cutting fiberglass use safety glasses and a resporator and don't leave an inch of skin exposed or you'll regret it. I say so from experience.

Yes, I'll cover myself from head to foot and wear a full face mask.

Here's how much I cut away from my IM after the fire:

 

 

 

 

Ron wrote:

 

"Gordon, what about the small cutting disk?  That's what I'm considering using."

 

Negatory, good buddy.......

 

If you're trying to cut a hole curve using a flat cutting wheel, you'll always be fighting against the wheel.  Get the Dremel hole cutting tool.  It's an arm that fits the Dremel at one end and has a pin at the other end to fit into a 1/8" hole you drill at the center of the hole you want.  Set it to the proper hole size, use the Dremel router/grout bit, put on your respirator/space suit/bunny slippers and full-face-enclosed helmet and have at it.  You should be done in about a minute.  If you're worried about getting abrasive powder anywhere, just hold a flexible hose from your vacuum cleaner in the same hand as the Dremel and hold the end of the hose close to the bit.  Powder won't be a problem then, and you might not need your respirator/space suit/bunny slippers and full-face-enclosed helmet.

 

To be perfectly honest, I don't have the hole-cutting tool, but always wanted one.  I usually draw the circle where I want it with a pencil and then free-hand the hole with a Dremel and a hasp, but it involves going very slowly or staying inside the line and then, very slowly even more, trimming out til I get to the line.  The hole cutting tool gets it right the first time. 

 

I used a Dremel with a mini-hasp to remove the material for Lane's horn grills and tail lights, clearanced the  firewall above the engine case when we were trying to install the engine (that was free-hand - Lane wasn't watching), buzzed the lip off of the headlight buckets, opened/trimmed a couple of holes in the dash and a bunch of other stuff.  If he was there the whole time he would'a fainted.  You'll find lots of uses for a Dremel and a hasp once you have it.  It goes through 1/4" fiberglass like Buddah!  Sometimes TOO fast.....

 

gn

Ron; I totally forgot about that! Yours has been the best Speedster resurrection ever!

What Dremel tool should I use for cutting a very shallow half-circle on the lower front body, just behind the bumper, to increase airflow to the oil cooler?

 

Ron...before you cut, are you sure you need to ? That's a beautiful car. What calcs have you done ?

Ron - Why not just plumb the "horn" vents over to the oil cooler?

If I cut off some of the fiberglass it won't be much-maybe one inch.  It also won't be very noticeable when the car is on the ground.

Wolfgang, because of the location of the battery box, I had to mount the cooler very close to the front, so I can't use the horn vents.  That would have been a really great idea, had I been able to mount the cooler farther back.

 

Another minor problem I will have is changing how I mount my license plate.  I'll have to mount it much higher, which may look a bit odd. 

 

I think you should try plugging the gaps between the cooler sides and scoop before you start cutting the body. As it is, much of the air that oversize scoop could be grabbing is just flowing around the cooler, not through it.

"What Dremel tool should I use for cutting a very shallow half-circle on the lower front body, just behind the bumper, to increase airflow to the oil cooler?" 

The radius of that curve would be long enough that you could get away with a cut-off wheel on a Dremel, but the angle you must hold it at might be a little uncomfortable, so I might still end up with a rotary mini-rasp set at about "8" for speed and free-hand it against a pre-drawn line.  

Thanks Gordon.  My kit came with an multipurpose bit (#561) that should do the trick.