Interior cooling

[Jim Craik]

Guys,

I have been thinking of ways to get more outside air into the interior of my SPF.

I have seen the window mods, with the helicopter vents and scoops but I'm not to happy with the look or changing the stock window.

I have been looking at the roof vent as a possable avenue. First I though about a small snorkel with a square base that can replace the stock air vent.

I'm now thinking about replacing the square vent plate with a flat piece that hinges at the back, when open it would be at about a 45 degree angle. If I remove the inside water collector it should bring in lots of air, yet when closed would appear mostly stock.

Any thoughts?

 

[Randy V]

I think that if you would hinge it at the front that you'd have better airflow as you'll be pulling heat out of the cabin there. I know you don't like the look of them - but as I recall - they are available in smaller sizes (although not able to find them right now in a search) - You could install helicopter vents in the front corners of the side windows as long as they don't get in the way of the mirrors... I think they would be almost insignificant to the net appearance of the car if mounted up there..
Or possibly some changes to the venting from the front NACA ducts?

 

[Jim Craik]

Randy, thanks for the comments,

I have found that opening the side vents, only makes my car hotter. I think what I get is a low pressure area inside and I can feel the hot air entering from the radiatior area (My car is stock, I have not done any extra sealing of the front bulkhead).

But I'm thinking that a front facing scoop with the side vents open would create a good flow of air and still pressurise the cabin enough to keep out the hot air from the radiatior area.

 

[Rick Muck- Mark IV]

Jim,

Have you opened the "brake ducts" that flank the radiator opening? These will flood the front clip with ambient temp air if you do so. While not "cooled" air, this will dissapate the heated air from the radiator and reduce the temperature difference your AC must make up.

And some time spent sealing the front bulkhead area will help greatly..oh, and some guy makes a seal kit that improves the AC performance by eliminating the hot air entry into the cockpit that happens where the AC air inlet is.

http://www.gt40s.com/forum/superformance-gt40s/30007-spf-gt40-ac-box-seal-kit.html

Hint, hint......

 

[Jim Craik]

Mark IV

Thanks for the info, that makes a lot of sense, I'll open up the brake ducts.

I read the info about the cooling box seal kit, I will order that.

My thinking on the fresh air intake is this. I live at the top of a mountain. It's approximate six miles up hill. On weekends, when I do most of my driving it's a popular drive for amateurs.

It's often a slow ride behind folks at 10-15 mph. I have found that on hot days, I need to turn off the ac to keep the temp from getting too high.

At those times, extra air would be good.

 

[Jack Houpe]

You live in the bay area and complain about the heat?? Try moving to Alaska. Was it not you that said your car is nice and cool without and mods?

 

[Jim Craik]

Gee Jack,

If you read my post again, you will see that I did not complain about the heat.

My issue was driving up hill on a hot day at 10-15 mph, nothing else.

But thanks for the input, very helpful!

 

[Seymour Snerd]

I read the info about the cooling box seal kit, I will order that.

Rick's seal kit does a good job of keeping the A/C system from fighting a losing battle with the radiator.

Another thing to do in that area is seal the air path from the radiator to the hood vents, this gets all the radiator exhaust out of the car altogether and sends all of it up over the roof (where your roof vent idea might just bring it back in if you're unlucky).

There are some other pretty gross sources of heat: the transmission tunnel, and in particular the openings at its rear where the cables, etc., pass through the firewall.

Fundamentally there's a very efficient 300,000 watt heater right behind your head that you're battling, and even a small entry into the cabin is going to be hard to fight. If it were me I would go after all those sources of heat first; they're easy to fix and don't require any invention or aerodynamic luck; just sealing and insulating like you would with your house. Ideally with the A/C on recirc the cabin should be essentially air-tight.

I seem to recall reading that the roof vent is positive pressure at lower speeds but becomes negative at higher speeds (or vice versa). So unless you stick something well up above the boundary layer (how about a Mk II brake snorkel?) you may never be able to make this work.

BTW, if your problem occurs during an uphill crawl at 10-15 mph, no scoop is going to help much. At that speed there's nothing particularly aerodynamic going on.

Regarding the cooling system and any tendency to overheat, I notice a fairly large gap between the lower edge of the radiator and the grill opening. I haven't gone after this yet but my recollection is that a fairly simple shape cut from flat material would fix it. That kind of thing is a classic contributor to poor cooling. Forcing all the air entering the grill opening to actually go through the radiator rather than around it can really help. And it helps both the cooling and the A/C.

And lastly, how are your fans? Do you have the upgraded 5-blade ones?

 

[Seymour Snerd]

If you read my post again, you will see that I did not complain about the heat.

That's OK, I will. I grew up in the South Peninsula and did not enjoy the 90-100 degree summers at all.

 

[Jim Craik]

Alan,

Thanks, good info. I have been looking at that space in front of the radiator, a good seal there would be a great help. If nothing else it would aid greatly in reducing front lift.

Alan, where on the Peninsula did you grow up? I grew up in Menlo Park.

 

[Seymour Snerd]

Alan,

If nothing else it would aid greatly in reducing front lift.

That's exactly what I was thinking.

Also regarding routing the radiator exhaust, here's a picture of how it's done on P1032, a Mk II. That's what I'm going to do (eventually). Maybe the shape of yours would be somehwat different to match up with the hood vents, being a Mk I.

 

[Jim Craik]

Alan,

That's a nice layout, that would work great.

I tried adding to your PM, but I'm using a new Ipad, and I can't figure out how to get to the bottom of the message. (i'm a 20th Century guy).

I was at Menlo summer of 65 and part of year 65, before they kicked me out

My wife was a Menlo College grad and was on the Board of Trustees for some time.

I live on the mountain behind PV in Saratoga, 2.5ac in PV very, very big bucks!

 

[Rick Muck- Mark IV]

Be sure to reduce the heat paths from the engine compartment as best as you can. If your car is LHD, the tunnel for the RHD sill shifter is still there, a nice, open path for heat, noise and critters! Remove your RH seat and look at the clear route these have into your cabin. A good chunk of dense foam stuffed in there will help greatly. And the standard bulkhead window does not do much but keep rocks off your head! Either our glass upgrade bulkhead window kit or some time spent sealing the standard polycarb unit will pay off greatly.

While some of the heat paths may seem small, you are battling a very big source of BTUs and every little bit will help!

We are working on a molded heat/noise insulator that can go under the bulkhead carpet and still look good. Not ready yet, but in the works.

Honestly, the GT40 parts we have developed have been slightly disappointing....we have priced them close to cost just to help GT owners, but sales are not what I would call "brisk". Still, we will offer then until stock is gone.

 

[Mike Christian]

Jim,

If you are stock, can't you just make the NACA ducts functional somehow? I mean get some SCAT tubing and hook them up to a vent eyeball inside (somehow)?

Mike
Ps: thinking about doing the same someday...

 

[Jim Craik]

Mark IV,

Yes, I removed the bulkhead carpet, and added Dynamat for noise, an aluminum backed bubble-wrap for heat. Additionally, I used the 3/4' plexi to replace the bulkhead window, these additions made a huge difference in noise and heat.

I'm just looking for a way to "roll down the window" if you know what I mean.

 

[Jim Craik]

Mike I thought about that to, but most of my AC air comes from the eyeballs and I don't want to effect that.

 

[Scott Calabro]

Funny thing is I totally enjoy the heat, noise and wonderful 60's smell of a GT ... there is almost nothing more I look forward to after a long New England winter.

Isn't this the essence of the GT experience?

A/C.... that is almost as bad as LHD & center shift:laugh:

Seriously though, I just remove my side windows.

It takes 5 minutes.

 

[Mike Drew]

Jim,

Here is a very important point that nobody has yet touched on. Your car is a Superformance with a two-nostril front hood (bonnet). SPF totally screwed up the design of this piece. The originals had a V-shaped center section that ensured that 100% of the air passing through the radiator, exited through the top of the hood.

Check out the photo below. This is from an original GT40 road car; the notch on the right side is to provide clearance for the oil cooler. This view is looking from the perspective of the radiator, back towards the rear of the car:

You can see that the air is well-managed and exits out the top. Now, take a look at your own nose section. It's an engineering disaster! Rather than this V-shaped setup, there is a huge box-shaped section in the center. A substantial percentage of the air that exits the radiator, instead of going through the vents, is instead routed straight back against the front of the passenger compartment portion of the tub! This hot air then finds its way through the various holes, slits and slots and floods the driving compartment.

If you have access to a fiberglass guy, you can modify your hood to copy the design of the original; failing that, Jay Cushman sells a perfect reproduction for $500. Here's a photo of Jay's piece (presumably taken from a race car, hence the lack of the cutout?)

I would think it would be cheaper/easier to modify your existing unit and touch up the paint, rather than starting from scratch, and having to do all the bodywork and paint work etc. (not to mention the initial cost of the new piece).

Before taking steps to introduce cool air into the car, it's definitely worthwhile to eliminate as many sources of hot air as possible!

 

[Jim Craik]

Mike,

Thanks, I knew the first time I saw the hood that it was not right. It looks to me that 20-30% of the air goes out to the wheel wells.

Mike, by the way, I was talking to a friend, he told me about spinning his Big, Red, Steroid filled Pantera right in front of you!

 

[Seymour Snerd]

Seriously though, I just remove my side windows.

It takes 5 minutes.

Good point. And BTW this operation is easier and more "sustainable" if you replace SPF's wood-screws-in-fiberlgass with 3mm hex-socket flathead machine screws in threaded inserts.