ShopTalk Forums | Aircooled VW Tech & Restoration Help

Double post.

Jadewombat wrote:Very good points, Coolrydes. Again, I've preached this for years and very few seem to take advantage of it, claims mean very little without real numbers. :roll: Any theory doesn't mean too much to mean unless the science actually backs it up. Most guys will post a topic, get 10 replies or whatever and 8 of the response opinions say to do it method A and 2 say method B so original poster winds up going with A most likely, but that doesn't necessarily make it the best method. I built a 1914 that puts out a zillion hp, oh really, did you dyno. that? Bullcrap.

Exactly.

Jadewombat wrote:I just looked at your drawing again, sorry I'm really not trying to nitpick just trying to lend some perspective. The front area of a bug at the rear end of the hood and the base of the front windshield is a high pressure area, VW knew this and took advantage of it by placing vents for the fresh air fan. Next question, if the area on top of the decklid is a high pressure area, you might not get that flow off of the back of the radiator up at out of the stock ghia decklid vents. A high pressure area will not lend itself to "letting out" that hot radiator air, the two will work against each other. If it is a completely negative air pressure area the stock aircooled fan and carb. would have to work very, very hard at speed from the air flow across the decklid wanting to pull that air out of the engine compartment constantly. Look at the attached and share your thoughts.

Jadewombat, first i want to say, thanks for the replies and that from my point of view your thoughts aren't nit picky or unwelcome. I had a business adviser that always used to say "No one is smarter than all of us". I love that saying and I think it fits very well here.

Second, thanks for the links to that thread of GermanLook. You wasted another few hours of my life as I try to learn as much as I can about cars, aerodynamics, etc, etc. (I had never heard of a "manometer" until this thread).. :) I have a very demanding job and this project is my mental escape, so thank again..lol

Now, on to business..

I took a look at Gerrelt's page (referenced from the GL thread) and the video's of the wool string on his bug. From my interpretation, it looks like you have a point on a bug where the addition of a spoiler helps create a low pressure area below the spoiler. We may have the same situation with the Ghia but it's really unknown to us at the moment. (well scratch that, unknown to *me*, Kevin is different animal altogether). As you can probably tell, we are going to test the hell out of this setup and can't really move forward until we get this car running and rolling. But after looking at the excellent work Gerrelt started, some things immediately come to mind that should help, fix or resolve any possible air pressure issues:

1. A spoiler of sorts similar to what Gerrelt built.
2. Possibly sealing the vents on the deck lid and making new ones on the rear portion of the lid or some other lower place.
3. I think people are sleeping a bit on the under body spoiler concept and the amount of pressure it will create but without data points it's moot to discuss right now.

This project is lucky enough to have the eyes of folks like you and others combined with the engineering/mechanical talent of Kevin. So with manometer in hand and brightly colored yarn taped to the car, we'll figure this poop out. lol

Check out this picture and tell me why the deck lid stand off's are installed with the big spoiler? It seems contrary. The spoiler is designed to help create down force by re-directing the air thus creating a lower air pressure area around the deck lid? Is this why the deck lid has standoffs, to help provide more air to the carbs because with the spoiler the air isn't flowing into the deck lid vents? (Actually, now it makes sense!)



If someone wants to make a quick $50, take a *low light* Ghia (let's get the body type right), tape on some white or highly contrasting yarn across the entire back of the car and get some good stable video taken and send it to me. Please pay particular attention to the deck lid vents and the rear lid section. Offer good until 1/19/2013, multiple slots avail, PM for selection. :)

Jadewombat wrote:And before we get too hard any heavy on a tangent about downforce, wings, splitters, etc. ghias do have some pretty impressive lines right out of the box to be able to handle these speeds (although this one has a 911 engine):

http://www.youtube.com/embed/112izsiBJ10?hl=fr&fs=1
http://www.germanlook.net/forums/showthread.php?t=11352

ok.. so reality just sunk in. I'm *never* going to hit 160MPH+ in my Ghia - not gonna happen. The "problem space" just got much smaller and reasonable. All we need to do is cool this puppy while running constantly in the 70-120MPH range. well ok, maybe up to 140MPH.

Another question, what's the fastest documented speed for a vintage bug? Are there any videos available like the Bader or the other Ghia?

I regards to the air movement above the trans. Your right with a firewall and a sealed engine bay there will be no air movement due to the presure build up. The presure build up would cause the air to be pushed under the car and for the area to become hot.

I have a 356 speedster replicar that I recently performed a turbo injected engine swap. Part of the swap was to place the air intake above the trans in a box that allowed the air cleaner to be serviced through a opening behind the rear panel that is in front of and above the trans. I then cut a hole in the panel behind the seat. I made the mistake of driving me speedster without covering that hole or building the box around the air cleaner at first and I found out first hand the amount of presure that is built up in that area, as it blew everything inside the car and hard. There had to be 25 + psi in that area. When I moved the firewall forward and got rid of the factory parcel tray area behind the Ghia's back seat I created an area a lot like my speedster used to have, however now with out the fire wall the air can excape through the decklid vents. Also you have to understand on an air cooled sealed engine compartment, you have a huge air pump (the fan) creating a large vacuum at 3000 rpms. Have you ever had your hand near the opening on the back of a fan shround while the engine was turning at 3000 rpms. If you have you most likely felt like you hand was going to be sucked in along with your arm and full uppped body. Now without that air pump, sealed engine bay, and a negative air presure, I don't think we are going to have any issues. I will do the lite string test once it is done so you guys understand I'm not pulling your legs. Anyone want to place a wager against it working?

noslzzp wrote:
Check out this picture and tell me why the deck lid stand off's are installed with the big spoiler? It seems contrary. The spoiler is designed to help create down force by re-directing the air thus creating a lower air pressure area around the deck lid? Is this why the deck lid has standoffs, to help provide more air to the carbs because with the spoiler the air isn't flowing into the deck lid vents? (Actually, now it makes sense!)

I agree, not really sure why they would put those decklid standoffs, seems like the decklid propped up would be creating more drag and the wing less effective. Seems like a small scoop (dare I say it?) to the vents would work better if the engine is being starved for air. Who knows.

Understanding aero. will really help with your project. It's like getting free hp--sort of. I definitely not an expert, but I have done quite a bit of homework. I autocrossed my '73 super for a year and a half. I was limited to the things I could do hp-wise to the engine, not because of budget but the time involved I simply didn't have to work on it each week and that I didn't want the car to be off the road for extended amounts of time (re-working the heads, etc.) then miss the next race the following month. I tried just about every aero. trick I could find and lightened the car as much as I could to cut through the course and hold my momentum up. But yes, at high(er) speeds aero. is critical as bugs/ghias were simply not designed to go this fast...from the factory anyways. Again, not saying that they can't be made to go very fast :

http://www.youtube.com/watch?v=uKV9PVHw2xA

As for high speed "limits", or where the car get's sketchy I wouldn't worry about it too much at this point, but with that six-cylinder, the Mendeola suspension dialed in, and all of the aero. stuff your'e planning you'll go plenty fast above 100mph and safely. Just make sure you start with the basics, remember, it's the nut that hangs to the steering wheel (driver) that makes or breaks most situations. Make sure you know your car after it gets built very well at the lower speeds first. Really push it to the limits in some autocrosses or track days so you know the weight distribution, turn-in, braking, how the tail feels when you blip it, where the tires will break away cornering, the throttle-on response, etc. before you take it up to progressively higher speeds. Discussion on the subject of high-speeds, handling, and aero.:

http://www.germanlook.net/forums/showth ... 53&page=85

coolrydes wrote:I regards to the air movement above the trans. Your right with a firewall and a sealed engine bay there will be no air movement due to the presure build up. The presure build up would cause the air to be pushed under the car and for the area to become hot.

I made the mistake of driving me speedster without covering that hole or building the box around the air cleaner at first and I found out first hand the amount of presure that is built up in that area, as it blew everything inside the car and hard. There had to be 25 + psi in that area.

There probably is some pressure getting up in that area, but not fully mixing, replacing, and being carried away from the car. Why? Ever smell an exhaust leak? If the exhaust from the engine (behind you) with all of that air flowing above, below, and the sides at speed is not carrying it away, then there's gotta be some re-circulation of this air in the rear of the car coming forward under pressure.

Have you ever had your hand near the opening on the back of a fan shround while the engine was turning at 3000 rpms. If you have you most likely felt like you hand was going to be sucked in along with your arm and full uppped body.

Yes. My friend came to my shop complaining of a noise in the engine. There was a shop rag sitting in the fan shroud. He had kept a rag down in the crux below the pass. taillight down in the body work to check the dipstick every once in a while. No doubt that the stock configuration does work well with a sealed compartment drawing the fresh air down in through the fan shroud, passed the oil cooler, and down to the ground where the air flowing under the car (at speed) easily draws it away down and out under the rear apron.

Now without that air pump, sealed engine bay, and a negative air presure, I don't think we are going to have any issues. I will do the lite string test once it is done so you guys understand I'm not pulling your legs. Anyone want to place a wager against it working?

Again, everything changes from the stock sealed compartment design with regards to airflow now with your Basilari with regards to airflow under the car, up and around the trans. and the engine area. Probably not ideal drawing air from under the car to go across the radiator vs. from the top of the car or sides (like a type 3) as you alluded to with the example of why the stock engine seal is so important, but still not saying it shouldn't work either. I like the sleeper look myself without a lot of hacking to the outside of the car. If you gents could get some manometer readings (colored in brown on the attached) after you get the car going both with and without that lower scoop, and with the decklid vents open and taped off? I will wager you a gentlemen's bet that your scoops on the underside will have to extend up to near the face of the radiator and your design will work better with the vents taped off. How's that sound?

Put in some more work getting ready to move some water....

There was a thread a while back concerning rear mounted radiators etc. Joel provided a link to a thread that a guy actually showed why the rear system would not work.

I'm still considering my idea but it is a bit off. Hope your conversion goes well.
What engine is that?

Why Not ?

Build it, run it. Just keep an eye on your temperatures.
Trial and error will guide you.

Did you check on the last run of Puma’s from brazil, they went water-cooled. Radiators mounted in the back and I have seen a few with a side mount.

Ghia Nut wrote:There was a thread a while back concerning rear mounted radiators etc. Joel provided a link to a thread that a guy actually showed why the rear system would not work.

We'll see.

Ghia Nut wrote:I'm still considering my idea but it is a bit off. Hope your conversion goes well.
What engine is that?

If your car is a Ghia, this is probably a build you want to keep tabs on. We're going to do what we can to make this system work very efficiently. Some changes have been made to the car that people are not fully understanding and at this point there is no real use in explaining it further until we have concrete data, video, a presidential order and a UFO landing on video shown live across the world.

The engine is a flat-6 Subaru EZ30R (variable cam version). Good for over 300HP, naturally aspirated.

noslzzp be honest now...........have you ever thought to turbo this bad boy

panel wrote:noslzzp be honest now...........have you ever thought to turbo this bad boy

Not turbo - supercharged. These 6 cylinder's have been pushed to 800+HP but that is totally ridiculous for my application. Without modding/replacing internals it can be safely pushed (I'm told) to just under 500HP. But, not now my friend and probably no time soon.

Ghia Nut wrote:There was a thread a while back concerning rear mounted radiators etc. Joel provided a link to a thread that a guy actually showed why the rear system would not work.

Sorry I can't remember which one it was, there has been many but Gerrelts is very well detailed on all the methods he tried to make his rear rad setup work.

With regards to a rear rad placement. I have a Bradley GT2 that I converted to mid engine Subaru with the Subaru auto trans. My fuel cell sits above the trans with the rad approx 6 inches behind it. The top of the rad is basically blocked by the fuel cell. The bottom is obstructed by the transmission. I have the 2 stock Subi fans on the back of the rad with approx 5" clearance to the back of the car. There is a fresh air scoop above the fuel cell. I have zero problems keeping it cool. In fact the fans only come on at low speed or idling. Temp holds steady at 220 deg on the highway. 230 idling.


During the build stage. Rad placement.


Mockup of fuel cell.


Fuel cell in place


Hot air outlets, note tail pipes come up beside the rad and exit beside the backup lights.