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Brian Mathe
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Joined: May 30, 2004
Posts: 168
Location: Delaware
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 Posted: Sun Jul 08, 2012 3:23 pm Post subject: |
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Very good point.
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cdennisg
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Joined: November 02, 2004
Posts: 20948
Location: Sandpoint, ID
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| Posted: Sun Jul 08, 2012 1:53 pm Post subject: |
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| papercutt wrote: |
| I will have to dig up my old Gene Berg articles but I do remember him publishing an article about temps in the engine bay of a bus with windows open/closed, deck lid on/off. If I remember correctly, he advised to cut a small section out behind the license plate. It would not be visible but allowed some air flow out. I think it would help. Like when you drive with just one window down, if you crack the back one, the air flows much smoother. |
the difference would be that in the engine compartment, there is already air outflow via the cooling fan and, in larger engines, dual carbs sucking way more air than a stock engine. I would bet that any opening to the rear of the compartment will only suck air in, not allow air to escape.
I like the idea of a duct that runs from down near the frame to the front tin near the starter. It brings fresh air from below the bus right into the intake area of the cooling fan. I did this on a 1776 in a 57 bus and though I had no real gauges, the dip stick test told me it was better than without the extra air. Plus, it was free.
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Last edited by cdennisg on Sun Jul 08, 2012 4:02 pm; edited 2 times in total |
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Brian Mathe
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Joined: May 30, 2004
Posts: 168
Location: Delaware
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| Posted: Sun Jul 08, 2012 12:41 pm Post subject: |
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I will have to dig up my old Gene Berg articles but I do remember him publishing an article about temps in the engine bay of a bus with windows open/closed, deck lid on/off. If I remember correctly, he advised to cut a small section out behind the license plate. It would not be visible but allowed some air flow out. I think it would help. Like when you drive with just one window down, if you crack the back one, the air flows much smoother.
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flemcadiddlehopper
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Joined: December 05, 2011
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Location: Kelowna, BC. Canada.
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| Posted: Sun Jul 08, 2012 8:54 am Post subject: |
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This will make me sound like a dick, but.....I bet Jake has data on a bag being sucked into the cooling fan and covering the fins of 2 cylinders and measurements of the differences between them.....But, it on a Ghia.
Gordo. |
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pyrOman
Fire Master
Joined: July 21, 2003
Posts: 12564
Location: Over 2002 posts deleted!
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| Posted: Sun Jul 01, 2012 5:33 am Post subject: |
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Not starting another thread but...
Chances are "good" that an open engine lid (or none at all) will allow all sorts of road debris including the ever present pastic bag and/or floating newspaper to get sucked into the engine compartment and thus the cooling fan itself. 
True or false? 
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Jeff Power
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Joined: October 13, 2004
Posts: 1170
Location: with any luck, in my garage building bass guitars.
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| Posted: Sat Jun 30, 2012 6:44 pm Post subject: |
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Closed, driving around with the decklid open just looks dumb like when you forget to close the fuel filler door. 
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jtauxe 
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Joined: September 30, 2004
Posts: 5976
Location: Los Alamos, New Mexico, USA
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| Posted: Sat Jun 30, 2012 5:33 pm Post subject: |
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False.
| Campy wrote: |
| Regarding leaving the engine door open, hot air is blown out from the rear of the engine (cylinder heads and cylinders) and some of it would go into the engine compartment. |
Exactly. Drive with your door closed the way VW intended. You don't want to be sucking in hot air coming off the bottom of your engine.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sat Jun 30, 2012 4:30 pm Post subject: |
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| dawerks wrote: |
| 1000 miles in one day in a bug! Awesome!!. |
Yep Chicago to Denver in one day.. All we did was stop to take a leak and fuel up.
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KombiMadness
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Joined: December 09, 2011
Posts: 388
Location: Sunshine Coast, Australia
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| Posted: Sat Jun 30, 2012 3:35 pm Post subject: |
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| cru62 wrote: |
| plane_ben wrote: |
| The splitties vents were low, below the belt line where laminar flow is consistant and strong you don't need scoops. |
It is difficult to change the direction of air in laminar flow. It either needs to be physically redirected (i.e. scoops in this case) or by pressure differential. Since it is so difficult it is possible that the laminar air rushing by on the outside of the vents could draw out air from the engine compartment by a venturi effect. The leaks in the sealing tins, etc. will be accentuated in this case, drawing in hot air instead of cool air.
As far as the dead zone is concerned, I did not mean that the air in it was still. The air flowing over, under and around a bus at speed will trap a low pressure "bubble" of "dirty" air which just stays in the aerodynamic shadow of the vehicle.
As the displacement of the VW engines increased in buses, the fan size (thickness) and vent area both increased. At the end of production the displacement of bug engines and the area of the vents were approximately equal to what they were in the late 60's. Buses, however, increased the vent area as the displacement increased. The reason that the scoops are high on the later buses is primarily due to the the cleaner air being up high. Just look at all the contraptions VW tried in various areas of the globe to pick up clean air. Trucks had the absolute worst location for the stock vents. AND they had one less vent on top of it. |
Sound good points raised by cru62 regarding aerodynamics. However, the air flowing off the trailing surface doesn't just sit dead or just stay there, it actually flows forward.
I'm not getting into the debate raised by the initial thread poster but I will point out some aerodynamic constants about any object with fast flowing air moving around it or a fast moving object moving through (still) air - same effect....
Especially if the object is squared off or slightly rounded off at the back end (most cars), the laminar air flowing off the back doesn't just hang around or just stay at the back of the object (car), it actually flows forward in a series of eddies called vortices. You have all observed this watching water in a creek flowing past a rock and is why white water rafters sometimes get trapped downstream of big rocks and you all learned pretty quickly when you first started driving that if you left the tailgate open in your station wagon, you got exhaust gasses 'sucked' into the car....
The oil mist on the back of the bus alluded to by cru62 is also there because of this effect.
Aerodynamics regarding airflow and pressure differentials can get complicated but the above is a constant for any 'blunt' object with air flowing around it. So an open engine lid will have some air flowing into it from behind the bus. If this air is coming off a hot engine & exhaust from underneath the bus..... well, I'll let you draw your own conclusions. 
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dawerks
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| Posted: Sat Jun 30, 2012 12:36 pm Post subject: |
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1000 miles in one day in a bug! Awesome!! What is 'test lube #1'?
Don't worry about getting an argument, it's the nature of forums. Thank you for posting the information, great!
From the data; CHT's were higher with the decklid propped open (by about 14-18F). I would call it a toss.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sat Jun 30, 2012 12:22 pm Post subject: |
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No use in summarizing.. Just look at the data and come to your own conclusion.. Anything I state will be argued with, anyway.
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pyrOman
Fire Master
Joined: July 21, 2003
Posts: 12564
Location: Over 2002 posts deleted!
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| Posted: Sat Jun 30, 2012 11:51 am Post subject: Re: Data debate |
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| Don66bus wrote: |
Now we are getting some numbers. Plane Ben's measurements say that open lids lead to hotter temps. I browsed about 8 sheets of Jake Raby's data but it is a little overwhelming without access to the spreadsheet, and it is for a bug in any case. Jake, could you shorten that exercise and tell us what you found on your Bug lid open or closed research? Pyroman, I agree that you have great data and what appears to be an admirable engine which does not need any bizarre cooling fixes. Do you have any comparison with the lid open and closed? We can tell it runs great with the lid closed.
Thanks to all. So far I do not see a clear decision on whether an open bus engine lid is an advantage or not in hot conditions.
Don |
How about contributing by installing accurate gauges on your bus and running your very own test with the lid opened and closed? 
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| A man with an experience is never at the mercy of a man with an argument. |
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Don66bus
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Joined: January 11, 2006
Posts: 444
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| Posted: Sat Jun 30, 2012 11:26 am Post subject: Data debate |
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Now we are getting some numbers. Plane Ben's measurements say that open lids lead to hotter temps. I browsed about 8 sheets of Jake Raby's data but it is a little overwhelming without access to the spreadsheet, and it is for a bug in any case. Jake, could you shorten that exercise and tell us what you found on your Bug lid open or closed research? Pyroman, I agree that you have great data and what appears to be an admirable engine which does not need any bizarre cooling fixes. Do you have any comparison with the lid open and closed? We can tell it runs great with the lid closed.
Thanks to all. So far I do not see a clear decision on whether an open bus engine lid is an advantage or not in hot conditions.
Don |
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cru62
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Posts: 4121
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| Posted: Sat Jun 30, 2012 10:22 am Post subject: |
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| plane_ben wrote: |
| The splitties vents were low, below the belt line where laminar flow is consistant and strong you don't need scoops. |
It is difficult to change the direction of air in laminar flow. It either needs to be physically redirected (i.e. scoops in this case) or by pressure differential. Since it is so difficult it is possible that the laminar air rushing by on the outside of the vents could draw out air from the engine compartment by a venturi effect. The leaks in the sealing tins, etc. will be accentuated in this case, drawing in hot air instead of cool air.
As far as the dead zone is concerned, I did not mean that the air in it was still. The air flowing over, under and around a bus at speed will trap a low pressure "bubble" of "dirty" air which just stays in the aerodynamic shadow of the vehicle.
As the displacement of the VW engines increased in buses, the fan size (thickness) and vent area both increased. At the end of production the displacement of bug engines and the area of the vents were approximately equal to what they were in the late 60's. Buses, however, increased the vent area as the displacement increased. The reason that the scoops are high on the later buses is primarily due to the the cleaner air being up high. Just look at all the contraptions VW tried in various areas of the globe to pick up clean air. Trucks had the absolute worst location for the stock vents. AND they had one less vent on top of it.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sat Jun 30, 2012 10:11 am Post subject: |
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No, this was not in a Bus.. The same debate often occurs with beetles. I made 50+ cooling system changes on that trip and woul often test them with open and closed decks to see the effects each way.
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EverettB
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Joined: April 11, 2000
Posts: 71759
Location: Phoenix 602
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| Posted: Sat Jun 30, 2012 10:09 am Post subject: Re: Opinions vs. data |
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| Jake Raby wrote: |
| Don66bus wrote: |
| Looking at this debate, I see a bunch of opinions and guesses, and one person who measured the difference. Has anyone else done those back-to-back tests along the same stretch of highway, with the engine lid open and closed? Right now the evidence from the Altewagen seems pretty good. |
I did over 3,450 miles. Look at the Pilot's notes on each of these data logs to see I the decklid was propped or not and look at the CHT pan OT values for each leg o my run.
Www.aircooledtechnology.com/crosscountry
Race Technology 28 channel data logger power by SPA instrumentation. |
This is informative but that was not a Bus, right?
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plane_ben
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Posts: 349
Location: Tucson, AZ
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| Posted: Sat Jun 30, 2012 9:46 am Post subject: |
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Great info Jake. But I couldn't determine where deck lid was opened or closed. Since that is the debate here. Numbers looked pretty consistant across the states.
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Jake Raby
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Joined: August 23, 2003
Posts: 7433
Location: Aircooled Heaven USA
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| Posted: Sat Jun 30, 2012 9:30 am Post subject: Re: Opinions vs. data |
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| Don66bus wrote: |
| Looking at this debate, I see a bunch of opinions and guesses, and one person who measured the difference. Has anyone else done those back-to-back tests along the same stretch of highway, with the engine lid open and closed? Right now the evidence from the Altewagen seems pretty good. |
I did over 3,450 miles. Look at the Pilot's notes on each of these data logs to see I the decklid was propped or not and look at the CHT pan OT values for each leg o my run.
Www.aircooledtechnology.com/crosscountry
Race Technology 28 channel data logger power by SPA instrumentation.
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Jake Raby
Raby Engine Development
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plane_ben
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Joined: February 27, 2005
Posts: 349
Location: Tucson, AZ
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| Posted: Sat Jun 30, 2012 8:28 am Post subject: |
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I did both a side scoop and open engine deck lid down here in Tucson AZ. I had an oil temp and head temp gauge. Initially my oil temp sender was on the plate for the oil dip stick location for type 3 blocks and my oil temps were very high and inconsistant at different speeds, but head temps remained consistant. Relocated the oil temp sender to a 'T' by the oil pressure port below the distributor gave me better oil temps.
Once that was set, my head temps were higher with the deck lid open by about 8-10 degrees. I had already 86'ed the scoops by this test so I can't vouch for any difference there. I ran the same ten mile run down I-10 at the same speed. Watched and recorded the temps at each mile post both directions. The segment of highway was between Tucson and Benson, AZ and has some steep up hills and down hill sections.
The only time my head temps were even with the deck lid open was when going down hill with little or no engine load.
I say keep the damn thing closed. That's the way VW engineers designed it.
Many will point out that Bay window buses have scoops. Yes they do and look at the location, they are high above the belt line where laminar flow is different and can be affected by an open window. The splitties vents were low, below the belt line where laminar flow is consistant and strong you don't need scoops.
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Snoop Bob
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| Posted: Sat Jun 30, 2012 8:24 am Post subject: Re: Opinions vs. data |
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| pyrOman wrote: |
| Don66bus wrote: |
| Looking at this debate, I see a bunch of opinions and guesses, and one person who measured the difference. Has anyone else done those back-to-back tests along the same stretch of highway, with the engine lid open and closed? Right now the evidence from the Altewagen seems pretty good. |
My experience is not a guess or just opinion and my measurements are done with calibrated instrumentation.  |
I think what he was saying was that most people's posts are opinion based, additionally your base measurement/data was posted but there is no comparison data to open lid (not that you would want or need to test that with your temps.)
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| Put your lips onto the little tit with the hole in it inside and make a good seal. You can suck and blow but with a little resistance. It gets better after it's wet. |
| EverettB wrote: |
| I would be interested in knowing the sizes of the various shafts. |
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