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Old 06-19-2017, 12:24 PM   #271 (permalink)
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VW cooling: maintain pressure differential, avoid chrome.

@chopstix:

VW cooling systems, you want to learn about them? Google up "Bob Hoover Sermons" (you are looking for Bob Hoover's "Sermons" files - and not the preacher nor the noted aviator) and anything you can find about "HVX mods" that he did for airplane power plant usage of VW engines. Oh, and his "Tulz" files are good, too - tools he made himself/figured out how to use properly, etc. There's a pdf of most of his "Sermons" around on the 'net, but you can find more by searching around. Huh, his blog is still around: Bob Hoover's Blog He's sadly passed on, but I learned *so much* about VW engines from his posts. Most of what he writes is based on bus usage, plus his airplane stuff. He wanted more power out of the VW engine for climbing up to altitude, so he basically taught himself thermodynamics while reverse-engineering the VW cooling system. His findings: with stock cooling fin area, you can dissipate the waste heat from 40hp continuously so long as the cooling tin is properly set up. Any more hp than that must be intermittent, and the heat goes into heating up the metal and the oil, and then you need to run lower power for a while to dissipate the buildup.

Also very good at story telling for his trips/adventures, and how to build and maintain yourself a good reliable engine (he'd get 100k out of a set of jugs, 200k out of the crankcase/heads).

Cooling basics (and apologies if you know this already): Cooling system depends on a pressure differential between the engine bay and the underside/rear of the vehicle. There's a rubber gasket around the engine tin that seals the engine bay from the underside of the vehicle. What you need to do is make sure that air can get into the engine bay in sufficient quantity, and that it can exit out the bottom, and that the hot air does not get sucked back in. You can create positive pressure in the bay, or negative pressure underneath. Avoid negative pressure in the bay. *Avoid chrome valvecovers and pushrod tubes* (the engine you show has them - avoid!) - it traps heat inside the engine, and both were apparently fitted for artic usage for that very reason. Use stock "accordion" style pushrod covers - they are part of the cooling system. Make sure all of the engine tin is in place - Bob has a lot of notes about bits that are often missing, etc. Paint the fins with a thin coat of flat black for best heat rejection. Beware stroker engines - they spread out the cylinder heads and need properly reworked cooling tin to cool properly - involves cutting the shroud pretty high up around the fan (Type 1) to make sure the "slug" of coolest, densest air from the fan hits the right spot on the cylinder heads.

I really cannot recommend Bob's work too much. Hands down the most informed, readable technical resource for VW aircooled engines I've ever read. Some ranting here and there about "what the cool magazines have that's all wrong" but written in an entertaining style. He even has some mixed praise for John Muir (of "How to keep your Volkswagen Alive, a Manual of Step-by-Step Procedures for the Compleat Idiot" fame) - mostly in the form of only knocking on the few things the guy got wrong and some bad advice in the book. Muir's book is beautiful, too - still my go-to for "how to understand a car".

Sounds like you're gearing up for an interesting project! Have fun!

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Old 06-19-2017, 08:35 PM   #272 (permalink)
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Thanks for the interesting facts. I'll dig into them a bit more as I check things off my list. (I've got a few obligations at present. Then I'll be more seriously looking at building this car.)

On the cooling, I talked with BGW about the Delivery kit and they told me to keep the stock cooling as it simply works the best. Then add a duct(s) in the delivery side wall to force air into the engine cavity. This is basically what you are telling me as well. Its also basically the same as stock with the rear engine cover slots.

So then I asked him about putting the air inlets inside the rear fenders as beetles are known to have a scooping effect from them. (The scooping effect is bad for the cars aero as it causes rear lift.) He claimed that they should work in concept. But there's additional problems to deal with like water/snow splashing the air inlets on a daily driver. But I'm thinking about hotrod louvers in both rear fenders venting into the engine compartment. I'm also thinking about adding a stainless screen on the inside wall of those louvers. That way the scooping effect is utilized for engine cooling, and I wouldn't have to cut on the rear fenders, or add scoops in the Delivery shell. It would keep the exterior as smooth and stock looking as possible. Plus the concept of adding a diffuser would benefit the fender louver vents since the diffuser would further separate the air in the fenders from the air under the car. Or at least that is my initial thoughts.

Oh and I don't like chrome on engines, its too hard to keep clean!

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Old 06-19-2017, 10:37 PM   #273 (permalink)
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Sermons of Bob Hoover is a good mention.

You're not going to get much 'scooping' action inside the wheelwell. Keep in mind that the cooling fan is interposed between the engine bay plenum and the underside. IIRC it's 1500cfm of pumped positive pressure air. Just having an adequately sized opening is all that's needed.

http://justacarguy.blogspot.com/2017...-creation.html





I'd seen this one on thesamba, JACG points to the build thread.

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Old 06-20-2017, 01:50 PM   #274 (permalink)
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It looks so cool, even though it's too low to be a practical daily-driver.
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Old 06-20-2017, 04:42 PM   #275 (permalink)
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I'd want to see someone sitting in it with the bubble top closed before I'd pass judgment as a daily driver. More your speed?

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Old 06-20-2017, 05:26 PM   #276 (permalink)
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I'd want to see someone sitting in it with the bubble top closed before I'd pass judgment as a daily driver. More your speed?
That one is MY STYLE! Except for the beacon light on the roof and the poorly done front bump creation.

I read about the Roth-ian styled bubble top on Samba. He has video of him driving it down the alley behind the shop where he built it. Its a cool project since nobody builds them like that anymore. I would like to hear Moldy Marvin's opinion of the car.

The scooping effect was quoted from numerous posts on the Samba. They make it out to be a big deal. Me, I don't know how big a deal it actually is. But I know that I need a place to add cooling with that shell. So venting through the side panels will do the trick. Thus that is the limit of my concern with the concept.

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Old 06-20-2017, 06:07 PM   #277 (permalink)
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thesamba isn't always authoritative. Ferinstance, I asked Everett Barnes about interest in front wheel skirts and he thought the idea would get shouted down.

The gap between the fenderwell and tire is narrow and full of churn. No guarantee of a positive pressure gradient to the underside. If you cut the vent[s], you could do A-B-A testing.

I liked the solution Harry Bradley suggested in his drawings from the '80s. I know I scanned it but I haven't found it in my albums. Basically he added a 1.5-2" C-bracket on each mounting bolt to hold the stock fender out and then covered the gap with perforated metal mesh. He also had the taillights and turn signals in there as well.

I'll keep looking through my backups.
________

The roof-top light and whatever is going on under the [raised] front bumper made me think 'rural fire department'.

https://www.google.com/search?q=battle+car+beetle
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Old 06-20-2017, 07:26 PM   #278 (permalink)
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This is completely off vw topic, but since you brought up 'rural fire department'. My small town had a 70's era flat front end (cab over) ford fire truck. The details are not important beyond its a town of 100+ people, so buying a new one is completely not going to happen. ~ Nothing I'm about to tell you is exaggerated in ANY way.

So for about 10 years every time someone called the FD the old yellow truck was driven out the door, and everyone in town placed bets on how far they would make it before they had to turn back and cancel their response!
Most of the time the truck made it 2 or 3 blocks then let out a giant poof of black smoke. Then lost all its power, and limped back to the fire house at half walking speed. Every year they spent tax dollars on trying to figure out what the heck was wrong with it.
They sent it to ford dealers, chevy dealers, and local auto repair shops. No one could figure it out. I can't begin to tell you how many houses burned flat from no local fire truck to respond. The firemen drove their own trucks and used the available supplies in place of the truck. But the slow response times from bringing in fire trucks from 15 to 20 miles away left most of the calls as complete losses.

Eventually a FD from another city donated their old truck to the city. But for about 10 years we basically had no fire protection. Your words reminded me of this... as we used to joke about the day when the whole town would burn flat from the old yellow truck. That truck was sold to a local recycler and later recycled after they couldn't make it run either.

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Old 06-21-2017, 04:56 AM   #279 (permalink)
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I'd want to see someone sitting in it with the bubble top closed before I'd pass judgment as a daily driver.
I'm sure headroom would be an issue, unless the cockpit could be set more towards the center of the cabin.


Quote:
More your speed?

Sure. That Variant would be good to use for work at unimproved airfields.
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Old 06-21-2017, 09:50 PM   #280 (permalink)
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I did nothing today regarding me having a VW project car. But its one day closer until I get the checks in the mail, to actually do something!




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