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Old 08-01-2011, 09:02 PM
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Default Keeping your cool...

Specifically for VW engines of all sizes. I had an opportunity to run to a show this past weekend in the new car, equipped with a bone stock 1600 single port with a single Solex PICT 30/3 carb. The exhaust is custom made, sort of a header type deal, so it's exhaling much more efficiently than it's inhaling. The trip was about 100 miles round; the last half at the end of the day featured air temperatures hovering around 98 degrees, which means the road temperature was probably 115 or more.

The car is equipped with an electric oil temp gauge and pressure gauge. Now, my pressure probably isn't as accurate as I'd like, as it's T'd off in the normal access hole under the distributor, but at least it's something to monitor. The temp gauge has the sender in the sump at the rear - a perfect place to be. The motor has all the tins in place, including the thermostat and flaps. The breast tin under the pulley is not there, however.

As I settled into the trip home, I carefully watched what the numbers did as I went. The a/c was off (and really, when I turned it on, didn't do much other than cool my elbow... but that's another thread), and there were no other accessories running. The engine cover was off, by the way. The temp gauge steadily climbed until it hit 210 degrees and stopped there... perfect! It stayed there for a little while as I drifted with traffic at around 60mph. As I neared my exit and more stop and go, the temps climbed little by little, stopping around 230.... just a smidge too high for my taste.. and for the engine. The gauge may not be accurate, either, but I'm not taking chances. I'm running a 10w30 synthetic, so that was right at the upper limit. For what it's worth, VW engines were designed to run on straight 30 weight oils. Those with doghouse oil coolers (the fan shroud with the bump on the left for the oil cooler) have a little easier time keeping the engine cool than with a standard shroud. All the while the engine was pinging - and there wasn't a place I could pull over to stop for long enough to let it cool down. I just tried to keep the revs low and not lug the engine... a full valve setting will take place this weekend.

Anyhow... this whole thing got me to thinking on how to cool the engine more efficiently. The one major item, of course, that Sterlings (and variants) don't have is an enclosed engine bay that divides the lower half from the upper half, just like in a Beetle. We have some rudimentary fiberglass pieces along the sides and occasionally at the rear of the motor, but nothing along the front. That alone allows for quite a bit of heat to be drawn from the exhaust system up into the fan and back down over the cylinders, regardless of how much air you think you're drawing from those vents on the top of the body. What to do? Well, if you're crafty, some thin aluminum sheet strategically placed to mimic the Beetle tins would help, though obtaining a completely sealed bay is going to be next to impossible. Another option (that I'm going to explore first) is header wrap for the exhaust pipes. If that heat can be kept out, all the better. The third option is a remote cooler, which I fabricated on my first car and worked so well the oil never did get up to temperature anytime of the year (I think the highest it ever got was 190 degrees on a particularly sweltering day), but that has it's own issues in the winter, where you want the oil to get hot - 210 degrees is the butter zone for these engines.

Reading some posts in other forums, there are mixed reviews on how to effectively cool an engine in a kit or dune buggy, since we are at the disadvantage of not only having precious little airflow to the fan (and subsequently back out again), and several suggestions had been put forward. First was to retard your timing by a few degrees. That never occured to me, but it makes sense. That, too, will be implemented shortly. The second is to make sure all the tins are in place, including the tins under and between the cylinders. Third, and this was of some debate, was to fashion a smooth walled intake directly to the fan from a fresh air source outside the vehicle. That is probably the single most difficult thing to fashion and have it function correctly - any air turbulence will disrupt the flow through the fan and rob it of efficiency (essentially, it will cavitate and lose air through the blades).

I know there are several folks running around with no apparent issues, but I wanted to make sure everyone was aware of what may happen. Your best bet for monitoring temps is a combination of the oil temp gauge and a CHT (cylinder head temp) gauge, with the sender mounted under cylinder 3 for those with standard fan shrouds. A Berg temperature stick in the dipstick hole is the most accurate, but only comes with a light that activates on the dashboard at between 220 and 225 degrees.
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Old 08-02-2011, 10:00 PM
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Thanks for that post. It's actually helping me to organize my thoughts for the silver Cimbria.

I drove it around for about an hour last week just to test it out and to see what breaks. Significantly, the afternoon was one of those very hot ones. I kept and eye on the oil temp, but to be honest I wasn't 100% sure what temp to be looking for on the Bug engine as I hadn't researched it beforehand.

I'm going to test it again tomorrow, but I don't think I overheated one bit. I think it hung around 205 for most of the trip, even when idling after running hard, etc.

My car has a remote oil cooler but it's located in what should be a totally useless position, right in front of the top of the doghouse without any air drawn through it.

BUT... The builder plumbed some direct vents from the side vents of the Cimbria back to the front edge of the doghouse intake. At that point, they end. They aren't attached to the doghouse per se; they just end about an inch in front of it. This alone might be VERY significant. If those pipes were sealed to the intake AND were restrictive, you're right that the air might cavitate.

I just recently experienced this first hand in our office. Our dental suction broke. A new unit cost $6000, so I started to explore creative options. The existing pump moved about 240 CFM. So I bought an industrial dust collector at Harbor Freight (for $160) that was rated at about 1600 CFM. I bought a guillotine-style door valve that I rationalized could be opened or closed as needed to obtain the perfect amount of suction. With the door fully open, it was powerful enough to such your entire arm into the unit (through the open door, NOT through the dental suction plumbing like we wanted.) Interestingly, when we closed the door to increase the vacuum through the system, guess what happened?

Nothing. There wasn't one puff of useful suction at the end of that damn hose. Best as I can tell, a big, squirrel cage fan like that can move a high VOLUME of air but couldn't actually create any vacuum through a restrictive system. It's almost like there is too much slop around the fan and it's shroud to build a suction. That big, powerful fan was merely cavitating in its own swirrling little world without pulling in any new air.

So when the VW guys say that a closed, restrictive system might actually be detrimental, I'm gonna tend to believe them after what I saw with that giant industrial sucker.

(Parenthetically, when the original, failing suction pump later fully failed and caught fire, the dust collector was extremely useful in evacuating smoke from the basement. We'll pretend that was intentional.)

So -- back to my car's lack of an overheating problem -- I don't know what's going on there. Perhaps I'm benefiting from the remote oil cooler even though it's in a dumb position. Maybe those ducts (looks like a pair of 2 inch pvc pipes) that are pointed at the doghouse but aren't actually attacked to it are actually doing something. I don't know. But it surprised me a little that it DIDN'T overheat seeing as how the first gen Cimbria was rumored to run hot due to the design of the rear hatch.

I'm going to run it again over the next two days and see if I can get it to overheat. Perhaps it was running hotter than I remember. Hmmmm.

Do you know what a typical safe operating range for cylinder head temperature is for a Bug? I'll keep an eye on that as well. Of course, this is all based on the perhaps flawed assumption that my gauges read accurately.

With your car, do you think a big-honkin' oversized remote oil cooler that was placed optimally would help? (Maybe even one with a thermostatically controlled emergency fan.) You'd incur the expense of the cooler, but overall it might be one of the easier solutions -- or might at least partially contribute to the solution.

It's definitely unnerving when you witness your temp slowing climbing to oblivion with nothing to do but watch. My red car did that (until I realized it wasn't the radiator or the fans but rather was just a shot alternator that couldn't push those fans.) I hate that. You ride along trying to constantly plan were best to break down and/or what temp is the temp you absolutely won't drive beyond. Not good.
"Give me a fulcrum and a lever long enough and I can move the Earth" -- Archimedes
"Hand me that pipe so we can extend this breaker bar three more feet. Don't worry; Craftsman tools have a lifetime warranty." -- Dad
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Old 08-02-2011, 11:16 PM
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I'd like a photo of that setup, Warren! The cooler is sitting basically on top of the fan shroud?? Or is it in front of the fan intake?

I've been rolling around ideas as outlined above for cooling the engine more effectively. Ideally, a complete "tinware" system around the engine would be perfect, but other than that, I'm going to start with the header wrap on the pipes, and I'm going to investigate removing the stock oil cooler (which preheats the #3 cylinder anyway) and putting in a remote somewhere close with an auxiliary fan. I don't want to tax the oil pump too much, but I think if I keep the run reasonable it should be fine.

As for cylinder head temps... general thoughts should be that they will range between 325 and 375 degrees. Obviously, cooler is better. Anything over 375 and you start cooking valves.
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Old 10-27-2011, 11:59 PM
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Any luck with the header wraps? My ride runs way to hot for my likes. I've put a partial shield between the muffler and engine with the (possible futile) hope that by delaying the direct upward movement of radiated heat, the airflow underneath might scavage some of it out.

I'm also running a 250cfm marine blower into the engine compartment and have a smallish remote oil cooler with 2 12v fans blowing out the back. None of it can keep up with the building heat.
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Old 10-28-2011, 12:20 AM
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Well.. with the outside air temps falling I really can't say for sure. The overall engine bay heat is way down since wrapping the headers and installing some reflective heat blanket as makeshift tins, and my last trip out with the car yielded more than acceptable oil temps. On my other car with the v6 and custom headers, I wrapped those as well - and a huge world of difference. Unwrapped, I couldn't service the engine while it was running; wrapped, it's still hot due to the mufflers, but far more bearable than before.

A word of caution with wraps though; if they get wet they will rot the metal very quickly. And use gloves and full length arm protection... the fiberglass strands get everywhere!
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