<VV> LM turbos and no lower shrouds
jvhroberts at aol.com
jvhroberts at aol.com
Tue Oct 25 06:30:42 EDT 2011
Also not to get into a war...
Marine engines are overcooled all the time, but look at their cooling source! As such, not particularly applicable to an air cooled engine!! :)
Corvair engines aren't water pumpers, no matter how much SOME people want to spray water all over and into them!! <G>
In my experience, overcooling a Corvair engine is just about impossible. And yes, mine had all the seals in place around the engine, etc.
Design parameters assumes things were designed for the intended application. Given that the 80 through 180 HP Corvairs have essentially the same cooling system, I have little doubt the cooling system was designed based on cost. GM simply figured if they didn't overheat to destruction while cruising, that's fine. They didn't really care beyond that, where obviously I do! ALL Corvairs, if driven hard (and if you have a 140, a turbo, or just like having fun, why wouldn't you?) will run hotter than ideal, often by a lot.
So, yeah, there's room for improvement. A LOT of room for improvement.
John Roberts
-----Original Message-----
From: Eric S. Eberhard <flash at vicsmba.com>
To: Carlton Smith <carlton55 at comcast.net>
Cc: virtualvairs <virtualvairs at corvair.org>
Sent: Mon, Oct 24, 2011 9:01 pm
Subject: Re: <VV> LM turbos and no lower shrouds
Carlton,
You are most welcome. See my response to Mr. Roberts who disagrees
and is knowledgeable and well respected. In this case I think he is
wrong, and more than wrong. What many people consider "stock
cooling" is not stock cooling. You can't have a lot of extra holes
in your firewall. You must have proper seals all around the
engine. The bellows must function properly including proper
adjustment and making sure they are good. And my caveat is "close
to stock car" -- meaning a 300hp 3 liter dual triple Weber monster is
a different can of worms. A built turbo with Weber and and big
pistons and big turbo, another can of worms. When you do a lot of
mods, you start changing everything ... and unless you know how to
engineer that ... for example if you put a Weber on and do nothing
else my guess is you will knock. So you slowly start going down the
road of one mod leads to another. And in the end, perhaps, the stock
cooling fails. My cars are all stock Corvair with the exception of
ignition system (I hate points and setting the dwell, just lazy) and
my coupe also uses the 260 cam (bet money that has no affect on
heat). Oh yeah -- making sure those vanes are clear and the jugs are
not packed with grease ... that is important.
The car was designed to run at those temps, that is correct, and I
would not assume that "cooler is better" and maybe that is why you
get a different answer from me than Mr. Roberts. I am not say it is
not cooler without the shrouds. What I am saying is that a stock
engine will run within design parameters under any driving condition
(speed or outside temp) with a stock cooling system -- no matter how
spirited you are.
If you run cooler and warm-ups take longer, you likely are cause WAY
MORE WEAR than driving it at temp. Have you ever wondered why people
ask when looking at a used car "city miles or highway miles" or why
almost all diesels are left on when drivers go into store, truck
stops, eat dinner, whatever? Answer -- starting a car is like
driving 100 miles. Starting a COLD car is like driving 1000
miles. That is because oil drains off the engine parts and when you
first start it is a little
dry.
And it is so much worse if cold and allowed to run cold, the oil is
NOT circulating well. Which, BTW, is why you need sure to make sure
you use an oil that has enough ZDDP (zinc etc). Like Mobil 1 15-50
(note each mfg most oils do not have enough zinc, but usually they
have something with enough zinc -- not all Mobil 1 has enough). You
can use Clarks zinc additive although I don't trust that as much as
an oil made right to start with. In fact, for long term wear on your
engine your oil choice is crucial. I hope you did not break in that
new engine with dinosaur oil that did not have the zinc ... hard on the cam!
What I am saying is when not driving in a spirited way, just toodling
along, you may be running so cold that the oil is NOT doing it's job,
the oil is thicker, and you may be harming your engine more. It was
designed around the stock cooling system and you cannot be hurt going
that way. However, when you go down modification road ... unless you
are very knowledgeable, one problem can lead to another or you could
have unintended consequences (particularly in this case from running
too cold). You can actually contribute to building up sludge in your
engine. That happens when temps are not high enough and I would
suspect that when you take the shrouds off you could easily be
running oil temp that are WAY too low. You need something like
200-220 oil temps. Oddly I have one car that has cylinder head and
oil temp gauges (my toy) ... when oil temps hit 270-280 cylinder head
temps are 425+ ... this is a good place as this is about max (any
more and the stock temp idiot light goes nuts). Cylinder head temps
are way more volatile than oil temps (e.g. it takes forever to get
oil temps up or down, cylinder temps change almost instantly from
super hot to cool). I would guess that if you are running 300-325 on
the freeway that your oil temps could easily be in the 200-220 range
-- meaning probably TOO COLD. http://www.synlube.com/sludge.htm
(note they recommend synthetic as I do, with zinc!!!!!!).
So my recommend is still, run it stock assuming it runs within stock
parameters, use good oil, and a good ignition system.
I should point that I have heard of stock manifolds cracking from
getting real hot and then zooming through a puddle of cold water. I
suspect it is a minor risk, but real.
So that I don't get in a war with Mr. Roberts whom I usually agree
with -- I agree it runs cooler without shrouds. But it cools
CORRECTLY with the shrouds and maintains the engineered
tempuratures. It is possible to run too cold as well as too
hot. Otherwise there would not be thermostats in water cooled
cars. Engines are designed to operate within a specific temperature
RANGE for optimum efficiency. A properly functioning cooling system
with the correct heat RANGE is absolutely essential for good fuel
economy and performance as well as prevention of sludge buildup in
oil passages and the heads. A thermostat that causes the engine to
run too cold can experience up to a two mpg loss in fuel economy ...
Here is a posting on running too cool an
engine:
http://www.sailnet.com/forums/atomic-4/53480-will-running-cold-cause-engine-damage.html
I believe it is still better in all ways stock, due to exposing the
engine, possible cracks, running colder than you should. I think you
could compare it to removing the thermostat in a conventional
car. It would be slow and hard to warm up, and run too cold at
times. If you know exactly what you are doing and want to fiddle
with it, fine. Otherwise, stock works. It is a matter of do you
trust the original engineers to make a system that is best most of
the time, or do you want to try and do better and take the risk of doing worse?
Eric
At 04:02 AM 10/23/2011, you wrote:
>Hi Eric,
>
>Thanks for your opinion. I am seeking those with experience and you have
>shared yours.
>
>I have owned my particular 1965 turbo Corsa since 2007. The previous owner
>had rebuilt the engine in 2000. It was totally stock with the exception of a
>Clark's 260 cam. On the highway in the Midwest if I went over 65MPH for any
>length of time on a 75-80 degree day the head temp would reach 425-450
>degrees (the gage is accurate as I have a infrared temp gun). The engine
>always had a couple of (loud) clacky valves that were lifter/cam oriented. I
>decided to have the engine rebuilt last winter by a professional Corvair
>mechanic. The engine was totally rebuilt stock, head veins cleared as much
>as possible, correct valve geometry restored, etc. We discovered the bad
>Clarks cam grind on 2 lobes is what was causing the 2 clacky valves and
>replaced it with an Isky cam of the same 260 spec. (I checked with others
>and found they also had problems (on occasion) with this particular Clarks
>cam). Anyway I now have normal quiet engine now. However, with the shrouds
>on I still would go to 425-450 degrees on long distance highway traveling.
>So I decided to try the shrouds off option and it usually travels at 300-325
>degrees and on a hot day might go to 350. I am told by may turbo owners and
>the folks at Clarks that the shrouds on temperatures are absolutely normal
>for a turbo. Also that those temperatures will eventually shorten the life
>of the engine as compared to a standard engine. I drive the car every day in
>the summer and garage it in the winter. I drive it as long as I can every
>year so that does involve fall and spring days in the upper 30s and 40s. I
>can still get heat in the cab from the upper shroud hose so that is ok with
>me. However, I don't like having the bottom of the engine exposed all of the
>time to possible road debris (rocks, etc.). I am a little worried about the
>start up/warm up factor although it seems it warms up fairly quickly. So you
>can see I am already at the point of making a possible mod decision. I am
>interested to know what John Roberts is suggesting.
>
> Thanks for your input Eric!
>
> Regards,
> Carlton Smith
>
>
>
>-----Original Message-----
>From: virtualvairs-bounces at corvair.org
>[mailto:virtualvairs-bounces at corvair.org] On Behalf Of Eric S. Eberhard
>Sent: Sunday, October 23, 2011 2:29 AM
>To: virtualvairs at corvair.org
>Subject: <VV> LM turbos and no lower shrouds
>
>
>
>I am always puzzled by this discussion which comes up every so
>often. The car was designed well from the factory. If you have
>everything correct -- all the shrouds as well as seals and so forth,
>there is no better system. I am in AZ, totally bone-stock, at
>altitude (3500-8000 feet), summer temps of 110 ... and I NEVER have
>even gotten remotely close to overheating. Our speed limit is 75 and
>I can go up a 6% grade at 80, no over heating. From my 3500 to 7500
>feet happens in 6 miles, no overheat even at 80.
>
>I believe that those that overheat and think they need to
>remove/modify shrouds simply have other problem they are compensating
>for. Mine is a 62 EM and perhaps it is different, but I have had to
>EM turbos as well and neither ever had a heating problem.
>And we get 20 degrees in the winter, so having those shrouds on then
>is crucial and I don't need the hassle of swapping them on and off.
>
>One writer pointed out the correct heat is required for quick
>boost. Correct. Some people even wrap their exhaust to push temp
>even higher, for that reason. Some people mistakenly use a "free
>flowing" muffler which actually reduces boost and is bad. I used an
>NOS turbo muffler.
>
>Keep it stock and it will be absolutely reliable (my only mods are
>electronic ignition and related upgrades).
>
>If you have heating problems -- are your plugs too hot? I use Nology
>Silverstone plugs and they perform very well with a 38 gap and hot
>ignition, no overheating. They are made for vintage cars. They are
>expensive, but I have over 30k on them and they are clean as a whistle.
>
>BTW -- opinions are like belly buttons and so I have one. I respect
>others, as other people have done neat things. I am not a good
>enough amateur mechanic to re-engineer things. But I believe a
>properly set up stock system -- not all that hard to achieve -- is
>going to be reliable. Doing the ignition and putting a Judson on one
>of my cars is sort of the limit of my explorations. However, my
>Spyder always has instant boost (no lag), boosts at 2000 rpm in 4th,
>pulls to redline, and I can't overheat it.
>
>So if you are in the mood, you might try making it factory spec
>first, seeing how that goes, and then modify. Otherwise, you might
>mask a problem that later gets ugly.
>
>Eric
>
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Eric S. Eberhard
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