Corvair twin Turbo

[Mr.Squeelerz]

I have been toying with the idea of doing a twin turbo set up on my Corsa 140. Thinking about using the original style delco turbos that came in the Corvairs. They are relatively inexpensive. Not to go crazy with boost but to create usable boost and keep it corvair. Any Ideas?

[TonyL]

It should work, I dont know why I haven't seen more corvairs with twins pushing in to 140 heads. Perhaps heat may be a factor. I plan to vortech supercharge mine eventually. Figuring out intercooling and a plenum seem to be the big challenges.

[Mr.Squeelerz]

If cooling is an issue...has anyone mounted an electric puller type fan? and if so what were the results. Would you still use the Carter YH carb for each turbo or make a custom plenum with direct port/TBI? which would be affordable?

[TonyL]

The use of an electric fan on a corvair is a myth. Everyone who's ever tried it failed miserably. The fan on the corvair is a centrifugal blower fan, electric radial fans do not "push" hard enough. The CFM rating on a fan is either for pushing or pulling air through a radiator. The engine is 1/2 an inch away from the fan. This causes cavitation with ANY electric fan and you get no cooling. So my advice is to get that idea out of your head. the stock fan is great, and works on 400 hp vairs just fine.

There has been many advancements in the area of fuel injection with the corvair through american-pi. It's the hottest thing out there, but the most expensive. Carbs would be the cheapest way to go. There's been several guys who go with webber side drafts.

There's been better success with guys setting up "blow through" carbs on thier cars. (which is the route I'd go, if not fuel injection.) Some of the higest output corvair motors run this setup.

[pdq67]

Oooooh!!

I gotta!!

Remove the barrel fins and can the suckers and water cool her like Subaru made their flat-4's!!

BUT that popped-off said, I flat DON'T know if this can be done or not??

pdq67

[deuce_454]

wouldnt it be easier to put the #match engine on a pallet, and stuff in an LS2 if you really want a watercooled engine??? the weight should be comparable at worst...

with regards to stock turbos... well they are setup for stock airflow.. if you want to add more power and boost, get some that are matched to the boost and airflow toy are running... masterpower turbos are awesome units and are cheap as dirt

[Fuelie Fan]

I'm not sure what physical event you are trying to explain, but cavitation is definitely not the correct word. Cavitation only happens in liquids under low pressures. So, firstly, air is a gas not a liquid. Secondly, pushing would create higher pressure downstream, not lower pressure.

There are some incredibly powerful electric fans on the market now. I've had to use them in a number of projects recently. If you have any data on the existing mechanical fan and/or required i could probably design a system. You may need to upgrade your alternator though ;)


The use of an electric fan on a corvair is a myth. Everyone who's ever tried it failed miserably. The fan on the corvair is a centrifugal blower fan, electric radial fans do not "push" hard enough. The CFM rating on a fan is either for pushing or pulling air through a radiator. The engine is 1/2 an inch away from the fan. This causes cavitation with ANY electric fan and you get no cooling. So my advice is to get that idea out of your head. the stock fan is great, and works on 400 hp vairs just fine.

There has been many advancements in the area of fuel injection with the corvair through american-pi. It's the hottest thing out there, but the most expensive. Carbs would be the cheapest way to go. There's been several guys who go with webber side drafts.

There's been better success with guys setting up "blow through" carbs on thier cars. (which is the route I'd go, if not fuel injection.) Some of the higest output corvair motors run this setup.

[TonyL]

It's been done to death. really.

You're missing my point. There's a difference between the CFM needed and the PSI needed to push air over the corvair engine.

Having an electric fan with a high CFM rating isn't going to be enough, because that rating was designed for as little restriction before or after the fan as possible. The heads and engine are litterally an inch away from the whole fan surface. It's very restrictive. Couple this with the fact that air moving too fast is ALSO bad. it wont hang around long enough for effective heat transfer.


Perhaps cavitation isn't the proper technical term, It's exactly what happens on these cars. The air buffers against the engine and heads and the fan fails to push sufficient air around the motor. The heat spirals out of control, the fan gets hot and fails.

Case in point:
here's an actual twin turbo corvair running the electric fan setup.
Note the better alternator.
https://static1.pt-content.com/images/noimg.gif

This car cannot be driven anywhere. He only autocrosses it. (so I'm told.) otherwise it gets hot.

There's even a kit on the market that was tested over at corvaircenter.com. It was a very serious test because so many of us wnat this system to work. It failed. the car got hot every time, regardless of load.

what we need is a squirrel cage type blower system, one for each cylinder bank blowing down over the heads. Something that creates the PSI needed, Not the CFM. One like a Porsche has or even the DTM type fan the big bore VW guys are running. I favor a dual squirrel fan setup myself, because i think i'd look cool and could be run with a serpentine belt setup.

[Fuelie Fan]

I will repeat that i design systems like these for a living, and I hate to sound rude because you're a respected member on the site and have one of the coolest corvairs I've seen, but despite knowing "what's been done to death" you're not demonstrating any knowledge of the physics here, so please don't try to come off like you're an expert on the subject. I am well aware of how to read fan curves. I know that almost all electric fans are rated at 0 psi drop. That is why i asked for data on the mechanical fan: If i had some indication of it's performance and operating points, then I could better judge the challenge.

To correct another of your points, you need pressure AND flowrate. I am staring right now at three fan curves. The first flows 3500 cfm at 0 pressure drop, the second one only flows 3000. BUT, the "smaller" still flows 1700 at 1inH2O drop, while the other one has deadheaded (zero flow). The third has an even HIGHER max pressure but less flow at wide open AND at the 1" point. This fan would fit your "pressure not cfm" criteria but perform worse than the fan mentioned before it if the required pressure drop is indeed 1". Its the flow rate AT the pressure drop combination. It's like sizing fuel pumps, except the pressure drop number can sometimes be VERY hard to estimate (such as in this case).

Take a step back: If you took the existing mechanical fan and connected a 100hp electic motor to it, can we agree that it would cool your motor (until your battery died)? If so, then we're over the "electric fans won't work" hurdle. From there, it's just a matter of optimization. Just because aftermarket attempts to date have sucked doesn't mean it's impossible.

Being relatively unfamiliar, can you tell me why the fan has to be so close? Is it because of those intake tracts? Maybe packaging would be the downfall, and you wouldn't be able to fit a powerful enough electric motor underneath the intake. I don't know. I just hate the whole "it can't be done" thing, i hate people usings buzz words when they have no idea what they mean, and most of all I hate the propagation of psuedo-science on these boards.

[pdq67]

Fuelie,

Thinking out loud is all??

Can't we use a stock Corvair fan and use a topend rpm hp sized right vari-speed electric motor on it so that the electric motor's computer controlled rheostat, (i.e., electronic speed controller), allow's the motor to behave like it is belt driven??

Or are you telling us that the motor would have to be so big that it become's impractical?

pdq67

[Fuelie Fan]

Yeah i think out loud a lot! Though experiments are very useful for me to flush out a problem.

that's what i was suggesting, if you have an electric motor powerful enough to spin the factory fan at the same average speed as it is currently spun by the engine, then it is technically possible to do an electric fan setup. But, having never tried it, I don't know what the space constraints are.

[TonyL]

Fuelie,

Thinking out loud is all??

Can't we use a stock Corvair fan and use a topend rpm hp sized right vari-speed electric motor on it so that the electric motor's computer controlled rheostat, (i.e., electronic speed controller), allow's the motor to behave like it is belt driven??

Or are you telling us that the motor would have to be so big that it become's impractical?

pdq67

Yes. That too has been done a lot. Can an electric fan work at all? Sure. The point seems to be the problem here. There's simply no point to changing it to an electric one that will work. The amount of HP required to run the fan due to the amperage load on the alternator cancels out the HP gained by switching.

Now. Im not an expert on the whole thing. Far from it. All I know is what I've read on corvair message boards. This topic is the equivalent of "define pro-touring" here. It comes up and deteriorates into a mess quickly, often and regularly on virtually every corvair based board. But overwhelmingly, despite many attempts to prove it can be done, all so far, have ended in failure. Clark's corvair (the industry's biggest supplyer of corvair parts and performance goodies) won't even discuss it anymore.

you want data?
Click here (http://corvaircenter.com/phorum/read.php?1,90723,page=1)


COOLING THE CORVAIR ENGINE
WITH AN ELECTRIC FAN

With the knowledge that the stock Corvair cooling fan consumes some 14
horsepower at 4800 RPM, and even greater power at potential racing speeds,
enthusiasts have long sought a remedy for this considerable reduction in engine
output. If somehow, the stock engine-driven cooling fan could be replaced by an
electric-driven fan similar to those now being used on current production cars,
then the horsepower required for cooling could be reduced. There have
previously been many attempts to accomplish this feat, but none has ever been
entirely successful, although rumors abound with success stories. Despite this,
the concept remains alive with the hope, that maybe there might be some way to
accomplish this cooling feat; something previously overlooked or some new
piece of equipment that might do the job. If this cooling method worked, not
only would considerable engine power be saved, but also any potential fan belt
problems might be side-stepped too. One of the initial problems when trying to
compare the stock cooling setup to an electric fan is the confusion of CFM
ratings. The stock fan is rated somewhere around 1400 CFM at an engine speed
of 4000 RPM, while many electric fans are rated at a much higher CFM. This
leads one into thinking that the electric fan might flow more air. It isn’t so,
but it’s easy to get confused. The problem is that the electric fans just don’
t develop the kind of air pressures required to force the air over the
engine restrictions.
At the 2005 International Corvair Convention in Portland, Oregon,
a company, Vairhouse, of Reno, Nevada was displaying an electric
cooling-fan setup they were manufacturing and selling. They not only had the unit on
display, but they also had a Corvair equipped with their cooling unit that was
being driven around the convention area. Complete engine cooling was being
claimed and the rumor was that the Corvair car had been driven from Reno with
this unit doing the total cooling. If true, it would represent a major
milestone accomplishment.
With this new electric cooling-fan system now for sale and
available, we decided to purchase one and run some of our own, relatively
impartial, tests to see how good this unit might work. As far as we know, this would
be the very first actual independent testing of any similar cooling setup. All
previously tests were, of course, run by the system designer/builder and
actual facts or reports were seldom released.
So it was, that we obtained this new cooling system, designed to
completely replace the stock engine- driven cooling fan on a Corvair. Ken
Hand generously offered to install the system on one of his Corvairs and run the
tests. Frank Parker, a Chevrolet engineer (of Corvair/Northstar fame)
instrumented the test Corvair for data collection and assisted Ken in running the
tests and evaluating the data.

[TonyL]

More information on corvair cooling fans and attempts at electric. (http://autoxer.skiblack.com/fan.html)


The major difference in requirement as far as airflow is concerned is not the total mass airflow, but the pressure required to push that mass of air over the cooling surface in the required amount of time. Water pumpers use a radiator with a pretty low pressure drop at rated airflows, which means that ram air is sufficient above about 30 mph, and an auxiliary cooling fan need only move the air against a slight pressure gradient at speeds below this. Corvair engines are in fact pretty much self-cooling at speeds above 30 if properly ducted (4-inch dryer hose from the headlight buckets works nicely). Unfortunately, there are circumstances in car operation where the car simply doesn't go fast enough long enough to use this "free" cooling. The stock early model air ducting is adequate; the stock late-model is much more optimized, but both are compromises between the need for interior space, clean dry air, lack of noise, and as much pressure differential across the engine as possible from vehicle motion.

At steady state cruise at, say, 45 mph, a Corvair engine in a coupe or sedan is pretty much wasting the power used to turn the fan, provided that the various fins, shrouds, and seals are where they should be and doing as they should do. But who actually spends a majority of their drive cycle at 45 without speeding or slowing? Convertibles have a less optimized plumbing arrangement, and suffer considerably with the top down. Forward controls are actually pretty well plumbed for cooling air, but generate more engine heat because they're pushing a heavier vehicle with more frontal area.

https://static1.pt-content.com/images/pt/2007/12/headTemp-1.jpg

and here's the most technical data on the fan system that I can find.



There have been a number of very informative posts on the technical specs of the Corvair's main cooling fan on Virtual Vairs. I've condensed a couple from Rad Davis and Ray Sedman to give you an idea of what the requirements are:

The Corvair engine design requires approximately 18 cubic feet of air per minute (CFM) per indicated horsepower and a system pressure of 7 inches of water at 4,000 rpm (see SAE 140C "The Chevrolet Corvair"). This works out to 80 hp and 1800 cfm on the '60, which represents a 20% safety factor. Note, that the temperature curve is quite close to the indicated mean effective pressure (IMEP) curve. The peak is about 2,600 rpm. At this rpm, temperature will be 30 degrees F hotter than at maximum speed. If the power output of the engine is increased by shifting the IMEP to a higher speed, the same temperature levels will follow. No change in fan or speed ratio is required to cool the higher output engine, however there is the problem that the fan starts to stall above 4K rpms

[TonyL]

Still more reading. "corvairs and electric fans don't mix" (http://www.mindspring.com/~corvair/RadFAQ/ElectricFans.html)

If you are going to read ANYTHING on the corvair engine electric fan conversion problem read this one. This seems to be the universal "nail in the coffin" argument for most.

I still think there must be a better way.

a belt driven dual squirrel cage setup blowing down over both cylinder banks aught to do it and it should be more efficient.

[Beige]

The term you are looking for is reversion.

All of your info seems to be based on pusher fans. A puller and some tweaked shrouding might work better.

Also, about your point about the alternater amp draw eating the HP freed by removing the engine driven fan.
While the HP used would be the same, give or take. You can control when that HP is being used to charge the battery. Up to a point anyway.

[TonyL]

yep. Im sure there's a more efficient system out there. All it takes is the demand for one to be created. I'm also confident that the stock fan is sufficent for just about every possible output out of this engine. All that needs to change is the drive system. If someone could build a shaft or gear drive rather than a 90 degree pulley system, the problem would go away mostly. Mods to the actual fan itself are all that is needed.

[Fuelie Fan]

I definitely see the challenge now, thanks for the info. I'm gonna take a look and see if I have any fans that would be suitable.

[TonyL]

I definitely see the challenge now, thanks for the info. I'm gonna take a look and see if I have any fans that would be suitable.

Cool! Thanks for forgiving my ignorance. All I know is what I have read. Having someone versed in the design of these types of systems is exactly what we need. Not someone using "shade tree science" trying to figure something out.

[Fuelie Fan]

What is the corvair's stock fan diameter, and is it desirable to match this? Do you have a good link to a picture of stock shrouding?

[TonyL]

Im not sure of the stock fan's diameter, but I know that many people reduce the fan down by 2 inches to lower the rotating mass, and gain power.

There are loads of images on google (http://images.google.com/images?q=corvair+shrouding&ie=UTF-8&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&sa=N&tab=wi)

Click here for a good one. (http://www.bitinfusion.com/09-26-07%20Sandblast%20corvair%20tin%20and%20paint/DSCF0983.jpg)

Thing is, for me, the problem isn't the limitations of the fan itself. But rather that the belt has to bend 90 degrees to turn it. Corvair engines can rev to 7500 to 8000 rpm all day long. but when you let off, the belt flies off.

There's been all kinds of clever attempts to fix this problem. Billet spring loaded tensioners, etc. Some work ok, but the problem has to have a better solution.

[pdq67]

Fuelie,

Thanks for not laughing at me!!

And PLEASE again..................

Can we remove the cast-iron cylinder barrel fins and can the suckers and then individually manifold water cool each cylinder can say bottom in and top out, one at a time to a small belt-driven w/p and rad.!!

That said, I flat DON'T know if this can be done or not??

But, heck, if a guy can pipe a multi-stage NOS system, then this should be a piece a cake, imho........

pdq67

[ScottS]

Hi Guys

Just wanted to chime in on the fan thing. I think I know why the belt gets thrown.

When the fan ( which is pretty heavy) gets spun up to high rpm, and when you let off the gas, The engine responds with some compression braking and the revs drop - but the fan wants to keep spinning- so the belt , which was under tension driving the fan by being PULLED around the pulleys, is suddenly being PUSHED around the pulleys by the momentum of the van.

I think the solution is a simple one way sprag clutch on the fan so when it wants to spin faster than the engine, it can.once it slows down to the engine rpm, or the engine speeds back up to the fan speed, then the engine can drive it again.

This should stop any thrown belts.

Motorcycles have one way clutches so that they don't lock up the back wheels when downshifting, a pretty simple clutch is just two disks, one rotating inside the other with rollers in between on ramps- turn it one way and the rollers jam , and you transfer drive from the inner hub to the outer- drive the outer hub faster than the inner and the rollers just roll. One of these days I am going to build one- it could be built right into the fan pulley.

[Corsa]

Has anyone thought about adapting a blower off of say a 3800 series 2, adapted to the stock tin, pull the throttle body off so it can really suck, fix up a different pulley on the front, and bingo a fan that won't slip belts. plus you could duct the intake for the blower to a scoop on the hood, or under the window to pull cool air in. This would get the psi needed to "push through" the cooling fins, would vary with engine speed, and flow the right cfm, especially with different pulleys and intake size options.

I know where one of these is, at a junk yard here close to the house. I'll buy it when I have money (not sure when that'll be, don't hold your breath) and see what I can come up with.

This same kind of system was used on the "cammer" engine in the astro1 concept motor.

[The Stickman]

Way back when in the mid 90's I ran track events with a Corvair club. I friend of mine thru those events had a convertible twin turbo car. He used Motorcyle turbos and a 390 cfm Holley 4barrle I gave him.