Speedster fan set up

Speedster on ebay has a unique fan set up under the deck lid

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Nice set up!!! Take a look at the pics, the only thing to worry about is moisture when washing vehicle or if you are bold enough to take a cruise in the rain!

Gabe

The same question occurs to me each day of life, but this picture prompts the same universal question......Does it blow,,,,,or suck ?
Which would be most effective ?


Gclarke "The vacaville Guy"

gary, its the thought that counts. as long as "it" works i'm sure "it"
would have positive results.

Bruce.....you make me laugh....It's good to start the day laughing.


Gary

When it comes to sucking and blowing, doesn't it depend which side of the fan you're looking at? Anyways, I assume it blows out of the grill, upwards, si???

I believe the fan should "suck" cool outside air into the engine compartment when the car is moving.
When the car stops and shuts off, the fan could then reverse directions and "blow" - exhausting the hot air out of the engine.
Since it's just a matter of spinning the fan blades one way or the other, it would be easy to do.
Suck and blow...Wow, the best of both worlds.

Suck and blow...reminds me of a Mel Brooks' movie. (the giant vacuum cleaner in space?)

Okay....who has the definitive engineering answer ?


GClarke

The Fan Blade "Pitch" illustrated in the picture indicates the Fan Blade will "Pull" air into the Engine Compartment.

Reversing the Motor's rotation will have very little effect due to the "Pitch" of the Fan Blade.

Suck.....blow is just an expression. What do you think we are? Baloons? Oh your talking about the fan!

All I know is that it sucks when the motor blows!:)

BD

If fan blades are "pitched" to be effective moving air one way, they would be equally effective in moving air the opposite direction if the blades' rotation were reversed.

"You sure about that, Mr. Wizard?"
"Yes, Billy. It's a scientific fact!"

... Unless the blades are "cupped" (in addition to being pitched), in which case they will move some air in the opposite direction when the motor is reversed, but in nowhere near the volume as teh direction of normal rotation. This is what I do to pay for my speedster addiction... Fans 'n stuff.

And the blades in the first pic do look "cupped." I stand (or actually sit) corrected.
Ordinarily, I'm a big fan of fans.

Soooooooooooo, Mr. Wizard, is the conclusion that this fan is sucking outside air, and blowing it onto the motor ? And if that is the case....is that more effective cooling than the other direction??????????



Gclarke "The Vacaville Guy"

If the purpose of the fan is to cool the engine, then yes, the fan is pulling outside air DOWN into the engine.
In other words, just like "The Benefactor" on ABC, it sucks.

Thinkyo, problem solved.

Only if there is somewhere for all that hot air to go . Kind of like blowing into a bottle if there is no vent for air to escape through.

This fan looks suspiciously like those supplied with external oil coolers, which would also lead me to believe that it is drawing air into the engine compartment.

In terms of increased efficiency for sucking versus blowing and similar performance for both; in general this is true (think engine driven fans with conventional untipped blades), but almost always fans in automotive applications are designed to operate in one direction only, and therefore have increased airflow in one direction.

The fan blades are a "forward skew" design (meaning that the tip of the blade is forward of the blade root on the hub) which is a more efficient blade than a "backward skew" blade (which is the opposite). the band around the edge of the fan is there to not only add structure to an otherwise thin blade, but also (when combined with the right fan shroud design) can have a significant effect on performance.

The "cupping" of the blades is in fact a means of reducing the weight of the fan, and has no real effect on the efficiency, but would affect the fan performance were its direction to be reversed.

The only thing I would change is to fill back in all the open space around the outside, because all you're doing otherwise is recirculating air around the fan.

I wonder how it is controlled? Is there a thermostat somewhere? How would you calibrate between cylinder head temperature or oil temp and the ambinet temperature in the underhood environment?

Stan, you mentioned that you "do fans" to support your speedster habit, are these automotive fans? That's what I do to feed my obsession.

Cheers,

Jim.

If the fan were sucking air in to the engine compartment I believe it may help by creating positive air pressure to keep the carbs and the engine driven fan from creating negative pressure an pulling more air from the bottom half of the engine. If the engine were properly sealed from the bottom half and the fan on the alternator engine has fresh air I don't think this fan would help at all. But maybe this car has both of these problems and this helps keep thing cooler. I think I remember this subject coming up before about which would actually be more effective sucking hot air out of engine compartment or pushing cool air in????

Either way the carbs wouldn't be too happy if some sort of liquid was swallowed down their throats.

Jim,

Nothing that exciting. I'm a HVAC and refrigeration guy, mostly supermarkets, all commercial (most residential customers are concerned only with the price, and that's a road I don't want to go down). Lots-'o-fans in my line of work, just none of 'em on a moving vehicle.

Re: the fan in question- it seems to me that the only time it would have any effect at all is when the car is stopped. Any other time the area behind the car would either be under negative or positive pressure dependant on the aerodynamics of the vehicle (which I cannot discuss with any actual knowledge... but I would think negative). Anyhow- I doubt a little 12v fan would have the push (or pull) to overcome the low pressure created by the aerodynamics. It seems to me, the only time it would work is when the car was stopped, when the engine isn't staving for cooling (or carb) air anyhow. A neat idea, but I'd have to see it actually DO something to be impressed.

I'd think that with those tiny aircleaners those carbs are STILL not going to get enough air

The air cleaner filter area is larger.

Air cleaner diameter of 6.5"
Times that by 3.14 x 1" height ..... 20.41
Carb intake of 2.5" ID is much less of an area

Nature abhors a vacuume. Sucked or blown new air is exchanged.

So, where does one tap into in order to activate the fan based on enging temp?

Saw a similar setup at a Corvair convention (Fan Belt Toss, circa 1981). Fella had rigged a series of wings and air foils starting about mid roof and each was designed to duct cool air INTO the rear deck grille. Then he removed the original cooling fan from the engine, effectively increasing the available horsepower to the rear wheels. Finally, he had a very similar electric fan hook up using a thermostat to trigger the motor and cool off the engine when it got to hot. He claimed on the freeway, his wings and such ran the engine cool enough that the fan did'nt even come on. Can't verify any of that claim.

As for sucking or blowing, it is pretty obvious that ole Ferdinand located the grille to let cool air in. Think about the opposite. Assuming you could efectively suck air out of the grile, where is the replacing air going to come from? From the transaxle area? From below the vehicle? All these places are a lot hotter than the ambient air above the rear deck lid. Why would you want to do that? And I agree, it takes like 8 hosepower (I think) to drive the stock VW cooling fan /alternator. That would take one hell of a large electric motor to turn a purely electric fan for engine cooling. So maybe as an auxilary cooling device only?

I have a bit of experiance with cooling fans but not on the speedster. I work in the film production business operating what is called an Insert/Camera Car which is actually a highly modified 94 GMC 1 ton.
I have a GM 502 Crate Motor in it, the largest aluminum radiator available. I cool the motor with the largest twin fan Flex-O-Fan available. The fan operates from an aux. adjustable two speed thermostat.
Depending upon where it's set (the thermostat), the fan will come on at about 2/3 speed and under higher heat conditions comes on full.
Also, it continues to run for :30-:40 seconds when the engine is turned off pulling cool air through the radiator.
The OEM fan arraingment is removed.
Cools the engine fine and much better then the OEM.
There are many different sizes of faans in cluding the small OEM aux fans which may well assist in flooding the engine compartment with cool air especially at idel or in stop and go traffic.
On another note I have a smaller fan mounted on the outside of the radiator in a 57 Morgan +4 running backwards. I simply removed the fan, flipped it and reverse the polarity. Works great. It's also running on an adjustable thermostate like the one on the 95 GMC.
Now, enough of that maby it'll help. I have other Speedster concerns which maby some of you can help me with.....Next post

Next post speedster related. I have a CMC Speedster with a 1776 motor built by Stephens Machineing and I have a couple of issues:
1) There is a clearence problem betwee the top of the fan shroud and the fiberglass above it. It is real bad but torque of the motor does cause it to rub. So looking for an less tall fan shroud or I may have to cut into the glass above to allow a bit of breathing room. Any suggestions?
2) Looking to lose the generator and go to an alternator. Since the alternator case is a bit bigger the the generator case I wondering if there is any clearance problems with the lid or the carb linkage the car has 55mm Dellortos.
I'm Considering the center mount fan shroud (which has smaller shoulders) and the alternator relocating stand arraingment offered my Dan's Performance Parts out in San Diago somewhere.
Any comments or suggestions?
Thanks in advance
Mike

Try the OEM VW fan set up; it works better than anything out there except for appreciatively more expensive units such as the DTM sold by Jake Raby. It's flat at the top (as opposed to the old 36 hp units or the newer aftermarket units modeled after them) so maybe you gain some clearance there but to tell you the truth this is the first time I've heard of such a clearance issue on a Speedster replica. With regards to the alternator and alternator stand you won't have any clearance problems with your carbs (by the way I suppose you meant Dellorto 45's; I haven't heard of 55's yet; I've heard of 52's though). Not to be critical but for a 1776 you're probably over carbed. Good luck on your project.

impala - Sorry! They are perported to be Dellorto 36mm. But, I haven't removed them yet to check. This car is fairly new to me so I'm still in the discovery mode. The other specs I have are:
1776 motor
284 duration 431 lift cam
8 dowel crank and flywheel
SMI 40x35.5mm big valve racing heads
Counter weighted and balanced Crank
36 mm Dellortos
1700 lb. Kennedy Clutch.
At the moment I'm hearing a noise coming through the back left carb when I air hose it by ear. So I'm about to get into the valves and seem if I have a loose rocker arm down there. I'm supposing with the engine rebuild they installed chromoly push rods so I'm researching the proper valve lash. Looks like something between .012 and.014 is safe.
Had a 56 Porsche 1600 normal coupe years ago and I have forgotton everything....If course it was stock, this ones not.

........they installed chromoly push rods so I'm researching the proper valve lash. Looks like something between .012 and.014 is safe.

Chromoly push rods get a zero clearance adjustment that being, just loose enough to be able to rotate/spin the rods between your fingers. .012-.014 and the motor will not run.

As I understand it from my research here, there and everywhere, the zero lash on chromoly push rods might give you a bit more power but you have to, or should re-adjust every 3000 miles or so as the tend to tighted up. Also therte is more possibility of smoking a valve. I decided to loosen mine up to .004 which is tighter then stock which I believe is .006.
Waiting for new gaskets coming tomarrow from NAPA so when it's back together I'll report back.

Moly rods don't expand as others do.

As Alan says chromoly pushrods are adjusted at zero lash and perfectly safe. Aluminum pushrods (stock and aftermarket) expand more than the chromolys; that's why the factory specifies a .006 lash. With respect to the readjustment every 3,000 miles; it's something you have to do anyways when changing your oil and it doesn't take that long; might as well do it while under there. It only takes a couple of new cork valve cover gaskets.

If those are your engine specs you might be undercarbed then unless you swapped your venturis for larger ones due to your big valve heads. By the way Dellortos are great; I just installed a set of 40's in my car.

Hey Ricardo -

I'll bet that you're having fun with your new engine? Is it performing as you hoped it would? Wishing you many trouble-free miles!

Peace - Out!

Thanks Jim!; everything's sort of set up but I haven't got a chance to really drive it; I mean some sort of an extended trip. I still need to do that to really dial it in although it's working (and sounding) a hell of a lot better than it did before the upgrades. I thanked Jjr for supplying me with one of his one of a kind screwdrivers for adjusting dual Dells in Speedsters. Since necessity is the mother of invention he came up with a really short blade screwdriver that he fabbed up and it works perfectly to adjust the mixture screws in such tight quarters.

Well I've adjusted the chromoly's at .004. If it runs like a weak sister I'll go back to the zero lash or perhaps .015. I''ve always run valves a bit loose. If I can hear them their not burning. With hydrolic lifters I adjust them with the engine ideling. Back them off till they clatter, tighten them till they just stop and then 1/4 turn more.
I hate static tuning but Oh well.

do you think that this will work?
http://cgi.ebay.com/ebaymotors/12-INCH-S-BLADE-XTREME-DUTY-ELECTRIC-COOLING-FAN-NEW_W0QQitemZ110055554622QQihZ001QQcategoryZ33600QQrdZ1QQcmdZViewItem

Item number: 110055554622